bridge: netlink: export root port

Add IFLA_BR_ROOT_PORT and export it via netlink.
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/if_link.h

@@ -235,6 +235,7 @@ enum {
 	IFLA_BR_GROUP_FWD_MASK,
 	IFLA_BR_ROOT_ID,
 	IFLA_BR_BRIDGE_ID,
+	IFLA_BR_ROOT_PORT,
 	__IFLA_BR_MAX,
 };
 

net/bridge/br_netlink.c

@@ -856,6 +856,7 @@ static size_t br_get_size(const struct net_device *brdev)
 	       nla_total_size(sizeof(u16)) +    /* IFLA_BR_GROUP_FWD_MASK */
 	       nla_total_size(sizeof(struct ifla_bridge_id)) +   /* IFLA_BR_ROOT_ID */
 	       nla_total_size(sizeof(struct ifla_bridge_id)) +   /* IFLA_BR_BRIDGE_ID */
+	       nla_total_size(sizeof(u16)) +    /* IFLA_BR_ROOT_PORT */
 	       0;
 }
 
@@ -888,7 +889,8 @@ static int br_fill_info(struct sk_buff *skb, const struct net_device *brdev)
 	    nla_put_u8(skb, IFLA_BR_VLAN_FILTERING, vlan_enabled) ||
 	    nla_put_u16(skb, IFLA_BR_GROUP_FWD_MASK, group_fwd_mask) ||
 	    nla_put(skb, IFLA_BR_ROOT_ID, sizeof(root_id), &root_id) ||
-	    nla_put(skb, IFLA_BR_BRIDGE_ID, sizeof(bridge_id), &bridge_id))
+	    nla_put(skb, IFLA_BR_BRIDGE_ID, sizeof(bridge_id), &bridge_id) ||
+	    nla_put_u16(skb, IFLA_BR_ROOT_PORT, br->root_port))
 		return -EMSGSIZE;
 
 #ifdef CONFIG_BRIDGE_VLAN_FILTERING