tipc: let broadcast packet reception use new link receive function

The code path for receiving broadcast packets is currently distinct
from the unicast path. This leads to unnecessary code and data
duplication, something that can be avoided with some effort.

We now introduce separate per-peer tipc_link instances for handling
broadcast packet reception. Each receive link keeps a pointer to the
common, single, broadcast link instance, and can hence handle release
and retransmission of send buffers as if they belonged to the own
instance.

Furthermore, we let each unicast link instance keep a reference to both
the pertaining broadcast receive link, and to the common send link.
This makes it possible for the unicast links to easily access data for
broadcast link synchronization, as well as for carrying acknowledges for
received broadcast packets.

Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 312 insertions, 123 deletions

diff --git a/net/tipc/link.c b/net/tipc/link.c
index 6a1a9d9239ae..ff725c398914 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -76,6 +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
  */
@@ -111,7 +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)
@@ -151,6 +163,16 @@ 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;
@@ -158,14 +180,31 @@ int tipc_link_is_active(struct tipc_link *l)
 	return (node_active_link(n, 0) == l) || (node_active_link(n, 1) == l);
 }
 
-void tipc_link_add_bc_peer(struct tipc_link *l)
+void tipc_link_add_bc_peer(struct tipc_link *snd_l,
+			   struct tipc_link *uc_l,
+			   struct sk_buff_head *xmitq)
 {
-	l->ackers++;
+	struct tipc_link *rcv_l = uc_l->bc_rcvlink;
+
+	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 *l)
+void tipc_link_remove_bc_peer(struct tipc_link *snd_l,
+			      struct tipc_link *rcv_l,
+			      struct sk_buff_head *xmitq)
 {
-	l->ackers--;
+	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)
@@ -193,6 +232,8 @@ static u32 link_own_addr(struct tipc_link *l)
  * @peer: node id of peer node
  * @peer_caps: bitmap describing peer node capabilities
  * @maddr: media address to be used
+ * @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
@@ -202,8 +243,12 @@ static u32 link_own_addr(struct tipc_link *l)
 bool tipc_link_create(struct tipc_node *n, 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_media_addr *maddr,
-		      struct sk_buff_head *inputq, struct sk_buff_head *namedq,
+		      u16 peer_caps,
+		      struct tipc_media_addr *maddr,
+		      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;
@@ -239,6 +284,8 @@ bool tipc_link_create(struct tipc_node *n, char *if_name, int bearer_id,
 	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;
@@ -261,46 +308,32 @@ bool tipc_link_create(struct tipc_node *n, char *if_name, int bearer_id,
  *
  * Returns true if link was created, otherwise false
  */
-bool tipc_link_bc_create(struct tipc_node *n, int mtu, int window,
-			 u16 peer_caps,
+bool tipc_link_bc_create(struct tipc_node *n, 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 tipc_link *l;
 
 	if (!tipc_link_create(n, "", MAX_BEARERS, 0, 'Z', mtu, 0, window,
-			      0, 0, 0, peer_caps, NULL, inputq, namedq, link))
+			      0, ownnode, peer, peer_caps, NULL, 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;
-	return true;
-}
+	l->bc_rcvlink = l;
 
-/* tipc_link_build_bcast_sync_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_bcast_sync_msg(struct tipc_link *l,
-				    struct sk_buff_head *xmitq)
-{
-	struct sk_buff *skb;
-	struct sk_buff_head list;
-	u16 last_sent;
+	/* Broadcast send link is always up */
+	if (link_is_bc_sndlink(l))
+		l->state = LINK_ESTABLISHED;
 
-	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);
+	return true;
 }
 
 /**
@@ -507,12 +540,17 @@ 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);
 
@@ -520,7 +558,7 @@ 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;
@@ -671,6 +709,7 @@ void tipc_link_reset(struct tipc_link *l)
 	l->silent_intv_cnt = 0;
 	l->stats.recv_info = 0;
 	l->stale_count = 0;
+	l->bc_peer_is_up = false;
 	link_reset_statistics(l);
 }
 
@@ -692,7 +731,7 @@ int __tipc_link_xmit(struct net *net, struct tipc_link *link,
 	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;
+	u16 bc_ack = link->bc_rcvlink->rcv_nxt - 1;
 	struct tipc_media_addr *addr = link->media_addr;
 	struct sk_buff_head *transmq = &link->transmq;
 	struct sk_buff_head *backlogq = &link->backlogq;
@@ -712,7 +751,7 @@ int __tipc_link_xmit(struct net *net, struct tipc_link *link,
 		msg = buf_msg(skb);
 		msg_set_seqno(msg, seqno);
 		msg_set_ack(msg, ack);
-		msg_set_bcast_ack(msg, bc_last_in);
+		msg_set_bcast_ack(msg, bc_ack);
 
 		if (likely(skb_queue_len(transmq) < maxwin)) {
 			__skb_dequeue(list);
@@ -762,7 +801,7 @@ 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;
@@ -781,7 +820,7 @@ 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);
@@ -816,23 +855,6 @@ int tipc_link_xmit(struct tipc_link *l, struct sk_buff_head *list,
 }
 
 /*
- * 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
@@ -872,6 +894,7 @@ void tipc_link_advance_backlog(struct tipc_link *l, struct sk_buff_head *xmitq)
 	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);
@@ -886,54 +909,25 @@ void tipc_link_advance_backlog(struct tipc_link *l, struct sk_buff_head *xmitq)
 		__skb_queue_tail(&l->transmq, skb);
 		__skb_queue_tail(xmitq, _skb);
 		TIPC_SKB_CB(skb)->ackers = l->ackers;
-		msg_set_ack(hdr, ack);
 		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)
+static void link_retransmit_failure(struct tipc_link *l, struct sk_buff *skb)
 {
-	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: %u\n", TIPC_SKB_CB(buf)->ackers);
-
-		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;
-	}
+	struct tipc_msg *hdr = buf_msg(skb);
+
+	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));
 }
 
 void tipc_link_retransmit(struct tipc_link *l_ptr, struct sk_buff *skb,
@@ -976,7 +970,7 @@ int tipc_link_retrans(struct tipc_link *l, u16 from, u16 to,
 	struct sk_buff *_skb, *skb = skb_peek(&l->transmq);
 	struct tipc_msg *hdr;
 	u16 ack = l->rcv_nxt - 1;
-	u16 bc_ack = l->owner->bclink.last_in;
+	u16 bc_ack = l->bc_rcvlink->rcv_nxt - 1;
 
 	if (!skb)
 		return 0;
@@ -1018,11 +1012,9 @@ int tipc_link_retrans(struct tipc_link *l, u16 from, u16 to,
  * 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:
@@ -1032,8 +1024,8 @@ 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:
@@ -1054,7 +1046,6 @@ 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;
@@ -1095,13 +1086,15 @@ 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->owner->net);
+		tipc_link_bc_init_rcv(l->bc_rcvlink, hdr);
+		tipc_bcast_unlock(l->owner->net);
 	}
 drop:
 	kfree_skb(skb);
@@ -1124,12 +1117,28 @@ 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
@@ -1151,6 +1160,9 @@ 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);
 }
@@ -1211,12 +1223,11 @@ 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;
@@ -1284,18 +1295,13 @@ void tipc_link_proto_xmit(struct tipc_link *l, u32 msg_typ, int probe_msg,
 	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))
@@ -1303,33 +1309,34 @@ 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);
@@ -1431,7 +1438,7 @@ 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))
@@ -1518,6 +1525,188 @@ 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);