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Date: Sun, 17 Dec 2006 15:52:49 -0500
From: Kris Kennaway <kris@obsecurity.org>
To: Andrew Pantyukhin <infofarmer@FreeBSD.org>
Message-ID: <20061217205249.GA73132@xor.obsecurity.org>
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Cc: current@freebsd.org, David Xu <davidxu@freebsd.org>
Subject: Re: vge(4) bad checksum
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On Sun, Dec 17, 2006 at 11:46:24PM +0300, Andrew Pantyukhin wrote:
> I'm not sure what it's all about, but with today's
> current whatever goes out my vge interface (icmp/
> tcp/udp) has bad checksum:

This is a FAQ; it's probably using hardware checksum offloading.

Since the packet passed down to the NIC does not yet have the checksum
computed, it looks to tcpdump like the checksum is incorrect.  However
if you look at the packet actually transmitted by the NIC
(e.g. tcpdump on another host), you'll see that it has the correct
checksum.

Kris

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