Intranet connection fails sporadically

[lostmsu]

Same machine and remote connections work fine, but intranet connection (192.168.x.x behind NAT) fails most of the time.

From the log I suspect SIPSorcery completely ignores the ice candidate with .local mDNS name that Chrome sends, so it seems the same as #743 except I don't get any errors regarding this candidate.

Are mDNS candidates like this supported/implemented at all (e.g. should the issue 743 be considered a feature request)?

Can something be done to let the browser drive the connection somehow (if that makes sense)? As seen from the log my app sends out an ice candidate with a local IP, and Chrome client should be able to connect to it.

Here's the example log:

sipsorcery: Warning: No DTLS certificate is provided in the configuration
sipsorcery: Debug: CreateRtpSocket attempting to create and bind RTP socket(s) on [::]:0.
sipsorcery: Debug: CreateBoundSocket attempting to create and bind socket(s) on [::]:0 using protocol Udp.
sipsorcery: Debug: CreateBoundSocket successfully bound on [::]:49509, dual mode True.
sipsorcery: Debug: Successfully bound RTP socket [::]:49509 (dual mode True).
sipsorcery: Debug: RTPChannel for [::]:49509 started.
SIPSorcery.Net.SctpDataReceiver: Debug: SCTP windows size for data receiver set at 218.
sipsorcery: Debug: SCTP creating DTLS based association, is DTLS client False, ID 5000:5000:49509.
sipsorcery: Debug: Adding ICE server for stun:stun.l.google.com:19302.
sipsorcery: Debug: Data channel create request for label control.
sipsorcery: Debug: Data channel create request for label persistence.
sipsorcery: Debug: RTP ICE Channel discovered 1 local candidates.
sipsorcery: Debug: Adding ICE server for stun:stun.l.google.com:19302.
sipsorcery: Debug: Attempting to resolve STUN server URI stun:stun.l.google.com:19302.
Borg.Drone.Drone: Debug: Status: PreparingUplink
Borg.Drone.Uplink.Trusted.Signaling.OneDriveSignaling: Debug: local ice candidate {"candidate":"candidate:132864737 1 udp 2113937663 192.168.0.18 49509 typ host generation 0","sdpMid":"0","sdpMLineIndex":0,"usernameFragment":"HXTG"}
sipsorcery: Debug: ICE server stun:stun.l.google.com:19302 successfully resolved to 142.250.107.127:19302.
sipsorcery: Debug: Sending STUN binding request to ICE server stun:stun.l.google.com:19302  with address 142.250.107.127:19302.
sipsorcery: Debug: STUN binding success response received for ICE server check to stun:stun.l.google.com:19302.
sipsorcery: Debug: Adding server reflex ICE candidate for ICE server stun:stun.l.google.com:19302 and 50.35.77.75:49509.
Borg.Drone.Uplink.Trusted.Signaling.OneDriveSignaling: Debug: local ice candidate {"candidate":"candidate:1674909274 1 udp 1677730047 50.35.77.75 49509 typ srflx raddr 0.0.0.0 rport 0 generation 0","sdpMid":"0","sdpMLineIndex":0,"usernameFragment":"HXTG"}
sipsorcery: Debug: ICE RTP channel stopping ICE server checks in gathering state complete and connection state new.
