From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Du, Fan" Subject: Re: GSO packets on lower MTU retaining gso_size? Date: Tue, 07 Jun 2016 14:46:06 +0800 Message-ID: <57566DAE.4010609@intel.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev To: Yuval Mintz Return-path: Received: from mga04.intel.com ([192.55.52.120]:54194 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753457AbcFGGqO (ORCPT ); Tue, 7 Jun 2016 02:46:14 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On 2016/6/7 14:05, Yuval Mintz wrote: > While experimenting with Vxlan tunnels, I've reached a topology where the > Vxlan interface's MTU was 1500 while base-interface was smaller [600]. > > While 'regular' packets broke via ip-fragmentation, GSO SKBs passing from > the vxlan interface to the base interface remained whole, and their > `gso_size' remained matching to that of the vxlan-interface's MTU; > This caused the HW to drop said packets, as it would have resulted with > the device sending to the line packets with length larger than the mtu. > > Is this broken on the udp-tunnel transmit path, the setup or the driver [qede]? I believe it's identical to issue I met before[1], the owner of the offending code believe a host can't generate packet size larger than the underlying NIC MTU and refuse to do the GSO here. [1]: https://patchwork.ozlabs.org/patch/415791/