tipc: introduce new link protocol msg create function

As a preparation for later changes, we introduce a new function
tipc_link_build_proto_msg(). Instead of actually sending the created
protocol message, it only creates it and adds it to the head of a
skb queue provided by the caller.

Since we still need the existing function tipc_link_protocol_xmit()
for a while, we redesign it to make use of the new function.

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

net/tipc/link.c

@@ -129,6 +129,9 @@ static void tipc_link_proto_rcv(struct tipc_link *link,
 				struct sk_buff *skb);
 static void link_set_supervision_props(struct tipc_link *l_ptr, u32 tol);
 static void link_state_event(struct tipc_link *l_ptr, u32 event);
+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_reset_statistics(struct tipc_link *l_ptr);
 static void link_print(struct tipc_link *l_ptr, const char *str);
 static void tipc_link_sync_xmit(struct tipc_link *l);
@@ -1323,77 +1326,21 @@ static void link_handle_out_of_seq_msg(struct tipc_link *l_ptr,
 /*
  * Send protocol message to the other endpoint.
  */
-void tipc_link_proto_xmit(struct tipc_link *l_ptr, u32 msg_typ, int probe_msg,
+void tipc_link_proto_xmit(struct tipc_link *l, u32 msg_typ, int probe_msg,
 			  u32 gap, u32 tolerance, u32 priority)
 {
-	struct sk_buff *buf = NULL;
-	struct tipc_msg *msg = l_ptr->pmsg;
-	u32 msg_size = sizeof(l_ptr->proto_msg);
-	int r_flag;
-	u16 last_rcv;
+	struct sk_buff *skb = NULL;
+	struct sk_buff_head xmitq;
 
-	/* Don't send protocol message during link failover */
-	if (l_ptr->exec_mode == TIPC_LINK_BLOCKED)
-		return;
-
-	/* Abort non-RESET send if communication with node is prohibited */
-	if ((tipc_node_blocked(l_ptr->owner)) && (msg_typ != RESET_MSG))
-		return;
-
-	/* Create protocol message with "out-of-sequence" sequence number */
-	msg_set_type(msg, msg_typ);
-	msg_set_net_plane(msg, l_ptr->net_plane);
-	msg_set_bcast_ack(msg, l_ptr->owner->bclink.last_in);
-	msg_set_last_bcast(msg, tipc_bclink_get_last_sent(l_ptr->owner->net));
-
-	if (msg_typ == STATE_MSG) {
-		u16 next_sent = l_ptr->snd_nxt;
-
-		if (!tipc_link_is_up(l_ptr))
-			return;
-		msg_set_next_sent(msg, next_sent);
-		if (!skb_queue_empty(&l_ptr->deferdq)) {
-			last_rcv = buf_seqno(skb_peek(&l_ptr->deferdq));
-			gap = mod(last_rcv - l_ptr->rcv_nxt);
-		}
-		msg_set_seq_gap(msg, gap);
-		if (gap)
-			l_ptr->stats.sent_nacks++;
-		msg_set_link_tolerance(msg, tolerance);
-		msg_set_linkprio(msg, priority);
-		msg_set_max_pkt(msg, l_ptr->mtu);
-		msg_set_ack(msg, mod(l_ptr->rcv_nxt - 1));
-		msg_set_probe(msg, probe_msg != 0);
-		if (probe_msg)
-			l_ptr->stats.sent_probes++;
-		l_ptr->stats.sent_states++;
-	} else {		/* RESET_MSG or ACTIVATE_MSG */
-		msg_set_ack(msg, mod(l_ptr->failover_checkpt - 1));
-		msg_set_seq_gap(msg, 0);
-		msg_set_next_sent(msg, 1);
-		msg_set_probe(msg, 0);
-		msg_set_link_tolerance(msg, l_ptr->tolerance);
-		msg_set_linkprio(msg, l_ptr->priority);
-		msg_set_max_pkt(msg, l_ptr->advertised_mtu);
-	}
-
-	r_flag = (l_ptr->owner->working_links > tipc_link_is_up(l_ptr));
-	msg_set_redundant_link(msg, r_flag);
-	msg_set_linkprio(msg, l_ptr->priority);
-	msg_set_size(msg, msg_size);
-
-	msg_set_seqno(msg, mod(l_ptr->snd_nxt + (0xffff / 2)));
-
-	buf = tipc_buf_acquire(msg_size);
-	if (!buf)
+	__skb_queue_head_init(&xmitq);
+	tipc_link_build_proto_msg(l, msg_typ, probe_msg, gap,
+				  tolerance, priority, &xmitq);
+	skb = __skb_dequeue(&xmitq);
+	if (!skb)
 		return;
-
-	skb_copy_to_linear_data(buf, msg, sizeof(l_ptr->proto_msg));
-	buf->priority = TC_PRIO_CONTROL;
-	tipc_bearer_send(l_ptr->owner->net, l_ptr->bearer_id, buf,
-			 &l_ptr->media_addr);
-	l_ptr->rcv_unacked = 0;
-	kfree_skb(buf);
+	tipc_bearer_send(l->owner->net, l->bearer_id, skb, &l->media_addr);
+	l->rcv_unacked = 0;
+	kfree_skb(skb);
 }
 
 /*
@@ -1514,6 +1461,69 @@ static void tipc_link_proto_rcv(struct tipc_link *l_ptr,
 	kfree_skb(buf);
 }
 
+/* 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;
+
+	/* Don't send protocol message during reset or link failover */
+	if (l->exec_mode == TIPC_LINK_BLOCKED)
+		return;
+
+	/* Abort non-RESET send if communication with node is prohibited */
+	if ((tipc_node_blocked(l->owner)) && (mtyp != RESET_MSG))
+		return;
+
+	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_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);
+
+	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;
+		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++;
+	} else {
+		/* RESET_MSG or ACTIVATE_MSG */
+		msg_set_max_pkt(hdr, l->advertised_mtu);
+		msg_set_ack(hdr, l->failover_checkpt - 1);
+		msg_set_next_sent(hdr, 1);
+	}
+	skb = tipc_buf_acquire(msg_size(hdr));
+	if (!skb)
+		return;
+	skb_copy_to_linear_data(skb, hdr, msg_size(hdr));
+	skb->priority = TC_PRIO_CONTROL;
+	__skb_queue_head(xmitq, skb);
+}
 
 /* tipc_link_tunnel_xmit(): Tunnel one packet via a link belonging to
  * a different bearer. Owner node is locked.