diff --git a/ChangeLog b/ChangeLog
index 690d693..5da19e8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,13 @@
 = mbed TLS x.x.x branch released xxxx-xx-xx
 
 Security
+   * Fix bug in DTLS handling of new associations with the same parameters
+     (RFC 6347 section 4.2.8): after sending its HelloVerifyRequest, the
+     server would end up with corrupted state and only send invalid records to
+     the client. An attacker able to send forged UDP packets to the server
+     could use that to obtain a Denial of Service. This could only happen when
+     MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE was enabled in config.h (which it is
+     by default).
    * Fix side channel in ECC code that allowed an adversary with access to
      precise enough timing and memory access information (typically an
      untrusted operating system attacking a secure enclave) to fully recover
diff --git a/Makefile b/Makefile
index 6014597..05e3606 100644
--- a/Makefile
+++ b/Makefile
@@ -111,8 +111,10 @@
 
 ## Editor navigation files
 C_SOURCE_FILES = $(wildcard include/*/*.h library/*.[hc] programs/*/*.[hc] tests/suites/*.function)
+# Exuberant-ctags invocation. Other ctags implementations may require different options.
+CTAGS = ctags --langmap=c:+.h.function -o
 tags: $(C_SOURCE_FILES)
-	ctags -o $@ $(C_SOURCE_FILES)
+	$(CTAGS) $@ $(C_SOURCE_FILES)
 TAGS: $(C_SOURCE_FILES)
 	etags -o $@ $(C_SOURCE_FILES)
 GPATH GRTAGS GSYMS GTAGS: $(C_SOURCE_FILES)
diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index 6586214..7b91604 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -525,6 +525,23 @@
 #error "MBEDTLS_SSL_PROTO_TLS1_2 defined, but not all prerequisites"
 #endif
 
+#if (defined(MBEDTLS_SSL_PROTO_SSL3) || defined(MBEDTLS_SSL_PROTO_TLS1) ||  \
+     defined(MBEDTLS_SSL_PROTO_TLS1_1) || defined(MBEDTLS_SSL_PROTO_TLS1_2)) && \
+    !(defined(MBEDTLS_KEY_EXCHANGE_RSA_ENABLED) ||                          \
+      defined(MBEDTLS_KEY_EXCHANGE_DHE_RSA_ENABLED) ||                      \
+      defined(MBEDTLS_KEY_EXCHANGE_ECDHE_RSA_ENABLED) ||                    \
+      defined(MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED) ||                  \
+      defined(MBEDTLS_KEY_EXCHANGE_ECDH_RSA_ENABLED) ||                     \
+      defined(MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA_ENABLED) ||                   \
+      defined(MBEDTLS_KEY_EXCHANGE_PSK_ENABLED) ||                          \
+      defined(MBEDTLS_KEY_EXCHANGE_DHE_PSK_ENABLED) ||                      \
+      defined(MBEDTLS_KEY_EXCHANGE_RSA_PSK_ENABLED) ||                      \
+      defined(MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED) ||                    \
+      defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED) )
+#error "One or more versions of the TLS protocol are enabled " \
+        "but no key exchange methods defined with MBEDTLS_KEY_EXCHANGE_xxxx"
+#endif
+
 #if defined(MBEDTLS_SSL_PROTO_DTLS)     && \
     !defined(MBEDTLS_SSL_PROTO_TLS1_1)  && \
     !defined(MBEDTLS_SSL_PROTO_TLS1_2)
@@ -648,6 +665,10 @@
 #error "MBEDTLS_X509_CREATE_C defined, but not all prerequisites"
 #endif
 
+#if defined(MBEDTLS_CERTS_C) && !defined(MBEDTLS_X509_USE_C)
+#error "MBEDTLS_CERTS_C defined, but not all prerequisites"
+#endif
+
 #if defined(MBEDTLS_X509_CRT_PARSE_C) && ( !defined(MBEDTLS_X509_USE_C) )
 #error "MBEDTLS_X509_CRT_PARSE_C defined, but not all prerequisites"
 #endif
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 1188e53..5f6ae62 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -3598,29 +3598,38 @@
     int ret;
     size_t len;
 
