linux-kernel - Re: [PATCH] net/ipv6: allow device-only routes via the multipath API

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Message-ID: <7a4ebf5d-1815-44b6-bf77-bc7b32f39984@kernel.org>
Date: Sun, 16 Nov 2025 18:57:28 -0700
From: David Ahern <dsahern@...nel.org>
To: azey <me@...y.net>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Nicolas Dichtel <nicolas.dichtel@...nd.com>
Subject: Re: [PATCH] net/ipv6: allow device-only routes via the multipath API

On 11/16/25 11:31 AM, azey wrote:
> At some point after b5d2d75e079a ("net/ipv6: Do not allow device only
> routes via the multipath API"), the IPv6 stack was updated such that
> device-only multipath routes can be installed and work correctly, but
> still weren't allowed in the code.
> 
> This change removes the has_gateway check from rtm_to_fib6_multipath_config()
> and the fib_nh_gw_family check from rt6_qualify_for_ecmp(), allowing
> device-only multipath routes to be installed again.
> 

My recollection is that device only legs of an ECMP route is only valid
with the separate nexthop code. Added Nicholas (author of the original
IPv4 multipath code) to keep me honest.