netdev - Re: IPv6 Router Advertisement Router Preference (RFC 4191) behavior issue

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Message-ID: <CACS3ZpBdTWXoQVhNFks4VqEUxCC8WmurjnD8WUH7LVedxHjSGA@mail.gmail.com>
Date:   Wed, 1 Dec 2021 08:31:34 +0200
From:   Juhamatti Kuusisaari <juhamatk@...il.com>
To:     David Ahern <dsahern@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: IPv6 Router Advertisement Router Preference (RFC 4191) behavior issue

Hello,

On Mon, 29 Nov 2021 at 01:11, David Ahern <dsahern@...il.com> wrote:
>
> On 11/18/21 3:35 AM, Juhamatti Kuusisaari wrote:
> > Hello,
> >
> > I have been testing IPv6 Router Advertisement Default Router
> > Preference on 5.1X and it seems it is not honoured by the Linux
> > networking stack. Whenever a new default router preference with a
> > higher or lower preference value is received, a new default gateway is
> > added as an ECMP route in the routing table with equal weight. This is
> > a bit surprising as RFC 4191 Sec. 3.2 mentions that the higher
> > preference value should be preferred. This part seems to be missing
> > from the Linux implementation.
> >
> > The problem has existed apparently for a while, see below discussion
> > for reference:
> > https://serverfault.com/questions/768932/can-linux-be-made-to-honour-ipv6-route-advertisement-preferences
> >
> > I am happy to test any improvements to this, in case someone takes a look.
> >
>
> do you have CONFIG_IPV6_ROUTER_PREF enabled and accept_ra_rtr_pref set
> for the device?

Yes, I have these set.

BR,
--
 Juhamatti