From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McHardy Subject: Re: DDoS attack causing bad effect on conntrack searches Date: Fri, 23 Apr 2010 13:06:45 +0200 Message-ID: <4BD17F45.3030802@trash.net> References: <1271941082.14501.189.camel@jdb-workstation> <4BD04C74.9020402@trash.net> <1271946961.7895.5665.camel@edumazet-laptop> <1271948029.7895.5707.camel@edumazet-laptop> <20100422155123.GA2524@linux.vnet.ibm.com> <1271952128.7895.5851.camel@edumazet-laptop> <1271970199.7895.6482.camel@edumazet-laptop> <4BD17CAA.4090708@trash.net> <1272020717.7895.7974.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Jesper Dangaard Brouer , paulmck@linux.vnet.ibm.com, Changli Gao , hawk@comx.dk, Linux Kernel Network Hackers , Netfilter Developers To: Eric Dumazet Return-path: Received: from stinky.trash.net ([213.144.137.162]:55681 "EHLO stinky.trash.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756315Ab0DWLGu (ORCPT ); Fri, 23 Apr 2010 07:06:50 -0400 In-Reply-To: <1272020717.7895.7974.camel@edumazet-laptop> Sender: netfilter-devel-owner@vger.kernel.org List-ID: Eric Dumazet wrote: > Le vendredi 23 avril 2010 =E0 12:55 +0200, Patrick McHardy a =E9crit = : >> Eric Dumazet wrote: >>> OK but a lookup last a fraction of a micro second, unless interrupt= ed by >>> hard irq. >>> >>> Probability of a change during a lookup should be very very small. >>> >>> Note that the scenario for a restart is : >>> >>> The lookup go through the chain. >>> While it is examining one object, this object is deleted. >>> The object is re-allocated by another cpu and inserted to a new cha= in. >> I think another scenario that seems a bit more likely would be >> that a new entry is added to the chain after it was fully searched. >> Perhaps we could continue searching at the last position if the >> last entry is not a nulls entry to improve this. >=20 > But the last entry is always a nulls entry, what do you mean exactly = ? >=20 > When an unsert (of a fresh object, not a reused one) is done, this > doesnt affect lookups in any way, since its done at the head of list. Right, I missed that :) -- To unsubscribe from this list: send the line "unsubscribe netfilter-dev= el" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html