From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [PATCH 3/5] netfilter: add SYNPROXY core/target Date: Thu, 8 Aug 2013 10:04:48 +0200 Message-ID: <20130808100448.010cd96d@redhat.com> References: <1375897371-18430-1-git-send-email-kaber@trash.net> <1375897371-18430-4-git-send-email-kaber@trash.net> <20130807222600.51eeca09@redhat.com> <20130807205602.GA21463@macbook.localnet> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: pablo@netfilter.org, netfilter-devel@vger.kernel.org, netdev@vger.kernel.org, mph@one.com, as@one.com To: Patrick McHardy Return-path: In-Reply-To: <20130807205602.GA21463@macbook.localnet> Sender: netfilter-devel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed, 7 Aug 2013 22:56:03 +0200 Patrick McHardy wrote: > On Wed, Aug 07, 2013 at 10:26:00PM +0200, Jesper Dangaard Brouer wrote: > > On Wed, 7 Aug 2013 19:42:49 +0200 Patrick McHardy wrote: [...] > > Besides shouldn't nth->ack_seq be zero, in a SYN packet? This is the > > SYN "replayed" towards the server right? > > > > I also pointed to this in an earlier patch Martin showed me, but he > > reported that changing this resulted in bad behavior. So, I would > > request Martin to re-test this part. > > Right, it should be zero, but it doesn't matter since the ACK flag isn't > set. This is used to propagate the sequence number to the hook function > to initialize the sequence adjustment data. While in the target function, > we don't have any connection tracking state to store this in. We could > set it to zero after that, but it shouldn't matter. I think it deserves a comment in the code, that you are using ack_seq, to relay this information to the hook, as its not obvious. And I think we should set it to zero after that, else it will be visible on the wire, and wireshark complains (with a warning) when it sees pure SYN packets with a non-zero ACK number (Martin send me a dump some time ago, and I just checked). p.s. thanks for working on this module, which we discussed during the Netfilter Workshop 2013. -- Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer