Merge branch 'tipc-next'

Jon Maloy says:

====================
tipc: improve broadcast implementation

The TIPC broadcast link implementation is currently complex and hard to
follow. It also incurs some amount of code and structure duplication,
something that can be reduced significantly with a little effort.

This commit series introduces a number of improvements which address
both the locking structure, the code/structure duplication issue, and
the overall readbility of the code.

The series consists of three main parts:

1-7: Adaptation to the new link structure, and preparation for the next
     step. In particular, we want the broadcast transmission link to
     have a life cycle that is longer than any of its potential (unicast
     and broadcast receive links) users. This eliminates the need to
     always test for the presence of this link before accessing it.

8-10: This is what is really new in this series. Commit #9 is by far
      the largest and most important one, because it moves most of
      the broadcast functionality into link.c, partially reusing the
      fields and functionality of the unicast link. The removal of
      the "node_map" infrastructure in commit #10 is also an important
      achievement.

11-16: Some improvements leveraging the changes made in the previous
       commits.

The series needs commit 53387c4e22ac ("tipc: extend broadcast link window size")
and commit e53567948f82 ("tipc: conditionally expand buffer headroom over udp tunnel")
which are both present in 'net' but not yet in 'net-next', to apply cleanly.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 419 insertions, 356 deletions

diff --git a/net/tipc/link.c b/net/tipc/link.c
index ff9b0b92e62e..4449fa01e232 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -50,6 +50,7 @@
  */
 static const char *link_co_err = "Link tunneling error, ";
 static const char *link_rst_msg = "Resetting link ";
+static const char tipc_bclink_name[] = "broadcast-link";
 
 static const struct nla_policy tipc_nl_link_policy[TIPC_NLA_LINK_MAX + 1] = {
 	[TIPC_NLA_LINK_UNSPEC]		= { .type = NLA_UNSPEC },
@@ -75,6 +76,14 @@ static const struct nla_policy tipc_nl_prop_policy[TIPC_NLA_PROP_MAX + 1] = {
 	[TIPC_NLA_PROP_WIN]		= { .type = NLA_U32 }
 };
 
+/* Send states for broadcast NACKs
+ */
+enum {
+	BC_NACK_SND_CONDITIONAL,
+	BC_NACK_SND_UNCONDITIONAL,
+	BC_NACK_SND_SUPPRESS,
+};
+
 /*
  * Interval between NACKs when packets arrive out of order
  */
@@ -110,7 +119,11 @@ static void tipc_link_build_proto_msg(struct tipc_link *l, int mtyp, bool probe,
 				      struct sk_buff_head *xmitq);
 static void link_reset_statistics(struct tipc_link *l_ptr);
 static void link_print(struct tipc_link *l_ptr, const char *str);
-static void tipc_link_sync_rcv(struct tipc_node *n, struct sk_buff *buf);
+static void tipc_link_build_nack_msg(struct tipc_link *l,
+				     struct sk_buff_head *xmitq);
+static void tipc_link_build_bc_init_msg(struct tipc_link *l,
+					struct sk_buff_head *xmitq);
+static bool tipc_link_release_pkts(struct tipc_link *l, u16 to);
 
 /*
  *  Simple non-static link routines (i.e. referenced outside this file)
@@ -150,11 +163,66 @@ bool tipc_link_is_blocked(struct tipc_link *l)
 	return l->state & (LINK_RESETTING | LINK_PEER_RESET | LINK_FAILINGOVER);
 }
 
+bool link_is_bc_sndlink(struct tipc_link *l)
+{
+	return !l->bc_sndlink;
+}
+
+bool link_is_bc_rcvlink(struct tipc_link *l)
+{
+	return ((l->bc_rcvlink == l) && !link_is_bc_sndlink(l));
+}
+
 int tipc_link_is_active(struct tipc_link *l)
 {
-	struct tipc_node *n = l->owner;
+	return l->active;
+}
+
+void tipc_link_set_active(struct tipc_link *l, bool active)
+{
+	l->active = active;
+}
+
+void tipc_link_add_bc_peer(struct tipc_link *snd_l,
+			   struct tipc_link *uc_l,
+			   struct sk_buff_head *xmitq)
+{
+	struct tipc_link *rcv_l = uc_l->bc_rcvlink;
 
-	return (node_active_link(n, 0) == l) || (node_active_link(n, 1) == l);
+	snd_l->ackers++;
+	rcv_l->acked = snd_l->snd_nxt - 1;
+	tipc_link_build_bc_init_msg(uc_l, xmitq);
+}
+
+void tipc_link_remove_bc_peer(struct tipc_link *snd_l,
+			      struct tipc_link *rcv_l,
+			      struct sk_buff_head *xmitq)
+{
+	u16 ack = snd_l->snd_nxt - 1;
+
+	snd_l->ackers--;
+	tipc_link_bc_ack_rcv(rcv_l, ack, xmitq);
+	tipc_link_reset(rcv_l);
+	rcv_l->state = LINK_RESET;
+	if (!snd_l->ackers) {
+		tipc_link_reset(snd_l);
+		__skb_queue_purge(xmitq);
+	}
+}
+
+int tipc_link_bc_peers(struct tipc_link *l)
+{
+	return l->ackers;
+}
+
+void tipc_link_set_mtu(struct tipc_link *l, int mtu)
+{
+	l->mtu = mtu;
+}
+
+int tipc_link_mtu(struct tipc_link *l)
+{
+	return l->mtu;
 }
 
 static u32 link_own_addr(struct tipc_link *l)
@@ -165,57 +233,72 @@ static u32 link_own_addr(struct tipc_link *l)
 /**
  * tipc_link_create - create a new link
  * @n: pointer to associated node
- * @b: pointer to associated bearer
+ * @if_name: associated interface name
+ * @bearer_id: id (index) of associated bearer
+ * @tolerance: link tolerance to be used by link
+ * @net_plane: network plane (A,B,c..) this link belongs to
+ * @mtu: mtu to be advertised by link
+ * @priority: priority to be used by link
+ * @window: send window to be used by link
+ * @session: session to be used by link
  * @ownnode: identity of own node
- * @peer: identity of peer node
- * @maddr: media address to be used
+ * @peer: node id of peer node
+ * @peer_caps: bitmap describing peer node capabilities
+ * @bc_sndlink: the namespace global link used for broadcast sending
+ * @bc_rcvlink: the peer specific link used for broadcast reception
  * @inputq: queue to put messages ready for delivery
  * @namedq: queue to put binding table update messages ready for delivery
  * @link: return value, pointer to put the created link
  *
  * Returns true if link was created, otherwise false
  */
-bool tipc_link_create(struct tipc_node *n, struct tipc_bearer *b, u32 session,
-		      u32 ownnode, u32 peer, struct tipc_media_addr *maddr,
-		      struct sk_buff_head *inputq, struct sk_buff_head *namedq,
+bool tipc_link_create(struct net *net, char *if_name, int bearer_id,
+		      int tolerance, char net_plane, u32 mtu, int priority,
+		      int window, u32 session, u32 ownnode, u32 peer,
+		      u16 peer_caps,
+		      struct tipc_link *bc_sndlink,
+		      struct tipc_link *bc_rcvlink,
+		      struct sk_buff_head *inputq,
+		      struct sk_buff_head *namedq,
 		      struct tipc_link **link)
 {
 	struct tipc_link *l;
 	struct tipc_msg *hdr;
-	char *if_name;
 
 	l = kzalloc(sizeof(*l), GFP_ATOMIC);
 	if (!l)
 		return false;
 	*link = l;
+	l->pmsg = (struct tipc_msg *)&l->proto_msg;
+	hdr = l->pmsg;
+	tipc_msg_init(ownnode, hdr, LINK_PROTOCOL, RESET_MSG, INT_H_SIZE, peer);
+	msg_set_size(hdr, sizeof(l->proto_msg));
+	msg_set_session(hdr, session);
+	msg_set_bearer_id(hdr, l->bearer_id);
 
 	/* Note: peer i/f name is completed by reset/activate message */
-	if_name = strchr(b->name, ':') + 1;
 	sprintf(l->name, "%u.%u.%u:%s-%u.%u.%u:unknown",
 		tipc_zone(ownnode), tipc_cluster(ownnode), tipc_node(ownnode),
 		if_name, tipc_zone(peer), tipc_cluster(peer), tipc_node(peer));
+	strcpy((char *)msg_data(hdr), if_name);
 
 	l->addr = peer;
-	l->media_addr = maddr;
-	l->owner = n;
+	l->peer_caps = peer_caps;
+	l->net = net;
 	l->peer_session = WILDCARD_SESSION;
-	l->bearer_id = b->identity;
-	l->tolerance = b->tolerance;
-	l->net_plane = b->net_plane;
-	l->advertised_mtu = b->mtu;
-	l->mtu = b->mtu;
-	l->priority = b->priority;
-	tipc_link_set_queue_limits(l, b->window);
+	l->bearer_id = bearer_id;
+	l->tolerance = tolerance;
+	l->net_plane = net_plane;
+	l->advertised_mtu = mtu;
+	l->mtu = mtu;
+	l->priority = priority;
+	tipc_link_set_queue_limits(l, window);
+	l->ackers = 1;
+	l->bc_sndlink = bc_sndlink;
+	l->bc_rcvlink = bc_rcvlink;
 	l->inputq = inputq;
 	l->namedq = namedq;
 	l->state = LINK_RESETTING;
-	l->pmsg = (struct tipc_msg *)&l->proto_msg;
-	hdr = l->pmsg;
-	tipc_msg_init(ownnode, hdr, LINK_PROTOCOL, RESET_MSG, INT_H_SIZE, peer);
-	msg_set_size(hdr, sizeof(l->proto_msg));
-	msg_set_session(hdr, session);
-	msg_set_bearer_id(hdr, l->bearer_id);
-	strcpy((char *)msg_data(hdr), if_name);
 	__skb_queue_head_init(&l->transmq);
 	__skb_queue_head_init(&l->backlogq);
 	__skb_queue_head_init(&l->deferdq);
@@ -224,27 +307,43 @@ bool tipc_link_create(struct tipc_node *n, struct tipc_bearer *b, u32 session,
 	return true;
 }
 
-/* tipc_link_build_bcast_sync_msg() - synchronize broadcast link endpoints.
+/**
+ * tipc_link_bc_create - create new link to be used for broadcast
+ * @n: pointer to associated node
+ * @mtu: mtu to be used
+ * @window: send window to be used
+ * @inputq: queue to put messages ready for delivery
+ * @namedq: queue to put binding table update messages ready for delivery
+ * @link: return value, pointer to put the created link
  *
- * Give a newly added peer node the sequence number where it should
- * start receiving and acking broadcast packets.
+ * Returns true if link was created, otherwise false
  */
-void tipc_link_build_bcast_sync_msg(struct tipc_link *l,
-				    struct sk_buff_head *xmitq)
+bool tipc_link_bc_create(struct net *net, u32 ownnode, u32 peer,
+			 int mtu, int window, u16 peer_caps,
+			 struct sk_buff_head *inputq,
+			 struct sk_buff_head *namedq,
+			 struct tipc_link *bc_sndlink,
+			 struct tipc_link **link)
 {
-	struct sk_buff *skb;
-	struct sk_buff_head list;
-	u16 last_sent;
+	struct tipc_link *l;
 
-	skb = tipc_msg_create(BCAST_PROTOCOL, STATE_MSG, INT_H_SIZE,
-			      0, l->addr, link_own_addr(l), 0, 0, 0);
-	if (!skb)
-		return;
-	last_sent = tipc_bclink_get_last_sent(l->owner->net);
-	msg_set_last_bcast(buf_msg(skb), last_sent);
-	__skb_queue_head_init(&list);
-	__skb_queue_tail(&list, skb);
-	tipc_link_xmit(l, &list, xmitq);
+	if (!tipc_link_create(net, "", MAX_BEARERS, 0, 'Z', mtu, 0, window,
+			      0, ownnode, peer, peer_caps, bc_sndlink,
+			      NULL, inputq, namedq, link))
+		return false;
+
+	l = *link;
+	strcpy(l->name, tipc_bclink_name);
+	tipc_link_reset(l);
+	l->state = LINK_RESET;
+	l->ackers = 0;
+	l->bc_rcvlink = l;
+
+	/* Broadcast send link is always up */
+	if (link_is_bc_sndlink(l))
+		l->state = LINK_ESTABLISHED;
+
+	return true;
 }
 
