Merge branch 'amt-fix-validation-and-synchronization-bugs'

Taehee Yoo says:

====================
amt: fix validation and synchronization bugs

There are some synchronization issues in the amt module.
Especially, an amt gateway doesn't well synchronize its own variables
and status(amt->status).
It tries to use a workqueue for handles in a single thread.
A global lock is also good, but it would occur complex locking complex.

In this patchset, only the gateway uses workqueue.
The reason why only gateway interface uses workqueue is that gateway
should manage its own states and variables a little bit statefully.
But relay doesn't need to manage tunnels statefully, stateless is okay.
So, relay side message handlers are okay to be called concurrently.
But it doesn't mean that no lock is needed.

Only amt multicast data message type will not be processed by the work
queue because It contains actual multicast data.
So, it should be processed immediately.

When any amt gateway events are triggered(sending discovery message by
delayed_work, sending request message by delayed_work and receiving
messages), it stores event and skb into the event queue(amt->events[16]).
Then, workqueue processes these events one by one.

The first patch is to use the work queue.

The second patch is to remove unnecessary lock due to a previous patch.

The third patch is to use READ_ONCE() in the amt module.
Even if the amt module uses a single thread, some variables (ready4,
ready6, amt->status) can be accessed concurrently.

The fourth patch is to add missing nonce generation logic when it sends a
new request message.

The fifth patch is to drop unexpected advertisement messages.
advertisement message should be received only after the gateway sends
a discovery message first.
So, the gateway should drop advertisement messages if it has never
sent a discovery message and it also should drop duplicate advertisement
messages.
Using nonce is good to distinguish whether a received message is an
expected message or not.

The sixth patch is to drop unexpected query messages.
This is the same behavior as the fourth patch.
Query messages should be received only after the gateway sends a request
message first.
The nonce variable is used to distinguish whether it is a reply to a
previous request message or not.
amt->ready4 and amt->ready6 are used to distinguish duplicate messages.

The seventh patch is to drop unexpected multicast data.
AMT gateway should not receive multicast data message type before
establish between gateway and relay.
In order to drop unexpected multicast data messages, it checks amt->status.

The last patch is to fix a locking problem on the relay side.
amt->nr_tunnels variable is protected by amt->lock.
But amt_request_handler() doesn't protect this variable.

v2:
 - Use local_bh_disable() instead of rcu_read_lock_bh() in
   amt_membership_query_handler.
 - Fix using uninitialized variables.
 - Fix unexpectedly start the event_wq after stopping.
 - Fix possible deadlock in amt_event_work().
 - Add a limit variable in amt_event_work() to prevent infinite working.
 - Rename amt_queue_events() to amt_queue_event().
====================

Link: https://lore.kernel.org/r/20220717160910.19156-1-ap420073@gmail.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/amt.c

@@ -577,14 +577,14 @@ static struct sk_buff *amt_build_igmp_gq(struct amt_dev *amt)
 	return skb;
 }
 
-static void __amt_update_gw_status(struct amt_dev *amt, enum amt_status status,
-				   bool validate)
+static void amt_update_gw_status(struct amt_dev *amt, enum amt_status status,
+				 bool validate)
 {
 	if (validate && amt->status >= status)
 		return;
 	netdev_dbg(amt->dev, "Update GW status %s -> %s",
 		   status_str[amt->status], status_str[status]);
-	amt->status = status;
+	WRITE_ONCE(amt->status, status);
 }
 
 static void __amt_update_relay_status(struct amt_tunnel_list *tunnel,
@@ -600,14 +600,6 @@ static void __amt_update_relay_status(struct amt_tunnel_list *tunnel,
 	tunnel->status = status;
 }
 
-static void amt_update_gw_status(struct amt_dev *amt, enum amt_status status,
-				 bool validate)
-{
-	spin_lock_bh(&amt->lock);
-	__amt_update_gw_status(amt, status, validate);
-	spin_unlock_bh(&amt->lock);
-}
-
 static void amt_update_relay_status(struct amt_tunnel_list *tunnel,
 				    enum amt_status status, bool validate)
 {
@@ -700,9 +692,7 @@ static void amt_send_discovery(struct amt_dev *amt)
 	if (unlikely(net_xmit_eval(err)))
 		amt->dev->stats.tx_errors++;
 
