From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rik van Riel Subject: TG3, kvm, ipv6 & tso data corruption bug? Date: Wed, 28 Oct 2009 10:46:55 -0400 Message-ID: <4AE8595F.1080404@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Linux kernel Mailing List , Matt Carlson , Michael Chan , KVM list To: netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:40387 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754197AbZJ1Oqz (ORCPT ); Wed, 28 Oct 2009 10:46:55 -0400 Sender: netdev-owner@vger.kernel.org List-ID: I have been tracking down what I thought was a KVM related network issue for a while, however it appears it could be a hardware issue. The symptom is that data in network packets gets corrupted, before the checksum is calculated. This means the remote host can get corrupted data, with no way to calculate it (except application level checksums). Luckily ssh has such checksums, so my rsync over ssh backup script discovered this issue. On a very regular basis, I got this message from ssh: Corrupted MAC on input. I have played around a bit and narrowed it down to the following: ipv4 => no problem ipv6 w/o tso => no problem ipv6 with tso => occasional data corruption Disabling tso with ethtool -K eth0 tso off makes the problem stop. I am running Fedora 12's 2.6.31.1-56.fc12.x86_64 kernel, with the following hardware: 05:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5761 Gigabit Ethernet PCIe (rev 10) I do not know enough about the network layer to know whether this is fixable in software or whether TSO offloading for ipv6 should just be disabled on this model. -- All rights reversed.