[tor-bugs] #31385 [Circumvention/Snowflake]: Snowflake client fails after bootstrap

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#31385: Snowflake client fails after bootstrap
-------------------------------------+--------------------------
 Reporter:  cypherpunks              |          Owner:  cohosh
     Type:  defect                   |         Status:  assigned
 Priority:  Medium                   |      Milestone:
Component:  Circumvention/Snowflake  |        Version:
 Severity:  Normal                   |     Resolution:
 Keywords:                           |  Actual Points:
Parent ID:                           |         Points:
 Reviewer:                           |        Sponsor:
-------------------------------------+--------------------------

Comment (by cohosh):

 I was able to reproduce this after updating Tor Browser. The client worked
 fine before the update:

 {{{
 2019/08/12 15:25:00 WebRTC: At capacity [1/1]  Retrying in 10 seconds...
 2019/08/12 15:25:01 Traffic Bytes (in|out): 543 | 543 -- (1 OnMessages, 1
 Sends)
 2019/08/12 15:25:07 Traffic Bytes (in|out): 1086 | 1086 -- (2 OnMessages,
 2 Sends)
 2019/08/12 15:25:10 WebRTC: At capacity [1/1]  Retrying in 10 seconds...
 2019/08/12 15:25:12 Traffic Bytes (in|out): 543 | 1600 -- (1 OnMessages, 2
 Sends)
 2019/08/12 15:25:18 Traffic Bytes (in|out): 1086 | 1086 -- (2 OnMessages,
 2 Sends)
 2019/08/12 15:25:18 WebRTC: closing DataChannel
 2019/08/12 15:25:18 ConnectLoop: stopped.
 2019/08/12 15:25:18 copy loop ended
 2019/08/12 15:25:18 ---- Handler: closed ---
 2019/08/12 15:25:18 WebRTC: DataChannel.OnClose [locally]
 2019/08/12 15:25:18 WebRTC: closing PeerConnection
 2019/08/12 15:25:18 WebRTC: Closing
 2019/08/12 15:25:18 WebRTC: melted all 1 snowflakes.
 2019/08/12 15:25:18 SOCKS listening...
 2019/08/12 15:25:18 snowflake is done.
 }}}

 But afterwards, I got repeated behaviour where data is going out but no
 data is coming back in:
 {{{
 2019/08/12 [scrubbed] Received Answer.
 2019/08/12 [scrubbed] WebRTC: DataChannel.OnOpen
 2019/08/12 [scrubbed] Buffered 1057 bytes --> WebRTC
 2019/08/12 [scrubbed] Traffic Bytes (in|out): 0 | 1057 -- (0 OnMessages, 1
 Sends)
 2019/08/12 [scrubbed] Buffered 543 bytes --> WebRTC
 2019/08/12 [scrubbed] Traffic Bytes (in|out): 0 | 543 -- (0 OnMessages, 1
 Sends)
 2019/08/12 [scrubbed] Buffered 543 bytes --> WebRTC
 2019/08/12 [scrubbed] WebRTC: No messages received for 30 seconds --
 closing stale connection.
 2019/08/12 [scrubbed] WebRTC: closing DataChannel
 2019/08/12 [scrubbed] WebRTC: DataChannel.OnClose [locally]
 2019/08/12 [scrubbed] WebRTC: closing PeerConnection
 2019/08/12 [scrubbed] WebRTC: Closing
 2019/08/12 [scrubbed] Traffic Bytes (in|out): 0 | 543 -- (0 OnMessages, 1
 Sends)
 2019/08/12 [scrubbed] Buffered 543 bytes --> WebRTC
 2019/08/12 [scrubbed] Traffic Bytes (in|out): 0 | 543 -- (0 OnMessages, 1
 Sends)
 2019/08/12 [scrubbed] Buffered 543 bytes --> WebRTC
 2019/08/12 [scrubbed] Traffic Bytes (in|out): 0 | 543 -- (0 OnMessages, 1
 Sends)
 2019/08/12 [scrubbed] Buffered 543 bytes --> WebRTC
 2019/08/12 [scrubbed] Traffic Bytes (in|out): 0 | 543 -- (0 OnMessages, 1
 Sends)
 2019/08/12 [scrubbed] Buffered 1571 bytes --> WebRTC
 }}}

 This could be either a bug at the client or just by chance that the pre-
 update version got a good proxy.

 I also just made #31403 because our over-zealous log scrubber fix and the
 guards against large reads haven't made their way into Tor Browser yet

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/31385#comment:11>
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