Date: Fri, 20 Aug 2004 20:20:12 -0700 From: Sean McNeil <sean@mcneil.com> To: Ruslan Ermilov <ru@FreeBSD.org> Cc: gallatin@cs.duke.edu Subject: Re: on amd64 tcp4 cksums are bad (FYI) Message-ID: <1093058412.41311.10.camel@server.mcneil.com>
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Gentlemen, > >> >You're almost certainly using a driver which offloads transmit > >> >checksums. (both fxp and em do) Since BPF sniffs the packet before it > >> >leaves the host, the checksum has not yet been calculated, so it looks > >> >bad. I reported this a long time ago. Hardware transmit checksums are broken somewhere. Most likely UDP and perhaps ipfw/nat have something to do with it. I've just checked and the problem still exists. In order for something like NFS to work, you have to turn off txcsum. Other people see this same issue and it has led me to conclude it isn't nic related. Cheers, Sean
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