From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Greear Subject: Problem with igb and vlans in 2.6.38-rc4 Date: Thu, 10 Feb 2011 09:57:01 -0800 Message-ID: <4D5426ED.7000801@candelatech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: netdev Return-path: Received: from mail.candelatech.com ([208.74.158.172]:33203 "EHLO ns3.lanforge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750991Ab1BJR5C (ORCPT ); Thu, 10 Feb 2011 12:57:02 -0500 Received: from [192.168.100.195] (firewall.candelatech.com [70.89.124.249]) (authenticated bits=0) by ns3.lanforge.com (8.14.2/8.14.2) with ESMTP id p1AHv1VP007267 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Thu, 10 Feb 2011 09:57:01 -0800 Sender: netdev-owner@vger.kernel.org List-ID: We have a user-space app that uses packet-sockets to grab and send Ethernet frames (basically a user-space bridge). This has stopped working for VLANs unless we set the physical port MTU to be vlan-MTU + 4 (ie, 1504 for standard MTU size vlan frames). I think this started post 2.6.34 kernel..but not exactly sure at this time. The test setup is essentially: client -- vlan 5 -- [ eth4 {software-bridge} eth3 ] -- vlan 5 -- server The software bridge machine has no VLANs enabled..it is supposed to just read Ethernet frames from one port and xmit out the other. The bridge machine sees rx-length errors, and if only one port is set to 1504, the other shows xmit errors (since it doesn't like sending a frame 4 bytes larger than MTU probably). This used to work, and I'm hoping this change wasn't done on purpose. Thanks, Ben -- Ben Greear Candela Technologies Inc http://www.candelatech.com