tipc: Add support for customized subscription overlap handling

This patch enables TIPC's topology server code to do customized
overlap detection handling on a per-subscription basis.  (This
capability is needed to support the upcoming introduction of
multi-cluster TIPC networks.)
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/subscr.c

@@ -157,7 +157,8 @@ void tipc_subscr_report_overlap(struct subscription *sub,
 		return;
 	if (!must && !(sub->filter & TIPC_SUB_PORTS))
 		return;
-	subscr_send_event(sub, found_lower, found_upper, event, port_ref, node);
+
+	sub->event_cb(sub, found_lower, found_upper, event, port_ref, node);
 }
 
 /**
@@ -372,6 +373,7 @@ static void subscr_subscribe(struct tipc_subscr *s,
 		subscr_terminate(subscriber);
 		return;
 	}
+	sub->event_cb = subscr_send_event;
 	memcpy(&sub->evt.s, s, sizeof(struct tipc_subscr));
 	INIT_LIST_HEAD(&sub->subscription_list);
 	INIT_LIST_HEAD(&sub->nameseq_list);

net/tipc/subscr.h

@@ -37,11 +37,18 @@
 #ifndef _TIPC_SUBSCR_H
 #define _TIPC_SUBSCR_H
 
+struct subscription;
+
+typedef void (*tipc_subscr_event) (struct subscription *sub,
+				   u32 found_lower, u32 found_upper,
+				   u32 event, u32 port_ref, u32 node);
+
 /**
  * struct subscription - TIPC network topology subscription object
  * @seq: name sequence associated with subscription
  * @timeout: duration of subscription (in ms)
  * @filter: event filtering to be done for subscription
+ * @event_cb: routine invoked when a subscription event is detected
  * @evt: template for events generated by subscription
  * @subscription_list: adjacent subscriptions in subscriber's subscription list
  * @nameseq_list: adjacent subscriptions in name sequence's subscription list
@@ -53,6 +60,7 @@ struct subscription {
 	struct tipc_name_seq seq;
 	u32 timeout;
 	u32 filter;
+	tipc_subscr_event event_cb;
 	struct tipc_event evt;
 	struct list_head subscription_list;
 	struct list_head nameseq_list;