Re: [PATCH net] netlink: specs: rt-link: fix ipv6 devconf doc

["Asbjørn Sloth Tønnesen" <ast@fiberby.net>]

On 8/27/26 10:55 AM, Paolo Abeni wrote:
> On 8/24/26 12:38 PM, Asbjørn Sloth Tønnesen wrote:
>> devconf is even odder than described in the blamed commit, where bpth
>> IPv4 and IPv6 are described in an identical way:
>> "u32 indexed by ipv?-devconf - 1 on output, on input it's a nest".
>>
>> There are two issues with that line for IPv6:
>>
>> 1) The subtraction is an IPv4 specific quirk, to avoid having an unused
>>     u32 at index 0, thus saving 4 bytes per net device being dumped:
>>
>>     - In include/uapi/linux/ip.h the IPV4_DEVCONF_* enum begins with
>>       IPV4_DEVCONF_FORWARDING = 1, so the enum starts at 1, which is
>>       the reason for the subtraction in the IPv4 variant.
>>
>>     - In include/uapi/linux/ipv6.h the DEVCONF_* enum begins with
>>       DEVCONF_FORWARDING = 0, so subtraction would underflow.
>>
>>     - ipv6_store_devconf() in net/ipv6/addrconf.c also doesn't do the
>>       subtraction in the output path.
>>
>> 2) Setting IPv6 devconf through Netlink is not yet supported, as
>>     IFLA_INET6_CONF is not handled in inet6_set_link_af().
>>
>> Fixes: 720447bd0b24 ("netlink: specs: rt-link: remove implicit structs from devconf")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
> Nowadays net PRs are already too big due more-or-less security-relevant
> changes. I think this is better suited for net-next, with no 'fixes' tag
> nor stable cc, WDYT?

The unsupported input is the main doc correction, that I would like to go into
v7.3 and earlier, as Fernando is planning to add that support for v7.4.

I stumbled upon this, as I was trying to getting rid of some sysctl calls
in an internal provisioning tool.

If the PR size is already an issue for rc1, then I can resubmit when net-next opens.
(I assumed that you were trying to make the net PR sizes into an reversed xmas tree)

It's likely going to end up in stable regardless, it's just easier for Greg and
Sasha when it's tagged.