diff --git a/ChangeLog b/ChangeLog
index fb1e918..e6b4e26 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,56 @@
 = mbed TLS x.x.x branch released xxxx-xx-xx
 
 Bugfix
+   * Fix a bug in the update function for SSL ticket keys which previously
+     invalidated keys of a lifetime of less than a 1s. Fixes #1968.
+
+Changes
+   * Add tests for session resumption in DTLS.
+
+= mbed TLS 2.13.1 branch released 2018-09-06
+
+API Changes
+   * Extend the platform module with an abstraction mbedtls_platform_gmtime_r()
+     whose implementation should behave as a thread-safe version of gmtime().
+     This allows users to configure such an implementation at compile time when
+     the target system cannot be deduced automatically, by setting the option
+     MBEDTLS_PLATFORM_GMTIME_R_ALT. At this stage Mbed TLS is only able to
+     automatically select implementations for Windows and POSIX C libraries.
+
+Bugfix
+   * Fix build failures on platforms where only gmtime() is available but
+     neither gmtime_r() nor gmtime_s() are present. Fixes #1907.
+
+= mbed TLS 2.13.0 branch released 2018-08-31
+
+Security
+   * Fix an issue in the X.509 module which could lead to a buffer overread
+     during certificate extensions parsing. In case of receiving malformed
+     input (extensions length field equal to 0), an illegal read of one byte
+     beyond the input buffer is made. Found and analyzed by Nathan Crandall.
+
+Features
+   * Add support for fragmentation of outgoing DTLS handshake messages. This
+     is controlled by the maximum fragment length as set locally or negotiated
+     with the peer, as well as by a new per-connection MTU option, set using
+     mbedtls_ssl_set_mtu().
+   * Add support for auto-adjustment of MTU to a safe value during the
+     handshake when flights do not get through (RFC 6347, section 4.1.1.1,
+     last paragraph).
+   * Add support for packing multiple records within a single datagram,
+     enabled by default.
+   * Add support for buffering out-of-order handshake messages in DTLS.
+     The maximum amount of RAM used for this can be controlled by the
+     compile-time constant MBEDTLS_SSL_DTLS_MAX_BUFFERING defined
+     in mbedtls/config.h.
+
+API Changes
+   * Add function mbedtls_ssl_set_datagram_packing() to configure
+     the use of datagram packing (enabled by default).
+
+Bugfix
+   * Fix a potential memory leak in mbedtls_ssl_setup() function. An allocation
+     failure in the function could lead to other buffers being leaked.
    * Fixes an issue with MBEDTLS_CHACHAPOLY_C which would not compile if
      MBEDTLS_ARC4_C and MBEDTLS_CIPHER_NULL_CIPHER weren't also defined. #1890
    * Fix a memory leak in ecp_mul_comb() if ecp_precompute_comb() fails.
@@ -10,11 +60,23 @@
    * Add ecc extensions only if an ecc based ciphersuite is used.
      This improves compliance to RFC 4492, and as a result, solves
      interoperability issues with BouncyCastle. Raised by milenamil in #1157.
-   * Replace printf with mbedtls_printf in aria. Found by TrinityTonic in #1908.
+   * Replace printf with mbedtls_printf in the ARIA module. Found by
+     TrinityTonic in #1908.
    * Fix potential use-after-free in mbedtls_ssl_get_max_frag_len()
      and mbedtls_ssl_get_record_expansion() after a session reset. Fixes #1941.
-   * Fix a bug in the update function for SSL ticket keys which previously
-     invalidated keys of a lifetime of less than a 1s. Fixes #1968.
+   * Fix a bug that caused SSL/TLS clients to incorrectly abort the handshake
+     with TLS versions 1.1 and earlier when the server requested authentication
+     without providing a list of CAs. This was due to an overly strict bounds
+     check in parsing the CertificateRequest message,
+     introduced in Mbed TLS 2.12.0. Fixes #1954.
+   * Fix a miscalculation of the maximum record expansion in
+     mbedtls_ssl_get_record_expansion() in case of ChachaPoly ciphersuites,
+     or CBC ciphersuites in (D)TLS versions 1.1 or higher. Fixes #1913, #1914.
+   * Fix undefined shifts with negative values in certificates parsing
+     (found by Catena cyber using oss-fuzz)
+   * Fix memory leak and free without initialization in pk_encrypt
+     and pk_decrypt example programs. Reported by Brace Stout. Fixes #1128.
+   * Remove redundant else statement. Raised by irwir. Fixes #1776.
 
 Changes
    * Copy headers preserving timestamps when doing a "make install".
@@ -23,7 +85,10 @@
      Drozd. Fixes #1215 raised by randombit.
    * Improve compatibility with some alternative CCM implementations by using
      CCM test vectors from RAM.
-   * Add tests for session resumption in DTLS.
+   * Add support for buffering of out-of-order handshake messages.
+   * Add warnings to the documentation of the HKDF module to reduce the risk
+     of misusing the mbedtls_hkdf_extract() and mbedtls_hkdf_expand()
+     functions. Fixes #1775. Reported by Brian J. Murray.
 
 = mbed TLS 2.12.0 branch released 2018-07-25
 
diff --git a/doxygen/input/doc_mainpage.h b/doxygen/input/doc_mainpage.h
index f695dd2..b9f9ec1 100644
--- a/doxygen/input/doc_mainpage.h
+++ b/doxygen/input/doc_mainpage.h
@@ -24,7 +24,7 @@
  */
 
 /**
- * @mainpage mbed TLS v2.12.0 source code documentation
+ * @mainpage mbed TLS v2.13.1 source code documentation
  *
  * This documentation describes the internal structure of mbed TLS.  It was
  * automatically generated from specially formatted comment blocks in
diff --git a/doxygen/mbedtls.doxyfile b/doxygen/mbedtls.doxyfile
index 317eb0d..2a87ada 100644
--- a/doxygen/mbedtls.doxyfile
+++ b/doxygen/mbedtls.doxyfile
@@ -28,7 +28,7 @@
 # identify the project. Note that if you do not use Doxywizard you need
 # to put quotes around the project name if it contains spaces.
 
-PROJECT_NAME           = "mbed TLS v2.12.0"
+PROJECT_NAME           = "mbed TLS v2.13.1"
 
 # The PROJECT_NUMBER tag can be used to enter a project or revision number.
 # This could be handy for archiving the generated documentation or
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 70820be..81438c5 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -137,12 +137,21 @@
 /**
  * \def MBEDTLS_HAVE_TIME_DATE
  *
- * System has time.h and time(), gmtime() and the clock is correct.
+ * System has time.h, time(), and an implementation for
+ * mbedtls_platform_gmtime_r() (see below).
  * The time needs to be correct (not necesarily very accurate, but at least
  * the date should be correct). This is used to verify the validity period of
  * X.509 certificates.
  *
  * Comment if your system does not have a correct clock.
+ *
+ * \note mbedtls_platform_gmtime_r() is an abstraction in platform_util.h that
+ * behaves similarly to the gmtime_r() function from the C standard. Refer to
+ * the documentation for mbedtls_platform_gmtime_r() for more information.
+ *
+ * \note It is possible to configure an implementation for
+ * mbedtls_platform_gmtime_r() at compile-time by using the macro
+ * MBEDTLS_PLATFORM_GMTIME_R_ALT.
  */
 #define MBEDTLS_HAVE_TIME_DATE
 
@@ -3010,6 +3019,23 @@
  */
 //#define MBEDTLS_SSL_OUT_CONTENT_LEN             16384
 
+/** \def MBEDTLS_SSL_DTLS_MAX_BUFFERING
+ *
+ * Maximum number of heap-allocated bytes for the purpose of
+ * DTLS handshake message reassembly and future message buffering.
+ *
+ * This should be at least 9/8 * MBEDTLSSL_IN_CONTENT_LEN
+ * to account for a reassembled handshake message of maximum size,
+ * together with its reassembly bitmap.
+ *
+ * A value of 2 * MBEDTLS_SSL_IN_CONTENT_LEN (32768 by default)
+ * should be sufficient for all practical situations as it allows
+ * to reassembly a large handshake message (such as a certificate)
+ * while buffering multiple smaller handshake messages.
+ *
+ */
+//#define MBEDTLS_SSL_DTLS_MAX_BUFFERING             32768
+
 //#define MBEDTLS_SSL_DEFAULT_TICKET_LIFETIME     86400 /**< Lifetime of session tickets (if enabled) */
 //#define MBEDTLS_PSK_MAX_LEN               32 /**< Max size of TLS pre-shared keys, in bytes (default 256 bits) */
 //#define MBEDTLS_SSL_COOKIE_TIMEOUT        60 /**< Default expiration delay of DTLS cookies, in seconds if HAVE_TIME, or in number of cookies issued */
@@ -3083,6 +3109,25 @@
  */
 //#define MBEDTLS_PLATFORM_ZEROIZE_ALT
 
+/**
+ * Uncomment the macro to let Mbed TLS use your alternate implementation of
+ * mbedtls_platform_gmtime_r(). This replaces the default implementation in
+ * platform_util.c.
+ *
+ * gmtime() is not a thread-safe function as defined in the C standard. The
+ * library will try to use safer implementations of this function, such as
+ * gmtime_r() when available. However, if Mbed TLS cannot identify the target
+ * system, the implementation of mbedtls_platform_gmtime_r() will default to
+ * using the standard gmtime(). In this case, calls from the library to
+ * gmtime() will be guarded by the global mutex mbedtls_threading_gmtime_mutex
+ * if MBEDTLS_THREADING_C is enabled. We recommend that calls from outside the
+ * library are also guarded with this mutex to avoid race conditions. However,
+ * if the macro MBEDTLS_PLATFORM_GMTIME_R_ALT is defined, Mbed TLS will
+ * unconditionally use the implementation for mbedtls_platform_gmtime_r()
+ * supplied at compile time.
+ */
+//#define MBEDTLS_PLATFORM_GMTIME_R_ALT
+
 /* \} name SECTION: Customisation configuration options */
 
 /* Target and application specific configurations */
diff --git a/include/mbedtls/hkdf.h b/include/mbedtls/hkdf.h
index 6833e72..e6ed7cd 100644
--- a/include/mbedtls/hkdf.h
+++ b/include/mbedtls/hkdf.h
@@ -73,6 +73,11 @@
  *  \brief  Take the input keying material \p ikm and extract from it a
  *          fixed-length pseudorandom key \p prk.
  *
+ *  \warning    This function should only be used if the security of it has been
+ *              studied and established in that particular context (eg. TLS 1.3
+ *              key schedule). For standard HKDF security guarantees use
+ *              \c mbedtls_hkdf instead.
+ *
  *  \param       md        A hash function; md.size denotes the length of the
  *                         hash function output in bytes.
  *  \param       salt      An optional salt value (a non-secret random value);
@@ -97,10 +102,15 @@
  *  \brief  Expand the supplied \p prk into several additional pseudorandom
  *          keys, which is the output of the HKDF.
  *
+ *  \warning    This function should only be used if the security of it has been
+ *              studied and established in that particular context (eg. TLS 1.3
+ *              key schedule). For standard HKDF security guarantees use
+ *              \c mbedtls_hkdf instead.
+ *
  *  \param  md        A hash function; md.size denotes the length of the hash
  *                    function output in bytes.
- *  \param  prk       A pseudorandom key of at least md.size bytes. \p prk is usually,
- *                    the output from the HKDF extract step.
+ *  \param  prk       A pseudorandom key of at least md.size bytes. \p prk is
+ *                    usually the output from the HKDF extract step.
  *  \param  prk_len   The length in bytes of \p prk.
  *  \param  info      An optional context and application specific information
  *                    string. This can be a zero-length string.
diff --git a/include/mbedtls/platform_util.h b/include/mbedtls/platform_util.h
index 84f0732..164a1a0 100644
--- a/include/mbedtls/platform_util.h
+++ b/include/mbedtls/platform_util.h
@@ -25,7 +25,17 @@
 #ifndef MBEDTLS_PLATFORM_UTIL_H
 #define MBEDTLS_PLATFORM_UTIL_H
 
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
 #include <stddef.h>
+#if defined(MBEDTLS_HAVE_TIME_DATE)
+#include "mbedtls/platform_time.h"
+#include <time.h>
+#endif /* MBEDTLS_HAVE_TIME_DATE */
 
 #ifdef __cplusplus
 extern "C" {
@@ -55,6 +65,37 @@
  */
 void mbedtls_platform_zeroize( void *buf, size_t len );
 
+#if defined(MBEDTLS_HAVE_TIME_DATE)
+/**
+ * \brief      Platform-specific implementation of gmtime_r()
+ *
+ *             The function is a thread-safe abstraction that behaves
+ *             similarly to the gmtime_r() function from Unix/POSIX.
+ *
+ *             Mbed TLS will try to identify the underlying platform and
+ *             make use of an appropriate underlying implementation (e.g.
+ *             gmtime_r() for POSIX and gmtime_s() for Windows). If this is
+ *             not possible, then gmtime() will be used. In this case, calls
+ *             from the library to gmtime() will be guarded by the mutex
+ *             mbedtls_threading_gmtime_mutex if MBEDTLS_THREADING_C is
+ *             enabled. It is recommended that calls from outside the library
+ *             are also guarded by this mutex.
+ *
+ *             If MBEDTLS_PLATFORM_GMTIME_R_ALT is defined, then Mbed TLS will
+ *             unconditionally use the alternative implementation for
+ *             mbedtls_platform_gmtime_r() supplied by the user at compile time.
+ *
+ * \param tt     Pointer to an object containing time (in seconds) since the
+ *               epoch to be converted
+ * \param tm_buf Pointer to an object where the results will be stored
+ *
+ * \return      Pointer to an object of type struct tm on success, otherwise
+ *              NULL
+ */
+struct tm *mbedtls_platform_gmtime_r( const mbedtls_time_t *tt,
+                                      struct tm *tm_buf );
+#endif /* MBEDTLS_HAVE_TIME_DATE */
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 2d511a8..83849a5 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -121,6 +121,7 @@
 #define MBEDTLS_ERR_SSL_INVALID_VERIFY_HASH               -0x6600  /**< Couldn't set the hash for verifying CertificateVerify */
 #define MBEDTLS_ERR_SSL_CONTINUE_PROCESSING               -0x6580  /**< Internal-only message signaling that further message-processing should be done */
 #define MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS                 -0x6500  /**< The asynchronous operation is not completed yet. */
+#define MBEDTLS_ERR_SSL_EARLY_MESSAGE                     -0x6480  /**< Internal-only message signaling that a message arrived early. */
 
 /*
  * Various constants
@@ -242,6 +243,14 @@
 #define MBEDTLS_SSL_OUT_CONTENT_LEN MBEDTLS_SSL_MAX_CONTENT_LEN
 #endif
 
+/*
+ * Maximum number of heap-allocated bytes for the purpose of
+ * DTLS handshake message reassembly and future message buffering.
+ */
+#if !defined(MBEDTLS_SSL_DTLS_MAX_BUFFERING)
+#define MBEDTLS_SSL_DTLS_MAX_BUFFERING 32768
+#endif
+
 /* \} name SECTION: Module settings */
 
 /*
@@ -1022,14 +1031,14 @@
     int renego_records_seen;    /*!< Records since renego request, or with DTLS,
                                   number of retransmissions of request if
                                   renego_max_records is < 0           */
-#endif
+#endif /* MBEDTLS_SSL_RENEGOTIATION */
 
     int major_ver;              /*!< equal to  MBEDTLS_SSL_MAJOR_VERSION_3    */
     int minor_ver;              /*!< either 0 (SSL3) or 1 (TLS1.0)    */
 
 #if defined(MBEDTLS_SSL_DTLS_BADMAC_LIMIT)
     unsigned badmac_seen;       /*!< records with a bad MAC received    */
-#endif
+#endif /* MBEDTLS_SSL_DTLS_BADMAC_LIMIT */
 
     mbedtls_ssl_send_t *f_send; /*!< Callback for network send */
     mbedtls_ssl_recv_t *f_recv; /*!< Callback for network receive */
@@ -1085,11 +1094,11 @@
     uint16_t in_epoch;          /*!< DTLS epoch for incoming records  */
     size_t next_record_offset;  /*!< offset of the next record in datagram
                                      (equal to in_left if none)       */
-#endif
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
 #if defined(MBEDTLS_SSL_DTLS_ANTI_REPLAY)
     uint64_t in_window_top;     /*!< last validated record seq_num    */
     uint64_t in_window;         /*!< bitmask for replay detection     */
-#endif
+#endif /* MBEDTLS_SSL_DTLS_ANTI_REPLAY */
 
     size_t in_hslen;            /*!< current handshake message length,
                                      including the handshake header   */
@@ -1098,6 +1107,11 @@
     int keep_current_message;   /*!< drop or reuse current message
                                      on next call to record layer? */
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    uint8_t disable_datagram_packing;  /*!< Disable packing multiple records
+                                        *   within a single datagram.  */
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
     /*
      * Record layer (outgoing data)
      */
@@ -1112,12 +1126,18 @@
     size_t out_msglen;          /*!< record header: message length    */
     size_t out_left;            /*!< amount of data not yet written   */
 
+    unsigned char cur_out_ctr[8]; /*!<  Outgoing record sequence  number. */
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    uint16_t mtu;               /*!< path mtu, used to fragment outgoing messages */
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
 #if defined(MBEDTLS_ZLIB_SUPPORT)
     unsigned char *compress_buf;        /*!<  zlib data buffer        */
-#endif
+#endif /* MBEDTLS_ZLIB_SUPPORT */
 #if defined(MBEDTLS_SSL_CBC_RECORD_SPLITTING)
     signed char split_done;     /*!< current record already splitted? */
-#endif
+#endif /* MBEDTLS_SSL_CBC_RECORD_SPLITTING */
 
     /*
      * PKI layer
@@ -1130,11 +1150,11 @@
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
     char *hostname;             /*!< expected peer CN for verification
                                      (and SNI if available)                 */
-#endif
+#endif /* MBEDTLS_X509_CRT_PARSE_C */
 
 #if defined(MBEDTLS_SSL_ALPN)
     const char *alpn_chosen;    /*!<  negotiated protocol                   */
-#endif
+#endif /* MBEDTLS_SSL_ALPN */
 
     /*
      * Information for DTLS hello verify
@@ -1142,7 +1162,7 @@
 #if defined(MBEDTLS_SSL_DTLS_HELLO_VERIFY) && defined(MBEDTLS_SSL_SRV_C)
     unsigned char  *cli_id;         /*!<  transport-level ID of the client  */
     size_t          cli_id_len;     /*!<  length of cli_id                  */
-#endif
+#endif /* MBEDTLS_SSL_DTLS_HELLO_VERIFY && MBEDTLS_SSL_SRV_C */
 
     /*
      * Secure renegotiation
@@ -1154,7 +1174,7 @@
     size_t verify_data_len;             /*!<  length of verify data stored   */
     char own_verify_data[MBEDTLS_SSL_VERIFY_DATA_MAX_LEN]; /*!<  previous handshake verify data */
     char peer_verify_data[MBEDTLS_SSL_VERIFY_DATA_MAX_LEN]; /*!<  previous handshake verify data */
-#endif
+#endif /* MBEDTLS_SSL_RENEGOTIATION */
 };
 
 #if defined(MBEDTLS_SSL_HW_RECORD_ACCEL)
@@ -1374,6 +1394,52 @@
                           mbedtls_ssl_recv_t *f_recv,
                           mbedtls_ssl_recv_timeout_t *f_recv_timeout );
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+/**
+ * \brief          Set the Maximum Tranport Unit (MTU).
+ *                 Special value: 0 means unset (no limit).
+ *                 This represents the maximum size of a datagram payload
+ *                 handled by the transport layer (usually UDP) as determined
+ *                 by the network link and stack. In practice, this controls
+ *                 the maximum size datagram the DTLS layer will pass to the
+ *                 \c f_send() callback set using \c mbedtls_ssl_set_bio().
+ *
+ * \note           The limit on datagram size is converted to a limit on
+ *                 record payload by subtracting the current overhead of
+ *                 encapsulation and encryption/authentication if any.
+ *
+ * \note           This can be called at any point during the connection, for
+ *                 example when a Path Maximum Transfer Unit (PMTU)
+ *                 estimate becomes available from other sources,
+ *                 such as lower (or higher) protocol layers.
+ *
+ * \note           This setting only controls the size of the packets we send,
+ *                 and does not restrict the size of the datagrams we're
+ *                 willing to receive. Client-side, you can request the
+ *                 server to use smaller records with \c
+ *                 mbedtls_ssl_conf_max_frag_len().
+ *
+ * \note           If both a MTU and a maximum fragment length have been
+ *                 configured (or negotiated with the peer), the resulting
+ *                 lower limit on record payload (see first note) is used.
+ *
+ * \note           This can only be used to decrease the maximum size
+ *                 of datagrams (hence records, see first note) sent. It
+ *                 cannot be used to increase the maximum size of records over
+ *                 the limit set by #MBEDTLS_SSL_OUT_CONTENT_LEN.
+ *
+ * \note           Values lower than the current record layer expansion will
+ *                 result in an error when trying to send data.
+ *
+ * \note           Using record compression together with a non-zero MTU value
+ *                 will result in an error when trying to send data.
+ *
+ * \param ssl      SSL context
+ * \param mtu      Value of the path MTU in bytes
+ */
+void mbedtls_ssl_set_mtu( mbedtls_ssl_context *ssl, uint16_t mtu );
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
 /**
  * \brief          Set the timeout period for mbedtls_ssl_read()
  *                 (Default: no timeout.)
@@ -1757,6 +1823,38 @@
 #endif /* MBEDTLS_SSL_DTLS_BADMAC_LIMIT */
 
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
+
+/**
+ * \brief          Allow or disallow packing of multiple handshake records
+ *                 within a single datagram.
+ *
+ * \param ssl           The SSL context to configure.
+ * \param allow_packing This determines whether datagram packing may
+ *                      be used or not. A value of \c 0 means that every
+ *                      record will be sent in a separate datagram; a
+ *                      value of \c 1 means that, if space permits,
+ *                      multiple handshake messages (including CCS) belonging to
+ *                      a single flight may be packed within a single datagram.
+ *
+ * \note           This is enabled by default and should only be disabled
+ *                 for test purposes, or if datagram packing causes
+ *                 interoperability issues with peers that don't support it.
+ *
+ * \note           Allowing datagram packing reduces the network load since
+ *                 there's less overhead if multiple messages share the same
+ *                 datagram. Also, it increases the handshake efficiency
+ *                 since messages belonging to a single datagram will not
+ *                 be reordered in transit, and so future message buffering
+ *                 or flight retransmission (if no buffering is used) as
+ *                 means to deal with reordering are needed less frequently.
+ *
+ * \note           Application records are not affected by this option and
+ *                 are currently always sent in separate datagrams.
+ *
+ */
+void mbedtls_ssl_set_datagram_packing( mbedtls_ssl_context *ssl,
+                                       unsigned allow_packing );
+
 /**
  * \brief          Set retransmit timeout values for the DTLS handshake.
  *                 (DTLS only, no effect on TLS.)
@@ -2433,6 +2531,18 @@
  *                 (Client: set maximum fragment length to emit *and*
  *                 negotiate with the server during handshake)
  *
+ * \note           With TLS, this currently only affects ApplicationData (sent
+ *                 with \c mbedtls_ssl_read()), not handshake messages.
+ *                 With DTLS, this affects both ApplicationData and handshake.
+ *
+ * \note           This sets the maximum length for a record's payload,
+ *                 excluding record overhead that will be added to it, see
+ *                 \c mbedtls_ssl_get_record_expansion().
+ *
+ * \note           For DTLS, it is also possible to set a limit for the total
+ *                 size of daragrams passed to the transport layer, including
+ *                 record overhead, see \c mbedtls_ssl_set_mtu().
+ *
  * \param conf     SSL configuration
  * \param mfl_code Code for maximum fragment length (allowed values:
  *                 MBEDTLS_SSL_MAX_FRAG_LEN_512,  MBEDTLS_SSL_MAX_FRAG_LEN_1024,
@@ -2695,6 +2805,9 @@
  * \brief          Return the (maximum) number of bytes added by the record
  *                 layer: header + encryption/MAC overhead (inc. padding)
  *
+ * \note           This function is not available (always returns an error)
+ *                 when record compression is enabled.
+ *
  * \param ssl      SSL context
  *
  * \return         Current maximum record expansion in bytes, or
@@ -2709,12 +2822,8 @@
  *                 This is the value negotiated with peer if any,
  *                 or the locally configured value.
  *
- * \note           With DTLS, \c mbedtls_ssl_write() will return an error if
- *                 called with a larger length value.
- *                 With TLS, \c mbedtls_ssl_write() will fragment the input if
- *                 necessary and return the number of bytes written; it is up
- *                 to the caller to call \c mbedtls_ssl_write() again in
- *                 order to send the remaining bytes if any.
+ * \sa             mbedtls_ssl_conf_max_frag_len()
+ * \sa             mbedtls_ssl_get_max_record_payload()
  *
  * \param ssl      SSL context
  *
@@ -2723,6 +2832,34 @@
 size_t mbedtls_ssl_get_max_frag_len( const mbedtls_ssl_context *ssl );
 #endif /* MBEDTLS_SSL_MAX_FRAGMENT_LENGTH */
 
+/**
+ * \brief          Return the current maximum outgoing record payload in bytes.
+ *                 This takes into account the config.h setting \c
+ *                 MBEDTLS_SSL_OUT_CONTENT_LEN, the configured and negotiated
+ *                 max fragment length extension if used, and for DTLS the
+ *                 path MTU as configured and current record expansion.
+ *
+ * \note           With DTLS, \c mbedtls_ssl_write() will return an error if
+ *                 called with a larger length value.
+ *                 With TLS, \c mbedtls_ssl_write() will fragment the input if
+ *                 necessary and return the number of bytes written; it is up
+ *                 to the caller to call \c mbedtls_ssl_write() again in
+ *                 order to send the remaining bytes if any.
+ *
+ * \note           This function is not available (always returns an error)
+ *                 when record compression is enabled.
+ *
+ * \sa             mbedtls_ssl_set_mtu()
+ * \sa             mbedtls_ssl_get_max_frag_len()
+ * \sa             mbedtls_ssl_get_record_expansion()
+ *
+ * \param ssl      SSL context
+ *
+ * \return         Current maximum payload for an outgoing record,
+ *                 or a negative error code.
+ */
+int mbedtls_ssl_get_max_out_record_payload( const mbedtls_ssl_context *ssl );
+
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
 /**
  * \brief          Return the peer certificate from the current connection
diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index d214703..4b4417a 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -155,6 +155,9 @@
 #define MBEDTLS_SSL_OUT_PAYLOAD_LEN ( MBEDTLS_SSL_PAYLOAD_OVERHEAD + \
                                       ( MBEDTLS_SSL_OUT_CONTENT_LEN ) )
 
+/* The maximum number of buffered handshake messages. */
+#define MBEDTLS_SSL_MAX_BUFFERED_HS 4
+
 /* Maximum length we can advertise as our max content length for
    RFC 6066 max_fragment_length extension negotiation purposes
    (the lesser of both sizes, if they are unequal.)
@@ -294,18 +297,45 @@
     unsigned char verify_cookie_len;    /*!<  Cli: cookie length
                                               Srv: flag for sending a cookie */
 
-    unsigned char *hs_msg;              /*!<  Reassembled handshake message  */
-
     uint32_t retransmit_timeout;        /*!<  Current value of timeout       */
     unsigned char retransmit_state;     /*!<  Retransmission state           */
-    mbedtls_ssl_flight_item *flight;            /*!<  Current outgoing flight        */
-    mbedtls_ssl_flight_item *cur_msg;           /*!<  Current message in flight      */
+    mbedtls_ssl_flight_item *flight;    /*!<  Current outgoing flight        */
+    mbedtls_ssl_flight_item *cur_msg;   /*!<  Current message in flight      */
+    unsigned char *cur_msg_p;           /*!<  Position in current message    */
     unsigned int in_flight_start_seq;   /*!<  Minimum message sequence in the
                                               flight being received          */
     mbedtls_ssl_transform *alt_transform_out;   /*!<  Alternative transform for
                                               resending messages             */
     unsigned char alt_out_ctr[8];       /*!<  Alternative record epoch/counter
                                               for resending messages         */
+
+    struct
+    {
+        size_t total_bytes_buffered; /*!< Cumulative size of heap allocated
+                                      *   buffers used for message buffering. */
+
+        uint8_t seen_ccs;               /*!< Indicates if a CCS message has
+                                         *   been seen in the current flight. */
+
+        struct mbedtls_ssl_hs_buffer
+        {
+            unsigned is_valid      : 1;
+            unsigned is_fragmented : 1;
+            unsigned is_complete   : 1;
+            unsigned char *data;
+            size_t data_len;
+        } hs[MBEDTLS_SSL_MAX_BUFFERED_HS];
+
+        struct
+        {
+            unsigned char *data;
+            size_t len;
+            unsigned epoch;
+        } future_record;
+
+    } buffering;
+
+    uint16_t mtu;                       /*!<  Handshake mtu, used to fragment outgoing messages */
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
     /*
@@ -364,6 +394,8 @@
 #endif /* MBEDTLS_SSL_ASYNC_PRIVATE */
 };
 
