net: bridge: add STP xstats

This adds rx_bpdu, tx_bpdu, rx_tcn, tx_tcn, transition_blk,
transition_fwd xstats counters to the bridge ports copied over via
netlink, providing useful information for STP.

Signed-off-by: Vivien Didelot <[e-mail]>
Acked-by: Nikolay Aleksandrov <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

include/uapi/linux/if_bridge.h

···
 	__u32 pad2;
 };
 
+struct bridge_stp_xstats {
+	__u64 transition_blk;
+	__u64 transition_fwd;
+	__u64 rx_bpdu;
+	__u64 tx_bpdu;
+	__u64 rx_tcn;
+	__u64 tx_tcn;
+};
+
 /* Bridge multicast database attributes
  * [MDBA_MDB] = {
  *     [MDBA_MDB_ENTRY] = {
···
 	BRIDGE_XSTATS_VLAN,
 	BRIDGE_XSTATS_MCAST,
 	BRIDGE_XSTATS_PAD,
+	BRIDGE_XSTATS_STP,
 	__BRIDGE_XSTATS_MAX
 };
 #define BRIDGE_XSTATS_MAX (__BRIDGE_XSTATS_MAX - 1)

net/bridge/br_netlink.c

···
 		br_multicast_get_stats(br, p, nla_data(nla));
 	}
 #endif
+
+	if (p) {
+		nla = nla_reserve_64bit(skb, BRIDGE_XSTATS_STP,
+					sizeof(p->stp_xstats),
+					BRIDGE_XSTATS_PAD);
+		if (!nla)
+			goto nla_put_failure;
+
+		spin_lock_bh(&br->lock);
+		memcpy(nla_data(nla), &p->stp_xstats, sizeof(p->stp_xstats));
+		spin_unlock_bh(&br->lock);
+	}
+
 	nla_nest_end(skb, nest);
 	*prividx = 0;
 

net/bridge/br_private.h

···
 #endif
 	u16				group_fwd_mask;
 	u16				backup_redirected_cnt;
+
+	struct bridge_stp_xstats	stp_xstats;
 };
 
 #define kobj_to_brport(obj)	container_of(obj, struct net_bridge_port, kobj)

net/bridge/br_stp.c

···
 		br_info(p->br, "port %u(%s) entered %s state\n",
 				(unsigned int) p->port_no, p->dev->name,
 				br_port_state_names[p->state]);
+
+	if (p->br->stp_enabled == BR_KERNEL_STP) {
+		switch (p->state) {
+		case BR_STATE_BLOCKING:
+			p->stp_xstats.transition_blk++;
+			break;
+		case BR_STATE_FORWARDING:
+			p->stp_xstats.transition_fwd++;
+			break;
+		}
+	}
 }
 
 /* called under bridge lock */
···
 	struct net_bridge *br;
 	int was_root;
 
+	p->stp_xstats.rx_bpdu++;
+
 	br = p->br;
 	was_root = br_is_root_bridge(br);
 
···
 /* called under bridge lock */
 void br_received_tcn_bpdu(struct net_bridge_port *p)
 {
+	p->stp_xstats.rx_tcn++;
+
 	if (br_is_designated_port(p)) {
 		br_info(p->br, "port %u(%s) received tcn bpdu\n",
 			(unsigned int) p->port_no, p->dev->name);

net/bridge/br_stp_bpdu.c

···
 	br_set_ticks(buf+33, bpdu->forward_delay);
 
 	br_send_bpdu(p, buf, 35);
+
+	p->stp_xstats.tx_bpdu++;
 }
 
 /* called under bridge lock */
···
 	buf[2] = 0;
 	buf[3] = BPDU_TYPE_TCN;
 	br_send_bpdu(p, buf, 4);
+
+	p->stp_xstats.tx_tcn++;
 }
 
 /*