On Fri, Aug 20, 2004 at 03:41:26PM -0400, Andrew Gallatin wrote: > > David W. Hankins writes: > > > > This is as observed via tcpdump on [client], which is what is producing > > the bad checksums. Obviously it doesn't cause a problem since no one > > listens to TCP checksums, but it's interesting. I only noticed it > > because I was tcpdump'ing for completely unrelated reasons, and it caught > > my eye. > > <...> > > > Client machine is amd64, running 64-bit mode 5-current fresh as of > > yesterday. Network interface is e1000, so fxp. Server is also freebsd > > e1000 is actually em. > > 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. > > See this thread: > http://lists.FreeBSD.org/pipermail/freebsd-net/2004-August/004703.html > This should be added to FAQ. Cheers, -- Ruslan Ermilov ru_at_FreeBSD.org FreeBSD committer
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