+typedef struct mbedtls_ssl_hs_buffer mbedtls_ssl_hs_buffer;
+
 /*
  * This structure contains a full set of runtime transform parameters
  * either in negotiation or active.
@@ -478,7 +510,6 @@
 void mbedtls_ssl_reset_checksum( mbedtls_ssl_context *ssl );
 int mbedtls_ssl_derive_keys( mbedtls_ssl_context *ssl );
 
-int mbedtls_ssl_read_record_layer( mbedtls_ssl_context *ssl );
 int mbedtls_ssl_handle_message_type( mbedtls_ssl_context *ssl );
 int mbedtls_ssl_prepare_handshake_record( mbedtls_ssl_context *ssl );
 void mbedtls_ssl_update_handshake_status( mbedtls_ssl_context *ssl );
@@ -490,7 +521,10 @@
  *              of the logic of (D)TLS from the implementation
  *              of the secure transport.
  *
- * \param  ssl  SSL context to use
+ * \param  ssl              The SSL context to use.
+ * \param  update_hs_digest This indicates if the handshake digest
+ *                          should be automatically updated in case
+ *                          a handshake message is found.
  *
  * \return      0 or non-zero error code.
  *
@@ -556,10 +590,12 @@
  *              following the above definition.
  *
  */
-int mbedtls_ssl_read_record( mbedtls_ssl_context *ssl );
+int mbedtls_ssl_read_record( mbedtls_ssl_context *ssl,
+                             unsigned update_hs_digest );
 int mbedtls_ssl_fetch_input( mbedtls_ssl_context *ssl, size_t nb_want );
 
-int mbedtls_ssl_write_record( mbedtls_ssl_context *ssl );
+int mbedtls_ssl_write_handshake_msg( mbedtls_ssl_context *ssl );
+int mbedtls_ssl_write_record( mbedtls_ssl_context *ssl, uint8_t force_flush );
 int mbedtls_ssl_flush_output( mbedtls_ssl_context *ssl );
 
 int mbedtls_ssl_parse_certificate( mbedtls_ssl_context *ssl );
@@ -668,6 +704,7 @@
 void mbedtls_ssl_send_flight_completed( mbedtls_ssl_context *ssl );
 void mbedtls_ssl_recv_flight_completed( mbedtls_ssl_context *ssl );
 int mbedtls_ssl_resend( mbedtls_ssl_context *ssl );
+int mbedtls_ssl_flight_transmit( mbedtls_ssl_context *ssl );
 #endif
 
 /* Visible for testing purposes only */
diff --git a/include/mbedtls/threading.h b/include/mbedtls/threading.h
index 5112ebb..75298bf 100644
--- a/include/mbedtls/threading.h
+++ b/include/mbedtls/threading.h
@@ -99,6 +99,17 @@
 #if defined(MBEDTLS_FS_IO)
 extern mbedtls_threading_mutex_t mbedtls_threading_readdir_mutex;
 #endif
+
+#if defined(MBEDTLS_HAVE_TIME_DATE) && !defined(MBEDTLS_PLATFORM_GMTIME_R_ALT)
+/* This mutex may or may not be used in the default definition of
+ * mbedtls_platform_gmtime_r(), but in order to determine that,
+ * we need to check POSIX features, hence modify _POSIX_C_SOURCE.
+ * With the current approach, this declaration is orphaned, lacking
+ * an accompanying definition, in case mbedtls_platform_gmtime_r()
+ * doesn't need it, but that's not a problem. */
+extern mbedtls_threading_mutex_t mbedtls_threading_gmtime_mutex;
+#endif /* MBEDTLS_HAVE_TIME_DATE && !MBEDTLS_PLATFORM_GMTIME_R_ALT */
+
 #endif /* MBEDTLS_THREADING_C */
 
 #ifdef __cplusplus
diff --git a/include/mbedtls/version.h b/include/mbedtls/version.h
index eaf25d9..326b8bd 100644
--- a/include/mbedtls/version.h
+++ b/include/mbedtls/version.h
@@ -39,17 +39,17 @@
  * Major, Minor, Patchlevel
  */
 #define MBEDTLS_VERSION_MAJOR  2
-#define MBEDTLS_VERSION_MINOR  12
-#define MBEDTLS_VERSION_PATCH  0
+#define MBEDTLS_VERSION_MINOR  13
+#define MBEDTLS_VERSION_PATCH  1
 
 /**
  * The single version number has the following structure:
  *    MMNNPP00
  *    Major version | Minor version | Patch version
  */
-#define MBEDTLS_VERSION_NUMBER         0x020C0000
-#define MBEDTLS_VERSION_STRING         "2.12.0"
-#define MBEDTLS_VERSION_STRING_FULL    "mbed TLS 2.12.0"
+#define MBEDTLS_VERSION_NUMBER         0x020D0100
+#define MBEDTLS_VERSION_STRING         "2.13.1"
+#define MBEDTLS_VERSION_STRING_FULL    "mbed TLS 2.13.1"
 
 #if defined(MBEDTLS_VERSION_C)
 
diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index 5115b96..275eda3 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -159,15 +159,15 @@
 
 if(USE_SHARED_MBEDTLS_LIBRARY)
     add_library(mbedcrypto SHARED ${src_crypto})
-    set_target_properties(mbedcrypto PROPERTIES VERSION 2.12.0 SOVERSION 3)
+    set_target_properties(mbedcrypto PROPERTIES VERSION 2.13.1 SOVERSION 3)
     target_link_libraries(mbedcrypto ${libs})
 
     add_library(mbedx509 SHARED ${src_x509})
-    set_target_properties(mbedx509 PROPERTIES VERSION 2.12.0 SOVERSION 0)
+    set_target_properties(mbedx509 PROPERTIES VERSION 2.13.1 SOVERSION 0)
     target_link_libraries(mbedx509 ${libs} mbedcrypto)
 
     add_library(mbedtls SHARED ${src_tls})
-    set_target_properties(mbedtls PROPERTIES VERSION 2.12.0 SOVERSION 11)
+    set_target_properties(mbedtls PROPERTIES VERSION 2.13.1 SOVERSION 12)
     target_link_libraries(mbedtls ${libs} mbedx509)
 
     install(TARGETS mbedtls mbedx509 mbedcrypto
diff --git a/library/Makefile b/library/Makefile
index ac88d4c..430c598 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -35,7 +35,7 @@
 endif
 endif
 
-SOEXT_TLS=so.11
+SOEXT_TLS=so.12
 SOEXT_X509=so.0
 SOEXT_CRYPTO=so.3
 
diff --git a/library/ecp.c b/library/ecp.c
index 68c6f49..9e2c085 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -1897,7 +1897,6 @@
             mbedtls_mpi_get_bit( d, 1 ) != 0 ||
             mbedtls_mpi_bitlen( d ) - 1 != grp->nbits ) /* mbedtls_mpi_bitlen is one-based! */
             return( MBEDTLS_ERR_ECP_INVALID_KEY );
-        else
 
         /* see [Curve25519] page 5 */
         if( grp->nbits == 254 && mbedtls_mpi_get_bit( d, 2 ) != 0 )
diff --git a/library/error.c b/library/error.c
index 774244b..6c88689 100644
--- a/library/error.c
+++ b/library/error.c
@@ -515,6 +515,8 @@
             mbedtls_snprintf( buf, buflen, "SSL - Internal-only message signaling that further message-processing should be done" );
         if( use_ret == -(MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS) )
             mbedtls_snprintf( buf, buflen, "SSL - The asynchronous operation is not completed yet" );
+        if( use_ret == -(MBEDTLS_ERR_SSL_EARLY_MESSAGE) )
+            mbedtls_snprintf( buf, buflen, "SSL - Internal-only message signaling that a message arrived early" );
 #endif /* MBEDTLS_SSL_TLS_C */
 
 #if defined(MBEDTLS_X509_USE_C) || defined(MBEDTLS_X509_CREATE_C)
diff --git a/library/platform_util.c b/library/platform_util.c
index 1a57de9..ca5fe4f 100644
--- a/library/platform_util.c
+++ b/library/platform_util.c
@@ -20,6 +20,14 @@
  *  This file is part of Mbed TLS (https://tls.mbed.org)
  */
 
+/*
+ * Ensure gmtime_r is available even with -std=c99; must be defined before
+ * config.h, which pulls in glibc's features.h. Harmless on other platforms.
+ */
+#if !defined(_POSIX_C_SOURCE)
+#define _POSIX_C_SOURCE 200112L
+#endif
+
 #if !defined(MBEDTLS_CONFIG_FILE)
 #include "mbedtls/config.h"
 #else
@@ -27,6 +35,7 @@
 #endif
 
 #include "mbedtls/platform_util.h"
+#include "mbedtls/threading.h"
 
 #include <stddef.h>
 #include <string.h>
@@ -65,3 +74,62 @@
     memset_func( buf, 0, len );
 }
 #endif /* MBEDTLS_PLATFORM_ZEROIZE_ALT */
+
+#if defined(MBEDTLS_HAVE_TIME_DATE) && !defined(MBEDTLS_PLATFORM_GMTIME_R_ALT)
+#include <time.h>
+#if !defined(_WIN32) && (defined(unix) || \
+    defined(__unix) || defined(__unix__) || (defined(__APPLE__) && \
+    defined(__MACH__)))
+#include <unistd.h>
+#endif /* !_WIN32 && (unix || __unix || __unix__ ||
+        * (__APPLE__ && __MACH__)) */
+
+#if !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) ||     \
+       ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) &&                     \
+         _POSIX_THREAD_SAFE_FUNCTIONS >= 20112L ) )
+/*
+ * This is a convenience shorthand macro to avoid checking the long
+ * preprocessor conditions above. Ideally, we could expose this macro in
+ * platform_util.h and simply use it in platform_util.c, threading.c and
+ * threading.h. However, this macro is not part of the Mbed TLS public API, so
+ * we keep it private by only defining it in this file
+ */
+#if ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) )
+#define PLATFORM_UTIL_USE_GMTIME
+#endif /* ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) ) */
+
+#endif /* !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) ||     \
+             ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) &&                     \
+                _POSIX_THREAD_SAFE_FUNCTIONS >= 20112L ) ) */
+
+struct tm *mbedtls_platform_gmtime_r( const mbedtls_time_t *tt,
+                                      struct tm *tm_buf )
+{
+#if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
+    return( ( gmtime_s( tm_buf, tt ) == 0 ) ? tm_buf : NULL );
+#elif !defined(PLATFORM_UTIL_USE_GMTIME)
+    return( gmtime_r( tt, tm_buf ) );
+#else
+    struct tm *lt;
+
+#if defined(MBEDTLS_THREADING_C)
+    if( mbedtls_mutex_lock( &mbedtls_threading_gmtime_mutex ) != 0 )
+        return( NULL );
+#endif /* MBEDTLS_THREADING_C */
+
+    lt = gmtime( tt );
+
+    if( lt != NULL )
+    {
+        memcpy( tm_buf, lt, sizeof( struct tm ) );
+    }
+
+#if defined(MBEDTLS_THREADING_C)
+    if( mbedtls_mutex_unlock( &mbedtls_threading_gmtime_mutex ) != 0 )
+        return( NULL );
+#endif /* MBEDTLS_THREADING_C */
+
+    return( ( lt == NULL ) ? NULL : tm_buf );
+#endif /* _WIN32 && !EFIX64 && !EFI32 */
+}
+#endif /* MBEDTLS_HAVE_TIME_DATE && MBEDTLS_PLATFORM_GMTIME_R_ALT */
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 321d636..8385720 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -1088,12 +1088,21 @@
         mbedtls_ssl_send_flight_completed( ssl );
 #endif
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+        ( ret = mbedtls_ssl_flight_transmit( ssl ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_flight_transmit", ret );
+        return( ret );
+    }
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write client hello" ) );
 
     return( 0 );
@@ -1491,7 +1500,7 @@
 
     buf = ssl->in_msg;
 
-    if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
     {
         /* No alert on a read error. */
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret );
@@ -2340,7 +2349,7 @@
 #endif /* MBEDTLS_KEY_EXCHANGE_ECDH_RSA_ENABLED ||
           MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA_ENABLED */
 
-    if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret );
         return( ret );
@@ -2647,7 +2656,7 @@
         return( 0 );
     }
 
-    if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret );
         return( ret );
@@ -2721,7 +2730,7 @@
      * therefore the buffer length at this point must be greater than that
      * regardless of the actual code path.
      */
-    if( ssl->in_hslen <= mbedtls_ssl_hs_hdr_len( ssl ) + 3 + n )
+    if( ssl->in_hslen <= mbedtls_ssl_hs_hdr_len( ssl ) + 2 + n )
     {
         MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad certificate request message" ) );
         mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
@@ -2799,7 +2808,7 @@
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse server hello done" ) );
 
-    if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret );
         return( ret );
@@ -3075,9 +3084,9 @@
 
     ssl->state++;
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
@@ -3260,9 +3269,9 @@
 
     ssl->state++;
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
@@ -3288,7 +3297,7 @@
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse new session ticket" ) );
 
-    if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret );
         return( ret );
@@ -3323,8 +3332,8 @@
 
     msg = ssl->in_msg + mbedtls_ssl_hs_hdr_len( ssl );
 
-    lifetime = ( msg[0] << 24 ) | ( msg[1] << 16 ) |
-               ( msg[2] <<  8 ) | ( msg[3]       );
+    lifetime = ( ((uint32_t) msg[0]) << 24 ) | ( msg[1] << 16 ) |
+               ( msg[2] << 8 ) | ( msg[3] );
 
     ticket_len = ( msg[4] << 8 ) | ( msg[5] );
 
@@ -3402,10 +3411,10 @@
     if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
         ssl->handshake->retransmit_state == MBEDTLS_SSL_RETRANS_SENDING )
     {
-        if( ( ret = mbedtls_ssl_resend( ssl ) ) != 0 )
+        if( ( ret = mbedtls_ssl_flight_transmit( ssl ) ) != 0 )
             return( ret );
     }
-#endif
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
 
     /* Change state now, so that it is right in mbedtls_ssl_read_record(), used
      * by DTLS for dropping out-of-sequence ChangeCipherSpec records */
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 2872f1f..36ca0d6 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -1294,7 +1294,7 @@
             return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
         }
 
-        memcpy( ssl->out_ctr + 2, ssl->in_ctr + 2, 6 );
+        memcpy( ssl->cur_out_ctr + 2, ssl->in_ctr + 2, 6 );
 
 #if defined(MBEDTLS_SSL_DTLS_ANTI_REPLAY)
         if( mbedtls_ssl_dtls_replay_check( ssl ) != 0 )
@@ -2384,12 +2384,21 @@
 
     ssl->state = MBEDTLS_SSL_SERVER_HELLO_VERIFY_REQUEST_SENT;
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+        ( ret = mbedtls_ssl_flight_transmit( ssl ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_flight_transmit", ret );
+        return( ret );
+    }
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write hello verify request" ) );
 
     return( 0 );
@@ -2624,7 +2633,7 @@
     ssl->out_msgtype = MBEDTLS_SSL_MSG_HANDSHAKE;
     ssl->out_msg[0]  = MBEDTLS_SSL_HS_SERVER_HELLO;
 
-    ret = mbedtls_ssl_write_record( ssl );
+    ret = mbedtls_ssl_write_handshake_msg( ssl );
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write server hello" ) );
 
@@ -2819,7 +2828,7 @@
     ssl->out_msg[4 + ct_len + sa_len] = (unsigned char)( total_dn_size  >> 8 );
     ssl->out_msg[5 + ct_len + sa_len] = (unsigned char)( total_dn_size       );
 
-    ret = mbedtls_ssl_write_record( ssl );
+    ret = mbedtls_ssl_write_handshake_msg( ssl );
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write certificate request" ) );
 
@@ -3336,9 +3345,9 @@
 
     ssl->state++;
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
@@ -3363,12 +3372,21 @@
         mbedtls_ssl_send_flight_completed( ssl );
 #endif
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+        ( ret = mbedtls_ssl_flight_transmit( ssl ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_flight_transmit", ret );
+        return( ret );
+    }
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write server hello done" ) );
 
     return( 0 );
@@ -3710,7 +3728,7 @@
     }
     else
 #endif
-    if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret );
         return( ret );
@@ -4020,25 +4038,10 @@
     }
 
     /* Read the message without adding it to the checksum */
-    do {
-
-        do ret = mbedtls_ssl_read_record_layer( ssl );
-        while( ret == MBEDTLS_ERR_SSL_CONTINUE_PROCESSING );
-
-        if( ret != 0 )
-        {
-            MBEDTLS_SSL_DEBUG_RET( 1, ( "mbedtls_ssl_read_record_layer" ), ret );
-            return( ret );
-        }
-
-        ret = mbedtls_ssl_handle_message_type( ssl );
-
-    } while( MBEDTLS_ERR_SSL_NON_FATAL           == ret ||
-             MBEDTLS_ERR_SSL_CONTINUE_PROCESSING == ret );
-
+    ret = mbedtls_ssl_read_record( ssl, 0 /* no checksum update */ );
     if( 0 != ret )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, ( "mbedtls_ssl_handle_message_type" ), ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, ( "mbedtls_ssl_read_record" ), ret );
         return( ret );
     }
 
@@ -4227,9 +4230,9 @@
      */
     ssl->handshake->new_session_ticket = 0;
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
@@ -4258,10 +4261,10 @@
     if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
         ssl->handshake->retransmit_state == MBEDTLS_SSL_RETRANS_SENDING )
     {
-        if( ( ret = mbedtls_ssl_resend( ssl ) ) != 0 )
+        if( ( ret = mbedtls_ssl_flight_transmit( ssl ) ) != 0 )
             return( ret );
     }
-#endif
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
 
     switch( ssl->state )
     {
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 3b047fc..8bd74db 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -54,6 +54,9 @@
 #include "mbedtls/oid.h"
 #endif
 
+static void ssl_reset_in_out_pointers( mbedtls_ssl_context *ssl );
+static uint32_t ssl_get_hs_total_len( mbedtls_ssl_context const *ssl );
+
 /* Length of the "epoch" field in the record header */
 static inline size_t ssl_ep_len( const mbedtls_ssl_context *ssl )
 {
@@ -96,7 +99,101 @@
     return( 0 );
 }
 
+static void ssl_update_out_pointers( mbedtls_ssl_context *ssl,
+                                     mbedtls_ssl_transform *transform );
+static void ssl_update_in_pointers( mbedtls_ssl_context *ssl,
+                                    mbedtls_ssl_transform *transform );
+
+#define SSL_DONT_FORCE_FLUSH 0
+#define SSL_FORCE_FLUSH      1
+
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
+
+/* Forward declarations for functions related to message buffering. */
+static void ssl_buffering_free( mbedtls_ssl_context *ssl );
+static void ssl_buffering_free_slot( mbedtls_ssl_context *ssl,
+                                     uint8_t slot );
+static void ssl_free_buffered_record( mbedtls_ssl_context *ssl );
+static int ssl_load_buffered_message( mbedtls_ssl_context *ssl );
+static int ssl_load_buffered_record( mbedtls_ssl_context *ssl );
+static int ssl_buffer_message( mbedtls_ssl_context *ssl );
+static int ssl_buffer_future_record( mbedtls_ssl_context *ssl );
+static int ssl_next_record_is_in_datagram( mbedtls_ssl_context *ssl );
+
+static size_t ssl_get_current_mtu( const mbedtls_ssl_context *ssl );
+static size_t ssl_get_maximum_datagram_size( mbedtls_ssl_context const *ssl )
+{
+    size_t mtu = ssl_get_current_mtu( ssl );
+
+    if( mtu != 0 && mtu < MBEDTLS_SSL_OUT_BUFFER_LEN )
+        return( mtu );
+
+    return( MBEDTLS_SSL_OUT_BUFFER_LEN );
+}
+
+static int ssl_get_remaining_space_in_datagram( mbedtls_ssl_context const *ssl )
+{
+    size_t const bytes_written = ssl->out_left;
+    size_t const mtu           = ssl_get_maximum_datagram_size( ssl );
+
+    /* Double-check that the write-index hasn't gone
+     * past what we can transmit in a single datagram. */
+    if( bytes_written > mtu )
+    {
+        /* Should never happen... */
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    return( (int) ( mtu - bytes_written ) );
+}
+
+static int ssl_get_remaining_payload_in_datagram( mbedtls_ssl_context const *ssl )
+{
+    int ret;
+    size_t remaining, expansion;
+    size_t max_len = MBEDTLS_SSL_MAX_CONTENT_LEN;
+
+#if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
+    const size_t mfl = mbedtls_ssl_get_max_frag_len( ssl );
+
+    if( max_len > mfl )
+        max_len = mfl;
+
+    /* By the standard (RFC 6066 Sect. 4), the MFL extension
+     * only limits the maximum record payload size, so in theory
+     * we would be allowed to pack multiple records of payload size
+     * MFL into a single datagram. However, this would mean that there's
+     * no way to explicitly communicate MTU restrictions to the peer.
+     *
+     * The following reduction of max_len makes sure that we never
+     * write datagrams larger than MFL + Record Expansion Overhead.
+     */
+    if( max_len <= ssl->out_left )
+        return( 0 );
+
+    max_len -= ssl->out_left;
+#endif
+
+    ret = ssl_get_remaining_space_in_datagram( ssl );
+    if( ret < 0 )
+        return( ret );
+    remaining = (size_t) ret;
+
+    ret = mbedtls_ssl_get_record_expansion( ssl );
+    if( ret < 0 )
+        return( ret );
+    expansion = (size_t) ret;
+
+    if( remaining <= expansion )
+        return( 0 );
+
+    remaining -= expansion;
+    if( remaining >= max_len )
+        remaining = max_len;
+
+    return( (int) remaining );
+}
+
 /*
  * Double the retransmit timeout value, within the allowed range,
  * returning -1 if the maximum value has already been reached.
@@ -108,6 +205,15 @@
     if( ssl->handshake->retransmit_timeout >= ssl->conf->hs_timeout_max )
         return( -1 );
 
+    /* Implement the final paragraph of RFC 6347 section 4.1.1.1
+     * in the following way: after the initial transmission and a first
+     * retransmission, back off to a temporary estimated MTU of 508 bytes.
+     * This value is guaranteed to be deliverable (if not guaranteed to be
+     * delivered) of any compliant IPv4 (and IPv6) network, and should work
+     * on most non-IP stacks too. */
+    if( ssl->handshake->retransmit_timeout != ssl->conf->hs_timeout_min )
+        ssl->handshake->mtu = 508;
+
     new_timeout = 2 * ssl->handshake->retransmit_timeout;
 
     /* Avoid arithmetic overflow and range overflow */
@@ -1345,14 +1451,6 @@
     MBEDTLS_SSL_DEBUG_BUF( 4, "before encrypt: output payload",
                       ssl->out_msg, ssl->out_msglen );
 
-    if( ssl->out_msglen > MBEDTLS_SSL_OUT_CONTENT_LEN )
-    {
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "Record content %u too large, maximum %d",
-                                    (unsigned) ssl->out_msglen,
-                                    MBEDTLS_SSL_OUT_CONTENT_LEN ) );
-        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
-    }
-
     /*
      * Add MAC before if needed
      */
@@ -1626,6 +1724,8 @@
 #if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
         if( auth_done == 0 )
         {
+            unsigned char mac[MBEDTLS_SSL_MAC_ADD];
+
             /*
              * MAC(MAC_write_key, seq_num +
              *     TLSCipherText.type +
@@ -1648,10 +1748,12 @@
             mbedtls_md_hmac_update( &ssl->transform_out->md_ctx_enc, pseudo_hdr, 13 );
             mbedtls_md_hmac_update( &ssl->transform_out->md_ctx_enc,
                              ssl->out_iv, ssl->out_msglen );
-            mbedtls_md_hmac_finish( &ssl->transform_out->md_ctx_enc,
-                             ssl->out_iv + ssl->out_msglen );
+            mbedtls_md_hmac_finish( &ssl->transform_out->md_ctx_enc, mac );
             mbedtls_md_hmac_reset( &ssl->transform_out->md_ctx_enc );
 
+            memcpy( ssl->out_iv + ssl->out_msglen, mac,
+                    ssl->transform_out->maclen );
+
             ssl->out_msglen += ssl->transform_out->maclen;
             auth_done++;
         }
@@ -2644,7 +2746,7 @@
 int mbedtls_ssl_flush_output( mbedtls_ssl_context *ssl )
 {
     int ret;
-    unsigned char *buf, i;
+    unsigned char *buf;
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> flush output" ) );
 
@@ -2667,8 +2769,7 @@
         MBEDTLS_SSL_DEBUG_MSG( 2, ( "message length: %d, out_left: %d",
                        mbedtls_ssl_hdr_len( ssl ) + ssl->out_msglen, ssl->out_left ) );
 
-        buf = ssl->out_hdr + mbedtls_ssl_hdr_len( ssl ) +
-              ssl->out_msglen - ssl->out_left;
+        buf = ssl->out_hdr - ssl->out_left;
         ret = ssl->f_send( ssl->p_bio, buf, ssl->out_left );
 
         MBEDTLS_SSL_DEBUG_RET( 2, "ssl->f_send", ret );
@@ -2687,16 +2788,17 @@
         ssl->out_left -= ret;
     }
 
-    for( i = 8; i > ssl_ep_len( ssl ); i-- )
-        if( ++ssl->out_ctr[i - 1] != 0 )
-            break;
-
-    /* The loop goes to its end iff the counter is wrapping */
-    if( i == ssl_ep_len( ssl ) )
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
     {
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "outgoing message counter would wrap" ) );
-        return( MBEDTLS_ERR_SSL_COUNTER_WRAPPING );
+        ssl->out_hdr = ssl->out_buf;
     }
+    else
+#endif
+    {
+        ssl->out_hdr = ssl->out_buf + 8;
+    }
+    ssl_update_out_pointers( ssl, ssl->transform_out );
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= flush output" ) );
 
@@ -2713,6 +2815,9 @@
 static int ssl_flight_append( mbedtls_ssl_context *ssl )
 {
     mbedtls_ssl_flight_item *msg;
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> ssl_flight_append" ) );
+    MBEDTLS_SSL_DEBUG_BUF( 4, "message appended to flight",
+                           ssl->out_msg, ssl->out_msglen );
 
     /* Allocate space for current message */
     if( ( msg = mbedtls_calloc( 1, sizeof(  mbedtls_ssl_flight_item ) ) ) == NULL )
@@ -2746,6 +2851,7 @@
         cur->next = msg;
     }
 
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= ssl_flight_append" ) );
     return( 0 );
 }
 
@@ -2794,19 +2900,12 @@
     ssl->handshake->alt_transform_out = tmp_transform;
 
     /* Swap epoch + sequence_number */
-    memcpy( tmp_out_ctr,                 ssl->out_ctr,                8 );
-    memcpy( ssl->out_ctr,                ssl->handshake->alt_out_ctr, 8 );
+    memcpy( tmp_out_ctr,                 ssl->cur_out_ctr,            8 );
+    memcpy( ssl->cur_out_ctr,            ssl->handshake->alt_out_ctr, 8 );
     memcpy( ssl->handshake->alt_out_ctr, tmp_out_ctr,                 8 );
 
     /* Adjust to the newly activated transform */
-    if( ssl->transform_out != NULL &&
-        ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
-    {
-        ssl->out_msg = ssl->out_iv + ssl->transform_out->ivlen -
-                                     ssl->transform_out->fixed_ivlen;
-    }
-    else
-        ssl->out_msg = ssl->out_iv;
+    ssl_update_out_pointers( ssl, ssl->transform_out );
 
 #if defined(MBEDTLS_SSL_HW_RECORD_ACCEL)
     if( mbedtls_ssl_hw_record_activate != NULL )
@@ -2822,20 +2921,38 @@
 
 /*
  * Retransmit the current flight of messages.
+ */
+int mbedtls_ssl_resend( mbedtls_ssl_context *ssl )
+{
+    int ret = 0;
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> mbedtls_ssl_resend" ) );
+
+    ret = mbedtls_ssl_flight_transmit( ssl );
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= mbedtls_ssl_resend" ) );
+
+    return( ret );
+}
+
+/*
+ * Transmit or retransmit the current flight of messages.
  *
  * Need to remember the current message in case flush_output returns
  * WANT_WRITE, causing us to exit this function and come back later.
  * This function must be called until state is no longer SENDING.
  */
-int mbedtls_ssl_resend( mbedtls_ssl_context *ssl )
+int mbedtls_ssl_flight_transmit( mbedtls_ssl_context *ssl )
 {
-    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> mbedtls_ssl_resend" ) );
+    int ret;
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> mbedtls_ssl_flight_transmit" ) );
 
     if( ssl->handshake->retransmit_state != MBEDTLS_SSL_RETRANS_SENDING )
     {
-        MBEDTLS_SSL_DEBUG_MSG( 2, ( "initialise resending" ) );
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "initialise flight transmission" ) );
 
         ssl->handshake->cur_msg = ssl->handshake->flight;
+        ssl->handshake->cur_msg_p = ssl->handshake->flight->p + 12;
         ssl_swap_epochs( ssl );
 
         ssl->handshake->retransmit_state = MBEDTLS_SSL_RETRANS_SENDING;
@@ -2843,33 +2960,129 @@
 
     while( ssl->handshake->cur_msg != NULL )
     {
-        int ret;
-        mbedtls_ssl_flight_item *cur = ssl->handshake->cur_msg;
+        size_t max_frag_len;
+        const mbedtls_ssl_flight_item * const cur = ssl->handshake->cur_msg;
+
+        int const is_finished =
+            ( cur->type == MBEDTLS_SSL_MSG_HANDSHAKE &&
+              cur->p[0] == MBEDTLS_SSL_HS_FINISHED );
+
+        uint8_t const force_flush = ssl->disable_datagram_packing == 1 ?
+            SSL_FORCE_FLUSH : SSL_DONT_FORCE_FLUSH;
 
