Re: [PATCH v3] ipv6: add `force_forwarding` sysctl to enable per-interface forwarding

Gabriel Goller <g.goller@xxxxxxxxxxx> · Thu, 3 Jul 2025 13:05:11 +0200

On 02.07.2025 09:10, Jakub Kicinski wrote:
On Wed, 2 Jul 2025 17:14:42 +0200 Nicolas Dichtel wrote:
> Should we invert the polarity? It appears that the condition below only
> let's this setting _disable_ forwarding. IMO calling it "force" suggests
> to the user that it will force it to be enabled.
Not sure to follow you. When force_forwarding is set to 1 the forwarding is
always enabled.

sysctl | all.forwarding | iface.force_forwarding | packet processing from iface
       |      0         |           0            |        no forward
       |      0         |           1            |         forward
       |      1         |           0            |         forward
       |      1         |           1            |         forward

Ugh, I can't read comparisons to zero.
Let's switch to more sane logic:

	if (idev && !READ_ONCE(idev->cnf.force_forwarding) &&
	    !READ_ONCE(net->ipv6.devconf_all->forwarding))

Agree!

Thanks for the review.