From mboxrd@z Thu Jan 1 00:00:00 1970 From: Philip Craig Subject: Re: NAT packets leaking out with source address Date: Thu, 06 Mar 2008 12:01:34 +1000 Message-ID: <47CF507E.2070203@snapgear.com> References: <20080305165231.505bdd44@speedy> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20080305165231.505bdd44@speedy> Sender: netfilter-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Stephen Hemminger Cc: Patrick McHardy , netfilter@vger.kernel.org Stephen Hemminger wrote: > QA is seeing some (not all packets) going through a NAT router with the > original source address. Is this a known problem? or a configuration issue? > > The packets are ICMP echo requests coming in at almost line rate, so some > table could be getting overloaded? First step is to check the conntrack table for an unnatted and unreplied entry. If the first ICMP was sent before the NAT rule was installed, and you never get a reply (presumably because it is was not NATted), then subsequent ICMP packets will use the same conntrack entry and not be NATted either. These will also refresh the timeout on the conntrack, so it never expires until you stop pinging. If this is the problem, the solution is to make sure you have the NAT rules installed before the filter rules allow the packets.