Merge branch 'iotssl-165-dtls-hs-fragmentation-new' into datagram_packing

ChangeLog

@@ -5,9 +5,8 @@ mbed TLS ChangeLog (Sorted per branch, date)
 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 new per-connection MTU option, set using
+     with the peer, as well as by a new per-connection MTU option, set using
      mbedtls_ssl_set_mtu().
-   * Add support for fragmentation of outoing DTLS handshake messages.
    * Add support for packing multiple records within a single datagram,
      enabled by default.
 

include/mbedtls/ssl.h

@@ -1395,23 +1395,28 @@ void mbedtls_ssl_set_bio( mbedtls_ssl_context *ssl,
  *                 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 PMTU estimate becomes available from other
  *                 sources, such as lower (or higher) protocol layers.
  *
- * \note           This only controls the size of the packets we send.
- *                 Client-side, you can request the server to use smaller
- *                 records with \c mbedtls_ssl_conf_max_frag_len().
+ * \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 (after translating the MTU setting to a limit
- *                 on the record content length) is used.
+ *                 lower limit on record payload (see first note) is used.
  *
  * \note           This can only be used to decrease the maximum size
- *                 of datagrams sent. It cannot be used to increase the
- *                 maximum size of records over the limit set by
- *                 #MBEDTLS_SSL_OUT_CONTENT_LEN.
+ *                 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.

library/ssl_tls.c

@@ -7323,6 +7323,11 @@ 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 );
 

tests/ssl-opt.sh

@@ -5144,6 +5144,8 @@ run_test    "DTLS fragmenting: both (MTU)" \
             -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
@@ -5160,7 +5162,26 @@ run_test    "DTLS fragmenting: proxy MTU, simple handshake" \
              mtu=512" \
             0 \
             -S "resend" \
-            -C "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" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             mtu=512 nbio=2" \
+            0 \
+            -S "resend" \
             -s "found fragmented DTLS handshake message" \
             -c "found fragmented DTLS handshake message" \
             -C "error"
@@ -5171,9 +5192,10 @@ run_test    "DTLS fragmenting: proxy MTU, simple handshake" \
 # Since we don't support reading fragmented ClientHello yet,
 # up the MTU to 1450 (larger than ClientHello with session ticket,
 # but still smaller than client's Certificate to ensure fragmentation).
-#
 # A resend on the client-side might happen if the server is
 # slow to reset, therefore omitting '-C "resend"' below.
+# reco_delay avoids races where the client reconnects before the server has
+# resumed listening, which would result in a spurious resend.
 not_with_valgrind # spurious resend due to timeout
 requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
 requires_config_enabled MBEDTLS_RSA_C
@@ -5187,7 +5209,7 @@ run_test    "DTLS fragmenting: proxy MTU, resumed handshake" \
             "$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" \
+             mtu=1450 reconnect=1 reco_delay=1" \
             0 \
             -S "resend" \
             -s "found fragmented DTLS handshake message" \
@@ -5363,6 +5385,25 @@ run_test    "DTLS fragmenting: proxy MTU + 3d" \
             -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" \
+            "$P_CLI dtls=1 debug_level=2 \
+             crt_file=data_files/server8_int-ca2.crt \
+             key_file=data_files/server8.key \
+             hs_timeout=250-10000 mtu=512 nbio=2" \
+            0 \
+            -s "found fragmented DTLS handshake message" \
+            -c "found fragmented DTLS handshake message" \
+            -C "error"
+
 # interop tests for DTLS fragmentating with reliable connection
 #
 # here and below we just want to test that the we fragment in a way that
@@ -5372,6 +5413,7 @@ requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
 requires_config_enabled MBEDTLS_RSA_C
 requires_config_enabled MBEDTLS_ECDSA_C
 requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_2
+requires_gnutls
 run_test    "DTLS fragmenting: gnutls server, DTLS 1.2" \
             "$G_SRV -u" \
             "$P_CLI dtls=1 debug_level=2 \
@@ -5387,6 +5429,7 @@ requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
 requires_config_enabled MBEDTLS_RSA_C
 requires_config_enabled MBEDTLS_ECDSA_C
 requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_1
+requires_gnutls
 run_test    "DTLS fragmenting: gnutls server, DTLS 1.0" \
             "$G_SRV -u" \
             "$P_CLI dtls=1 debug_level=2 \
@@ -5403,6 +5446,7 @@ requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
 requires_config_enabled MBEDTLS_RSA_C
 requires_config_enabled MBEDTLS_ECDSA_C
 requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_2
+requires_gnutls
 run_test    "DTLS fragmenting: gnutls client, DTLS 1.2" \
             "$P_SRV dtls=1 debug_level=2 server_addr=::1 \
              crt_file=data_files/server7_int-ca.crt \
@@ -5418,6 +5462,7 @@ 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 server_addr=::1 \
              crt_file=data_files/server7_int-ca.crt \
@@ -5527,6 +5572,7 @@ run_test    "DTLS fragmenting: 3d, gnutls server, DTLS 1.0" \
 ##
 ## # gnutls-cli always tries IPv6 first, and doesn't fall back to IPv4 with DTLS
 ## requires_ipv6
+## requires_gnutls
 ## requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
 ## requires_config_enabled MBEDTLS_RSA_C
 ## requires_config_enabled MBEDTLS_ECDSA_C
@@ -5544,6 +5590,7 @@ run_test    "DTLS fragmenting: 3d, gnutls server, DTLS 1.0" \
 ##
 ## # gnutls-cli always tries IPv6 first, and doesn't fall back to IPv4 with DTLS
 ## requires_ipv6
+## requires_gnutls
 ## requires_config_enabled MBEDTLS_SSL_PROTO_DTLS
 ## requires_config_enabled MBEDTLS_RSA_C
 ## requires_config_enabled MBEDTLS_ECDSA_C