Merge branch 'tipc-scalable-broadcast-NACK'

Jon Maloy says:

====================
tipc: improve broadcast NACK mechanism

The broadcast protocol has turned out to not scale well beyond 70-80
nodes, while it is now possible to build TIPC clusters of at least ten
times that size. This commit series improves the NACK/retransmission
mechanism of the broadcast protocol to make is at scalable as the rest
of TIPC.
====================

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

net/tipc/bcast.c

@@ -269,18 +269,19 @@ void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l, u32 acked)
  *
  * RCU is locked, no other locks set
  */
-void tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,
+int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,
-			 struct tipc_msg *hdr)
+			struct tipc_msg *hdr)
 {
 	struct sk_buff_head *inputq = &tipc_bc_base(net)->inputq;
 	struct sk_buff_head xmitq;
+	int rc = 0;
 
 	__skb_queue_head_init(&xmitq);
 
 	tipc_bcast_lock(net);
 	if (msg_type(hdr) == STATE_MSG) {
 		tipc_link_bc_ack_rcv(l, msg_bcast_ack(hdr), &xmitq);
-		tipc_link_bc_sync_rcv(l, hdr, &xmitq);
+		rc = tipc_link_bc_sync_rcv(l, hdr, &xmitq);
 	} else {
 		tipc_link_bc_init_rcv(l, hdr);
 	}
@@ -291,6 +292,7 @@ void tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,
 	/* Any socket wakeup messages ? */
 	if (!skb_queue_empty(inputq))
 		tipc_sk_rcv(net, inputq);
+	return rc;
 }
 
 /* tipc_bcast_add_peer - add a peer node to broadcast link and bearer

net/tipc/bcast.h

@@ -56,8 +56,8 @@ int  tipc_bcast_get_mtu(struct net *net);
 int tipc_bcast_xmit(struct net *net, struct sk_buff_head *list);
 int tipc_bcast_rcv(struct net *net, struct tipc_link *l, struct sk_buff *skb);
 void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l, u32 acked);
-void tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,
+int tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l,
-			 struct tipc_msg *hdr);
+			struct tipc_msg *hdr);
 int tipc_nl_add_bc_link(struct net *net, struct tipc_nl_msg *msg);
 int tipc_nl_bc_link_set(struct net *net, struct nlattr *attrs[]);
 int tipc_bclink_reset_stats(struct net *net);

net/tipc/link.c

@@ -181,7 +181,10 @@ struct tipc_link {
 	u16 acked;
 	struct tipc_link *bc_rcvlink;
 	struct tipc_link *bc_sndlink;
-	int nack_state;
+	unsigned long prev_retr;
+	u16 prev_from;
+	u16 prev_to;
+	u8 nack_state;
 	bool bc_peer_is_up;
 
 	/* Statistics */
@@ -202,6 +205,8 @@ enum {
 	BC_NACK_SND_SUPPRESS,
 };
 
+#define TIPC_BC_RETR_LIMIT 10   /* [ms] */
+
 /*
  * Interval between NACKs when packets arrive out of order
  */
@@ -237,8 +242,8 @@ 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);
 static void link_print(struct tipc_link *l, const char *str);
-static void tipc_link_build_nack_msg(struct tipc_link *l,
+static int tipc_link_build_nack_msg(struct tipc_link *l,
-				     struct sk_buff_head *xmitq);
+				    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);
@@ -367,6 +372,18 @@ int tipc_link_bc_peers(struct tipc_link *l)
 	return l->ackers;
 }
 
+u16 link_bc_rcv_gap(struct tipc_link *l)
+{
+	struct sk_buff *skb = skb_peek(&l->deferdq);
+	u16 gap = 0;
+
+	if (more(l->snd_nxt, l->rcv_nxt))
+		gap = l->snd_nxt - l->rcv_nxt;
+	if (skb)
+		gap = buf_seqno(skb) - l->rcv_nxt;
+	return gap;
+}
+
 void tipc_link_set_mtu(struct tipc_link *l, int mtu)
 {
 	l->mtu = mtu;
@@ -1135,7 +1152,10 @@ int tipc_link_build_state_msg(struct tipc_link *l, struct sk_buff_head *xmitq)
 		if (((l->rcv_nxt ^ tipc_own_addr(l->net)) & 0xf) != 0xf)
 			return 0;
 		l->rcv_unacked = 0;
-		return TIPC_LINK_SND_BC_ACK;
+
+		/* Use snd_nxt to store peer's snd_nxt in broadcast rcv link */
+		l->snd_nxt = l->rcv_nxt;
+		return TIPC_LINK_SND_STATE;
 	}
 
