mrp: add periodictimer to allow retries when packets get lost

MRP doesn't implement the periodictimer in 802.1Q, so it never retries
if packets get lost. I ran into this problem when MRP sent a MVRP
JoinIn before the interface was fully up. The JoinIn was lost, MRP
didn't retry, and MVRP registration failed.

Tested against Juniper QFabric switches

Signed-off-by: Noel Burton-Krahn <[e-mail]>
Acked-by: David Ward <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/mrp.h

···
 	struct mrp_application	*app;
 	struct net_device	*dev;
 	struct timer_list	join_timer;
+	struct timer_list	periodic_timer;
 
 	spinlock_t		lock;
 	struct sk_buff_head	queue;

net/802/mrp.c

···
 static unsigned int mrp_join_time __read_mostly = 200;
 module_param(mrp_join_time, uint, 0644);
 MODULE_PARM_DESC(mrp_join_time, "Join time in ms (default 200ms)");
+
+static unsigned int mrp_periodic_time __read_mostly = 1000;
+module_param(mrp_periodic_time, uint, 0644);
+MODULE_PARM_DESC(mrp_periodic_time, "Periodic time in ms (default 1s)");
+
 MODULE_LICENSE("GPL");
 
 static const u8
···
 	mrp_join_timer_arm(app);
 }
 
+static void mrp_periodic_timer_arm(struct mrp_applicant *app)
+{
+	mod_timer(&app->periodic_timer,
+		  jiffies + msecs_to_jiffies(mrp_periodic_time));
+}
+
+static void mrp_periodic_timer(unsigned long data)
+{
+	struct mrp_applicant *app = (struct mrp_applicant *)data;
+
+	spin_lock(&app->lock);
+	mrp_mad_event(app, MRP_EVENT_PERIODIC);
+	mrp_pdu_queue(app);
+	spin_unlock(&app->lock);
+
+	mrp_periodic_timer_arm(app);
+}
+
 static int mrp_pdu_parse_end_mark(struct sk_buff *skb, int *offset)
 {
 	__be16 endmark;
···
 	rcu_assign_pointer(dev->mrp_port->applicants[appl->type], app);
 	setup_timer(&app->join_timer, mrp_join_timer, (unsigned long)app);
 	mrp_join_timer_arm(app);
+	setup_timer(&app->periodic_timer, mrp_periodic_timer,
+		    (unsigned long)app);
+	mrp_periodic_timer_arm(app);
 	return 0;
 
 err3:
···
 	 * all pending messages before the applicant is gone.
 	 */
 	del_timer_sync(&app->join_timer);
+	del_timer_sync(&app->periodic_timer);
 
 	spin_lock_bh(&app->lock);
 	mrp_mad_event(app, MRP_EVENT_TX);