Preserve ICE candidate Extensions

Ensure that ICE candidates are retained when parsed and stringified,
and converted to ICE.candidate.

icecandidate.go

@@ -24,6 +24,7 @@ type ICECandidate struct {
 	TCPType        string           `json:"tcpType"`
 	SDPMid         string           `json:"sdpMid"`
 	SDPMLineIndex  uint16           `json:"sdpMLineIndex"`
+	extensions     []ice.CandidateExtension
 }
 
 // Conversion for package ice.
@@ -67,6 +68,7 @@ func newICECandidateFromICE(candidate ice.Candidate, sdpMid string, sdpMLineInde
 		TCPType:       candidate.TCPType().String(),
 		SDPMid:        sdpMid,
 		SDPMLineIndex: sdpMLineIndex,
+		extensions:    candidate.Extensions(),
 	}
 
 	if candidate.RelatedAddress() != nil {
@@ -77,7 +79,7 @@ func newICECandidateFromICE(candidate ice.Candidate, sdpMid string, sdpMLineInde
 	return newCandidate, nil
 }
 
-func (c ICECandidate) toICE() (ice.Candidate, error) {
+func (c ICECandidate) toICE() (cand ice.Candidate, err error) {
 	candidateID := c.statsID
 	switch c.Typ {
 	case ICECandidateTypeHost:
@@ -92,7 +94,7 @@ func (c ICECandidate) toICE() (ice.Candidate, error) {
 			Priority:    c.Priority,
 		}
 
-		return ice.NewCandidateHost(&config)
+		cand, err = ice.NewCandidateHost(&config)
 	case ICECandidateTypeSrflx:
 		config := ice.CandidateServerReflexiveConfig{
 			CandidateID: candidateID,
@@ -106,7 +108,7 @@ func (c ICECandidate) toICE() (ice.Candidate, error) {
 			RelPort:     int(c.RelatedPort),
 		}
 
-		return ice.NewCandidateServerReflexive(&config)
+		cand, err = ice.NewCandidateServerReflexive(&config)
 	case ICECandidateTypePrflx:
 		config := ice.CandidatePeerReflexiveConfig{
 			CandidateID: candidateID,
@@ -120,7 +122,7 @@ func (c ICECandidate) toICE() (ice.Candidate, error) {
 			RelPort:     int(c.RelatedPort),
 		}
 
-		return ice.NewCandidatePeerReflexive(&config)
+		cand, err = ice.NewCandidatePeerReflexive(&config)
 	case ICECandidateTypeRelay:
 		config := ice.CandidateRelayConfig{
 			CandidateID: candidateID,
@@ -134,10 +136,21 @@ func (c ICECandidate) toICE() (ice.Candidate, error) {
 			RelPort:     int(c.RelatedPort),
 		}
 
-		return ice.NewCandidateRelay(&config)
+		cand, err = ice.NewCandidateRelay(&config)
 	default:
 		return nil, fmt.Errorf("%w: %s", errICECandidateTypeUnknown, c.Typ)
 	}
+
+	if cand != nil && err == nil {
+		for i := range c.extensions {
+			err = cand.AddExtension(c.extensions[i])
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	return cand, err
 }
 
 func convertTypeFromICE(t ice.CandidateType) (ICECandidateType, error) {

icecandidate_test.go

@@ -248,3 +248,20 @@ func TestICECandidateSDPMid_ToJSON(t *testing.T) {
 	assert.Equal(t, candidate.SDPMid, "0")
 	assert.Equal(t, candidate.SDPMLineIndex, uint16(1))
 }
+
+func TestICECandidateExtensions_ToJSON(t *testing.T) {
+	cand := "2637185494 1 udp 2121932543 192.168.1.4 50723 typ host generation 1 ufrag Jzd0 network-id 1"
+	candidate, err := ice.UnmarshalCandidate(cand)
+	assert.NoError(t, err)
+
+	sdpMid := "1"
+	sdpMLineIndex := uint16(2)
+
+	iceCandidate, err := newICECandidateFromICE(candidate, sdpMid, sdpMLineIndex)
+	assert.NoError(t, err)
+
+	candidateInit := iceCandidate.ToJSON()
+
+	assert.Equal(t, sdpMLineIndex, *candidateInit.SDPMLineIndex)
+	assert.Equal(t, "candidate:"+cand, candidateInit.Candidate)
+}