net: bridge: mst: Multiple Spanning Tree (MST) mode

Allow the user to switch from the current per-VLAN STP mode to an MST
mode.

Up to this point, per-VLAN STP states where always isolated from each
other. This is in contrast to the MSTP standard (802.1Q-2018, Clause
13.5), where VLANs are grouped into MST instances (MSTIs), and the
state is managed on a per-MSTI level, rather that at the per-VLAN
level.

Perhaps due to the prevalence of the standard, many switching ASICs
are built after the same model. Therefore, add a corresponding MST
mode to the bridge, which we can later add offloading support for in a
straight-forward way.

For now, all VLANs are fixed to MSTI 0, also called the Common
Spanning Tree (CST). That is, all VLANs will follow the port-global
state.

Upcoming changes will make this actually useful by allowing VLANs to
be mapped to arbitrary MSTIs and allow individual MSTI states to be
changed.

Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 37 insertions, 0 deletions

diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 48bc61ebc211..c2190c8841fb 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -178,6 +178,7 @@ enum {
  * @br_mcast_ctx: if MASTER flag set, this is the global vlan multicast context
  * @port_mcast_ctx: if MASTER flag unset, this is the per-port/vlan multicast
  *                  context
+ * @msti: if MASTER flag set, this holds the VLANs MST instance
  * @vlist: sorted list of VLAN entries
  * @rcu: used for entry destruction
  *
@@ -210,6 +211,8 @@ struct net_bridge_vlan {
 		struct net_bridge_mcast_port	port_mcast_ctx;
 	};
 
+	u16				msti;
+
 	struct list_head		vlist;
 
 	struct rcu_head			rcu;
@@ -445,6 +448,7 @@ enum net_bridge_opts {
 	BROPT_NO_LL_LEARN,
 	BROPT_VLAN_BRIDGE_BINDING,
 	BROPT_MCAST_VLAN_SNOOPING_ENABLED,
+	BROPT_MST_ENABLED,
 };
 
 struct net_bridge {
@@ -1765,6 +1769,39 @@ static inline bool br_vlan_state_allowed(u8 state, bool learn_allow)
 }
 #endif
 
+/* br_mst.c */
+#ifdef CONFIG_BRIDGE_VLAN_FILTERING
+DECLARE_STATIC_KEY_FALSE(br_mst_used);
+static inline bool br_mst_is_enabled(struct net_bridge *br)
+{
+	return static_branch_unlikely(&br_mst_used) &&
+		br_opt_get(br, BROPT_MST_ENABLED);
+}
+
+int br_mst_set_state(struct net_bridge_port *p, u16 msti, u8 state,
+		     struct netlink_ext_ack *extack);
+void br_mst_vlan_init_state(struct net_bridge_vlan *v);
+int br_mst_set_enabled(struct net_bridge *br, bool on,
+		       struct netlink_ext_ack *extack);
+#else
+static inline bool br_mst_is_enabled(struct net_bridge *br)
+{
+	return false;
+}
+
+static inline int br_mst_set_state(struct net_bridge_port *p, u16 msti,
+				   u8 state, struct netlink_ext_ack *extack)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int br_mst_set_enabled(struct net_bridge *br, bool on,
+				     struct netlink_ext_ack *extack)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
 struct nf_br_ops {
 	int (*br_dev_xmit_hook)(struct sk_buff *skb);
 };