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From: Nicolas Dichtel <nicolas.dichtel@6wind.com>
To: Gabriel Goller <g.goller@proxmox.com>,
	David Ahern <dsahern@kernel.org>,
	Ido Schimmel <idosch@nvidia.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@kernel.org>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Simon Horman <horms@kernel.org>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next] ipv6: reset all.force_forwarding when disabling all.forwarding
Date: Tue, 10 Nov 2026 18:34:50 +0100	[thread overview]
Message-ID: <1eb85d22-7d2b-460c-82f6-2af15a4875dc@6wind.com> (raw)
In-Reply-To: <20261109-ipv6_reset_all-v1-1-815dfd508246@proxmox.com>

Le 09/11/2026 à 16:53, Gabriel Goller a écrit :
> Disabling all.forwarding resets force_forwarding on every interface, but
> leaves all.force_forwarding set:
> 
>   # sysctl -wq net.ipv6.conf.all.forwarding=1
>   # sysctl -wq net.ipv6.conf.all.force_forwarding=1
>   # sysctl -wq net.ipv6.conf.all.forwarding=0
>   # sysctl net.ipv6.conf.dummy1.force_forwarding
>   net.ipv6.conf.dummy1.force_forwarding = 0
>   # sysctl net.ipv6.conf.all.force_forwarding
>   net.ipv6.conf.all.force_forwarding = 1
> 
> Writing 1 to all.force_forwarding afterwards is ignored because the
> value did not change, so the interfaces are not re-enabled.
> 
> Reset all.force_forwarding too and notify netconf listeners.
> 
> Suggested-by: Ido Schimmel <idosch@nvidia.com>
> Signed-off-by: Gabriel Goller <g.goller@proxmox.com>

There is the same effect if an interface entry is reset:

$ sysctl -wq net.ipv6.conf.all.force_forwarding=1
$ sysctl net.ipv6.conf.ntfp1.force_forwarding net.ipv6.conf.all.force_forwarding
net.ipv6.conf.ntfp1.force_forwarding = 1
net.ipv6.conf.all.force_forwarding = 1
$ sysctl -wq net.ipv6.conf.ntfp1.force_forwarding=0
$ sysctl net.ipv6.conf.ntfp1.force_forwarding net.ipv6.conf.all.force_forwarding
net.ipv6.conf.ntfp1.force_forwarding = 0
net.ipv6.conf.all.force_forwarding = 1
$ sysctl -wq net.ipv6.conf.all.force_forwarding=1
$ sysctl net.ipv6.conf.ntfp1.force_forwarding net.ipv6.conf.all.force_forwarding
net.ipv6.conf.ntfp1.force_forwarding = 0
net.ipv6.conf.all.force_forwarding = 1

Maybe the new value should be applied whatever the old value was for the 'all'
entry (like for net.ipv6.conf.all.forwarding).

Note that, it is the same for ipv4 forwarding:

$ sysctl -wq net.ipv4.conf.all.forwarding=1
$ sysctl net.ipv4.conf.all.forwarding net.ipv4.conf.ntfp1.forwarding
net.ipv4.conf.all.forwarding = 1
net.ipv4.conf.ntfp1.forwarding = 1
$ sysctl -wq net.ipv4.conf.ntfp1.forwarding=0
$ sysctl net.ipv4.conf.all.forwarding net.ipv4.conf.ntfp1.forwarding
net.ipv4.conf.all.forwarding = 1
net.ipv4.conf.ntfp1.forwarding = 0
$ sysctl -wq net.ipv4.conf.all.forwarding=1
$ sysctl net.ipv4.conf.all.forwarding net.ipv4.conf.ntfp1.forwarding
net.ipv4.conf.all.forwarding = 1
net.ipv4.conf.ntfp1.forwarding = 0

but not for ipv6 forwarding:
$ sysctl -wq net.ipv6.conf.all.forwarding=1
$ sysctl net.ipv6.conf.all.forwarding net.ipv6.conf.ntfp1.forwarding
net.ipv6.conf.all.forwarding = 1
net.ipv6.conf.ntfp1.forwarding = 1
$ sysctl -wq net.ipv6.conf.ntfp1.forwarding=0
$ sysctl net.ipv6.conf.all.forwarding net.ipv6.conf.ntfp1.forwarding
net.ipv6.conf.all.forwarding = 1
net.ipv6.conf.ntfp1.forwarding = 0
$ sysctl -wq net.ipv6.conf.all.forwarding=1
$ sysctl net.ipv6.conf.all.forwarding net.ipv6.conf.ntfp1.forwarding
net.ipv6.conf.all.forwarding = 1
net.ipv6.conf.ntfp1.forwarding = 1

      reply	other threads:[~2026-11-10 17:34 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-11-09 15:53 Gabriel Goller
2026-11-10 17:34 ` Nicolas Dichtel [this message]

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