Allow a VLAN to change its MSTID. In particular, allow multiple VLANs
to use the same MSTID. This is a global VLAN setting, i.e. any VLANs
bound to the same MSTID will share their per-VLAN STP states on all
bridge ports.

Example:

By default, each VLAN is placed in a separate MSTID:

root@coronet:~# ip link add dev br0 type bridge vlan_filtering 1
root@coronet:~# ip link set dev eth1 master br0
root@coronet:~# bridge vlan add dev eth1 vid 2 pvid untagged
root@coronet:~# bridge vlan add dev eth1 vid 3
root@coronet:~# bridge vlan global
port              vlan-id
br0               1
                    mcast_snooping 1 mca<redacted>_interval 1000 mstid 1
                  2
                    mcast_snooping 1 mca<redacted>_interval 1000 mstid 2
                  3
                    mcast_snooping 1 mca<redacted>_interval 1000 mstid 3

Once two or more VLANs are bound to the same MSTID, their states move
in lockstep, independent of which VID is used to access the state:

root@coronet:~# bridge vlan global set dev br0 vid 2 mstid 10
root@coronet:~# bridge vlan global set dev br0 vid 3 mstid 10
root@coronet:~# bridge -d vlan global
port              vlan-id
br0               1
                    mcast_snooping 1 mca<redacted>_interval 1000 mstid 1
                  2-3
                    mcast_snooping 1 mca<redacted>_interval 1000 mstid 10

root@coronet:~# bridge vlan set dev eth1 vid 2 state blocking
root@coronet:~# bridge -d vlan
port              vlan-id
eth1              1 Egress Untagged
                    state forwarding mcast_router 1
                  2 PVID Egress Untagged
                    state blocking mcast_router 1
                  3
                    state blocking mcast_router 1
br0               1 PVID Egress Untagged
                    state forwarding mcast_router 1
root@coronet:~# bridge vlan set dev eth1 vid 3 state forwarding
root@coronet:~# bridge -d vlan
port              vlan-id
eth1              1 Egress Untagged
                    state forwarding mcast_router 1
                  2 PVID Egress Untagged
                    state forwarding mcast_router 1
                  3
                    state forwarding mcast_router 1
br0               1 PVID Egress Untagged
                    state forwarding mcast_router 1

Signed-off-by: Tobias Waldekranz <[email protected]>
---
 include/uapi/linux/if_bridge.h |  1 +
 net/bridge/br_private.h        |  3 ++
 net/bridge/br_vlan.c           | 53 ++++++++++++++++++++++++++--------
 net/bridge/br_vlan_options.c   | 17 ++++++++++-
 4 files changed, 61 insertions(+), 13 deletions(-)

diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
index 2711c3522010..4a971b419d9f 100644
--- a/include/uapi/linux/if_bridge.h
+++ b/include/uapi/linux/if_bridge.h
@@ -564,6 +564,7 @@ enum {
        BRIDGE_VLANDB_GOPTS_MCAST_QUERIER,
        BRIDGE_VLANDB_GOPTS_MCAST_ROUTER_PORTS,
        BRIDGE_VLANDB_GOPTS_MCAST_QUERIER_STATE,
+       BRIDGE_VLANDB_GOPTS_MSTID,
        __BRIDGE_VLANDB_GOPTS_MAX
 };
 #define BRIDGE_VLANDB_GOPTS_MAX (__BRIDGE_VLANDB_GOPTS_MAX - 1)
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 7781e7a4449b..5b121cf7aabe 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -1759,6 +1759,9 @@ static inline void br_vlan_set_state(struct 
net_bridge_vlan *v, u8 state)
        mst->state = state;
 }
 
+u16 br_vlan_mstid_get(const struct net_bridge_vlan *v);
+int br_vlan_mstid_set(struct net_bridge_vlan *v, u16 mstid);
+
 static inline u8 br_vlan_get_pvid_state(const struct net_bridge_vlan_group *vg)
 {
        return READ_ONCE(vg->pvid_state);
diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index b0383ec6cc91..459e84a7354d 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -41,10 +41,8 @@ static void br_vlan_mst_rcu_free(struct rcu_head *rcu)
        kfree(mst);
 }
 
-static void br_vlan_mst_put(struct net_bridge_vlan *v)
+static void br_vlan_mst_put(struct br_vlan_mst *mst)
 {
-       struct br_vlan_mst *mst = rtnl_dereference(v->mst);
-
        if (refcount_dec_and_test(&mst->refcnt))
                call_rcu(&mst->rcu, br_vlan_mst_rcu_free);
 }
@@ -153,13 +151,17 @@ static struct br_vlan_mst *br_vlan_group_mst_get(struct 
net_bridge_vlan_group *v
 
 static int br_vlan_mst_migrate(struct net_bridge_vlan *v, u16 mstid)
 {
+       struct br_vlan_mst *mst, *old_mst;
        struct net_bridge_vlan_group *vg;
-       struct br_vlan_mst *mst;
+       struct net_bridge *br;
 
