Re: [net-next v2 11/11] net: bridge: mcast: export multicast router presence adjacent to a port

Nikolay Aleksandrov
2021-05-11T09:23:38Z

On 09/05/2021 22:45, Linus Lüssing wrote:
> To properly support routable multicast addresses in batman-adv in a
> group-aware way, a batman-adv node needs to know if it serves multicast
> routers.
>
> This adds a function to the bridge to export this so that batman-adv
> can then make full use of the Multicast Router Discovery capability of
> the bridge.
>
> Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
> ---
> net/bridge/br_multicast.c | 58 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 58 insertions(+)
>
> diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
> index b625fd6..e963de5 100644
> --- a/net/bridge/br_multicast.c
> +++ b/net/bridge/br_multicast.c
> @@ -4061,6 +4061,64 @@ unlock:
> }
> EXPORT_SYMBOL_GPL(br_multicast_has_querier_adjacent);
>
> +/**
> + * br_multicast_has_router_adjacent - Checks for a router behind a bridge port
> + * @dev: The bridge port adjacent to which to check for a multicast router
> + * @proto: The protocol family to check for: IGMP -> ETH_P_IP, MLD -> ETH_P_IPV6
> + *
> + * Checks whether the given interface has a bridge on top and if so returns
> + * true if a multicast router is behind one of the other ports of this
> + * bridge. Otherwise returns false.
> + */
> +bool br_multicast_has_router_adjacent(struct net_device *dev, int proto)
> +{
> + struct net_bridge_port *port, *p;
> + bool ret = false;
> +
> + rcu_read_lock();
> + if (!netif_is_bridge_port(dev))
> + goto unlock;
> +
> + port = br_port_get_rcu(dev);

You can combine both of netif_is_bridge_port and br_port_get_rcu() checks and use
br_port_get_check_rcu(). Then you can also drop the port->br check.

> + if (!port || !port->br)
> + goto unlock;
> +
> + switch (proto) {
> + case ETH_P_IP:
> + hlist_for_each_entry_rcu(p, &port->br->ip4_mc_router_list,
> + ip4_rlist) {
> + if (p == port)
> + continue;
> +
> + ret = true;
> + goto unlock;
> + }
> + break;
> +#if IS_ENABLED(CONFIG_IPV6)
> + case ETH_P_IPV6:
> + hlist_for_each_entry_rcu(p, &port->br->ip6_mc_router_list,
> + ip6_rlist) {
> + if (p == port)
> + continue;
> +
> + ret = true;
> + goto unlock;
> + }
> + break;
> +#endif
> + default:
> + /* when compiled without IPv6 support, be conservative and
> + * always assume presence of an IPv6 multicast router
> + */
> + ret = true;
> + }
> +
> +unlock:
> + rcu_read_unlock();
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(br_multicast_has_router_adjacent);
> +
> static void br_mcast_stats_add(struct bridge_mcast_stats __percpu *stats,
> const struct sk_buff *skb, u8 type, u8 dir)
> {
>