[tor-bugs] #28942 [Circumvention/Snowflake]: Evaluate pion WebRTC

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#28942: Evaluate pion WebRTC
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 Reporter:  backkem                         |          Owner:  cohosh
     Type:  enhancement                     |         Status:  accepted
 Priority:  Medium                          |      Milestone:
Component:  Circumvention/Snowflake         |        Version:
 Severity:  Normal                          |     Resolution:
 Keywords:  anti-censorship-roadmap-august  |  Actual Points:
Parent ID:                                  |         Points:  5
 Reviewer:                                  |        Sponsor:
                                            |  Sponsor28-must
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Comment (by cohosh):

 Replying to [comment:52 cohosh]:
 > Well I can narrow down that at least one problem I'm having using just
 master versions of pion dependencies from the snowflake
 [https://github.com/cohosh/snowflake/commit/3cc240625cad22db02eca7af41b139606c13147d
 pion branch] is due to ICE not gathering any candidates.
 >
 > For me the client isn't even contacting the broker, but stalling in
 `exchangeSDP`
 [https://github.com/cohosh/snowflake/blob/pion/client/lib/webrtc.go#L298
 L298] waiting for an offer to be sent from when the ICE gathering is
 completed
 [https://github.com/cohosh/snowflake/blob/pion/client/lib/webrtc.go#L174
 L174]. I don't see any log messages from `OnICECandidate`.

 Found the introduction of at least one breaking change
 [https://github.com/pion/webrtc/commit/7c18bbcceed776b547a44a0b921284db7d4bc69a
 #diff-d2ee665bb8c62c914fee5e9c743be25cR1034 here]

 This is the cause for ICE not working at the client side. The reason is
 that we use the new Trickle method of gathering ICE candidates (this was
 necessary to get pion working at the client, as outlined in comment:28).
 I'm not sure why this specific change at R1034 was merged, since it
 doesn't seem to have anything to do with the commit message and I can't
 figure out it's purpose.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28942#comment:53>
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