Move StripLocalAddresses to a common util

Trac: 19026

common/util/util.go

@@ -3,7 +3,9 @@ package util
 import (
 	"encoding/json"
 	"log"
+	"net"
 
+	"github.com/pion/sdp/v2"
 	"github.com/pion/webrtc/v2"
 )
 
@@ -56,3 +58,46 @@ func DeserializeSessionDescription(msg string) *webrtc.SessionDescription {
 		SDP:  parsed["sdp"].(string),
 	}
 }
+
+// Stolen from https://github.com/golang/go/pull/30278
+func IsLocal(ip net.IP) bool {
+	if ip4 := ip.To4(); ip4 != nil {
+		// Local IPv4 addresses are defined in https://tools.ietf.org/html/rfc1918
+		return ip4[0] == 10 ||
+			(ip4[0] == 172 && ip4[1]&0xf0 == 16) ||
+			(ip4[0] == 192 && ip4[1] == 168)
+	}
+	// Local IPv6 addresses are defined in https://tools.ietf.org/html/rfc4193
+	return len(ip) == net.IPv6len && ip[0]&0xfe == 0xfc
+}
+
+// Removes local LAN address ICE candidates
+func StripLocalAddresses(str string) string {
+	var desc sdp.SessionDescription
+	err := desc.Unmarshal([]byte(str))
+	if err != nil {
+		return str
+	}
+	for _, m := range desc.MediaDescriptions {
+		attrs := make([]sdp.Attribute, 0)
+		for _, a := range m.Attributes {
+			if a.IsICECandidate() {
+				ice, err := a.ToICECandidate()
+				if err == nil && ice.Typ == "host" {
+					ip := net.ParseIP(ice.Address)
+					if ip != nil && (IsLocal(ip) || ip.IsUnspecified() || ip.IsLoopback()) {
+						/* no append in this case */
+						continue
+					}
+				}
+			}
+			attrs = append(attrs, a)
+		}
+		m.Attributes = attrs
+	}
+	bts, err := desc.Marshal()
+	if err != nil {
+		return str
+	}
+	return string(bts)
+}