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Date: Sun, 06 Jul 1997 21:46:19 -0400
To: dg@root.com, Archie Cobbs <archie@whistle.com>
From: Matt Thomas <matt@3am-software.com>
Subject: Re: VJ compression and MAX_HDR 
Cc: freebsd-hackers@FreeBSD.ORG
In-Reply-To: <199707070053.RAA18621@implode.root.com>
References: <Your message of "Sun, 06 Jul 1997 16:56:47 PDT."             <199707062356.QAA13745@bubba.whistle.com>
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At 05:53 PM 7/6/97 -0700, David Greenman wrote:
>>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.

But the maximum TCP header is also 64 bytes so it could be > MLEN.  
For now it isn't probable since few TCP options exist to push the
TCP header beyond 32 byte mark.  SACK will push that close to the
limit however.


-- 
Matt Thomas               Internet:   matt@3am-software.com
3am Software Foundry      WWW URL:    http://www.3am-software.com/bio/matt.html
Westford, MA              Disclaimer: I disavow all knowledge of this message