From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: [PATCH net] macvlan: Disable LRO on lowerdev; warn if it's turned back on Date: Tue, 21 Feb 2012 20:28:56 +0000 Message-ID: <1329856136.2689.46.camel@bwh-desktop> References: <1329851622.2689.6.camel@bwh-desktop> <4F43F816.6070908@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: David Miller , , Shradha Shah , Patrick McHardy , "Eric W. Biederman" To: John Fastabend Return-path: Received: from exchange.solarflare.com ([216.237.3.220]:24733 "EHLO ocex02.SolarFlarecom.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1754933Ab2BUU3A (ORCPT ); Tue, 21 Feb 2012 15:29:00 -0500 In-Reply-To: <4F43F816.6070908@intel.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 2012-02-21 at 12:01 -0800, John Fastabend wrote: > On 2/21/2012 11:13 AM, Ben Hutchings wrote: > > Large Receive Offload (LRO) is only appropriate for packets that are > > destined for the host, and should be disabled if received packets may > > be forwarded. > > > > Further, macvtap_skb_to_vnet_hdr() will BUG() on a packet received > > with LRO (but not GRO). > > > > Signed-off-by: Ben Hutchings > > --- > > I'm not really familiar with macvlan so I'm not certain that this should > > be applied to all modes. > > > > Ben. > > > > drivers/net/macvlan.c | 7 +++++++ > > 1 files changed, 7 insertions(+), 0 deletions(-) > > > > But this patch assumes the macvlan is forwarding traffic to a guest > via macvtap. Which is an assumption that may not be true. > > It seems more appropriate for the macvtap driver to do these checks > after all its the driver that may BUG() with LRO. That's what I thought at first, but then I looked through what macvlan was doing and it certainly appears to re-transmit skbs in all modes. That's not valid when gso_size != 0 and gso_type == 0. Ben. -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.