tipc: send out RESET immediately when link goes down

When a link is taken down because of a node local event, such as
disabling of a bearer or an interface, we currently leave it to the
peer node to discover the broken communication. The default time for
such failure discovery is 1.5-2 seconds.

If we instead allow the terminating link endpoint to send out a RESET
message at the moment it is reset, we can achieve the impression that
both endpoints are going down instantly. Since this is a very common
scenario, we find it worthwhile to make this small modification.

Apart from letting the link produce the said message, we also have to
ensure that the interface is able to transmit it before TIPC is
detached. We do this by performing the disabling of a bearer in three
steps:

1) Disable reception of TIPC packets from the interface in question.
2) Take down the links, while allowing them so send out a RESET message.
3) Disable transmission of TIPC packets on the interface.

Apart from this, we now have to react on the NETDEV_GOING_DOWN event,
instead of as currently the NEDEV_DOWN event, to ensure that such
transmission is possible during the teardown phase.

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

1 files changed, 3 insertions, 5 deletions

diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index ce9f7bfc0b92..82b278668ab7 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -362,6 +362,7 @@ static void bearer_disable(struct net *net, struct tipc_bearer *b_ptr)
 	b_ptr->media->disable_media(b_ptr);
 
 	tipc_node_delete_links(net, b_ptr->identity);
+	RCU_INIT_POINTER(b_ptr->media_ptr, NULL);
 	if (b_ptr->link_req)
 		tipc_disc_delete(b_ptr->link_req);
 
@@ -399,16 +400,13 @@ int tipc_enable_l2_media(struct net *net, struct tipc_bearer *b,
 
 /* tipc_disable_l2_media - detach TIPC bearer from an L2 interface
  *
- * Mark L2 bearer as inactive so that incoming buffers are thrown away,
- * then get worker thread to complete bearer cleanup.  (Can't do cleanup
- * here because cleanup code needs to sleep and caller holds spinlocks.)
+ * Mark L2 bearer as inactive so that incoming buffers are thrown away
  */
 void tipc_disable_l2_media(struct tipc_bearer *b)
 {
 	struct net_device *dev;
 
 	dev = (struct net_device *)rtnl_dereference(b->media_ptr);
-	RCU_INIT_POINTER(b->media_ptr, NULL);
 	RCU_INIT_POINTER(dev->tipc_ptr, NULL);
 	synchronize_net();
 	dev_put(dev);
@@ -554,7 +552,7 @@ static int tipc_l2_device_event(struct notifier_block *nb, unsigned long evt,
 	case NETDEV_CHANGE:
 		if (netif_carrier_ok(dev))
 			break;
-	case NETDEV_DOWN:
+	case NETDEV_GOING_DOWN:
 	case NETDEV_CHANGEMTU:
 		tipc_reset_bearer(net, b_ptr);
 		break;