 	/* Unicast ACK */
@@ -1164,17 +1184,26 @@ void tipc_link_build_reset_msg(struct tipc_link *l, struct sk_buff_head *xmitq)
 }
 
 /* tipc_link_build_nack_msg: prepare link nack message for transmission
+ * Note that sending of broadcast NACK is coordinated among nodes, to
+ * reduce the risk of NACK storms towards the sender
  */
-static void tipc_link_build_nack_msg(struct tipc_link *l,
+static int tipc_link_build_nack_msg(struct tipc_link *l,
-				     struct sk_buff_head *xmitq)
+				    struct sk_buff_head *xmitq)
 {
 	u32 def_cnt = ++l->stats.deferred_recv;
+	int match1, match2;
 
-	if (link_is_bc_rcvlink(l))
+	if (link_is_bc_rcvlink(l)) {
-		return;
+		match1 = def_cnt & 0xf;
+		match2 = tipc_own_addr(l->net) & 0xf;
+		if (match1 == match2)
+			return TIPC_LINK_SND_STATE;
+		return 0;
+	}
 
 	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);
+	return 0;
 }
 
 /* tipc_link_rcv - process TIPC packets/messages arriving from off-node
@@ -1225,7 +1254,7 @@ int tipc_link_rcv(struct tipc_link *l, struct sk_buff *skb,
 		/* Defer delivery if sequence gap */
 		if (unlikely(seqno != rcv_nxt)) {
 			__tipc_skb_queue_sorted(defq, seqno, skb);
-			tipc_link_build_nack_msg(l, xmitq);
+			rc |= tipc_link_build_nack_msg(l, xmitq);
 			break;
 		}
 
@@ -1236,7 +1265,7 @@ int tipc_link_rcv(struct tipc_link *l, struct sk_buff *skb,
 			rc |= tipc_link_input(l, skb, l->inputq);
 		if (unlikely(++l->rcv_unacked >= TIPC_MIN_LINK_WIN))
 			rc |= tipc_link_build_state_msg(l, xmitq);
-		if (unlikely(rc & ~TIPC_LINK_SND_BC_ACK))
+		if (unlikely(rc & ~TIPC_LINK_SND_STATE))
 			break;
 	} while ((skb = __skb_dequeue(defq)));
 
@@ -1250,10 +1279,11 @@ 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 tipc_link *bcl = l->bc_rcvlink;
 	struct sk_buff *skb;
 	struct tipc_msg *hdr;
 	struct sk_buff_head *dfq = &l->deferdq;
-	bool node_up = link_is_up(l->bc_rcvlink);
+	bool node_up = link_is_up(bcl);
 	struct tipc_mon_state *mstate = &l->mon_state;
 	int dlen = 0;
 	void *data;
@@ -1281,7 +1311,7 @@ static void tipc_link_build_proto_msg(struct tipc_link *l, int mtyp, bool probe,
 	msg_set_net_plane(hdr, l->net_plane);
 	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_bcast_ack(hdr, bcl->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);
@@ -1291,6 +1321,7 @@ static void tipc_link_build_proto_msg(struct tipc_link *l, int mtyp, bool probe,
 
 	if (mtyp == STATE_MSG) {
 		msg_set_seq_gap(hdr, rcvgap);
+		msg_set_bc_gap(hdr, link_bc_rcv_gap(bcl));
 		msg_set_probe(hdr, probe);
 		tipc_mon_prep(l->net, data, &dlen, mstate, l->bearer_id);
 		msg_set_size(hdr, INT_H_SIZE + dlen);
@@ -1573,51 +1604,107 @@ void tipc_link_bc_init_rcv(struct tipc_link *l, struct tipc_msg *hdr)
 		l->rcv_nxt = peers_snd_nxt;
 }
 
