From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McHardy Subject: Re: problem with connection tracking with fragmentation needed icmp error Date: Fri, 03 Nov 2006 11:19:52 +0100 Message-ID: <454B17C8.1010904@trash.net> References: <013a01c6fe4b$c5032dc0$4c01a8c0@elitecore26> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Cc: netfilter-devel@lists.netfilter.org Return-path: To: Nishit Shah In-Reply-To: <013a01c6fe4b$c5032dc0$4c01a8c0@elitecore26> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: netfilter-devel-bounces@lists.netfilter.org Errors-To: netfilter-devel-bounces@lists.netfilter.org List-Id: netfilter-devel.vger.kernel.org Nishit Shah wrote: > Hi, > > I have a following setup > > machineA ------------------------------router -------------------------- > firewall ------------------------------------ machineB > 172.16.16.2 172.16.16.1 9.9.9.1 9.9.9.2 > 192.168.1.1 192.168.1.2 > > > router has two interfaces, eth0 is connected to machineA with mtu of 1000, > all other interfaces with mtu of 1500. > if i ping from machineA to machineB with data size 1200 and DF bit set, > packet will reach machineB, machineB will reply with DF bit set and data > size 1200, > upon receving this packet router sends icmp fragmentation needed and DF bit > set message to machineB, when this packet comes to firewall conntrack marks > that packet's state as INVALID. is it the valid case ?? I don't see how this can happen on current kernels that manually associate locally generated ICMP errors with the original conntrack. What kernel version are you running on the router?