Feature: add support for multicast (#245)

* add support for multicast (#243)

* adjust setup

---------

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

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
+}