[lwip-devel] [bug #26010] PSH bit not set correctly when segments are merged

[Kieran Mansley]

URL:
  <http://savannah.nongnu.org/bugs/?26010>

                 Summary: PSH bit not set correctly when segments are merged
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: kieranm
            Submitted on: Thu 26 Mar 2009 14:37:44 GMT
                Category: TCP
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: kieranm
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: 1.3.1
            lwIP version: CVS Head

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Details:

I've noticed that when we merge segments in tcp_enqueue, we fail to set the
PSH bit correctly.

After merging the segment we free the tail, and so set our reference (seg) to
that to NULL.

Later in the function we do this:

  if (seg != NULL && seglen > 0 && seg->tcphdr != NULL &&
      ((apiflags & TCP_WRITE_FLAG_MORE)==0)) {
    TCPH_SET_FLAG(seg->tcphdr, TCP_PSH);
  }

By setting seg to NULL we prevent the setting of the PSH flag, even though we
would had the segments not been merged.

I propose setting seg = useg (and seglen = useg->len) instead of to NULL. 
This will mean the code that sets the PSH flag should then work correctly.

Patch attached.  Any objections?



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File Attachments:


-------------------------------------------------------
Date: Thu 26 Mar 2009 14:37:44 GMT  Name: psh  Size: 417B   By: kieranm

<http://savannah.nongnu.org/bugs/download.php?file_id=17806>

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