Date: Mon, 12 Jan 2004 00:10:43 -0500 From: David Gilbert <dgilbert@dclg.ca> To: Andre Oppermann <andre@freebsd.org> Cc: David Gilbert <dgilbert@dclg.ca> Subject: Re: off-by-one error in ip_fragment, recently. Message-ID: <16386.11347.853356.826784@canoe.dclg.ca> In-Reply-To: <40008FCD.90525A33@freebsd.org> References: <16384.14322.83258.940369@canoe.dclg.ca> <40008783.330FAFF4@freebsd.org> <40008FCD.90525A33@freebsd.org>
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One more update before I go to bed. On major change in if_gre.c has been to change gh->gi_len = m->m_pkthdr.len; to gh->gi_len = htons(m->m_pkthdr.len); ... which is a fairly semantic change. Now ip_output() is called immediately after that ... and ip_output seems to expect the length in the packet to still be host order because it has: if ((ifp->if_snd.ifq_len + ip->ip_len / ifp->if_mtu + 1) >= as one of the first things that are done with ip->ip_len... or am I mussing that up? ip_output then goes on to call htons() on ip->ip_len many more times, and I'm too tired to track it reliably. But, if I revert the change in if_gre.c, the kernel doesn't crash ... but the gre tunnel also doesn't work. It would appear the byte swap happens a few more times before ip_fragment(). But... what I do know is that in the -CURRENT code, the values that arrive in ip->ip_len in ip_fragment() from the gre tunnel are the byteswapped values from m->m_pkthdr.len above. ... which makes me wonder if this is a showstopper ... that ip_fragment() is broken in some general way. Dave. -- ============================================================================ |David Gilbert, Independent Contractor. | Two things can only be | |Mail: dave@daveg.ca | equal if and only if they | |http://daveg.ca | are precisely opposite. | =========================================================GLO================
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