[bug #27905] FIN isn't combined with data sent

[Sylvain Beucler-4]

URL:
  <http://savannah.nongnu.org/bugs/?27905>

                 Summary: FIN isn't combined with data sent
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: goldsimon
            Submitted on: So 01 Nov 2009 17:20:41 GMT
                Category: TCP
                Severity: 3 - Normal
              Item Group: Change Request
                  Status: Need Info
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release:
            lwIP version: CVS Head

    _______________________________________________________

Details:

In tcp_enqueue, we currently don't combine FIN segments to the last unsent.
Does anybody know why? I would have thought that this would be a good idea to
keep the number of segments sent low.

I.e. the httpd closes a connection right after all data is enqueued
successfully. Although the enqueued segments are still on unsent (tcp_output
hasn't been called, yet), FIN always results in a new segment.




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[Sylvain Beucler-4]

Update of bug #27905 (project lwip):

                 Summary: FIN isn't combined with data sent => FIN isn't
combined with data on unsent


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[Sylvain Beucler-4]

Follow-up Comment #1, bug #27905 (project lwip):

It was probably just simpler that way.  I don't think this is a big deal.
Whichever results in smaller code is best.

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[Sylvain Beucler-4]

Follow-up Comment #2, bug #27905 (project lwip):

I spotted this while working on the raw api httpd: with HTTP/1.1, the server
currently sends "Connection: close" because it closes the connection after
each request/response. However, since the actual FIN needs a while, it happens
often that the FINs are sent at the same time, resulting in duplicate FINs and
ACKs.

This is of course not really wrong behaviour, but it would be nicer to
prevent duplicate ACKs if we can. I'll test how much code change it would
be...

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[Sylvain Beucler-4]

Update of bug #27905 (project lwip):

                  Status:               Need Info => Fixed                  
             Assigned to:                    None => goldsimon              
             Open/Closed:                    Open => Closed                

    _______________________________________________________

Follow-up Comment #3:

Fixed since the code change is rather small and the code size doesn't change
much, too.

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