 /**
@@ -451,12 +550,17 @@ static void link_profile_stats(struct tipc_link *l)
 
 /* tipc_link_timeout - perform periodic task as instructed from node timeout
  */
+/* tipc_link_timeout - perform periodic task as instructed from node timeout
+ */
 int tipc_link_timeout(struct tipc_link *l, struct sk_buff_head *xmitq)
 {
 	int rc = 0;
 	int mtyp = STATE_MSG;
 	bool xmit = false;
 	bool prb = false;
+	u16 bc_snt = l->bc_sndlink->snd_nxt - 1;
+	u16 bc_acked = l->bc_rcvlink->acked;
+	bool bc_up = link_is_up(l->bc_rcvlink);
 
 	link_profile_stats(l);
 
@@ -464,7 +568,7 @@ int tipc_link_timeout(struct tipc_link *l, struct sk_buff_head *xmitq)
 	case LINK_ESTABLISHED:
 	case LINK_SYNCHING:
 		if (!l->silent_intv_cnt) {
-			if (tipc_bclink_acks_missing(l->owner))
+			if (bc_up && (bc_acked != bc_snt))
 				xmit = true;
 		} else if (l->silent_intv_cnt <= l->abort_limit) {
 			xmit = true;
@@ -555,38 +659,6 @@ void link_prepare_wakeup(struct tipc_link *l)
 	}
 }
 
-/**
- * tipc_link_reset_fragments - purge link's inbound message fragments queue
- * @l_ptr: pointer to link
- */
-void tipc_link_reset_fragments(struct tipc_link *l_ptr)
-{
-	kfree_skb(l_ptr->reasm_buf);
-	l_ptr->reasm_buf = NULL;
-}
-
-void tipc_link_purge_backlog(struct tipc_link *l)
-{
-	__skb_queue_purge(&l->backlogq);
-	l->backlog[TIPC_LOW_IMPORTANCE].len = 0;
-	l->backlog[TIPC_MEDIUM_IMPORTANCE].len = 0;
-	l->backlog[TIPC_HIGH_IMPORTANCE].len = 0;
-	l->backlog[TIPC_CRITICAL_IMPORTANCE].len = 0;
-	l->backlog[TIPC_SYSTEM_IMPORTANCE].len = 0;
-}
-
-/**
- * tipc_link_purge_queues - purge all pkt queues associated with link
- * @l_ptr: pointer to link
- */
-void tipc_link_purge_queues(struct tipc_link *l_ptr)
-{
-	__skb_queue_purge(&l_ptr->deferdq);
-	__skb_queue_purge(&l_ptr->transmq);
-	tipc_link_purge_backlog(l_ptr);
-	tipc_link_reset_fragments(l_ptr);
-}
-
 void tipc_link_reset(struct tipc_link *l)
 {
 	/* Link is down, accept any session */
@@ -598,12 +670,16 @@ void tipc_link_reset(struct tipc_link *l)
 	/* Prepare for renewed mtu size negotiation */
 	l->mtu = l->advertised_mtu;
 
-	/* Clean up all queues: */
+	/* Clean up all queues and counters: */
 	__skb_queue_purge(&l->transmq);
 	__skb_queue_purge(&l->deferdq);
 	skb_queue_splice_init(&l->wakeupq, l->inputq);
-
-	tipc_link_purge_backlog(l);
+	__skb_queue_purge(&l->backlogq);
+	l->backlog[TIPC_LOW_IMPORTANCE].len = 0;
+	l->backlog[TIPC_MEDIUM_IMPORTANCE].len = 0;
+	l->backlog[TIPC_HIGH_IMPORTANCE].len = 0;
+	l->backlog[TIPC_CRITICAL_IMPORTANCE].len = 0;
+	l->backlog[TIPC_SYSTEM_IMPORTANCE].len = 0;
 	kfree_skb(l->reasm_buf);
 	kfree_skb(l->failover_reasm_skb);
 	l->reasm_buf = NULL;
@@ -611,81 +687,15 @@ void tipc_link_reset(struct tipc_link *l)
 	l->rcv_unacked = 0;
 	l->snd_nxt = 1;
 	l->rcv_nxt = 1;
+	l->acked = 0;
 	l->silent_intv_cnt = 0;
 	l->stats.recv_info = 0;
 	l->stale_count = 0;
+	l->bc_peer_is_up = false;
 	link_reset_statistics(l);
 }
 
