Add relayServerIP field to signal for foreign-relay fallback dial

shared/relay/client/dialer/ws/ws.go

@@ -26,13 +26,14 @@ func (d Dialer) Protocol() string {
 	return "WS"
 }
 
-func (d Dialer) Dial(ctx context.Context, address string) (net.Conn, error) {
+func (d Dialer) Dial(ctx context.Context, address, serverName string) (net.Conn, error) {
 	wsURL, err := prepareURL(address)
 	if err != nil {
 		return nil, err
 	}
 
-	opts := createDialOptions()
+	var underlying net.Conn
+	opts := createDialOptions(serverName, &underlying)
 
 	parsedURL, err := url.Parse(wsURL)
 	if err != nil {
@@ -52,7 +53,7 @@ func (d Dialer) Dial(ctx context.Context, address string) (net.Conn, error) {
 		_ = resp.Body.Close()
 	}
 
-	conn := NewConn(wsConn, address)
+	conn := NewConn(wsConn, address, underlying)
 	return conn, nil
 }
 
@@ -64,7 +65,10 @@ func prepareURL(address string) (string, error) {
 	return strings.Replace(address, "rel", "ws", 1), nil
 }
 
-func httpClientNbDialer() *http.Client {
+// httpClientNbDialer builds the http client used by the websocket library.
+// underlyingOut, when non-nil, is populated with the raw conn from the
+// transport's DialContext so the caller can read its RemoteAddr.
+func httpClientNbDialer(serverName string, underlyingOut *net.Conn) *http.Client {
 	customDialer := nbnet.NewDialer()
 
 	certPool, err := x509.SystemCertPool()
@@ -75,10 +79,15 @@ func httpClientNbDialer() *http.Client {
 
 	customTransport := &http.Transport{
 		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
-			return customDialer.DialContext(ctx, network, addr)
+			c, err := customDialer.DialContext(ctx, network, addr)
+			if err == nil && underlyingOut != nil {
+				*underlyingOut = c
+			}
+			return c, err
 		},
 		TLSClientConfig: &tls.Config{
-			RootCAs: certPool,
+			RootCAs:    certPool,
+			ServerName: serverName,
 		},
 	}