[PATCH v2 net-next 01/10] net: bridge: mst: Multiple Spanning Tree (MST) mode

From: Tobias Waldekranz
Date: Tue Mar 01 2022 - 05:04:09 EST

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@xxxxxxxxxxxxxx>
---
include/uapi/linux/if_link.h | 1 +
net/bridge/Makefile | 2 +-
net/bridge/br_input.c | 17 +++++++-
net/bridge/br_mst.c | 83 ++++++++++++++++++++++++++++++++++++
net/bridge/br_netlink.c | 14 +++++-
net/bridge/br_private.h | 26 +++++++++++
net/bridge/br_stp.c | 3 ++
net/bridge/br_vlan.c | 20 ++++++++-
net/bridge/br_vlan_options.c | 5 +++
9 files changed, 166 insertions(+), 5 deletions(-)
create mode 100644 net/bridge/br_mst.c

diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index e315e53125f4..7e0a653aafa3 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -482,6 +482,7 @@ enum {
IFLA_BR_VLAN_STATS_PER_PORT,
IFLA_BR_MULTI_BOOLOPT,
IFLA_BR_MCAST_QUERIER_STATE,
+ IFLA_BR_MST_ENABLED,
__IFLA_BR_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_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..ad6e91670fa8
--- /dev/null
+++ b/net/bridge/br_mst.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Bridge Multiple Spanning Tree Support
+ *
+ * Authors:
+ * Tobias Waldekranz <tobias@xxxxxxxxxxxxxx>
+ */
+
+#include <linux/kernel.h>
+
+#include "br_private.h"
+
+DEFINE_STATIC_KEY_FALSE(br_mst_used);
+
+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);
+}
+
+void br_mst_set_state(struct net_bridge_port *p, u16 msti, u8 state)
+{
+ struct net_bridge_vlan_group *vg;
+ struct net_bridge_vlan *v;
+
+ vg = nbp_vlan_group(p);
+ if (!vg)
+ return;
+
+ list_for_each_entry(v, &vg->vlan_list, vlist) {
+ if (v->brvlan->msti != msti)
+ continue;
+
+ br_mst_vlan_set_state(p, v, state);
+ }
+}
+
+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, unsigned long val)
+{
+ struct net_bridge_vlan_group *vg;
+ struct net_bridge_port *p;
+
+ /* Mode may only be changed when there are no port VLANs. */
+ list_for_each_entry(p, &br->port_list, list) {
+ vg = nbp_vlan_group(p);
+
+ if (vg->num_vlans)
+ return -EBUSY;
+ }
+
+ if (val > 1)
+ return -EINVAL;
+
+ if (!!val == br_opt_get(br, BROPT_MST_ENABLED))
+ return 0;
+
+ if (val)
+ static_branch_enable(&br_mst_used);
+ else
+ static_branch_disable(&br_mst_used);
+
+ br_opt_toggle(br, BROPT_MST_ENABLED, !!val);
+ return 0;
+}
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 7d4432ca9a20..a17a0fe25a58 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -1163,6 +1163,7 @@ static const struct nla_policy br_policy[IFLA_BR_MAX + 1] = {
[IFLA_BR_MCAST_IGMP_VERSION] = { .type = NLA_U8 },
[IFLA_BR_MCAST_MLD_VERSION] = { .type = NLA_U8 },
[IFLA_BR_VLAN_STATS_PER_PORT] = { .type = NLA_U8 },
+ [IFLA_BR_MST_ENABLED] = { .type = NLA_U8 },
[IFLA_BR_MULTI_BOOLOPT] =
NLA_POLICY_EXACT_LEN(sizeof(struct br_boolopt_multi)),
};
@@ -1255,6 +1256,14 @@ static int br_changelink(struct net_device *brdev, struct nlattr *tb[],
if (err)
return err;
}
+
+ if (data[IFLA_BR_MST_ENABLED]) {
+ __u8 mst = nla_get_u8(data[IFLA_BR_MST_ENABLED]);
+
+ err = br_mst_set_enabled(br, mst);
+ if (err)
+ return err;
+ }
#endif

if (data[IFLA_BR_GROUP_FWD_MASK]) {
@@ -1475,6 +1484,7 @@ static size_t br_get_size(const struct net_device *brdev)
nla_total_size(sizeof(u16)) + /* IFLA_BR_VLAN_DEFAULT_PVID */
nla_total_size(sizeof(u8)) + /* IFLA_BR_VLAN_STATS_ENABLED */
nla_total_size(sizeof(u8)) + /* IFLA_BR_VLAN_STATS_PER_PORT */
+ nla_total_size(sizeof(u8)) + /* IFLA_BR_MST_ENABLED */
#endif
nla_total_size(sizeof(u16)) + /* IFLA_BR_GROUP_FWD_MASK */
nla_total_size(sizeof(struct ifla_bridge_id)) + /* IFLA_BR_ROOT_ID */
@@ -1572,7 +1582,9 @@ static int br_fill_info(struct sk_buff *skb, const struct net_device *brdev)
nla_put_u8(skb, IFLA_BR_VLAN_STATS_ENABLED,
br_opt_get(br, BROPT_VLAN_STATS_ENABLED)) ||
nla_put_u8(skb, IFLA_BR_VLAN_STATS_PER_PORT,
- br_opt_get(br, BROPT_VLAN_STATS_PER_PORT)))
+ br_opt_get(br, BROPT_VLAN_STATS_PER_PORT)) ||
+ nla_put_u8(skb, IFLA_BR_MST_ENABLED,
+ br_opt_get(br, BROPT_MST_ENABLED)))
return -EMSGSIZE;
#endif
#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 48bc61ebc211..af50ad036b06 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 +1769,28 @@ 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);
+}
+
+void br_mst_set_state(struct net_bridge_port *p, u16 msti, u8 state);
+void br_mst_vlan_init_state(struct net_bridge_vlan *v);
+int br_mst_set_enabled(struct net_bridge *br, unsigned long val);
+#else
+static inline bool br_mst_is_enabled(struct net_bridge *br)
+{
+ return false;
+}
+
+static inline void br_mst_set_state(struct net_bridge_port *p,
+ u16 msti, u8 state) {}
+#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..82a97a021a57 100644
--- a/net/bridge/br_stp.c
+++ b/net/bridge/br_stp.c
@@ -43,6 +43,9 @@ 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))
+ br_mst_set_state(p, 0, state);
+
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