bridge: implement BPDU blocking

This is Linux bridge implementation of STP protection
(Cisco BPDU guard/Juniper BPDU block). BPDU block disables
the bridge port if a STP BPDU packet is received.

Why would you want to do this?
If running Spanning Tree on bridge, hostile devices on the network
may send BPDU and cause network failure. Enabling bpdu block
will detect and stop this.

How to recover the port?
The port will be restarted if link is brought down, or
removed and reattached.  For example:
 # ip li set dev eth0 down; ip li set dev eth0 up

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 15 insertions, 1 deletions

diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 0188a2f706c4..c331e28c7880 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -26,6 +26,7 @@ static inline size_t br_port_info_size(void)
                 + nla_total_size(2)     /* IFLA_BRPORT_PRIORITY */
                 + nla_total_size(4)     /* IFLA_BRPORT_COST */
                 + nla_total_size(1)     /* IFLA_BRPORT_MODE */
+                + nla_total_size(1)     /* IFLA_BRPORT_GUARD */
                 + 0;
 }
 
@@ -49,7 +50,8 @@ static int br_port_fill_attrs(struct sk_buff *skb,
         if (nla_put_u8(skb, IFLA_BRPORT_STATE, p->state) ||
             nla_put_u16(skb, IFLA_BRPORT_PRIORITY, p->priority) ||
             nla_put_u32(skb, IFLA_BRPORT_COST, p->path_cost) ||
-            nla_put_u8(skb, IFLA_BRPORT_MODE, mode))
+            nla_put_u8(skb, IFLA_BRPORT_MODE, mode) ||
+            nla_put_u8(skb, IFLA_BRPORT_GUARD, !!(p->flags & BR_BPDU_GUARD)))
                 return -EMSGSIZE;
 
         return 0;
@@ -162,6 +164,7 @@ static const struct nla_policy ifla_brport_policy[IFLA_BRPORT_MAX + 1] = {
         [IFLA_BRPORT_COST]      = { .type = NLA_U32 },
         [IFLA_BRPORT_PRIORITY]  = { .type = NLA_U16 },
         [IFLA_BRPORT_MODE]      = { .type = NLA_U8 },
+        [IFLA_BRPORT_GUARD]     = { .type = NLA_U8 },
 };
 
 /* Change the state of the port and notify spanning tree */
@@ -203,6 +206,7 @@ static int br_setport(struct net_bridge_port *p, struct nlattr *tb[])
         int err;
 
         br_set_port_flag(p, tb, IFLA_BRPORT_MODE, BR_HAIRPIN_MODE);
+        br_set_port_flag(p, tb, IFLA_BRPORT_GUARD, BR_BPDU_GUARD);
 
         if (tb[IFLA_BRPORT_COST]) {
                 err = br_stp_set_path_cost(p, nla_get_u32(tb[IFLA_BRPORT_COST]));
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 22111ffd68df..c92b0804ff2d 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -135,6 +135,7 @@ struct net_bridge_port
 
         unsigned long                   flags;
 #define BR_HAIRPIN_MODE         0x00000001
+#define BR_BPDU_GUARD           0x00000002
 
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
         u32                             multicast_startup_queries_sent;
diff --git a/net/bridge/br_stp_bpdu.c b/net/bridge/br_stp_bpdu.c
index fd30a6022dea..7f884e3fb955 100644
--- a/net/bridge/br_stp_bpdu.c
+++ b/net/bridge/br_stp_bpdu.c
@@ -170,6 +170,13 @@ void br_stp_rcv(const struct stp_proto *proto, struct sk_buff *skb,
         if (!ether_addr_equal(dest, br->group_addr))
                 goto out;
 
+        if (p->flags & BR_BPDU_GUARD) {
+                br_notice(br, "BPDU received on blocked port %u(%s)\n",
+                          (unsigned int) p->port_no, p->dev->name);
+                br_stp_disable_port(p);
+                goto out;
+        }
+
         buf = skb_pull(skb, 3);
 
         if (buf[0] == BPDU_TYPE_CONFIG) {
diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c
index f26173d33d8d..d1dfa4026185 100644
--- a/net/bridge/br_sysfs_if.c
+++ b/net/bridge/br_sysfs_if.c
@@ -156,6 +156,7 @@ static int store_flush(struct net_bridge_port *p, unsigned long v)
 static BRPORT_ATTR(flush, S_IWUSR, NULL, store_flush);
 
 BRPORT_ATTR_FLAG(hairpin_mode, BR_HAIRPIN_MODE);
+BRPORT_ATTR_FLAG(bpdu_guard, BR_BPDU_GUARD);
 
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 static ssize_t show_multicast_router(struct net_bridge_port *p, char *buf)
@@ -189,6 +190,7 @@ static const struct brport_attribute *brport_attrs[] = {
         &brport_attr_hold_timer,
         &brport_attr_flush,
         &brport_attr_hairpin_mode,
+        &brport_attr_bpdu_guard,
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
         &brport_attr_multicast_router,
 #endif