Remove IPv6 ZoneID from ICE candidates (#704)

Link-local IPv6 addresses may have ZoneID attached at the end. It has
local meaning only and should not be send to other parties. This change
removes ZoneID from generated candidate string, and ignores ZoneID
when received candidate is parsed.

candidate_base.go

@@ -447,6 +447,13 @@ func (c *candidateBase) copy() (Candidate, error) {
 	return UnmarshalCandidate(c.Marshal())
 }
 
+func removeZoneIDFromAddress(addr string) string {
+	if i := strings.Index(addr, "%"); i != -1 {
+		return addr[:i]
+	}
+	return addr
+}
+
 // Marshal returns the string representation of the ICECandidate
 func (c *candidateBase) Marshal() string {
 	val := c.Foundation()
@@ -459,7 +466,7 @@ func (c *candidateBase) Marshal() string {
 		c.Component(),
 		c.NetworkType().NetworkShort(),
 		c.Priority(),
-		c.Address(),
+		removeZoneIDFromAddress(c.Address()),
 		c.Port(),
 		c.Type())
 
@@ -509,7 +516,7 @@ func UnmarshalCandidate(raw string) (Candidate, error) {
 	priority := uint32(priorityRaw)
 
 	// Address
-	address := split[4]
+	address := removeZoneIDFromAddress(split[4])
 
 	// Port
 	rawPort, err := strconv.ParseUint(split[5], 10, 16)

candidate_test.go

@@ -391,7 +391,7 @@ func TestCandidateMarshal(t *testing.T) {
 
 		assert.NoError(t, err)
 
-		assert.True(t, test.candidate.Equal(actualCandidate))
+		assert.Truef(t, test.candidate.Equal(actualCandidate), "%s != %s", test.candidate.String(), actualCandidate.String())
 		assert.Equal(t, test.marshaled, actualCandidate.Marshal())
 	}
 }
@@ -435,3 +435,40 @@ func TestCandidateWriteTo(t *testing.T) {
 	_, err = c1.writeTo([]byte("test"), c2)
 	assert.Error(t, err, "writing to closed conn")
 }
+
+func TestMarshalUnmarshalCandidateWithZoneID(t *testing.T) {
+	candidateWithZoneID := &CandidateHost{
+		candidateBase{
+			networkType:        NetworkTypeUDP6,
+			candidateType:      CandidateTypeHost,
+			address:            "fcd9:e3b8:12ce:9fc5:74a5:c6bb:d8b:e08a%Local Connection",
+			port:               53987,
+			priorityOverride:   500,
+			foundationOverride: "750",
+		},
+		"",
+	}
+	candidateStr := "750 0 udp 500 fcd9:e3b8:12ce:9fc5:74a5:c6bb:d8b:e08a 53987 typ host"
+	require.Equal(t, candidateStr, candidateWithZoneID.Marshal())
+
+	candidate := &CandidateHost{
+		candidateBase{
+			networkType:        NetworkTypeUDP6,
+			candidateType:      CandidateTypeHost,
+			address:            "fcd9:e3b8:12ce:9fc5:74a5:c6bb:d8b:e08a",
+			port:               53987,
+			priorityOverride:   500,
+			foundationOverride: "750",
+		},
+		"",
+	}
+	candidateWithZoneIDStr := "750 0 udp 500 fcd9:e3b8:12ce:9fc5:74a5:c6bb:d8b:e08a%eth0 53987 typ host"
+	candidate2, err := UnmarshalCandidate(candidateWithZoneIDStr)
+	require.NoError(t, err)
+	require.Truef(t, candidate.Equal(candidate2), "%s != %s", candidate.String(), candidate2.String())
+
+	candidateWithZoneIDStr2 := "750 0 udp 500 fcd9:e3b8:12ce:9fc5:74a5:c6bb:d8b:e08a%eth0%eth1 53987 typ host"
+	candidate2, err = UnmarshalCandidate(candidateWithZoneIDStr2)
+	require.NoError(t, err)
+	require.Truef(t, candidate.Equal(candidate2), "%s != %s", candidate.String(), candidate2.String())
+}