Date: Thu, 10 Apr 2008 02:01:16 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Jack Vogel" <jfvogel@gmail.com>, <qpadla@gmail.com> Cc: Vitezslav Novy <vnovy@vnovy.net>, freebsd-current@freebsd.org Subject: Re: IP bad-len 0 ( on em0 ) Message-ID: <002401c89aa6$61387e00$b6db87d4@multiplay.co.uk> References: <200802042142.38606.qpadla@gmail.com><200802070018.54429.qpadla@gmail.com><006801c87f19$a14d8060$b6db87d4@multiplay.co.uk><200804092043.24500.qpadla@gmail.com> <2a41acea0804091659l7ac2d9adqcbdd0caf900469b@mail.gmail.com>
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----- Original Message -----
From: "Jack Vogel" <jfvogel@gmail.com>
> I've looked into this a little, and then got interrupted with other issues. The
> reason the thing is zero'ed is because the hardware is going to repacketize
> this big wad that its been handled, it should be making new headers that
> appear in the packets on the wire. So its not yet clear to me what the
> real brokenness is, you are actually SUPPOSED to zero that value and
> csum according to documentation, but the rewritten headers should have
> correct len's in them, so the question is why in some cases they do not.
>
> I have a test case but it actually involves the advanced code (now in igb).
>
> If someone has a simple reproducible set of steps I would appreciate it.
We saw this with a simple iperf test. I assumed this was due to the same
reason tcpdump sees invalid checksums when hw checksum was enabled but
wanted to confirm.
Regards
Steve
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