Re: [PATCH net-next 2/5] net: bridge: mcast: export ip{4,6}_active state to netlink

[Ido Schimmel <idosch@nvidia.com>]

On Thu, May 22, 2025 at 09:17:04PM +0200, Linus Lüssing wrote:
> diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> index 318386cc5b0d..41f6c461ab32 100644
> --- a/include/uapi/linux/if_link.h
> +++ b/include/uapi/linux/if_link.h
> @@ -742,6 +742,16 @@ enum in6_addr_gen_mode {
>   * @IFLA_BR_FDB_MAX_LEARNED
>   *   Set the number of max dynamically learned FDB entries for the current
>   *   bridge.
> + *
> + * @IFLA_BR_MCAST_ACTIVE_V4
> + *   Bridge IPv4 mcast active state, read only.
> + *
> + *   1 if an IGMP querier is present, 0 otherwise.
> + *
> + * @IFLA_BR_MCAST_ACTIVE_V6
> + *   Bridge IPv4 mcast active state, read only.
> + *
> + *   1 if an MLD querier is present, 0 otherwise.
>   */

[...]

> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
> index 6e337937d0d7..7829d2842851 100644
> --- a/net/bridge/br_netlink.c
> +++ b/net/bridge/br_netlink.c
> @@ -1264,7 +1264,9 @@ static const struct nla_policy br_policy[IFLA_BR_MAX + 1] = {
>  	[IFLA_BR_VLAN_STATS_ENABLED] = { .type = NLA_U8 },
>  	[IFLA_BR_MCAST_STATS_ENABLED] = { .type = NLA_U8 },
>  	[IFLA_BR_MCAST_IGMP_VERSION] = { .type = NLA_U8 },
> +	[IFLA_BR_MCAST_ACTIVE_V4] = { .type = NLA_U8 },
>  	[IFLA_BR_MCAST_MLD_VERSION] = { .type = NLA_U8 },
> +	[IFLA_BR_MCAST_ACTIVE_V6] = { .type = NLA_U8 },

The new attributes should be set to 'NLA_REJECT' if they are meant to be
read only. They can also be removed from the policy, but being explicit
and using 'NLA_REJECT' is better IMO.