netdev - Re: [PATCH net 1/2] net: fib: restore ECMP balance from loopback

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Message-ID: <willemdebruijn.kernel.1d692ef4130e8@gmail.com>
Date: Mon, 15 Dec 2025 16:45:11 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Vadim Fedorenko <vadim.fedorenko@...ux.dev>, 
 Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
 "David S. Miller" <davem@...emloft.net>, 
 David Ahern <dsahern@...nel.org>, 
 Eric Dumazet <edumazet@...gle.com>, 
 Paolo Abeni <pabeni@...hat.com>, 
 Simon Horman <horms@...nel.org>, 
 Willem de Bruijn <willemb@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>
Cc: Shuah Khan <shuah@...nel.org>, 
 Ido Schimmel <idosch@...dia.com>, 
 netdev@...r.kernel.org
Subject: Re: [PATCH net 1/2] net: fib: restore ECMP balance from loopback

Vadim Fedorenko wrote:
> On 13/12/2025 20:54, Willem de Bruijn wrote:
> > Vadim Fedorenko wrote:
> >> Preference of nexthop with source address broke ECMP for packets with
> >> source address from loopback interface. Original behaviour was to
> >> balance over nexthops while now it uses the latest nexthop from the
> >> group.
> > 
> > How does the loopback device specifically come into this?
> 
> It may be a dummy device as well. The use case is when there are 2 
> physical interfaces and 1 service IP address, distributed by any
> routing protocol. The socket is bound to service, thus it's used in
> route selection.

Can you elaborate a bit more on this. Maybe in the commit message
itself. How is loopback relevant to this service IP.