From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: [PATCH 2/2] net: ip, ipv6: handle gso skbs in forwarding path Date: Wed, 29 Jan 2014 12:04:01 +0100 Message-ID: <20140129110401.GA25336@order.stressinduktion.org> References: <1390810971-23959-1-git-send-email-fw@strlen.de> <1390810971-23959-2-git-send-email-fw@strlen.de> <1390846967.27806.75.camel@edumazet-glaptop2.roam.corp.google.com> <20140128002707.GA12308@order.stressinduktion.org> <20140129105347.GF30123@breakpoint.cc> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: Eric Dumazet , netdev@vger.kernel.org To: Florian Westphal Return-path: Received: from order.stressinduktion.org ([87.106.68.36]:44114 "EHLO order.stressinduktion.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750942AbaA2LED (ORCPT ); Wed, 29 Jan 2014 06:04:03 -0500 Content-Disposition: inline In-Reply-To: <20140129105347.GF30123@breakpoint.cc> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Jan 29, 2014 at 11:53:47AM +0100, Florian Westphal wrote: > Hannes Frederic Sowa wrote: > > > TCP stream not using DF flag are very unlikely to care if we adjust > > > their MTU (lowering gso_size) at this point ? > > > > UDP shouldn't be a problem, too. > > Sorry for late reply, but how can this be safe for UDP? > We should make sure that peer sees original, unchanged datagram? Peer as in original destination? Of course, we must not alter the datagram but can only do fragmentation or send back frag_needed. > And only solution for UDP that I can see is to do sw segmentation (i.e. > create ip fragments). Hardware(-UFO) would do fragmentation in hardware, too, because there is no other way to split UDP data in any other way. If UFO is not supported manual sw segmentation would create the required fragments in output path, too. Greetings, Hannes