         /* Swap epochs before sending Finished: we can't do it after
          * sending ChangeCipherSpec, in case write returns WANT_READ.
          * Must be done before copying, may change out_msg pointer */
-        if( cur->type == MBEDTLS_SSL_MSG_HANDSHAKE &&
-            cur->p[0] == MBEDTLS_SSL_HS_FINISHED )
+        if( is_finished && ssl->handshake->cur_msg_p == ( cur->p + 12 ) )
         {
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "swap epochs to send finished message" ) );
             ssl_swap_epochs( ssl );
         }
 
-        memcpy( ssl->out_msg, cur->p, cur->len );
-        ssl->out_msglen = cur->len;
-        ssl->out_msgtype = cur->type;
+        ret = ssl_get_remaining_payload_in_datagram( ssl );
+        if( ret < 0 )
+            return( ret );
+        max_frag_len = (size_t) ret;
 
-        ssl->handshake->cur_msg = cur->next;
+        /* CCS is copied as is, while HS messages may need fragmentation */
+        if( cur->type == MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC )
+        {
+            if( max_frag_len == 0 )
+            {
+                if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 )
+                    return( ret );
 
-        MBEDTLS_SSL_DEBUG_BUF( 3, "resent handshake message header", ssl->out_msg, 12 );
+                continue;
+            }
 
-        if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+            memcpy( ssl->out_msg, cur->p, cur->len );
+            ssl->out_msglen  = cur->len;
+            ssl->out_msgtype = cur->type;
+
+            /* Update position inside current message */
+            ssl->handshake->cur_msg_p += cur->len;
+        }
+        else
+        {
+            const unsigned char * const p = ssl->handshake->cur_msg_p;
+            const size_t hs_len = cur->len - 12;
+            const size_t frag_off = p - ( cur->p + 12 );
+            const size_t rem_len = hs_len - frag_off;
+            size_t cur_hs_frag_len, max_hs_frag_len;
+
+            if( ( max_frag_len < 12 ) || ( max_frag_len == 12 && hs_len != 0 ) )
+            {
+                if( is_finished )
+                    ssl_swap_epochs( ssl );
+
+                if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 )
+                    return( ret );
+
+                continue;
+            }
+            max_hs_frag_len = max_frag_len - 12;
+
+            cur_hs_frag_len = rem_len > max_hs_frag_len ?
+                max_hs_frag_len : rem_len;
+
+            if( frag_off == 0 && cur_hs_frag_len != hs_len )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 2, ( "fragmenting handshake message (%u > %u)",
+                                            (unsigned) cur_hs_frag_len,
+                                            (unsigned) max_hs_frag_len ) );
+            }
+
+            /* Messages are stored with handshake headers as if not fragmented,
+             * copy beginning of headers then fill fragmentation fields.
+             * Handshake headers: type(1) len(3) seq(2) f_off(3) f_len(3) */
+            memcpy( ssl->out_msg, cur->p, 6 );
+
+            ssl->out_msg[6] = ( ( frag_off >> 16 ) & 0xff );
+            ssl->out_msg[7] = ( ( frag_off >>  8 ) & 0xff );
+            ssl->out_msg[8] = ( ( frag_off       ) & 0xff );
+
+            ssl->out_msg[ 9] = ( ( cur_hs_frag_len >> 16 ) & 0xff );
+            ssl->out_msg[10] = ( ( cur_hs_frag_len >>  8 ) & 0xff );
+            ssl->out_msg[11] = ( ( cur_hs_frag_len       ) & 0xff );
+
+            MBEDTLS_SSL_DEBUG_BUF( 3, "handshake header", ssl->out_msg, 12 );
+
+            /* Copy the handshake message content and set records fields */
+            memcpy( ssl->out_msg + 12, p, cur_hs_frag_len );
+            ssl->out_msglen = cur_hs_frag_len + 12;
+            ssl->out_msgtype = cur->type;
+
+            /* Update position inside current message */
+            ssl->handshake->cur_msg_p += cur_hs_frag_len;
+        }
+
+        /* If done with the current message move to the next one if any */
+        if( ssl->handshake->cur_msg_p >= cur->p + cur->len )
+        {
+            if( cur->next != NULL )
+            {
+                ssl->handshake->cur_msg = cur->next;
+                ssl->handshake->cur_msg_p = cur->next->p + 12;
+            }
+            else
+            {
+                ssl->handshake->cur_msg = NULL;
+                ssl->handshake->cur_msg_p = NULL;
+            }
+        }
+
+        /* Actually send the message out */
+        if( ( ret = mbedtls_ssl_write_record( ssl, force_flush ) ) != 0 )
         {
             MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
             return( ret );
         }
     }
 
+    if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 )
+        return( ret );
+
+    /* Update state and set timer */
     if( ssl->state == MBEDTLS_SSL_HANDSHAKE_OVER )
         ssl->handshake->retransmit_state = MBEDTLS_SSL_RETRANS_FINISHED;
     else
@@ -2878,7 +3091,7 @@
         ssl_set_timer( ssl, ssl->handshake->retransmit_timeout );
     }
 
-    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= mbedtls_ssl_resend" ) );
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= mbedtls_ssl_flight_transmit" ) );
 
     return( 0 );
 }
@@ -2896,6 +3109,12 @@
     /* The next incoming flight will start with this msg_seq */
     ssl->handshake->in_flight_start_seq = ssl->handshake->in_msg_seq;
 
+    /* We don't want to remember CCS's across flight boundaries. */
+    ssl->handshake->buffering.seen_ccs = 0;
+
+    /* Clear future message buffering structure. */
+    ssl_buffering_free( ssl );
+
     /* Cancel timer */
     ssl_set_timer( ssl, 0 );
 
@@ -2927,43 +3146,100 @@
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
 /*
- * Record layer functions
+ * Handshake layer functions
  */
 
 /*
- * Write current record.
- * Uses ssl->out_msgtype, ssl->out_msglen and bytes at ssl->out_msg.
+ * Write (DTLS: or queue) current handshake (including CCS) message.
+ *
+ *  - fill in handshake headers
+ *  - update handshake checksum
+ *  - DTLS: save message for resending
+ *  - then pass to the record layer
+ *
+ * DTLS: except for HelloRequest, messages are only queued, and will only be
+ * actually sent when calling flight_transmit() or resend().
+ *
+ * Inputs:
+ *  - ssl->out_msglen: 4 + actual handshake message len
+ *      (4 is the size of handshake headers for TLS)
+ *  - ssl->out_msg[0]: the handshake type (ClientHello, ServerHello, etc)
+ *  - ssl->out_msg + 4: the handshake message body
+ *
+ * Outputs, ie state before passing to flight_append() or write_record():
+ *   - ssl->out_msglen: the length of the record contents
+ *      (including handshake headers but excluding record headers)
+ *   - ssl->out_msg: the record contents (handshake headers + content)
  */
-int mbedtls_ssl_write_record( mbedtls_ssl_context *ssl )
+int mbedtls_ssl_write_handshake_msg( mbedtls_ssl_context *ssl )
 {
-    int ret, done = 0, out_msg_type;
-    size_t len = ssl->out_msglen;
+    int ret;
+    const size_t hs_len = ssl->out_msglen - 4;
+    const unsigned char hs_type = ssl->out_msg[0];
 
-    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write record" ) );
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write handshake message" ) );
+
+    /*
+     * Sanity checks
+     */
+    if( ssl->out_msgtype != MBEDTLS_SSL_MSG_HANDSHAKE          &&
+        ssl->out_msgtype != MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC )
+    {
+        /* In SSLv3, the client might send a NoCertificate alert. */
+#if defined(MBEDTLS_SSL_PROTO_SSL3) && defined(MBEDTLS_SSL_CLI_C)
+        if( ! ( ssl->minor_ver      == MBEDTLS_SSL_MINOR_VERSION_0 &&
+                ssl->out_msgtype    == MBEDTLS_SSL_MSG_ALERT       &&
+                ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT ) )
+#endif /* MBEDTLS_SSL_PROTO_SSL3 && MBEDTLS_SSL_SRV_C */
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+    }
+
+    if( ssl->out_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE &&
+        hs_type != MBEDTLS_SSL_HS_HELLO_REQUEST &&
+        ssl->handshake == NULL )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
 
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
     if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
         ssl->handshake != NULL &&
         ssl->handshake->retransmit_state == MBEDTLS_SSL_RETRANS_SENDING )
     {
-        ; /* Skip special handshake treatment when resending */
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
     }
-    else
 #endif
+
+    /* Double-check that we did not exceed the bounds
+     * of the outgoing record buffer.
+     * This should never fail as the various message
+     * writing functions must obey the bounds of the
+     * outgoing record buffer, but better be safe.
+     *
+     * Note: We deliberately do not check for the MTU or MFL here.
+     */
+    if( ssl->out_msglen > MBEDTLS_SSL_OUT_CONTENT_LEN )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "Record too large: "
+                                    "size %u, maximum %u",
+                                    (unsigned) ssl->out_msglen,
+                                    (unsigned) MBEDTLS_SSL_OUT_CONTENT_LEN ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    /*
+     * Fill handshake headers
+     */
     if( ssl->out_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE )
     {
-        out_msg_type = ssl->out_msg[0];
-
-        if( out_msg_type != MBEDTLS_SSL_HS_HELLO_REQUEST &&
-            ssl->handshake == NULL )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
-            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
-        }
-
-        ssl->out_msg[1] = (unsigned char)( ( len - 4 ) >> 16 );
-        ssl->out_msg[2] = (unsigned char)( ( len - 4 ) >>  8 );
-        ssl->out_msg[3] = (unsigned char)( ( len - 4 )       );
+        ssl->out_msg[1] = (unsigned char)( hs_len >> 16 );
+        ssl->out_msg[2] = (unsigned char)( hs_len >>  8 );
+        ssl->out_msg[3] = (unsigned char)( hs_len       );
 
         /*
          * DTLS has additional fields in the Handshake layer,
@@ -2980,17 +3256,16 @@
             {
                 MBEDTLS_SSL_DEBUG_MSG( 1, ( "DTLS handshake message too large: "
                               "size %u, maximum %u",
-                               (unsigned) ( ssl->in_hslen - 4 ),
+                               (unsigned) ( hs_len ),
                                (unsigned) ( MBEDTLS_SSL_OUT_CONTENT_LEN - 12 ) ) );
                 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
             }
 
-            memmove( ssl->out_msg + 12, ssl->out_msg + 4, len - 4 );
+            memmove( ssl->out_msg + 12, ssl->out_msg + 4, hs_len );
             ssl->out_msglen += 8;
-            len += 8;
 
             /* Write message_seq and update it, except for HelloRequest */
-            if( out_msg_type != MBEDTLS_SSL_HS_HELLO_REQUEST )
+            if( hs_type != MBEDTLS_SSL_HS_HELLO_REQUEST )
             {
                 ssl->out_msg[4] = ( ssl->handshake->out_msg_seq >> 8 ) & 0xFF;
                 ssl->out_msg[5] = ( ssl->handshake->out_msg_seq      ) & 0xFF;
@@ -3002,23 +3277,23 @@
                 ssl->out_msg[5] = 0;
             }
 
-            /* We don't fragment, so frag_offset = 0 and frag_len = len */
+            /* Handshake hashes are computed without fragmentation,
+             * so set frag_offset = 0 and frag_len = hs_len for now */
             memset( ssl->out_msg + 6, 0x00, 3 );
             memcpy( ssl->out_msg + 9, ssl->out_msg + 1, 3 );
         }
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
-        if( out_msg_type != MBEDTLS_SSL_HS_HELLO_REQUEST )
-            ssl->handshake->update_checksum( ssl, ssl->out_msg, len );
+        /* Update running hashes of handshake messages seen */
+        if( hs_type != MBEDTLS_SSL_HS_HELLO_REQUEST )
+            ssl->handshake->update_checksum( ssl, ssl->out_msg, ssl->out_msglen );
     }
 
-    /* Save handshake and CCS messages for resending */
+    /* Either send now, or just save to be sent (and resent) later */
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
     if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
-        ssl->handshake != NULL &&
-        ssl->handshake->retransmit_state != MBEDTLS_SSL_RETRANS_SENDING &&
-        ( ssl->out_msgtype == MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC ||
-          ssl->out_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE ) )
+        ( ssl->out_msgtype != MBEDTLS_SSL_MSG_HANDSHAKE ||
+          hs_type != MBEDTLS_SSL_HS_HELLO_REQUEST ) )
     {
         if( ( ret = ssl_flight_append( ssl ) ) != 0 )
         {
@@ -3026,7 +3301,40 @@
             return( ret );
         }
     }
+    else
 #endif
+    {
+        if( ( ret = mbedtls_ssl_write_record( ssl, SSL_FORCE_FLUSH ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "ssl_write_record", ret );
+            return( ret );
+        }
+    }
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write handshake message" ) );
+
+    return( 0 );
+}
+
+/*
+ * Record layer functions
+ */
+
+/*
+ * Write current record.
+ *
+ * Uses:
+ *  - ssl->out_msgtype: type of the message (AppData, Handshake, Alert, CCS)
+ *  - ssl->out_msglen: length of the record content (excl headers)
+ *  - ssl->out_msg: record content
+ */
+int mbedtls_ssl_write_record( mbedtls_ssl_context *ssl, uint8_t force_flush )
+{
+    int ret, done = 0;
+    size_t len = ssl->out_msglen;
+    uint8_t flush = force_flush;
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write record" ) );
 
 #if defined(MBEDTLS_ZLIB_SUPPORT)
     if( ssl->transform_out != NULL &&
@@ -3060,10 +3368,14 @@
 #endif /* MBEDTLS_SSL_HW_RECORD_ACCEL */
     if( !done )
     {
+        unsigned i;
+        size_t protected_record_size;
+
         ssl->out_hdr[0] = (unsigned char) ssl->out_msgtype;
         mbedtls_ssl_write_version( ssl->major_ver, ssl->minor_ver,
                            ssl->conf->transport, ssl->out_hdr + 1 );
 
+        memcpy( ssl->out_ctr, ssl->cur_out_ctr, 8 );
         ssl->out_len[0] = (unsigned char)( len >> 8 );
         ssl->out_len[1] = (unsigned char)( len      );
 
@@ -3080,18 +3392,76 @@
             ssl->out_len[1] = (unsigned char)( len      );
         }
 
-        ssl->out_left = mbedtls_ssl_hdr_len( ssl ) + ssl->out_msglen;
+        protected_record_size = len + mbedtls_ssl_hdr_len( ssl );
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+        /* In case of DTLS, double-check that we don't exceed
+         * the remaining space in the datagram. */
+        if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+        {
+            ret = ssl_get_remaining_space_in_datagram( ssl );
+            if( ret < 0 )
+                return( ret );
+
+            if( protected_record_size > (size_t) ret )
+            {
+                /* Should never happen */
+                return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+            }
+        }
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
 
         MBEDTLS_SSL_DEBUG_MSG( 3, ( "output record: msgtype = %d, "
-                            "version = [%d:%d], msglen = %d",
-                       ssl->out_hdr[0], ssl->out_hdr[1], ssl->out_hdr[2],
-                     ( ssl->out_len[0] << 8 ) | ssl->out_len[1] ) );
+                                    "version = [%d:%d], msglen = %d",
+                                    ssl->out_hdr[0], ssl->out_hdr[1],
+                                    ssl->out_hdr[2], len ) );
 
         MBEDTLS_SSL_DEBUG_BUF( 4, "output record sent to network",
-                       ssl->out_hdr, mbedtls_ssl_hdr_len( ssl ) + ssl->out_msglen );
+                               ssl->out_hdr, protected_record_size );
+
+        ssl->out_left += protected_record_size;
+        ssl->out_hdr  += protected_record_size;
+        ssl_update_out_pointers( ssl, ssl->transform_out );
+
+        for( i = 8; i > ssl_ep_len( ssl ); i-- )
+            if( ++ssl->cur_out_ctr[i - 1] != 0 )
+                break;
+
+        /* The loop goes to its end iff the counter is wrapping */
+        if( i == ssl_ep_len( ssl ) )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "outgoing message counter would wrap" ) );
+            return( MBEDTLS_ERR_SSL_COUNTER_WRAPPING );
+        }
     }
 
-    if( ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 )
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+        flush == SSL_DONT_FORCE_FLUSH )
+    {
+        size_t remaining;
+        ret = ssl_get_remaining_payload_in_datagram( ssl );
+        if( ret < 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "ssl_get_remaining_payload_in_datagram",
+                                   ret );
+            return( ret );
+        }
+
+        remaining = (size_t) ret;
+        if( remaining == 0 )
+        {
+            flush = SSL_FORCE_FLUSH;
+        }
+        else
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "Still %u bytes available in current datagram", (unsigned) remaining ) );
+        }
+    }
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+    if( ( flush == SSL_FORCE_FLUSH ) &&
+        ( ret = mbedtls_ssl_flush_output( ssl ) ) != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_flush_output", ret );
         return( ret );
@@ -3103,6 +3473,52 @@
 }
 
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
+
+static int ssl_hs_is_proper_fragment( mbedtls_ssl_context *ssl )
+{
+    if( ssl->in_msglen < ssl->in_hslen ||
+        memcmp( ssl->in_msg + 6, "\0\0\0",        3 ) != 0 ||
+        memcmp( ssl->in_msg + 9, ssl->in_msg + 1, 3 ) != 0 )
+    {
+        return( 1 );
+    }
+    return( 0 );
+}
+
+static uint32_t ssl_get_hs_frag_len( mbedtls_ssl_context const *ssl )
+{
+    return( ( ssl->in_msg[9] << 16  ) |
+            ( ssl->in_msg[10] << 8  ) |
+              ssl->in_msg[11] );
+}
+
+static uint32_t ssl_get_hs_frag_off( mbedtls_ssl_context const *ssl )
+{
+    return( ( ssl->in_msg[6] << 16 ) |
+            ( ssl->in_msg[7] << 8  ) |
+              ssl->in_msg[8] );
+}
+
+static int ssl_check_hs_header( mbedtls_ssl_context const *ssl )
+{
+    uint32_t msg_len, frag_off, frag_len;
+
+    msg_len  = ssl_get_hs_total_len( ssl );
+    frag_off = ssl_get_hs_frag_off( ssl );
+    frag_len = ssl_get_hs_frag_len( ssl );
+
+    if( frag_off > msg_len )
+        return( -1 );
+
+    if( frag_len > msg_len - frag_off )
+        return( -1 );
+
+    if( frag_len + 12 > ssl->in_msglen )
+        return( -1 );
+
+    return( 0 );
+}
+
 /*
  * Mark bits in bitmask (used for DTLS HS reassembly)
  */
@@ -3164,162 +3580,30 @@
     return( 0 );
 }
 
-/*
- * Reassemble fragmented DTLS handshake messages.
- *
- * Use a temporary buffer for reassembly, divided in two parts:
- * - the first holds the reassembled message (including handshake header),
- * - the second holds a bitmask indicating which parts of the message
- *   (excluding headers) have been received so far.
- */
-static int ssl_reassemble_dtls_handshake( mbedtls_ssl_context *ssl )
+/* msg_len does not include the handshake header */
+static size_t ssl_get_reassembly_buffer_size( size_t msg_len,
+                                              unsigned add_bitmap )
 {
-    unsigned char *msg, *bitmask;
-    size_t frag_len, frag_off;
-    size_t msg_len = ssl->in_hslen - 12; /* Without headers */
+    size_t alloc_len;
 
-    if( ssl->handshake == NULL )
-    {
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "not supported outside handshake (for now)" ) );
-        return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
-    }
+    alloc_len  = 12;                                 /* Handshake header */
+    alloc_len += msg_len;                            /* Content buffer   */
 
-    /*
-     * For first fragment, check size and allocate buffer
-     */
-    if( ssl->handshake->hs_msg == NULL )
-    {
-        size_t alloc_len;
+    if( add_bitmap )
+        alloc_len += msg_len / 8 + ( msg_len % 8 != 0 ); /* Bitmap       */
 
-        MBEDTLS_SSL_DEBUG_MSG( 2, ( "initialize reassembly, total length = %d",
-                            msg_len ) );
-
-        if( ssl->in_hslen > MBEDTLS_SSL_IN_CONTENT_LEN )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "handshake message too large" ) );
-            return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
-        }
-
-        /* The bitmask needs one bit per byte of message excluding header */
-        alloc_len = 12 + msg_len + msg_len / 8 + ( msg_len % 8 != 0 );
-
-        ssl->handshake->hs_msg = mbedtls_calloc( 1, alloc_len );
-        if( ssl->handshake->hs_msg == NULL )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc failed (%d bytes)", alloc_len ) );
-            return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
-        }
-
-        /* Prepare final header: copy msg_type, length and message_seq,
-         * then add standardised fragment_offset and fragment_length */
-        memcpy( ssl->handshake->hs_msg, ssl->in_msg, 6 );
-        memset( ssl->handshake->hs_msg + 6, 0, 3 );
-        memcpy( ssl->handshake->hs_msg + 9,
-                ssl->handshake->hs_msg + 1, 3 );
-    }
-    else
-    {
-        /* Make sure msg_type and length are consistent */
-        if( memcmp( ssl->handshake->hs_msg, ssl->in_msg, 4 ) != 0 )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "fragment header mismatch" ) );
-            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
-        }
-    }
-
-    msg = ssl->handshake->hs_msg + 12;
-    bitmask = msg + msg_len;
-
-    /*
-     * Check and copy current fragment
-     */
-    frag_off = ( ssl->in_msg[6]  << 16 ) |
-               ( ssl->in_msg[7]  << 8  ) |
-                 ssl->in_msg[8];
-    frag_len = ( ssl->in_msg[9]  << 16 ) |
-               ( ssl->in_msg[10] << 8  ) |
-                 ssl->in_msg[11];
-
-    if( frag_off + frag_len > msg_len )
-    {
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid fragment offset/len: %d + %d > %d",
-                          frag_off, frag_len, msg_len ) );
-        return( MBEDTLS_ERR_SSL_INVALID_RECORD );
-    }
-
-    if( frag_len + 12 > ssl->in_msglen )
-    {
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid fragment length: %d + 12 > %d",
-                          frag_len, ssl->in_msglen ) );
-        return( MBEDTLS_ERR_SSL_INVALID_RECORD );
-    }
-
-    MBEDTLS_SSL_DEBUG_MSG( 2, ( "adding fragment, offset = %d, length = %d",
-                        frag_off, frag_len ) );
-
-    memcpy( msg + frag_off, ssl->in_msg + 12, frag_len );
-    ssl_bitmask_set( bitmask, frag_off, frag_len );
-
-    /*
-     * Do we have the complete message by now?
-     * If yes, finalize it, else ask to read the next record.
-     */
-    if( ssl_bitmask_check( bitmask, msg_len ) != 0 )
-    {
-        MBEDTLS_SSL_DEBUG_MSG( 2, ( "message is not complete yet" ) );
-        return( MBEDTLS_ERR_SSL_CONTINUE_PROCESSING );
-    }
-
-    MBEDTLS_SSL_DEBUG_MSG( 2, ( "handshake message completed" ) );
-
-    if( frag_len + 12 < ssl->in_msglen )
-    {
-        /*
-         * We'got more handshake messages in the same record.
-         * This case is not handled now because no know implementation does
-         * that and it's hard to test, so we prefer to fail cleanly for now.
-         */
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "last fragment not alone in its record" ) );
-        return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
-    }
-
-    if( ssl->in_left > ssl->next_record_offset )
-    {
-        /*
-         * We've got more data in the buffer after the current record,
-         * that we don't want to overwrite. Move it before writing the
-         * reassembled message, and adjust in_left and next_record_offset.
-         */
-        unsigned char *cur_remain = ssl->in_hdr + ssl->next_record_offset;
-        unsigned char *new_remain = ssl->in_msg + ssl->in_hslen;
-        size_t remain_len = ssl->in_left - ssl->next_record_offset;
-
-        /* First compute and check new lengths */
-        ssl->next_record_offset = new_remain - ssl->in_hdr;
-        ssl->in_left = ssl->next_record_offset + remain_len;
-
-        if( ssl->in_left > MBEDTLS_SSL_IN_BUFFER_LEN -
-                           (size_t)( ssl->in_hdr - ssl->in_buf ) )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "reassembled message too large for buffer" ) );
-            return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
-        }
-
-        memmove( new_remain, cur_remain, remain_len );
-    }
-
-    memcpy( ssl->in_msg, ssl->handshake->hs_msg, ssl->in_hslen );
-
-    mbedtls_free( ssl->handshake->hs_msg );
-    ssl->handshake->hs_msg = NULL;
-
-    MBEDTLS_SSL_DEBUG_BUF( 3, "reassembled handshake message",
-                   ssl->in_msg, ssl->in_hslen );
-
-    return( 0 );
+    return( alloc_len );
 }
+
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
+static uint32_t ssl_get_hs_total_len( mbedtls_ssl_context const *ssl )
+{
+    return( ( ssl->in_msg[1] << 16 ) |
+            ( ssl->in_msg[2] << 8  ) |
+              ssl->in_msg[3] );
+}
+
 int mbedtls_ssl_prepare_handshake_record( mbedtls_ssl_context *ssl )
 {
     if( ssl->in_msglen < mbedtls_ssl_hs_hdr_len( ssl ) )
@@ -3329,10 +3613,7 @@
         return( MBEDTLS_ERR_SSL_INVALID_RECORD );
     }
 
-    ssl->in_hslen = mbedtls_ssl_hs_hdr_len( ssl ) + (
-                    ( ssl->in_msg[1] << 16 ) |
-                    ( ssl->in_msg[2] << 8  ) |
-                      ssl->in_msg[3] );
+    ssl->in_hslen = mbedtls_ssl_hs_hdr_len( ssl ) + ssl_get_hs_total_len( ssl );
 
     MBEDTLS_SSL_DEBUG_MSG( 3, ( "handshake message: msglen ="
                         " %d, type = %d, hslen = %d",
@@ -3344,12 +3625,26 @@
         int ret;
         unsigned int recv_msg_seq = ( ssl->in_msg[4] << 8 ) | ssl->in_msg[5];
 
+        if( ssl_check_hs_header( ssl ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid handshake header" ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+
         if( ssl->handshake != NULL &&
             ( ( ssl->state   != MBEDTLS_SSL_HANDSHAKE_OVER &&
                 recv_msg_seq != ssl->handshake->in_msg_seq ) ||
               ( ssl->state  == MBEDTLS_SSL_HANDSHAKE_OVER &&
                 ssl->in_msg[0] != MBEDTLS_SSL_HS_CLIENT_HELLO ) ) )
         {
+            if( recv_msg_seq > ssl->handshake->in_msg_seq )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 2, ( "received future handshake message of sequence number %u (next %u)",
+                                            recv_msg_seq,
+                                            ssl->handshake->in_msg_seq ) );
+                return( MBEDTLS_ERR_SSL_EARLY_MESSAGE );
+            }
+
             /* Retransmit only on last message from previous flight, to avoid
              * too many retransmissions.
              * Besides, No sane server ever retransmits HelloVerifyRequest */
@@ -3379,20 +3674,14 @@
         }
         /* Wait until message completion to increment in_msg_seq */
 
-        /* Reassemble if current message is fragmented or reassembly is
-         * already in progress */
-        if( ssl->in_msglen < ssl->in_hslen ||
-            memcmp( ssl->in_msg + 6, "\0\0\0",        3 ) != 0 ||
-            memcmp( ssl->in_msg + 9, ssl->in_msg + 1, 3 ) != 0 ||
-            ( ssl->handshake != NULL && ssl->handshake->hs_msg != NULL ) )
+        /* Message reassembly is handled alongside buffering of future
+         * messages; the commonality is that both handshake fragments and
+         * future messages cannot be forwarded immediately to the
+         * handshake logic layer. */
+        if( ssl_hs_is_proper_fragment( ssl ) == 1 )
         {
             MBEDTLS_SSL_DEBUG_MSG( 2, ( "found fragmented DTLS handshake message" ) );
-
-            if( ( ret = ssl_reassemble_dtls_handshake( ssl ) ) != 0 )
-            {
-                MBEDTLS_SSL_DEBUG_RET( 1, "ssl_reassemble_dtls_handshake", ret );
-                return( ret );
-            }
+            return( MBEDTLS_ERR_SSL_EARLY_MESSAGE );
         }
     }
     else
@@ -3409,9 +3698,9 @@
 
 void mbedtls_ssl_update_handshake_status( mbedtls_ssl_context *ssl )
 {
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
 