Borg.Drone.Uplink.Trusted.Signaling.OneDriveSignaling: Debug: new client file f88d0ce3-eca4-4445-984b-a970602c7e7c.sdp.client~RF5286cf80.TMP
Borg.Drone.Uplink.Trusted.Signaling.OneDriveSignaling: Debug: new client file f88d0ce3-eca4-4445-984b-a970602c7e7c.sdp.client
sipsorcery: Debug: RTP ICE Channel remote credentials set.
sipsorcery: Debug: SDP:[v=0
o=- 9213657954109484297 2 IN IP4 127.0.0.1
s=-
t=0 0
a=group:BUNDLE 0 1 2
a=msid-semantic: WMS
m=audio 9 UDP/TLS/RTP/SAVP 0 101
c=IN IP4 0.0.0.0
a=ice-ufrag:0gXJ
a=ice-pwd:ku+57rDP02jVQP2WTtX30P1B
a=fingerprint:sha-256 58:C8:DD:14:D5:15:ED:35:0B:4F:B6:B4:F2:D8:98:DD:B7:7E:93:13:C2:41:64:52:E7:CE:3D:60:C1:1B:08:9C
a=setup:active
a=mid:0
a=rtpmap:0 PCMU/8000
a=rtpmap:101 telephone-event/8000
a=rtcp:9 IN IP4 0.0.0.0
a=ice-options:trickle
a=rtcp-mux
a=recvonly
m=video 9 UDP/TLS/RTP/SAVP 100
c=IN IP4 0.0.0.0
a=ice-ufrag:0gXJ
a=ice-pwd:ku+57rDP02jVQP2WTtX30P1B
a=fingerprint:sha-256 58:C8:DD:14:D5:15:ED:35:0B:4F:B6:B4:F2:D8:98:DD:B7:7E:93:13:C2:41:64:52:E7:CE:3D:60:C1:1B:08:9C
a=setup:active
a=mid:1
a=rtpmap:100 H264/90000
a=fmtp:100 level-asymmetry-allowed=1;packetization-mode=0;profile-level-id=42e01f
a=rtcp:9 IN IP4 0.0.0.0
a=ice-options:trickle
a=rtcp-mux
a=recvonly
m=application 9 UDP/DTLS/SCTP webrtc-datachannel
c=IN IP4 0.0.0.0
a=ice-ufrag:0gXJ
a=ice-pwd:ku+57rDP02jVQP2WTtX30P1B
a=fingerprint:sha-256 58:C8:DD:14:D5:15:ED:35:0B:4F:B6:B4:F2:D8:98:DD:B7:7E:93:13:C2:41:64:52:E7:CE:3D:60:C1:1B:08:9C
a=setup:active
a=mid:2
a=ice-options:trickle
a=sctp-port:5000
a=max-message-size:262144
]
sipsorcery: Debug: LogRemoteSDPSsrcAttributes: Audio:[ ] 
 Video: [  []  ]
Borg.Drone.Uplink.Trusted.Signaling.OneDriveSignaling: Debug: local ice candidate {"candidate":"candidate:1674909274 1 udp 1677730047 50.35.77.75 49509 typ srflx raddr 0.0.0.0 rport 0 generation 0","sdpMid":"0","sdpMLineIndex":0,"usernameFragment":"HXTG"}
Borg.Drone.Uplink.Connection: Information: set remote description: {"type":"answer","sdp":"v=0\r\no=- 9213657954109484297 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=group:BUNDLE 0 1 2\r\na=msid-semantic: WMS\r\nm=audio 9 UDP/TLS/RTP/SAVP 0 101\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=ice-ufrag:0gXJ\r\na=ice-pwd:ku+57rDP02jVQP2WTtX30P1B\r\na=ice-options:trickle\r\na=fingerprint:sha-256 58:C8:DD:14:D5:15:ED:35:0B:4F:B6:B4:F2:D8:98:DD:B7:7E:93:13:C2:41:64:52:E7:CE:3D:60:C1:1B:08:9C\r\na=setup:active\r\na=mid:0\r\na=recvonly\r\na=rtcp-mux\r\na=rtpmap:0 PCMU/8000\r\na=rtpmap:101 telephone-event/8000\r\nm=video 9 UDP/TLS/RTP/SAVP 100\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=ice-ufrag:0gXJ\r\na=ice-pwd:ku+57rDP02jVQP2WTtX30P1B\r\na=ice-options:trickle\r\na=fingerprint:sha-256 58:C8:DD:14:D5:15:ED:35:0B:4F:B6:B4:F2:D8:98:DD:B7:7E:93:13:C2:41:64:52:E7:CE:3D:60:C1:1B:08:9C\r\na=setup:active\r\na=mid:1\r\na=recvonly\r\na=rtcp-mux\r\na=rtpmap:100 H264/90000\r\na=fmtp:100 level-asymmetry-allowed=1;packetization-mode=0;profile-level-id=42e01f\r\nm=application 9 UDP/DTLS/SCTP webrtc-datachannel\r\nc=IN IP4 0.0.0.0\r\na=ice-ufrag:0gXJ\r\na=ice-pwd:ku+57rDP02jVQP2WTtX30P1B\r\na=ice-options:trickle\r\na=fingerprint:sha-256 58:C8:DD:14:D5:15:ED:35:0B:4F:B6:B4:F2:D8:98:DD:B7:7E:93:13:C2:41:64:52:E7:CE:3D:60:C1:1B:08:9C\r\na=setup:active\r\na=mid:2\r\na=sctp-port:5000\r\na=max-message-size:262144\r\n"}
