From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cong Wang Subject: Re: [PATCH net] gre: Fix MTU sizing check for gretap tunnels Date: Fri, 12 Jul 2013 01:11:16 +0000 (UTC) Message-ID: References: <20130711201152.8775.40579.stgit@ahduyck-hc1.jf.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit To: netdev@vger.kernel.org Return-path: Received: from plane.gmane.org ([80.91.229.3]:33220 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932287Ab3GLBLi (ORCPT ); Thu, 11 Jul 2013 21:11:38 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1UxRtV-0001en-I3 for netdev@vger.kernel.org; Fri, 12 Jul 2013 03:11:33 +0200 Received: from 116.53.101.57 ([116.53.101.57]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 12 Jul 2013 03:11:33 +0200 Received: from xiyou.wangcong by 116.53.101.57 with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 12 Jul 2013 03:11:33 +0200 Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 11 Jul 2013 at 20:12 GMT, 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. > This patch indeed fixes the performance problem I reported, nice work! Thanks for the patch, Alexander!