-	spin_lock_bh(&amt->lock);
-	__amt_update_gw_status(amt, AMT_STATUS_SENT_DISCOVERY, true);
-	spin_unlock_bh(&amt->lock);
+	amt_update_gw_status(amt, AMT_STATUS_SENT_DISCOVERY, true);
 out:
 	rcu_read_unlock();
 }
@@ -900,6 +890,28 @@ static void amt_send_mld_gq(struct amt_dev *amt, struct amt_tunnel_list *tunnel)
 }
 #endif
 
+static bool amt_queue_event(struct amt_dev *amt, enum amt_event event,
+			    struct sk_buff *skb)
+{
+	int index;
+
+	spin_lock_bh(&amt->lock);
+	if (amt->nr_events >= AMT_MAX_EVENTS) {
+		spin_unlock_bh(&amt->lock);
+		return 1;
+	}
+
+	index = (amt->event_idx + amt->nr_events) % AMT_MAX_EVENTS;
+	amt->events[index].event = event;
+	amt->events[index].skb = skb;
+	amt->nr_events++;
+	amt->event_idx %= AMT_MAX_EVENTS;
+	queue_work(amt_wq, &amt->event_wq);
+	spin_unlock_bh(&amt->lock);
+
+	return 0;
+}
+
 static void amt_secret_work(struct work_struct *work)
 {
 	struct amt_dev *amt = container_of(to_delayed_work(work),
@@ -913,58 +925,72 @@ static void amt_secret_work(struct work_struct *work)
 			 msecs_to_jiffies(AMT_SECRET_TIMEOUT));
 }
 
-static void amt_discovery_work(struct work_struct *work)
+static void amt_event_send_discovery(struct amt_dev *amt)
 {
-	struct amt_dev *amt = container_of(to_delayed_work(work),
-					   struct amt_dev,
-					   discovery_wq);
-
-	spin_lock_bh(&amt->lock);
 	if (amt->status > AMT_STATUS_SENT_DISCOVERY)
 		goto out;
 	get_random_bytes(&amt->nonce, sizeof(__be32));
-	spin_unlock_bh(&amt->lock);
 
 	amt_send_discovery(amt);
-	spin_lock_bh(&amt->lock);
 out:
 	mod_delayed_work(amt_wq, &amt->discovery_wq,
 			 msecs_to_jiffies(AMT_DISCOVERY_TIMEOUT));
-	spin_unlock_bh(&amt->lock);
 }
 
-static void amt_req_work(struct work_struct *work)
+static void amt_discovery_work(struct work_struct *work)
 {
 	struct amt_dev *amt = container_of(to_delayed_work(work),
 					   struct amt_dev,
-					   req_wq);
+					   discovery_wq);
+
+	if (amt_queue_event(amt, AMT_EVENT_SEND_DISCOVERY, NULL))
+		mod_delayed_work(amt_wq, &amt->discovery_wq,
+				 msecs_to_jiffies(AMT_DISCOVERY_TIMEOUT));
+}
+
+static void amt_event_send_request(struct amt_dev *amt)
+{
 	u32 exp;
 
-	spin_lock_bh(&amt->lock);
 	if (amt->status < AMT_STATUS_RECEIVED_ADVERTISEMENT)
 		goto out;
 
 	if (amt->req_cnt > AMT_MAX_REQ_COUNT) {
 		netdev_dbg(amt->dev, "Gateway is not ready");
 		amt->qi = AMT_INIT_REQ_TIMEOUT;
-		amt->ready4 = false;
-		amt->ready6 = false;
+		WRITE_ONCE(amt->ready4, false);
+		WRITE_ONCE(amt->ready6, false);
 		amt->remote_ip = 0;
-		__amt_update_gw_status(amt, AMT_STATUS_INIT, false);
+		amt_update_gw_status(amt, AMT_STATUS_INIT, false);
 		amt->req_cnt = 0;
+		amt->nonce = 0;
 		goto out;
 	}
-	spin_unlock_bh(&amt->lock);
+
+	if (!amt->req_cnt) {
+		WRITE_ONCE(amt->ready4, false);
+		WRITE_ONCE(amt->ready6, false);
+		get_random_bytes(&amt->nonce, sizeof(__be32));
+	}
 
