Allow setting of MTU in DTLS

configure.ac

@@ -275,6 +275,17 @@ then
   AM_CFLAGS="-DWOLFSSL_DTLS $AM_CFLAGS"
 fi
 
+# DTLS change MTU
+AC_ARG_ENABLE([dtls-mtu],
+    [AS_HELP_STRING([--enable-dtls-mtu],[Enable setting the MTU size for wolfSSL DTLS (default: disabled)])],
+    [ ENABLED_DTLS_MTU=$enableval ],
+    [ ENABLED_DTLS_MTU=no ]
+    )
+if test "$ENABLED_DTLS_MTU" = "yes"
+then
+  AM_CFLAGS="-DWOLFSSL_DTLS_MTU $AM_CFLAGS"
+fi
+
 
 # TLS v1.3 Draft 18
 AC_ARG_ENABLE([tls13-draft18],

src/internal.c

@@ -1740,8 +1740,12 @@ int InitSSL_Ctx(WOLFSSL_CTX* ctx, WOLFSSL_METHOD* method, void* heap)
 
     ctx->devId = INVALID_DEVID;
 
-#if defined(WOLFSSL_DTLS) && defined(WOLFSSL_SCTP)
+#if defined(WOLFSSL_DTLS)
-    ctx->dtlsMtuSz = MAX_RECORD_SIZE;
+    #ifdef WOLFSSL_SCTP
+        ctx->dtlsMtuSz = MAX_RECORD_SIZE;
+    #elif defined(WOLFSSL_DTLS_MTU)
+        ctx->dtlsMtuSz = MAX_MTU;
+    #endif
 #endif
 
 #ifndef NO_CERTS
@@ -5649,6 +5653,8 @@ int InitSSL(WOLFSSL* ssl, WOLFSSL_CTX* ctx, int writeDup)
 #ifdef WOLFSSL_DTLS
     #ifdef WOLFSSL_SCTP
         ssl->options.dtlsSctp           = ctx->dtlsSctp;
+    #endif
+    #if defined(WOLFSSL_SCTP) || defined(WOLFSSL_DTLS_MTU)
         ssl->dtlsMtuSz                  = ctx->dtlsMtuSz;
         ssl->dtls_expected_rx           = ssl->dtlsMtuSz;
     #else

src/ssl.c

@@ -1076,6 +1076,10 @@ int wolfSSL_dtls_set_sctp(WOLFSSL* ssl)
     return WOLFSSL_SUCCESS;
 }
 
+#endif /* WOLFSSL_DTLS && WOLFSSL_SCTP */
+
+#if (defined(WOLFSSL_SCTP) || defined(WOLFSSL_DTLS_MTU)) && \
+                                                           defined(WOLFSSL_DTLS)
 
 int wolfSSL_CTX_dtls_set_mtu(WOLFSSL_CTX* ctx, word16 newMtu)
 {
@@ -1101,8 +1105,7 @@ int wolfSSL_dtls_set_mtu(WOLFSSL* ssl, word16 newMtu)
     return WOLFSSL_SUCCESS;
 }
 
-
+#endif /* WOLFSSL_DTLS && (WOLFSSL_SCTP || WOLFSSL_DTLS_MTU) */
-#endif /* WOLFSSL_DTLS && WOLFSSL_SCTP */
 
 
 #ifdef WOLFSSL_DTLS_DROP_STATS
@@ -2023,6 +2026,8 @@ static int wolfSSL_read_internal(WOLFSSL* ssl, void* data, int sz, int peek)
         ssl->dtls_expected_rx = max(sz + 100, MAX_MTU);
 #ifdef WOLFSSL_SCTP
         if (ssl->options.dtlsSctp)
+#endif
+#if defined(WOLLSSL_SCTP) || defined(WOLFSSL_DTLS_MTU)
             ssl->dtls_expected_rx = max(ssl->dtls_expected_rx, ssl->dtlsMtuSz);
 #endif
     }

