Implemented and fixed many issues

Common/Client/go/wshub/sources.go

@@ -447,6 +447,52 @@ func (u *UDPClient) runSession() error {
 	}
 }
 
+// interfaceForIP returns the interface that owns the given local address, or
+// nil if no interface matches (in which case callers fall back to letting the
+// kernel choose).
+func interfaceForIP(ip net.IP) *net.Interface {
+	if ip == nil || ip.IsUnspecified() {
+		return nil
+	}
+	ifaces, err := net.Interfaces()
+	if err != nil {
+		return nil
+	}
+	for i := range ifaces {
+		addrs, err := ifaces[i].Addrs()
+		if err != nil {
+			continue
+		}
+		for _, a := range addrs {
+			var aIP net.IP
+			switch v := a.(type) {
+			case *net.IPNet:
+				aIP = v.IP
+			case *net.IPAddr:
+				aIP = v.IP
+			}
+			if aIP != nil && aIP.Equal(ip) {
+				return &ifaces[i]
+			}
+		}
+	}
+	return nil
+}
+
+// interfaceForConn returns the interface a connection's local endpoint sits on.
+func interfaceForConn(c net.Conn) *net.Interface {
+	if c == nil {
+		return nil
+	}
+	switch a := c.LocalAddr().(type) {
+	case *net.TCPAddr:
+		return interfaceForIP(a.IP)
+	case *net.UDPAddr:
+		return interfaceForIP(a.IP)
+	}
+	return nil
+}
+
 // runMulticastSession handles the multicast mode session.
 func (u *UDPClient) runMulticastSession() error {
 	tcpAddr, err := net.ResolveTCPAddr("tcp4", u.serverAddr)
@@ -500,7 +546,15 @@ func (u *UDPClient) runMulticastSession() error {
 		return &net.AddrError{Err: "invalid multicast group IP", Addr: u.multicastGroup}
 	}
 	mcastAddr := &net.UDPAddr{IP: mcastIP, Port: mcastPort}
-	mcastConn, err := net.ListenMulticastUDP("udp4", nil, mcastAddr)
+	// Join on the interface that reaches the control connection. The UDPStreamer
+	// pins its multicast sends to its configured Interface (IP_MULTICAST_IF), so
+	// a join with a nil interface — which leaves imr_interface at INADDR_ANY and
+	// lets the kernel pick the default-route interface — silently receives
+	// nothing whenever that is not the sending interface. The local address of
+	// the control connection is the interface the server is reachable on, which
+	// is the sending interface in every single-homed and same-host deployment.
+	ifi := interfaceForConn(tcpConn)
+	mcastConn, err := net.ListenMulticastUDP("udp4", ifi, mcastAddr)
 	if err != nil {
 		return err
 	}
@@ -508,7 +562,12 @@ func (u *UDPClient) runMulticastSession() error {
 	if err := mcastConn.SetReadBuffer(udpRcvBufSize); err != nil {
 		log.Printf("[%s] multicast SetReadBuffer: %v", u.sourceID, err)
 	}
-	log.Printf("[%s] joined multicast %s:%s", u.sourceID, u.multicastGroup, strconv.Itoa(mcastPort))
+	ifName := "default"
+	if ifi != nil {
+		ifName = ifi.Name
+	}
+	log.Printf("[%s] joined multicast %s:%s on interface %s",
+		u.sourceID, u.multicastGroup, strconv.Itoa(mcastPort), ifName)
 
 	tcpDone := make(chan error, 1)
 	go func() {