fix for windows/macos

net/connUDP.go

@@ -361,6 +361,12 @@ func (c *UDPConn) writeToAddr(iface *net.Interface, src *net.IP, multicastHopLim
 		return err
 	}
 	cm := toControlMessage(p, iface, src)
+	if !supportsSetPacketControlMessage(c.connection) {
+		// if remote address is set, we can use it as destination address
+		// because connection is already connected
+		// only linux supports overwriting destination address
+		cm = nil
+	}
 	_, err = p.WriteTo(buffer, cm, raddr)
 	return err
 }

net/connUDP_internal_test.go

@@ -376,13 +376,18 @@ func TestPacketConnIPv4ReadFrom(t *testing.T) {
 		errC := readUDP4Conn.Close()
 		require.NoError(t, errC)
 	}()
+
+	require.Nil(t, readUDP4Conn.RemoteAddr())
+
 	writeUDP4Conn, err := net.DialUDP("udp4", nil, readUDP4Conn.LocalAddr().(*net.UDPAddr))
 	require.NoError(t, err)
 	defer func() {
 		errC := writeUDP4Conn.Close()
 		require.NoError(t, errC)
 	}()
 
+	require.NotNil(t, writeUDP4Conn.RemoteAddr())
+
 	readUDP6Conn, err := net.ListenUDP("udp6", &net.UDPAddr{Port: 1235})
 	require.NoError(t, err)
 	defer func() {

net/supportsSetPacketControlMessage.go

@@ -0,0 +1,9 @@
+//go:build !linux
+
+package net
+
+import "net"
+
+func supportsSetPacketDestination(c *net.UDPConn) bool {
+	return c.RemoteAddr() == nil
+}

net/supportsSetPacketControlMessage_linux.go

@@ -0,0 +1,7 @@
+package net
+
+import "net"
+
+func supportsSetPacketControlMessage(*net.UDPConn) bool {
+	return true
+}