Date: Fri, 22 Feb 2002 08:52:25 -0800 From: Lars Eggert <larse@ISI.EDU> To: John Polstra <jdp@polstra.com> Cc: net@freebsd.org Subject: Re: incorrect checksums with xl? Message-ID: <3C767749.3020302@isi.edu> References: <3C7547E0.8050805@isi.edu> <200202221643.g1MGhej38249@vashon.polstra.com>
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[-- Attachment #1 --] John, John Polstra wrote: > You are running tcpdump on the system that's sending the "bad" > packets, right? It makes perfect sense. The TCP/IP stack knows > that the NIC is going to insert the checksums, so it doesn't bother > calculating them itself. So BPF is handed packets in mbufs without > any checksums. On the way out to the wire, the NIC hardware/firmware > adds the checksums, but they don't show up in the mbufs that are being > sent to BPF. If you run tcpdump on the receiving system instead, > you'll find that the checksums seen there are valid. > > The same thing happens in the bge driver, because it also offloads > checksum generation to the NIC. that makes total sense. I'd like to see the paragraph above in big, bold letters in the xl(4) man page then - so far it doesn't discuss checksum offloading at all. :-) Thanks, Lars -- Lars Eggert <larse@isi.edu> Information Sciences Institute http://www.isi.edu/larse/ University of Southern California [-- Attachment #2 --] 0 *H 01 0 + 0 *H 00 G0 *H 01 0 UZA10U Western Cape10U Cape Town10 U Thawte1 0U Certificate Services1(0&U Personal Freemail RSA 2000.8.300 010824164000Z 020824164000Z0T10 UEggert1 0 U*Lars10U Lars Eggert1 0 *H larse@isi.edu00 *H 0 |\Pw v~~ FDooӦA\- Cˀ4.)&{肋 ,z (ܷر߈T7_'txGH^tt/ҹB8%t<#ֲN V0T0*+e!0 00L2uMyffBNUbNJJcdZ2s0U 0 larse@isi.edu0 U 0 0 *H aJPMՒ ]cѭC+kS+wZ1gY",YT41 j 6:~℩ D~Kؚl=u(ՎM?cF7@}T00 G0 *H 01 0 UZA10U Western Cape10U Cape Town10 U Thawte1 0U Certificate Services1(0&U Personal Freemail RSA 2000.8.300 010824164000Z 020824164000Z0T10 UEggert1 0 U*Lars10U Lars Eggert1 0 *H larse@isi.edu00 *H 0 |\Pw v~~ FDooӦA\- Cˀ4.)&{肋 ,z (ܷر߈T7_'txGH^tt/ҹB8%t<#ֲN V0T0*+e!0 00L2uMyffBNUbNJJcdZ2s0U 0 larse@isi.edu0 U 0 0 *H aJPMՒ ]cѭC+kS+wZ1gY",YT41 j 6:~℩ D~Kؚl=u(ՎM?cF7@}T0)0 0 *H 01 0 UZA10U Western Cape10U Cape Town10U Thawte Consulting1(0&U Certification Services Division1$0"UThawte Personal Freemail CA1+0) *H personal-freemail@thawte.com0 000830000000Z 020829235959Z01 0 UZA10U Western Cape10U Cape Town10 U Thawte1 0U Certificate Services1(0&U Personal Freemail RSA 2000.8.3000 *H 0 32c %E>nx'gڈD)c5*mp<ܮto034qmOe KaU5u'rװ |CBPQ<9TIf - ki N0L0)U "0 0 10UPrivateLabel1-2970U 0 0 U 0 *H so&e4KYbDI j&*b ct mSK8P:l4撜n# KrgPo.X PW Ո9[9}4%MjÑ/<RbH10001 0 UZA10U Western Cape10U Cape Town10 U Thawte1 0U Certificate Services1(0&U Personal Freemail RSA 2000.8.30G0 + a0 *H 1 *H 0 *H 1 020222165225Z0# *H 1Ka5&lӭ\Z0R *H 1E0C0 *H 0*H 0 *H @0+0 *H (0 *H 101 0 UZA10U Western Cape10U Cape Town10 U Thawte1 0U Certificate Services1(0&U Personal Freemail RSA 2000.8.30G0 *H s0M܁|X_CХ/GksQQDēH" .k$Rsax<0K,f{F0n눵 zGZ{Ǫ,Uv^"Sq+}Z
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