[SCTP] Reduce the size of struct sctp_ulpevent so that it fits in

       skb->cb even on 64-bit systems. 

Removed the redundant 'asoc' field in struct sctp_ulpevent and
instead use sinfo_assoc_id which is present within the other field
'sndrcvinfo'. This makes the size of struct sctp_ulpevent to be less
than the size of skb->cb[](48 bytes) even on 64-bit systems.

include/net/sctp/ulpevent.h

@@ -54,7 +54,6 @@
  * growing this structure as it is at the maximum limit now.
  */
 struct sctp_ulpevent {
-	struct sctp_association *asoc;
 	struct sctp_sndrcvinfo sndrcvinfo;
 	int msg_flags;
 	int iif;

net/sctp/ipv6.c

@@ -662,18 +662,20 @@ static void sctp_inet6_event_msgname(struct sctp_ulpevent *event,
 
 	if (msgname) {
 		union sctp_addr *addr;
+		struct sctp_association *asoc;
 
+		asoc = event->sndrcvinfo.sinfo_assoc_id;
 		sctp_inet6_msgname(msgname, addrlen);
 		sin6 = (struct sockaddr_in6 *)msgname;
-		sin6->sin6_port = htons(event->asoc->peer.port);
-		addr = &event->asoc->peer.primary_addr;
+		sin6->sin6_port = htons(asoc->peer.port);
+		addr = &asoc->peer.primary_addr;
 
 		/* Note: If we go to a common v6 format, this code
 		 * will change.
 		 */
 
 		/* Map ipv4 address into v4-mapped-on-v6 address.  */
-		if (sctp_sk(event->asoc->base.sk)->v4mapped &&
+		if (sctp_sk(asoc->base.sk)->v4mapped &&
 		    AF_INET == addr->sa.sa_family) {
 			sctp_v4_map_v6((union sctp_addr *)sin6);
 			sin6->sin6_addr.s6_addr32[3] =
@@ -681,7 +683,7 @@ static void sctp_inet6_event_msgname(struct sctp_ulpevent *event,
 			return;
 		}
 
-		sin6from = &event->asoc->peer.primary_addr.v6;
+		sin6from = &asoc->peer.primary_addr.v6;
 		ipv6_addr_copy(&sin6->sin6_addr, &sin6from->sin6_addr);
 		if (ipv6_addr_type(&sin6->sin6_addr) & IPV6_ADDR_LINKLOCAL)
 			sin6->sin6_scope_id = sin6from->sin6_scope_id;

net/sctp/protocol.c

@@ -691,10 +691,13 @@ static void sctp_inet_event_msgname(struct sctp_ulpevent *event, char *msgname,
 	struct sockaddr_in *sin, *sinfrom;
 
 	if (msgname) {
+		struct sctp_association *asoc;
+
+		asoc = event->sndrcvinfo.sinfo_assoc_id;
 		sctp_inet_msgname(msgname, addr_len);
 		sin = (struct sockaddr_in *)msgname;
-		sinfrom = &event->asoc->peer.primary_addr.v4;
-		sin->sin_port = htons(event->asoc->peer.port);
+		sinfrom = &asoc->peer.primary_addr.v4;
+		sin->sin_port = htons(asoc->peer.port);
 		sin->sin_addr.s_addr = sinfrom->sin_addr.s_addr;
 	}
 }

net/sctp/socket.c

@@ -1347,7 +1347,8 @@ SCTP_STATIC int sctp_recvmsg(struct kiocb *iocb, struct sock *sk,
 		 * rwnd by that amount. If all the data in the skb is read,
 		 * rwnd is updated when the event is freed.
 		 */
-		sctp_assoc_rwnd_increase(event->asoc, copied);
+		sctp_assoc_rwnd_increase(event->sndrcvinfo.sinfo_assoc_id,
+					 copied);
 		goto out;
 	} else if ((event->msg_flags & MSG_NOTIFICATION) ||
 		   (event->msg_flags & MSG_EOR))
@@ -4233,7 +4234,7 @@ static void sctp_sock_migrate(struct sock *oldsk, struct sock *newsk,
 	 */
 	sctp_skb_for_each(skb, &oldsk->sk_receive_queue, tmp) {
 		event = sctp_skb2event(skb);
-		if (event->asoc == assoc) {
+		if (event->sndrcvinfo.sinfo_assoc_id == assoc) {
 			__skb_unlink(skb, skb->list);
 			__skb_queue_tail(&newsk->sk_receive_queue, skb);
 		}
@@ -4262,7 +4263,7 @@ static void sctp_sock_migrate(struct sock *oldsk, struct sock *newsk,
 		 */
 		sctp_skb_for_each(skb, &oldsp->pd_lobby, tmp) {
 			event = sctp_skb2event(skb);
-			if (event->asoc == assoc) {
+			if (event->sndrcvinfo.sinfo_assoc_id == assoc) {
 				__skb_unlink(skb, skb->list);
 				__skb_queue_tail(queue, skb);
 			}

net/sctp/ulpevent.c

@@ -831,14 +831,14 @@ static inline void sctp_ulpevent_set_owner(struct sctp_ulpevent *event,
 	sctp_association_hold((struct sctp_association *)asoc);
 	skb = sctp_event2skb(event);
 	skb->sk = asoc->base.sk;
-	event->asoc = (struct sctp_association *)asoc;
+	event->sndrcvinfo.sinfo_assoc_id = sctp_assoc2id(asoc);
 	skb->destructor = sctp_stub_rfree;
 }
 
 /* A simple destructor to give up the reference to the association. */
 static inline void sctp_ulpevent_release_owner(struct sctp_ulpevent *event)
 {
-	sctp_association_put(event->asoc);
+	sctp_association_put(event->sndrcvinfo.sinfo_assoc_id);
 }
 
 /* Do accounting for bytes received and hold a reference to the association
@@ -880,7 +880,8 @@ static void sctp_ulpevent_release_data(struct sctp_ulpevent *event)
 	 */
 
 	skb = sctp_event2skb(event);
-	sctp_assoc_rwnd_increase(event->asoc, skb_headlen(skb));
+	sctp_assoc_rwnd_increase(event->sndrcvinfo.sinfo_assoc_id,
+				 skb_headlen(skb));
 
 	/* Don't forget the fragments. */
 	for (frag = skb_shinfo(skb)->frag_list; frag; frag = frag->next) {