Merge pull request #288 from anhu/caveat

Add a short caveat to client-tls13-resume.c

tls/client-tls13-resume.c

@@ -228,7 +228,22 @@ int main(int argc, char** argv)
     wolfSSL_FreeArrays(ssl);
 #endif
 
-    /* Save the session */
+#if 0
+    /* Save the session
+     *
+     * NOTE: This is not an ideal solution. Please see below where we call
+     * wolfSSL_get_session() just before disconnection. We do not need to
+     * call wolfSSL_peek() in that case because we have already called
+     * wolfSSL_read() so wolfSSL has already internally stored the session
+     * ticket. For TLS 1.2 it is fine to put wolfSSL_get_session() right after
+     * the connection is established because the resumption information is part
+     * of the TLS 1.2 handshake. This is not the case for TLS 1.3. However, if
+     * you are migrating from TLS 1.2 and are having a hard time moving your
+     * call to wolfSSL_get_session(), you can try this approach.
+     *
+     * This approach can result in issues with I/O and is best used with non-
+     * blocking mode sockets.
+     */
     session = wolfSSL_get_session(ssl);
     if (session == NULL) {
         printf("Session not available yet... trying peek\n");
@@ -238,6 +253,7 @@ int main(int argc, char** argv)
             printf("Session ticket found\n");
         }
     }
+#endif
 
     /* Get a message for the server from stdin */
     printf("Message for server: ");