From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phil Sutter Subject: Re: linux-next: Tree for Aug 7 Date: Wed, 7 Aug 2013 20:37:58 +0200 Message-ID: <20130807183758.GB16263@orbit.nwl.cc> References: <1375892245.4004.31.camel@edumazet-glaptop> <1375892522.8154.3.camel@jlt4.sipsolutions.net> <1375893609.4004.33.camel@edumazet-glaptop> <20130807.104713.1615549684239408926.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from orbit.nwl.cc ([176.31.251.142]:47829 "EHLO mail.nwl.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753085Ab3HGSi1 (ORCPT ); Wed, 7 Aug 2013 14:38:27 -0400 Content-Disposition: inline In-Reply-To: <20130807.104713.1615549684239408926.davem@davemloft.net> Sender: linux-next-owner@vger.kernel.org List-ID: To: David Miller Cc: eric.dumazet@gmail.com, johannes@sipsolutions.net, sedat.dilek@gmail.com, sfr@canb.auug.org.au, linux-next@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, hannes@stressinduktion.org, linux-wireless@vger.kernel.org, linville@tuxdriver.com On Wed, Aug 07, 2013 at 10:47:13AM -0700, David Miller wrote: > From: Eric Dumazet > Date: Wed, 07 Aug 2013 09:40:09 -0700 > > > On Wed, 2013-08-07 at 18:22 +0200, Johannes Berg wrote: > > > >> Maybe. I haven't tested it, but I'm thinking that skb->data doesn't > >> point to the start of the data frame in this case, since we now call > >> eth_type_trans() which pulls the ethernet header. So if the device just > >> transmits skb->len starting from skb->data, it'll be wrong, no? That > >> seems a basic assumption though. > > > > Yes, it seems calling eth_type_trans() is not right here, and even could > > crash. > > > > Sorry, for being vague, I am a bit busy this morning. > > Yes, this is absolutely the core problem, you absolute cannot > call eth_type_trans() on the output path, it pulls off the > ethernet header from the packet. That can't possibly work. > > I want a real fix submitted formally for this problem immediately, > or else I'm reverting all of these changes this afternoon. One could simply call skb_push(skb, ETH_HLEN) right after calling eth_type_trans(skb, dev) in order to undo the 'data' and 'len' adjustment. Not sure if this kind of hack is the right way to go here, or if the whole af_packet parses ethernet header discussion should be opened again instead. Best wishes, Phil