From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McHardy Subject: Re: conntrack, idle TCP connection and keep-alives Date: Sun, 27 Oct 2013 19:34:34 +0000 Message-ID: <20131027193434.GA16816@macbook.localnet> References: <526C22B8.5030102@torlan.ru> <20131027153408.GA20634@home> <20131027180129.GC27597@macbook.localnet> <20131027183825.GA17696@macbook.localnet> <20131027192019.GD32366@macbook.localnet> <526D6825.2090505@torlan.ru> <20131027193243.GA16338@macbook.localnet> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jozsef Kadlecsik , Phil Oester , netfilter-devel@vger.kernel.org To: WGH Return-path: Received: from stinky.trash.net ([213.144.137.162]:65277 "EHLO stinky.trash.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753613Ab3J0Tej (ORCPT ); Sun, 27 Oct 2013 15:34:39 -0400 Content-Disposition: inline In-Reply-To: <20131027193243.GA16338@macbook.localnet> Sender: netfilter-devel-owner@vger.kernel.org List-ID: On Sun, Oct 27, 2013 at 07:32:44PM +0000, Patrick McHardy wrote: > On Sun, Oct 27, 2013 at 11:23:17PM +0400, WGH wrote: > > On 27.10.2013 23:20, Patrick McHardy wrote: > > > On Sun, Oct 27, 2013 at 08:14:19PM +0100, Jozsef Kadlecsik wrote: > > >> I think a single flag could be sufficient: if the timer in conntrack goes > > >> off and the entry is in the ESTABLISHED state and this flag is not set, > > >> then send a TCP keepalive packet and start the timer with a short timeout. > > >> If we receive the reply packet, then the long ESTABLISHED timeout value > > >> can be restored and the flag cleared. > > > Sure, I think we wouldn't even need that flag, we can just send the keepalive > > > and set a short timeout. If a RST is received, the connection is killed > > > anyway, otherwise it will be refreshed with the ESTABLISHED timeout. > > > > > > But we do need a timestamp value to pass PAWS. > > I believe you forgot the third scenario: neither ACK nor RST is received > > in reply. > > Actually no, "... and set a short timeout ...". Well, OK, we do need a flag to distinguish normal timeout from probe timeout. But still I don't see how we can do this without increasing the size of every conntrack by at least 4 bytes.