 	amt_send_request(amt, false);
 	amt_send_request(amt, true);
-	spin_lock_bh(&amt->lock);
-	__amt_update_gw_status(amt, AMT_STATUS_SENT_REQUEST, true);
+	amt_update_gw_status(amt, AMT_STATUS_SENT_REQUEST, true);
 	amt->req_cnt++;
 out:
 	exp = min_t(u32, (1 * (1 << amt->req_cnt)), AMT_MAX_REQ_TIMEOUT);
 	mod_delayed_work(amt_wq, &amt->req_wq, msecs_to_jiffies(exp * 1000));
-	spin_unlock_bh(&amt->lock);
+}
+
+static void amt_req_work(struct work_struct *work)
+{
+	struct amt_dev *amt = container_of(to_delayed_work(work),
+					   struct amt_dev,
+					   req_wq);
+
+	if (amt_queue_event(amt, AMT_EVENT_SEND_REQUEST, NULL))
+		mod_delayed_work(amt_wq, &amt->req_wq,
+				 msecs_to_jiffies(100));
 }
 
 static bool amt_send_membership_update(struct amt_dev *amt,
@@ -1220,7 +1246,8 @@ static netdev_tx_t amt_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 		/* Gateway only passes IGMP/MLD packets */
 		if (!report)
 			goto free;
-		if ((!v6 && !amt->ready4) || (v6 && !amt->ready6))
+		if ((!v6 && !READ_ONCE(amt->ready4)) ||
+		    (v6 && !READ_ONCE(amt->ready6)))
 			goto free;
 		if (amt_send_membership_update(amt, skb,  v6))
 			goto free;
@@ -2236,6 +2263,10 @@ static bool amt_advertisement_handler(struct amt_dev *amt, struct sk_buff *skb)
 	    ipv4_is_zeronet(amta->ip4))
 		return true;
 
+	if (amt->status != AMT_STATUS_SENT_DISCOVERY ||
+	    amt->nonce != amta->nonce)
+		return true;
+
 	amt->remote_ip = amta->ip4;
 	netdev_dbg(amt->dev, "advertised remote ip = %pI4\n", &amt->remote_ip);
 	mod_delayed_work(amt_wq, &amt->req_wq, 0);
@@ -2251,6 +2282,9 @@ static bool amt_multicast_data_handler(struct amt_dev *amt, struct sk_buff *skb)
 	struct ethhdr *eth;
 	struct iphdr *iph;
 
+	if (READ_ONCE(amt->status) != AMT_STATUS_SENT_UPDATE)
+		return true;
+
 	hdr_size = sizeof(*amtmd) + sizeof(struct udphdr);
 	if (!pskb_may_pull(skb, hdr_size))
 		return true;
@@ -2325,6 +2359,9 @@ static bool amt_membership_query_handler(struct amt_dev *amt,
 	if (amtmq->reserved || amtmq->version)
 		return true;
 
+	if (amtmq->nonce != amt->nonce)
+		return true;
+
 	hdr_size -= sizeof(*eth);
 	if (iptunnel_pull_header(skb, hdr_size, htons(ETH_P_TEB), false))
 		return true;
@@ -2339,6 +2376,9 @@ static bool amt_membership_query_handler(struct amt_dev *amt,
 
 	iph = ip_hdr(skb);
 	if (iph->version == 4) {
+		if (READ_ONCE(amt->ready4))
+			return true;
+
 		if (!pskb_may_pull(skb, sizeof(*iph) + AMT_IPHDR_OPTS +
 				   sizeof(*ihv3)))
 			return true;
@@ -2349,12 +2389,10 @@ static bool amt_membership_query_handler(struct amt_dev *amt,
 		ihv3 = skb_pull(skb, sizeof(*iph) + AMT_IPHDR_OPTS);
 		skb_reset_transport_header(skb);
 		skb_push(skb, sizeof(*iph) + AMT_IPHDR_OPTS);
-		spin_lock_bh(&amt->lock);
-		amt->ready4 = true;
+		WRITE_ONCE(amt->ready4, true);
 		amt->mac = amtmq->response_mac;
 		amt->req_cnt = 0;
 		amt->qi = ihv3->qqic;
-		spin_unlock_bh(&amt->lock);
 		skb->protocol = htons(ETH_P_IP);
 		eth->h_proto = htons(ETH_P_IP);
 		ip_eth_mc_map(iph->daddr, eth->h_dest);
@@ -2363,6 +2401,9 @@ static bool amt_membership_query_handler(struct amt_dev *amt,
 		struct mld2_query *mld2q;
 		struct ipv6hdr *ip6h;
 
