DTLS Nonblocking Updates

1. Add error code for trying to retransmit a flight when transmitting
the flight hasn't finished.
2. Add function to retransmit the stored flight without updating the
timeout count.

src/internal.c

@@ -15836,6 +15836,9 @@ const char* wolfSSL_ERR_reason_error_string(unsigned long e)
     case EXT_MISSING:
         return "Required TLS extension missing";
 
+    case DTLS_RETX_OVER_TX:
+        return "DTLS interrupting flight transmit with retransmit";
+
     default :
         return "unknown error number";
     }

src/ssl.c

@@ -8827,6 +8827,27 @@ int wolfSSL_dtls_got_timeout(WOLFSSL* ssl)
     return result;
 }
 
+
+/* retransmit all the saves messages, WOLFSSL_SUCCESS on ok */
+int wolfSSL_dtls_retransmit(WOLFSSL* ssl)
+{
+    WOLFSSL_ENTER("wolfSSL_dtls_retransmit()");
+
+    if (ssl == NULL)
+        return WOLFSSL_FATAL_ERROR;
+
+    if (!ssl->options.handShakeDone) {
+        int result = DtlsMsgPoolSend(ssl, 0);
+        if (result < 0) {
+            ssl->error = result;
+            WOLFSSL_ERROR(result);
+            return WOLFSSL_FATAL_ERROR;
+        }
+    }
+
+    return 0;
+}
+
 #endif /* DTLS */
 #endif /* LEANPSK */
 

wolfssl/error-ssl.h

@@ -163,6 +163,7 @@ enum wolfSSL_ErrorCodes {
     EXT_MISSING                  = -428,   /* Required extension not found */
     UNSUPPORTED_EXTENSION        = -429,   /* TLSX not requested by client */
     PRF_MISSING                  = -430,   /* PRF not compiled in */
+    DTLS_RETX_OVER_TX            = -431,   /* Retransmit DTLS flight over */
     /* add strings to wolfSSL_ERR_reason_error_string in internal.c !!!!! */
 
     /* begin negotiation parameter errors */

wolfssl/ssl.h

@@ -723,6 +723,7 @@ WOLFSSL_API int  wolfSSL_dtls_get_current_timeout(WOLFSSL* ssl);
 WOLFSSL_API int  wolfSSL_dtls_set_timeout_init(WOLFSSL* ssl, int);
 WOLFSSL_API int  wolfSSL_dtls_set_timeout_max(WOLFSSL* ssl, int);
 WOLFSSL_API int  wolfSSL_dtls_got_timeout(WOLFSSL* ssl);
+WOLFSSL_API int  wolfSSL_dtls_retransmit(WOLFSSL*);
 WOLFSSL_API int  wolfSSL_dtls(WOLFSSL* ssl);
 
 WOLFSSL_API int  wolfSSL_dtls_set_peer(WOLFSSL*, void*, unsigned int);