From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next] gro: relax ID check in inet_gro_receive() Date: Thu, 21 Mar 2013 12:31:22 -0400 (EDT) Message-ID: <20130321.123122.1792402145612438586.davem@davemloft.net> References: <1363841553.3333.47.camel@edumazet-glaptop> <20130321.114616.279859400813363663.davem@davemloft.net> <1363882825.2736.4.camel@bwh-desktop.uk.solarflarecom.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org, dmitry@broadcom.com, eilong@broadcom.com, pshelar@nicira.com, hkchu@google.com, maze@google.com To: bhutchings@solarflare.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:44062 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754414Ab3CUQbY (ORCPT ); Thu, 21 Mar 2013 12:31:24 -0400 In-Reply-To: <1363882825.2736.4.camel@bwh-desktop.uk.solarflarecom.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Ben Hutchings Date: Thu, 21 Mar 2013 16:20:25 +0000 > On Thu, 2013-03-21 at 11:46 -0400, David Miller wrote: >> From: Eric Dumazet >> Date: Wed, 20 Mar 2013 21:52:33 -0700 >> >> > GRE TSO support doesn't increment the ID in the inner IP header. >> >> Is this a fundamental limitation of doing TSO over GRO or >> were the Broadcom folks just being lazy with their firmware >> implementation? >> >> I really don't want to apply this patch, because ipv4 frames >> even with DF set should have an incrementing ID field, in >> order to accomodate various header compression schemes. >> >> We go out of our way to do this for normal unencapsulated TCP stream >> packets, rather than set the ID field to zero (which we did for some >> time until the compression issue was pointed out to us). > > Besides which, GRO has been reliably reversible until now. (gso_size is > available through packet sockets, even if tcpdump doesn't appear to use > it yet.) Ignoring IPv4 IDs will break that guarantee. Right, even ignoring the header compression issues, our segmentation offloads must be perfectly reversible.