Extensions: Network filter to forward SNI from the downstream TLS connection to the upstream TLS connection

api/envoy/api/v2/auth/cert.proto

@@ -278,6 +278,11 @@ message UpstreamTlsContext {
   //
   //   TLS renegotiation is considered insecure and shouldn't be used unless absolutely necessary.
   bool allow_renegotiation = 3;
+
+  // If true, the SNI from the downstream connection is forwarded to the upstream connection.
+  //
+  // TODO: handle oneof with the sni
+  bool forward_original_sni = 4;
 }
 
 message DownstreamTlsContext {