-       if (br_vlan_is_master(v))
-               vg = br_vlan_group(v->br);
-       else
+       if (br_vlan_is_master(v)) {
+               br = v->br;
+               vg = br_vlan_group(br);
+       } else {
+               br = v->port->br;
                vg = nbp_vlan_group(v->port);
+       }
 
        mst = br_vlan_group_mst_get(vg, mstid);
        if (!mst) {
@@ -168,10 +170,37 @@ static int br_vlan_mst_migrate(struct net_bridge_vlan *v, 
u16 mstid)
                        return -ENOMEM;
        }
 
-       if (rtnl_dereference(v->mst))
-               br_vlan_mst_put(v);
-
+       old_mst = rtnl_dereference(v->mst);
        rcu_assign_pointer(v->mst, mst);
+
+       if (old_mst)
+               br_vlan_mst_put(old_mst);
+
+       return 0;
+}
+
+int br_vlan_mstid_set(struct net_bridge_vlan *v, u16 mstid)
+{
+       struct net_bridge *br = v->br;
+       struct net_bridge_port *p;
+       int err;
+
+       err = br_vlan_mst_migrate(v, mstid);
+       if (err)
+               return err;
+
+       list_for_each_entry(p, &br->port_list, list) {
+               struct net_bridge_vlan_group *vg = nbp_vlan_group(p);
+               struct net_bridge_vlan *portv;
+
+               portv = br_vlan_lookup(&vg->vlan_hash, v->vid);
+               if (!portv)
+                       continue;
+
+               err = br_vlan_mst_migrate(portv, mstid);
+               if (err)
+                       return err;
+       }
        return 0;
 }
 
@@ -501,7 +530,7 @@ static int __vlan_add(struct net_bridge_vlan *v, u16 flags,
        return err;
 
 out_mst_init:
-       br_vlan_mst_put(v);
+       br_vlan_mst_put(rtnl_dereference(v->mst));
 
 out_fdb_insert:
        if (br_vlan_should_use(v)) {
@@ -570,7 +599,7 @@ static int __vlan_del(struct net_bridge_vlan *v)
                call_rcu(&v->rcu, nbp_vlan_rcu_free);
        }
 
-       br_vlan_mst_put(v);
+       br_vlan_mst_put(rtnl_dereference(v->mst));
        br_vlan_put_master(masterv);
 out:
        return err;
diff --git a/net/bridge/br_vlan_options.c b/net/bridge/br_vlan_options.c
index 0b1099709d4b..1c0fd55fe6c9 100644
--- a/net/bridge/br_vlan_options.c
+++ b/net/bridge/br_vlan_options.c
@@ -380,6 +380,9 @@ bool br_vlan_global_opts_fill(struct sk_buff *skb, u16 vid, 
u16 vid_range,
 #endif
 #endif
 
+       if (nla_put_u16(skb, BRIDGE_VLANDB_GOPTS_MSTID, 
br_vlan_mstid_get(v_opts)))
+               goto out_err;
+
        nla_nest_end(skb, nest);
 
        return true;
@@ -411,7 +414,9 @@ static size_t rtnl_vlan_global_opts_nlmsg_size(const struct 
net_bridge_vlan *v)
                + nla_total_size(0) /* BRIDGE_VLANDB_GOPTS_MCAST_ROUTER_PORTS */
                + br_rports_size(&v->br_mcast_ctx) /* 
BRIDGE_VLANDB_GOPTS_MCAST_ROUTER_PORTS */
 #endif
-               + nla_total_size(sizeof(u16)); /* BRIDGE_VLANDB_GOPTS_RANGE */
+               + nla_total_size(sizeof(u16)) /* BRIDGE_VLANDB_GOPTS_RANGE */
+               + nla_total_size(sizeof(u16)) /* BRIDGE_VLANDB_GOPTS_MSTID */
+               + 0;
 }
 
 static void br_vlan_global_opts_notify(const struct net_bridge *br,
@@ -560,6 +565,15 @@ static int br_vlan_process_global_one_opts(const struct 
net_bridge *br,
        }
 #endif
 #endif
+       if (tb[BRIDGE_VLANDB_GOPTS_MSTID]) {
+               u16 mstid;
+
+               mstid = nla_get_u16(tb[BRIDGE_VLANDB_GOPTS_MSTID]);
+               err = br_vlan_mstid_set(v, mstid);
+               if (err)
+                       return err;
+               *changed = true;
+       }
 
        return 0;
 }
@@ -579,6 +593,7 @@ static const struct nla_policy 
br_vlan_db_gpol[BRIDGE_VLANDB_GOPTS_MAX + 1] = {
        [BRIDGE_VLANDB_GOPTS_MCAST_QUERIER_INTVL]       = { .type = NLA_U64 },
        [BRIDGE_VLANDB_GOPTS_MCAST_STARTUP_QUERY_INTVL] = { .type = NLA_U64 },
        [BRIDGE_VLANDB_GOPTS_MCAST_QUERY_RESPONSE_INTVL] = { .type = NLA_U64 },
+       [BRIDGE_VLANDB_GOPTS_MSTID] = NLA_POLICY_RANGE(NLA_U16, 1, 4094),
 };
 
 int br_vlan_rtm_process_global_options(struct net_device *dev,
-- 
2.25.1

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