SCTP: Use hashed lookup when looking for an association.

A SCTP endpoint may have a lot of associations on them and walking
the list is fairly inefficient.  Instead, use a hashed lookup,
and filter out the hash list based on the endopoing we already have.
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

net/sctp/endpointola.c

@@ -328,24 +328,34 @@ static struct sctp_association *__sctp_endpoint_lookup_assoc(
 	const union sctp_addr *paddr,
 	struct sctp_transport **transport)
 {
+	struct sctp_association *asoc = NULL;
+	struct sctp_transport *t = NULL;
+	struct sctp_hashbucket *head;
+	struct sctp_ep_common *epb;
+	int hash;
 	int rport;
-	struct sctp_association *asoc;
-	struct list_head *pos;
 
+	*transport = NULL;
 	rport = ntohs(paddr->v4.sin_port);
 
-	list_for_each(pos, &ep->asocs) {
-		asoc = list_entry(pos, struct sctp_association, asocs);
-		if (rport == asoc->peer.port) {
-			*transport = sctp_assoc_lookup_paddr(asoc, paddr);
-
-			if (*transport)
-				return asoc;
+	hash = sctp_assoc_hashfn(ep->base.bind_addr.port, rport);
+	head = &sctp_assoc_hashtable[hash];
+	read_lock(&head->lock);
+	for (epb = head->chain; epb; epb = epb->next) {
+		asoc = sctp_assoc(epb);
+		if (asoc->ep != ep || rport != asoc->peer.port)
+			goto next;
+
+		t = sctp_assoc_lookup_paddr(asoc, paddr);
+		if (t) {
+			*transport = t;
+			break;
 		}
+next:
+		asoc = NULL;
 	}
-
-	*transport = NULL;
-	return NULL;
+	read_unlock(&head->lock);
+	return asoc;
 }
 
 /* Lookup association on an endpoint based on a peer address.  BH-safe.  */