 /**
- * __tipc_link_xmit(): same as tipc_link_xmit, but destlink is known & locked
- * @link: link to use
- * @list: chain of buffers containing message
- *
- * Consumes the buffer chain, except when returning an error code,
- * Returns 0 if success, or errno: -ELINKCONG, -EMSGSIZE or -ENOBUFS
- * Messages at TIPC_SYSTEM_IMPORTANCE are always accepted
- */
-int __tipc_link_xmit(struct net *net, struct tipc_link *link,
-		     struct sk_buff_head *list)
-{
-	struct tipc_msg *msg = buf_msg(skb_peek(list));
-	unsigned int maxwin = link->window;
-	unsigned int i, imp = msg_importance(msg);
-	uint mtu = link->mtu;
-	u16 ack = mod(link->rcv_nxt - 1);
-	u16 seqno = link->snd_nxt;
-	u16 bc_last_in = link->owner->bclink.last_in;
-	struct tipc_media_addr *addr = link->media_addr;
-	struct sk_buff_head *transmq = &link->transmq;
-	struct sk_buff_head *backlogq = &link->backlogq;
-	struct sk_buff *skb, *bskb;
-
-	/* Match msg importance against this and all higher backlog limits: */
-	for (i = imp; i <= TIPC_SYSTEM_IMPORTANCE; i++) {
-		if (unlikely(link->backlog[i].len >= link->backlog[i].limit))
-			return link_schedule_user(link, list);
-	}
-	if (unlikely(msg_size(msg) > mtu))
-		return -EMSGSIZE;
-
-	/* Prepare each packet for sending, and add to relevant queue: */
-	while (skb_queue_len(list)) {
-		skb = skb_peek(list);
-		msg = buf_msg(skb);
-		msg_set_seqno(msg, seqno);
-		msg_set_ack(msg, ack);
-		msg_set_bcast_ack(msg, bc_last_in);
-
-		if (likely(skb_queue_len(transmq) < maxwin)) {
-			__skb_dequeue(list);
-			__skb_queue_tail(transmq, skb);
-			tipc_bearer_send(net, link->bearer_id, skb, addr);
-			link->rcv_unacked = 0;
-			seqno++;
-			continue;
-		}
-		if (tipc_msg_bundle(skb_peek_tail(backlogq), msg, mtu)) {
-			kfree_skb(__skb_dequeue(list));
-			link->stats.sent_bundled++;
-			continue;
-		}
-		if (tipc_msg_make_bundle(&bskb, msg, mtu, link->addr)) {
-			kfree_skb(__skb_dequeue(list));
-			__skb_queue_tail(backlogq, bskb);
-			link->backlog[msg_importance(buf_msg(bskb))].len++;
-			link->stats.sent_bundled++;
-			link->stats.sent_bundles++;
-			continue;
-		}
-		link->backlog[imp].len += skb_queue_len(list);
-		skb_queue_splice_tail_init(list, backlogq);
-	}
-	link->snd_nxt = seqno;
-	return 0;
-}
-
-/**
  * tipc_link_xmit(): enqueue buffer list according to queue situation
  * @link: link to use
  * @list: chain of buffers containing message
@@ -705,7 +715,7 @@ int tipc_link_xmit(struct tipc_link *l, struct sk_buff_head *list,
 	unsigned int mtu = l->mtu;
 	u16 ack = l->rcv_nxt - 1;
 	u16 seqno = l->snd_nxt;
-	u16 bc_last_in = l->owner->bclink.last_in;
+	u16 bc_ack = l->bc_rcvlink->rcv_nxt - 1;
 	struct sk_buff_head *transmq = &l->transmq;
 	struct sk_buff_head *backlogq = &l->backlogq;
 	struct sk_buff *skb, *_skb, *bskb;
@@ -724,7 +734,7 @@ int tipc_link_xmit(struct tipc_link *l, struct sk_buff_head *list,
 		hdr = buf_msg(skb);
 		msg_set_seqno(hdr, seqno);
 		msg_set_ack(hdr, ack);
-		msg_set_bcast_ack(hdr, bc_last_in);
+		msg_set_bcast_ack(hdr, bc_ack);
 
 		if (likely(skb_queue_len(transmq) < maxwin)) {
 			_skb = skb_clone(skb, GFP_ATOMIC);
@@ -733,6 +743,7 @@ int tipc_link_xmit(struct tipc_link *l, struct sk_buff_head *list,
 			__skb_dequeue(list);
 			__skb_queue_tail(transmq, skb);
 			__skb_queue_tail(xmitq, _skb);
+			TIPC_SKB_CB(skb)->ackers = l->ackers;
 			l->rcv_unacked = 0;
 			seqno++;
 			continue;
@@ -757,62 +768,13 @@ int tipc_link_xmit(struct tipc_link *l, struct sk_buff_head *list,
 	return 0;
 }
 
-/*
- * tipc_link_sync_rcv - synchronize broadcast link endpoints.
- * Receive the sequence number where we should start receiving and
- * acking broadcast packets from a newly added peer node, and open
- * up for reception of such packets.
- *
- * Called with node locked
- */
-static void tipc_link_sync_rcv(struct tipc_node *n, struct sk_buff *buf)
-{
-	struct tipc_msg *msg = buf_msg(buf);
-
-	n->bclink.last_sent = n->bclink.last_in = msg_last_bcast(msg);
-	n->bclink.recv_permitted = true;
-	kfree_skb(buf);
-}
-
-/*
- * tipc_link_push_packets - push unsent packets to bearer
- *
- * Push out the unsent messages of a link where congestion
- * has abated. Node is locked.
- *
- * Called with node locked
- */
-void tipc_link_push_packets(struct tipc_link *link)
-{
-	struct sk_buff *skb;
-	struct tipc_msg *msg;
-	u16 seqno = link->snd_nxt;
-	u16 ack = mod(link->rcv_nxt - 1);
-
-	while (skb_queue_len(&link->transmq) < link->window) {
-		skb = __skb_dequeue(&link->backlogq);
-		if (!skb)
-			break;
-		msg = buf_msg(skb);
-		link->backlog[msg_importance(msg)].len--;
-		msg_set_ack(msg, ack);
-		msg_set_seqno(msg, seqno);
-		seqno = mod(seqno + 1);
-		msg_set_bcast_ack(msg, link->owner->bclink.last_in);
-		link->rcv_unacked = 0;
-		__skb_queue_tail(&link->transmq, skb);
-		tipc_bearer_send(link->owner->net, link->bearer_id,
-				 skb, link->media_addr);
-	}
-	link->snd_nxt = seqno;
-}
-
 void tipc_link_advance_backlog(struct tipc_link *l, struct sk_buff_head *xmitq)
 {
 	struct sk_buff *skb, *_skb;
 	struct tipc_msg *hdr;
 	u16 seqno = l->snd_nxt;
 	u16 ack = l->rcv_nxt - 1;
+	u16 bc_ack = l->bc_rcvlink->rcv_nxt - 1;
 
 	while (skb_queue_len(&l->transmq) < l->window) {
 		skb = skb_peek(&l->backlogq);
@@ -826,96 +788,35 @@ void tipc_link_advance_backlog(struct tipc_link *l, struct sk_buff_head *xmitq)
 		l->backlog[msg_importance(hdr)].len--;
 		__skb_queue_tail(&l->transmq, skb);
 		__skb_queue_tail(xmitq, _skb);
-		msg_set_ack(hdr, ack);
+		TIPC_SKB_CB(skb)->ackers = l->ackers;
 		msg_set_seqno(hdr, seqno);
-		msg_set_bcast_ack(hdr, l->owner->bclink.last_in);
+		msg_set_ack(hdr, ack);
+		msg_set_bcast_ack(hdr, bc_ack);
 		l->rcv_unacked = 0;
 		seqno++;
 	}
 	l->snd_nxt = seqno;
 }
 
