From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martijn Lievaart Subject: Re: [NFQUEUE] Help with program that changes DHCP payload Date: Wed, 30 Jan 2008 22:22:37 +0100 Message-ID: <47A0EA9D.2010705@rtij.nl> References: <763049.9097.qm@web58311.mail.re3.yahoo.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <763049.9097.qm@web58311.mail.re3.yahoo.com> Sender: netfilter-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Vincent Arniego Cc: netfilter@vger.kernel.org Vincent Arniego wrote: > > Hi Everyone, > > I'm kinda new here and I would like some help regarding > netfilter_queue. If this is asked already, forgive me I didn't see it in the archives. > > I'm making a program that changes the value of an attribute in the DHCP > payload. > I'm using nfqueue to intercept the packet, change the content of the > payload and resend it again to DHCP > which resides in the same server as the firewall. Why am I doing this? > I'm making a pseudo option 82 using a translated bridge (which the mac > is unchangeable) but I'm using the hostname attribute instead. > Stop right there. The ISC DHCP server does very funky stuff to see packets addressed to 0.0.0.0. This means those packets do not go through netfilter. I bet this is at the root of your problem. I cannot think of a quick way to change this. Maybe hacking at dhcrelay sources is an better option. HTH, M4