ice: add candidate sdp mdns support

[sreimers]

Some browsers anonymize local webrtc sdp candidate ip addresses with mDNS [UUID].local (like "1bbabc05-80d2-4386-8e39-9666b53900d0.local"), this PR uses getaddrinfo to resolve these if needed.

TODO:

• a callback notification is needed (rcand is ready)
• Tested with Safari iOS (16.6), Firefox (116.0.3) and Chromium (116.0.5845.110)

refs baresip/baresip#2137

https://datatracker.ietf.org/doc/html/draft-ietf-mmusic-mdns-ice-candidates-03

Manual Testing:

• Start baresip-webrtc -v
• Open URL in Browser (private browser mode) Check recvonly (no microphone/camera permission) and connect
• You should see mDNS remote candidates:

{      audio. } mDNS remote cand: 4e712009-4a6c-40df-87a5-55bda80e6257.local
{      audio. } conncheck_start: waiting mDNS for remote candidate...
{      video. } mDNS remote cand: 4e712009-4a6c-40df-87a5-55bda80e6257.local
{      video. } conncheck_start: waiting mDNS for remote candidate...

[paresy]

Wow, thanks for the PR! I was eager and patched it on-top of version 3.4.0. It seems to work very good, with the WebRTC demo without any ICE servers set. When i define ICE-Servers on WebRTC-Demo (Backend) and in the JS part of the demo and if i use Firefox (which sends all candidates; Chrome/Safari seem to skip sending external candidates on a loopback connection) then the demo crashes.

See the attached log:

Local network addresses:
        en0:  192.168.1.89
        en0:  fd4b:a493:d8a7:4a5e:1823:55e6:2bdc:2ae7
medianat: ice
dtls_srtp: use prime256v1 for elliptic curve cryptography
mediaenc: dtls_srtp
DTLS-SRTP ready with profiles SRTP_AES128_CM_SHA1_80:SRTP_AES128_CM_SHA1_32:SRTP_AEAD_AES_128_GCM:SRTP_AEAD_AES_256_GCM
vidcodec: H264
vidcodec: H264
avcodec: using H.264 encoder 'libopenh264' -- OpenH264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
avcodec: using H.264 decoder 'h264' -- H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
ausrc: avformat
vidsrc: avformat
demo: using ICE server: turn:a.relay.metered.ca:80
demo: listening on:
    http://127.0.0.1:9000/
demo: request: met=GET, path=/, prm=
demo: loaded file '/Users/paresy/baresip/webrtc/src/../www/index.html', 1058 bytes (text/html)
demo: request: met=GET, path=/js/main.js, prm=
demo: loaded file '/Users/paresy/baresip/webrtc/src/../www/js/main.js', 5516 bytes (text/javascript)
demo: request: met=POST, path=/connect, prm=
demo: create session
peerconnection: new: sdp=Offerer
peerconnection: using mnat 'ice'
ice: new session with TURN-server at a.relay.metered.ca (username=4c3e49b5d658489d3b14ec0e)
peerconnection: using menc 'dtls_srtp'
peerconnection: add video (codecs=2)
ice: policy = all
stream: video: starting mediaenc 'dtls_srtp' (wait_secure=1)
ice: resolved TURN-server to address 216.39.253.22:80
video: added interface: en0:192.168.1.89 (local pref 65534)
video: added interface: en0:fd4b:a493:d8a7:4a5e:1823:55e6:2bdc:2ae7 (local pref 65535)
ice: relay gathered for comp 1 (0 OK)
ice: all components gathered.
video: comp1 setting local: 216.39.253.22:45636
ice: video: Default local candidates: 216.39.253.22:45636 / ?
peerconnection: medianat gathered (stable)
demo: session gathered -- send sdp 'offer'
peerconnection: create offer
- - offer - -
- - - - - - -
descr: encode: type='offer'
demo: request: met=PUT, path=/sdp, prm=
demo: handle PUT sdp: content is 'application/json'
descr: decode: type='answer'
peerconnection: set remote description. type=answer
- - answer - -
- - - - - - -
stream: update 'video'
stream: receive: setting SSRC: 7e688c3c
video: RTP/RTCP multiplexing enabled
peerconnection: start ice
demo: request: met=PATCH, path=/candidate, prm=
demo: request: met=PATCH, path=/candidate, prm=
demo: request: met=PATCH, path=/candidate, prm=
demo: request: met=PATCH, path=/candidate, prm=
{      video.1} added PeerReflexive remote candidate with priority 1853751551 (192.168.1.89:63253)
ice: form: 'video' no remote candidates
ice: form: 'video' no remote candidates
ice: form: 'video' no remote candidates
ice: form: 'video' no remote candidates
stunsrv: {video.1} local candidate not found (checklist=0) (src=192.168.1.89:63253)
demo: request: met=PATCH, path=/candidate, prm=
{      video. } starting connectivity checks with 4 candidate pairs
{      video.1}  host <---> prflx  FSM:      Frozen ===> InProgress
{      video.1} Tx en0:host:192.168.1.89:25328 ---> prflx:192.168.1.89:63253 (InProgress)  
{      video.1} Rx en0:host:192.168.1.89:25328 <--- prflx:192.168.1.89:63253 '0 OK'
{      video.1}  host <---> prflx  FSM:  InProgress ===> Succeeded 
{      video.1}  host <---> srflx  FSM:      Frozen ===> InProgress
{      video.1} Tx en0:host:192.168.1.89:25328 ---> srflx:31.16.224.154:63253 (InProgress)  
demo: request: met=PATCH, path=/candidate, prm=
{      video. } starting connectivity checks with 4 candidate pairs
{      video.1} srflx <---> prflx  FSM:      Frozen ===> InProgress
{      video.1} Tx en0:srflx:31.16.224.154:25328 ---> prflx:192.168.1.89:63253 (InProgress)  
{      video.1} Rx en0:srflx:31.16.224.154:25328 <--- prflx:192.168.1.89:63253 '0 OK'
{      video.1} New local candidate for mapped 192.168.1.89:25328
{      video.1} srflx <---> prflx  FSM:  InProgress ===> Succeeded 
{      video.1} relay <---> prflx  FSM:      Frozen ===> InProgress
{      video.1} Tx relay:216.39.253.22:45636 ---> prflx:192.168.1.89:63253 (InProgress)  
{      video. } starting connectivity checks with 3 candidate pairs
{      video.1} relay <---> srflx  FSM:      Frozen ===> InProgress
{      video.1} Tx relay:216.39.253.22:45636 ---> srflx:31.16.224.154:63253 (InProgress)  
{1} TURN Client error: 403 Forbidden IP
ice: gathering srflx for comp 1 ..
{      video. } starting connectivity checks with 3 candidate pairs
{      video. } starting connectivity checks with 3 candidate pairs
{      video.1} Rx relay:216.39.253.22:45636 <--- prflx:192.168.1.89:63253 '0 OK'
{      video.1} New local candidate for mapped 192.168.1.89:25328
{      video.1} relay <---> prflx  FSM:  InProgress ===> Succeeded 
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
{      video. } starting connectivity checks with 2 candidate pairs
mem: mem_deref: magic check failed 0x00000200 (0x1386049a8)

Process finished with exit code 138 (interrupted by signal 10: SIGBUS)  

I tracked down the issue to this line:
mem_deref(rcand->domain); in rcand_dealloc

Maybe a race condition?

[sreimers]

Thanks for testing, yes the mem_deref(rcand->domain); is useless/fatal since pl_strcpy does not allocate, should be fixed now.