[tor-bugs] #21305 [Obfuscation/Snowflake]: Client gets into an unrecoverable connect / close loop

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#21305: Client gets into an unrecoverable connect / close loop
---------------------------------------+-----------------
     Reporter:  arlolra                |      Owner:
         Type:  defect                 |     Status:  new
     Priority:  Medium                 |  Milestone:
    Component:  Obfuscation/Snowflake  |    Version:
     Severity:  Normal                 |   Keywords:
Actual Points:                         |  Parent ID:
       Points:                         |   Reviewer:
      Sponsor:                         |
---------------------------------------+-----------------
 This was after briefly losing internet connectivity.  It was just
 endlessly repeating this pattern.  We tried giving it a new proxy to
 connect to but with no luck.  Restarting the client immediately resolved
 the issue, so it seems to have got itself into a bad state.

 {{{
 2017/01/24 13:35:12 ---- Handler: closed ---
 2017/01/24 13:35:12 SOCKS listening...
 2017/01/24 13:35:12 SOCKS accepted:  {0.0.3.0:1  map[]}
 2017/01/24 13:35:14 WebRTC: Collecting a new Snowflake. Currently at [0/1]
 2017/01/24 13:35:14 snowflake-61xONPqOrMQ67aWl  connecting...
 2017/01/24 13:35:14 WebRTC: PeerConnection created.
 2017/01/24 13:35:14 WebRTC: OnNegotiationNeeded
 2017/01/24 13:35:14 WebRTC: DataChannel created.
 2017/01/24 13:35:14 candidate:4096217215 1 udp 2122260223 192.168.1.154
 40594 typ host generation 0 ufrag ko968AKONjQ/Rpya network-id 1
 2017/01/24 13:35:14 candidate:1970230987 1 udp 1686052607 108.16.226.229
 40594 typ srflx raddr 192.168.1.154 rport 40594 generation 0 ufrag
 ko968AKONjQ/Rpya network-id 1
 2017/01/24 13:35:14 candidate:3131354255 1 tcp 1518280447 192.168.1.154
 53340 typ host tcptype passive generation 0 ufrag ko968AKONjQ/Rpya
 network-id 1
 2017/01/24 13:35:14 WebRTC: OnIceComplete
 2017/01/24 13:35:14 Negotiating via BrokerChannel...
 Target URL:  snowflake-reg.appspot.com
 Front URL:   www.google.com
 2017/01/24 13:35:14 BrokerChannel Response:
 200 OK

 2017/01/24 13:35:14 Received Answer:

 v=0
 o=mozilla...THIS_IS_SDPARTA-51.0 6797456362141212310 0 IN IP4 0.0.0.0
 s=-
 t=0 0
 a=sendrecv
 a=fingerprint:sha-256
 A8:2C:FA:1D:33:46:8F:57:5D:56:AC:5C:EF:32:B5:8D:8E:2C:A5:FD:8E:33:6E:88:DD:5F:CC:4A:8B:02:BA:64
 a=ice-options:trickle
 a=msid-semantic:WMS *
 m=application 38953 DTLS/SCTP 5000
 c=IN IP4 88.159.72.23
 a=candidate:0 1 UDP 2122252543 88.159.72.23 38953 typ host
 a=sendrecv
 a=end-of-candidates
 a=ice-pwd:acc3c9ec8efb8d0a16a500203da69560
 a=ice-ufrag:6cb61e26
 a=mid:data
 a=sctpmap:5000 webrtc-datachannel 256
 a=setup:active
 a=ssrc:2244974687 cname:{c72775ac-0151-48b1-9063-0922a11994e6}

 2017/01/24 13:35:14 ---- Handler: snowflake assigned ----
 2017/01/24 13:35:14 Buffered 218 bytes --> WebRTC
 2017/01/24 13:35:14 WebRTC: DataChannel.OnOpen
 2017/01/24 13:35:14 Flushed 218 bytes.
 2017/01/24 13:35:16 Traffic Bytes (in|out): 749 | 218 -- (1 OnMessages, 1
 Sends)
 2017/01/24 13:35:23 Traffic Bytes (in|out): 4803 | 3907 -- (8 OnMessages,
 7 Sends)
 2017/01/24 13:35:24 WebRTC: At capacity [1/1]  Retrying in 10 seconds...
 2017/01/24 13:35:34 WebRTC: At capacity [1/1]  Retrying in 10 seconds...
 2017/01/24 13:35:44 WebRTC: At capacity [1/1]  Retrying in 10 seconds...
 2017/01/24 13:35:49 WebRTC: No messages received for 30 seconds -- closing
 stale connection.
 2017/01/24 13:35:49 WebRTC: closing DataChannel
 2017/01/24 13:35:49 WebRTC: DataChannel.OnClose [locally]
 2017/01/24 13:35:49 WebRTC: closing PeerConnection
 2017/01/24 13:35:49 WebRTC: Closing
 2017/01/24 13:35:49 copy loop ended
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21305>
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