[libnice] nice_agent_restart_stream: proper usage and local candidate gathering with gstreamer

[Olivier Crête]

Hi,

Yes, if you do a ICE restart, the local candidates stay the same. You
can re-fetch them using nice_agent_get_local_candidates(), but they
will not have changed. The goal of a ICE restart is really to reconnect
to a different endpoint but while keeping your local endpoint
"unchanged", which means that you can do it seamlessly without dropping
anything.

Olivier

On Mon, 2020-12-14 at 07:45 +0000, Zachary Hueras wrote:
> On my quest, I've (belatedly) RTFM. It states:
> 
>     Note that to modify the set of local candidates, a new stream 
>     h​as to be created. For the remote party, this looks like a ICE
>     restart as well.​
> 
> If I understand this correctly, if I want *new* candidates, I should
> replace the nice stream (e.g., nice_agent_remove_stream,
> nice_agent_add_stream). Otherwise, I should re-signal the old
> candidates?
> ​
> Zachary HuerasPrincipal Software Engineer
> AMD Global Telemedicine, Inc.
> Cell : 978-660-3812
> zhueras at amdtelemedicine.com
> www.amdtelemedicine.com | Follow us on LinkedIn
> From: nice <nice-bounces at lists.freedesktop.org> on behalf of Zachary
> Hueras <ZHueras at amdtelemedicine.com>
> Sent: Monday, December 14, 2020 2:23 AM
> To: nice at lists.freedesktop.org
> Subject: [libnice] nice_agent_restart_stream: proper usage and local
> candidate gathering with gstreamer 
> Hello,
> 
> I'm trying to implement ICE restarts with gstreamer's webrtcbin. The
> thing I can't seem to figure out is how to get libnice to gather
> local candidates again. Or is this not supposed to happen?
> 
> As it stands, I:
> 
> - successfully generate a session description with new ufrag and pwd
> - set-local-description on webrtcbin
> - detect the changed credentials in GstWebRTCICEStream
> - invoke nice_agent_set_local_credentials​
> - invoke nice_agent_restart_stream
> - incidentally invoke nice_agent_gather_candidates (again)
> 
> However, no candidates appear to be added after this point. Is there
> something I'm missing?
> 
> When I connect this to a simple-peer based WebRTC application, and
> restart a successful connection, only the simple-peer side sends new
> candidates, and the connection eventually progresses to
> "disconnected" and ultimately "failed". I'm not sure if I'm just
> missing something from the gstreamer side, or if libnice is supposed
> to provide new candidates after a restart.
> 
> Any and all guidance is welcome.​
> 
> Zachary HuerasPrincipal Software Engineer
> AMD Global Telemedicine, Inc.
> Cell : 978-660-3812
> zhueras at amdtelemedicine.com
> www.amdtelemedicine.com | Follow us on LinkedIn
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-- 
Olivier Crête
olivier.crete at collabora.com

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