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, 17 insertions, 0 deletions

diff --git a/net/tipc/node.h b/net/tipc/node.h
index 9087063793f2..b61716a8218e 100644
--- a/net/tipc/node.h
+++ b/net/tipc/node.h
@@ -41,6 +41,7 @@
 #include "addr.h"
 #include "net.h"
 #include "bearer.h"
+#include "msg.h"
 
 /*
  * Out-of-range value for node signature
@@ -105,6 +106,7 @@ struct tipc_node {
         spinlock_t lock;
         struct hlist_node hash;
         struct tipc_link *active_links[2];
+        u32 act_mtus[2];
         struct tipc_link *links[MAX_BEARERS];
         unsigned int action_flags;
         struct tipc_node_bclink bclink;
@@ -143,4 +145,19 @@ static inline bool tipc_node_blocked(struct tipc_node *node)
                 TIPC_NOTIFY_NODE_DOWN | TIPC_WAIT_OWN_LINKS_DOWN));
 }
 
+static inline uint tipc_node_get_mtu(u32 addr, u32 selector)
+{
+        struct tipc_node *node;
+        u32 mtu;
+
+        node = tipc_node_find(addr);
+
+        if (likely(node))
+                mtu = node->act_mtus[selector & 1];
+        else
+                mtu = MAX_MSG_SIZE;
+
+        return mtu;
+}
+
 #endif