Fix for SNI callback

* Fix for SNI callback on server to make sure the SNI data is stored even without setting a hostname. This makes sure the SNI extension is set when there is a registered SNI recv callback.
* Fix for Apache HTTPD to include `WOLFSSL_ALWAYS_KEEP_SNI`

configure.ac

@@ -4279,6 +4279,7 @@ then
     AM_CFLAGS="$AM_CFLAGS -DOPENSSL_NO_SSL2 -DOPENSSL_NO_SSL3 -DOPENSSL_NO_COMP"
     AM_CFLAGS="$AM_CFLAGS -DHAVE_EX_DATA -DWOLFSSL_SIGNER_DER_CERT"
     AM_CFLAGS="$AM_CFLAGS -DWOLFSSL_CERT_EXT -DWOLFSSL_CERT_GEN"
+    AM_CFLAGS="$AM_CFLAGS -DWOLFSSL_ALWAYS_KEEP_SNI"
 
     # Requires OCSP make sure on
     if test "x$ENABLED_OCSP" = "xno"

examples/client/client.c

@@ -2692,7 +2692,7 @@ THREAD_RETURN WOLFSSL_THREAD client_test(void* args)
 
 #ifdef HAVE_SNI
     if (sniHostName) {
-        if (wolfSSL_CTX_UseSNI(ctx, 0, sniHostName,
+        if (wolfSSL_CTX_UseSNI(ctx, WOLFSSL_SNI_HOST_NAME, sniHostName,
                     (word16) XSTRLEN(sniHostName)) != WOLFSSL_SUCCESS) {
             wolfSSL_CTX_free(ctx); ctx = NULL;
             err_sys("UseSNI failed");

src/tls.c

@@ -2024,18 +2024,24 @@ static int TLSX_SNI_Parse(WOLFSSL* ssl, const byte* input, word16 length,
 
 #ifndef NO_WOLFSSL_SERVER
     if (!extension || !extension->data) {
-        #if defined(WOLFSSL_ALWAYS_KEEP_SNI) && !defined(NO_WOLFSSL_SERVER)
         /* This will keep SNI even though TLSX_UseSNI has not been called.
          * Enable it so that the received sni is available to functions
          * that use a custom callback when SNI is received.
          */
-
+    #ifdef WOLFSSL_ALWAYS_KEEP_SNI
         cacheOnly = 1;
+    #endif
+        if (ssl->ctx->sniRecvCb) {
+            cacheOnly = 1;
+        }
+
+        if (cacheOnly) {
             WOLFSSL_MSG("Forcing SSL object to store SNI parameter");
-        #else
+        }
+        else {
             /* Skipping, SNI not enabled at server side. */
             return 0;
-        #endif
+        }
     }
 
     if (OPAQUE16_LEN > length)