+    /* Use out_msg as temporary buffer for writing out HelloVerifyRequest,
+     * because the output buffer's already around. Don't use out_buf though,
+     * as we don't want to overwrite out_ctr. */
     ret = ssl_check_dtls_clihlo_cookie(
             ssl->conf->f_cookie_write,
             ssl->conf->f_cookie_check,
             ssl->conf->p_cookie,
             ssl->cli_id, ssl->cli_id_len,
             ssl->in_buf, ssl->in_left,
-            ssl->out_buf, MBEDTLS_SSL_MAX_CONTENT_LEN, &len );
+            ssl->out_msg, MBEDTLS_SSL_MAX_CONTENT_LEN, &len );
 
     MBEDTLS_SSL_DEBUG_RET( 2, "ssl_check_dtls_clihlo_cookie", ret );
 
     if( ret == MBEDTLS_ERR_SSL_HELLO_VERIFY_REQUIRED )
     {
+        int send_ret;
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "sending HelloVerifyRequest" ) );
+        MBEDTLS_SSL_DEBUG_BUF( 4, "output record sent to network",
+                                  ssl->out_msg, len );
         /* Don't check write errors as we can't do anything here.
          * If the error is permanent we'll catch it later,
          * if it's not, then hopefully it'll work next time. */
-        (void) ssl->f_send( ssl->p_bio, ssl->out_buf, len );
+        send_ret = ssl->f_send( ssl->p_bio, ssl->out_msg, len );
+        MBEDTLS_SSL_DEBUG_RET( 2, "ssl->f_send", send_ret );
+        (void) send_ret;
 
         return( MBEDTLS_ERR_SSL_HELLO_VERIFY_REQUIRED );
     }
 
     if( ret == 0 )
     {
-        /* Got a valid cookie, partially reset context */
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "cookie is valid, resetting context" ) );
         if( ( ret = ssl_session_reset_int( ssl, 1 ) ) != 0 )
         {
             MBEDTLS_SSL_DEBUG_RET( 1, "reset", ret );
diff --git a/library/x509.c b/library/x509.c
index 117c5fd..c12f7fb 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -1087,7 +1087,7 @@
     mbedtls_x509_crt_free( &clicert );
 #else
     ((void) verbose);
-#endif /* MBEDTLS_CERTS_C && MBEDTLS_SHA1_C */
+#endif /* MBEDTLS_CERTS_C && MBEDTLS_SHA256_C */
     return( ret );
 }
 
diff --git a/programs/test/udp_proxy.c b/programs/test/udp_proxy.c
index 02428b9..5b5809d 100644
--- a/programs/test/udp_proxy.c
+++ b/programs/test/udp_proxy.c
@@ -107,7 +107,8 @@
     "                        drop packets larger than N bytes\n"            \
     "    bad_ad=0/1          default: 0 (don't add bad ApplicationData)\n"  \
     "    protect_hvr=0/1     default: 0 (don't protect HelloVerifyRequest)\n" \
-    "    protect_len=%%d     default: (don't protect packets of this size)\n" \
+    "    protect_len=%%d      default: (don't protect packets of this size)\n" \
+    "    inject_clihlo=0/1   default: 0 (don't inject fake ClientHello)\n"  \
     "\n"                                                                    \
     "    seed=%%d             default: (use current time)\n"                \
     "\n"
@@ -130,7 +131,7 @@
     int bad_ad;                 /* inject corrupted ApplicationData record  */
     int protect_hvr;            /* never drop or delay HelloVerifyRequest   */
     int protect_len;            /* never drop/delay packet of the given size*/
-
+    int inject_clihlo;          /* inject fake ClientHello after handshake  */
     unsigned int seed;          /* seed for "random" events                 */
 } opt;
 
