tipc: make link mtu easily accessible from socket

Message fragmentation is currently performed at link level, inside
the protection of node_lock. This potentially binds up the sending
link structure for a long time, instead of letting it do other tasks,
such as handle reception of new packets.

In this commit, we make the MTUs of each active link become easily
accessible from the socket level, i.e., without taking any spinlock
or dereferencing the target link pointer. This way, we make it possible
to perform fragmentation in the sending socket, before sending the
whole fragment chain to the link for transport.

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

1 files changed, 21 insertions, 4 deletions

diff --git a/net/tipc/node.c b/net/tipc/node.c
index 5b44c3041be4..d959343043fd 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -1,7 +1,7 @@
 /*
  * net/tipc/node.c: TIPC node management routines
  *
- * Copyright (c) 2000-2006, 2012 Ericsson AB
+ * Copyright (c) 2000-2006, 2012-2014, Ericsson AB
  * Copyright (c) 2005-2006, 2010-2014, Wind River Systems
  * All rights reserved.
  *
@@ -155,21 +155,25 @@ void tipc_node_link_up(struct tipc_node *n_ptr, struct tipc_link *l_ptr)
 	if (!active[0]) {
 		active[0] = active[1] = l_ptr;
 		node_established_contact(n_ptr);
-		return;
+		goto exit;
 	}
 	if (l_ptr->priority < active[0]->priority) {
 		pr_info("New link <%s> becomes standby\n", l_ptr->name);
-		return;
+		goto exit;
 	}
 	tipc_link_dup_queue_xmit(active[0], l_ptr);
 	if (l_ptr->priority == active[0]->priority) {
 		active[0] = l_ptr;
-		return;
+		goto exit;
 	}
 	pr_info("Old link <%s> becomes standby\n", active[0]->name);
 	if (active[1] != active[0])
 		pr_info("Old link <%s> becomes standby\n", active[1]->name);
 	active[0] = active[1] = l_ptr;
+exit:
+	/* Leave room for changeover header when returning 'mtu' to users: */
+	n_ptr->act_mtus[0] = active[0]->max_pkt - INT_H_SIZE;
+	n_ptr->act_mtus[1] = active[1]->max_pkt - INT_H_SIZE;
 }
 
 /**
@@ -229,6 +233,19 @@ void tipc_node_link_down(struct tipc_node *n_ptr, struct tipc_link *l_ptr)
 		tipc_link_failover_send_queue(l_ptr);
 	else
 		node_lost_contact(n_ptr);
+
+	/* Leave room for changeover header when returning 'mtu' to users: */
+	if (active[0]) {
+		n_ptr->act_mtus[0] = active[0]->max_pkt - INT_H_SIZE;
+		n_ptr->act_mtus[1] = active[1]->max_pkt - INT_H_SIZE;
+		return;
+	}
+
+	/* Loopback link went down? No fragmentation needed from now on. */
+	if (n_ptr->addr == tipc_own_addr) {
+		n_ptr->act_mtus[0] = MAX_MSG_SIZE;
+		n_ptr->act_mtus[1] = MAX_MSG_SIZE;
+	}
 }
 
 int tipc_node_active_links(struct tipc_node *n_ptr)