diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index 764fba4..29d9906 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -671,6 +671,18 @@
 #define "MBEDTLS_SSL_CONF_EXTENDED_MASTER_SECRET and MBEDTLS_SSL_CONF_ENFORCE_EXTENDED_MASTER_SECRET must be defined together."
 #endif
 
+#if ( defined(MBEDTLS_SSL_CONF_SEND) &&                 \
+      !( defined(MBEDTLS_SSL_CONF_RECV) &&              \
+         defined(MBEDTLS_SSL_CONF_RECV_TIMEOUT) ) ) ||  \
+    ( defined(MBEDTLS_SSL_CONF_RECV) &&                 \
+      !( defined(MBEDTLS_SSL_CONF_SEND) &&              \
+         defined(MBEDTLS_SSL_CONF_RECV_TIMEOUT) ) ) ||  \
+    ( defined(MBEDTLS_SSL_CONF_RECV_TIMEOUT) &&         \
+      !( defined(MBEDTLS_SSL_CONF_SEND) &&              \
+         defined(MBEDTLS_SSL_CONF_RECV) ) )
+#define "MBEDTLS_SSL_CONF_SEND/RECV/RECV_TIMEOUT must be defined simultaneously"
+#endif
+
 #if defined(MBEDTLS_SSL_TICKET_C) && !defined(MBEDTLS_CIPHER_C)
 #error "MBEDTLS_SSL_TICKET_C defined, but not all prerequisites"
 #endif
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 597f2a3..a767cb2 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -3601,6 +3601,22 @@
 //#define MBEDTLS_SSL_CONF_CID_LEN 0
 //#define MBEDTLS_SSL_CONF_IGNORE_UNEXPECTED_CID MBEDTLS_SSL_UNEXPECTED_CID_IGNORE
 
+/* The send and receive callbacks to use by the SSL module.
+ * If defined,
+ * - MBEDTLS_SSL_CONF_RECV must evaluate to the name of an externally
+ *   defined function with signature
+ *      int (*f_recv)( void*, unsigned char *, size_t ),
+ * * MBEDTLS_SSL_CONF_SEND must evaluate to the name of an externally
+ *   defined function with signature
+ *      int (*f_send)( void*, const unsigned char *, size_t ),
+ * * MBEDTLS_SSL_CONF_RECV_TIMEOUT must evaluate to the name of an
+ * externally defined function with signature
+ *      int (*f_recv_timeout)( void*, const unsigned char *, size_t, uint32_t ).
+ */
+//#define MBEDTLS_SSL_CONF_RECV mbedtls_net_recv
+//#define MBEDTLS_SSL_CONF_SEND mbedtls_net_send
+//#define MBEDTLS_SSL_CONF_RECV_TIMEOUT mbedtls_net_recv_timeout
+
 /* The PRNG to use by the SSL module. If defined, this must
  * evaluate to the name on externally defined function with signature
  * int (*f_rng)(void *, unsigned char *, size_t),
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 7364dc4..671d107 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1146,9 +1146,15 @@
     unsigned badmac_seen;       /*!< records with a bad MAC received    */
 #endif /* MBEDTLS_SSL_DTLS_BADMAC_LIMIT */
 
+#if !defined(MBEDTLS_SSL_CONF_SEND)
     mbedtls_ssl_send_t *f_send; /*!< Callback for network send */
+#endif /* !MBEDTLS_SSL_CONF_SEND */
+#if !defined(MBEDTLS_SSL_CONF_RECV)
     mbedtls_ssl_recv_t *f_recv; /*!< Callback for network receive */
+#endif /* !MBEDTLS_SSL_CONF_RECV */
+#if !defined(MBEDTLS_SSL_CONF_RECV_TIMEOUT)
     mbedtls_ssl_recv_timeout_t *f_recv_timeout;
+#endif /* !MBEDTLS_SSL_CONF_RECV_TIMEOUT */
                                 /*!< Callback for network receive with timeout */
 
     void *p_bio;                /*!< context for I/O operations   */
@@ -1510,6 +1516,9 @@
                   void (*f_dbg)(void *, int, const char *, int, const char *),
                   void  *p_dbg );
 
