From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pascal Hambourg Subject: Re: [SOLVED] Re: IPv6 forwarding to TAP-interface fails Date: Wed, 23 Dec 2009 14:03:41 +0100 Message-ID: <4B32152D.60003@plouf.fr.eu.org> References: <20091219162047.04be7ac3@coercion> <4B2CDE84.3060703@plouf.fr.eu.org> <20091221114648.08eede72@malediction> <20091221140952.63c607f5@malediction> Mime-Version: 1.0 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20091221140952.63c607f5@malediction> Sender: netfilter-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="iso-8859-1" To: Mike Kazantsev Cc: netfilter@vger.kernel.org Mike Kazantsev a =E9crit : >=20 > And here's the problem: no link-local address on the interface. Good catch. I didn't notice it. > With this address added (or rather preserved), router is able to send > neighbor solicitation requests from it and everything works fine. >=20 > Anyway, strange thing is that, apparently, VM on the other side is ab= le > to send these requests without link-local address, using global one > instead: [...] > Guess older kernel (2.6.30.4) there is the cause of it, and that's al= so > why it worked before with pretty much the same setup. I observed that when sending a locally generated packet, Linux uses the source address (which is one one of its own addresses) of the packet as the source address in the neighbour solicitation, whereas when forwarding a packet it uses the link-local address attached to the output interface. So there may be trouble when forwarding a packet and the output interface has no link-local address. The tcpdump trace in your previous message shows a neighbour solicitation packet with unspecified source address : > IP6 :: > ff02::1:ff00:22: ICMP6, neighbor solicitation, who has 2001:= 470:1f0b:11de::22, length 24 This may explain the different results with pings from the LAN and from the router, and also why VM does not have the problem even though it ha= s no link-local address.