netdev - Re: jme: UDP checksum error, and lots of them

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Message-Id: <20101201.215916.104055114.davem@davemloft.net>
Date:	Wed, 01 Dec 2010 21:59:16 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	cooldavid@...ldavid.org
Cc:	jengelh@...ozas.de, netdev@...r.kernel.org
Subject: Re: jme: UDP checksum error, and lots of them

From: "Guo-Fu Tseng" <cooldavid@...ldavid.org>
Date: Thu, 2 Dec 2010 12:33:01 +0800

> I suspect that there might be some the HW-Checksum behavior error.
> ex: Replaced the UDP checksum field while it's all zero(no need to checksum)

I checked the VPNC code and it receives UDP encapsulated traffic using
a normal UDP socket.  So any bad checksums should show up in the
statistics and in fact the packets should be dropped by the IPv4
stack before making it to the vpnc application.

Something isn't right here.  The only thing that makes sense is if
the tcpdump checksum validation is wrong for some reason.  Because
only then could we give a reason for the UDP frames to not be
dropped before vpnc can see them.

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