From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pablo Neira Ayuso Subject: Re: ctnetlink kernel dump while running multiple libnfct clients Date: Mon, 28 Mar 2011 14:47:13 +0200 Message-ID: <4D908351.5010407@netfilter.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Netfilter Developer Mailing List To: Sam Roberts Return-path: Received: from mail.us.es ([193.147.175.20]:45820 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753098Ab1C1Mqp (ORCPT ); Mon, 28 Mar 2011 08:46:45 -0400 In-Reply-To: Sender: netfilter-devel-owner@vger.kernel.org List-ID: On 25/03/11 01:21, Sam Roberts wrote: > Screenshot attached. > > At the time I had 3 connections to nfnetlink open > - a userspace connection tracker what protocol are you tracking from user-space? > - a utility of mine that prints conntrack and expect events > (https://github.com/sam-github/libnet/blob/master/lua/nfct-events) > - watch -n0.8 -d sudo conntrack -L e > > It was after 5 or so loops of the watch that the kernel BUGged out. > > kernel is 2.6.38-020638-generic (ubuntu's v2.6.28-natty). > > For what it's worth, ctnetlink_exp_dump_expect() seems to assume that > the expectation being printed has a helper with a name that it can > call strlen() on: > > helper = rcu_dereference(help->helper); > if (helper) > NLA_PUT_STRING(skb, CTA_EXPECT_HELP_NAME, helper->name); > } AFAICS, the only way to hit this problem is to have some connection tracking helper in the kernel which overlaps your user-space helper, ie. someone is attaching a kernel helper to your conntrack. > The expectation being printed is one I created from userspace, so I > don't know what helper was found for it, or what it's name would be > (if any). Need more info to know what's going on.