-    if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER &&
-        ssl->handshake != NULL )
+    if( ssl->state != MBEDTLS_SSL_HANDSHAKE_OVER && hs != NULL )
     {
         ssl->handshake->update_checksum( ssl, ssl->in_msg, ssl->in_hslen );
     }
@@ -3421,7 +3710,29 @@
     if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
         ssl->handshake != NULL )
     {
-        ssl->handshake->in_msg_seq++;
+        unsigned offset;
+        mbedtls_ssl_hs_buffer *hs_buf;
+
+        /* Increment handshake sequence number */
+        hs->in_msg_seq++;
+
+        /*
+         * Clear up handshake buffering and reassembly structure.
+         */
+
+        /* Free first entry */
+        ssl_buffering_free_slot( ssl, 0 );
+
+        /* Shift all other entries */
+        for( offset = 0, hs_buf = &hs->buffering.hs[0];
+             offset + 1 < MBEDTLS_SSL_MAX_BUFFERED_HS;
+             offset++, hs_buf++ )
+        {
+            *hs_buf = *(hs_buf + 1);
+        }
+
+        /* Create a fresh last entry */
+        memset( hs_buf, 0, sizeof( mbedtls_ssl_hs_buffer ) );
     }
 #endif
 }
@@ -3822,7 +4133,16 @@
             }
             else
 #endif /* MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE && MBEDTLS_SSL_SRV_C */
+            {
+                /* Consider buffering the record. */
+                if( rec_epoch == (unsigned int) ssl->in_epoch + 1 )
+                {
+                    MBEDTLS_SSL_DEBUG_MSG( 2, ( "Consider record for buffering" ) );
+                    return( MBEDTLS_ERR_SSL_EARLY_MESSAGE );
+                }
+
                 return( MBEDTLS_ERR_SSL_UNEXPECTED_RECORD );
+            }
         }
 
 #if defined(MBEDTLS_SSL_DTLS_ANTI_REPLAY)
@@ -3835,15 +4155,6 @@
         }
 #endif
 
-        /* Drop unexpected ChangeCipherSpec messages */
-        if( ssl->in_msgtype == MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC &&
-            ssl->state != MBEDTLS_SSL_CLIENT_CHANGE_CIPHER_SPEC &&
-            ssl->state != MBEDTLS_SSL_SERVER_CHANGE_CIPHER_SPEC )
-        {
-            MBEDTLS_SSL_DEBUG_MSG( 1, ( "dropping unexpected ChangeCipherSpec" ) );
-            return( MBEDTLS_ERR_SSL_UNEXPECTED_RECORD );
-        }
-
         /* Drop unexpected ApplicationData records,
          * except at the beginning of renegotiations */
         if( ssl->in_msgtype == MBEDTLS_SSL_MSG_APPLICATION_DATA &&
@@ -3980,7 +4291,14 @@
  * RFC 6347 4.1.2.7) and continue reading until a valid record is found.
  *
  */
-int mbedtls_ssl_read_record( mbedtls_ssl_context *ssl )
+
+/* Helper functions for mbedtls_ssl_read_record(). */
+static int ssl_consume_current_message( mbedtls_ssl_context *ssl );
+static int ssl_get_next_record( mbedtls_ssl_context *ssl );
+static int ssl_record_is_in_progress( mbedtls_ssl_context *ssl );
+
+int mbedtls_ssl_read_record( mbedtls_ssl_context *ssl,
+                             unsigned update_hs_digest )
 {
     int ret;
 
@@ -3990,17 +4308,53 @@
     {
         do {
 
-            do ret = mbedtls_ssl_read_record_layer( ssl );
-            while( ret == MBEDTLS_ERR_SSL_CONTINUE_PROCESSING );
-
+            ret = ssl_consume_current_message( ssl );
             if( ret != 0 )
-            {
-                MBEDTLS_SSL_DEBUG_RET( 1, ( "mbedtls_ssl_read_record_layer" ), ret );
                 return( ret );
+
+            if( ssl_record_is_in_progress( ssl ) == 0 )
+            {
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+                int have_buffered = 0;
+
+                /* We only check for buffered messages if the
+                 * current datagram is fully consumed. */
+                if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+                    ssl_next_record_is_in_datagram( ssl ) == 0 )
+                {
+                    if( ssl_load_buffered_message( ssl ) == 0 )
+                        have_buffered = 1;
+                }
+
+                if( have_buffered == 0 )
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+                {
+                    ret = ssl_get_next_record( ssl );
+                    if( ret == MBEDTLS_ERR_SSL_CONTINUE_PROCESSING )
+                        continue;
+
+                    if( ret != 0 )
+                    {
+                        MBEDTLS_SSL_DEBUG_RET( 1, ( "ssl_get_next_record" ), ret );
+                        return( ret );
+                    }
+                }
             }
 
             ret = mbedtls_ssl_handle_message_type( ssl );
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+            if( ret == MBEDTLS_ERR_SSL_EARLY_MESSAGE )
+            {
+                /* Buffer future message */
+                ret = ssl_buffer_message( ssl );
+                if( ret != 0 )
+                    return( ret );
+
+                ret = MBEDTLS_ERR_SSL_CONTINUE_PROCESSING;
+            }
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
         } while( MBEDTLS_ERR_SSL_NON_FATAL           == ret  ||
                  MBEDTLS_ERR_SSL_CONTINUE_PROCESSING == ret );
 
@@ -4010,14 +4364,15 @@
             return( ret );
         }
 
-        if( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE )
+        if( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE &&
+            update_hs_digest == 1 )
         {
             mbedtls_ssl_update_handshake_status( ssl );
         }
     }
     else
     {
-        MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= reuse previously read message" ) );
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "reuse previously read message" ) );
         ssl->keep_current_message = 0;
     }
 
@@ -4026,13 +4381,350 @@
     return( 0 );
 }
 
-int mbedtls_ssl_read_record_layer( mbedtls_ssl_context *ssl )
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+static int ssl_next_record_is_in_datagram( mbedtls_ssl_context *ssl )
 {
-    int ret;
+    if( ssl->in_left > ssl->next_record_offset )
+        return( 1 );
 
+    return( 0 );
+}
+
+static int ssl_load_buffered_message( mbedtls_ssl_context *ssl )
+{
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+    mbedtls_ssl_hs_buffer * hs_buf;
+    int ret = 0;
+
+    if( hs == NULL )
+        return( -1 );
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> ssl_load_buffered_messsage" ) );
+
+    if( ssl->state == MBEDTLS_SSL_CLIENT_CHANGE_CIPHER_SPEC ||
+        ssl->state == MBEDTLS_SSL_SERVER_CHANGE_CIPHER_SPEC )
+    {
+        /* Check if we have seen a ChangeCipherSpec before.
+         * If yes, synthesize a CCS record. */
+        if( !hs->buffering.seen_ccs )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "CCS not seen in the current flight" ) );
+            ret = -1;
+            goto exit;
+        }
+
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Injecting buffered CCS message" ) );
+        ssl->in_msgtype = MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC;
+        ssl->in_msglen = 1;
+        ssl->in_msg[0] = 1;
+
+        /* As long as they are equal, the exact value doesn't matter. */
+        ssl->in_left            = 0;
+        ssl->next_record_offset = 0;
+
+        hs->buffering.seen_ccs = 0;
+        goto exit;
+    }
+
+#if defined(MBEDTLS_DEBUG_C)
+    /* Debug only */
+    {
+        unsigned offset;
+        for( offset = 1; offset < MBEDTLS_SSL_MAX_BUFFERED_HS; offset++ )
+        {
+            hs_buf = &hs->buffering.hs[offset];
+            if( hs_buf->is_valid == 1 )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 2, ( "Future message with sequence number %u %s buffered.",
+                            hs->in_msg_seq + offset,
+                            hs_buf->is_complete ? "fully" : "partially" ) );
+            }
+        }
+    }
+#endif /* MBEDTLS_DEBUG_C */
+
+    /* Check if we have buffered and/or fully reassembled the
+     * next handshake message. */
+    hs_buf = &hs->buffering.hs[0];
+    if( ( hs_buf->is_valid == 1 ) && ( hs_buf->is_complete == 1 ) )
+    {
+        /* Synthesize a record containing the buffered HS message. */
+        size_t msg_len = ( hs_buf->data[1] << 16 ) |
+                         ( hs_buf->data[2] << 8  ) |
+                           hs_buf->data[3];
+
+        /* Double-check that we haven't accidentally buffered
+         * a message that doesn't fit into the input buffer. */
+        if( msg_len + 12 > MBEDTLS_SSL_IN_CONTENT_LEN )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+            return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+        }
+
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Next handshake message has been buffered - load" ) );
+        MBEDTLS_SSL_DEBUG_BUF( 3, "Buffered handshake message (incl. header)",
+                               hs_buf->data, msg_len + 12 );
+
+        ssl->in_msgtype = MBEDTLS_SSL_MSG_HANDSHAKE;
+        ssl->in_hslen   = msg_len + 12;
+        ssl->in_msglen  = msg_len + 12;
+        memcpy( ssl->in_msg, hs_buf->data, ssl->in_hslen );
+
+        ret = 0;
+        goto exit;
+    }
+    else
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Next handshake message %u not or only partially bufffered",
+                                    hs->in_msg_seq ) );
+    }
+
+    ret = -1;
+
+exit:
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= ssl_load_buffered_message" ) );
+    return( ret );
+}
+
+static int ssl_buffer_make_space( mbedtls_ssl_context *ssl,
+                                  size_t desired )
+{
+    int offset;
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "Attempt to free buffered messages to have %u bytes available",
+                                (unsigned) desired ) );
+
+    /* Get rid of future records epoch first, if such exist. */
+    ssl_free_buffered_record( ssl );
+
+    /* Check if we have enough space available now. */
+    if( desired <= ( MBEDTLS_SSL_DTLS_MAX_BUFFERING -
+                     hs->buffering.total_bytes_buffered ) )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Enough space available after freeing future epoch record" ) );
+        return( 0 );
+    }
+
+    /* We don't have enough space to buffer the next expected handshake
+     * message. Remove buffers used for future messages to gain space,
+     * starting with the most distant one. */
+    for( offset = MBEDTLS_SSL_MAX_BUFFERED_HS - 1;
+         offset >= 0; offset-- )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Free buffering slot %d to make space for reassembly of next handshake message",
+                                    offset ) );
+
+        ssl_buffering_free_slot( ssl, (uint8_t) offset );
+
+        /* Check if we have enough space available now. */
+        if( desired <= ( MBEDTLS_SSL_DTLS_MAX_BUFFERING -
+                         hs->buffering.total_bytes_buffered ) )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "Enough space available after freeing buffered HS messages" ) );
+            return( 0 );
+        }
+    }
+
+    return( -1 );
+}
+
+static int ssl_buffer_message( mbedtls_ssl_context *ssl )
+{
+    int ret = 0;
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+
+    if( hs == NULL )
+        return( 0 );
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> ssl_buffer_message" ) );
+
+    switch( ssl->in_msgtype )
+    {
+        case MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC:
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "Remember CCS message" ) );
+
+            hs->buffering.seen_ccs = 1;
+            break;
+
+        case MBEDTLS_SSL_MSG_HANDSHAKE:
+        {
+            unsigned recv_msg_seq_offset;
+            unsigned recv_msg_seq = ( ssl->in_msg[4] << 8 ) | ssl->in_msg[5];
+            mbedtls_ssl_hs_buffer *hs_buf;
+            size_t msg_len = ssl->in_hslen - 12;
+
+            /* We should never receive an old handshake
+             * message - double-check nonetheless. */
+            if( recv_msg_seq < ssl->handshake->in_msg_seq )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+                return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+            }
+
+            recv_msg_seq_offset = recv_msg_seq - ssl->handshake->in_msg_seq;
+            if( recv_msg_seq_offset >= MBEDTLS_SSL_MAX_BUFFERED_HS )
+            {
+                /* Silently ignore -- message too far in the future */
+                MBEDTLS_SSL_DEBUG_MSG( 2,
+                 ( "Ignore future HS message with sequence number %u, "
+                   "buffering window %u - %u",
+                   recv_msg_seq, ssl->handshake->in_msg_seq,
+                   ssl->handshake->in_msg_seq + MBEDTLS_SSL_MAX_BUFFERED_HS - 1 ) );
+
+                goto exit;
+            }
+
+            MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffering HS message with sequence number %u, offset %u ",
+                                        recv_msg_seq, recv_msg_seq_offset ) );
+
+            hs_buf = &hs->buffering.hs[ recv_msg_seq_offset ];
+
+            /* Check if the buffering for this seq nr has already commenced. */
+            if( !hs_buf->is_valid )
+            {
+                size_t reassembly_buf_sz;
+
+                hs_buf->is_fragmented =
+                    ( ssl_hs_is_proper_fragment( ssl ) == 1 );
+
+                /* We copy the message back into the input buffer
+                 * after reassembly, so check that it's not too large.
+                 * This is an implementation-specific limitation
+                 * and not one from the standard, hence it is not
+                 * checked in ssl_check_hs_header(). */
+                if( msg_len + 12 > MBEDTLS_SSL_IN_CONTENT_LEN )
+                {
+                    /* Ignore message */
+                    goto exit;
+                }
+
+                /* Check if we have enough space to buffer the message. */
+                if( hs->buffering.total_bytes_buffered >
+                    MBEDTLS_SSL_DTLS_MAX_BUFFERING )
+                {
+                    MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+                    return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+                }
+
+                reassembly_buf_sz = ssl_get_reassembly_buffer_size( msg_len,
+                                                       hs_buf->is_fragmented );
+
+                if( reassembly_buf_sz > ( MBEDTLS_SSL_DTLS_MAX_BUFFERING -
+                                          hs->buffering.total_bytes_buffered ) )
+                {
+                    if( recv_msg_seq_offset > 0 )
+                    {
+                        /* If we can't buffer a future message because
+                         * of space limitations -- ignore. */
+                        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffering of future message of size %u would exceed the compile-time limit %u (already %u bytes buffered) -- ignore\n",
+                             (unsigned) msg_len, MBEDTLS_SSL_DTLS_MAX_BUFFERING,
+                             (unsigned) hs->buffering.total_bytes_buffered ) );
+                        goto exit;
+                    }
+                    else
+                    {
+                        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffering of future message of size %u would exceed the compile-time limit %u (already %u bytes buffered) -- attempt to make space by freeing buffered future messages\n",
+                             (unsigned) msg_len, MBEDTLS_SSL_DTLS_MAX_BUFFERING,
+                             (unsigned) hs->buffering.total_bytes_buffered ) );
+                    }
+
+                    if( ssl_buffer_make_space( ssl, reassembly_buf_sz ) != 0 )
+                    {
+                        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Reassembly of next message of size %u (%u with bitmap) would exceed the compile-time limit %u (already %u bytes buffered) -- fail\n",
+                             (unsigned) msg_len,
+                             (unsigned) reassembly_buf_sz,
+                             MBEDTLS_SSL_DTLS_MAX_BUFFERING,
+                             (unsigned) hs->buffering.total_bytes_buffered ) );
+                        ret = MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL;
+                        goto exit;
+                    }
+                }
+
+                MBEDTLS_SSL_DEBUG_MSG( 2, ( "initialize reassembly, total length = %d",
+                                            msg_len ) );
+
+                hs_buf->data = mbedtls_calloc( 1, reassembly_buf_sz );
+                if( hs_buf->data == NULL )
+                {
+                    ret = MBEDTLS_ERR_SSL_ALLOC_FAILED;
+                    goto exit;
+                }
+                hs_buf->data_len = reassembly_buf_sz;
+
+                /* Prepare final header: copy msg_type, length and message_seq,
+                 * then add standardised fragment_offset and fragment_length */
+                memcpy( hs_buf->data, ssl->in_msg, 6 );
+                memset( hs_buf->data + 6, 0, 3 );
+                memcpy( hs_buf->data + 9, hs_buf->data + 1, 3 );
+
+                hs_buf->is_valid = 1;
+
+                hs->buffering.total_bytes_buffered += reassembly_buf_sz;
+            }
+            else
+            {
+                /* Make sure msg_type and length are consistent */
+                if( memcmp( hs_buf->data, ssl->in_msg, 4 ) != 0 )
+                {
+                    MBEDTLS_SSL_DEBUG_MSG( 1, ( "Fragment header mismatch - ignore" ) );
+                    /* Ignore */
+                    goto exit;
+                }
+            }
+
+            if( !hs_buf->is_complete )
+            {
+                size_t frag_len, frag_off;
+                unsigned char * const msg = hs_buf->data + 12;
+
+                /*
+                 * Check and copy current fragment
+                 */
+
+                /* Validation of header fields already done in
+                 * mbedtls_ssl_prepare_handshake_record(). */
+                frag_off = ssl_get_hs_frag_off( ssl );
+                frag_len = ssl_get_hs_frag_len( ssl );
+
+                MBEDTLS_SSL_DEBUG_MSG( 2, ( "adding fragment, offset = %d, length = %d",
+                                            frag_off, frag_len ) );
+                memcpy( msg + frag_off, ssl->in_msg + 12, frag_len );
+
+                if( hs_buf->is_fragmented )
+                {
+                    unsigned char * const bitmask = msg + msg_len;
+                    ssl_bitmask_set( bitmask, frag_off, frag_len );
+                    hs_buf->is_complete = ( ssl_bitmask_check( bitmask,
+                                                               msg_len ) == 0 );
+                }
+                else
+                {
+                    hs_buf->is_complete = 1;
+                }
+
+                MBEDTLS_SSL_DEBUG_MSG( 2, ( "message %scomplete",
+                                   hs_buf->is_complete ? "" : "not yet " ) );
+            }
+
+            break;
+        }
+
+        default:
+            /* We don't buffer other types of messages. */
+            break;
+    }
+
+exit:
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= ssl_buffer_message" ) );
+    return( ret );
+}
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+static int ssl_consume_current_message( mbedtls_ssl_context *ssl )
+{
     /*
-     * Step A
-     *
      * Consume last content-layer message and potentially
      * update in_msglen which keeps track of the contents'
      * consumption state.
@@ -4114,20 +4806,161 @@
         ssl->in_msglen = 0;
     }
 
-    /*
-     * Step B
-     *
-     * Fetch and decode new record if current one is fully consumed.
-     *
-     */
+    return( 0 );
+}
 
+static int ssl_record_is_in_progress( mbedtls_ssl_context *ssl )
+{
     if( ssl->in_msglen > 0 )
+        return( 1 );
+
+    return( 0 );
+}
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+
+static void ssl_free_buffered_record( mbedtls_ssl_context *ssl )
+{
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+    if( hs == NULL )
+        return;
+
+    if( hs->buffering.future_record.data != NULL )
     {
-        /* There's something left to be processed in the current record. */
+        hs->buffering.total_bytes_buffered -=
+            hs->buffering.future_record.len;
+
+        mbedtls_free( hs->buffering.future_record.data );
+        hs->buffering.future_record.data = NULL;
+    }
+}
+
+static int ssl_load_buffered_record( mbedtls_ssl_context *ssl )
+{
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+    unsigned char * rec;
+    size_t rec_len;
+    unsigned rec_epoch;
+
+    if( ssl->conf->transport != MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+        return( 0 );
+
+    if( hs == NULL )
+        return( 0 );
+
+    rec       = hs->buffering.future_record.data;
+    rec_len   = hs->buffering.future_record.len;
+    rec_epoch = hs->buffering.future_record.epoch;
+
+    if( rec == NULL )
+        return( 0 );
+
+    /* Only consider loading future records if the
+     * input buffer is empty. */
+    if( ssl_next_record_is_in_datagram( ssl ) == 1 )
+        return( 0 );
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> ssl_load_buffered_record" ) );
+
+    if( rec_epoch != ssl->in_epoch )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffered record not from current epoch." ) );
+        goto exit;
+    }
+
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "Found buffered record from current epoch - load" ) );
+
+    /* Double-check that the record is not too large */
+    if( rec_len > MBEDTLS_SSL_IN_BUFFER_LEN -
+        (size_t)( ssl->in_hdr - ssl->in_buf ) )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    memcpy( ssl->in_hdr, rec, rec_len );
+    ssl->in_left = rec_len;
+    ssl->next_record_offset = 0;
+
+    ssl_free_buffered_record( ssl );
+
+exit:
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= ssl_load_buffered_record" ) );
+    return( 0 );
+}
+
+static int ssl_buffer_future_record( mbedtls_ssl_context *ssl )
+{
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+    size_t const rec_hdr_len = 13;
+    size_t const total_buf_sz = rec_hdr_len + ssl->in_msglen;
+
+    /* Don't buffer future records outside handshakes. */
+    if( hs == NULL )
+        return( 0 );
+
+    /* Only buffer handshake records (we are only interested
+     * in Finished messages). */
+    if( ssl->in_msgtype != MBEDTLS_SSL_MSG_HANDSHAKE )
+        return( 0 );
+
+    /* Don't buffer more than one future epoch record. */
+    if( hs->buffering.future_record.data != NULL )
+        return( 0 );
+
+    /* Don't buffer record if there's not enough buffering space remaining. */
+    if( total_buf_sz > ( MBEDTLS_SSL_DTLS_MAX_BUFFERING -
+                         hs->buffering.total_bytes_buffered ) )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffering of future epoch record of size %u would exceed the compile-time limit %u (already %u bytes buffered) -- ignore\n",
+                        (unsigned) total_buf_sz, MBEDTLS_SSL_DTLS_MAX_BUFFERING,
+                        (unsigned) hs->buffering.total_bytes_buffered ) );
         return( 0 );
     }
 
-    /* Current record either fully processed or to be discarded. */
+    /* Buffer record */
+    MBEDTLS_SSL_DEBUG_MSG( 2, ( "Buffer record from epoch %u",
+                                ssl->in_epoch + 1 ) );
+    MBEDTLS_SSL_DEBUG_BUF( 3, "Buffered record", ssl->in_hdr,
+                           rec_hdr_len + ssl->in_msglen );
+
+    /* ssl_parse_record_header() only considers records
+     * of the next epoch as candidates for buffering. */
+    hs->buffering.future_record.epoch = ssl->in_epoch + 1;
+    hs->buffering.future_record.len   = total_buf_sz;
+
+    hs->buffering.future_record.data =
+        mbedtls_calloc( 1, hs->buffering.future_record.len );
+    if( hs->buffering.future_record.data == NULL )
+    {
+        /* If we run out of RAM trying to buffer a
+         * record from the next epoch, just ignore. */
+        return( 0 );
+    }
+
+    memcpy( hs->buffering.future_record.data, ssl->in_hdr, total_buf_sz );
+
+    hs->buffering.total_bytes_buffered += total_buf_sz;
+    return( 0 );
+}
+
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+static int ssl_get_next_record( mbedtls_ssl_context *ssl )
+{
+    int ret;
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    /* We might have buffered a future record; if so,
+     * and if the epoch matches now, load it.
+     * On success, this call will set ssl->in_left to
+     * the length of the buffered record, so that
+     * the calls to ssl_fetch_input() below will
+     * essentially be no-ops. */
+    ret = ssl_load_buffered_record( ssl );
+    if( ret != 0 )
+        return( ret );
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
 
     if( ( ret = mbedtls_ssl_fetch_input( ssl, mbedtls_ssl_hdr_len( ssl ) ) ) != 0 )
     {
@@ -4141,6 +4974,16 @@
         if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
             ret != MBEDTLS_ERR_SSL_CLIENT_RECONNECT )
         {
+            if( ret == MBEDTLS_ERR_SSL_EARLY_MESSAGE )
+            {
+                ret = ssl_buffer_future_record( ssl );
+                if( ret != 0 )
+                    return( ret );
+
+                /* Fall through to handling of unexpected records */
+                ret = MBEDTLS_ERR_SSL_UNEXPECTED_RECORD;
+            }
+
             if( ret == MBEDTLS_ERR_SSL_UNEXPECTED_RECORD )
             {
                 /* Skip unexpected record (but not whole datagram) */
@@ -4272,6 +5115,39 @@
         }
     }
 
+    if( ssl->in_msgtype == MBEDTLS_SSL_MSG_CHANGE_CIPHER_SPEC )
+    {
+        if( ssl->in_msglen != 1 )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid CCS message, len: %d",
+                           ssl->in_msglen ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+
+        if( ssl->in_msg[0] != 1 )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid CCS message, content: %02x",
+                                        ssl->in_msg[0] ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+        if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+            ssl->state != MBEDTLS_SSL_CLIENT_CHANGE_CIPHER_SPEC    &&
+            ssl->state != MBEDTLS_SSL_SERVER_CHANGE_CIPHER_SPEC )
+        {
+            if( ssl->handshake == NULL )
+            {
+                MBEDTLS_SSL_DEBUG_MSG( 1, ( "dropping ChangeCipherSpec outside handshake" ) );
+                return( MBEDTLS_ERR_SSL_UNEXPECTED_RECORD );
+            }
+
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "received out-of-order ChangeCipherSpec - remember" ) );
+            return( MBEDTLS_ERR_SSL_EARLY_MESSAGE );
+        }
+#endif
+    }
+
     if( ssl->in_msgtype == MBEDTLS_SSL_MSG_ALERT )
     {
         if( ssl->in_msglen != 2 )
@@ -4373,7 +5249,7 @@
     ssl->out_msg[0] = level;
     ssl->out_msg[1] = message;
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_record( ssl, SSL_FORCE_FLUSH ) ) != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
         return( ret );
@@ -4542,9 +5418,9 @@
 
     ssl->state++;
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
@@ -4597,7 +5473,7 @@
     }
 #endif
 
-    if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
     {
         /* mbedtls_ssl_read_record may have sent an alert already. We
            let it decide whether to alert. */
@@ -4955,9 +5831,9 @@
 
     ssl->state++;
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
@@ -4972,7 +5848,7 @@
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse change cipher spec" ) );
 
-    if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret );
         return( ret );
@@ -4986,13 +5862,8 @@
         return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE );
     }
 
-    if( ssl->in_msglen != 1 || ssl->in_msg[0] != 1 )
-    {
-        MBEDTLS_SSL_DEBUG_MSG( 1, ( "bad change cipher spec message" ) );
-        mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
-                                        MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR );
-        return( MBEDTLS_ERR_SSL_BAD_HS_CHANGE_CIPHER_SPEC );
-    }
+    /* CCS records are only accepted if they have length 1 and content '1',
+     * so we don't need to check this here. */
 
     /*
      * Switch to our negotiated transform and session parameters for inbound
@@ -5022,16 +5893,7 @@
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
     memset( ssl->in_ctr, 0, 8 );
 
-    /*
-     * Set the in_msg pointer to the correct location based on IV length
-     */
-    if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
-    {
-        ssl->in_msg = ssl->in_iv + ssl->transform_negotiate->ivlen -
-                      ssl->transform_negotiate->fixed_ivlen;
-    }
-    else
-        ssl->in_msg = ssl->in_iv;
+    ssl_update_in_pointers( ssl, ssl->transform_negotiate );
 
 #if defined(MBEDTLS_SSL_HW_RECORD_ACCEL)
     if( mbedtls_ssl_hw_record_activate != NULL )
@@ -5482,16 +6344,7 @@
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write finished" ) );
 
-    /*
-     * Set the out_msg pointer to the correct location based on IV length
-     */
-    if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
-    {
-        ssl->out_msg = ssl->out_iv + ssl->transform_negotiate->ivlen -
-                       ssl->transform_negotiate->fixed_ivlen;
-    }
-    else
-        ssl->out_msg = ssl->out_iv;
+    ssl_update_out_pointers( ssl, ssl->transform_negotiate );
 
     ssl->handshake->calc_finished( ssl, ssl->out_msg + 4, ssl->conf->endpoint );
 
@@ -5543,14 +6396,14 @@
 
         /* Remember current epoch settings for resending */
         ssl->handshake->alt_transform_out = ssl->transform_out;
-        memcpy( ssl->handshake->alt_out_ctr, ssl->out_ctr, 8 );
+        memcpy( ssl->handshake->alt_out_ctr, ssl->cur_out_ctr, 8 );
 
         /* Set sequence_number to zero */
-        memset( ssl->out_ctr + 2, 0, 6 );
+        memset( ssl->cur_out_ctr + 2, 0, 6 );
 
         /* Increment epoch */
         for( i = 2; i > 0; i-- )
-            if( ++ssl->out_ctr[i - 1] != 0 )
+            if( ++ssl->cur_out_ctr[i - 1] != 0 )
                 break;
 