tests/api.c

@@ -31296,6 +31296,47 @@ static void test_SetTmpEC_DHE_Sz(void)
 #endif
 }
 
+static void test_wolfSSL_dtls_set_mtu(void)
+{
+#if (defined(WOLFSSL_DTLS_MTU) || defined(WOLFSSL_SCTP)) && \
+                                                           defined(WOLFSSL_DTLS)
+    WOLFSSL_CTX* ctx = NULL;
+    WOLFSSL*     ssl = NULL;
+    const char* testCertFile;
+    const char* testKeyFile;
+
+    AssertNotNull(ctx = wolfSSL_CTX_new(wolfDTLSv1_2_server_method()));
+#ifndef NO_RSA
+	testCertFile = svrCertFile;
+	testKeyFile = svrKeyFile;
+#elif defined(HAVE_ECC)
+	testCertFile = eccCertFile;
+	testKeyFile = eccKeyFile;
+#endif
+    if  (testCertFile != NULL && testKeyFile != NULL) {
+        AssertTrue(wolfSSL_CTX_use_certificate_file(ctx, testCertFile,
+                                                    WOLFSSL_FILETYPE_PEM));
+        AssertTrue(wolfSSL_CTX_use_PrivateKey_file(ctx, testKeyFile,
+                                                   WOLFSSL_FILETYPE_PEM));
+    }
+    AssertNotNull(ssl = wolfSSL_new(ctx));
+
+    AssertIntEQ(wolfSSL_CTX_dtls_set_mtu(NULL, 1488), BAD_FUNC_ARG);
+    AssertIntEQ(wolfSSL_dtls_set_mtu(NULL, 1488), BAD_FUNC_ARG);
+    AssertIntEQ(wolfSSL_CTX_dtls_set_mtu(ctx, 20000), BAD_FUNC_ARG);
+    AssertIntEQ(wolfSSL_dtls_set_mtu(ssl, 20000), WOLFSSL_FAILURE);
+    AssertIntEQ(wolfSSL_get_error(ssl, WOLFSSL_FAILURE), BAD_FUNC_ARG);
+    AssertIntEQ(wolfSSL_CTX_dtls_set_mtu(ctx, 1488), WOLFSSL_SUCCESS);
+    AssertIntEQ(wolfSSL_dtls_set_mtu(ssl, 1488), WOLFSSL_SUCCESS);
+
+    wolfSSL_free(ssl);
+    wolfSSL_CTX_free(ctx);
+
+    printf(testingFmt, "wolfSSL_dtls_set_mtu()");
+    printf(resultFmt, passed);
+#endif
+}
+
 #if !defined(NO_RSA) && !defined(NO_SHA) && !defined(NO_FILESYSTEM) && \
     !defined(NO_CERTS)
 static int load_ca_into_cm(WOLFSSL_CERT_MANAGER* cm, char* certA)
@@ -31598,6 +31639,7 @@ void ApiTest(void)
     test_wolfSSL_SetTmpDH_buffer();
     test_wolfSSL_SetMinMaxDhKey_Sz();
     test_SetTmpEC_DHE_Sz();
+    test_wolfSSL_dtls_set_mtu();
 #if !defined(NO_WOLFSSL_CLIENT) && !defined(NO_WOLFSSL_SERVER) && \
     defined(HAVE_IO_TESTS_DEPENDENCIES)
     test_wolfSSL_read_write();

wolfssl/internal.h

@@ -2684,6 +2684,9 @@ struct WOLFSSL_CTX {
 #endif
 #if defined(WOLFSSL_SCTP) && defined(WOLFSSL_DTLS)
     byte        dtlsSctp;         /* DTLS-over-SCTP mode */
+#endif
+#if (defined(WOLFSSL_SCTP) || defined(WOLFSSL_DTLS_MTU)) && \
+                                                           defined(WOLFSSL_DTLS)
     word16      dtlsMtuSz;        /* DTLS MTU size */
 #endif
 #ifndef NO_DH
@@ -4021,9 +4024,9 @@ struct WOLFSSL {
 #ifdef WOLFSSL_SESSION_EXPORT
     wc_dtls_export  dtls_export;        /* export function for session */
 #endif
-#ifdef WOLFSSL_SCTP
+#if defined(WOLFSSL_SCTP) || defined(WOLFSSL_DTLS_MTU)
     word16          dtlsMtuSz;
-#endif /* WOLFSSL_SCTP */
+#endif /* WOLFSSL_SCTP || WOLFSSL_DTLS_MTU */
 #ifdef WOLFSSL_MULTICAST
     void*           mcastHwCbCtx;       /* Multicast highwater callback ctx */
 #endif /* WOLFSSL_MULTICAST */