From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lance Richardson Subject: Re: [PATCH net v3] ipv4: allow local fragmentation in ip_finish_output_gso() Date: Fri, 4 Nov 2016 09:49:13 -0400 (EDT) Message-ID: <1461381070.97911800.1478267353507.JavaMail.zimbra@redhat.com> References: <1478118977-19608-1-git-send-email-lrichard@redhat.com> <20161103222751.5ae120ed@halley> <1769078966.96766888.1478207154311.JavaMail.zimbra@redhat.com> <20161104114014.3dbb8684@halley> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: Hannes Frederic Sowa , fw@strlen.de, netdev@vger.kernel.org, jtluka@redhat.com To: Shmulik Ladkani Return-path: Received: from mx6-phx2.redhat.com ([209.132.183.39]:53187 "EHLO mx6-phx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933535AbcKDNt1 (ORCPT ); Fri, 4 Nov 2016 09:49:27 -0400 In-Reply-To: <20161104114014.3dbb8684@halley> Sender: netdev-owner@vger.kernel.org List-ID: > From: "Shmulik Ladkani" > To: "Hannes Frederic Sowa" > Cc: "Lance Richardson" , fw@strlen.de, netdev@vger.kernel.org, jtluka@redhat.com > Sent: Friday, November 4, 2016 5:40:14 AM > Subject: Re: [PATCH net v3] ipv4: allow local fragmentation in ip_finish_output_gso() > > On Thu, 3 Nov 2016 22:34:34 +0100 Hannes Frederic Sowa > wrote: > > Correct, but we should maybe redefine the code a bit. From my > > understanding we can now create an ICMP storm in case every fragment gets. > > Yes, you are right. > > Each segment gets into ip_fragment, and due to outer DF being set, > ICMP_FRAG_NEEDED is sent per segment. > > BTW, suppose GRO is off, and sender actually did send a burst of > (non-gso) packets with outer DF set, and each was tunnel encapsulated, > resulting in oversized frames. > > Would'nt the stack just send the ICMP_FRAG_NEEDED per encapsulated > frame? > > If so, then the GRO behaviour is aligned, and there's nothing to fix. > Agree. > Best, > Shmulik >