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

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Message-Id: <3DEFF398-F151-487E-A2F8-5AB593E4A21B@massar.ch>
Date:   Thu, 18 Nov 2021 11:49:29 +0100
From:   Jeroen Massar <jeroen@...sar.ch>
To:     Juhamatti Kuusisaari <juhamatk@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: IPv6 Router Advertisement Router Preference (RFC 4191) behavior
 issue



> On 20211118, at 11:35, Juhamatti Kuusisaari <juhamatk@...il.com> 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.

Do watch out that there are a couple of user space tools (yes, that thing) that think that they have to handle RAs.... and thus one might get conflicts about reasoning between the kernel doing it or that user space daemon thing.

Greets,
 Jeroen