Date: Sun, 8 Feb 2009 21:42:53 +1100 From: Peter Jeremy <peter@vk2pj.dyndns.org> To: Danny Braniss <danny@cs.huji.ac.il> Cc: freebsd-stable@freebsd.org Subject: Re: impossible packet length ... Message-ID: <20090208104253.GB31876@test71.vk2pj.dyndns.org> In-Reply-To: <E1LW60v-0000zC-B2@kabab.cs.huji.ac.il> References: <E1LW5Ht-0000VH-D8@kabab.cs.huji.ac.il> <20090208091656.GA31876@test71.vk2pj.dyndns.org> <E1LW60v-0000zC-B2@kabab.cs.huji.ac.il>
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--ZoaI/ZTpAVc4A5k6 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2009-Feb-08 11:31:45 +0200, Danny Braniss <danny@cs.huji.ac.il> wrote: >Q: with rxcsum on, and a bad checksum packet is received, is it > dropped by the NIC? if not, then it somewhat explains the behaviour If checksum offloading is working correctly then a bad packet should be dropped by the NIC. If checksum offloading isn't working correctly then you can wind up in the situation where both the NIC and the driver think the other party has verified the checksum. It's also possible that you may be running into corruption during DMA transfer =66rom the NIC to RAM. ISTR there have been some issues reported recently with checksum offloading on some NICs - though I don't have details to hand - you might like to search the lists. >changing the nic is tough, but if needed will be done.=20 If disabling checksum offloading fixes the problem and the additional CPU load is acceptable (at least until you find a real fix) then there's no need to change NICs. --=20 Peter Jeremy --ZoaI/ZTpAVc4A5k6 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.10 (FreeBSD) iEYEARECAAYFAkmOty0ACgkQ/opHv/APuIecbgCeKUBqmqvYE/t/UJv/Z03h7ZaM KnUAn0yYadZJgChKjSUatT1NgPAAkYJk =YD1D -----END PGP SIGNATURE----- --ZoaI/ZTpAVc4A5k6--
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