-static void link_retransmit_failure(struct tipc_link *l_ptr,
-				    struct sk_buff *buf)
-{
-	struct tipc_msg *msg = buf_msg(buf);
-	struct net *net = l_ptr->owner->net;
-
-	pr_warn("Retransmission failure on link <%s>\n", l_ptr->name);
-
-	if (l_ptr->addr) {
-		/* Handle failure on standard link */
-		link_print(l_ptr, "Resetting link ");
-		pr_info("Failed msg: usr %u, typ %u, len %u, err %u\n",
-			msg_user(msg), msg_type(msg), msg_size(msg),
-			msg_errcode(msg));
-		pr_info("sqno %u, prev: %x, src: %x\n",
-			msg_seqno(msg), msg_prevnode(msg), msg_orignode(msg));
-	} else {
-		/* Handle failure on broadcast link */
-		struct tipc_node *n_ptr;
-		char addr_string[16];
-
-		pr_info("Msg seq number: %u,  ", msg_seqno(msg));
-		pr_cont("Outstanding acks: %lu\n",
-			(unsigned long) TIPC_SKB_CB(buf)->handle);
-
-		n_ptr = tipc_bclink_retransmit_to(net);
-
-		tipc_addr_string_fill(addr_string, n_ptr->addr);
-		pr_info("Broadcast link info for %s\n", addr_string);
-		pr_info("Reception permitted: %d,  Acked: %u\n",
-			n_ptr->bclink.recv_permitted,
-			n_ptr->bclink.acked);
-		pr_info("Last in: %u,  Oos state: %u,  Last sent: %u\n",
-			n_ptr->bclink.last_in,
-			n_ptr->bclink.oos_state,
-			n_ptr->bclink.last_sent);
-
-		n_ptr->action_flags |= TIPC_BCAST_RESET;
-		l_ptr->stale_count = 0;
-	}
-}
-
-void tipc_link_retransmit(struct tipc_link *l_ptr, struct sk_buff *skb,
-			  u32 retransmits)
+static void link_retransmit_failure(struct tipc_link *l, struct sk_buff *skb)
 {
-	struct tipc_msg *msg;
-
-	if (!skb)
-		return;
-
-	msg = buf_msg(skb);
-
-	/* Detect repeated retransmit failures */
-	if (l_ptr->last_retransm == msg_seqno(msg)) {
-		if (++l_ptr->stale_count > 100) {
-			link_retransmit_failure(l_ptr, skb);
-			return;
-		}
-	} else {
-		l_ptr->last_retransm = msg_seqno(msg);
-		l_ptr->stale_count = 1;
-	}
+	struct tipc_msg *hdr = buf_msg(skb);
 
-	skb_queue_walk_from(&l_ptr->transmq, skb) {
-		if (!retransmits)
-			break;
-		msg = buf_msg(skb);
-		msg_set_ack(msg, mod(l_ptr->rcv_nxt - 1));
-		msg_set_bcast_ack(msg, l_ptr->owner->bclink.last_in);
-		tipc_bearer_send(l_ptr->owner->net, l_ptr->bearer_id, skb,
-				 l_ptr->media_addr);
-		retransmits--;
-		l_ptr->stats.retransmitted++;
-	}
+	pr_warn("Retransmission failure on link <%s>\n", l->name);
+	link_print(l, "Resetting link ");
+	pr_info("Failed msg: usr %u, typ %u, len %u, err %u\n",
+		msg_user(hdr), msg_type(hdr), msg_size(hdr), msg_errcode(hdr));
+	pr_info("sqno %u, prev: %x, src: %x\n",
+		msg_seqno(hdr), msg_prevnode(hdr), msg_orignode(hdr));
 }
 
-static int tipc_link_retransm(struct tipc_link *l, int retransm,
-			      struct sk_buff_head *xmitq)
+int tipc_link_retrans(struct tipc_link *l, u16 from, u16 to,
+		      struct sk_buff_head *xmitq)
 {
 	struct sk_buff *_skb, *skb = skb_peek(&l->transmq);
 	struct tipc_msg *hdr;
+	u16 ack = l->rcv_nxt - 1;
+	u16 bc_ack = l->bc_rcvlink->rcv_nxt - 1;
 
 	if (!skb)
 		return 0;
@@ -928,19 +829,25 @@ static int tipc_link_retransm(struct tipc_link *l, int retransm,
 		link_retransmit_failure(l, skb);
 		return tipc_link_fsm_evt(l, LINK_FAILURE_EVT);
 	}
+
+	/* Move forward to where retransmission should start */
 	skb_queue_walk(&l->transmq, skb) {
-		if (!retransm)
-			return 0;
+		if (!less(buf_seqno(skb), from))
+			break;
+	}
+
+	skb_queue_walk_from(&l->transmq, skb) {
+		if (more(buf_seqno(skb), to))
+			break;
 		hdr = buf_msg(skb);
 		_skb = __pskb_copy(skb, MIN_H_SIZE, GFP_ATOMIC);
 		if (!_skb)
 			return 0;
 		hdr = buf_msg(_skb);
-		msg_set_ack(hdr, l->rcv_nxt - 1);
-		msg_set_bcast_ack(hdr, l->owner->bclink.last_in);
+		msg_set_ack(hdr, ack);
+		msg_set_bcast_ack(hdr, bc_ack);
 		_skb->priority = TC_PRIO_CONTROL;
 		__skb_queue_tail(xmitq, _skb);
-		retransm--;
 		l->stats.retransmitted++;
 	}
 	return 0;
@@ -951,11 +858,9 @@ static int tipc_link_retransm(struct tipc_link *l, int retransm,
  * Consumes buffer if message is of right type
  * Node lock must be held
  */
-static bool tipc_data_input(struct tipc_link *link, struct sk_buff *skb,
+static bool tipc_data_input(struct tipc_link *l, struct sk_buff *skb,
 			    struct sk_buff_head *inputq)
 {
-	struct tipc_node *node = link->owner;
-
 	switch (msg_user(buf_msg(skb))) {
 	case TIPC_LOW_IMPORTANCE:
 	case TIPC_MEDIUM_IMPORTANCE:
@@ -965,8 +870,8 @@ static bool tipc_data_input(struct tipc_link *link, struct sk_buff *skb,
 		skb_queue_tail(inputq, skb);
 		return true;
 	case NAME_DISTRIBUTOR:
-		node->bclink.recv_permitted = true;
-		skb_queue_tail(link->namedq, skb);
+		l->bc_rcvlink->state = LINK_ESTABLISHED;
+		skb_queue_tail(l->namedq, skb);
 		return true;
 	case MSG_BUNDLER:
 	case TUNNEL_PROTOCOL:
@@ -987,7 +892,6 @@ static bool tipc_data_input(struct tipc_link *link, struct sk_buff *skb,
 static int tipc_link_input(struct tipc_link *l, struct sk_buff *skb,
 			   struct sk_buff_head *inputq)
 {
-	struct tipc_node *node = l->owner;
 	struct tipc_msg *hdr = buf_msg(skb);
 	struct sk_buff **reasm_skb = &l->reasm_buf;
 	struct sk_buff *iskb;
@@ -1028,13 +932,15 @@ static int tipc_link_input(struct tipc_link *l, struct sk_buff *skb,
 		if (tipc_buf_append(reasm_skb, &skb)) {
 			l->stats.recv_fragmented++;
 			tipc_data_input(l, skb, inputq);
-		} else if (!*reasm_skb) {
+		} else if (!*reasm_skb && !link_is_bc_rcvlink(l)) {
+			pr_warn_ratelimited("Unable to build fragment list\n");
 			return tipc_link_fsm_evt(l, LINK_FAILURE_EVT);
 		}
 		return 0;
 	} else if (usr == BCAST_PROTOCOL) {
-		tipc_link_sync_rcv(node, skb);
-		return 0;
+		tipc_bcast_lock(l->net);
+		tipc_link_bc_init_rcv(l->bc_rcvlink, hdr);
+		tipc_bcast_unlock(l->net);
 	}
 drop:
 	kfree_skb(skb);
@@ -1057,12 +963,28 @@ static bool tipc_link_release_pkts(struct tipc_link *l, u16 acked)
 }
 