         /* The loop goes to its end iff the counter is wrapping */
@@ -5562,7 +6415,7 @@
     }
     else
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
-    memset( ssl->out_ctr, 0, 8 );
+    memset( ssl->cur_out_ctr, 0, 8 );
 
     ssl->transform_out = ssl->transform_negotiate;
     ssl->session_out = ssl->session_negotiate;
@@ -5583,12 +6436,21 @@
         mbedtls_ssl_send_flight_completed( ssl );
 #endif
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
+        ( ret = mbedtls_ssl_flight_transmit( ssl ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_flight_transmit", ret );
+        return( ret );
+    }
+#endif
+
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write finished" ) );
 
     return( 0 );
@@ -5610,7 +6472,7 @@
 
     ssl->handshake->calc_finished( ssl, buf, ssl->conf->endpoint ^ 1 );
 
-    if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
     {
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_read_record", ret );
         return( ret );
@@ -5841,6 +6703,78 @@
 }
 #endif /* MBEDTLS_SSL_DTLS_HELLO_VERIFY && MBEDTLS_SSL_SRV_C */
 
+/* Once ssl->out_hdr as the address of the beginning of the
+ * next outgoing record is set, deduce the other pointers.
+ *
+ * Note: For TLS, we save the implicit record sequence number
+ *       (entering MAC computation) in the 8 bytes before ssl->out_hdr,
+ *       and the caller has to make sure there's space for this.
+ */
+
+static void ssl_update_out_pointers( mbedtls_ssl_context *ssl,
+                                     mbedtls_ssl_transform *transform )
+{
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+    {
+        ssl->out_ctr = ssl->out_hdr +  3;
+        ssl->out_len = ssl->out_hdr + 11;
+        ssl->out_iv  = ssl->out_hdr + 13;
+    }
+    else
+#endif
+    {
+        ssl->out_ctr = ssl->out_hdr - 8;
+        ssl->out_len = ssl->out_hdr + 3;
+        ssl->out_iv  = ssl->out_hdr + 5;
+    }
+
+    /* Adjust out_msg to make space for explicit IV, if used. */
+    if( transform != NULL &&
+        ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
+    {
+        ssl->out_msg = ssl->out_iv + transform->ivlen - transform->fixed_ivlen;
+    }
+    else
+        ssl->out_msg = ssl->out_iv;
+}
+
+/* Once ssl->in_hdr as the address of the beginning of the
+ * next incoming record is set, deduce the other pointers.
+ *
+ * Note: For TLS, we save the implicit record sequence number
+ *       (entering MAC computation) in the 8 bytes before ssl->in_hdr,
+ *       and the caller has to make sure there's space for this.
+ */
+
+static void ssl_update_in_pointers( mbedtls_ssl_context *ssl,
+                                    mbedtls_ssl_transform *transform )
+{
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+    {
+        ssl->in_ctr = ssl->in_hdr +  3;
+        ssl->in_len = ssl->in_hdr + 11;
+        ssl->in_iv  = ssl->in_hdr + 13;
+    }
+    else
+#endif
+    {
+        ssl->in_ctr = ssl->in_hdr - 8;
+        ssl->in_len = ssl->in_hdr + 3;
+        ssl->in_iv  = ssl->in_hdr + 5;
+    }
+
+    /* Offset in_msg from in_iv to allow space for explicit IV, if used. */
+    if( transform != NULL &&
+        ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
+    {
+        ssl->in_msg = ssl->in_iv + transform->ivlen - transform->fixed_ivlen;
+    }
+    else
+        ssl->in_msg = ssl->in_iv;
+}
+
 /*
  * Initialize an SSL context
  */
@@ -5852,6 +6786,28 @@
 /*
  * Setup an SSL context
  */
+
+static void ssl_reset_in_out_pointers( mbedtls_ssl_context *ssl )
+{
+    /* Set the incoming and outgoing record pointers. */
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
+    {
+        ssl->out_hdr = ssl->out_buf;
+        ssl->in_hdr  = ssl->in_buf;
+    }
+    else
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+    {
+        ssl->out_hdr = ssl->out_buf + 8;
+        ssl->in_hdr  = ssl->in_buf  + 8;
+    }
+
+    /* Derive other internal pointers. */
+    ssl_update_out_pointers( ssl, NULL /* no transform enabled */ );
+    ssl_update_in_pointers ( ssl, NULL /* no transform enabled */ );
+}
+
 int mbedtls_ssl_setup( mbedtls_ssl_context *ssl,
                        const mbedtls_ssl_config *conf )
 {
@@ -5862,57 +6818,55 @@
     /*
      * Prepare base structures
      */
+
+    /* Set to NULL in case of an error condition */
+    ssl->out_buf = NULL;
+
     ssl->in_buf = mbedtls_calloc( 1, MBEDTLS_SSL_IN_BUFFER_LEN );
     if( ssl->in_buf == NULL )
     {
         MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc(%d bytes) failed", MBEDTLS_SSL_IN_BUFFER_LEN) );
-        return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
+        ret = MBEDTLS_ERR_SSL_ALLOC_FAILED;
+        goto error;
     }
 
     ssl->out_buf = mbedtls_calloc( 1, MBEDTLS_SSL_OUT_BUFFER_LEN );
     if( ssl->out_buf == NULL )
     {
         MBEDTLS_SSL_DEBUG_MSG( 1, ( "alloc(%d bytes) failed", MBEDTLS_SSL_OUT_BUFFER_LEN) );
-        mbedtls_free( ssl->in_buf );
-        ssl->in_buf = NULL;
-        return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
+        ret = MBEDTLS_ERR_SSL_ALLOC_FAILED;
+        goto error;
     }
 
-#if defined(MBEDTLS_SSL_PROTO_DTLS)
-    if( conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
-    {
-        ssl->out_hdr = ssl->out_buf;
-        ssl->out_ctr = ssl->out_buf +  3;
-        ssl->out_len = ssl->out_buf + 11;
-        ssl->out_iv  = ssl->out_buf + 13;
-        ssl->out_msg = ssl->out_buf + 13;
-
-        ssl->in_hdr = ssl->in_buf;
-        ssl->in_ctr = ssl->in_buf +  3;
-        ssl->in_len = ssl->in_buf + 11;
-        ssl->in_iv  = ssl->in_buf + 13;
-        ssl->in_msg = ssl->in_buf + 13;
-    }
-    else
-#endif
-    {
-        ssl->out_ctr = ssl->out_buf;
-        ssl->out_hdr = ssl->out_buf +  8;
-        ssl->out_len = ssl->out_buf + 11;
-        ssl->out_iv  = ssl->out_buf + 13;
-        ssl->out_msg = ssl->out_buf + 13;
-
-        ssl->in_ctr = ssl->in_buf;
-        ssl->in_hdr = ssl->in_buf +  8;
-        ssl->in_len = ssl->in_buf + 11;
-        ssl->in_iv  = ssl->in_buf + 13;
-        ssl->in_msg = ssl->in_buf + 13;
-    }
+    ssl_reset_in_out_pointers( ssl );
 
     if( ( ret = ssl_handshake_init( ssl ) ) != 0 )
-        return( ret );
+        goto error;
 
     return( 0 );
+
+error:
+    mbedtls_free( ssl->in_buf );
+    mbedtls_free( ssl->out_buf );
+
+    ssl->conf = NULL;
+
+    ssl->in_buf = NULL;
+    ssl->out_buf = NULL;
+
+    ssl->in_hdr = NULL;
+    ssl->in_ctr = NULL;
+    ssl->in_len = NULL;
+    ssl->in_iv = NULL;
+    ssl->in_msg = NULL;
+
+    ssl->out_hdr = NULL;
+    ssl->out_ctr = NULL;
+    ssl->out_len = NULL;
+    ssl->out_iv = NULL;
+    ssl->out_msg = NULL;
+
+    return( ret );
 }
 
 /*
@@ -5926,6 +6880,11 @@
 {
     int ret;
 
+#if !defined(MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE) ||     \
+    !defined(MBEDTLS_SSL_SRV_C)
+    ((void) partial);
+#endif
+
     ssl->state = MBEDTLS_SSL_HELLO_REQUEST;
 
     /* Cancel any possibly running timer */
@@ -5942,12 +6901,10 @@
     ssl->secure_renegotiation = MBEDTLS_SSL_LEGACY_RENEGOTIATION;
 
     ssl->in_offt = NULL;
+    ssl_reset_in_out_pointers( ssl );
 
-    ssl->in_msg = ssl->in_buf + 13;
     ssl->in_msgtype = 0;
     ssl->in_msglen = 0;
-    if( partial == 0 )
-        ssl->in_left = 0;
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
     ssl->next_record_offset = 0;
     ssl->in_epoch = 0;
@@ -5961,7 +6918,6 @@
 
     ssl->keep_current_message = 0;
 
-    ssl->out_msg = ssl->out_buf + 13;
     ssl->out_msgtype = 0;
     ssl->out_msglen = 0;
     ssl->out_left = 0;
@@ -5970,6 +6926,8 @@
         ssl->split_done = 0;
 #endif
 
+    memset( ssl->cur_out_ctr, 0, sizeof( ssl->cur_out_ctr ) );
+
     ssl->transform_in = NULL;
     ssl->transform_out = NULL;
 
@@ -5977,8 +6935,14 @@
     ssl->session_out = NULL;
 
     memset( ssl->out_buf, 0, MBEDTLS_SSL_OUT_BUFFER_LEN );
+
+#if defined(MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE) && defined(MBEDTLS_SSL_SRV_C)
     if( partial == 0 )
+#endif /* MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE && MBEDTLS_SSL_SRV_C */
+    {
+        ssl->in_left = 0;
         memset( ssl->in_buf, 0, MBEDTLS_SSL_IN_BUFFER_LEN );
+    }
 
 #if defined(MBEDTLS_SSL_HW_RECORD_ACCEL)
     if( mbedtls_ssl_hw_record_reset != NULL )
@@ -6011,7 +6975,9 @@
 #endif
 
 #if defined(MBEDTLS_SSL_DTLS_HELLO_VERIFY) && defined(MBEDTLS_SSL_SRV_C)
+#if defined(MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE)
     if( partial == 0 )
+#endif
     {
         mbedtls_free( ssl->cli_id );
         ssl->cli_id = NULL;
@@ -6062,7 +7028,15 @@
 #endif
 
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
-void mbedtls_ssl_conf_handshake_timeout( mbedtls_ssl_config *conf, uint32_t min, uint32_t max )
+
+void mbedtls_ssl_set_datagram_packing( mbedtls_ssl_context *ssl,
+                                       unsigned allow_packing )
+{
+    ssl->disable_datagram_packing = !allow_packing;
+}
+
+void mbedtls_ssl_conf_handshake_timeout( mbedtls_ssl_config *conf,
+                                         uint32_t min, uint32_t max )
 {
     conf->hs_timeout_min = min;
     conf->hs_timeout_max = max;
@@ -6112,6 +7086,13 @@
     ssl->f_recv_timeout = f_recv_timeout;
 }
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+void mbedtls_ssl_set_mtu( mbedtls_ssl_context *ssl, uint16_t mtu )
+{
+    ssl->mtu = mtu;
+}
+#endif
+
 void mbedtls_ssl_conf_read_timeout( mbedtls_ssl_config *conf, uint32_t timeout )
 {
     conf->read_timeout   = timeout;
@@ -6775,7 +7756,7 @@
 
     /*
      * In all other cases, the rest of the message can be dropped.
-     * As in ssl_read_record_layer, this needs to be adapted if
+     * As in ssl_get_next_record, this needs to be adapted if
      * we implement support for multiple alerts in single records.
      */
 
@@ -6842,8 +7823,9 @@
 
 int mbedtls_ssl_get_record_expansion( const mbedtls_ssl_context *ssl )
 {
-    size_t transform_expansion;
+    size_t transform_expansion = 0;
     const mbedtls_ssl_transform *transform = ssl->transform_out;
+    unsigned block_size;
 
     if( transform == NULL )
         return( (int) mbedtls_ssl_hdr_len( ssl ) );
@@ -6857,13 +7839,31 @@
     {
         case MBEDTLS_MODE_GCM:
         case MBEDTLS_MODE_CCM:
+        case MBEDTLS_MODE_CHACHAPOLY:
         case MBEDTLS_MODE_STREAM:
             transform_expansion = transform->minlen;
             break;
 
         case MBEDTLS_MODE_CBC:
-            transform_expansion = transform->maclen
-                      + mbedtls_cipher_get_block_size( &transform->cipher_ctx_enc );
+
+            block_size = mbedtls_cipher_get_block_size(
+                &transform->cipher_ctx_enc );
+
+            /* Expansion due to the addition of the MAC. */
+            transform_expansion += transform->maclen;
+
+            /* Expansion due to the addition of CBC padding;
+             * Theoretically up to 256 bytes, but we never use
+             * more than the block size of the underlying cipher. */
+            transform_expansion += block_size;
+
+            /* For TLS 1.1 or higher, an explicit IV is added
+             * after the record header. */
+#if defined(MBEDTLS_SSL_PROTO_TLS1_1) || defined(MBEDTLS_SSL_PROTO_TLS1_2)
+            if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_2 )
+                transform_expansion += block_size;
+#endif /* MBEDTLS_SSL_PROTO_TLS1_1 || MBEDTLS_SSL_PROTO_TLS1_2 */
+
             break;
 
         default:
@@ -6884,19 +7884,83 @@
      */
     max_len = ssl_mfl_code_to_length( ssl->conf->mfl_code );
 
-    /*
-     * Check if a smaller max length was negotiated
-     */
+    /* Check if a smaller max length was negotiated */
     if( ssl->session_out != NULL &&
         ssl_mfl_code_to_length( ssl->session_out->mfl_code ) < max_len )
     {
         max_len = ssl_mfl_code_to_length( ssl->session_out->mfl_code );
     }
 
-    return max_len;
+    /* During a handshake, use the value being negotiated */
+    if( ssl->session_negotiate != NULL &&
+        ssl_mfl_code_to_length( ssl->session_negotiate->mfl_code ) < max_len )
+    {
+        max_len = ssl_mfl_code_to_length( ssl->session_negotiate->mfl_code );
+    }
+
+    return( max_len );
 }
 #endif /* MBEDTLS_SSL_MAX_FRAGMENT_LENGTH */
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+static size_t ssl_get_current_mtu( const mbedtls_ssl_context *ssl )
+{
+    if( ssl->handshake == NULL || ssl->handshake->mtu == 0 )
+        return( ssl->mtu );
+
+    if( ssl->mtu == 0 )
+        return( ssl->handshake->mtu );
+
+    return( ssl->mtu < ssl->handshake->mtu ?
+            ssl->mtu : ssl->handshake->mtu );
+}
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+int mbedtls_ssl_get_max_out_record_payload( const mbedtls_ssl_context *ssl )
+{
+    size_t max_len = MBEDTLS_SSL_OUT_CONTENT_LEN;
+
+#if !defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH) && \
+    !defined(MBEDTLS_SSL_PROTO_DTLS)
+    (void) ssl;
+#endif
+
+#if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
+    const size_t mfl = mbedtls_ssl_get_max_frag_len( ssl );
+
+    if( max_len > mfl )
+        max_len = mfl;
+#endif
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( ssl_get_current_mtu( ssl ) != 0 )
+    {
+        const size_t mtu = ssl_get_current_mtu( ssl );
+        const int ret = mbedtls_ssl_get_record_expansion( ssl );
+        const size_t overhead = (size_t) ret;
+
+        if( ret < 0 )
+            return( ret );
+
+        if( mtu <= overhead )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "MTU too low for record expansion" ) );
+            return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );
+        }
+
+        if( max_len > mtu - overhead )
+            max_len = mtu - overhead;
+    }
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
+#if !defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH) &&        \
+    !defined(MBEDTLS_SSL_PROTO_DTLS)
+    ((void) ssl);
+#endif
+
+    return( (int) max_len );
+}
+
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
 const mbedtls_x509_crt *mbedtls_ssl_get_peer_cert( const mbedtls_ssl_context *ssl )
 {
@@ -6984,9 +8048,9 @@
     ssl->out_msgtype = MBEDTLS_SSL_MSG_HANDSHAKE;
     ssl->out_msg[0]  = MBEDTLS_SSL_HS_HELLO_REQUEST;
 
-    if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+    if( ( ret = mbedtls_ssl_write_handshake_msg( ssl ) ) != 0 )
     {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_handshake_msg", ret );
         return( ret );
     }
 
@@ -7116,7 +8180,7 @@
 
     in_ctr_cmp = memcmp( ssl->in_ctr + ep_len,
                         ssl->conf->renego_period + ep_len, 8 - ep_len );
-    out_ctr_cmp = memcmp( ssl->out_ctr + ep_len,
+    out_ctr_cmp = memcmp( ssl->cur_out_ctr + ep_len,
                           ssl->conf->renego_period + ep_len, 8 - ep_len );
 
     if( in_ctr_cmp <= 0 && out_ctr_cmp <= 0 )
@@ -7151,7 +8215,7 @@
         if( ssl->handshake != NULL &&
             ssl->handshake->retransmit_state == MBEDTLS_SSL_RETRANS_SENDING )
         {
-            if( ( ret = mbedtls_ssl_resend( ssl ) ) != 0 )
+            if( ( ret = mbedtls_ssl_flight_transmit( ssl ) ) != 0 )
                 return( ret );
         }
     }
@@ -7200,7 +8264,7 @@
             ssl_set_timer( ssl, ssl->conf->read_timeout );
         }
 
-        if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+        if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
         {
             if( ret == MBEDTLS_ERR_SSL_CONN_EOF )
                 return( 0 );
@@ -7215,7 +8279,7 @@
             /*
              * OpenSSL sends empty messages to randomize the IV
              */
-            if( ( ret = mbedtls_ssl_read_record( ssl ) ) != 0 )
+            if( ( ret = mbedtls_ssl_read_record( ssl, 1 ) ) != 0 )
             {
                 if( ret == MBEDTLS_ERR_SSL_CONN_EOF )
                     return( 0 );
@@ -7448,12 +8512,15 @@
 static int ssl_write_real( mbedtls_ssl_context *ssl,
                            const unsigned char *buf, size_t len )
 {
-    int ret;
-#if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
-    size_t max_len = mbedtls_ssl_get_max_frag_len( ssl );
-#else
-    size_t max_len = MBEDTLS_SSL_OUT_CONTENT_LEN;
-#endif /* MBEDTLS_SSL_MAX_FRAGMENT_LENGTH */
+    int ret = mbedtls_ssl_get_max_out_record_payload( ssl );
+    const size_t max_len = (size_t) ret;
+
+    if( ret < 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_get_max_out_record_payload", ret );
+        return( ret );
+    }
+
     if( len > max_len )
     {
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
@@ -7494,7 +8561,7 @@
         ssl->out_msgtype = MBEDTLS_SSL_MSG_APPLICATION_DATA;
         memcpy( ssl->out_msg, buf, len );
 
-        if( ( ret = mbedtls_ssl_write_record( ssl ) ) != 0 )
+        if( ( ret = mbedtls_ssl_write_record( ssl, SSL_FORCE_FLUSH ) ) != 0 )
         {
             MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_write_record", ret );
             return( ret );
@@ -7646,6 +8713,41 @@
 }
 #endif /* MBEDTLS_X509_CRT_PARSE_C */
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+
+static void ssl_buffering_free( mbedtls_ssl_context *ssl )
+{
+    unsigned offset;
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+
+    if( hs == NULL )
+        return;
+
+    ssl_free_buffered_record( ssl );
+
+    for( offset = 0; offset < MBEDTLS_SSL_MAX_BUFFERED_HS; offset++ )
+        ssl_buffering_free_slot( ssl, offset );
+}
+
+static void ssl_buffering_free_slot( mbedtls_ssl_context *ssl,
+                                     uint8_t slot )
+{
+    mbedtls_ssl_handshake_params * const hs = ssl->handshake;
+    mbedtls_ssl_hs_buffer * const hs_buf = &hs->buffering.hs[slot];
+
+    if( slot >= MBEDTLS_SSL_MAX_BUFFERED_HS )
+        return;
+
+    if( hs_buf->is_valid == 1 )
+    {
+        hs->buffering.total_bytes_buffered -= hs_buf->data_len;
+        mbedtls_free( hs_buf->data );
+        memset( hs_buf, 0, sizeof( mbedtls_ssl_hs_buffer ) );
+    }
+}
+
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+
 void mbedtls_ssl_handshake_free( mbedtls_ssl_context *ssl )
 {
     mbedtls_ssl_handshake_params *handshake = ssl->handshake;
@@ -7725,8 +8827,8 @@
 
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
     mbedtls_free( handshake->verify_cookie );
-    mbedtls_free( handshake->hs_msg );
     ssl_flight_free( handshake->flight );
+    ssl_buffering_free( ssl );
 #endif
 
     mbedtls_platform_zeroize( handshake,
diff --git a/library/threading.c b/library/threading.c
index 7a32e67..7c90c7c 100644
--- a/library/threading.c
+++ b/library/threading.c
@@ -19,6 +19,14 @@
  *  This file is part of mbed TLS (https://tls.mbed.org)
  */
 
+/*
+ * Ensure gmtime_r is available even with -std=c99; must be defined before
+ * config.h, which pulls in glibc's features.h. Harmless on other platforms.
+ */
+#if !defined(_POSIX_C_SOURCE)
+#define _POSIX_C_SOURCE 200112L
+#endif
+
 #if !defined(MBEDTLS_CONFIG_FILE)
 #include "mbedtls/config.h"
 #else
@@ -29,6 +37,36 @@
 
 #include "mbedtls/threading.h"
 
+#if defined(MBEDTLS_HAVE_TIME_DATE) && !defined(MBEDTLS_PLATFORM_GMTIME_R_ALT)
+
+#if !defined(_WIN32) && (defined(unix) || \
+    defined(__unix) || defined(__unix__) || (defined(__APPLE__) && \
+    defined(__MACH__)))
+#include <unistd.h>
+#endif /* !_WIN32 && (unix || __unix || __unix__ ||
+        * (__APPLE__ && __MACH__)) */
+
+#if !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) ||     \
+       ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) &&                     \
+         _POSIX_THREAD_SAFE_FUNCTIONS >= 20112L ) )
+/*
+ * This is a convenience shorthand macro to avoid checking the long
+ * preprocessor conditions above. Ideally, we could expose this macro in
+ * platform_util.h and simply use it in platform_util.c, threading.c and
+ * threading.h. However, this macro is not part of the Mbed TLS public API, so
+ * we keep it private by only defining it in this file
+ */
+
+#if ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) )
+#define THREADING_USE_GMTIME
+#endif /* ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) ) */
+
+#endif /* !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) ||     \
+             ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) &&                     \
+                _POSIX_THREAD_SAFE_FUNCTIONS >= 20112L ) ) */
+
+#endif /* MBEDTLS_HAVE_TIME_DATE && !MBEDTLS_PLATFORM_GMTIME_R_ALT */
+
 #if defined(MBEDTLS_THREADING_PTHREAD)
 static void threading_mutex_init_pthread( mbedtls_threading_mutex_t *mutex )
 {
@@ -114,6 +152,9 @@
 #if defined(MBEDTLS_FS_IO)
     mbedtls_mutex_init( &mbedtls_threading_readdir_mutex );
 #endif
+#if defined(THREADING_USE_GMTIME)
+    mbedtls_mutex_init( &mbedtls_threading_gmtime_mutex );
+#endif
 }
 
 /*
@@ -124,6 +165,9 @@
 #if defined(MBEDTLS_FS_IO)
     mbedtls_mutex_free( &mbedtls_threading_readdir_mutex );
 #endif
+#if defined(THREADING_USE_GMTIME)
+    mbedtls_mutex_free( &mbedtls_threading_gmtime_mutex );
+#endif
 }
 #endif /* MBEDTLS_THREADING_ALT */
 
@@ -136,5 +180,8 @@
 #if defined(MBEDTLS_FS_IO)
 mbedtls_threading_mutex_t mbedtls_threading_readdir_mutex MUTEX_INIT;
 #endif
+#if defined(THREADING_USE_GMTIME)
+mbedtls_threading_mutex_t mbedtls_threading_gmtime_mutex MUTEX_INIT;
+#endif
 
 #endif /* MBEDTLS_THREADING_C */
diff --git a/library/x509.c b/library/x509.c
index 2e6795f..52b5b64 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -29,10 +29,6 @@
  *  http://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf
  */
 
-/* Ensure gmtime_r is available even with -std=c99; must be included before
- * config.h, which pulls in glibc's features.h. Harmless on other platforms. */
-#define _POSIX_C_SOURCE 200112L
-
 #if !defined(MBEDTLS_CONFIG_FILE)
 #include "mbedtls/config.h"
 #else
@@ -67,6 +63,7 @@
 #include "mbedtls/platform_time.h"
 #endif
 #if defined(MBEDTLS_HAVE_TIME_DATE)
+#include "mbedtls/platform_util.h"
 #include <time.h>
 #endif
 
@@ -901,11 +898,7 @@
     int ret = 0;
 
     tt = mbedtls_time( NULL );
-#if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
-    lt = gmtime_s( &tm_buf, &tt ) == 0 ? &tm_buf : NULL;
-#else
-    lt = gmtime_r( &tt, &tm_buf );
-#endif
+    lt = mbedtls_platform_gmtime_r( &tt, &tm_buf );
 
     if( lt == NULL )
         ret = -1;
diff --git a/library/x509_crt.c b/library/x509_crt.c
index 290c1eb..a390f81 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -163,6 +163,9 @@
 static int x509_profile_check_md_alg( const mbedtls_x509_crt_profile *profile,
                                       mbedtls_md_type_t md_alg )
 {
+    if( md_alg == MBEDTLS_MD_NONE )
+        return( -1 );
+
     if( ( profile->allowed_mds & MBEDTLS_X509_ID_FLAG( md_alg ) ) != 0 )
         return( 0 );
 
@@ -176,6 +179,9 @@
 static int x509_profile_check_pk_alg( const mbedtls_x509_crt_profile *profile,
                                       mbedtls_pk_type_t pk_alg )
 {
+    if( pk_alg == MBEDTLS_PK_NONE )
+        return( -1 );
+
     if( ( profile->allowed_pks & MBEDTLS_X509_ID_FLAG( pk_alg ) ) != 0 )
         return( 0 );
 
@@ -208,6 +214,9 @@
     {
         const mbedtls_ecp_group_id gid = mbedtls_pk_ec( *pk )->grp.id;
 
+        if( gid == MBEDTLS_ECP_DP_NONE )
+            return( -1 );
+
         if( ( profile->allowed_curves & MBEDTLS_X509_ID_FLAG( gid ) ) != 0 )
             return( 0 );
 
@@ -570,18 +579,14 @@
         end_ext_data = *p + len;
 
         /* Get extension ID */
-        extn_oid.tag = **p;
-
-        if( ( ret = mbedtls_asn1_get_tag( p, end, &extn_oid.len, MBEDTLS_ASN1_OID ) ) != 0 )
+        if( ( ret = mbedtls_asn1_get_tag( p, end_ext_data, &extn_oid.len,
+                                          MBEDTLS_ASN1_OID ) ) != 0 )
             return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS + ret );
 
+        extn_oid.tag = MBEDTLS_ASN1_OID;
         extn_oid.p = *p;
         *p += extn_oid.len;
 
-        if( ( end - *p ) < 1 )
-            return( MBEDTLS_ERR_X509_INVALID_EXTENSIONS +
-                    MBEDTLS_ERR_ASN1_OUT_OF_DATA );
-
         /* Get optional critical */
         if( ( ret = mbedtls_asn1_get_bool( p, end_ext_data, &is_critical ) ) != 0 &&
             ( ret != MBEDTLS_ERR_ASN1_UNEXPECTED_TAG ) )
diff --git a/programs/pkey/pk_decrypt.c b/programs/pkey/pk_decrypt.c
index 00bd71e..1d8c959 100644
--- a/programs/pkey/pk_decrypt.c
+++ b/programs/pkey/pk_decrypt.c
@@ -73,7 +73,10 @@
     const char *pers = "mbedtls_pk_decrypt";
     ((void) argv);
 
+    mbedtls_pk_init( &pk );
+    mbedtls_entropy_init( &entropy );
     mbedtls_ctr_drbg_init( &ctr_drbg );
+
     memset(result, 0, sizeof( result ) );
 
     if( argc != 2 )
@@ -90,20 +93,18 @@
     mbedtls_printf( "\n  . Seeding the random number generator..." );
     fflush( stdout );
 
-    mbedtls_entropy_init( &entropy );
-    if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
-                               (const unsigned char *) pers,
-                               strlen( pers ) ) ) != 0 )
+    if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func,
+                                       &entropy, (const unsigned char *) pers,
+                                       strlen( pers ) ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned %d\n", ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%04x\n",
+                        -ret );
         goto exit;
     }
 
     mbedtls_printf( "\n  . Reading private key from '%s'", argv[1] );
     fflush( stdout );
 
