From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [Bugme-new] [Bug 14427] New: ipv6 forward cause strange route Date: Mon, 2 Nov 2009 22:32:37 -0800 Message-ID: <20091102223237.c0102f19.akpm@linux-foundation.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: bugzilla-daemon@bugzilla.kernel.org, bugme-daemon@bugzilla.kernel.org, green@msu.ru To: netdev@vger.kernel.org Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:40902 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751396AbZKCGdQ (ORCPT ); Tue, 3 Nov 2009 01:33:16 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: (switched to email. Please respond via emailed reply-to-all, not via the bugzilla web interface). On Sat, 17 Oct 2009 10:42:01 GMT bugzilla-daemon@bugzilla.kernel.org wrote: > http://bugzilla.kernel.org/show_bug.cgi?id=14427 > > Summary: ipv6 forward cause strange route > Product: Networking > Version: 2.5 > Platform: All > OS/Version: Linux > Tree: Mainline > Status: NEW > Severity: normal > Priority: P1 > Component: IPV6 > AssignedTo: yoshfuji@linux-ipv6.org > ReportedBy: green@msu.ru > Regression: No > > > When enabling forwarding for IPv6 on interface, in the routing table local > appears new route. It like route to local ip but with all host bits set to 0. > Example: > -------------------------------------------------- > # cat /proc/sys/net/ipv6/conf/eth0/forwarding > 0 > # ip -6 addr add 2001:db8:1:1::5/64 dev eth0 > # ip -6 route show table local > ... > local 2001:db8:1:1::5 via :: dev lo proto none metric 0 mtu 16436 advmss > 16376 hoplimit 4294967295 > ... > # echo 1 > /proc/sys/net/ipv6/conf/eth0/forwarding > # ip -6 route show table local > ... > local 2001:db8:1:1:: via :: dev lo proto none metric 0 mtu 16436 advmss > 16376 hoplimit 4294967295 > local 2001:db8:1:1::5 via :: dev lo proto none metric 0 mtu 16436 advmss > 16376 hoplimit 4294967295 > ... > -------------------------------------------------- > After enabling forwarding, route "2001:db8:1:1:: via :: dev lo" is added. No > matter, forwarding is enabled before or after adding of address, this route is > "on" with forwarding and "off" without it. > Such behavior causes problems with /127 network masks. For example: > -------------------------------------------------- > # echo 1 > /proc/sys/net/ipv6/conf/eth0/forwarding > # ip -6 addr add 2001:db8:1:1::5/127 dev eth0 > # ip -6 route add default via 2001:db8:1:1::4 > RTNETLINK answers: Invalid argument > -------------------------------------------------- > But if we disable forwarding (and strange route) when adding needed route, we > will succeed. > -------------------------------------------------- > # echo 0 > /proc/sys/net/ipv6/conf/eth0/forwarding > # ip -6 route add default via 2001:db8:1:1::4 > # echo 1 > /proc/sys/net/ipv6/conf/eth0/forwarding > -------------------------------------------------- > Default route remains in the table after enabling forwarding and it is doing in > work. But in this case we still can not access 2001:db8:1:1::4, because it is > routed to loopback: > -------------------------------------------------- > # ping6 -c 1 2001:db8:1:1::4 > PING 2001:db8:1:1::4(2001:db8:1:1::4) 56 data bytes > 64 bytes from 2001:db8:1:1::5: icmp_seq=1 ttl=64 time=0.114 ms > -------------------------------------------------- > We get reply from self interface. > > This was tested on x86 and x86_64 with 2.6.30 kernel and some previous versions > on ArchLinux (2.6.30 x86 and x86_64), Ubuntu (2.6.28-15-generic x86_64) and > gentoo (2.6.30-gentoo-r5 x86_64). >