Date: Fri, 15 Jan 2010 11:32:35 -0800 From: Pyun YongHyeon <pyunyh@gmail.com> To: alan bryan <alan.bryan@yahoo.com> Cc: freebsd-stable@freebsd.org Subject: Re: General problems with checksums (txcsum/rxcsum) on FreeBSD 8.0? Message-ID: <20100115193235.GH1228@michelle.cdnetworks.com> In-Reply-To: <491716.58173.qm@web50503.mail.re2.yahoo.com> References: <491716.58173.qm@web50503.mail.re2.yahoo.com>
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On Fri, Jan 15, 2010 at 11:12:43AM -0800, alan bryan wrote: > I just read a different thread about problems with checksums on vge (and nfe in the replies). > > I'll just chime in here with some more information - I have a couple other message threads going about some weird high packet volumes on my new FreeBSD 8.0-Release NFS server. I thought it might be an issue with the igb driver so I put in a new card using em instead and got the exact same behavior. I'm currently sifting through a tcpdump in wireshark and there are all sorts of messages in there about checksums being incorrect - both TCP and UDP. This is for communications between this client machine (FreeBSD 7.0-Release) and any of the 8.0 machines I have. The packets going to non-8.0 machines (at least so far) appear to be fine. > > I'll defer to those who know more than I about the networking code, but is there perhaps an issue in general with the checksuming and not specific to one card or driver - is that even possible? That's now 4 different drivers all with various checksum problem reports. > > I'm going to be working on this all day today (and likely over the weekend) so if I can help by supplying information please let me know what you need. > If you are seeing bad checksum reported by tcpdump/wireshark for TX frames on checksum capable controller, it's normal. bpf(4) just sees TX frames before inserting checksum computed by hardware so tcpdump/wireshark reports invalid checksum. You can safely ignore that. If you want to verify whether sending host generated correct checksum, you should capture the frame on receive side. If tcpdump/ wireshark reports bad checksummed frame on received frames it's real bad checksummed frame.
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