-    mbedtls_pk_init( &pk );
-
     if( ( ret = mbedtls_pk_parse_keyfile( &pk, argv[1], "" ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_pk_parse_keyfile returned -0x%04x\n", -ret );
@@ -116,14 +117,16 @@
     if( ( f = fopen( "result-enc.txt", "rb" ) ) == NULL )
     {
         mbedtls_printf( "\n  ! Could not open %s\n\n", "result-enc.txt" );
+        ret = 1;
         goto exit;
     }
 
     i = 0;
-
     while( fscanf( f, "%02X", &c ) > 0 &&
            i < (int) sizeof( buf ) )
+    {
         buf[i++] = (unsigned char) c;
+    }
 
     fclose( f );
 
@@ -136,7 +139,8 @@
     if( ( ret = mbedtls_pk_decrypt( &pk, buf, i, result, &olen, sizeof(result),
                             mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_pk_decrypt returned -0x%04x\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_pk_decrypt returned -0x%04x\n",
+                        -ret );
         goto exit;
     }
 
@@ -147,13 +151,15 @@
     exit_code = MBEDTLS_EXIT_SUCCESS;
 
 exit:
-    mbedtls_ctr_drbg_free( &ctr_drbg );
+
+    mbedtls_pk_free( &pk );
     mbedtls_entropy_free( &entropy );
+    mbedtls_ctr_drbg_free( &ctr_drbg );
 
 #if defined(MBEDTLS_ERROR_C)
     if( exit_code != MBEDTLS_EXIT_SUCCESS )
     {
-        mbedtls_strerror( ret, (char *) buf, sizeof(buf) );
+        mbedtls_strerror( ret, (char *) buf, sizeof( buf ) );
         mbedtls_printf( "  !  Last error was: %s\n", buf );
     }
 #endif
diff --git a/programs/pkey/pk_encrypt.c b/programs/pkey/pk_encrypt.c
index 400619c..22dedba 100644
--- a/programs/pkey/pk_encrypt.c
+++ b/programs/pkey/pk_encrypt.c
@@ -73,6 +73,8 @@
     const char *pers = "mbedtls_pk_encrypt";
 
     mbedtls_ctr_drbg_init( &ctr_drbg );
+    mbedtls_entropy_init( &entropy );
+    mbedtls_pk_init( &pk );
 
     if( argc != 3 )
     {
@@ -88,20 +90,18 @@
     mbedtls_printf( "\n  . Seeding the random number generator..." );
     fflush( stdout );
 
-    mbedtls_entropy_init( &entropy );
-    if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
-                               (const unsigned char *) pers,
-                               strlen( pers ) ) ) != 0 )
+    if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func,
+                                       &entropy, (const unsigned char *) pers,
+                                       strlen( pers ) ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%04x\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned -0x%04x\n",
+                        -ret );
         goto exit;
     }
 
     mbedtls_printf( "\n  . Reading public key from '%s'", argv[1] );
     fflush( stdout );
 
-    mbedtls_pk_init( &pk );
-
     if( ( ret = mbedtls_pk_parse_public_keyfile( &pk, argv[1] ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_pk_parse_public_keyfile returned -0x%04x\n", -ret );
@@ -126,7 +126,8 @@
                             buf, &olen, sizeof(buf),
                             mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
     {
-        mbedtls_printf( " failed\n  ! mbedtls_pk_encrypt returned -0x%04x\n", -ret );
+        mbedtls_printf( " failed\n  ! mbedtls_pk_encrypt returned -0x%04x\n",
+                        -ret );
         goto exit;
     }
 
@@ -135,13 +136,17 @@
      */
     if( ( f = fopen( "result-enc.txt", "wb+" ) ) == NULL )
     {
-        mbedtls_printf( " failed\n  ! Could not create %s\n\n", "result-enc.txt" );
+        mbedtls_printf( " failed\n  ! Could not create %s\n\n",
+                        "result-enc.txt" );
+        ret = 1;
         goto exit;
     }
 
     for( i = 0; i < olen; i++ )
+    {
         mbedtls_fprintf( f, "%02X%s", buf[i],
                  ( i + 1 ) % 16 == 0 ? "\r\n" : " " );
+    }
 
     fclose( f );
 
@@ -150,13 +155,15 @@
     exit_code = MBEDTLS_EXIT_SUCCESS;
 
 exit:
-    mbedtls_ctr_drbg_free( &ctr_drbg );
+
+    mbedtls_pk_free( &pk );
     mbedtls_entropy_free( &entropy );
+    mbedtls_ctr_drbg_free( &ctr_drbg );
 
 #if defined(MBEDTLS_ERROR_C)
     if( exit_code != MBEDTLS_EXIT_SUCCESS )
     {
-        mbedtls_strerror( ret, (char *) buf, sizeof(buf) );
+        mbedtls_strerror( ret, (char *) buf, sizeof( buf ) );
         mbedtls_printf( "  !  Last error was: %s\n", buf );
     }
 #endif
diff --git a/programs/ssl/ssl_client2.c b/programs/ssl/ssl_client2.c
index 0dd9e3f..efd2b30 100644
--- a/programs/ssl/ssl_client2.c
+++ b/programs/ssl/ssl_client2.c
@@ -106,6 +106,8 @@
 #define DFL_TRANSPORT           MBEDTLS_SSL_TRANSPORT_STREAM
 #define DFL_HS_TO_MIN           0
 #define DFL_HS_TO_MAX           0
+#define DFL_DTLS_MTU            -1
+#define DFL_DGRAM_PACKING        1
 #define DFL_FALLBACK            -1
 #define DFL_EXTENDED_MS         -1
 #define DFL_ETM                 -1
@@ -198,7 +200,11 @@
 #define USAGE_DTLS \
     "    dtls=%%d             default: 0 (TLS)\n"                           \
     "    hs_timeout=%%d-%%d    default: (library default: 1000-60000)\n"    \
-    "                        range of DTLS handshake timeouts in millisecs\n"
+    "                        range of DTLS handshake timeouts in millisecs\n" \
+    "    mtu=%%d              default: (library default: unlimited)\n"  \
+    "    dgram_packing=%%d    default: 1 (allowed)\n"                   \
+    "                        allow or forbid packing of multiple\n" \
+    "                        records within a single datgram.\n"
 #else
 #define USAGE_DTLS ""
 #endif
@@ -345,7 +351,9 @@
     int transport;              /* TLS or DTLS?                             */
     uint32_t hs_to_min;         /* Initial value of DTLS handshake timer    */
     uint32_t hs_to_max;         /* Max value of DTLS handshake timer        */
+    int dtls_mtu;               /* UDP Maximum tranport unit for DTLS       */
     int fallback;               /* is this a fallback connection?           */
+    int dgram_packing;          /* allow/forbid datagram packing            */
     int extended_ms;            /* negotiate extended master secret?        */
     int etm;                    /* negotiate encrypt then mac?              */
 } opt;
@@ -617,9 +625,11 @@
     opt.transport           = DFL_TRANSPORT;
     opt.hs_to_min           = DFL_HS_TO_MIN;
     opt.hs_to_max           = DFL_HS_TO_MAX;
+    opt.dtls_mtu            = DFL_DTLS_MTU;
     opt.fallback            = DFL_FALLBACK;
     opt.extended_ms         = DFL_EXTENDED_MS;
     opt.etm                 = DFL_ETM;
+    opt.dgram_packing       = DFL_DGRAM_PACKING;
 
     for( i = 1; i < argc; i++ )
     {
@@ -927,6 +937,21 @@
             if( opt.hs_to_min == 0 || opt.hs_to_max < opt.hs_to_min )
                 goto usage;
         }
+        else if( strcmp( p, "mtu" ) == 0 )
+        {
+            opt.dtls_mtu = atoi( q );
+            if( opt.dtls_mtu < 0 )
+                goto usage;
+        }
+        else if( strcmp( p, "dgram_packing" ) == 0 )
+        {
+            opt.dgram_packing = atoi( q );
+            if( opt.dgram_packing != 0 &&
+                opt.dgram_packing != 1 )
+            {
+                goto usage;
+            }
+        }
         else if( strcmp( p, "recsplit" ) == 0 )
         {
             opt.recsplit = atoi( q );
@@ -1327,6 +1352,9 @@
     if( opt.hs_to_min != DFL_HS_TO_MIN || opt.hs_to_max != DFL_HS_TO_MAX )
         mbedtls_ssl_conf_handshake_timeout( &conf, opt.hs_to_min,
                                             opt.hs_to_max );
+
+    if( opt.dgram_packing != DFL_DGRAM_PACKING )
+        mbedtls_ssl_set_datagram_packing( &ssl, opt.dgram_packing );
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
 #if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
@@ -1485,6 +1513,11 @@
                              mbedtls_net_send, mbedtls_net_recv,
                              opt.nbio == 0 ? mbedtls_net_recv_timeout : NULL );
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( opt.dtls_mtu != DFL_DTLS_MTU )
+        mbedtls_ssl_set_mtu( &ssl, opt.dtls_mtu );
+#endif
+
 #if defined(MBEDTLS_TIMING_C)
     mbedtls_ssl_set_timer_cb( &ssl, &timer, mbedtls_timing_set_delay,
                                             mbedtls_timing_get_delay );
diff --git a/programs/ssl/ssl_server2.c b/programs/ssl/ssl_server2.c
index 7654a64..070c005 100644
--- a/programs/ssl/ssl_server2.c
+++ b/programs/ssl/ssl_server2.c
@@ -150,7 +150,9 @@
 #define DFL_ANTI_REPLAY         -1
 #define DFL_HS_TO_MIN           0
 #define DFL_HS_TO_MAX           0
+#define DFL_DTLS_MTU            -1
 #define DFL_BADMAC_LIMIT        -1
+#define DFL_DGRAM_PACKING        1
 #define DFL_EXTENDED_MS         -1
 #define DFL_ETM                 -1
 
@@ -297,7 +299,11 @@
 #define USAGE_DTLS \
     "    dtls=%%d             default: 0 (TLS)\n"                           \
     "    hs_timeout=%%d-%%d    default: (library default: 1000-60000)\n"    \
-    "                        range of DTLS handshake timeouts in millisecs\n"
+    "                        range of DTLS handshake timeouts in millisecs\n" \
+    "    mtu=%%d              default: (library default: unlimited)\n"  \
+    "    dgram_packing=%%d    default: 1 (allowed)\n"                   \
+    "                        allow or forbid packing of multiple\n" \
+    "                        records within a single datgram.\n"
 #else
 #define USAGE_DTLS ""
 #endif
@@ -470,6 +476,8 @@
     int anti_replay;            /* Use anti-replay for DTLS? -1 for default */
     uint32_t hs_to_min;         /* Initial value of DTLS handshake timer    */
     uint32_t hs_to_max;         /* Max value of DTLS handshake timer        */
+    int dtls_mtu;               /* UDP Maximum tranport unit for DTLS       */
+    int dgram_packing;          /* allow/forbid datagram packing            */
     int badmac_limit;           /* Limit of records with bad MAC            */
 } opt;
 
@@ -1338,6 +1346,8 @@
     opt.anti_replay         = DFL_ANTI_REPLAY;
     opt.hs_to_min           = DFL_HS_TO_MIN;
     opt.hs_to_max           = DFL_HS_TO_MAX;
+    opt.dtls_mtu            = DFL_DTLS_MTU;
+    opt.dgram_packing       = DFL_DGRAM_PACKING;
     opt.badmac_limit        = DFL_BADMAC_LIMIT;
     opt.extended_ms         = DFL_EXTENDED_MS;
     opt.etm                 = DFL_ETM;
@@ -1684,6 +1694,21 @@
             if( opt.hs_to_min == 0 || opt.hs_to_max < opt.hs_to_min )
                 goto usage;
         }
+        else if( strcmp( p, "mtu" ) == 0 )
+        {
+            opt.dtls_mtu = atoi( q );
+            if( opt.dtls_mtu < 0 )
+                goto usage;
+        }
+        else if( strcmp( p, "dgram_packing" ) == 0 )
+        {
+            opt.dgram_packing = atoi( q );
+            if( opt.dgram_packing != 0 &&
+                opt.dgram_packing != 1 )
+            {
+                goto usage;
+            }
+        }
         else if( strcmp( p, "sni" ) == 0 )
         {
             opt.sni = q;
@@ -2155,6 +2180,9 @@
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
     if( opt.hs_to_min != DFL_HS_TO_MIN || opt.hs_to_max != DFL_HS_TO_MAX )
         mbedtls_ssl_conf_handshake_timeout( &conf, opt.hs_to_min, opt.hs_to_max );
+
+    if( opt.dgram_packing != DFL_DGRAM_PACKING )
+        mbedtls_ssl_set_datagram_packing( &ssl, opt.dgram_packing );
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
 #if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
@@ -2473,6 +2501,11 @@
         mbedtls_ssl_set_bio( &ssl, &client_fd, mbedtls_net_send, mbedtls_net_recv,
                              opt.nbio == 0 ? mbedtls_net_recv_timeout : NULL );
 
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( opt.dtls_mtu != DFL_DTLS_MTU )
+        mbedtls_ssl_set_mtu( &ssl, opt.dtls_mtu );
+#endif
+
 #if defined(MBEDTLS_TIMING_C)
     mbedtls_ssl_set_timer_cb( &ssl, &timer, mbedtls_timing_set_delay,
                                             mbedtls_timing_get_delay );
diff --git a/programs/test/udp_proxy.c b/programs/test/udp_proxy.c
index 55e0f24..41739d0 100644
--- a/programs/test/udp_proxy.c
+++ b/programs/test/udp_proxy.c
@@ -40,6 +40,8 @@
 #define mbedtls_time            time
 #define mbedtls_time_t          time_t
 #define mbedtls_printf          printf
+#define mbedtls_calloc          calloc
+#define mbedtls_free            free
 #define MBEDTLS_EXIT_SUCCESS    EXIT_SUCCESS
 #define MBEDTLS_EXIT_FAILURE    EXIT_FAILURE
 #endif /* MBEDTLS_PLATFORM_C */
@@ -106,6 +108,21 @@
     "    delay=%%d            default: 0 (no delayed packets)\n"            \
     "                        delay about 1:N packets randomly\n"            \
     "    delay_ccs=0/1       default: 0 (don't delay ChangeCipherSpec)\n"   \
+    "    delay_cli=%%s        Handshake message from client that should be\n"\
+    "                        delayed. Possible values are 'ClientHello',\n" \
+    "                        'Certificate', 'CertificateVerify', and\n"     \
+    "                        'ClientKeyExchange'.\n"                        \
+    "                        May be used multiple times, even for the same\n"\
+    "                        message, in which case the respective message\n"\
+    "                        gets delayed multiple times.\n"                 \
+    "    delay_srv=%%s        Handshake message from server that should be\n"\
+    "                        delayed. Possible values are 'HelloRequest',\n"\
+    "                        'ServerHello', 'ServerHelloDone', 'Certificate'\n"\
+    "                        'ServerKeyExchange', 'NewSessionTicket',\n"\
+    "                        'HelloVerifyRequest' and ''CertificateRequest'.\n"\
+    "                        May be used multiple times, even for the same\n"\
+    "                        message, in which case the respective message\n"\
+    "                        gets delayed multiple times.\n"                 \
     "    drop=%%d             default: 0 (no dropped packets)\n"            \
     "                        drop about 1:N packets randomly\n"             \
     "    mtu=%%d              default: 0 (unlimited)\n"                     \
@@ -121,6 +138,9 @@
 /*
  * global options
  */
+
+#define MAX_DELAYED_HS 10
+
 static struct options
 {
     const char *server_addr;    /* address to forward packets to            */
@@ -131,6 +151,12 @@
     int duplicate;              /* duplicate 1 in N packets (none if 0)     */
     int delay;                  /* delay 1 packet in N (none if 0)          */
     int delay_ccs;              /* delay ChangeCipherSpec                   */
+    char* delay_cli[MAX_DELAYED_HS];  /* handshake types of messages from
+                                       * client that should be delayed.     */
+    uint8_t delay_cli_cnt;      /* Number of entries in delay_cli.          */
+    char* delay_srv[MAX_DELAYED_HS];  /* handshake types of messages from
+                                       * server that should be delayed.     */
+    uint8_t delay_srv_cnt;      /* Number of entries in delay_srv.          */
     int drop;                   /* drop 1 packet in N (none if 0)           */
     int mtu;                    /* drop packets larger than this            */
     int bad_ad;                 /* inject corrupted ApplicationData record  */
@@ -164,6 +190,11 @@
     opt.pack           = DFL_PACK;
     /* Other members default to 0 */
 
+    opt.delay_cli_cnt = 0;
+    opt.delay_srv_cnt = 0;
+    memset( opt.delay_cli, 0, sizeof( opt.delay_cli ) );
+    memset( opt.delay_srv, 0, sizeof( opt.delay_srv ) );
+
     for( i = 1; i < argc; i++ )
     {
         p = argv[i];
@@ -197,6 +228,43 @@
             if( opt.delay_ccs < 0 || opt.delay_ccs > 1 )
                 exit_usage( p, q );
         }
+        else if( strcmp( p, "delay_cli" ) == 0 ||
+                 strcmp( p, "delay_srv" ) == 0 )
+        {
+            uint8_t *delay_cnt;
+            char **delay_list;
+            size_t len;
+            char *buf;
+
+            if( strcmp( p, "delay_cli" ) == 0 )
+            {
+                delay_cnt  = &opt.delay_cli_cnt;
+                delay_list = opt.delay_cli;
+            }
+            else
+            {
+                delay_cnt  = &opt.delay_srv_cnt;
+                delay_list = opt.delay_srv;
+            }
+
+            if( *delay_cnt == MAX_DELAYED_HS )
+            {
+                mbedtls_printf( " too many uses of %s: only %d allowed\n",
+                                p, MAX_DELAYED_HS );
+                exit_usage( p, NULL );
+            }
+
+            len = strlen( q );
+            buf = mbedtls_calloc( 1, len + 1 );
+            if( buf == NULL )
+            {
+                mbedtls_printf( " Allocation failure\n" );
+                exit( 1 );
+            }
+            memcpy( buf, q, len + 1 );
+
+            delay_list[ (*delay_cnt)++ ] = buf;
+        }
         else if( strcmp( p, "drop" ) == 0 )
         {
             opt.drop = atoi( q );
@@ -488,11 +556,37 @@
     return( 0 );
 }
 
-static packet prev;
+#define MAX_DELAYED_MSG 5
+static size_t prev_len;
+static packet prev[MAX_DELAYED_MSG];
 
 void clear_pending( void )
 {
-    memset( &prev, 0, sizeof( packet ) );
+    memset( &prev, 0, sizeof( prev ) );
+    prev_len = 0;
+}
+
+void delay_packet( packet *delay )
+{
+    if( prev_len == MAX_DELAYED_MSG )
+        return;
+
+    memcpy( &prev[prev_len++], delay, sizeof( packet ) );
+}
+
+int send_delayed()
+{
+    uint8_t offset;
+    int ret;
+    for( offset = 0; offset < prev_len; offset++ )
+    {
+        ret = send_packet( &prev[offset], "delayed" );
+        if( ret != 0 )
+            return( ret );
+    }
+
+    clear_pending();
+    return( 0 );
 }
 
 /*
@@ -540,6 +634,10 @@
     packet cur;
     size_t id;
 
+    uint8_t delay_idx;
+    char ** delay_list;
+    uint8_t delay_list_len;
+
     /* receive packet */
     if( ( ret = mbedtls_net_recv( src, cur.buf, sizeof( cur.buf ) ) ) <= 0 )
     {
@@ -555,6 +653,37 @@
 
     id = cur.len % sizeof( dropped );
 
+    if( strcmp( way, "S <- C" ) == 0 )
+    {
+        delay_list     = opt.delay_cli;
+        delay_list_len = opt.delay_cli_cnt;
+    }
+    else
+    {
+        delay_list     = opt.delay_srv;
+        delay_list_len = opt.delay_srv_cnt;
+    }
+
+    /* Check if message type is in the list of messages
+     * that should be delayed */
+    for( delay_idx = 0; delay_idx < delay_list_len; delay_idx++ )
+    {
+        if( delay_list[ delay_idx ] == NULL )
+            continue;
+
+        if( strcmp( delay_list[ delay_idx ], cur.type ) == 0 )
+        {
+            /* Delay message */
+            delay_packet( &cur );
+
+            /* Remove entry from list */
+            mbedtls_free( delay_list[delay_idx] );
+            delay_list[delay_idx] = NULL;
+
+            return( 0 );
+        }
+    }
+
     /* do we want to drop, delay, or forward it? */
     if( ( opt.mtu != 0 &&
           cur.len > (unsigned) opt.mtu ) ||
@@ -574,12 +703,11 @@
                strcmp( cur.type, "ApplicationData" ) != 0 &&
                ! ( opt.protect_hvr &&
                    strcmp( cur.type, "HelloVerifyRequest" ) == 0 ) &&
-               prev.dst == NULL &&
                cur.len != (size_t) opt.protect_len &&
                dropped[id] < DROP_MAX &&
                rand() % opt.delay == 0 ) )
     {
-        memcpy( &prev, &cur, sizeof( packet ) );
+        delay_packet( &cur );
     }
     else
     {
@@ -587,14 +715,10 @@
         if( ( ret = send_packet( &cur, "forwarded" ) ) != 0 )
             return( ret );
 
-        /* send previously delayed message if any */
-        if( prev.dst != NULL )
-        {
-            ret = send_packet( &prev, "delayed" );
-            memset( &prev, 0, sizeof( packet ) );
-            if( ret != 0 )
-                return( ret );
-        }
+        /* send previously delayed messages if any */
+        ret = send_delayed();
+        if( ret != 0 )
+            return( ret );
     }
 
     return( 0 );
@@ -604,6 +728,7 @@
 {
     int ret = 1;
     int exit_code = MBEDTLS_EXIT_FAILURE;
+    uint8_t delay_idx;
 
     mbedtls_net_context listen_fd, client_fd, server_fd;
 
@@ -798,6 +923,12 @@
     }
 #endif
 
+    for( delay_idx = 0; delay_idx < MAX_DELAYED_HS; delay_idx++ )
+    {
+        mbedtls_free( opt.delay_cli + delay_idx );
+        mbedtls_free( opt.delay_srv + delay_idx );
+    }
+
     mbedtls_net_free( &client_fd );
     mbedtls_net_free( &server_fd );
     mbedtls_net_free( &listen_fd );
diff --git a/programs/x509/cert_write.c b/programs/x509/cert_write.c
index 09a91e0..fa99461 100644
--- a/programs/x509/cert_write.c
+++ b/programs/x509/cert_write.c
@@ -164,7 +164,7 @@
     const char *issuer_key;     /* filename of the issuer key file      */
     const char *subject_pwd;    /* password for the subject key file    */
     const char *issuer_pwd;     /* password for the issuer key file     */
-    const char *output_file;    /* where to store the constructed key file  */
+    const char *output_file;    /* where to store the constructed CRT   */
     const char *subject_name;   /* subject name for certificate         */
     const char *issuer_name;    /* issuer name for certificate          */
     const char *not_before;     /* validity period not before           */
@@ -770,7 +770,7 @@
     }
 
     /*
-     * 1.2. Writing the request
+     * 1.2. Writing the certificate
      */
     mbedtls_printf( "  . Writing the certificate..." );
     fflush( stdout );
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index ca9c93e..1faa5d5 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -558,6 +558,26 @@
 msg "test: small SSL_IN_CONTENT_LEN - ssl-opt.sh MFL tests"
 if_build_succeeded tests/ssl-opt.sh -f "Max fragment"
 
+msg "build: small MBEDTLS_SSL_DTLS_MAX_BUFFERING #0"
+cleanup
+cp "$CONFIG_H" "$CONFIG_BAK"
+scripts/config.pl set MBEDTLS_SSL_DTLS_MAX_BUFFERING 1000
+CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
+make
+
+msg "test: small MBEDTLS_SSL_DTLS_MAX_BUFFERING #0 - ssl-opt.sh specific reordering test"
+if_build_succeeded tests/ssl-opt.sh -f "DTLS reordering: Buffer out-of-order hs msg before reassembling next, free buffered msg"
+
+msg "build: small MBEDTLS_SSL_DTLS_MAX_BUFFERING #1"
+cleanup
+cp "$CONFIG_H" "$CONFIG_BAK"
+scripts/config.pl set MBEDTLS_SSL_DTLS_MAX_BUFFERING 240
+CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
+make
+
+msg "test: small MBEDTLS_SSL_DTLS_MAX_BUFFERING #1 - ssl-opt.sh specific reordering test"
+if_build_succeeded tests/ssl-opt.sh -f "DTLS reordering: Buffer encrypted Finished message, drop for fragmented NewSessionTicket"
+
 msg "build: cmake, full config, clang" # ~ 50s
 cleanup
 cp "$CONFIG_H" "$CONFIG_BAK"
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 92b7686..30d1ebb 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -41,6 +41,28 @@
 G_CLI="echo 'GET / HTTP/1.0' | $GNUTLS_CLI --x509cafile data_files/test-ca_cat12.crt"
 TCP_CLIENT="$PERL scripts/tcp_client.pl"
 
+# alternative versions of OpenSSL and GnuTLS (no default path)
+
+if [ -n "${OPENSSL_LEGACY:-}" ]; then
+    O_LEGACY_SRV="$OPENSSL_LEGACY s_server -www -cert data_files/server5.crt -key data_files/server5.key"
+    O_LEGACY_CLI="echo 'GET / HTTP/1.0' | $OPENSSL_LEGACY s_client"
+else
+    O_LEGACY_SRV=false
+    O_LEGACY_CLI=false
+fi
+
+if [ -n "${GNUTLS_NEXT_SERV:-}" ]; then
+    G_NEXT_SRV="$GNUTLS_NEXT_SERV --x509certfile data_files/server5.crt --x509keyfile data_files/server5.key"
+else
+    G_NEXT_SRV=false
+fi
+
+if [ -n "${GNUTLS_NEXT_CLI:-}" ]; then
+    G_NEXT_CLI="echo 'GET / HTTP/1.0' | $GNUTLS_NEXT_CLI --x509cafile data_files/test-ca_cat12.crt"
+else
+    G_NEXT_CLI=false
+fi
+
 TESTS=0
 FAILS=0
 SKIPS=0
@@ -120,6 +142,14 @@
     done
 }
 
+# Skip next test; use this macro to skip tests which are legitimate
+# in theory and expected to be re-introduced at some point, but
+# aren't expected to succeed at the moment due to problems outside
+# our control (such as bugs in other TLS implementations).
+skip_next_test() {
+    SKIP_NEXT="YES"
+}
+
 # skip next test if the flag is not enabled in config.h
 requires_config_enabled() {
     if grep "^#define $1" $CONFIG_H > /dev/null; then :; else
@@ -134,6 +164,27 @@
     fi
 }
 
+get_config_value_or_default() {
+    NAME="$1"
+    DEF_VAL=$( grep ".*#define.*${NAME}" ../include/mbedtls/config.h |
+               sed 's/^.*\s\([0-9]*\)$/\1/' )
+    ../scripts/config.pl get $NAME || echo "$DEF_VAL"
+}
+
+requires_config_value_at_least() {
+    VAL=$( get_config_value_or_default "$1" )
+    if [ "$VAL" -lt "$2" ]; then
+       SKIP_NEXT="YES"
+    fi
+}
+
+requires_config_value_at_most() {
+    VAL=$( get_config_value_or_default "$1" )
+    if [ "$VAL" -gt "$2" ]; then
+       SKIP_NEXT="YES"
+    fi
+}
+
 # skip next test if OpenSSL doesn't support FALLBACK_SCSV
 requires_openssl_with_fallback_scsv() {
     if [ -z "${OPENSSL_HAS_FBSCSV:-}" ]; then
@@ -163,6 +214,34 @@
     fi
 }
 
+# skip next test if GnuTLS-next isn't available
+requires_gnutls_next() {
+    if [ -z "${GNUTLS_NEXT_AVAILABLE:-}" ]; then
+        if ( which "${GNUTLS_NEXT_CLI:-}" && which "${GNUTLS_NEXT_SERV:-}" ) >/dev/null 2>&1; then
+            GNUTLS_NEXT_AVAILABLE="YES"
+        else
+            GNUTLS_NEXT_AVAILABLE="NO"
+        fi
+    fi
+    if [ "$GNUTLS_NEXT_AVAILABLE" = "NO" ]; then
+        SKIP_NEXT="YES"
+    fi
+}
+
+# skip next test if OpenSSL-legacy isn't available
+requires_openssl_legacy() {
+    if [ -z "${OPENSSL_LEGACY_AVAILABLE:-}" ]; then
+        if which "${OPENSSL_LEGACY:-}" >/dev/null 2>&1; then
+            OPENSSL_LEGACY_AVAILABLE="YES"
+        else
+            OPENSSL_LEGACY_AVAILABLE="NO"
+        fi
+    fi
+    if [ "$OPENSSL_LEGACY_AVAILABLE" = "NO" ]; then
+        SKIP_NEXT="YES"
+    fi
+}
+
 # skip next test if IPv6 isn't available on this host
 requires_ipv6() {
     if [ -z "${HAS_IPV6:-}" ]; then
@@ -632,6 +711,9 @@
     if [ "$PRESERVE_LOGS" -gt 0 ]; then
         mv $SRV_OUT o-srv-${TESTS}.log
         mv $CLI_OUT o-cli-${TESTS}.log
+        if [ -n "$PXY_CMD" ]; then
+            mv $PXY_OUT o-pxy-${TESTS}.log
+        fi
     fi
 
     rm -f $SRV_OUT $CLI_OUT $PXY_OUT
@@ -715,7 +797,20 @@
 O_SRV="$O_SRV -accept $SRV_PORT -dhparam data_files/dhparams.pem"
 O_CLI="$O_CLI -connect localhost:+SRV_PORT"
 G_SRV="$G_SRV -p $SRV_PORT"
-G_CLI="$G_CLI -p +SRV_PORT localhost"
+G_CLI="$G_CLI -p +SRV_PORT"
+
+if [ -n "${OPENSSL_LEGACY:-}" ]; then
+    O_LEGACY_SRV="$O_LEGACY_SRV -accept $SRV_PORT -dhparam data_files/dhparams.pem"
+    O_LEGACY_CLI="$O_LEGACY_CLI -connect localhost:+SRV_PORT"
+fi
+
+if [ -n "${GNUTLS_NEXT_SERV:-}" ]; then
+    G_NEXT_SRV="$G_NEXT_SRV -p $SRV_PORT"
+fi
+
+if [ -n "${GNUTLS_NEXT_CLI:-}" ]; then
+    G_NEXT_CLI="$G_NEXT_CLI -p +SRV_PORT"
+fi
 
