tipc: optimize link synching mechanism

This commit along with the next one are to resolve the issues with the
link changeover mechanism. See that commit for details.

Basically, for the link synching, from now on, we will send only one
single ("dummy") SYNCH message to peer. The SYNCH message does not
contain any data, just a header conveying the synch point to the peer.

A new node capability flag ("TIPC_TUNNEL_ENHANCED") is introduced for
backward compatible!

Acked-by: Ying Xue <ying.xue@windriver.com>
Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Suggested-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Tuong Lien <tuong.t.lien@dektech.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 26 insertions, 0 deletions

diff --git a/net/tipc/link.c b/net/tipc/link.c
index 66d3a07bc571..e215b4ba6a4b 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -1665,6 +1665,7 @@ void tipc_link_tnl_prepare(struct tipc_link *l, struct tipc_link *tnl,
 	struct sk_buff_head *queue = &l->transmq;
 	struct sk_buff_head tmpxq, tnlq;
 	u16 pktlen, pktcnt, seqno = l->snd_nxt;
+	u16 syncpt;
 
 	if (!tnl)
 		return;
@@ -1684,6 +1685,31 @@ void tipc_link_tnl_prepare(struct tipc_link *l, struct tipc_link *tnl,
 	tipc_link_xmit(l, &tnlq, &tmpxq);
 	__skb_queue_purge(&tmpxq);
 
+	/* Link Synching:
+	 * From now on, send only one single ("dummy") SYNCH message
+	 * to peer. The SYNCH message does not contain any data, just
+	 * a header conveying the synch point to the peer.
+	 */
+	if (mtyp == SYNCH_MSG && (tnl->peer_caps & TIPC_TUNNEL_ENHANCED)) {
+		tnlskb = tipc_msg_create(TUNNEL_PROTOCOL, SYNCH_MSG,
+					 INT_H_SIZE, 0, l->addr,
+					 tipc_own_addr(l->net),
+					 0, 0, 0);
+		if (!tnlskb) {
+			pr_warn("%sunable to create dummy SYNCH_MSG\n",
+				link_co_err);
+			return;
+		}
+
+		hdr = buf_msg(tnlskb);
+		syncpt = l->snd_nxt + skb_queue_len(&l->backlogq) - 1;
+		msg_set_syncpt(hdr, syncpt);
+		msg_set_bearer_id(hdr, l->peer_bearer_id);
+		__skb_queue_tail(&tnlq, tnlskb);
+		tipc_link_xmit(tnl, &tnlq, xmitq);
+		return;
+	}
+
 	/* Initialize reusable tunnel packet header */
 	tipc_msg_init(tipc_own_addr(l->net), &tnlhdr, TUNNEL_PROTOCOL,
 		      mtyp, INT_H_SIZE, l->addr);