From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McHardy Subject: Re: [PATCH for 2.6.33] conntrack: restrict runtime hashsize modifications Date: Thu, 04 Feb 2010 17:27:54 +0100 Message-ID: <4B6AF58A.202@trash.net> References: <20100203203929.GA6168@x200> <4B6AF36A.3050402@trash.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Cc: davem@davemloft.net, jonathan@jonmasters.org, eric.dumazet@gmail.com, netdev@vger.kernel.org, netfilter-devel@vger.kernel.org To: Alexey Dobriyan Return-path: Received: from stinky.trash.net ([213.144.137.162]:48624 "EHLO stinky.trash.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752668Ab0BDQ2B (ORCPT ); Thu, 4 Feb 2010 11:28:01 -0500 In-Reply-To: <4B6AF36A.3050402@trash.net> Sender: netfilter-devel-owner@vger.kernel.org List-ID: Patrick McHardy wrote: > Alexey Dobriyan wrote: >> Jon Masters correctly points out that conntrack hash sizes >> (nf_conntrack_htable_size) are global (not per-netns) and >> modifiable at runtime via /sys/module/nf_conntrack/hashsize . >> >> Steps to reproduce: >> clone(CLONE_NEWNET) >> [grow /sys/module/nf_conntrack/hashsize] >> exit() >> >> At netns exit we are going to scan random memory for conntracks to be killed. >> >> Apparently there is a code which deals with hashtable resize for >> init_net (and it was there befode netns conntrack code), so prohibit >> hashsize modification if there is more than one netns exists. >> >> To change hashtable sizes, you need to reload module. >> >> Expectation hashtable size was simply glued to a variable with no code >> to rehash expectations, so it was a bug to allow writing to it. >> Make "expect_hashsize" readonly. >> >> This is temporarily until we figure out what to do. > > How about alternatively moving nf_conntrack_hsize into the > per-namespace struct? It doesn't look more complicated or > intrusive and would allow to still change the init_net > hashsize. Also seems less hackish :) Just to avoid duplicate work, I'm currently trying that.