@@ -219,6 +220,12 @@
             if( opt.protect_len < 0 )
                 exit_usage( p, q );
         }
+        else if( strcmp( p, "inject_clihlo" ) == 0 )
+        {
+            opt.inject_clihlo = atoi( q );
+            if( opt.inject_clihlo < 0 || opt.inject_clihlo > 1 )
+                exit_usage( p, q );
+        }
         else if( strcmp( p, "seed" ) == 0 )
         {
             opt.seed = atoi( q );
@@ -311,11 +318,41 @@
     fflush( stdout );
 }
 
+/*
+ * In order to test the server's behaviour when receiving a ClientHello after
+ * the connection is established (this could be a hard reset from the client,
+ * but the server must not drop the existing connection before establishing
+ * client reachability, see RFC 6347 Section 4.2.8), we memorize the first
+ * ClientHello we see (which can't have a cookie), then replay it after the
+ * first ApplicationData record - then we're done.
+ *
+ * This is controlled by the inject_clihlo option.
+ *
+ * We want an explicit state and a place to store the packet.
+ */
+typedef enum {
+    ICH_INIT,       /* haven't seen the first ClientHello yet */
+    ICH_CACHED,     /* cached the initial ClientHello */
+    ICH_INJECTED,   /* ClientHello already injected, done */
+} inject_clihlo_state_t;
+
+static inject_clihlo_state_t inject_clihlo_state;
+static packet initial_clihlo;
+
 int send_packet( const packet *p, const char *why )
 {
     int ret;
     mbedtls_net_context *dst = p->dst;
 
+    /* save initial ClientHello? */
+    if( opt.inject_clihlo != 0 &&
+        inject_clihlo_state == ICH_INIT &&
+        strcmp( p->type, "ClientHello" ) == 0 )
+    {
+        memcpy( &initial_clihlo, p, sizeof( packet ) );
+        inject_clihlo_state = ICH_CACHED;
+    }
+
     /* insert corrupted ApplicationData record? */
     if( opt.bad_ad &&
         strcmp( p->type, "ApplicationData" ) == 0 )
@@ -353,6 +390,23 @@
         }
     }
 
+    /* Inject ClientHello after first ApplicationData */
+    if( opt.inject_clihlo != 0 &&
+        inject_clihlo_state == ICH_CACHED &&
+        strcmp( p->type, "ApplicationData" ) == 0 )
+    {
+        print_packet( &initial_clihlo, "injected" );
+
+        if( ( ret = mbedtls_net_send( dst, initial_clihlo.buf,
+                                           initial_clihlo.len ) ) <= 0 )
+        {
+            mbedtls_printf( "  ! mbedtls_net_send returned %d\n", ret );
+            return( ret );
+        }
+
+        inject_clihlo_state = ICH_INJECTED;
+    }
+
     return( 0 );
 }
 
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 1434156..f304fdc 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -4972,8 +4972,8 @@
 
 not_with_valgrind # spurious resend
 run_test    "DTLS client reconnect from same port: reference" \
-            "$P_SRV dtls=1 exchanges=2 read_timeout=1000" \
-            "$P_CLI dtls=1 exchanges=2 debug_level=2 hs_timeout=500-1000" \
+            "$P_SRV dtls=1 exchanges=2 read_timeout=20000 hs_timeout=10000-20000" \
+            "$P_CLI dtls=1 exchanges=2 debug_level=2 hs_timeout=10000-20000" \
             0 \
             -C "resend" \
             -S "The operation timed out" \
@@ -4981,8 +4981,8 @@
 
 not_with_valgrind # spurious resend
 run_test    "DTLS client reconnect from same port: reconnect" \
-            "$P_SRV dtls=1 exchanges=2 read_timeout=1000" \
-            "$P_CLI dtls=1 exchanges=2 debug_level=2 hs_timeout=500-1000 reconnect_hard=1" \
+            "$P_SRV dtls=1 exchanges=2 read_timeout=20000 hs_timeout=10000-20000" \
+            "$P_CLI dtls=1 exchanges=2 debug_level=2 hs_timeout=10000-20000 reconnect_hard=1" \
             0 \
             -C "resend" \
             -S "The operation timed out" \
@@ -5011,6 +5011,14 @@
             -s "The operation timed out" \
             -S "Client initiated reconnection from same port"
 
