sctp: Bring SCTP_DELAYED_ACK socket option into API compliance

Brings delayed_ack socket option set/get into line with the latest ietf
socket extensions API draft, while maintaining backwards compatibility.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sctp/structs.h

@@ -300,6 +300,7 @@ struct sctp_sock {
 
 	/* The default SACK delay timeout for new associations. */
 	__u32 sackdelay;
+	__u32 sackfreq;
 
 	/* Flags controlling Heartbeat, SACK delay, and Path MTU Discovery. */
 	__u32 param_flags;
@@ -938,6 +939,7 @@ struct sctp_transport {
 
 	/* SACK delay timeout */
 	unsigned long sackdelay;
+	__u32 sackfreq;
 
 	/* When was the last time (in jiffies) that we heard from this
 	 * transport?  We use this to pick new active and retran paths.
@@ -1542,6 +1544,7 @@ struct sctp_association {
 		 *             : SACK's are not delayed (see Section 6).
 		 */
 		__u8    sack_needed;     /* Do we need to sack the peer? */
+		__u32	sack_cnt;
 
 		/* These are capabilities which our peer advertised.  */
 		__u8	ecn_capable;	 /* Can peer do ECN? */
@@ -1651,6 +1654,7 @@ struct sctp_association {
 
 	/* SACK delay timeout */
 	unsigned long sackdelay;
+	__u32 sackfreq;
 
 
 	unsigned long timeouts[SCTP_NUM_TIMEOUT_TYPES];

include/net/sctp/user.h

@@ -93,8 +93,9 @@ enum sctp_optname {
 #define SCTP_STATUS SCTP_STATUS
 	SCTP_GET_PEER_ADDR_INFO,
 #define SCTP_GET_PEER_ADDR_INFO SCTP_GET_PEER_ADDR_INFO
-	SCTP_DELAYED_ACK_TIME,
-#define SCTP_DELAYED_ACK_TIME SCTP_DELAYED_ACK_TIME
+	SCTP_DELAYED_ACK,
+#define SCTP_DELAYED_ACK_TIME SCTP_DELAYED_ACK
+#define SCTP_DELAYED_ACK SCTP_DELAYED_ACK
 	SCTP_CONTEXT,	/* Receive Context */
 #define SCTP_CONTEXT SCTP_CONTEXT
 	SCTP_FRAGMENT_INTERLEAVE,
@@ -618,13 +619,26 @@ struct sctp_authkeyid {
 };
 
 
-/* 7.1.23. Delayed Ack Timer (SCTP_DELAYED_ACK_TIME)
+/*
+ * 7.1.23.  Get or set delayed ack timer (SCTP_DELAYED_SACK)
  *
- *   This options will get or set the delayed ack timer.  The time is set
- *   in milliseconds.  If the assoc_id is 0, then this sets or gets the
- *   endpoints default delayed ack timer value.  If the assoc_id field is
- *   non-zero, then the set or get effects the specified association.
+ * This option will effect the way delayed acks are performed.  This
+ * option allows you to get or set the delayed ack time, in
+ * milliseconds.  It also allows changing the delayed ack frequency.
+ * Changing the frequency to 1 disables the delayed sack algorithm.  If
+ * the assoc_id is 0, then this sets or gets the endpoints default
+ * values.  If the assoc_id field is non-zero, then the set or get
+ * effects the specified association for the one to many model (the
+ * assoc_id field is ignored by the one to one model).  Note that if
+ * sack_delay or sack_freq are 0 when setting this option, then the
+ * current values will remain unchanged.
  */
+struct sctp_sack_info {
+	sctp_assoc_t	sack_assoc_id;
+	uint32_t	sack_delay;
+	uint32_t	sack_freq;
+};
+
 struct sctp_assoc_value {
     sctp_assoc_t            assoc_id;
     uint32_t                assoc_value;

net/sctp/associola.c

@@ -136,6 +136,7 @@ static struct sctp_association *sctp_association_init(struct sctp_association *a
 
 	/* Set association default SACK delay */
 	asoc->sackdelay = msecs_to_jiffies(sp->sackdelay);
+	asoc->sackfreq = sp->sackfreq;
 
 	/* Set the association default flags controlling
 	 * Heartbeat, SACK delay, and Path MTU Discovery.
@@ -261,6 +262,7 @@ static struct sctp_association *sctp_association_init(struct sctp_association *a
 	 * already received one packet.]
 	 */
 	asoc->peer.sack_needed = 1;
+	asoc->peer.sack_cnt = 0;
 
 	/* Assume that the peer will tell us if he recognizes ASCONF
 	 * as part of INIT exchange.
@@ -615,6 +617,7 @@ struct sctp_transport *sctp_assoc_add_peer(struct sctp_association *asoc,
 	 * association configured value.
 	 */
 	peer->sackdelay = asoc->sackdelay;
+	peer->sackfreq = asoc->sackfreq;
 
 	/* Enable/disable heartbeat, SACK delay, and path MTU discovery
 	 * based on association setting.

net/sctp/sm_sideeffect.c

@@ -190,20 +190,28 @@ static int sctp_gen_sack(struct sctp_association *asoc, int force,
 	 * unacknowledged DATA chunk. ...
 	 */
 	if (!asoc->peer.sack_needed) {
-		/* We will need a SACK for the next packet.  */
-		asoc->peer.sack_needed = 1;
+		asoc->peer.sack_cnt++;
 
 		/* Set the SACK delay timeout based on the
 		 * SACK delay for the last transport
 		 * data was received from, or the default
 		 * for the association.
 		 */
-		if (trans)
+		if (trans) {
+			/* We will need a SACK for the next packet.  */
+			if (asoc->peer.sack_cnt >= trans->sackfreq - 1)
+				asoc->peer.sack_needed = 1;
+
 			asoc->timeouts[SCTP_EVENT_TIMEOUT_SACK] =
 				trans->sackdelay;
-		else
+		} else {
+			/* We will need a SACK for the next packet.  */
+			if (asoc->peer.sack_cnt >= asoc->sackfreq - 1)
+				asoc->peer.sack_needed = 1;
+
 			asoc->timeouts[SCTP_EVENT_TIMEOUT_SACK] =
 				asoc->sackdelay;
+		}
 
 		/* Restart the SACK timer. */
 		sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_RESTART,
@@ -216,6 +224,7 @@ static int sctp_gen_sack(struct sctp_association *asoc, int force,
 			goto nomem;
 
 		asoc->peer.sack_needed = 0;
+		asoc->peer.sack_cnt = 0;
 
 		sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(sack));