[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:  (none)
     Type:  defect                 |         Status:  new
 Priority:  Medium                 |      Milestone:
Component:  Obfuscation/Snowflake  |        Version:
 Severity:  Normal                 |     Resolution:
 Keywords:                         |  Actual Points:
Parent ID:                         |         Points:
 Reviewer:                         |        Sponsor:
-----------------------------------+------------------------

Comment (by dcf):

 Here's a graph of the number of file descriptors held open by the
 snowflake-client process while I was using it today. The first plateau at
 21:30 is when it stopped working and I turned off snowflake in the
 browser. snowflake-client continued running, got out of whatever rut it
 was in, and consumed a few more descriptors before I finally closed the
 browser.

 [[Image(snowflake-client-fds-20170814.png)]]

 The descriptors are six-fd repetitions of this nature. I suspect there's
 one for each attempt to contact the broker (i.e. `---- Handler: snowflake
 assigned ----`).
 {{{
 snowflake 28366 david  217w     FIFO       0,10      0t0 1150258477 pipe
 snowflake 28366 david  218r     FIFO       0,10      0t0 1150258478 pipe
 snowflake 28366 david  219w     FIFO       0,10      0t0 1150258478 pipe
 snowflake 28366 david  220u     IPv4 1150257563      0t0        UDP
 xx.Berkeley.EDU:48700
 snowflake 28366 david  221u     IPv4 1150258488      0t0        TCP
 xx.Berkeley.EDU:46037 (LISTEN)
 snowflake 28366 david  222r     FIFO       0,10      0t0 1150262588 pipe
 snowflake 28366 david  223w     FIFO       0,10      0t0 1150262588 pipe
 snowflake 28366 david  224r     FIFO       0,10      0t0 1150262589 pipe
 snowflake 28366 david  225w     FIFO       0,10      0t0 1150262589 pipe
 snowflake 28366 david  226u     IPv4 1150260856      0t0        UDP
 xx.Berkeley.EDU:49943
 snowflake 28366 david  227u     IPv4 1150262068      0t0        TCP
 xx.Berkeley.EDU:52465 (LISTEN)
 }}}

 During the plateau at 21:30, there were a lot of `Buffered` messages in
 the log:
 {{{
 2017/08/14 14:24:34 WebRTC: DataChannel.OnOpen
 2017/08/14 14:24:34 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:24:36 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:24:38 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:24:39 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:24:40 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:24:42 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:24:44 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:24:46 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:24:48 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:24:50 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:24:52 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:24:54 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:24:56 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:24:58 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:25:00 Buffered 1057 bytes --> WebRTC
 2017/08/14 14:25:01 Buffered 543 bytes --> WebRTC
 2017/08/14 14:25:02 Buffered 543 bytes --> WebRTC
 2017/08/14 14:25:03 Buffered 543 bytes --> WebRTC
 2017/08/14 14:25:03 WebRTC: No messages received for 30 seconds -- closing
 stale connection.
 2017/08/14 14:25:03 WebRTC: closing DataChannel
 2017/08/14 14:25:03 WebRTC: DataChannel.OnClose [locally]
 2017/08/14 14:25:03 WebRTC: closing PeerConnection
 2017/08/14 14:25:03 WebRTC: Closing
 2017/08/14 14:25:04 Buffered 543 bytes --> WebRTC
 2017/08/14 14:25:05 Buffered 543 bytes --> WebRTC
 2017/08/14 14:25:06 Buffered 543 bytes --> WebRTC
 2017/08/14 14:25:07 Buffered 543 bytes --> WebRTC
 }}}

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21312#comment:11>
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