[tor-bugs] #21312 [Obfuscation/Snowflake]: snowflake-client is pegged at 100% cpu

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#21312: snowflake-client is pegged at 100% cpu
-----------------------------------+--------------------------
 Reporter:  arlolra                |          Owner:  arlolra
     Type:  defect                 |         Status:  assigned
 Priority:  High                   |      Milestone:
Component:  Obfuscation/Snowflake  |        Version:
 Severity:  Major                  |     Resolution:
 Keywords:                         |  Actual Points:
Parent ID:                         |         Points:
 Reviewer:                         |        Sponsor:
-----------------------------------+--------------------------

Comment (by cypherpunks):

 @dcf I'm seeing 80-120sec interruptions at times following your change
 (it's definitely noticeable), looking at the snowflake.log at around the
 intervals in which it happens I found this,

 {{{
 10:54 WebRTC: Collecting a new Snowflake. Currently at [0/1]
 10:54 snowflake-<redacted-ID1>  connecting...
 10:54 WebRTC: PeerConnection created.
 10:54 WebRTC: OnNegotiationNeeded
 10:54 WebRTC: DataChannel created.
 .
 .
 .
 11:10 ---- Handler: snowflake assigned ----
 11:10 Buffered xxx bytes --> WebRTC
 11:10 WebRTC: DataChannel.OnOpen
 11:10 Flushed xxx bytes.
 11:10 Traffic Bytes (in|out): xxx | xx -- (1 OnMessages, 1 Sends)
 11:17 Traffic Bytes (in|out): xxxxx | xxxxx -- (35 OnMessages, 28 Sends)
 11:20 WebRTC: At capacity [1/1]  Retrying in 10 seconds...
 11:30 WebRTC: At capacity [1/1]  Retrying in 10 seconds...
 11:40 WebRTC: At capacity [1/1]  Retrying in 10 seconds...
 11:42 Traffic Bytes (in|out): xxxx | xxxx -- (1 OnMessages, 1 Sends)
 11:50 WebRTC: At capacity [1/1]  Retrying in 10 seconds...
 12:00 WebRTC: At capacity [1/1]  Retrying in 10 seconds...
 12:10 WebRTC: At capacity [1/1]  Retrying in 10 seconds...
 12:13 WebRTC: No messages received for 30 seconds -- closing stale
 connection.
 12:13 WebRTC: closing DataChannel
 12:13 WebRTC: DataChannel.OnClose [locally]
 12:13 WebRTC: closing PeerConnection
 12:13 WebRTC: Closing
 12:13 copy loop ended
 12:13 ---- Handler: closed ---
 12:13 SOCKS listening...
 12:14 SOCKS accepted:  {0.0.3.0:1  map[]}
 12:18 Traffic Bytes (in|out): 0 | xxxxx -- (0 OnMessages, 23 Sends)
 12:20 WebRTC: Collecting a new Snowflake. Currently at [0/1]
 12:20 snowflake-<redacted-ID2>  connecting...
 12:20 WebRTC: PeerConnection created.
 12:20 WebRTC: OnNegotiationNeeded
 12:20 WebRTC: DataChannel created.
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21312#comment:26>
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