+run_test    "DTLS client reconnect from same port: attacker-injected" \
+            -p "$P_PXY inject_clihlo=1" \
+            "$P_SRV dtls=1 exchanges=2 debug_level=1" \
+            "$P_CLI dtls=1 exchanges=2" \
+            0 \
+            -s "possible client reconnect from the same port" \
+            -S "Client initiated reconnection from same port"
+
 # Tests for various cases of client authentication with DTLS
 # (focused on handshake flows and message parsing)
 
@@ -5135,8 +5143,8 @@
 not_with_valgrind # spurious resend due to timeout
 run_test    "DTLS proxy: reference" \
             -p "$P_PXY" \
-            "$P_SRV dtls=1 debug_level=2" \
-            "$P_CLI dtls=1 debug_level=2" \
+            "$P_SRV dtls=1 debug_level=2 hs_timeout=10000-20000" \
+            "$P_CLI dtls=1 debug_level=2 hs_timeout=10000-20000" \
             0 \
             -C "replayed record" \
             -S "replayed record" \
@@ -5151,8 +5159,8 @@
 not_with_valgrind # spurious resend due to timeout
 run_test    "DTLS proxy: duplicate every packet" \
             -p "$P_PXY duplicate=1" \
-            "$P_SRV dtls=1 debug_level=2" \
-            "$P_CLI dtls=1 debug_level=2" \
+            "$P_SRV dtls=1 debug_level=2 hs_timeout=10000-20000" \
+            "$P_CLI dtls=1 debug_level=2 hs_timeout=10000-20000" \
             0 \
             -c "replayed record" \
             -s "replayed record" \
diff --git a/tests/suites/main_test.function b/tests/suites/main_test.function
index 042085f..8f134ff 100644
--- a/tests/suites/main_test.function
+++ b/tests/suites/main_test.function
@@ -348,7 +348,7 @@
           testfile_index++ )
     {
         int unmet_dep_count = 0;
-        char *unmet_dependencies[20];
+        char *unmet_dependencies[20]; /* only filled when verbose != 0 */
 
         test_filename = test_files[ testfile_index ];
 
@@ -369,6 +369,7 @@
                 mbedtls_exit( MBEDTLS_EXIT_FAILURE );
             }
             unmet_dep_count = 0;
+            memset( unmet_dependencies, 0, sizeof( unmet_dependencies ) );
 
             if( ( ret = get_line( file, buf, sizeof(buf) ) ) != 0 )
                 break;
@@ -391,18 +392,16 @@
                 {
                     if( dep_check( params[i] ) != DEPENDENCY_SUPPORTED )
                     {
-                        if( 0 == option_verbose )
+                        if( 0 != option_verbose )
                         {
-                            /* Only one count is needed if not verbose */
-                            unmet_dep_count++;
-                            break;
-                        }
-
-                        unmet_dependencies[ unmet_dep_count ] = strdup(params[i]);
-                        if(  unmet_dependencies[ unmet_dep_count ] == NULL )
-                        {
-                            mbedtls_fprintf( stderr, "FATAL: Out of memory\n" );
-                            mbedtls_exit( MBEDTLS_EXIT_FAILURE );
+                            unmet_dependencies[unmet_dep_count] =
+                                strdup( params[i] );
+                            if(  unmet_dependencies[unmet_dep_count] == NULL )
+                            {
+                                mbedtls_fprintf( stderr,
+                                                 "FATAL: Out of memory\n" );
+                                mbedtls_exit( MBEDTLS_EXIT_FAILURE );
+                            }
                         }
                         unmet_dep_count++;
                     }