 # Allow SHA-1, because many of our test certificates use it
 P_SRV="$P_SRV allow_sha1=1"
@@ -801,6 +896,22 @@
             -S "SSL - None of the common ciphersuites is usable" \
             -S "SSL - The server has no ciphersuites in common"
 
+# Test empty CA list in CertificateRequest in TLS 1.1 and earlier
+
+requires_gnutls
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_1
+run_test    "CertificateRequest with empty CA list, TLS 1.1 (GnuTLS server)" \
+            "$G_SRV"\
+            "$P_CLI force_version=tls1_1" \
+            0
+
+requires_gnutls
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1
+run_test    "CertificateRequest with empty CA list, TLS 1.0 (GnuTLS server)" \
+            "$G_SRV"\
+            "$P_CLI force_version=tls1" \
+            0
+
 # Tests for SHA-1 support
 
 requires_config_disabled MBEDTLS_TLS_DEFAULT_ALLOW_SHA1_IN_CERTIFICATES
@@ -849,6 +960,35 @@
             "$P_CLI key_file=data_files/cli-rsa.key crt_file=data_files/cli-rsa-sha256.crt" \
             0
 
+# Tests for datagram packing
+run_test    "DTLS: multiple records in same datagram, client and server" \
+            "$P_SRV dtls=1 dgram_packing=1 debug_level=2" \
+            "$P_CLI dtls=1 dgram_packing=1 debug_level=2" \
+            0 \
+            -c "next record in same datagram" \
+            -s "next record in same datagram"
+
+run_test    "DTLS: multiple records in same datagram, client only" \
+            "$P_SRV dtls=1 dgram_packing=0 debug_level=2" \
+            "$P_CLI dtls=1 dgram_packing=1 debug_level=2" \
+            0 \
+            -s "next record in same datagram" \
+            -C "next record in same datagram"
+
+run_test    "DTLS: multiple records in same datagram, server only" \
+            "$P_SRV dtls=1 dgram_packing=1 debug_level=2" \
+            "$P_CLI dtls=1 dgram_packing=0 debug_level=2" \
+            0 \
+            -S "next record in same datagram" \
+            -c "next record in same datagram"
+
+run_test    "DTLS: multiple records in same datagram, neither client nor server" \
+            "$P_SRV dtls=1 dgram_packing=0 debug_level=2" \
+            "$P_CLI dtls=1 dgram_packing=0 debug_level=2" \
+            0 \
+            -S "next record in same datagram" \
+            -C "next record in same datagram"
+
 # Tests for Truncated HMAC extension
 
 run_test    "Truncated HMAC: client default, server default" \
@@ -2215,7 +2355,7 @@
 requires_gnutls
 run_test    "Renego ext: gnutls client strict, server default" \
             "$P_SRV debug_level=3" \
-            "$G_CLI --priority=NORMAL:%SAFE_RENEGOTIATION" \
+            "$G_CLI --priority=NORMAL:%SAFE_RENEGOTIATION localhost" \
             0 \
             -s "received TLS_EMPTY_RENEGOTIATION_INFO\|found renegotiation extension" \
             -s "server hello, secure renegotiation extension"
@@ -2223,7 +2363,7 @@
 requires_gnutls
 run_test    "Renego ext: gnutls client unsafe, server default" \
             "$P_SRV debug_level=3" \
-            "$G_CLI --priority=NORMAL:%DISABLE_SAFE_RENEGOTIATION" \
+            "$G_CLI --priority=NORMAL:%DISABLE_SAFE_RENEGOTIATION localhost" \
             0 \
             -S "received TLS_EMPTY_RENEGOTIATION_INFO\|found renegotiation extension" \
             -S "server hello, secure renegotiation extension"
@@ -2231,7 +2371,7 @@
 requires_gnutls
 run_test    "Renego ext: gnutls client unsafe, server break legacy" \
             "$P_SRV debug_level=3 allow_legacy=-1" \
-            "$G_CLI --priority=NORMAL:%DISABLE_SAFE_RENEGOTIATION" \
+            "$G_CLI --priority=NORMAL:%DISABLE_SAFE_RENEGOTIATION localhost" \
             1 \
             -S "received TLS_EMPTY_RENEGOTIATION_INFO\|found renegotiation extension" \
             -S "server hello, secure renegotiation extension"
@@ -2242,7 +2382,7 @@
 run_test    "DER format: no trailing bytes" \
             "$P_SRV crt_file=data_files/server5-der0.crt \
              key_file=data_files/server5.key" \
-            "$G_CLI " \
+            "$G_CLI localhost" \
             0 \
             -c "Handshake was completed" \
 
@@ -2250,7 +2390,7 @@
 run_test    "DER format: with a trailing zero byte" \
             "$P_SRV crt_file=data_files/server5-der1a.crt \
              key_file=data_files/server5.key" \
-            "$G_CLI " \
+            "$G_CLI localhost" \
             0 \
             -c "Handshake was completed" \
 
@@ -2258,7 +2398,7 @@
 run_test    "DER format: with a trailing random byte" \
             "$P_SRV crt_file=data_files/server5-der1b.crt \
              key_file=data_files/server5.key" \
-            "$G_CLI " \
+            "$G_CLI localhost" \
             0 \
             -c "Handshake was completed" \
 
@@ -2266,7 +2406,7 @@
 run_test    "DER format: with 2 trailing random bytes" \
             "$P_SRV crt_file=data_files/server5-der2.crt \
              key_file=data_files/server5.key" \
-            "$G_CLI " \
+            "$G_CLI localhost" \
             0 \
             -c "Handshake was completed" \
 
@@ -2274,7 +2414,7 @@
 run_test    "DER format: with 4 trailing random bytes" \
             "$P_SRV crt_file=data_files/server5-der4.crt \
              key_file=data_files/server5.key" \
-            "$G_CLI " \
+            "$G_CLI localhost" \
             0 \
             -c "Handshake was completed" \
 
@@ -2282,7 +2422,7 @@
 run_test    "DER format: with 8 trailing random bytes" \
             "$P_SRV crt_file=data_files/server5-der8.crt \
              key_file=data_files/server5.key" \
-            "$G_CLI " \
+            "$G_CLI localhost" \
             0 \
             -c "Handshake was completed" \
 
@@ -2290,7 +2430,7 @@
 run_test    "DER format: with 9 trailing random bytes" \
             "$P_SRV crt_file=data_files/server5-der9.crt \
              key_file=data_files/server5.key" \
-            "$G_CLI " \
+            "$G_CLI localhost" \
             0 \
             -c "Handshake was completed" \
 
@@ -3855,14 +3995,14 @@
 requires_gnutls
 run_test    "ClientHello without extensions, SHA-1 allowed" \
             "$P_SRV debug_level=3" \
-            "$G_CLI --priority=NORMAL:%NO_EXTENSIONS:%DISABLE_SAFE_RENEGOTIATION" \
+            "$G_CLI --priority=NORMAL:%NO_EXTENSIONS:%DISABLE_SAFE_RENEGOTIATION localhost" \
             0 \
             -s "dumping 'client hello extensions' (0 bytes)"
 
 requires_gnutls
 run_test    "ClientHello without extensions, SHA-1 forbidden in certificates on server" \
             "$P_SRV debug_level=3 key_file=data_files/server2.key crt_file=data_files/server2.crt allow_sha1=0" \
-            "$G_CLI --priority=NORMAL:%NO_EXTENSIONS:%DISABLE_SAFE_RENEGOTIATION" \
+            "$G_CLI --priority=NORMAL:%NO_EXTENSIONS:%DISABLE_SAFE_RENEGOTIATION localhost" \
             0 \
             -s "dumping 'client hello extensions' (0 bytes)"
 
@@ -5037,6 +5177,810 @@
             -c "found fragmented DTLS handshake message" \
             -C "error"
 
+# Tests for sending fragmented handshake messages with DTLS
+#
+# Use client auth when we need the client to send large messages,
+# and use large cert chains on both sides too (the long chains we have all use
+# both RSA and ECDSA, but ideally we should have long chains with either).
+# Sizes reached (UDP payload):
+# - 2037B for server certificate
+# - 1542B for client certificate
+# - 1013B for newsessionticket
+# - all others below 512B
+# All those tests assume MAX_CONTENT_LEN is at least 2048
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_MAX_FRAGMENT_LENGTH
+run_test    "DTLS fragmenting: none (for reference)" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             max_frag_len=4096" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             max_frag_len=4096" \
+            0 \
+            -S "found fragmented DTLS handshake message" \
+            -C "found fragmented DTLS handshake message" \
+            -C "error"
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_MAX_FRAGMENT_LENGTH
+run_test    "DTLS fragmenting: server only (max_frag_len)" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             max_frag_len=1024" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             max_frag_len=2048" \
+            0 \
+            -S "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+# With the MFL extension, the server has no way of forcing
+# the client to not exceed a certain MTU; hence, the following
+# test can't be replicated with an MTU proxy such as the one
+# `client-initiated, server only (max_frag_len)` below.
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_MAX_FRAGMENT_LENGTH
+run_test    "DTLS fragmenting: server only (more) (max_frag_len)" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             max_frag_len=512" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             max_frag_len=4096" \
+            0 \
+            -S "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_MAX_FRAGMENT_LENGTH
+run_test    "DTLS fragmenting: client-initiated, server only (max_frag_len)" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=none \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             max_frag_len=2048" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             max_frag_len=512" \
+            0 \
+            -S "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+# While not required by the standard defining the MFL extension
+# (according to which it only applies to records, not to datagrams),
+# Mbed TLS will never send datagrams larger than MFL + { Max record expansion },
+# as otherwise there wouldn't be any means to communicate MTU restrictions
+# to the peer.
+# The next test checks that no datagrams significantly larger than the
+# negotiated MFL are sent.
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_MAX_FRAGMENT_LENGTH
+run_test    "DTLS fragmenting: client-initiated, server only (max_frag_len), proxy MTU" \
+            -p "$P_PXY mtu=560" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=none \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             max_frag_len=2048" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             max_frag_len=512" \
+            0 \
+            -S "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_MAX_FRAGMENT_LENGTH
+run_test    "DTLS fragmenting: client-initiated, both (max_frag_len)" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             max_frag_len=2048" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             max_frag_len=512" \
+            0 \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+# While not required by the standard defining the MFL extension
+# (according to which it only applies to records, not to datagrams),
+# Mbed TLS will never send datagrams larger than MFL + { Max record expansion },
+# as otherwise there wouldn't be any means to communicate MTU restrictions
+# to the peer.
+# The next test checks that no datagrams significantly larger than the
+# negotiated MFL are sent.
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_MAX_FRAGMENT_LENGTH
+run_test    "DTLS fragmenting: client-initiated, both (max_frag_len), proxy MTU" \
+            -p "$P_PXY mtu=560" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             max_frag_len=2048" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             max_frag_len=512" \
+            0 \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+run_test    "DTLS fragmenting: none (for reference) (MTU)" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             mtu=4096" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             mtu=4096" \
+            0 \
+            -S "found fragmented DTLS handshake message" \
+            -C "found fragmented DTLS handshake message" \
+            -C "error"
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+run_test    "DTLS fragmenting: client (MTU)" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             mtu=4096" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             mtu=512" \
+            0 \
+            -s "found fragmented DTLS handshake message" \
+            -C "found fragmented DTLS handshake message" \
+            -C "error"
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+run_test    "DTLS fragmenting: server (MTU)" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             mtu=512" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             mtu=2048" \
+            0 \
+            -S "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+run_test    "DTLS fragmenting: both (MTU)" \
+            -p "$P_PXY mtu=512" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             mtu=512" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             mtu=512" \
+            0 \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+# Test for automatic MTU reduction on repeated resend
+not_with_valgrind
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+run_test    "DTLS fragmenting: proxy MTU: auto-reduction" \
+            -p "$P_PXY mtu=508" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key\
+             hs_timeout=100-400" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             hs_timeout=100-400" \
+            0 \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+only_with_valgrind
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+run_test    "DTLS fragmenting: proxy MTU: auto-reduction" \
+            -p "$P_PXY mtu=508" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key\
+             hs_timeout=250-10000" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             hs_timeout=250-10000" \
+            0 \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+# the proxy shouldn't drop or mess up anything, so we shouldn't need to resend
+# OTOH the client might resend if the server is to slow to reset after sending
+# a HelloVerifyRequest, so only check for no retransmission server-side
+not_with_valgrind # spurious resend due to timeout
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+run_test    "DTLS fragmenting: proxy MTU, simple handshake" \
+            -p "$P_PXY mtu=512" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             mtu=512" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             mtu=512" \
+            0 \
+            -S "resend" \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+not_with_valgrind # spurious resend due to timeout
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+run_test    "DTLS fragmenting: proxy MTU, simple handshake, nbio" \
+            -p "$P_PXY mtu=512" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             mtu=512 nbio=2" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             mtu=512 nbio=2" \
+            0 \
+            -S "resend" \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+# This ensures things still work after session_reset().
+# It also exercises the "resumed handshake" flow.
+# Since we don't support reading fragmented ClientHello yet,
+# up the MTU to 1450 (larger than ClientHello with session ticket,
+# but still smaller than client's Certificate to ensure fragmentation).
+# A resend on the client-side might happen if the server is
+# slow to reset, therefore omitting '-C "resend"' below.
+# reco_delay avoids races where the client reconnects before the server has
+# resumed listening, which would result in a spurious resend.
+not_with_valgrind # spurious resend due to timeout
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+run_test    "DTLS fragmenting: proxy MTU, resumed handshake" \
+            -p "$P_PXY mtu=1450" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             mtu=1450" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             mtu=1450 reconnect=1 reco_delay=1" \
+            0 \
+            -S "resend" \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+# A resend on the client-side might happen if the server is
+# slow to reset, therefore omitting '-C "resend"' below.
+not_with_valgrind # spurious resend due to timeout
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SHA256_C
+requires_config_enabled MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA
+requires_config_enabled MBEDTLS_SSL_RENEGOTIATION
+requires_config_enabled MBEDTLS_CHACHAPOLY_C
+run_test    "DTLS fragmenting: proxy MTU, ChachaPoly renego" \
+            -p "$P_PXY mtu=512" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             exchanges=2 renegotiation=1 \
+             force_ciphersuite=TLS-ECDHE-ECDSA-WITH-CHACHA20-POLY1305-SHA256 \
+             mtu=512" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             exchanges=2 renegotiation=1 renegotiate=1 \
+             mtu=512" \
+            0 \
+            -S "resend" \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+# A resend on the client-side might happen if the server is
+# slow to reset, therefore omitting '-C "resend"' below.
+not_with_valgrind # spurious resend due to timeout
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SHA256_C
+requires_config_enabled MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA
+requires_config_enabled MBEDTLS_SSL_RENEGOTIATION
+requires_config_enabled MBEDTLS_AES_C
+requires_config_enabled MBEDTLS_GCM_C
+run_test    "DTLS fragmenting: proxy MTU, AES-GCM renego" \
+            -p "$P_PXY mtu=512" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             exchanges=2 renegotiation=1 \
+             force_ciphersuite=TLS-ECDHE-ECDSA-WITH-AES-128-GCM-SHA256 \
+             mtu=512" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             exchanges=2 renegotiation=1 renegotiate=1 \
+             mtu=512" \
+            0 \
+            -S "resend" \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+# A resend on the client-side might happen if the server is
+# slow to reset, therefore omitting '-C "resend"' below.
+not_with_valgrind # spurious resend due to timeout
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SHA256_C
+requires_config_enabled MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA
+requires_config_enabled MBEDTLS_SSL_RENEGOTIATION
+requires_config_enabled MBEDTLS_AES_C
+requires_config_enabled MBEDTLS_CCM_C
+run_test    "DTLS fragmenting: proxy MTU, AES-CCM renego" \
+            -p "$P_PXY mtu=512" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             exchanges=2 renegotiation=1 \
+             force_ciphersuite=TLS-ECDHE-ECDSA-WITH-AES-128-CCM-8 \
+             mtu=512" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             exchanges=2 renegotiation=1 renegotiate=1 \
+             mtu=512" \
+            0 \
+            -S "resend" \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+# A resend on the client-side might happen if the server is
+# slow to reset, therefore omitting '-C "resend"' below.
+not_with_valgrind # spurious resend due to timeout
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SHA256_C
+requires_config_enabled MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA
+requires_config_enabled MBEDTLS_SSL_RENEGOTIATION
+requires_config_enabled MBEDTLS_AES_C
+requires_config_enabled MBEDTLS_CIPHER_MODE_CBC
+requires_config_enabled MBEDTLS_SSL_ENCRYPT_THEN_MAC
+run_test    "DTLS fragmenting: proxy MTU, AES-CBC EtM renego" \
+            -p "$P_PXY mtu=512" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             exchanges=2 renegotiation=1 \
+             force_ciphersuite=TLS-ECDHE-ECDSA-WITH-AES-128-CBC-SHA256 \
+             mtu=512" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             exchanges=2 renegotiation=1 renegotiate=1 \
+             mtu=512" \
+            0 \
+            -S "resend" \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+# A resend on the client-side might happen if the server is
+# slow to reset, therefore omitting '-C "resend"' below.
+not_with_valgrind # spurious resend due to timeout
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SHA256_C
+requires_config_enabled MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA
+requires_config_enabled MBEDTLS_SSL_RENEGOTIATION
+requires_config_enabled MBEDTLS_AES_C
+requires_config_enabled MBEDTLS_CIPHER_MODE_CBC
+run_test    "DTLS fragmenting: proxy MTU, AES-CBC non-EtM renego" \
+            -p "$P_PXY mtu=512" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             exchanges=2 renegotiation=1 \
+             force_ciphersuite=TLS-ECDHE-ECDSA-WITH-AES-128-CBC-SHA256 etm=0 \
+             mtu=512" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             exchanges=2 renegotiation=1 renegotiate=1 \
+             mtu=512" \
+            0 \
+            -S "resend" \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+client_needs_more_time 2
+run_test    "DTLS fragmenting: proxy MTU + 3d" \
+            -p "$P_PXY mtu=512 drop=8 delay=8 duplicate=8" \
+            "$P_SRV dgram_packing=0 dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             hs_timeout=250-10000 mtu=512" \
+            "$P_CLI dgram_packing=0 dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             hs_timeout=250-10000 mtu=512" \
+            0 \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+client_needs_more_time 2
+run_test    "DTLS fragmenting: proxy MTU + 3d, nbio" \
+            -p "$P_PXY mtu=512 drop=8 delay=8 duplicate=8" \
+            "$P_SRV dtls=1 debug_level=2 auth_mode=required \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             hs_timeout=250-10000 mtu=512 nbio=2" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             hs_timeout=250-10000 mtu=512 nbio=2" \
+            0 \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
+# interop tests for DTLS fragmentating with reliable connection
+#
+# here and below we just want to test that the we fragment in a way that
+# pleases other implementations, so we don't need the peer to fragment
+requires_gnutls
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_2
+requires_gnutls
+run_test    "DTLS fragmenting: gnutls server, DTLS 1.2" \
+            "$G_SRV -u" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             mtu=512 force_version=dtls1_2" \
+            0 \
+            -c "fragmenting handshake message" \
+            -C "error"
+
+requires_gnutls
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_1
+requires_gnutls
+run_test    "DTLS fragmenting: gnutls server, DTLS 1.0" \
+            "$G_SRV -u" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             mtu=512 force_version=dtls1" \
+            0 \
+            -c "fragmenting handshake message" \
+            -C "error"
+
+# We use --insecure for the GnuTLS client because it expects
+# the hostname / IP it connects to to be the name used in the
+# certificate obtained from the server. Here, however, it
+# connects to 127.0.0.1 while our test certificates use 'localhost'
+# as the server name in the certificate. This will make the
+# certifiate validation fail, but passing --insecure makes
+# GnuTLS continue the connection nonetheless.
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_2
+requires_gnutls
+run_test    "DTLS fragmenting: gnutls client, DTLS 1.2" \
+            "$P_SRV dtls=1 debug_level=2 \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             mtu=512 force_version=dtls1_2" \
+            "$G_CLI -u --insecure 127.0.0.1" \
+            0 \
+            -s "fragmenting handshake message"
+
+# See previous test for the reason to use --insecure
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_1
+requires_gnutls
+run_test    "DTLS fragmenting: gnutls client, DTLS 1.0" \
+            "$P_SRV dtls=1 debug_level=2 \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             mtu=512 force_version=dtls1" \
+            "$G_CLI -u --insecure 127.0.0.1" \
+            0 \
+            -s "fragmenting handshake message"
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_2
+run_test    "DTLS fragmenting: openssl server, DTLS 1.2" \
+            "$O_SRV -dtls1_2 -verify 10" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             mtu=512 force_version=dtls1_2" \
+            0 \
+            -c "fragmenting handshake message" \
+            -C "error"
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_1
+run_test    "DTLS fragmenting: openssl server, DTLS 1.0" \
+            "$O_SRV -dtls1 -verify 10" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             mtu=512 force_version=dtls1" \
+            0 \
+            -c "fragmenting handshake message" \
+            -C "error"
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_2
+run_test    "DTLS fragmenting: openssl client, DTLS 1.2" \
+            "$P_SRV dtls=1 debug_level=2 \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             mtu=512 force_version=dtls1_2" \
+            "$O_CLI -dtls1_2" \
+            0 \
+            -s "fragmenting handshake message"
+
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_1
+run_test    "DTLS fragmenting: openssl client, DTLS 1.0" \
+            "$P_SRV dtls=1 debug_level=2 \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             mtu=512 force_version=dtls1" \
+            "$O_CLI -dtls1" \
+            0 \
+            -s "fragmenting handshake message"
+
+# interop tests for DTLS fragmentating with unreliable connection
+#
+# again we just want to test that the we fragment in a way that
+# pleases other implementations, so we don't need the peer to fragment
+requires_gnutls_next
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_2
+client_needs_more_time 4
+run_test    "DTLS fragmenting: 3d, gnutls server, DTLS 1.2" \
+            -p "$P_PXY drop=8 delay=8 duplicate=8" \
+            "$G_NEXT_SRV -u" \
+            "$P_CLI dgram_packing=0 dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             hs_timeout=250-60000 mtu=512 force_version=dtls1_2" \
+            0 \
+            -c "fragmenting handshake message" \
+            -C "error"
+
+requires_gnutls_next
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_1
+client_needs_more_time 4
+run_test    "DTLS fragmenting: 3d, gnutls server, DTLS 1.0" \
+            -p "$P_PXY drop=8 delay=8 duplicate=8" \
+            "$G_NEXT_SRV -u" \
+            "$P_CLI dgram_packing=0 dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             hs_timeout=250-60000 mtu=512 force_version=dtls1" \
+            0 \
+            -c "fragmenting handshake message" \
+            -C "error"
+
+## The two tests below are disabled due to a bug in GnuTLS client that causes
+## handshake failures when the NewSessionTicket message is lost, see
+## https://gitlab.com/gnutls/gnutls/issues/543
+## We can re-enable them when a fixed version fo GnuTLS is available
+## and installed in our CI system.
+skip_next_test
+requires_gnutls
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_2
+client_needs_more_time 4
+run_test    "DTLS fragmenting: 3d, gnutls client, DTLS 1.2" \
+            -p "$P_PXY drop=8 delay=8 duplicate=8" \
+            "$P_SRV dtls=1 debug_level=2 \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             hs_timeout=250-60000 mtu=512 force_version=dtls1_2" \
+           "$G_CLI -u --insecure 127.0.0.1" \
+            0 \
+            -s "fragmenting handshake message"
+
+skip_next_test
+requires_gnutls
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_1
+client_needs_more_time 4
+run_test    "DTLS fragmenting: 3d, gnutls client, DTLS 1.0" \
+            -p "$P_PXY drop=8 delay=8 duplicate=8" \
+            "$P_SRV dtls=1 debug_level=2 \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             hs_timeout=250-60000 mtu=512 force_version=dtls1" \
+           "$G_CLI -u --insecure 127.0.0.1" \
+            0 \
+            -s "fragmenting handshake message"
+
+## Interop test with OpenSSL might triger a bug in recent versions (that
+## probably won't be fixed before 1.1.1X), so we use an old version that
+## doesn't have this bug, but unfortunately it doesn't have support for DTLS
+## 1.2 either, so the DTLS 1.2 tests are commented for now.
+## Bug report: https://github.com/openssl/openssl/issues/6902
+## They should be re-enabled (and the DTLS 1.0 switched back to a non-legacy
+## version of OpenSSL once a fixed version of OpenSSL is available)
+skip_next_test
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_2
+client_needs_more_time 4
+run_test    "DTLS fragmenting: 3d, openssl server, DTLS 1.2" \
+            -p "$P_PXY drop=8 delay=8 duplicate=8" \
+            "$O_SRV -dtls1_2 -verify 10" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             hs_timeout=250-60000 mtu=512 force_version=dtls1_2" \
+            0 \
+            -c "fragmenting handshake message" \
+            -C "error"
+
+requires_openssl_legacy
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_1
+client_needs_more_time 4
+run_test    "DTLS fragmenting: 3d, openssl server, DTLS 1.0" \
+            -p "$P_PXY drop=8 delay=8 duplicate=8" \
+            "$O_LEGACY_SRV -dtls1 -verify 10" \
+            "$P_CLI dgram_packing=0 dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             hs_timeout=250-60000 mtu=512 force_version=dtls1" \
+            0 \
+            -c "fragmenting handshake message" \
+            -C "error"
+
+## see comment on the previous-previous test
+## requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+## requires_config_enabled MBEDTLS_RSA_C
+## requires_config_enabled MBEDTLS_ECDSA_C
+## requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_2
+## client_needs_more_time 4
+## run_test    "DTLS fragmenting: 3d, openssl client, DTLS 1.2" \
+##             -p "$P_PXY drop=8 delay=8 duplicate=8" \
+##             "$P_SRV dtls=1 debug_level=2 \
+##              crt_file=data_files/server7_int-ca.crt \
+##              key_file=data_files/server7.key \
+##              hs_timeout=250-60000 mtu=512 force_version=dtls1_2" \
+##             "$O_CLI -dtls1_2" \
+##             0 \
+##             -s "fragmenting handshake message"
+
+# -nbio is added to prevent s_client from blocking in case of duplicated
+# messages at the end of the handshake
+requires_openssl_legacy
+requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
+requires_config_enabled MBEDTLS_RSA_C
+requires_config_enabled MBEDTLS_ECDSA_C
+requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_1
+client_needs_more_time 4
+run_test    "DTLS fragmenting: 3d, openssl client, DTLS 1.0" \
+            -p "$P_PXY drop=8 delay=8 duplicate=8" \
+            "$P_SRV dgram_packing=0 dtls=1 debug_level=2 \
+             crt_file=data_files/server7_int-ca.crt \
+             key_file=data_files/server7.key \
+             hs_timeout=250-60000 mtu=512 force_version=dtls1" \
+            "$O_LEGACY_CLI -nbio -dtls1" \
+            0 \
+            -s "fragmenting handshake message"
+
 # Tests for specific things with "unreliable" UDP connection
 
 not_with_valgrind # spurious resend due to timeout
@@ -5058,8 +6002,8 @@
 not_with_valgrind # spurious resend due to timeout
 run_test    "DTLS proxy: duplicate every packet" \
             -p "$P_PXY duplicate=1" \
-            "$P_SRV dtls=1 debug_level=2" \
-            "$P_CLI dtls=1 debug_level=2" \
+            "$P_SRV dtls=1 dgram_packing=0 debug_level=2" \
+            "$P_CLI dtls=1 dgram_packing=0 debug_level=2" \
             0 \
             -c "replayed record" \
             -s "replayed record" \
@@ -5071,8 +6015,8 @@
 
