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

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Message-ID: <6a42127f-77bd-4a25-af61-8bb8adb666c1@6wind.com>
Date: Wed, 2 Jul 2025 18:17:44 +0200
From: Nicolas Dichtel <nicolas.dichtel@...nd.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Gabriel Goller <g.goller@...xmox.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
 Jonathan Corbet <corbet@....net>, David Ahern <dsahern@...nel.org>,
 netdev@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] ipv6: add `force_forwarding` sysctl to enable
 per-interface forwarding

Le 02/07/2025 à 18:10, Jakub Kicinski a écrit :
> 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))
+1