From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Emelyanov Subject: Re: [PATCH] devinet: sysctl setup off by one Date: Mon, 26 May 2008 11:39:21 +0400 Message-ID: <483A6929.6060905@openvz.org> References: <20080523153559.156a1fb5@speedy> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "David S. Miller" , netdev@vger.kernel.org To: Stephen Hemminger Return-path: Received: from sacred.ru ([62.205.161.221]:58574 "EHLO sacred.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751884AbYEZHlv (ORCPT ); Mon, 26 May 2008 03:41:51 -0400 In-Reply-To: <20080523153559.156a1fb5@speedy> Sender: netdev-owner@vger.kernel.org List-ID: Stephen Hemminger wrote: > It look like the code to setup /proc/sys/net/ipv4/conf/XXX has an off by one bug > that causes the last entry (arp_accept) not to be adjusted properly. This causes > changes to the value to occur in the default namespace not the clone? Don't use > network namespaces myself, but this looks like a bug. > > Signed-off-by: Stephen Hemminger > > --- a/net/ipv4/devinet.c 2008-05-23 15:23:19.000000000 -0700 > +++ b/net/ipv4/devinet.c 2008-05-23 15:29:17.000000000 -0700 > @@ -1466,7 +1466,7 @@ static int __devinet_sysctl_register(str > if (!t) > goto out; > > - for (i = 0; i < ARRAY_SIZE(t->devinet_vars) - 1; i++) { > + for (i = 0; i < ARRAY_SIZE(t->devinet_vars); i++) { > t->devinet_vars[i].data += (char *)p - (char *)&ipv4_devconf; > t->devinet_vars[i].extra1 = p; > t->devinet_vars[i].extra2 = net; > This off-by-one is required, since the very last element of this array is used as a sentinel, that shows sysctl engine when to stop processing the table. Look, the sizeof(t->devinet_vars) is __NET_IPV4_CONF_MAX == 22, thus entries 0, 1, ... 20 are tables and the 21-st is this sentinel, so the initialization of this last entry, whose index is (this_sizeof() - 1), is not required. Thanks, Pavel