From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: Doubts about listen backlog and tcp_max_syn_backlog Date: Wed, 23 Jan 2013 11:28:08 -0800 Message-ID: <510039C8.7040401@hp.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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Leandro Lucarella Return-path: Received: from g1t0027.austin.hp.com ([15.216.28.34]:28800 "EHLO g1t0027.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751764Ab3AWT2K (ORCPT ); Wed, 23 Jan 2013 14:28:10 -0500 In-Reply-To: <20130123104736.GK4608@sociomantic.com> Sender: netdev-owner@vger.kernel.org List-ID: On 01/23/2013 02:47 AM, Leandro Lucarella wrote: > Thanks for the info. I'm definitely dropping SYNs and sending cookies, > around 50/s. Is there any way to tell how many connections are queued in > a particular socket? I am not familiar with one. Doesn't mean there isn't one, only that I am not able to think of it. > 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. 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. That would be 3 (,9, 21, etc...) seconds on a kernel with 3 seconds as the initial retransmission timeout. rick