+#if !defined(MBEDTLS_SSL_CONF_RECV) && \
+    !defined(MBEDTLS_SSL_CONF_SEND) && \
+    !defined(MBEDTLS_SSL_CONF_RECV_TIMEOUT)
 /**
  * \brief          Set the underlying BIO callbacks for write, read and
  *                 read-with-timeout.
@@ -1535,6 +1544,13 @@
  *                 \c mbedtls_ssl_recv_t and \c mbedtls_ssl_recv_timeout_t for
  *                 the conventions those callbacks must follow.
  *
+ * \note           On constrained systems, the pointers \p f_send, \p f_recv,
+ *                 and \p f_recv_timeout can also be configured at compile-time
+ *                 via the macros MBEDTLS_SSL_CONF_RECV, MBEDTLS_SSL_CONF_SEND
+ *                 and MBEDTLS_SSL_CONF_RECV_TIMEOUT. In this case, the
+ *                 corresponding parameters to this function don't take
+ *                 any effect.
+ *
  * \note           On some platforms, net_sockets.c provides
  *                 \c mbedtls_net_send(), \c mbedtls_net_recv() and
  *                 \c mbedtls_net_recv_timeout() that are suitable to be used
@@ -1545,6 +1561,18 @@
                           mbedtls_ssl_send_t *f_send,
                           mbedtls_ssl_recv_t *f_recv,
                           mbedtls_ssl_recv_timeout_t *f_recv_timeout );
+#else
+/**
+ * \brief          Set the context to be passed to the underlying BIO callbacks
+ *                 for write, read and read-with-timeout.
+ *
+ * \param ssl      The SSL context to configure.
+ * \param p_bio    The parameter (context) to be used for the BIO callbacks.
+ *
+ */
+void mbedtls_ssl_set_bio_ctx( mbedtls_ssl_context *ssl,
+                              void *p_bio );
+#endif
 
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
 
diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index 52835b4..8d5170c 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -1291,8 +1291,68 @@
 
 typedef int (*mbedtls_frng_t)( void*, unsigned char*, size_t );
 
+#if !defined(MBEDTLS_SSL_CONF_RECV)
+static inline mbedtls_ssl_recv_t* mbedtls_ssl_get_recv(
+    mbedtls_ssl_context const *ssl )
+{
+    return( ssl->f_recv );
+}
+#else /* !MBEDTLS_SSL_CONF_RECV */
+
+#define mbedtls_ssl_conf_recv_func MBEDTLS_SSL_CONF_RECV
+extern int mbedtls_ssl_conf_recv_func( void*, unsigned char*, size_t );
+
+static inline mbedtls_ssl_recv_t* mbedtls_ssl_get_recv(
+    mbedtls_ssl_context const *ssl )
+{
+    ((void) ssl);
+    return ((mbedtls_ssl_recv_t*) mbedtls_ssl_conf_recv_func);
+}
+#endif /* MBEDTLS_SSL_CONF_RECV */
+
+#if !defined(MBEDTLS_SSL_CONF_SEND)
+static inline mbedtls_ssl_send_t* mbedtls_ssl_get_send(
+    mbedtls_ssl_context const *ssl )
+{
+    return( ssl->f_send );
+}
+#else /* !MBEDTLS_SSL_CONF_SEND */
+
+#define mbedtls_ssl_conf_send_func MBEDTLS_SSL_CONF_SEND
+extern int mbedtls_ssl_conf_send_func( void*, unsigned char const*, size_t );
+
+static inline mbedtls_ssl_send_t* mbedtls_ssl_get_send(
+    mbedtls_ssl_context const *ssl )
+{
+    ((void) ssl);
+    return ((mbedtls_ssl_send_t*) mbedtls_ssl_conf_send_func);
+}
+#endif /* MBEDTLS_SSL_CONF_SEND */
+
+#if !defined(MBEDTLS_SSL_CONF_RECV_TIMEOUT)
+static inline mbedtls_ssl_recv_timeout_t* mbedtls_ssl_get_recv_timeout(
+    mbedtls_ssl_context const *ssl )
+{
+    return( ssl->f_recv_timeout );
+}
+#else /* !MBEDTLS_SSL_CONF_RECV_TIMEOUT */
+
+#define mbedtls_ssl_conf_recv_timeout_func MBEDTLS_SSL_CONF_RECV_TIMEOUT
+extern int mbedtls_ssl_conf_recv_timeout_func(
+    void*, unsigned char*, size_t, uint32_t );
+
+static inline mbedtls_ssl_recv_timeout_t* mbedtls_ssl_get_recv_timeout(
+    mbedtls_ssl_context const *ssl )
+{
+    ((void) ssl);
+    return ((mbedtls_ssl_recv_timeout_t*) mbedtls_ssl_conf_recv_timeout_func);
+}
+#endif /* MBEDTLS_SSL_CONF_RECV_TIMEOUT */
+
+typedef int mbedtls_frng_t( void*, unsigned char*, size_t );
+
 #if !defined(MBEDTLS_SSL_CONF_RNG)
-static inline mbedtls_frng_t mbedtls_ssl_conf_get_frng(
+static inline mbedtls_frng_t* mbedtls_ssl_conf_get_frng(
     mbedtls_ssl_config const *conf )
 {
     return( conf->f_rng );
@@ -1302,7 +1362,7 @@
 #define mbedtls_ssl_conf_rng_func MBEDTLS_SSL_CONF_RNG
 extern int mbedtls_ssl_conf_rng_func( void*, unsigned char*, size_t );
 
-static inline mbedtls_frng_t mbedtls_ssl_conf_get_frng(
+static inline mbedtls_frng_t* mbedtls_ssl_conf_get_frng(
     mbedtls_ssl_config const *conf )
 {
     ((void) conf);