+		if (READ_ONCE(amt->ready6))
+			return true;
+
 		if (!pskb_may_pull(skb, sizeof(*ip6h) + AMT_IP6HDR_OPTS +
 				   sizeof(*mld2q)))
 			return true;
@@ -2374,12 +2415,10 @@ static bool amt_membership_query_handler(struct amt_dev *amt,
 		mld2q = skb_pull(skb, sizeof(*ip6h) + AMT_IP6HDR_OPTS);
 		skb_reset_transport_header(skb);
 		skb_push(skb, sizeof(*ip6h) + AMT_IP6HDR_OPTS);
-		spin_lock_bh(&amt->lock);
-		amt->ready6 = true;
+		WRITE_ONCE(amt->ready6, true);
 		amt->mac = amtmq->response_mac;
 		amt->req_cnt = 0;
 		amt->qi = mld2q->mld2q_qqic;
-		spin_unlock_bh(&amt->lock);
 		skb->protocol = htons(ETH_P_IPV6);
 		eth->h_proto = htons(ETH_P_IPV6);
 		ipv6_eth_mc_map(&ip6h->daddr, eth->h_dest);
@@ -2392,12 +2431,14 @@ static bool amt_membership_query_handler(struct amt_dev *amt,
 	skb->pkt_type = PACKET_MULTICAST;
 	skb->ip_summed = CHECKSUM_NONE;
 	len = skb->len;
+	local_bh_disable();
 	if (__netif_rx(skb) == NET_RX_SUCCESS) {
 		amt_update_gw_status(amt, AMT_STATUS_RECEIVED_QUERY, true);
 		dev_sw_netstats_rx_add(amt->dev, len);
 	} else {
 		amt->dev->stats.rx_dropped++;
 	}
+	local_bh_enable();
 
 	return false;
 }
@@ -2638,7 +2679,9 @@ static bool amt_request_handler(struct amt_dev *amt, struct sk_buff *skb)
 		if (tunnel->ip4 == iph->saddr)
 			goto send;
 
+	spin_lock_bh(&amt->lock);
 	if (amt->nr_tunnels >= amt->max_tunnels) {
+		spin_unlock_bh(&amt->lock);
 		icmp_ndo_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, 0);
 		return true;
 	}
@@ -2646,8 +2689,10 @@ static bool amt_request_handler(struct amt_dev *amt, struct sk_buff *skb)
 	tunnel = kzalloc(sizeof(*tunnel) +
 			 (sizeof(struct hlist_head) * amt->hash_buckets),
 			 GFP_ATOMIC);
-	if (!tunnel)
+	if (!tunnel) {
+		spin_unlock_bh(&amt->lock);
 		return true;
+	}
 
 	tunnel->source_port = udph->source;
 	tunnel->ip4 = iph->saddr;
@@ -2660,10 +2705,9 @@ static bool amt_request_handler(struct amt_dev *amt, struct sk_buff *skb)
 
 	INIT_DELAYED_WORK(&tunnel->gc_wq, amt_tunnel_expire);
 
-	spin_lock_bh(&amt->lock);
 	list_add_tail_rcu(&tunnel->list, &amt->tunnel_list);
 	tunnel->key = amt->key;
-	amt_update_relay_status(tunnel, AMT_STATUS_RECEIVED_REQUEST, true);
+	__amt_update_relay_status(tunnel, AMT_STATUS_RECEIVED_REQUEST, true);
 	amt->nr_tunnels++;
 	mod_delayed_work(amt_wq, &tunnel->gc_wq,
 			 msecs_to_jiffies(amt_gmi(amt)));
@@ -2688,6 +2732,38 @@ static bool amt_request_handler(struct amt_dev *amt, struct sk_buff *skb)
 	return false;
 }
 
