From mboxrd@z Thu Jan 1 00:00:00 1970 From: Leandro Lucarella Subject: Re: Doubts about listen backlog and tcp_max_syn_backlog Date: Thu, 24 Jan 2013 13:22:23 +0100 Message-ID: <20130124122223.GQ4608@sociomantic.com> References: <20130122161038.GG4608@sociomantic.com> <1358873142.3464.3964.camel@edumazet-glaptop> <20130122165929.GH4608@sociomantic.com> <1358874800.3464.4002.camel@edumazet-glaptop> <50FED7CE.1030008@hp.com> <20130122184245.GJ4608@sociomantic.com> <50FF0C25.9000300@hp.com> <20130123104736.GK4608@sociomantic.com> <510039C8.7040401@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Eric Dumazet , netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Rick Jones Return-path: Received: from moutng.kundenserver.de ([212.227.126.186]:56365 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752979Ab3AXMWb (ORCPT ); Thu, 24 Jan 2013 07:22:31 -0500 Content-Disposition: inline In-Reply-To: <510039C8.7040401@hp.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Jan 23, 2013 at 11:28:08AM -0800, Rick Jones wrote: > >Then if syncookies are enabled, the time spent in connect() shouldn't be > >bigger than 3 seconds even if SYNs are being "dropped" by listen, right? > > Do you mean if "ESTABLISHED" connections are dropped because the > listen queue is full? I don't think I would put that as "SYNs being > dropped by listen" - too easy to confuse that with an actual > dropping of a SYN segment. I was just kind of quoting the name given by netstat: "SYNs to LISTEN sockets dropped" (for kernel 3.0, I noticed newer kernels don't have this stat anymore, or the name was changed). I still don't know if we are talking about the same thing. > But yes, I would not expect a connect() call to remain incomplete > for any longer than it took to receive an SYN|ACK from the other > end. So the only reason to experience these high times spent in connect() should be because a SYN or SYN|ACK was actually loss in a lower layer, like an error in the network device or a transmission error? > That would be 3 (,9, 21, etc...) seconds on a kernel with 3 > seconds as the initial retransmission timeout. Which can't be changed without recompiling, right? Thanks! -- Leandro Lucarella sociomantic labs GmbH http://www.sociomantic.com