From mboxrd@z Thu Jan 1 00:00:00 1970 From: Olaf van der Spek Subject: Re: Enable syn cookies by default Date: Thu, 15 Oct 2009 10:59:03 +0200 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 To: netdev@vger.kernel.org Return-path: Received: from mail-yx0-f187.google.com ([209.85.210.187]:56275 "EHLO mail-yx0-f187.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934957AbZJOI7j (ORCPT ); Thu, 15 Oct 2009 04:59:39 -0400 Received: by yxe17 with SMTP id 17so865944yxe.33 for ; Thu, 15 Oct 2009 01:59:03 -0700 (PDT) In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Sat, Oct 10, 2009 at 3:01 PM, Olaf van der Spek wrote: > Hi, > > I'm forwarding Debian feature request #520668. > > Could syn cookies be enabled by default? > > AFAIK syn cookies only get send when the half-open TCP connection > queue is full. So stuff like window scaling should work fine in normal > situations. > > Speaking of which: > When the half-open TCP connection queue is full and syn cookies are > enabled, you get a message like "kernel: possible SYN flooding on port > 2710. Sending cookies." > However when syn cookies are disabled, you don't get any message (in > kern.log), although connections to your server are timing out. > Could such a message be added? > Maybe with a suggestion to increase the size of that queue or to > enable syn cookies. > > Greetings, > > Olaf > > http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=520668 > http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=520667 > https://bugs.launchpad.net/ubuntu/+bug/57091 > Somebody?