+static void amt_gw_rcv(struct amt_dev *amt, struct sk_buff *skb)
+{
+	int type = amt_parse_type(skb);
+	int err = 1;
+
+	if (type == -1)
+		goto drop;
+
+	if (amt->mode == AMT_MODE_GATEWAY) {
+		switch (type) {
+		case AMT_MSG_ADVERTISEMENT:
+			err = amt_advertisement_handler(amt, skb);
+			break;
+		case AMT_MSG_MEMBERSHIP_QUERY:
+			err = amt_membership_query_handler(amt, skb);
+			if (!err)
+				return;
+			break;
+		default:
+			netdev_dbg(amt->dev, "Invalid type of Gateway\n");
+			break;
+		}
+	}
+drop:
+	if (err) {
+		amt->dev->stats.rx_dropped++;
+		kfree_skb(skb);
+	} else {
+		consume_skb(skb);
+	}
+}
+
 static int amt_rcv(struct sock *sk, struct sk_buff *skb)
 {
 	struct amt_dev *amt;
@@ -2719,8 +2795,12 @@ static int amt_rcv(struct sock *sk, struct sk_buff *skb)
 				err = true;
 				goto drop;
 			}
-			err = amt_advertisement_handler(amt, skb);
-			break;
+			if (amt_queue_event(amt, AMT_EVENT_RECEIVE, skb)) {
+				netdev_dbg(amt->dev, "AMT Event queue full\n");
+				err = true;
+				goto drop;
+			}
+			goto out;
 		case AMT_MSG_MULTICAST_DATA:
 			if (iph->saddr != amt->remote_ip) {
 				netdev_dbg(amt->dev, "Invalid Relay IP\n");
@@ -2738,11 +2818,12 @@ static int amt_rcv(struct sock *sk, struct sk_buff *skb)
 				err = true;
 				goto drop;
 			}
-			err = amt_membership_query_handler(amt, skb);
-			if (err)
+			if (amt_queue_event(amt, AMT_EVENT_RECEIVE, skb)) {
+				netdev_dbg(amt->dev, "AMT Event queue full\n");
+				err = true;
 				goto drop;
-			else
-				goto out;
+			}
+			goto out;
 		default:
 			err = true;
 			netdev_dbg(amt->dev, "Invalid type of Gateway\n");
@@ -2780,6 +2861,46 @@ static int amt_rcv(struct sock *sk, struct sk_buff *skb)
 	return 0;
 }
 
+static void amt_event_work(struct work_struct *work)
+{
+	struct amt_dev *amt = container_of(work, struct amt_dev, event_wq);
+	struct sk_buff *skb;
+	u8 event;
+	int i;
+
+	for (i = 0; i < AMT_MAX_EVENTS; i++) {
+		spin_lock_bh(&amt->lock);
+		if (amt->nr_events == 0) {
+			spin_unlock_bh(&amt->lock);
+			return;
+		}
+		event = amt->events[amt->event_idx].event;
+		skb = amt->events[amt->event_idx].skb;
+		amt->events[amt->event_idx].event = AMT_EVENT_NONE;
+		amt->events[amt->event_idx].skb = NULL;
+		amt->nr_events--;
+		amt->event_idx++;
+		amt->event_idx %= AMT_MAX_EVENTS;
+		spin_unlock_bh(&amt->lock);
+
+		switch (event) {
+		case AMT_EVENT_RECEIVE:
+			amt_gw_rcv(amt, skb);
+			break;
+		case AMT_EVENT_SEND_DISCOVERY:
+			amt_event_send_discovery(amt);
+			break;
+		case AMT_EVENT_SEND_REQUEST:
+			amt_event_send_request(amt);
+			break;
+		default:
+			if (skb)
+				kfree_skb(skb);
+			break;
+		}
+	}
+}
+
 static int amt_err_lookup(struct sock *sk, struct sk_buff *skb)
 {
 	struct amt_dev *amt;
@@ -2804,7 +2925,7 @@ static int amt_err_lookup(struct sock *sk, struct sk_buff *skb)
 		break;
 	case AMT_MSG_REQUEST:
 	case AMT_MSG_MEMBERSHIP_UPDATE:
-		if (amt->status >= AMT_STATUS_RECEIVED_ADVERTISEMENT)
+		if (READ_ONCE(amt->status) >= AMT_STATUS_RECEIVED_ADVERTISEMENT)
 			mod_delayed_work(amt_wq, &amt->req_wq, 0);
 		break;
 	default:
@@ -2867,6 +2988,8 @@ static int amt_dev_open(struct net_device *dev)
 