 /* tipc_link_build_ack_msg: prepare link acknowledge message for transmission
+ *
+ * Note that sending of broadcast ack is coordinated among nodes, to reduce
+ * risk of ack storms towards the sender
  */
-void tipc_link_build_ack_msg(struct tipc_link *l, struct sk_buff_head *xmitq)
+int tipc_link_build_ack_msg(struct tipc_link *l, struct sk_buff_head *xmitq)
 {
+	if (!l)
+		return 0;
+
+	/* Broadcast ACK must be sent via a unicast link => defer to caller */
+	if (link_is_bc_rcvlink(l)) {
+		if (((l->rcv_nxt ^ link_own_addr(l)) & 0xf) != 0xf)
+			return 0;
+		l->rcv_unacked = 0;
+		return TIPC_LINK_SND_BC_ACK;
+	}
+
+	/* Unicast ACK */
 	l->rcv_unacked = 0;
 	l->stats.sent_acks++;
 	tipc_link_build_proto_msg(l, STATE_MSG, 0, 0, 0, 0, xmitq);
+	return 0;
 }
 
 /* tipc_link_build_reset_msg: prepare link RESET or ACTIVATE message
@@ -1084,6 +1006,9 @@ static void tipc_link_build_nack_msg(struct tipc_link *l,
 {
 	u32 def_cnt = ++l->stats.deferred_recv;
 
+	if (link_is_bc_rcvlink(l))
+		return;
+
 	if ((skb_queue_len(&l->deferdq) == 1) || !(def_cnt % TIPC_NACK_INTV))
 		tipc_link_build_proto_msg(l, STATE_MSG, 0, 0, 0, 0, xmitq);
 }
@@ -1144,12 +1069,11 @@ int tipc_link_rcv(struct tipc_link *l, struct sk_buff *skb,
 		l->rcv_nxt++;
 		l->stats.recv_info++;
 		if (!tipc_data_input(l, skb, l->inputq))
-			rc = tipc_link_input(l, skb, l->inputq);
-		if (unlikely(rc))
-			break;
+			rc |= tipc_link_input(l, skb, l->inputq);
 		if (unlikely(++l->rcv_unacked >= TIPC_MIN_LINK_WIN))
-			tipc_link_build_ack_msg(l, xmitq);
-
+			rc |= tipc_link_build_ack_msg(l, xmitq);
+		if (unlikely(rc & ~TIPC_LINK_SND_BC_ACK))
+			break;
 	} while ((skb = __skb_dequeue(defq)));
 
 	return rc;
@@ -1158,45 +1082,6 @@ drop:
 	return rc;
 }
 
-/**
- * tipc_link_defer_pkt - Add out-of-sequence message to deferred reception queue
- *
- * Returns increase in queue length (i.e. 0 or 1)
- */
-u32 tipc_link_defer_pkt(struct sk_buff_head *list, struct sk_buff *skb)
-{
-	struct sk_buff *skb1;
-	u16 seq_no = buf_seqno(skb);
-
-	/* Empty queue ? */
-	if (skb_queue_empty(list)) {
-		__skb_queue_tail(list, skb);
-		return 1;
-	}
-
-	/* Last ? */
-	if (less(buf_seqno(skb_peek_tail(list)), seq_no)) {
-		__skb_queue_tail(list, skb);
-		return 1;
-	}
-
-	/* Locate insertion point in queue, then insert; discard if duplicate */
-	skb_queue_walk(list, skb1) {
-		u16 curr_seqno = buf_seqno(skb1);
-
-		if (seq_no == curr_seqno) {
-			kfree_skb(skb);
-			return 0;
-		}
-
-		if (less(seq_no, curr_seqno))
-			break;
-	}
-
-	__skb_queue_before(list, skb1, skb);
-	return 1;
-}
-
 /*
  * Send protocol message to the other endpoint.
  */
@@ -1212,23 +1097,17 @@ void tipc_link_proto_xmit(struct tipc_link *l, u32 msg_typ, int probe_msg,
 	skb = __skb_dequeue(&xmitq);
 	if (!skb)
 		return;
-	tipc_bearer_send(l->owner->net, l->bearer_id, skb, l->media_addr);
+	tipc_bearer_xmit_skb(l->net, l->bearer_id, skb, l->media_addr);
 	l->rcv_unacked = 0;
-	kfree_skb(skb);
 }
 
-/* tipc_link_build_proto_msg: prepare link protocol message for transmission
- */
 static void tipc_link_build_proto_msg(struct tipc_link *l, int mtyp, bool probe,
 				      u16 rcvgap, int tolerance, int priority,
 				      struct sk_buff_head *xmitq)
 {
 	struct sk_buff *skb = NULL;
 	struct tipc_msg *hdr = l->pmsg;
-	u16 snd_nxt = l->snd_nxt;
-	u16 rcv_nxt = l->rcv_nxt;
-	u16 rcv_last = rcv_nxt - 1;
-	int node_up = l->owner->bclink.recv_permitted;
+	bool node_up = link_is_up(l->bc_rcvlink);
 