+/* link_bc_retr eval()- check if the indicated range can be retransmitted now
+ * - Adjust permitted range if there is overlap with previous retransmission
+ */
+static bool link_bc_retr_eval(struct tipc_link *l, u16 *from, u16 *to)
+{
+	unsigned long elapsed = jiffies_to_msecs(jiffies - l->prev_retr);
+
+	if (less(*to, *from))
+		return false;
+
+	/* New retransmission request */
+	if ((elapsed > TIPC_BC_RETR_LIMIT) ||
+	    less(*to, l->prev_from) || more(*from, l->prev_to)) {
+		l->prev_from = *from;
+		l->prev_to = *to;
+		l->prev_retr = jiffies;
+		return true;
+	}
+
+	/* Inside range of previous retransmit */
+	if (!less(*from, l->prev_from) && !more(*to, l->prev_to))
+		return false;
+
+	/* Fully or partially outside previous range => exclude overlap */
+	if (less(*from, l->prev_from)) {
+		*to = l->prev_from - 1;
+		l->prev_from = *from;
+	}
+	if (more(*to, l->prev_to)) {
+		*from = l->prev_to + 1;
+		l->prev_to = *to;
+	}
+	l->prev_retr = jiffies;
+	return true;
+}
+
 /* 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,
+int tipc_link_bc_sync_rcv(struct tipc_link *l, struct tipc_msg *hdr,
-			   struct sk_buff_head *xmitq)
+			  struct sk_buff_head *xmitq)
 {
+	struct tipc_link *snd_l = l->bc_sndlink;
 	u16 peers_snd_nxt = msg_bc_snd_nxt(hdr);
+	u16 from = msg_bcast_ack(hdr) + 1;
+	u16 to = from + msg_bc_gap(hdr) - 1;
+	int rc = 0;
 
 	if (!link_is_up(l))
-		return;
+		return rc;
 
 	if (!msg_peer_node_is_up(hdr))
-		return;
+		return rc;
 
 	/* Open when peer ackowledges our bcast init msg (pkt #1) */
 	if (msg_ack(hdr))
 		l->bc_peer_is_up = true;
 
 	if (!l->bc_peer_is_up)
-		return;
+		return rc;
+
+	l->stats.recv_nacks++;
 
 	/* Ignore if peers_snd_nxt goes beyond receive window */
 	if (more(peers_snd_nxt, l->rcv_nxt + l->window))
-		return;
+		return rc;
+
+	if (link_bc_retr_eval(snd_l, &from, &to))
+		rc = tipc_link_retrans(snd_l, from, to, xmitq);
+
+	l->snd_nxt = peers_snd_nxt;
+	if (link_bc_rcv_gap(l))
+		rc |= TIPC_LINK_SND_STATE;
+
+	/* Return now if sender supports nack via STATE messages */
+	if (l->peer_caps & TIPC_BCAST_STATE_NACK)
+		return rc;
+
+	/* Otherwise, be backwards compatible */
 
 	if (!more(peers_snd_nxt, l->rcv_nxt)) {
 		l->nack_state = BC_NACK_SND_CONDITIONAL;
-		return;
+		return 0;
 	}
 
 	/* 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;
+		return 0;
 	}
 
 	/* 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;
+			return 0;
 	}
 
 	/* 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;
+	return 0;
 }
 
 void tipc_link_bc_ack_rcv(struct tipc_link *l, u16 acked,
@@ -1654,6 +1741,8 @@ void tipc_link_bc_ack_rcv(struct tipc_link *l, u16 acked,
 }
 
 /* tipc_link_bc_nack_rcv(): receive broadcast nack message
+ * This function is here for backwards compatibility, since
+ * no BCAST_PROTOCOL/STATE messages occur from TIPC v2.5.
  */
 int tipc_link_bc_nack_rcv(struct tipc_link *l, struct sk_buff *skb,
 			  struct sk_buff_head *xmitq)

net/tipc/link.h

@@ -63,7 +63,7 @@ enum {
 enum {
 	TIPC_LINK_UP_EVT       = 1,
 	TIPC_LINK_DOWN_EVT     = (1 << 1),
-	TIPC_LINK_SND_BC_ACK   = (1 << 2)
+	TIPC_LINK_SND_STATE    = (1 << 2)
 };
 
 /* Starting value for maximum packet size negotiation on unicast links
@@ -138,8 +138,8 @@ void tipc_link_bc_ack_rcv(struct tipc_link *l, u16 acked,
 void tipc_link_build_bc_sync_msg(struct tipc_link *l,
 				 struct sk_buff_head *xmitq);
 void tipc_link_bc_init_rcv(struct tipc_link *l, struct tipc_msg *hdr);
-void tipc_link_bc_sync_rcv(struct tipc_link *l,   struct tipc_msg *hdr,
+int tipc_link_bc_sync_rcv(struct tipc_link *l,   struct tipc_msg *hdr,
-			   struct sk_buff_head *xmitq);
+			  struct sk_buff_head *xmitq);
 int tipc_link_bc_nack_rcv(struct tipc_link *l, struct sk_buff *skb,
 			  struct sk_buff_head *xmitq);
 #endif

net/tipc/msg.h

@@ -719,6 +719,16 @@ static inline char *msg_media_addr(struct tipc_msg *m)
 	return (char *)&m->hdr[TIPC_MEDIA_INFO_OFFSET];
 }
 
