1348579 - 'failed to create passive TCP host candidate' when attempting to enter Discord voice channel

Status: RESOLVED INVALID

(Core :: WebRTC: Networking, defect, P2)

Description

[Shane Bundy]

Attachment: Connection log from about:webrtc

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:55.0) Gecko/20100101 Firefox/55.0
Build ID: 20170318030202

Steps to reproduce:

1. Sign in to Discord (discordapp.com)
2. Find a group and enter a voice channel


Actual results:

Discord claims to be connected while the console stays on the output 'Sending local SDP to voice server'. about:webrtc spews an error saying it was unable to create a passive TCP host candidate.


Expected results:

Discord should have connected without error.

Comment 1

[Shane Bundy]

This started to happen on the March 17th Nightly although it may have crept in to March 16th's one also. Disabling ICE TCP reduces the spew but does not resolve the issue.

Comment 2

[Nils Ohlmeier [:drno]]

Tired it with Nightly 2017-03-15 and 2017-03-19 and I no longer see ICE connecting. I'm not aware of any bigger changes in our ICE stack which would explain this. I think we can safely ignore the ICE TCP error messages, as the discord server never even offers ICE TCP.
What looks strange to me is that the discord server advertises as the SSRC for the audio RTP stream 0. That is at least not very clever, if not broken. But even with that SSRC number ICE should connect.

Comment 3

[Nils Ohlmeier [:drno]]

The problem is that the discord voice server in it's SDP answer sends back:
  a=setup:actpass

As Firefox offered a=setup:actpass the answerer needs to send back either a=setup:active or a=setup:passive.

And it would be good if the discord JS code would also check for errors thrown when doing the SetRemoteDescription() call, because Firefox throws an error/returns a promise failure which points out this error in the answer SDP.

Comment 4

[Randell Jesup [:jesup] (needinfo me)]

Side-note for Discord - there's evil code in the  webrtc.org codebase that Chrome and we (and Safari will) use, which disallows SSRC's of 0 - it uses that as a flag for "not set".  (Ugh)

Comment 5

[Shane Bundy]

I've filed a bug report with the Discord guys. I'll update this with their response.