Feature: add support for multicast (#245)

* add support for multicast (#243)

* adjust setup

---------

Co-authored-by: xjasonlyu <xjasonlyu@gmail.com>

engine/engine.go

@@ -193,6 +193,11 @@ func netstack(k *Key) (err error) {
 		return
 	}
 
+	var multicastGroups []net.IP
+	if multicastGroups, err = parseMulticastGroups(k.MulticastGroups); err != nil {
+		return err
+	}
+
 	var opts []option.Option
 	if k.TCPModerateReceiveBuffer {
 		opts = append(opts, option.WithTCPModerateReceiveBuffer(true))
@@ -217,6 +222,7 @@ func netstack(k *Key) (err error) {
 	if _defaultStack, err = core.CreateStack(&core.Config{
 		LinkEndpoint:     _defaultDevice,
 		TransportHandler: &mirror.Tunnel{},
+		MulticastGroups:  multicastGroups,
 		Options:          opts,
 	}); err != nil {
 		return

engine/key.go

@@ -13,6 +13,7 @@ type Key struct {
 	TCPModerateReceiveBuffer bool          `yaml:"tcp-moderate-receive-buffer"`
 	TCPSendBufferSize        string        `yaml:"tcp-send-buffer-size"`
 	TCPReceiveBufferSize     string        `yaml:"tcp-receive-buffer-size"`
+	MulticastGroups          string        `yaml:"multicast-groups"`
 	TUNPreUp                 string        `yaml:"tun-pre-up"`
 	TUNPostUp                string        `yaml:"tun-post-up"`
 	UDPTimeout               time.Duration `yaml:"udp-timeout"`

engine/parse.go

@@ -150,3 +150,21 @@ func parseShadowsocks(u *url.URL) (address, method, password, obfsMode, obfsHost
 
 	return
 }
+
+func parseMulticastGroups(s string) (multicastGroups []net.IP, _ error) {
+	ipStrings := strings.Split(s, ",")
+	for _, ipString := range ipStrings {
+		if strings.TrimSpace(ipString) == "" {
+			continue
+		}
+		ip := net.ParseIP(ipString)
+		if ip == nil {
+			return nil, fmt.Errorf("invalid IP format: %s", ipString)
+		}
+		if !ip.IsMulticast() {
+			return nil, fmt.Errorf("invalid multicast IP address: %s", ipString)
+		}
+		multicastGroups = append(multicastGroups, ip)
+	}
+	return
+}