[lwip-devel] [bug #28098] Nagle can prevent fast retransmit from sending segment

[Harry Bryson]

URL:
  <http://savannah.nongnu.org/bugs/?28098>

                 Summary: Nagle can prevent fast retransmit from sending
segment
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: hbryson
            Submitted on: Thu 26 Nov 2009 11:37:54 GMT
                Category: TCP
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: 
            lwIP version: 1.3.1

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Details:

If fast retransmit (tcp_rexmit() from tcp_receive()) attempts to output a
segment, the segment can be blocked by Nagle algorithm (if it matches the
appropriate criteria). It should not be.

If a slow retransmission occurs after the above event(tcp_rexmit_rto()), the
previous "stuck" segment is queued behind all its subsequent segments in the
unsent queue. When the unsent queue is output, the "stuck" segment will again
be prevented by Nagle from getting transmitted.

If no sunsequent data is enqueued to TCP (e.g. TCP PCB is "full"), the above
condition is persistent and the connection will stall and eventually fail.




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