tipc: let first message on link be a state message

According to the link FSM, a received traffic packet can take a link
from state ESTABLISHING to ESTABLISHED, but the link can still not be
fully set up in one atomic operation. This means that even if the the
very first packet on the link is a traffic packet with sequence number
1 (one), it has to be dropped and retransmitted.

This can be avoided if we let the mentioned packet be preceded by a
LINK_PROTOCOL/STATE message, which takes up the endpoint before the
arrival of the traffic.

We add this small feature in this commit.

This is a fully compatible change.

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

1 files changed, 4 insertions, 1 deletions

diff --git a/net/tipc/node.c b/net/tipc/node.c
index b00e12cda66c..68d9f7b8485c 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -545,6 +545,9 @@ static void __tipc_node_link_up(struct tipc_node *n, int bearer_id,
         pr_debug("Established link <%s> on network plane %c\n",
                  tipc_link_name(nl), tipc_link_plane(nl));
 
+        /* Ensure that a STATE message goes first */
+        tipc_link_build_state_msg(nl, xmitq);
+
         /* First link? => give it both slots */
         if (!ol) {
                 *slot0 = bearer_id;
@@ -1283,7 +1286,7 @@ static void tipc_node_bc_rcv(struct net *net, struct sk_buff *skb, int bearer_id
         /* Broadcast ACKs are sent on a unicast link */
         if (rc & TIPC_LINK_SND_BC_ACK) {
                 tipc_node_read_lock(n);
-                tipc_link_build_ack_msg(le->link, &xmitq);
+                tipc_link_build_state_msg(le->link, &xmitq);
                 tipc_node_read_unlock(n);
         }