From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McHardy Subject: Re: struct tpacket_auxdata userspace ABI breakage Date: Tue, 22 Jul 2008 18:36:51 +0200 Message-ID: <48860CA3.7030806@trash.net> References: <20080722160844.GK14846@cs181140183.pp.htv.fi> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Cc: "David S. Miller" , netdev@vger.kernel.org To: Adrian Bunk Return-path: Received: from stinky.trash.net ([213.144.137.162]:36050 "EHLO stinky.trash.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750857AbYGVQg5 (ORCPT ); Tue, 22 Jul 2008 12:36:57 -0400 In-Reply-To: <20080722160844.GK14846@cs181140183.pp.htv.fi> Sender: netdev-owner@vger.kernel.org List-ID: Adrian Bunk wrote: > Commit 393e52e33c6c26ec7db290dab803bac1bed962d4 > (packet: deliver VLAN TCI to userspace) adds a > member tp_vlan_tci to struct tpacket_auxdata. > > This changes the size of the struct, and unless I miss something > it is an ABI change that must be reverted. It increases the structure size under the assumption that userspace should be able to handle this since its expected that more things will be added over time. Existing binaries will continue to run just fine in any case, the only potential problem is when compiling against new headers and running on old kernels (structures will appear undersized if userspace doesn't handle this correctly). An alternative would a new cmsg for the VLAN TCI. The only existing user of this (a set of patches I sent for libpcap) handles this correctly though.