[tor-bugs] #18628 [Obfuscation/Snowflake]: Devise some way for the browser proxy to forward metadata to the bridge before the OR data

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#18628: Devise some way for the browser proxy to forward metadata to the bridge
before the OR data
-----------------------------------+------------------------------
 Reporter:  arlolra                |          Owner:
     Type:  defect                 |         Status:  needs_review
 Priority:  High                   |      Milestone:
Component:  Obfuscation/Snowflake  |        Version:
 Severity:  Normal                 |     Resolution:
 Keywords:                         |  Actual Points:
Parent ID:                         |         Points:
 Reviewer:                         |        Sponsor:
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Comment (by dcf):

 Replying to [comment:8 dcf]:
 > Replying to [comment:6 cmm32]:
 > I know that in comment:5 I made a fuss about moving the SDP parsing
 logic into webrtcConn.RemoteAddr. But for some reason, doing that makes it
 stop working for me to run proxy-go and snowflake-client on the same
 computer! The code hangs forever inside the call to
 c.pc.RemoteDescription(). I don't know why (it might be a bug in go-
 webrtc), but I bisected and
 [https://gitweb.torproject.org/user/dcf/snowflake.git/commit/?h=bug18628&id=2c0cfdfb953d3b37254c0a4dff5b61ca2be795cf
 2c0cfdfb] is definitely the commit that causes a change. So as a
 workaround, we might need to put the SDP parsing back where it was, until
 we figure out the cause. I can do that, if it's okay with you, because I'm
 easily able to reproduce the problem.

 Okay, I applied
 [https://gitweb.torproject.org/user/dcf/snowflake.git/commit/?h=bug18628&id=be4c2fdd5e0780d11386e7157cf92a9ea035b4c3
 a small workaround]: just calls conn.RemoteAddr() before entering the
 goroutine instead of inside. I wonder if there is some kind of locking
 around RemoteDescription that was making it hang when called from
 different threads.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/18628#comment:9>
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