tipc: simplify link timer handling

Prior to this commit, the link timer has been running at a "continuity
interval" of configured link tolerance/4. When a timer wakes up and
discovers that there has been no sign of life from the peer during the
previous interval, it divides its own timer interval by another factor
four, and starts sending one probe per new interval. When the configured
link tolerance time has passed without answer, i.e. after 16 unacked
probes, the link is declared faulty and reset.

This is unnecessary complex. It is sufficient to continue with the
original continuity interval, and instead reset the link after four
missed probe responses. This makes the timer handling in the link
simpler, and opens up for some planned later changes in this area.
This commit implements this change.
Reviewed-by: NRichard Alpe <richard.alpe@ericsson.com>
Reviewed-by: NErik Hugne <erik.hugne@ericsson.com>
Reviewed-by: NYing Xue <ying.xue@windriver.com>
Signed-off-by: NJon Maloy <jon.maloy@ericsson.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/tipc/link.c

@@ -528,7 +528,7 @@ static void link_state_event(struct tipc_link *l_ptr, unsigned int event)
 			l_ptr->fsm_msg_cnt = 0;
 			tipc_link_proto_xmit(l_ptr, STATE_MSG, 1, 0, 0, 0);
 			l_ptr->fsm_msg_cnt++;
-			link_set_timer(l_ptr, cont_intv / 4);
+			link_set_timer(l_ptr, cont_intv);
 			break;
 		case RESET_MSG:
 			pr_debug("%s<%s>, requested by peer\n",
@@ -579,7 +579,7 @@ static void link_state_event(struct tipc_link *l_ptr, unsigned int event)
 				tipc_link_proto_xmit(l_ptr, STATE_MSG,
 						     1, 0, 0, 0);
 				l_ptr->fsm_msg_cnt++;
-				link_set_timer(l_ptr, cont_intv / 4);
+				link_set_timer(l_ptr, cont_intv);
 			} else {	/* Link has failed */
 				pr_debug("%s<%s>, peer not responding\n",
 					 link_rst_msg, l_ptr->name);
@@ -1725,7 +1725,7 @@ static void link_set_supervision_props(struct tipc_link *l_ptr, u32 tol)
 
 	l_ptr->tolerance = tol;
 	l_ptr->cont_intv = msecs_to_jiffies(intv);
-	l_ptr->abort_limit = tol / (jiffies_to_msecs(l_ptr->cont_intv) / 4);
+	l_ptr->abort_limit = tol / (jiffies_to_msecs(l_ptr->cont_intv));
 }
 
 void tipc_link_set_queue_limits(struct tipc_link *l, u32 win)