From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH net] gre: Fix MTU sizing check for gretap tunnels Date: Thu, 11 Jul 2013 15:45:02 -0700 Message-ID: <1373582702.4600.85.camel@edumazet-glaptop> References: <20130711201152.8775.40579.stgit@ahduyck-hc1.jf.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Alexander Duyck , netdev@vger.kernel.org, jesse@nicira.com, davem@davemloft.net To: Pravin Shelar Return-path: Received: from mail-ob0-f176.google.com ([209.85.214.176]:56883 "EHLO mail-ob0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756466Ab3GKWpF (ORCPT ); Thu, 11 Jul 2013 18:45:05 -0400 Received: by mail-ob0-f176.google.com with SMTP id v19so10430308obq.7 for ; Thu, 11 Jul 2013 15:45:05 -0700 (PDT) In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 2013-07-11 at 15:24 -0700, Pravin Shelar wrote: > On Thu, Jul 11, 2013 at 1:12 PM, Alexander Duyck > wrote: > > This change fixes an MTU sizing issue seen with gretap tunnels when non-gso > > packets are sent from the interface. > > > > In my case I was able to reproduce the issue by simply sending a ping of > > 1421 bytes with the gretap interface created on a device with a standard > > 1500 mtu. > > > > This fix is based on the fact that the tunnel mtu is already adjusted by > > dev->hard_header_len so it would make sense that any packets being compared > > against that mtu should also be adjusted by hard_header_len and the tunnel > > header instead of just the tunnel header. > > > we can simplify code by not doing dev->hard_header_len adjustment to tunnel-mtu. > > And right thing would be adjusting tunnel-mtu according to rt->dst.dev > header-len so that we get mtu for out going path. What's the mtu value we want to put in the ICMP message ?