netdev - Selective MD5 Checksum Failuers

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Message-ID: <EB1DC92D4496BF4699C950937A61F17805833E@mx1.guavus.com>
Date:	Wed, 21 Apr 2010 11:42:54 +0000
From:	Bijay Singh <Bijay.Singh@...vus.com>
To:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:	"chrisw@...hat.com" <chrisw@...hat.com>,
	"davem@...emloft.net" <davem@...emloft.net>
Subject: Selective MD5 Checksum Failuers

I am noticing a strange and a troublesome behavior with tcp md5 checksums. Some selective packets are going out with invalid md5 checksums.

The only thing that is changing is the ack number (between the packets with valid and invalid md5 checksums), so while most packets have correct md5 checksums few 1 in 1000s have md5 checksums errors.

I am on 2.6.26 and I know that there have been significant changes since this version in this area. I have gone thru them but none of issues they address seem like the cause for this problem.

I have the scatter/gather and tcp segmentation disabled in the card.

The packet captures are attached.

Bijay

Download attachment "md5sum-2010-04-16.pcap1-754478487" of type "application/octet-stream" (126 bytes)

Download attachment "md5sum-2010-04-16.pcap1-754479689" of type "application/octet-stream" (126 bytes)