netdev - Re: [PATCH][IPv6] Export userland ND options through netlink (RDNSS support)

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Date:	Thu, 02 Dec 2010 22:59:59 +0000
From:	David Woodhouse <dwmw2@...radead.org>
To:	Pierre Ynard <linkfanel@...oo.fr>, yoshfuji@...ux-ipv6.org
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH][IPv6] Export userland ND options through netlink
 (RDNSS support)

On Fri, 2007-10-05 at 08:09 +0200, Pierre Ynard wrote:
> As discussed before, this patch provides userland with a way to access
> relevant options in Router Advertisements, after they are processed and
> validated by the kernel. Extra options are processed in a generic way;
> this patch only exports RDNSS options described in RFC5006, but support
> to control which options are exported could be easily added.
> 
> A new rtnetlink message type is defined, to transport Neighbor Discovery
> options, along with optional context information. At the moment only
> the address of the router sending an RDNSS option is included, but
> additional attributes may be later defined, if needed by new use cases.

RFC5006 §6.1 says:
    Note:  An RDNSS address MUST be used only as long as both the RA
      router lifetime and the RDNSS option lifetime have not expired.
      The reason is that the RDNSS may not be currently reachable or may
      not provide service to the host's current address (e.g., due to
      network ingress filtering [16][17]).

But when this option makes its way to userspace, we don't *know* the RA
router lifetime, or even which interface it came in on. I'm not sure how
we can use this correctly.

This is a start at using it in ConnMan... but unless I'm missing
something, we don't have enough information to do it properly:
http://lists.connman.net/pipermail/connman/2010-December/002781.html

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation

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