From: Nicolas Dichtel <nicolas.dichtel@6wind•com>
To: Wilco Baan Hofman <wilco@baanhofman•nl>
Cc: netdev <netdev@vger•kernel.org>
Subject: Re: ECMP ipv6 vs ipv4
Date: Mon, 15 Apr 2013 17:51:46 +0200 [thread overview]
Message-ID: <516C2212.4030502@6wind.com> (raw)
In-Reply-To: <1366012728.4975.13.camel@localhost>
Le 15/04/2013 09:58, Wilco Baan Hofman a écrit :
> Hi,
>
> I'm working on a patch to implement 'nexthop weight' for multipath ipv6.
> However, the ECMPv6 implementation has a few flaws that are quite
> annoying.
>
> One of the flaws is that the netlink nexthop API is asymmetrical, you
> can add nexthops through the netlink API, but when the result is
> requested it is completely different, resulting in bird6 removing the
> route as it does not match the initial route set.
In fact, there is two ways to add ECMP routes:
$ ip -6 route add 3ffe:304:124:2306::/64 \
nexthop via fe80::230:1bff:feb4:e05c dev eth0 \
nexthop via fe80::230:1bff:feb4:dd4f dev eth0
or
$ ip -6 route add 3ffe:304:124:2306::/64 via fe80::230:1bff:feb4:dd4f dev
eth0
$ ip -6 route append 3ffe:304:124:2306::/64 via fe80::230:1bff:feb4:e05c dev
eth0
Note that the second way matchs what is returned by the kernel (ie one entry per
nexthop).
>
> Another one of the flaws is that if I add nexthop weight or algorithm
> (weighted hash or weighted random) I need to add this to the main rt
> node, this seems like an inefficient memory structure, as this needs to
> be added to all the siblings as well.
Nexthop weight (rtnh->rtnh_hops) is not implemented.
>
> I propose that we have a nexthop structure to an exclusive route,
> similar what we have for IPv4, where we store the gateway, device and
> weight for all nexthops and the algorithm in the route. This would make
> the netlink API symmetrical again and fixes the n*n inefficiencies when
> adding routes (all siblings need to know about all siblings).
>
> What are your thoughts on this?
>
> Regards,
>
> Wilco Baan Hofman
>
> --
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next prev parent reply other threads:[~2013-04-15 15:51 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-15 7:58 ECMP ipv6 vs ipv4 Wilco Baan Hofman
2013-04-15 15:51 ` Nicolas Dichtel [this message]
2013-04-15 16:53 ` Wilco Baan Hofman
2013-04-17 9:03 ` Nicolas Dichtel
2013-04-17 13:16 ` Wilco Baan Hofman
2013-04-17 14:14 ` Nicolas Dichtel
2013-04-17 15:22 ` Wilco Baan Hofman
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