Borg.Drone.Uplink.Connection: Information: added remote ice candidate: {"candidate":"candidate:3431339218 1 udp 2113937151 b463c30d-aae3-4018-97a7-e0e78740710d.local 52101 typ host generation 0 ufrag 0gXJ network-cost 999","sdpMid":"0","sdpMLineIndex":0,"usernameFragment":"0gXJ"}
sipsorcery: Debug: RTP ICE Channel received remote candidate: 1549056351 1 udp 1677729535 50.35.77.75 52101 typ srflx raddr 0.0.0.0 rport 0 generation 0
Borg.Drone.Uplink.Connection: Information: added remote ice candidate: {"candidate":"candidate:1549056351 1 udp 1677729535 50.35.77.75 52101 typ srflx raddr 0.0.0.0 rport 0 generation 0 ufrag 0gXJ network-cost 999","sdpMid":"0","sdpMLineIndex":0,"usernameFragment":"0gXJ"}
sipsorcery: Debug: Adding new candidate pair to checklist for: udp:[::]:49509 (host)->udp:50.35.77.75:52101 (srflx)
sipsorcery: Debug: ICE RTP channel sending connectivity check for udp:[::]:49509 (host)->udp:50.35.77.75:52101 (srflx) from [::]:49509 to 50.35.77.75:52101 (use candidate False).
sipsorcery: Debug: ICE RTP channel sending connectivity check for udp:[::]:49509 (host)->udp:50.35.77.75:52101 (srflx) from [::]:49509 to 50.35.77.75:52101 (use candidate False).
sipsorcery: Debug: ICE RTP channel sending connectivity check for udp:[::]:49509 (host)->udp:50.35.77.75:52101 (srflx) from [::]:49509 to 50.35.77.75:52101 (use candidate False).
sipsorcery: Debug: ICE RTP channel sending connectivity check for udp:[::]:49509 (host)->udp:50.35.77.75:52101 (srflx) from [::]:49509 to 50.35.77.75:52101 (use candidate False).
... (many of the above)
sipsorcery: Debug: ICE RTP channel sending connectivity check for udp:[::]:49509 (host)->udp:50.35.77.75:52101 (srflx) from [::]:49509 to 50.35.77.75:52101 (use candidate False).
sipsorcery: Debug: ICE RTP channel checks for checklist entry have timed out, state being set to failed: udp:[::]:49509 (host)->udp:50.35.77.75:52101 (srflx).
Borg.Drone.VideoStreaming: Debug: connection state changed: failed
sipsorcery: Debug: ICE RTP channel stopping connectivity checks in connection state failed.
sipsorcery: Debug: Peer connection closed with reason normal.
sipsorcery: Debug: RtpIceChannel for [::]:49509 closed.
sipsorcery: Debug: RTPChannel closing, RTP receiver on port 49509. Reason: normal.
Borg.Drone.VideoStreaming: Debug: connection state changed: closed

[lostmsu]

The answer is: sipsorcery does not include mDNS resolver, but it has an extension point for one:

rtcPeerConnectionInstance.GetRtpChannel().MdnsResolve += mDNSResolve;

All modern versions of Windows will simply resolve mDNS .local addresses for you if you call Dns.GetHostAddresses(...). I believe Linux and MacOS will do that too.

So basically IMHO SIPSorcery should default to using the System.Net.Dns class unless user overrides MdnsResolve.