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Date:      Thu, 4 Nov 1999 15:44:45 -0600 (CST)
From:      Jonathan Lemon <jlemon@americantv.com>
To:        ken@kdm.org, current@freebsd.org
Subject:   Re: TCP sockets stuck in the CLOSING state
Message-ID:  <199911042144.PAA20756@free.pcs>
In-Reply-To: <local.mail.freebsd-current/199911042000.NAA91632@panzer.kdm.org>

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In article <local.mail.freebsd-current/199911042000.NAA91632@panzer.kdm.org> you write:
>
>Before I spend a lot of time hunting this down, I figured it might be worth
>asking -- is there any particular reason why TCP sockets may be getting
>stuck in the CLOSING state more often now?

Not sure.  But here's a tcpdump trace of a socket that ends up in the
CLOSING state.  (on the host ``cache'').

14:55:49.142607 folly.56982 > cache.9000: S 1691420120:1691420120(0) win 16384 <mss 1460> (DF)
14:55:49.142663 cache.9000 > folly.56982: S 1946461253:1946461253(0) ack 1691420121 win 17520 <mss 1460> (DF)
14:55:49.142991 folly.56982 > cache.9000: . ack 1 win 17520 (DF)
14:55:49.143384 folly.56982 > cache.9000: P 1:188(187) ack 1 win 17520 (DF)
14:55:49.340283 cache.9000 > folly.56982: . ack 188 win 17520 (DF)
14:55:50.287660 cache.9000 > folly.56982: P 1:1442(1441) ack 188 win 17520 (DF)
14:55:50.484537 cache.9000 > folly.56982: . 1442:2902(1460) ack 188 win 17520 (DF)
14:55:50.484552 cache.9000 > folly.56982: P 2902:4362(1460) ack 188 win 17520 (DF)
14:55:50.490171 cache.9000 > folly.56982: P 4362:4781(419) ack 188 win 17520 (DF)
14:55:50.490369 cache.9000 > folly.56982: F 4781:4781(0) ack 188 win 17520 (DF)
14:55:50.492154 folly.56982 > cache.9000: . ack 4781 win 17520 (DF)
14:55:50.492160 folly.56982 > cache.9000: F 188:188(0) ack 4781 win 17520 (DF)
14:55:50.492229 cache.9000 > folly.56982: . ack 189 win 17520 (DF)
14:55:51.490279 cache.9000 > folly.56982: . ack 189 win 17520 (DF)

Note that I think there are at least two oddities here:

    1. the other end (folly) never acks the FIN.  The packets at 
       timestamp .492154 and .492160 do not cover the FIN in the
       sequence space.  Yet the host `folly' closes the socket.

    2. the end that is stuck in CLOSING (cache) never retransmits 
       the FIN.  (The tcpdump extends for about 5 minutes after the
       last packet, with 0 packets lost).

Both machines are running -current from early this week.
--
Jonathan


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