 run_test    "DTLS proxy: duplicate every packet, server anti-replay off" \
             -p "$P_PXY duplicate=1" \
-            "$P_SRV dtls=1 debug_level=2 anti_replay=0" \
-            "$P_CLI dtls=1 debug_level=2" \
+            "$P_SRV dtls=1 dgram_packing=0 debug_level=2 anti_replay=0" \
+            "$P_CLI dtls=1 dgram_packing=0 debug_level=2" \
             0 \
             -c "replayed record" \
             -S "replayed record" \
@@ -5085,24 +6029,24 @@
 
 run_test    "DTLS proxy: multiple records in same datagram" \
             -p "$P_PXY pack=50" \
-            "$P_SRV dtls=1 debug_level=2" \
-            "$P_CLI dtls=1 debug_level=2" \
+            "$P_SRV dtls=1 dgram_packing=0 debug_level=2" \
+            "$P_CLI dtls=1 dgram_packing=0 debug_level=2" \
             0 \
             -c "next record in same datagram" \
             -s "next record in same datagram"
 
 run_test    "DTLS proxy: multiple records in same datagram, duplicate every packet" \
             -p "$P_PXY pack=50 duplicate=1" \
-            "$P_SRV dtls=1 debug_level=2" \
-            "$P_CLI dtls=1 debug_level=2" \
+            "$P_SRV dtls=1 dgram_packing=0 debug_level=2" \
+            "$P_CLI dtls=1 dgram_packing=0 debug_level=2" \
             0 \
             -c "next record in same datagram" \
             -s "next record in same datagram"
 
 run_test    "DTLS proxy: inject invalid AD record, default badmac_limit" \
             -p "$P_PXY bad_ad=1" \
-            "$P_SRV dtls=1 debug_level=1" \
-            "$P_CLI dtls=1 debug_level=1 read_timeout=100" \
+            "$P_SRV dtls=1 dgram_packing=0 debug_level=1" \
+            "$P_CLI dtls=1 dgram_packing=0 debug_level=1 read_timeout=100" \
             0 \
             -c "discarding invalid record (mac)" \
             -s "discarding invalid record (mac)" \
@@ -5113,8 +6057,8 @@
 
 run_test    "DTLS proxy: inject invalid AD record, badmac_limit 1" \
             -p "$P_PXY bad_ad=1" \
-            "$P_SRV dtls=1 debug_level=1 badmac_limit=1" \
-            "$P_CLI dtls=1 debug_level=1 read_timeout=100" \
+            "$P_SRV dtls=1 dgram_packing=0 debug_level=1 badmac_limit=1" \
+            "$P_CLI dtls=1 dgram_packing=0 debug_level=1 read_timeout=100" \
             1 \
             -C "discarding invalid record (mac)" \
             -S "discarding invalid record (mac)" \
@@ -5125,8 +6069,8 @@
 
 run_test    "DTLS proxy: inject invalid AD record, badmac_limit 2" \
             -p "$P_PXY bad_ad=1" \
-            "$P_SRV dtls=1 debug_level=1 badmac_limit=2" \
-            "$P_CLI dtls=1 debug_level=1 read_timeout=100" \
+            "$P_SRV dtls=1 dgram_packing=0 debug_level=1 badmac_limit=2" \
+            "$P_CLI dtls=1 dgram_packing=0 debug_level=1 read_timeout=100" \
             0 \
             -c "discarding invalid record (mac)" \
             -s "discarding invalid record (mac)" \
@@ -5137,8 +6081,8 @@
 
 run_test    "DTLS proxy: inject invalid AD record, badmac_limit 2, exchanges 2"\
             -p "$P_PXY bad_ad=1" \
-            "$P_SRV dtls=1 debug_level=1 badmac_limit=2 exchanges=2" \
-            "$P_CLI dtls=1 debug_level=1 read_timeout=100 exchanges=2" \
+            "$P_SRV dtls=1 dgram_packing=0 debug_level=1 badmac_limit=2 exchanges=2" \
+            "$P_CLI dtls=1 dgram_packing=0 debug_level=1 read_timeout=100 exchanges=2" \
             1 \
             -c "discarding invalid record (mac)" \
             -s "discarding invalid record (mac)" \
@@ -5149,22 +6093,174 @@
 
 run_test    "DTLS proxy: delay ChangeCipherSpec" \
             -p "$P_PXY delay_ccs=1" \
-            "$P_SRV dtls=1 debug_level=1" \
-            "$P_CLI dtls=1 debug_level=1" \
+            "$P_SRV dtls=1 debug_level=1 dgram_packing=0" \
+            "$P_CLI dtls=1 debug_level=1 dgram_packing=0" \
             0 \
             -c "record from another epoch" \
             -s "record from another epoch" \
             -s "Extra-header:" \
             -c "HTTP/1.0 200 OK"
 
+# Tests for reordering support with DTLS
+
+run_test    "DTLS reordering: Buffer out-of-order handshake message on client" \
+            -p "$P_PXY delay_srv=ServerHello" \
+            "$P_SRV dgram_packing=0 cookies=0 dtls=1 debug_level=2" \
+            "$P_CLI dgram_packing=0 dtls=1 debug_level=2" \
+            0 \
+            -c "Buffering HS message" \
+            -c "Next handshake message has been buffered - load"\
+            -S "Buffering HS message" \
+            -S "Next handshake message has been buffered - load"\
+            -C "Injecting buffered CCS message" \
+            -C "Remember CCS message" \
+            -S "Injecting buffered CCS message" \
+            -S "Remember CCS message"
+
+run_test    "DTLS reordering: Buffer out-of-order handshake message fragment on client" \
+            -p "$P_PXY delay_srv=ServerHello" \
+            "$P_SRV mtu=512 dgram_packing=0 cookies=0 dtls=1 debug_level=2" \
+            "$P_CLI dgram_packing=0 dtls=1 debug_level=2" \
+            0 \
+            -c "Buffering HS message" \
+            -c "found fragmented DTLS handshake message"\
+            -c "Next handshake message 1 not or only partially bufffered" \
+            -c "Next handshake message has been buffered - load"\
+            -S "Buffering HS message" \
+            -S "Next handshake message has been buffered - load"\
+            -C "Injecting buffered CCS message" \
+            -C "Remember CCS message" \
+            -S "Injecting buffered CCS message" \
+            -S "Remember CCS message"
+
+# The client buffers the ServerKeyExchange before receiving the fragmented
+# Certificate message; at the time of writing, together these are aroudn 1200b
+# in size, so that the bound below ensures that the certificate can be reassembled
+# while keeping the ServerKeyExchange.
+requires_config_value_at_least "MBEDTLS_SSL_DTLS_MAX_BUFFERING" 1300
+run_test    "DTLS reordering: Buffer out-of-order hs msg before reassembling next" \
+            -p "$P_PXY delay_srv=Certificate delay_srv=Certificate" \
+            "$P_SRV mtu=512 dgram_packing=0 cookies=0 dtls=1 debug_level=2" \
+            "$P_CLI dgram_packing=0 dtls=1 debug_level=2" \
+            0 \
+            -c "Buffering HS message" \
+            -c "Next handshake message has been buffered - load"\
+            -C "attempt to make space by freeing buffered messages" \
+            -S "Buffering HS message" \
+            -S "Next handshake message has been buffered - load"\
+            -C "Injecting buffered CCS message" \
+            -C "Remember CCS message" \
+            -S "Injecting buffered CCS message" \
+            -S "Remember CCS message"
+
+# The size constraints ensure that the delayed certificate message can't
+# be reassembled while keeping the ServerKeyExchange message, but it can
+# when dropping it first.
+requires_config_value_at_least "MBEDTLS_SSL_DTLS_MAX_BUFFERING" 900
+requires_config_value_at_most "MBEDTLS_SSL_DTLS_MAX_BUFFERING" 1299
+run_test    "DTLS reordering: Buffer out-of-order hs msg before reassembling next, free buffered msg" \
+            -p "$P_PXY delay_srv=Certificate delay_srv=Certificate" \
+            "$P_SRV mtu=512 dgram_packing=0 cookies=0 dtls=1 debug_level=2" \
+            "$P_CLI dgram_packing=0 dtls=1 debug_level=2" \
+            0 \
+            -c "Buffering HS message" \
+            -c "attempt to make space by freeing buffered future messages" \
+            -c "Enough space available after freeing buffered HS messages" \
+            -S "Buffering HS message" \
+            -S "Next handshake message has been buffered - load"\
+            -C "Injecting buffered CCS message" \
+            -C "Remember CCS message" \
+            -S "Injecting buffered CCS message" \
+            -S "Remember CCS message"
+
+run_test    "DTLS reordering: Buffer out-of-order handshake message on server" \
+            -p "$P_PXY delay_cli=Certificate" \
+            "$P_SRV dgram_packing=0 auth_mode=required cookies=0 dtls=1 debug_level=2" \
+            "$P_CLI dgram_packing=0 dtls=1 debug_level=2" \
+            0 \
+            -C "Buffering HS message" \
+            -C "Next handshake message has been buffered - load"\
+            -s "Buffering HS message" \
+            -s "Next handshake message has been buffered - load" \
+            -C "Injecting buffered CCS message" \
+            -C "Remember CCS message" \
+            -S "Injecting buffered CCS message" \
+            -S "Remember CCS message"
+
+run_test    "DTLS reordering: Buffer out-of-order CCS message on client"\
+            -p "$P_PXY delay_srv=NewSessionTicket" \
+            "$P_SRV dgram_packing=0 cookies=0 dtls=1 debug_level=2" \
+            "$P_CLI dgram_packing=0 dtls=1 debug_level=2" \
+            0 \
+            -C "Buffering HS message" \
+            -C "Next handshake message has been buffered - load"\
+            -S "Buffering HS message" \
+            -S "Next handshake message has been buffered - load" \
+            -c "Injecting buffered CCS message" \
+            -c "Remember CCS message" \
+            -S "Injecting buffered CCS message" \
+            -S "Remember CCS message"
+
+run_test    "DTLS reordering: Buffer out-of-order CCS message on server"\
+            -p "$P_PXY delay_cli=ClientKeyExchange" \
+            "$P_SRV dgram_packing=0 cookies=0 dtls=1 debug_level=2" \
+            "$P_CLI dgram_packing=0 dtls=1 debug_level=2" \
+            0 \
+            -C "Buffering HS message" \
+            -C "Next handshake message has been buffered - load"\
+            -S "Buffering HS message" \
+            -S "Next handshake message has been buffered - load" \
+            -C "Injecting buffered CCS message" \
+            -C "Remember CCS message" \
+            -s "Injecting buffered CCS message" \
+            -s "Remember CCS message"
+
+run_test    "DTLS reordering: Buffer encrypted Finished message" \
+            -p "$P_PXY delay_ccs=1" \
+            "$P_SRV dgram_packing=0 cookies=0 dtls=1 debug_level=2" \
+            "$P_CLI dgram_packing=0 dtls=1 debug_level=2" \
+            0 \
+            -s "Buffer record from epoch 1" \
+            -s "Found buffered record from current epoch - load" \
+            -c "Buffer record from epoch 1" \
+            -c "Found buffered record from current epoch - load"
+
+# In this test, both the fragmented NewSessionTicket and the ChangeCipherSpec
+# from the server are delayed, so that the encrypted Finished message
+# is received and buffered. When the fragmented NewSessionTicket comes
+# in afterwards, the encrypted Finished message must be freed in order
+# to make space for the NewSessionTicket to be reassembled.
+# This works only in very particular circumstances:
+# - MBEDTLS_SSL_DTLS_MAX_BUFFERING must be large enough to allow buffering
+#   of the NewSessionTicket, but small enough to also allow buffering of
+#   the encrypted Finished message.
+# - The MTU setting on the server must be so small that the NewSessionTicket
+#   needs to be fragmented.
+# - All messages sent by the server must be small enough to be either sent
+#   without fragmentation or be reassembled within the bounds of
+#   MBEDTLS_SSL_DTLS_MAX_BUFFERING. Achieve this by testing with a PSK-based
+#   handshake, omitting CRTs.
+requires_config_value_at_least "MBEDTLS_SSL_DTLS_MAX_BUFFERING" 240
+requires_config_value_at_most "MBEDTLS_SSL_DTLS_MAX_BUFFERING" 280
+run_test    "DTLS reordering: Buffer encrypted Finished message, drop for fragmented NewSessionTicket" \
+            -p "$P_PXY delay_srv=NewSessionTicket delay_srv=NewSessionTicket delay_ccs=1" \
+            "$P_SRV mtu=190 dgram_packing=0 psk=abc123 psk_identity=foo cookies=0 dtls=1 debug_level=2" \
+            "$P_CLI dgram_packing=0 dtls=1 debug_level=2 force_ciphersuite=TLS-PSK-WITH-AES-128-CCM-8 psk=abc123 psk_identity=foo" \
+            0 \
+            -s "Buffer record from epoch 1" \
+            -s "Found buffered record from current epoch - load" \
+            -c "Buffer record from epoch 1" \
+            -C "Found buffered record from current epoch - load" \
+            -c "Enough space available after freeing future epoch record"
+
 # Tests for "randomly unreliable connection": try a variety of flows and peers
 
 client_needs_more_time 2
 run_test    "DTLS proxy: 3d (drop, delay, duplicate), \"short\" PSK handshake" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
-            "$P_SRV dtls=1 hs_timeout=250-10000 tickets=0 auth_mode=none \
+            "$P_SRV dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 auth_mode=none \
              psk=abc123" \
-            "$P_CLI dtls=1 hs_timeout=250-10000 tickets=0 psk=abc123 \
+            "$P_CLI dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 psk=abc123 \
              force_ciphersuite=TLS-PSK-WITH-AES-128-CCM-8" \
             0 \
             -s "Extra-header:" \
@@ -5173,8 +6269,8 @@
 client_needs_more_time 2
 run_test    "DTLS proxy: 3d, \"short\" RSA handshake" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
-            "$P_SRV dtls=1 hs_timeout=250-10000 tickets=0 auth_mode=none" \
-            "$P_CLI dtls=1 hs_timeout=250-10000 tickets=0 \
+            "$P_SRV dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 auth_mode=none" \
+            "$P_CLI dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 \
              force_ciphersuite=TLS-RSA-WITH-AES-128-CBC-SHA" \
             0 \
             -s "Extra-header:" \
@@ -5183,8 +6279,8 @@
 client_needs_more_time 2
 run_test    "DTLS proxy: 3d, \"short\" (no ticket, no cli_auth) FS handshake" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
-            "$P_SRV dtls=1 hs_timeout=250-10000 tickets=0 auth_mode=none" \
-            "$P_CLI dtls=1 hs_timeout=250-10000 tickets=0" \
+            "$P_SRV dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 auth_mode=none" \
+            "$P_CLI dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0" \
             0 \
             -s "Extra-header:" \
             -c "HTTP/1.0 200 OK"
@@ -5192,8 +6288,8 @@
 client_needs_more_time 2
 run_test    "DTLS proxy: 3d, FS, client auth" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
-            "$P_SRV dtls=1 hs_timeout=250-10000 tickets=0 auth_mode=required" \
-            "$P_CLI dtls=1 hs_timeout=250-10000 tickets=0" \
+            "$P_SRV dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 auth_mode=required" \
+            "$P_CLI dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0" \
             0 \
             -s "Extra-header:" \
             -c "HTTP/1.0 200 OK"
@@ -5201,8 +6297,8 @@
 client_needs_more_time 2
 run_test    "DTLS proxy: 3d, FS, ticket" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
-            "$P_SRV dtls=1 hs_timeout=250-10000 tickets=1 auth_mode=none" \
-            "$P_CLI dtls=1 hs_timeout=250-10000 tickets=1" \
+            "$P_SRV dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=1 auth_mode=none" \
+            "$P_CLI dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=1" \
             0 \
             -s "Extra-header:" \
             -c "HTTP/1.0 200 OK"
@@ -5210,8 +6306,8 @@
 client_needs_more_time 2
 run_test    "DTLS proxy: 3d, max handshake (FS, ticket + client auth)" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
-            "$P_SRV dtls=1 hs_timeout=250-10000 tickets=1 auth_mode=required" \
-            "$P_CLI dtls=1 hs_timeout=250-10000 tickets=1" \
+            "$P_SRV dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=1 auth_mode=required" \
+            "$P_CLI dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=1" \
             0 \
             -s "Extra-header:" \
             -c "HTTP/1.0 200 OK"
@@ -5219,9 +6315,9 @@
 client_needs_more_time 2
 run_test    "DTLS proxy: 3d, max handshake, nbio" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
-            "$P_SRV dtls=1 hs_timeout=250-10000 nbio=2 tickets=1 \
+            "$P_SRV dtls=1 dgram_packing=0 hs_timeout=250-10000 nbio=2 tickets=1 \
              auth_mode=required" \
-            "$P_CLI dtls=1 hs_timeout=250-10000 nbio=2 tickets=1" \
+            "$P_CLI dtls=1 dgram_packing=0 hs_timeout=250-10000 nbio=2 tickets=1" \
             0 \
             -s "Extra-header:" \
             -c "HTTP/1.0 200 OK"
@@ -5229,9 +6325,9 @@
 client_needs_more_time 4
 run_test    "DTLS proxy: 3d, min handshake, resumption" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
-            "$P_SRV dtls=1 hs_timeout=250-10000 tickets=0 auth_mode=none \
+            "$P_SRV dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 auth_mode=none \
              psk=abc123 debug_level=3" \
-            "$P_CLI dtls=1 hs_timeout=250-10000 tickets=0 psk=abc123 \
+            "$P_CLI dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 psk=abc123 \
              debug_level=3 reconnect=1 read_timeout=1000 max_resend=10 \
              force_ciphersuite=TLS-PSK-WITH-AES-128-CCM-8" \
             0 \
@@ -5243,9 +6339,9 @@
 client_needs_more_time 4
 run_test    "DTLS proxy: 3d, min handshake, resumption, nbio" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
-            "$P_SRV dtls=1 hs_timeout=250-10000 tickets=0 auth_mode=none \
+            "$P_SRV dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 auth_mode=none \
              psk=abc123 debug_level=3 nbio=2" \
-            "$P_CLI dtls=1 hs_timeout=250-10000 tickets=0 psk=abc123 \
+            "$P_CLI dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 psk=abc123 \
              debug_level=3 reconnect=1 read_timeout=1000 max_resend=10 \
              force_ciphersuite=TLS-PSK-WITH-AES-128-CCM-8 nbio=2" \
             0 \
@@ -5258,9 +6354,9 @@
 requires_config_enabled MBEDTLS_SSL_RENEGOTIATION
 run_test    "DTLS proxy: 3d, min handshake, client-initiated renego" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
-            "$P_SRV dtls=1 hs_timeout=250-10000 tickets=0 auth_mode=none \
+            "$P_SRV dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 auth_mode=none \
              psk=abc123 renegotiation=1 debug_level=2" \
-            "$P_CLI dtls=1 hs_timeout=250-10000 tickets=0 psk=abc123 \
+            "$P_CLI dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 psk=abc123 \
              renegotiate=1 debug_level=2 \
              force_ciphersuite=TLS-PSK-WITH-AES-128-CCM-8" \
             0 \
@@ -5273,9 +6369,9 @@
 requires_config_enabled MBEDTLS_SSL_RENEGOTIATION
 run_test    "DTLS proxy: 3d, min handshake, client-initiated renego, nbio" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
-            "$P_SRV dtls=1 hs_timeout=250-10000 tickets=0 auth_mode=none \
+            "$P_SRV dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 auth_mode=none \
              psk=abc123 renegotiation=1 debug_level=2" \
-            "$P_CLI dtls=1 hs_timeout=250-10000 tickets=0 psk=abc123 \
+            "$P_CLI dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 psk=abc123 \
              renegotiate=1 debug_level=2 \
              force_ciphersuite=TLS-PSK-WITH-AES-128-CCM-8" \
             0 \
@@ -5288,10 +6384,10 @@
 requires_config_enabled MBEDTLS_SSL_RENEGOTIATION
 run_test    "DTLS proxy: 3d, min handshake, server-initiated renego" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
-            "$P_SRV dtls=1 hs_timeout=250-10000 tickets=0 auth_mode=none \
+            "$P_SRV dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 auth_mode=none \
              psk=abc123 renegotiate=1 renegotiation=1 exchanges=4 \
              debug_level=2" \
-            "$P_CLI dtls=1 hs_timeout=250-10000 tickets=0 psk=abc123 \
+            "$P_CLI dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 psk=abc123 \
              renegotiation=1 exchanges=4 debug_level=2 \
              force_ciphersuite=TLS-PSK-WITH-AES-128-CCM-8" \
             0 \
@@ -5304,10 +6400,10 @@
 requires_config_enabled MBEDTLS_SSL_RENEGOTIATION
 run_test    "DTLS proxy: 3d, min handshake, server-initiated renego, nbio" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
-            "$P_SRV dtls=1 hs_timeout=250-10000 tickets=0 auth_mode=none \
+            "$P_SRV dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 auth_mode=none \
              psk=abc123 renegotiate=1 renegotiation=1 exchanges=4 \
              debug_level=2 nbio=2" \
-            "$P_CLI dtls=1 hs_timeout=250-10000 tickets=0 psk=abc123 \
+            "$P_CLI dtls=1 dgram_packing=0 hs_timeout=250-10000 tickets=0 psk=abc123 \
              renegotiation=1 exchanges=4 debug_level=2 nbio=2 \
              force_ciphersuite=TLS-PSK-WITH-AES-128-CCM-8" \
             0 \
@@ -5321,7 +6417,7 @@
 run_test    "DTLS proxy: 3d, openssl server" \
             -p "$P_PXY drop=5 delay=5 duplicate=5 protect_hvr=1" \
             "$O_SRV -dtls1 -mtu 2048" \
-            "$P_CLI dtls=1 hs_timeout=250-60000 tickets=0" \
+            "$P_CLI dgram_packing=0 dtls=1 hs_timeout=250-60000 tickets=0" \
             0 \
             -c "HTTP/1.0 200 OK"
 
@@ -5330,7 +6426,7 @@
 run_test    "DTLS proxy: 3d, openssl server, fragmentation" \
             -p "$P_PXY drop=5 delay=5 duplicate=5 protect_hvr=1" \
             "$O_SRV -dtls1 -mtu 768" \
-            "$P_CLI dtls=1 hs_timeout=250-60000 tickets=0" \
+            "$P_CLI dgram_packing=0 dtls=1 hs_timeout=250-60000 tickets=0" \
             0 \
             -c "HTTP/1.0 200 OK"
 
@@ -5339,7 +6435,7 @@
 run_test    "DTLS proxy: 3d, openssl server, fragmentation, nbio" \
             -p "$P_PXY drop=5 delay=5 duplicate=5 protect_hvr=1" \
             "$O_SRV -dtls1 -mtu 768" \
-            "$P_CLI dtls=1 hs_timeout=250-60000 nbio=2 tickets=0" \
+            "$P_CLI dgram_packing=0 dtls=1 hs_timeout=250-60000 nbio=2 tickets=0" \
             0 \
             -c "HTTP/1.0 200 OK"
 
@@ -5349,7 +6445,7 @@
 run_test    "DTLS proxy: 3d, gnutls server" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
             "$G_SRV -u --mtu 2048 -a" \
-            "$P_CLI dtls=1 hs_timeout=250-60000" \
+            "$P_CLI dgram_packing=0 dtls=1 hs_timeout=250-60000" \
             0 \
             -s "Extra-header:" \
             -c "Extra-header:"
@@ -5360,7 +6456,7 @@
 run_test    "DTLS proxy: 3d, gnutls server, fragmentation" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
             "$G_SRV -u --mtu 512" \
-            "$P_CLI dtls=1 hs_timeout=250-60000" \
+            "$P_CLI dgram_packing=0 dtls=1 hs_timeout=250-60000" \
             0 \
             -s "Extra-header:" \
             -c "Extra-header:"
@@ -5371,7 +6467,7 @@
 run_test    "DTLS proxy: 3d, gnutls server, fragmentation, nbio" \
             -p "$P_PXY drop=5 delay=5 duplicate=5" \
             "$G_SRV -u --mtu 512" \
-            "$P_CLI dtls=1 hs_timeout=250-60000 nbio=2" \
+            "$P_CLI dgram_packing=0 dtls=1 hs_timeout=250-60000 nbio=2" \
             0 \
             -s "Extra-header:" \
             -c "Extra-header:"
diff --git a/tests/suites/test_suite_nist_kw.data b/tests/suites/test_suite_nist_kw.data
index eee4574..4462558 100644
--- a/tests/suites/test_suite_nist_kw.data
+++ b/tests/suites/test_suite_nist_kw.data
@@ -69,6 +69,27 @@
 NIST KW lengths #16 KWP unwrapping output buffer too short
 nist_kw_ciphertext_lengths:24:12:MBEDTLS_KW_MODE_KWP:MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA
 
+NIST KW lengths #17 KW plaintext NULL (2 to 2^54 - 1 semiblocks)
+nist_kw_plaintext_lengths:0:8:MBEDTLS_KW_MODE_KW:MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA
+
+NIST KW lengths #18 KW wrapping output NULL
+nist_kw_plaintext_lengths:8:0:MBEDTLS_KW_MODE_KW:MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA
+
+NIST KW lengths #19 KWP wrapping output NULL
+nist_kw_plaintext_lengths:8:0:MBEDTLS_KW_MODE_KWP:MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA
+
+NIST KW lengths #20 KW ciphertext NULL
+nist_kw_ciphertext_lengths:0:8:MBEDTLS_KW_MODE_KW:MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA
+
+NIST KW lengths #21 KWP ciphertext NULL
+nist_kw_ciphertext_lengths:0:8:MBEDTLS_KW_MODE_KWP:MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA
+
+NIST KW lengths #15 KW unwrapping output NULL
+nist_kw_ciphertext_lengths:32:0:MBEDTLS_KW_MODE_KW:MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA
+
+NIST KW lengths #16 KWP unwrapping output NULL
+nist_kw_ciphertext_lengths:24:0:MBEDTLS_KW_MODE_KWP:MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA
+
 NIST KW wrap AES-128 CAVS 17.4 PLAINTEXT LENGTH = 128 count 7
 depends_on:MBEDTLS_AES_C
 mbedtls_nist_kw_wrap:MBEDTLS_CIPHER_ID_AES:MBEDTLS_KW_MODE_KW:"095e293f31e317ba6861114b95c90792":"64349d506ae85ecd84459c7a5c423f55":"97de4425572274bd7fb2d6688d5afd4454d992348d42a643"
diff --git a/tests/suites/test_suite_nist_kw.function b/tests/suites/test_suite_nist_kw.function
index eb67c03..ae3ef80 100644
--- a/tests/suites/test_suite_nist_kw.function
+++ b/tests/suites/test_suite_nist_kw.function
@@ -158,19 +158,17 @@
 
     memset( key, 0, sizeof( key ) );
 
-    if (in_len == 0)
-    {
-        /* mbedtls_calloc can return NULL for zero-length buffers. Make sure we
-         * always have a plaintext buffer, even if the length is 0. */
-        plaintext = mbedtls_calloc( 1, 1 );
-    }
-    else
+    if( in_len != 0 )
     {
         plaintext = mbedtls_calloc( 1, in_len );
+        TEST_ASSERT( plaintext != NULL );
     }
-    TEST_ASSERT( plaintext != NULL );
-    ciphertext = mbedtls_calloc( 1, output_len );
-    TEST_ASSERT( ciphertext != NULL );
+
+    if( out_len != 0 )
+    {
+        ciphertext = mbedtls_calloc( 1, output_len );
+        TEST_ASSERT( ciphertext != NULL );
+    }
 
     memset( plaintext, 0, in_len );
     memset( ciphertext, 0, output_len );
@@ -216,10 +214,16 @@
 
     memset( key, 0, sizeof( key ) );
 
-    plaintext = mbedtls_calloc( 1, output_len );
-    TEST_ASSERT( plaintext != NULL );
-    ciphertext = mbedtls_calloc( 1, in_len );
-    TEST_ASSERT( ciphertext != NULL );
+    if( out_len != 0 )
+    {
+        plaintext = mbedtls_calloc( 1, output_len );
+        TEST_ASSERT( plaintext != NULL );
+    }
+    if( in_len != 0 )
+    {
+        ciphertext = mbedtls_calloc( 1, in_len );
+        TEST_ASSERT( ciphertext != NULL );
+    }
 
     memset( plaintext, 0, output_len );
     memset( ciphertext, 0, in_len );
diff --git a/tests/suites/test_suite_version.data b/tests/suites/test_suite_version.data
index 402c8b8..c3542e5 100644
--- a/tests/suites/test_suite_version.data
+++ b/tests/suites/test_suite_version.data
@@ -1,8 +1,8 @@
 Check compiletime library version
-check_compiletime_version:"2.12.0"
+check_compiletime_version:"2.13.1"
 
 Check runtime library version
-check_runtime_version:"2.12.0"
+check_runtime_version:"2.13.1"
 
 Check for MBEDTLS_VERSION_C
 check_feature:"MBEDTLS_VERSION_C":0