From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesse Gross Subject: Re: [PATCH 2/3] offloading: Support multiple vlan tags in GSO. Date: Mon, 1 Nov 2010 18:31:46 -0700 Message-ID: References: <1288390495-28923-1-git-send-email-jesse@nicira.com> <1288390495-28923-2-git-send-email-jesse@nicira.com> <1288643630.2231.30.camel@achroite.uk.solarflarecom.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: David Miller , netdev@vger.kernel.org To: Ben Hutchings Return-path: Received: from mail-wy0-f174.google.com ([74.125.82.174]:55272 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752783Ab0KBBbr convert rfc822-to-8bit (ORCPT ); Mon, 1 Nov 2010 21:31:47 -0400 Received: by wyf28 with SMTP id 28so6140776wyf.19 for ; Mon, 01 Nov 2010 18:31:46 -0700 (PDT) In-Reply-To: <1288643630.2231.30.camel@achroite.uk.solarflarecom.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, Nov 1, 2010 at 1:33 PM, Ben Hutchings wrote: > On Fri, 2010-10-29 at 15:14 -0700, Jesse Gross wrote: >> We assume that hardware TSO can't support multiple levels of vlan ta= gs >> but we allow it to be done. =A0Therefore, enable GSO to parse these = tags >> so we can fallback to software. >> >> Signed-off-by: Jesse Gross >> CC: Ben Hutchings > [...] > > I can't see how TSO would be enabled on a second-level VLAN device; > presumably you're thinking about GSO being enabled there? Right, TSO can't be enabled on a stacked vlan device. However, there are a few ways that I can think of to hit this code path. One is GSO, another is encapsulating a bridged packet that is already tagged. These are definitely corner cases and I can think of a few other caveats when using them. Mostly I'm just thinking about making it robust in the face of weird corner cases, one piece at a time at least.