 	amt->ready4 = false;
 	amt->ready6 = false;
+	amt->event_idx = 0;
+	amt->nr_events = 0;
 
 	err = amt_socket_create(amt);
 	if (err)
@@ -2874,6 +2997,7 @@ static int amt_dev_open(struct net_device *dev)
 
 	amt->req_cnt = 0;
 	amt->remote_ip = 0;
+	amt->nonce = 0;
 	get_random_bytes(&amt->key, sizeof(siphash_key_t));
 
 	amt->status = AMT_STATUS_INIT;
@@ -2892,6 +3016,8 @@ static int amt_dev_stop(struct net_device *dev)
 	struct amt_dev *amt = netdev_priv(dev);
 	struct amt_tunnel_list *tunnel, *tmp;
 	struct socket *sock;
+	struct sk_buff *skb;
+	int i;
 
 	cancel_delayed_work_sync(&amt->req_wq);
 	cancel_delayed_work_sync(&amt->discovery_wq);
@@ -2904,6 +3030,15 @@ static int amt_dev_stop(struct net_device *dev)
 	if (sock)
 		udp_tunnel_sock_release(sock);
 
+	cancel_work_sync(&amt->event_wq);
+	for (i = 0; i < AMT_MAX_EVENTS; i++) {
+		skb = amt->events[i].skb;
+		if (skb)
+			kfree_skb(skb);
+		amt->events[i].event = AMT_EVENT_NONE;
+		amt->events[i].skb = NULL;
+	}
+
 	amt->ready4 = false;
 	amt->ready6 = false;
 	amt->req_cnt = 0;
@@ -3146,8 +3281,8 @@ static int amt_newlink(struct net *net, struct net_device *dev,
 	INIT_DELAYED_WORK(&amt->discovery_wq, amt_discovery_work);
 	INIT_DELAYED_WORK(&amt->req_wq, amt_req_work);
 	INIT_DELAYED_WORK(&amt->secret_wq, amt_secret_work);
+	INIT_WORK(&amt->event_wq, amt_event_work);
 	INIT_LIST_HEAD(&amt->tunnel_list);
-
 	return 0;
 err:
 	dev_put(amt->stream_dev);
@@ -3280,7 +3415,7 @@ static int __init amt_init(void)
 	if (err < 0)
 		goto unregister_notifier;
 
-	amt_wq = alloc_workqueue("amt", WQ_UNBOUND, 1);
+	amt_wq = alloc_workqueue("amt", WQ_UNBOUND, 0);
 	if (!amt_wq) {
 		err = -ENOMEM;
 		goto rtnl_unregister;

include/net/amt.h

@@ -78,6 +78,15 @@ enum amt_status {
 
 #define AMT_STATUS_MAX (__AMT_STATUS_MAX - 1)
 
+/* Gateway events only */
+enum amt_event {
+	AMT_EVENT_NONE,
+	AMT_EVENT_RECEIVE,
+	AMT_EVENT_SEND_DISCOVERY,
+	AMT_EVENT_SEND_REQUEST,
+	__AMT_EVENT_MAX,
+};
+
 struct amt_header {
 #if defined(__LITTLE_ENDIAN_BITFIELD)
 	u8 type:4,
@@ -292,6 +301,12 @@ struct amt_group_node {
 	struct hlist_head	sources[];
 };
 
+#define AMT_MAX_EVENTS	16
+struct amt_events {
+	enum amt_event event;
+	struct sk_buff *skb;
+};
+
 struct amt_dev {
 	struct net_device       *dev;
 	struct net_device       *stream_dev;
@@ -308,6 +323,7 @@ struct amt_dev {
 	struct delayed_work     req_wq;
 	/* Protected by RTNL */
 	struct delayed_work     secret_wq;
+	struct work_struct	event_wq;
 	/* AMT status */
 	enum amt_status		status;
 	/* Generated key */
@@ -345,6 +361,10 @@ struct amt_dev {
 	/* Used only in gateway mode */
 	u64			mac:48,
 				reserved:16;
+	/* AMT gateway side message handler queue */
+	struct amt_events	events[AMT_MAX_EVENTS];
+	u8			event_idx;
+	u8			nr_events;
 };
 
 #define AMT_TOS			0xc0