Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754902AbWL1SNP (ORCPT ); Thu, 28 Dec 2006 13:13:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754909AbWL1SNP (ORCPT ); Thu, 28 Dec 2006 13:13:15 -0500 Received: from mail.us.es ([193.147.175.20]:45764 "EHLO us.es" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754902AbWL1SNO (ORCPT ); Thu, 28 Dec 2006 13:13:14 -0500 X-Greylist: delayed 397 seconds by postgrey-1.27 at vger.kernel.org; Thu, 28 Dec 2006 13:13:14 EST Message-ID: <459409AE.9070402@netfilter.org> Date: Thu, 28 Dec 2006 19:15:10 +0100 From: Pablo Neira Ayuso User-Agent: Thunderbird 1.5.0.5 (X11/20060812) MIME-Version: 1.0 To: Jan Engelhardt CC: Netfilter Developer Mailing List , Linux Kernel Mailing List , kaber@trash.net Subject: Re: skb->h not initialized References: In-Reply-To: X-Enigmail-Version: 0.94.0.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1289 Lines: 28 Jan Engelhardt wrote: > while writing a netfilter match module I found that, when run, > skb->h.th is not set to the TCP header (it is assured that the packet > _is_ TCP), as this printk shows me: > > skb: h.th=cb5bc4dc nh.iph=cb5bc4dc mac.raw=cb5bc4ce head=cb5bc400 > data=cb5bc4dc tail=cb5bc510 end=cb5bc580 > > Is it intended that skb->h.th is not set to skb->data + length of ip > header (skb->data+protoff as far as netfilter matches are concerned)? The netfilter hooks are placed in the network layer, therefore skb->h.th is not set in the input path since the packet did not reach the transport layer yet (prerouting/input), but it is set in the output path because it already passed by the transport layer (output/postrouting). BTW, I'm unsure that this can be of interest in the linux-kernel list, please there's no need to cc everyone. Use netfilter or linux-net instead next time. -- The dawn of the fourth age of Linux firewalling is coming; a time of great struggle and heroic deeds -- J.Kadlecsik got inspired by J.Morris - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/