 	/* Don't send protocol message during reset or link failover */
 	if (tipc_link_is_blocked(l))
@@ -1236,33 +1115,34 @@ static void tipc_link_build_proto_msg(struct tipc_link *l, int mtyp, bool probe,
 
 	msg_set_type(hdr, mtyp);
 	msg_set_net_plane(hdr, l->net_plane);
-	msg_set_bcast_ack(hdr, l->owner->bclink.last_in);
-	msg_set_last_bcast(hdr, tipc_bclink_get_last_sent(l->owner->net));
+	msg_set_next_sent(hdr, l->snd_nxt);
+	msg_set_ack(hdr, l->rcv_nxt - 1);
+	msg_set_bcast_ack(hdr, l->bc_rcvlink->rcv_nxt - 1);
+	msg_set_last_bcast(hdr, l->bc_sndlink->snd_nxt - 1);
 	msg_set_link_tolerance(hdr, tolerance);
 	msg_set_linkprio(hdr, priority);
 	msg_set_redundant_link(hdr, node_up);
 	msg_set_seq_gap(hdr, 0);
 
 	/* Compatibility: created msg must not be in sequence with pkt flow */
-	msg_set_seqno(hdr, snd_nxt + U16_MAX / 2);
+	msg_set_seqno(hdr, l->snd_nxt + U16_MAX / 2);
 
 	if (mtyp == STATE_MSG) {
 		if (!tipc_link_is_up(l))
 			return;
-		msg_set_next_sent(hdr, snd_nxt);
 
 		/* Override rcvgap if there are packets in deferred queue */
 		if (!skb_queue_empty(&l->deferdq))
-			rcvgap = buf_seqno(skb_peek(&l->deferdq)) - rcv_nxt;
+			rcvgap = buf_seqno(skb_peek(&l->deferdq)) - l->rcv_nxt;
 		if (rcvgap) {
 			msg_set_seq_gap(hdr, rcvgap);
 			l->stats.sent_nacks++;
 		}
-		msg_set_ack(hdr, rcv_last);
 		msg_set_probe(hdr, probe);
 		if (probe)
 			l->stats.sent_probes++;
 		l->stats.sent_states++;
+		l->rcv_unacked = 0;
 	} else {
 		/* RESET_MSG or ACTIVATE_MSG */
 		msg_set_max_pkt(hdr, l->advertised_mtu);
@@ -1354,7 +1234,8 @@ static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
 {
 	struct tipc_msg *hdr = buf_msg(skb);
 	u16 rcvgap = 0;
-	u16 nacked_gap = msg_seq_gap(hdr);
+	u16 ack = msg_ack(hdr);
+	u16 gap = msg_seq_gap(hdr);
 	u16 peers_snd_nxt =  msg_next_sent(hdr);
 	u16 peers_tol = msg_link_tolerance(hdr);
 	u16 peers_prio = msg_linkprio(hdr);
@@ -1363,7 +1244,7 @@ static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
 	char *if_name;
 	int rc = 0;
 
-	if (tipc_link_is_blocked(l))
+	if (tipc_link_is_blocked(l) || !xmitq)
 		goto exit;
 
 	if (link_own_addr(l) > msg_prevnode(hdr))
@@ -1433,11 +1314,11 @@ static int tipc_link_proto_rcv(struct tipc_link *l, struct sk_buff *skb,
 		if (rcvgap || (msg_probe(hdr)))
 			tipc_link_build_proto_msg(l, STATE_MSG, 0, rcvgap,
 						  0, 0, xmitq);
-		tipc_link_release_pkts(l, msg_ack(hdr));
+		tipc_link_release_pkts(l, ack);
 
 		/* If NACK, retransmit will now start at right position */
-		if (nacked_gap) {
-			rc = tipc_link_retransm(l, nacked_gap, xmitq);
+		if (gap) {
+			rc = tipc_link_retrans(l, ack + 1, ack + gap, xmitq);
 			l->stats.recv_nacks++;
 		}
 
