5 files changed, 133 insertions, 2 deletions

diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
index 9019f326fe81..5372e2042adf 100644
--- a/net/bridge/br_forward.c
+++ b/net/bridge/br_forward.c
@@ -142,7 +142,20 @@ static int deliver_clone(const struct net_bridge_port *prev,
 void br_forward(const struct net_bridge_port *to,
 		struct sk_buff *skb, bool local_rcv, bool local_orig)
 {
-	if (to && should_deliver(to, skb)) {
+	if (unlikely(!to))
+		goto out;
+
+	/* redirect to backup link if the destination port is down */
+	if (rcu_access_pointer(to->backup_port) && !netif_carrier_ok(to->dev)) {
+		struct net_bridge_port *backup_port;
+
+		backup_port = rcu_dereference(to->backup_port);
+		if (unlikely(!backup_port))
+			goto out;
+		to = backup_port;
+	}
+
+	if (should_deliver(to, skb)) {
 		if (local_rcv)
 			deliver_clone(to, skb, local_orig);
 		else
@@ -150,6 +163,7 @@ void br_forward(const struct net_bridge_port *to,
 		return;
 	}
 
+out:
 	if (!local_rcv)
 		kfree_skb(skb);
 }
diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index e7c8d55212aa..0363f1bdc401 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -170,6 +170,58 @@ void br_manage_promisc(struct net_bridge *br)
 	}
 }
 
+int nbp_backup_change(struct net_bridge_port *p,
+		      struct net_device *backup_dev)
+{
+	struct net_bridge_port *old_backup = rtnl_dereference(p->backup_port);
+	struct net_bridge_port *backup_p = NULL;
+
+	ASSERT_RTNL();
+
+	if (backup_dev) {
+		if (!br_port_exists(backup_dev))
+			return -ENOENT;
+
+		backup_p = br_port_get_rtnl(backup_dev);
+		if (backup_p->br != p->br)
+			return -EINVAL;
+	}
+
+	if (p == backup_p)
+		return -EINVAL;
+
+	if (old_backup == backup_p)
+		return 0;
+
+	/* if the backup link is already set, clear it */
+	if (old_backup)
+		old_backup->backup_redirected_cnt--;
+
+	if (backup_p)
+		backup_p->backup_redirected_cnt++;
+	rcu_assign_pointer(p->backup_port, backup_p);
+
+	return 0;
+}
+
+static void nbp_backup_clear(struct net_bridge_port *p)
+{
+	nbp_backup_change(p, NULL);
+	if (p->backup_redirected_cnt) {
+		struct net_bridge_port *cur_p;
+
+		list_for_each_entry(cur_p, &p->br->port_list, list) {
+			struct net_bridge_port *backup_p;
+
+			backup_p = rtnl_dereference(cur_p->backup_port);
+			if (backup_p == p)
+				nbp_backup_change(cur_p, NULL);
+		}
+	}
+
+	WARN_ON(rcu_access_pointer(p->backup_port) || p->backup_redirected_cnt);
+}
+
 static void nbp_update_port_count(struct net_bridge *br)
 {
 	struct net_bridge_port *p;
@@ -295,6 +347,7 @@ static void del_nbp(struct net_bridge_port *p)
 	nbp_vlan_flush(p);
 	br_fdb_delete_by_port(br, p, 0, 1);
 	switchdev_deferred_process();
+	nbp_backup_clear(p);
 
 	nbp_update_port_count(br);
 
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 9f5eb05b0373..ec2b58a09f76 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -169,13 +169,15 @@ static inline size_t br_nlmsg_size(struct net_device *dev, u32 filter_mask)
 		+ nla_total_size(1) /* IFLA_OPERSTATE */
 		+ nla_total_size(br_port_info_size()) /* IFLA_PROTINFO */
 		+ nla_total_size(br_get_link_af_size_filtered(dev,
-				 filter_mask)); /* IFLA_AF_SPEC */
+				 filter_mask)) /* IFLA_AF_SPEC */
+		+ nla_total_size(4); /* IFLA_BRPORT_BACKUP_PORT */
 }
 
 static int br_port_fill_attrs(struct sk_buff *skb,
 			      const struct net_bridge_port *p)
 {
 	u8 mode = !!(p->flags & BR_HAIRPIN_MODE);
+	struct net_bridge_port *backup_p;
 	u64 timerval;
 
 	if (nla_put_u8(skb, IFLA_BRPORT_STATE, p->state) ||
@@ -237,6 +239,14 @@ static int br_port_fill_attrs(struct sk_buff *skb,
 		return -EMSGSIZE;
 #endif
 
+	/* we might be called only with br->lock */
+	rcu_read_lock();
+	backup_p = rcu_dereference(p->backup_port);
+	if (backup_p)
+		nla_put_u32(skb, IFLA_BRPORT_BACKUP_PORT,
+			    backup_p->dev->ifindex);
+	rcu_read_unlock();
+
 	return 0;
 }
 