+static inline u32 msg_bc_gap(struct tipc_msg *m)
+{
+	return msg_bits(m, 8, 0, 0x3ff);
+}
+
+static inline void msg_set_bc_gap(struct tipc_msg *m, u32 n)
+{
+	msg_set_bits(m, 8, 0, 0x3ff, n);
+}
+
 /*
  * Word 9
  */

net/tipc/node.c

@@ -1262,6 +1262,34 @@ void tipc_node_broadcast(struct net *net, struct sk_buff *skb)
 	kfree_skb(skb);
 }
 
+static void tipc_node_bc_sync_rcv(struct tipc_node *n, struct tipc_msg *hdr,
+				  int bearer_id, struct sk_buff_head *xmitq)
+{
+	struct tipc_link *ucl;
+	int rc;
+
+	rc = tipc_bcast_sync_rcv(n->net, n->bc_entry.link, hdr);
+
+	if (rc & TIPC_LINK_DOWN_EVT) {
+		tipc_bearer_reset_all(n->net);
+		return;
+	}
+
+	if (!(rc & TIPC_LINK_SND_STATE))
+		return;
+
+	/* If probe message, a STATE response will be sent anyway */
+	if (msg_probe(hdr))
+		return;
+
+	/* Produce a STATE message carrying broadcast NACK */
+	tipc_node_read_lock(n);
+	ucl = n->links[bearer_id].link;
+	if (ucl)
+		tipc_link_build_state_msg(ucl, xmitq);
+	tipc_node_read_unlock(n);
+}
+
 /**
  * tipc_node_bc_rcv - process TIPC broadcast packet arriving from off-node
  * @net: the applicable net namespace
@@ -1298,7 +1326,7 @@ static void tipc_node_bc_rcv(struct net *net, struct sk_buff *skb, int bearer_id
 	rc = tipc_bcast_rcv(net, be->link, skb);
 
 	/* Broadcast ACKs are sent on a unicast link */
-	if (rc & TIPC_LINK_SND_BC_ACK) {
+	if (rc & TIPC_LINK_SND_STATE) {
 		tipc_node_read_lock(n);
 		tipc_link_build_state_msg(le->link, &xmitq);
 		tipc_node_read_unlock(n);
@@ -1505,7 +1533,7 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b)
 
 	/* Ensure broadcast reception is in synch with peer's send state */
 	if (unlikely(usr == LINK_PROTOCOL))
-		tipc_bcast_sync_rcv(net, n->bc_entry.link, hdr);
+		tipc_node_bc_sync_rcv(n, hdr, bearer_id, &xmitq);
 	else if (unlikely(tipc_link_acked(n->bc_entry.link) != bc_ack))
 		tipc_bcast_ack_rcv(net, n->bc_entry.link, bc_ack);
 

net/tipc/node.h

@@ -1,7 +1,7 @@
 /*
  * net/tipc/node.h: Include file for TIPC node management routines
  *
- * Copyright (c) 2000-2006, 2014-2015, Ericsson AB
+ * Copyright (c) 2000-2006, 2014-2016, Ericsson AB
  * Copyright (c) 2005, 2010-2014, Wind River Systems
  * All rights reserved.
  *
@@ -45,11 +45,14 @@
 /* Optional capabilities supported by this code version
  */
 enum {
-	TIPC_BCAST_SYNCH   = (1 << 1),
+	TIPC_BCAST_SYNCH      = (1 << 1),
-	TIPC_BLOCK_FLOWCTL = (2 << 1)
+	TIPC_BCAST_STATE_NACK = (1 << 2),
+	TIPC_BLOCK_FLOWCTL    = (1 << 3)
 };
 
-#define TIPC_NODE_CAPABILITIES (TIPC_BCAST_SYNCH | TIPC_BLOCK_FLOWCTL)
+#define TIPC_NODE_CAPABILITIES (TIPC_BCAST_SYNCH | \
+				TIPC_BCAST_STATE_NACK | \
+				TIPC_BLOCK_FLOWCTL)
 #define INVALID_BEARER_ID -1
 
 void tipc_node_stop(struct net *net);