@@ -1450,6 +1331,188 @@ exit:
 	return rc;
 }
 
+/* tipc_link_build_bc_proto_msg() - create broadcast protocol message
+ */
+static bool tipc_link_build_bc_proto_msg(struct tipc_link *l, bool bcast,
+					 u16 peers_snd_nxt,
+					 struct sk_buff_head *xmitq)
+{
+	struct sk_buff *skb;
+	struct tipc_msg *hdr;
+	struct sk_buff *dfrd_skb = skb_peek(&l->deferdq);
+	u16 ack = l->rcv_nxt - 1;
+	u16 gap_to = peers_snd_nxt - 1;
+
+	skb = tipc_msg_create(BCAST_PROTOCOL, STATE_MSG, INT_H_SIZE,
+			      0, l->addr, link_own_addr(l), 0, 0, 0);
+	if (!skb)
+		return false;
+	hdr = buf_msg(skb);
+	msg_set_last_bcast(hdr, l->bc_sndlink->snd_nxt - 1);
+	msg_set_bcast_ack(hdr, ack);
+	msg_set_bcgap_after(hdr, ack);
+	if (dfrd_skb)
+		gap_to = buf_seqno(dfrd_skb) - 1;
+	msg_set_bcgap_to(hdr, gap_to);
+	msg_set_non_seq(hdr, bcast);
+	__skb_queue_tail(xmitq, skb);
+	return true;
+}
+
+/* tipc_link_build_bc_init_msg() - synchronize broadcast link endpoints.
+ *
+ * Give a newly added peer node the sequence number where it should
+ * start receiving and acking broadcast packets.
+ */
+void tipc_link_build_bc_init_msg(struct tipc_link *l,
+				 struct sk_buff_head *xmitq)
+{
+	struct sk_buff_head list;
+
+	__skb_queue_head_init(&list);
+	if (!tipc_link_build_bc_proto_msg(l->bc_rcvlink, false, 0, &list))
+		return;
+	tipc_link_xmit(l, &list, xmitq);
+}
+
+/* tipc_link_bc_init_rcv - receive initial broadcast synch data from peer
+ */
+void tipc_link_bc_init_rcv(struct tipc_link *l, struct tipc_msg *hdr)
+{
+	int mtyp = msg_type(hdr);
+	u16 peers_snd_nxt = msg_bc_snd_nxt(hdr);
+
+	if (link_is_up(l))
+		return;
+
+	if (msg_user(hdr) == BCAST_PROTOCOL) {
+		l->rcv_nxt = peers_snd_nxt;
+		l->state = LINK_ESTABLISHED;
+		return;
+	}
+
+	if (l->peer_caps & TIPC_BCAST_SYNCH)
+		return;
+
+	if (msg_peer_node_is_up(hdr))
+		return;
+
+	/* Compatibility: accept older, less safe initial synch data */
+	if ((mtyp == RESET_MSG) || (mtyp == ACTIVATE_MSG))
+		l->rcv_nxt = peers_snd_nxt;
+}
+
+/* tipc_link_bc_sync_rcv - update rcv link according to peer's send state
+ */
+void tipc_link_bc_sync_rcv(struct tipc_link *l, struct tipc_msg *hdr,
+			   struct sk_buff_head *xmitq)
+{
+	u16 peers_snd_nxt = msg_bc_snd_nxt(hdr);
+
+	if (!link_is_up(l))
+		return;
+
+	if (!msg_peer_node_is_up(hdr))
+		return;
+
+	l->bc_peer_is_up = true;
+
+	/* Ignore if peers_snd_nxt goes beyond receive window */
+	if (more(peers_snd_nxt, l->rcv_nxt + l->window))
+		return;
+
+	if (!more(peers_snd_nxt, l->rcv_nxt)) {
+		l->nack_state = BC_NACK_SND_CONDITIONAL;
+		return;
+	}
+
+	/* Don't NACK if one was recently sent or peeked */
+	if (l->nack_state == BC_NACK_SND_SUPPRESS) {
+		l->nack_state = BC_NACK_SND_UNCONDITIONAL;
+		return;
+	}
+
+	/* Conditionally delay NACK sending until next synch rcv */
+	if (l->nack_state == BC_NACK_SND_CONDITIONAL) {
+		l->nack_state = BC_NACK_SND_UNCONDITIONAL;
+		if ((peers_snd_nxt - l->rcv_nxt) < TIPC_MIN_LINK_WIN)
+			return;
+	}
+
+	/* Send NACK now but suppress next one */
+	tipc_link_build_bc_proto_msg(l, true, peers_snd_nxt, xmitq);
+	l->nack_state = BC_NACK_SND_SUPPRESS;
+}
+
+void tipc_link_bc_ack_rcv(struct tipc_link *l, u16 acked,
+			  struct sk_buff_head *xmitq)
+{
+	struct sk_buff *skb, *tmp;
+	struct tipc_link *snd_l = l->bc_sndlink;
+
+	if (!link_is_up(l) || !l->bc_peer_is_up)
+		return;
+
+	if (!more(acked, l->acked))
+		return;
+
+	/* Skip over packets peer has already acked */
+	skb_queue_walk(&snd_l->transmq, skb) {
+		if (more(buf_seqno(skb), l->acked))
+			break;
+	}
+
+	/* Update/release the packets peer is acking now */
+	skb_queue_walk_from_safe(&snd_l->transmq, skb, tmp) {
+		if (more(buf_seqno(skb), acked))
+			break;
+		if (!--TIPC_SKB_CB(skb)->ackers) {
+			__skb_unlink(skb, &snd_l->transmq);
+			kfree_skb(skb);
+		}
+	}
+	l->acked = acked;
+	tipc_link_advance_backlog(snd_l, xmitq);
+	if (unlikely(!skb_queue_empty(&snd_l->wakeupq)))
+		link_prepare_wakeup(snd_l);
+}
+
+/* tipc_link_bc_nack_rcv(): receive broadcast nack message
+ */
+int tipc_link_bc_nack_rcv(struct tipc_link *l, struct sk_buff *skb,
+			  struct sk_buff_head *xmitq)
+{
+	struct tipc_msg *hdr = buf_msg(skb);
+	u32 dnode = msg_destnode(hdr);
+	int mtyp = msg_type(hdr);
+	u16 acked = msg_bcast_ack(hdr);
+	u16 from = acked + 1;
+	u16 to = msg_bcgap_to(hdr);
+	u16 peers_snd_nxt = to + 1;
+	int rc = 0;
+
+	kfree_skb(skb);
+
+	if (!tipc_link_is_up(l) || !l->bc_peer_is_up)
+		return 0;
+
+	if (mtyp != STATE_MSG)
+		return 0;
+
+	if (dnode == link_own_addr(l)) {
+		tipc_link_bc_ack_rcv(l, acked, xmitq);
+		rc = tipc_link_retrans(l->bc_sndlink, from, to, xmitq);
+		l->stats.recv_nacks++;
+		return rc;
+	}
+
+	/* Msg for other node => suppress own NACK at next sync if applicable */
+	if (more(peers_snd_nxt, l->rcv_nxt) && !less(l->rcv_nxt, from))
+		l->nack_state = BC_NACK_SND_SUPPRESS;
+
+	return 0;
+}
+
 void tipc_link_set_queue_limits(struct tipc_link *l, u32 win)
 {
 	int max_bulk = TIPC_MAX_PUBLICATIONS / (l->mtu / ITEM_SIZE);
@@ -1514,7 +1577,7 @@ static void link_reset_statistics(struct tipc_link *l_ptr)
 static void link_print(struct tipc_link *l, const char *str)
 {
 	struct sk_buff *hskb = skb_peek(&l->transmq);
-	u16 head = hskb ? msg_seqno(buf_msg(hskb)) : l->snd_nxt;
+	u16 head = hskb ? msg_seqno(buf_msg(hskb)) : l->snd_nxt - 1;
 	u16 tail = l->snd_nxt - 1;
 
 	pr_info("%s Link <%s> state %x\n", str, l->name, l->state);
@@ -1738,7 +1801,7 @@ static int __tipc_nl_add_link(struct net *net, struct tipc_nl_msg *msg,
 	if (tipc_link_is_up(link))
 		if (nla_put_flag(msg->skb, TIPC_NLA_LINK_UP))
 			goto attr_msg_full;
-	if (tipc_link_is_active(link))
+	if (link->active)
 		if (nla_put_flag(msg->skb, TIPC_NLA_LINK_ACTIVE))
 			goto attr_msg_full;