[PATCH v5 net-next 01/15] net: bridge: mst: Multiple Spanning Tree (MST) mode

Tobias Waldekranz
2022-03-16T15:09:18Z

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>
---
include/uapi/linux/if_bridge.h | 1 +
net/bridge/Makefile | 2 +-
net/bridge/br.c | 5 ++
net/bridge/br_input.c | 17 ++++++-
net/bridge/br_mst.c | 87 ++++++++++++++++++++++++++++++++++
net/bridge/br_private.h | 37 +++++++++++++++
net/bridge/br_stp.c | 6 +++
net/bridge/br_vlan.c | 20 +++++++-
net/bridge/br_vlan_options.c | 5 ++
9 files changed, 176 insertions(+), 4 deletions(-)
create mode 100644 net/bridge/br_mst.c

diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
index 2711c3522010..30a242195ced 100644
--- a/include/uapi/linux/if_bridge.h
+++ b/include/uapi/linux/if_bridge.h
@@ -759,6 +759,7 @@ struct br_mcast_stats {
enum br_boolopt_id {
BR_BOOLOPT_NO_LL_LEARN,
BR_BOOLOPT_MCAST_VLAN_SNOOPING,
+ BR_BOOLOPT_MST_ENABLE,
BR_BOOLOPT_MAX
};

diff --git a/net/bridge/Makefile b/net/bridge/Makefile
index 7fb9a021873b..24bd1c0a9a5a 100644
--- a/net/bridge/Makefile
+++ b/net/bridge/Makefile
@@ -20,7 +20,7 @@ obj-$(CONFIG_BRIDGE_NETFILTER) += br_netfilter.o

bridge-$(CONFIG_BRIDGE_IGMP_SNOOPING) += br_multicast.o br_mdb.o br_multicast_eht.o

-bridge-$(CONFIG_BRIDGE_VLAN_FILTERING) += br_vlan.o br_vlan_tunnel.o br_vlan_options.o
+bridge-$(CONFIG_BRIDGE_VLAN_FILTERING) += br_vlan.o br_vlan_tunnel.o br_vlan_options.o br_mst.o

bridge-$(CONFIG_NET_SWITCHDEV) += br_switchdev.o

diff --git a/net/bridge/br.c b/net/bridge/br.c
index b1dea3febeea..96e91d69a9a8 100644
--- a/net/bridge/br.c
+++ b/net/bridge/br.c
@@ -265,6 +265,9 @@ int br_boolopt_toggle(struct net_bridge *br, enum br_boolopt_id opt, bool on,
case BR_BOOLOPT_MCAST_VLAN_SNOOPING:
err = br_multicast_toggle_vlan_snooping(br, on, extack);
break;
+ case BR_BOOLOPT_MST_ENABLE:
+ err = br_mst_set_enabled(br, on, extack);
+ break;
default:
/* shouldn't be called with unsupported options */
WARN_ON(1);
@@ -281,6 +284,8 @@ int br_boolopt_get(const struct net_bridge *br, enum br_boolopt_id opt)
return br_opt_get(br, BROPT_NO_LL_LEARN);
case BR_BOOLOPT_MCAST_VLAN_SNOOPING:
return br_opt_get(br, BROPT_MCAST_VLAN_SNOOPING_ENABLED);
+ case BR_BOOLOPT_MST_ENABLE:
+ return br_opt_get(br, BROPT_MST_ENABLED);
default:
/* shouldn't be called with unsupported options */
WARN_ON(1);
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index e0c13fcc50ed..196417859c4a 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -78,13 +78,22 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
u16 vid = 0;
u8 state;

- if (!p || p->state == BR_STATE_DISABLED)
+ if (!p)
goto drop;

br = p->br;
+
+ if (br_mst_is_enabled(br)) {
+ state = BR_STATE_FORWARDING;
+ } else {
+ if (p->state == BR_STATE_DISABLED)
+ goto drop;
+
+ state = p->state;
+ }
+
brmctx = &p->br->multicast_ctx;
pmctx = &p->multicast_ctx;
- state = p->state;
if (!br_allowed_ingress(p->br, nbp_vlan_group_rcu(p), skb, &vid,
&state, &vlan))
goto out;
@@ -370,9 +379,13 @@ static rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
return RX_HANDLER_PASS;

forward:
+ if (br_mst_is_enabled(p->br))
+ goto defer_stp_filtering;
+
switch (p->state) {
case BR_STATE_FORWARDING:
case BR_STATE_LEARNING:
+defer_stp_filtering:
if (ether_addr_equal(p->br->dev->dev_addr, dest))
skb->pkt_type = PACKET_HOST;

