Re: [PATCH net-next] ipv6: always apply all.force_forwarding to every interface

[Nicolas Dichtel]

Le 12/11/2026 à 14:41, Gabriel Goller a écrit :
> Currently, writing to all.force_forwarding updates the interfaces
> only if the value stored in all.force_forwarding changes. Setting an
> interface to a different value and then writing the same value to all
> leaves that interface unchanged:
> 
>   # sysctl -wq net.ipv6.conf.all.force_forwarding=1
>   # sysctl -wq net.ipv6.conf.dummy1.force_forwarding=0
>   # sysctl -wq net.ipv6.conf.all.force_forwarding=1
>   # sysctl net.ipv6.conf.dummy1.force_forwarding
>   net.ipv6.conf.dummy1.force_forwarding = 0
> 
> Apply every write to all.force_forwarding to all interfaces, even when
> its stored value is unchanged, matching all.forwarding. In the example,
> the final write to all now sets dummy1.force_forwarding back to 1.
> 
> Also match forwarding's locking: take RTNL for every write and compare
> the old and new values under the lock, rather than returning early based
> on an unlocked comparison. Send netconf notifications only for actual
> value changes, including for default and per-interface writes.
> 
> Note that IPv4's forwarding does not behave like this, but we won't
> change that one and align force_forward to the IPv6 forwarding.
> 
> Fixes: f24987ef6959 ("ipv6: add `force_forwarding` sysctl to enable per-interface forwarding")
> Suggested-by: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>
> Signed-off-by: Gabriel Goller <g.goller@xxxxxxxxxxx>

Reviewed-by: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>