sctp: convert sack_needed and sack_generation to bits

commit 38ee8fb6 upstream.

They don't need to be any bigger than that and with this we start a new
bitfield for tracking association runtime stuff, like zero window
situation.
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[ kamal: 3.19-stable prereq for
  8a0d19c5 sctp: start t5 timer only when peer rwnd is 0 and local state is SHUTDOWN_PENDING ]
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

include/net/sctp/structs.h

@@ -773,10 +773,10 @@ struct sctp_transport {
 		hb_sent:1,
 
 		/* Is the Path MTU update pending on this tranport */
-		pmtu_pending:1;
+		pmtu_pending:1,
 
-	/* Has this transport moved the ctsn since we last sacked */
-	__u32 sack_generation;
+		/* Has this transport moved the ctsn since we last sacked */
+		sack_generation:1;
 	u32 dst_cookie;
 
 	struct flowi fl;
@@ -1481,19 +1481,19 @@ struct sctp_association {
 			prsctp_capable:1,   /* Can peer do PR-SCTP? */
 			auth_capable:1;     /* Is peer doing SCTP-AUTH? */
 
-		/* Ack State   : This flag indicates if the next received
+		/* sack_needed : This flag indicates if the next received
 		 *             : packet is to be responded to with a
-		 *             : SACK. This is initializedto 0.  When a packet
-		 *             : is received it is incremented. If this value
+		 *             : SACK. This is initialized to 0.  When a packet
+		 *             : is received sack_cnt is incremented. If this value
 		 *             : reaches 2 or more, a SACK is sent and the
 		 *             : value is reset to 0. Note: This is used only
 		 *             : when no DATA chunks are received out of
 		 *             : order.  When DATA chunks are out of order,
 		 *             : SACK's are not delayed (see Section 6).
 		 */
-		__u8    sack_needed;     /* Do we need to sack the peer? */
+		__u8    sack_needed:1,     /* Do we need to sack the peer? */
+			sack_generation:1;
 		__u32	sack_cnt;
-		__u32	sack_generation;
 
 		__u32   adaptation_ind;	 /* Adaptation Code point. */