@@ -663,6 +673,7 @@ static const struct nla_policy br_port_policy[IFLA_BRPORT_MAX + 1] = {
 	[IFLA_BRPORT_GROUP_FWD_MASK] = { .type = NLA_U16 },
 	[IFLA_BRPORT_NEIGH_SUPPRESS] = { .type = NLA_U8 },
 	[IFLA_BRPORT_ISOLATED]	= { .type = NLA_U8 },
+	[IFLA_BRPORT_BACKUP_PORT] = { .type = NLA_U32 },
 };
 
 /* Change the state of the port and notify spanning tree */
@@ -817,6 +828,23 @@ static int br_setport(struct net_bridge_port *p, struct nlattr *tb[])
 	if (err)
 		return err;
 
+	if (tb[IFLA_BRPORT_BACKUP_PORT]) {
+		struct net_device *backup_dev = NULL;
+		u32 backup_ifindex;
+
+		backup_ifindex = nla_get_u32(tb[IFLA_BRPORT_BACKUP_PORT]);
+		if (backup_ifindex) {
+			backup_dev = __dev_get_by_index(dev_net(p->dev),
+							backup_ifindex);
+			if (!backup_dev)
+				return -ENOENT;
+		}
+
+		err = nbp_backup_change(p, backup_dev);
+		if (err)
+			return err;
+	}
+
 	br_port_flags_change(p, old_flags ^ p->flags);
 	return 0;
 }
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index cf0005d2a4d0..11ed2029985f 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -237,6 +237,7 @@ struct net_bridge_port {
 #ifdef CONFIG_BRIDGE_VLAN_FILTERING
 	struct net_bridge_vlan_group	__rcu *vlgrp;
 #endif
+	struct net_bridge_port		__rcu *backup_port;
 
 	/* STP */
 	u8				priority;
@@ -281,6 +282,7 @@ struct net_bridge_port {
 	int				offload_fwd_mark;
 #endif
 	u16				group_fwd_mask;
+	u16				backup_redirected_cnt;
 };
 
 #define kobj_to_brport(obj)	container_of(obj, struct net_bridge_port, kobj)
@@ -597,6 +599,7 @@ netdev_features_t br_features_recompute(struct net_bridge *br,
 					netdev_features_t features);
 void br_port_flags_change(struct net_bridge_port *port, unsigned long mask);
 void br_manage_promisc(struct net_bridge *br);
+int nbp_backup_change(struct net_bridge_port *p, struct net_device *backup_dev);
 
 /* br_input.c */
 int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb);
diff --git a/net/bridge/br_sysfs_if.c b/net/bridge/br_sysfs_if.c
index 4ac940067754..7c87a2fe5248 100644
--- a/net/bridge/br_sysfs_if.c
+++ b/net/bridge/br_sysfs_if.c
@@ -191,6 +191,38 @@ static int store_group_fwd_mask(struct net_bridge_port *p,
 static BRPORT_ATTR(group_fwd_mask, 0644, show_group_fwd_mask,
 		   store_group_fwd_mask);
 
+static ssize_t show_backup_port(struct net_bridge_port *p, char *buf)
+{
+	struct net_bridge_port *backup_p;
+	int ret = 0;
+
+	rcu_read_lock();
+	backup_p = rcu_dereference(p->backup_port);
+	if (backup_p)
+		ret = sprintf(buf, "%s\n", backup_p->dev->name);
+	rcu_read_unlock();
+
+	return ret;
+}
+
+static int store_backup_port(struct net_bridge_port *p, char *buf)
+{
+	struct net_device *backup_dev = NULL;
+	char *nl = strchr(buf, '\n');
+
+	if (nl)
+		*nl = '\0';
+
+	if (strlen(buf) > 0) {
+		backup_dev = __dev_get_by_name(dev_net(p->dev), buf);
+		if (!backup_dev)
+			return -ENOENT;
+	}
+
+	return nbp_backup_change(p, backup_dev);
+}
+static BRPORT_ATTR_RAW(backup_port, 0644, show_backup_port, store_backup_port);
+
 BRPORT_ATTR_FLAG(hairpin_mode, BR_HAIRPIN_MODE);
 BRPORT_ATTR_FLAG(bpdu_guard, BR_BPDU_GUARD);
 BRPORT_ATTR_FLAG(root_block, BR_ROOT_BLOCK);
@@ -254,6 +286,7 @@ static const struct brport_attribute *brport_attrs[] = {
 	&brport_attr_group_fwd_mask,
 	&brport_attr_neigh_suppress,
 	&brport_attr_isolated,
+	&brport_attr_backup_port,
 	NULL
 };