TEL-889: Nullity check for address in connection info

sdp/helpers.go

@@ -38,15 +38,21 @@ func GetAudioDest(s *sdp.SessionDescription, audio *sdp.MediaDescription) (netip
 		return netip.AddrPort{}, errors.New("no audio in sdp")
 	}
 
-	// pick media-level c=; if absent, fall back to session-level c=
-	ci := audio.ConnectionInformation
-	if ci == nil {
-		ci = s.ConnectionInformation
+	// A c= line without an address parses to a non-nil ConnectionInformation
+	// with a nil Address, so it has to be checked separately.
+	connAddr := func(ci *sdp.ConnectionInformation) string {
+		if ci == nil || ci.NetworkType != "IN" || ci.Address == nil {
+			return ""
+		}
+		return ci.Address.Address
+	}
+
+	// pick media-level c=, then session-level c=, then the o= address
+	addr := connAddr(audio.ConnectionInformation)
+	if addr == "" {
+		addr = connAddr(s.ConnectionInformation)
 	}
-	var addr string
-	if ci != nil && ci.NetworkType == "IN" {
-		addr = ci.Address.Address
-	} else if s.Origin.NetworkType == "IN" {
+	if addr == "" && s.Origin.NetworkType == "IN" {
 		addr = s.Origin.UnicastAddress
 	}
 	if addr == "" {

sdp/helpers_test.go

@@ -80,6 +80,87 @@ func TestGetAudioDest(t *testing.T) {
 			},
 			expected: netip.MustParseAddrPort("1.2.3.4:1234"),
 		},
+		{
+			name: "media level connection info without address",
+			session: &sdp.SessionDescription{
+				ConnectionInformation: &sdp.ConnectionInformation{
+					NetworkType: "IN",
+					AddressType: "IP4",
+					Address:     &sdp.Address{Address: "1.2.3.4"},
+				},
+			},
+			audio: &sdp.MediaDescription{
+				MediaName: sdp.MediaName{
+					Media: "audio",
+					Port:  sdp.RangedPort{Value: 1234},
+				},
+				ConnectionInformation: &sdp.ConnectionInformation{
+					NetworkType: "IN",
+					AddressType: "IP4",
+				},
+			},
+			expected: netip.MustParseAddrPort("1.2.3.4:1234"),
+		},
+		{
+			name: "connection info without address falls back to origin",
+			session: &sdp.SessionDescription{
+				Origin: sdp.Origin{
+					NetworkType:    "IN",
+					AddressType:    "IP4",
+					UnicastAddress: "5.6.7.8",
+				},
+				ConnectionInformation: &sdp.ConnectionInformation{
+					NetworkType: "IN",
+					AddressType: "IP4",
+				},
+			},
+			audio: &sdp.MediaDescription{
+				MediaName: sdp.MediaName{
+					Media: "audio",
+					Port:  sdp.RangedPort{Value: 1234},
+				},
+			},
+			expected: netip.MustParseAddrPort("5.6.7.8:1234"),
+		},
+		{
+			name: "non-IN connection info falls back to session level",
+			session: &sdp.SessionDescription{
+				ConnectionInformation: &sdp.ConnectionInformation{
+					NetworkType: "IN",
+					AddressType: "IP4",
+					Address:     &sdp.Address{Address: "1.2.3.4"},
+				},
+			},
+			audio: &sdp.MediaDescription{
+				MediaName: sdp.MediaName{
+					Media: "audio",
+					Port:  sdp.RangedPort{Value: 1234},
+				},
+				ConnectionInformation: &sdp.ConnectionInformation{
+					NetworkType: "FOO",
+					AddressType: "IP4",
+					Address:     &sdp.Address{Address: "9.9.9.9"},
+				},
+			},
+			expected: netip.MustParseAddrPort("1.2.3.4:1234"),
+		},
+		{
+			name: "no usable address anywhere",
+			session: &sdp.SessionDescription{
+				ConnectionInformation: &sdp.ConnectionInformation{
+					NetworkType: "IN",
+					AddressType: "IP4",
+				},
+			},
+			audio: &sdp.MediaDescription{
+				MediaName: sdp.MediaName{
+					Media: "audio",
+					Port:  sdp.RangedPort{Value: 1234},
+				},
+			},
+			expected: netip.AddrPort{},
+			error:    true,
+		},
 		{
 			name:     "nil session",
 			session:  nil,

sdp/offer_test.go

@@ -529,6 +529,55 @@ a=sendrecv
 `,
 			wantErr: true,
 		},
+		{
+			// The media-level c= has no address, so the session-level one is used.
+			name: "media level c= without address",
+			sdp: `v=0
+o=- 1234567890 1234567890 IN IP4 1.2.3.4
+s=LiveKit
+c=IN IP4 1.2.3.4
+t=0 0
+m=audio 1234 RTP/AVP 0 101
+c=IN IP4
+a=rtpmap:0 PCMU/8000
+a=rtpmap:101 telephone-event/8000
+a=ptime:20
+a=sendrecv
+`,
+			wantErr: false,
+		},
+		{
+			name: "session level c= without address falls back to o=",
+			sdp: `v=0
+o=- 1234567890 1234567890 IN IP4 1.2.3.4
+s=LiveKit
+c=IN IP4
+t=0 0
+m=audio 1234 RTP/AVP 0 101
+a=rtpmap:0 PCMU/8000
+a=rtpmap:101 telephone-event/8000
+a=ptime:20
+a=sendrecv
+`,
+			wantErr: false,
+		},
+		{
+			// Neither c= nor o= carries an address. pion defaults the o= address
+			// to 0.0.0.0, so this parses rather than failing.
+			name: "no address in c= or o=",
+			sdp: `v=0
+o=- 1234567890 1234567890 IN IP4
+s=LiveKit
+c=IN IP4
+t=0 0
+m=audio 1234 RTP/AVP 0 101
+a=rtpmap:0 PCMU/8000
+a=rtpmap:101 telephone-event/8000
+a=ptime:20
+a=sendrecv
+`,
+			wantErr: false,
+		},
 	}
 
 	for _, test := range tests {
@@ -543,6 +592,29 @@ a=sendrecv
 	}
 }
 
+// An unusable media-level c= must fall through to the session-level c=, not all
+// the way to o=.
+func TestParseOfferConnectionAddressFallback(t *testing.T) {
+	g := media.GlobalCodecs()
+
+	const sdpData = `v=0
+o=- 1234567890 1234567890 IN IP4 5.6.7.8
+s=LiveKit
+c=IN IP4 1.2.3.4
+t=0 0
+m=audio 1234 RTP/AVP 0 101
+c=IN IP4
+a=rtpmap:0 PCMU/8000
+a=rtpmap:101 telephone-event/8000
+a=ptime:20
+a=sendrecv
+`
+
+	offer, err := ParseOfferWith(g, []byte(sdpData))
+	require.NoError(t, err)
+	require.Equal(t, netip.MustParseAddrPort("1.2.3.4:1234"), offer.Addr)
+}
+
 func TestParseOfferSRTP(t *testing.T) {
 	g := media.GlobalCodecs()