Re: draft-gont-6man-slaac-renum-01

神明達哉 <jinmei@wide.ad.jp> Mon, 25 March 2019 20:23 UTC

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From: 神明達哉 <jinmei@wide.ad.jp>
Date: Mon, 25 Mar 2019 13:23:06 -0700
Message-ID: <CAJE_bqeuA+APL=Rs-J_8oAKQMzownjPCSQcO5v+LDNeoqzCkjQ@mail.gmail.com>
Subject: Re: draft-gont-6man-slaac-renum-01
To: Fernando Gont <fgont@si6networks.com>
Cc: ek@loon.co, IETF IPv6 Mailing List <ipv6@ietf.org>
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At Mon, 25 Mar 2019 09:50:14 +0100,
Fernando Gont <fgont@si6networks.com> wrote:

> > This would basically be a host sending a packet from itself to itself
> > via the router.  The destination address should be a GUA from the PIO
> > formed on the interface, but the contents and source address I'm less
> > sure of (could be from link-local or the same GUA or a different
> > on-link GUA, could be a ping or a unicast NS or a UDP packet to a port
> > the host opens, ...).
>
> I'm not sure if a packet with a link-local address that would be bounced
> back on the same link would be considered "source address out of scope"
> by the router or not

It shouldn't be considered "source address out of scope", at least
protocol-wise.  See section 9 of RFC4007.  It doesn't explicitly show
an example of source=link-local and destination=global, but the
description of when the "beyond scope of source address" error applies
should be clear enough to understand this case shouldn't result in
that condition.  Most if not all BSD-variant OSes should fully conform
to this concept of RFC4007 and should forward the packet back to the
original link as expected.

I wouldn't be surprised, however, if there's a buggy implementation
that precludes any kind of forwarding simply when the source (or
destination for that matter) address is link-local.  I'd be
particularly curious if any Linux kernel version has this kind of bug,
since some widely deployed CPE routers may be developed on some flavor
of Linux.

--
JINMEI, Tatuya