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Subject[PATCH net-next 2/2] net: bridge: mcast: export multicast router presence adjacent to a port
Date
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>
---
include/linux/if_bridge.h | 8 ++++++
net/bridge/br_multicast.c | 58 +++++++++++++++++++++++++++++++++++++++
2 files changed, 66 insertions(+)

diff --git a/include/linux/if_bridge.h b/include/linux/if_bridge.h
index 2cc35038a8ca..12e9a32dbca0 100644
--- a/include/linux/if_bridge.h
+++ b/include/linux/if_bridge.h
@@ -67,6 +67,7 @@ int br_multicast_list_adjacent(struct net_device *dev,
struct list_head *br_ip_list);
bool br_multicast_has_querier_anywhere(struct net_device *dev, int proto);
bool br_multicast_has_querier_adjacent(struct net_device *dev, int proto);
+bool br_multicast_has_router_adjacent(struct net_device *dev, int proto);
bool br_multicast_enabled(const struct net_device *dev);
bool br_multicast_router(const struct net_device *dev);
int br_mdb_replay(struct net_device *br_dev, struct net_device *dev,
@@ -87,6 +88,13 @@ static inline bool br_multicast_has_querier_adjacent(struct net_device *dev,
{
return false;
}
+
+static inline bool br_multicast_has_router_adjacent(struct net_device *dev,
+ int proto)
+{
+ return true;
+}
+
static inline bool br_multicast_enabled(const struct net_device *dev)
{
return false;
diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 0ebdbf09f44c..4afaf011f171 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -4013,6 +4013,64 @@ bool br_multicast_has_querier_adjacent(struct net_device *dev, int proto)
}
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);
+ 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)
{
--
2.31.0
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