tipc: add back link trace events

In the previous commit ("tipc: add Gap ACK blocks support for broadcast
link"), we have removed the following link trace events due to the code
changes:

- tipc_link_bc_ack
- tipc_link_retrans

This commit adds them back along with some minor changes to adapt to
the new code.
Acked-by: Ying Xue <ying.xue@windriver.com>
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Tuong Lien <tuong.t.lien@dektech.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/link.c

@@ -1504,6 +1504,8 @@ static int tipc_link_advance_transmq(struct tipc_link *l, struct tipc_link *r,
 	bool is_uc = !link_is_bc_sndlink(l);
 	bool bc_has_acked = false;
 
+	trace_tipc_link_retrans(r, acked + 1, acked + gap, &l->transmq);
+
 	/* Determine Gap ACK blocks if any for the particular link */
 	if (ga && is_uc) {
 		/* Get the Gap ACKs, uc part */
@@ -2410,6 +2412,7 @@ int tipc_link_bc_ack_rcv(struct tipc_link *r, u16 acked, u16 gap,
 	if (less(acked, r->acked) || (acked == r->acked && !gap && !ga))
 		return 0;
 
+	trace_tipc_link_bc_ack(r, acked, gap, &l->transmq);
 	tipc_link_advance_transmq(l, r, acked, gap, ga, xmitq, &unused, &rc);
 
 	tipc_link_advance_backlog(l, xmitq);

net/tipc/trace.h

@@ -299,8 +299,10 @@ DECLARE_EVENT_CLASS(tipc_link_transmq_class,
 		__entry->from = f;
 		__entry->to = t;
 		__entry->len = skb_queue_len(tq);
-		__entry->fseqno = msg_seqno(buf_msg(skb_peek(tq)));
-		__entry->lseqno = msg_seqno(buf_msg(skb_peek_tail(tq)));
+		__entry->fseqno = __entry->len ?
+				  msg_seqno(buf_msg(skb_peek(tq))) : 0;
+		__entry->lseqno = __entry->len ?
+				  msg_seqno(buf_msg(skb_peek_tail(tq))) : 0;
 	),
 
 	TP_printk("<%s> retrans req: [%u-%u] transmq: %u [%u-%u]\n",
@@ -308,15 +310,16 @@ DECLARE_EVENT_CLASS(tipc_link_transmq_class,
 		  __entry->len, __entry->fseqno, __entry->lseqno)
 );
 
-DEFINE_EVENT(tipc_link_transmq_class, tipc_link_retrans,
+DEFINE_EVENT_CONDITION(tipc_link_transmq_class, tipc_link_retrans,
 	TP_PROTO(struct tipc_link *r, u16 f, u16 t, struct sk_buff_head *tq),
-	TP_ARGS(r, f, t, tq)
+	TP_ARGS(r, f, t, tq),
+	TP_CONDITION(less_eq(f, t))
 );
 
 DEFINE_EVENT_PRINT(tipc_link_transmq_class, tipc_link_bc_ack,
 	TP_PROTO(struct tipc_link *r, u16 f, u16 t, struct sk_buff_head *tq),
 	TP_ARGS(r, f, t, tq),
-	TP_printk("<%s> acked: [%u-%u] transmq: %u [%u-%u]\n",
+	TP_printk("<%s> acked: %u gap: %u transmq: %u [%u-%u]\n",
 		  __entry->name, __entry->from, __entry->to,
 		  __entry->len, __entry->fseqno, __entry->lseqno)
 );