linux-kernel - Re: [PATCH net-next v6] ipv6: add `force_forwarding` sysctl to enable per-interface forwarding

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Message-ID: <hf2yl42fk2dy7nbrwkhcxkp6eaopv2mnjiuh66ehgk3eevyeq3@edkzqjrcprkp>
Date: Tue, 22 Jul 2025 10:17:43 +0200
From: Gabriel Goller <g.goller@...xmox.com>
To: Paolo Abeni <pabeni@...hat.com>
Cc: Nicolas Dichtel <nicolas.dichtel@...nd.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Simon Horman <horms@...nel.org>, 
	Jonathan Corbet <corbet@....net>, David Ahern <dsahern@...nel.org>, Shuah Khan <shuah@...nel.org>, 
	netdev@...r.kernel.org, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next v6] ipv6: add `force_forwarding` sysctl to
 enable per-interface forwarding

On 15.07.2025 15:34, Paolo Abeni wrote:
>On 7/11/25 2:42 PM, Gabriel Goller wrote:
>> It is currently impossible to enable ipv6 forwarding on a per-interface
>> basis like in ipv4. To enable forwarding on an ipv6 interface we need to
>> enable it on all interfaces and disable it on the other interfaces using
>> a netfilter rule. This is especially cumbersome if you have lots of
>> interface and only want to enable forwarding on a few. According to the
>> sysctl docs [0] the `net.ipv6.conf.all.forwarding` enables forwarding
>> for all interfaces, while the interface-specific
>> `net.ipv6.conf.<interface>.forwarding` configures the interface
>> Host/Router configuration.
>>
>> Introduce a new sysctl flag `force_forwarding`, which can be set on every
>> interface. The ip6_forwarding function will then check if the global
>> forwarding flag OR the force_forwarding flag is active and forward the
>> packet.
>>
>> To preserver backwards-compatibility reset the flag (on all interfaces)
>> to 0 if the net.ipv6.conf.all.forwarding flag is set to 0.
>>
>> Add a short selftest that checks if a packet gets forwarded with and
>> without `force_forwarding`.
>>
>> [0]: https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt
>>
>> Signed-off-by: Gabriel Goller <g.goller@...xmox.com>
>> Acked-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>
>> ---
>> v6:
>>     * rebase
>>     * remove brackts around single line
>>     * add 'nodad' to addresses in selftest to avoid sporadic failures
>
>I'm sorry, but it still does not apply. Please rebase again and re-submit.
>
>Thanks,
>
>Paolo

Thanks for the review! Rebased again, should apply now.