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Date:      Thu, 24 Jun 1999 16:05:15 +0200 (MET DST)
From:      Luigi Rizzo <luigi@labinfo.iet.unipi.it>
To:        hackers@freebsd.org
Subject:   weird socket behaviour (sbflush)...
Message-ID:  <199906241405.QAA01215@labinfo.iet.unipi.it>

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Hi,

while implementing a reliable datagram protocol (PGM for what matters)
i am hitting a weird behaviour of sbflush().

The problem is, the protocol (at least, in my implementation)
allows the writing of zero-sized packets (essentially, just headers
and no payload) which are put in the socket buffer.
This results in some cases in sb_cc = 0, sb_mbcnt != 0, and this
condition causes sbflush to panic.

There is not an equivalent of this in TCP (which counts bytes, not
segments) or UDP (which allows zero-sized packets but bypasses the
socket buffer) so i am not sure if it is appropriate to "fix" sbflush()
so that it uses sbdroprecord() instead of sbdrop() in case of a
datagram protocol ?

	cheers
	luigi
-----------------------------------+-------------------------------------
  Luigi RIZZO, luigi@iet.unipi.it  . Dip. di Ing. dell'Informazione
  http://www.iet.unipi.it/~luigi/  . Universita` di Pisa
  TEL/FAX: +39-050-568.533/522     . via Diotisalvi 2, 56126 PISA (Italy)

		  http://www.iet.unipi.it/~luigi/ngc99/
====  First International Workshop on Networked Group Communication  ====
-----------------------------------+-------------------------------------


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