From owner-freebsd-hackers  Sun Jul  6 20:58:43 1997
Return-Path: <owner-hackers>
Received: (from root@localhost)
          by hub.freebsd.org (8.8.5/8.8.5) id UAA21832
          for hackers-outgoing; Sun, 6 Jul 1997 20:58:43 -0700 (PDT)
Received: from alpha.xerox.com (alpha.Xerox.COM [13.1.64.93])
          by hub.freebsd.org (8.8.5/8.8.5) with SMTP id UAA21827
          for <freebsd-hackers@freebsd.org>; Sun, 6 Jul 1997 20:58:41 -0700 (PDT)
Received: from crevenia.parc.xerox.com ([13.2.116.11]) by alpha.xerox.com with SMTP id <15380(1)>; Sun, 6 Jul 1997 20:58:09 PDT
Received: from localhost by crevenia.parc.xerox.com with SMTP id <177512>; Sun, 6 Jul 1997 20:57:58 -0700
To: dg@root.com
cc: Archie Cobbs <archie@whistle.com>, freebsd-hackers@freebsd.org
Subject: Re: VJ compression and MAX_HDR 
In-reply-to: Your message of "Sun, 06 Jul 97 17:53:37 PDT."
             <199707070053.RAA18621@implode.root.com> 
Date: Sun, 6 Jul 1997 20:57:57 PDT
From: Bill Fenner <fenner@parc.xerox.com>
Message-Id: <97Jul6.205758pdt.177512@crevenia.parc.xerox.com>
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

David Greenman <dg@root.com> wrote:
>   I think the case of IP+TCP header > MLEN is more than rare...I think it 
>never happens. Even with all options, the IP header doesn't exceed 64 bytes.

Both IP and TCP headers have maximum lengths of 60 bytes.  A maximum size
IP + max size TCP header, however, is 120 bytes, which > MLEN.

sl_compress_tcp() requires the IP and TCP headers to be contiguous; the
only way to require that without requiring them to be shorter than MLEN
is to require that sl_compress_tcp() be passed a cluster mbuf.  Failing
that, the code that checks TCP options (maybe just the last BCMP in the
check-if-we-should-send-this-one-compressed) needs to learn about mbuf
chains.

  Bill