Date: Sun, 06 Jul 1997 17:53:37 -0700 From: David Greenman <dg@root.com> To: Archie Cobbs <archie@whistle.com> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: VJ compression and MAX_HDR Message-ID: <199707070053.RAA18621@implode.root.com> In-Reply-To: Your message of "Sun, 06 Jul 1997 16:56:47 PDT." <199707062356.QAA13745@bubba.whistle.com>
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>> This means that when Van Jacobson compression is active, any packets >> sent to us with combined IP and TCP header length greater than MLEN >> will be dropped, always. >> >> This is an admittedly rare case, but my question is, why was this >> done? What code would break if MAX_HDR is changed back to 128? ... >After further review, it looks like the genesis of this change is >the fact that sl_compress_tcp() requires the full TCP/IP headers >to lie within the first mbuf, and sl_uncompress_tcp() requires the >TCP/IP header (in the TYPE_UNCOMPRESSED_TCP case) to also be in a >contiguous buffer... > >Plus the fact that m_pullup() won't work for values greater than MHLEN >doesn't help. 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. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
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