Re: [PATCH net-next 3/5] net: bridge: mcast: check if snooping is enabled for active state

[Simon Horman <horms@kernel.org>]

On Thu, May 22, 2025 at 09:17:05PM +0200, Linus Lüssing wrote:
> To be able to use the upcoming SWITCHDEV_ATTR_ID_BRIDGE_MC_ACTIVE
> as a potential replacement for SWITCHDEV_ATTR_ID_BRIDGE_MC_DISABLED
> also check and toggle the active state if multicast snooping is enabled
> or disabled. So that MC_ACTIVE not only checks the querier state, but
> also if multicast snooping is enabled in general.
> 
> Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
> ---
>  include/uapi/linux/if_link.h |  6 ++++--
>  net/bridge/br_multicast.c    | 35 +++++++++++++++++++++++++++++++++--
>  2 files changed, 37 insertions(+), 4 deletions(-)
> 
> diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> index 41f6c461ab32..479d039477cb 100644
> --- a/include/uapi/linux/if_link.h
> +++ b/include/uapi/linux/if_link.h
> @@ -746,12 +746,14 @@ enum in6_addr_gen_mode {
>   * @IFLA_BR_MCAST_ACTIVE_V4
>   *   Bridge IPv4 mcast active state, read only.
>   *
> - *   1 if an IGMP querier is present, 0 otherwise.
> + *   1 if *IFLA_BR_MCAST_SNOOPING* is enabled and 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.
> + *   1 if *IFLA_BR_MCAST_SNOOPING* is enabled and an MLD querier is present,
> + *   0 otherwise.
>   */
>  enum {
>  	IFLA_BR_UNSPEC,
> diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
> index b66d2173e321..0bbaa21c1479 100644
> --- a/net/bridge/br_multicast.c
> +++ b/net/bridge/br_multicast.c
> @@ -1150,6 +1150,7 @@ static int br_ip6_multicast_check_active(struct net_bridge_mcast *brmctx,
>   *
>   * The multicast active state is set, per protocol family, if:
>   *
> + * - multicast snooping is enabled
>   * - an IGMP/MLD querier is present
>   * - for own IPv6 MLD querier: an IPv6 address is configured on the bridge
>   *
> @@ -1169,6 +1170,13 @@ static int __br_multicast_update_active(struct net_bridge_mcast *brmctx,
>  
>  	lockdep_assert_held_once(&brmctx->br->multicast_lock);
>  
> +	if (!br_opt_get(brmctx->br, BROPT_MULTICAST_ENABLED))
> +		force_inactive = true;
> +
> +	if (br_opt_get(brmctx->br, BROPT_MCAST_VLAN_SNOOPING_ENABLED) &&
> +	    br_multicast_ctx_vlan_disabled(brmctx))
> +		force_inactive = true;
> +
>  	ip4_active = !force_inactive;
>  	ip6_active = !force_inactive;
>  	ip4_changed = br_ip4_multicast_check_active(brmctx, &ip4_active);
> @@ -1396,6 +1404,22 @@ static struct sk_buff *br_multicast_alloc_query(struct net_bridge_mcast *brmctx,
>  	return NULL;
>  }
>  
> +static int br_multicast_toggle_enabled(struct net_bridge *br, bool on,
> +				       struct netlink_ext_ack *extack)
> +{
> +	int err, old;
> +
> +	br_opt_toggle(br, BROPT_MULTICAST_ENABLED, on);
> +
> +	err = br_multicast_update_active(&br->multicast_ctx, extack);
> +	if (err && err != -EOPNOTSUPP) {
> +		br_opt_toggle(br, BROPT_MULTICAST_ENABLED, old);

Hi Linus,

Old appears to be used uninitialised here.

Flagged by allmodconfig builds on x86_64 with clang-20.1.4.

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