diff --git a/net/bridge/br_mst.c b/net/bridge/br_mst.c
new file mode 100644
index 000000000000..0f9f596f86bc
--- /dev/null
+++ b/net/bridge/br_mst.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Bridge Multiple Spanning Tree Support
+ *
+ * Authors:
+ * Tobias Waldekranz <tobias@waldekranz.com>
+ */
+
+#include <linux/kernel.h>
+
+#include "br_private.h"
+
+DEFINE_STATIC_KEY_FALSE(br_mst_used);
+
+static void br_mst_vlan_set_state(struct net_bridge_port *p, struct net_bridge_vlan *v,
+ u8 state)
+{
+ struct net_bridge_vlan_group *vg = nbp_vlan_group(p);
+
+ if (v->state == state)
+ return;
+
+ br_vlan_set_state(v, state);
+
+ if (v->vid == vg->pvid)
+ br_vlan_set_pvid_state(vg, state);
+}
+
+int br_mst_set_state(struct net_bridge_port *p, u16 msti, u8 state,
+ struct netlink_ext_ack *extack)
+{
+ struct net_bridge_vlan_group *vg;
+ struct net_bridge_vlan *v;
+
+ vg = nbp_vlan_group(p);
+ if (!vg)
+ return 0;
+
+ list_for_each_entry(v, &vg->vlan_list, vlist) {
+ if (v->brvlan->msti != msti)
+ continue;
+
+ br_mst_vlan_set_state(p, v, state);
+ }
+
+ return 0;
+}
+
+void br_mst_vlan_init_state(struct net_bridge_vlan *v)
+{
+ /* VLANs always start out in MSTI 0 (CST) */
+ v->msti = 0;
+
+ if (br_vlan_is_master(v))
+ v->state = BR_STATE_FORWARDING;
+ else
+ v->state = v->port->state;
+}
+
+int br_mst_set_enabled(struct net_bridge *br, bool on,
+ struct netlink_ext_ack *extack)
+{
+ struct net_bridge_vlan_group *vg;
+ struct net_bridge_port *p;
+
+ list_for_each_entry(p, &br->port_list, list) {
+ vg = nbp_vlan_group(p);
+
+ if (!vg->num_vlans)
+ continue;
+
+ NL_SET_ERR_MSG(extack,
+ "MST mode can't be changed while VLANs exist");
+ return -EBUSY;
+ }
+
+ if (br_opt_get(br, BROPT_MST_ENABLED) == on)
+ return 0;
+
+ if (on)
+ static_branch_enable(&br_mst_used);
+ else
+ static_branch_disable(&br_mst_used);
+
+ br_opt_toggle(br, BROPT_MST_ENABLED, on);
+ return 0;
+}
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);
};
diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c
index 1d80f34a139c..7d27b2e6038f 100644
--- a/net/bridge/br_stp.c
+++ b/net/bridge/br_stp.c
@@ -43,6 +43,12 @@ void br_set_state(struct net_bridge_port *p, unsigned int state)
return;

p->state = state;
+ if (br_opt_get(p->br, BROPT_MST_ENABLED)) {
+ err = br_mst_set_state(p, 0, state, NULL);
+ if (err)
+ br_warn(p->br, "error setting MST state on port %u(%s)\n",
+ p->port_no, netdev_name(p->dev));
+ }
err = switchdev_port_attr_set(p->dev, &attr, NULL);
if (err && err != -EOPNOTSUPP)
br_warn(p->br, "error setting offload STP state on port %u(%s)\n",
diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 7557e90b60e1..0f5e75ccac79 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -226,6 +226,24 @@ static void nbp_vlan_rcu_free(struct rcu_head *rcu)
kfree(v);
}

+static void br_vlan_init_state(struct net_bridge_vlan *v)
+{
+ struct net_bridge *br;
+
+ if (br_vlan_is_master(v))
+ br = v->br;
+ else
+ br = v->port->br;
+
+ if (br_opt_get(br, BROPT_MST_ENABLED)) {
+ br_mst_vlan_init_state(v);
+ return;
+ }
+
+ v->state = BR_STATE_FORWARDING;
+ v->msti = 0;
+}
+
/* This is the shared VLAN add function which works for both ports and bridge
* devices. There are four possible calls to this function in terms of the
* vlan entry type:
@@ -322,7 +340,7 @@ static int __vlan_add(struct net_bridge_vlan *v, u16 flags,
}

/* set the state before publishing */
- v->state = BR_STATE_FORWARDING;
+ br_vlan_init_state(v);

err = rhashtable_lookup_insert_fast(&vg->vlan_hash, &v->vnode,
br_vlan_rht_params);
diff --git a/net/bridge/br_vlan_options.c b/net/bridge/br_vlan_options.c
index a6382973b3e7..09112b56e79c 100644
--- a/net/bridge/br_vlan_options.c
+++ b/net/bridge/br_vlan_options.c
@@ -99,6 +99,11 @@ static int br_vlan_modify_state(struct net_bridge_vlan_group *vg,
return -EBUSY;
}

+ if (br_opt_get(br, BROPT_MST_ENABLED)) {
+ NL_SET_ERR_MSG_MOD(extack, "Can't modify vlan state directly when MST is enabled");
+ return -EBUSY;
+ }
+
if (v->state == state)
return 0;

--
2.25.1