[SCTP] Bundle SACK with outgoing DATA.

If we are sending DATA, bundle a SACK.  Otherwise, we end up 
always waiting for the delayed SACK rules (timer or every other
packet rule) to kick in.   

include/net/sctp/sctp.h

@@ -421,6 +421,15 @@ static inline __s32 sctp_jitter(__u32 rto)
 	return ret;
 }
 
+/* Break down data chunks at this point.  */
+static inline int sctp_frag_point(int pmtu)
+{
+	pmtu -= SCTP_IP_OVERHEAD + sizeof(struct sctp_data_chunk);
+	pmtu -= sizeof(struct sctp_sack_chunk);
+
+	return pmtu;
+}
+
 /* Walk through a list of TLV parameters.  Don't trust the
  * individual parameter lengths and instead depend on
  * the chunk length to indicate when to stop.  Make sure

include/net/sctp/structs.h

@@ -590,13 +590,16 @@ struct sctp_packet {
 	/* This packet should advertise ECN capability to the network
 	 * via the ECT bit.
 	 */
-	int ecn_capable;
+	char ecn_capable;
 
 	/* This packet contains a COOKIE-ECHO chunk. */
-	int has_cookie_echo;
+	char has_cookie_echo;
+
+	/* This packet containsa SACK chunk. */
+	char has_sack; 
 
 	/* SCTP cannot fragment this packet. So let ip fragment it. */
-	int ipfragok;
+	char ipfragok;
 
 	int malloced;
 };

net/sctp/associola.c

@@ -421,8 +421,7 @@ struct sctp_transport *sctp_assoc_add_peer(struct sctp_association *asoc,
 	SCTP_DEBUG_PRINTK("sctp_assoc_add_peer:association %p PMTU set to "
 			  "%d\n", asoc, asoc->pmtu);
 
-	asoc->frag_point = asoc->pmtu;
-	asoc->frag_point -= SCTP_IP_OVERHEAD + sizeof(struct sctp_data_chunk);
+	asoc->frag_point = sctp_frag_point(asoc->pmtu);
 
 	/* The asoc->peer.port might not be meaningful yet, but
 	 * initialize the packet structure anyway.
@@ -658,31 +657,20 @@ int sctp_cmp_addr_exact(const union sctp_addr *ss1,
 }
 
 /* Return an ecne chunk to get prepended to a packet.
- * Note:  We are sly and return a shared, prealloced chunk.
+ * Note:  We are sly and return a shared, prealloced chunk.  FIXME:
+ * No we don't, but we could/should.
  */
-sctp_chunk_t *sctp_get_ecne_prepend(sctp_association_t *asoc)
+sctp_chunk_t *sctp_get_ecne_prepend(struct sctp_association *asoc)
 {
-	sctp_chunk_t *chunk;
-	int need_ecne;
-	__u32 lowest_tsn;
-
-	/* Can be called from task or bh.   Both need_ecne and
-	 * last_ecne_tsn are written during bh.
-	 */
-	need_ecne = asoc->need_ecne;
-	lowest_tsn = asoc->last_ecne_tsn;
-
-	if (need_ecne) {
-		chunk = sctp_make_ecne(asoc, lowest_tsn);
+	struct sctp_chunk *chunk;
 
-		/* ECNE is not mandatory to the flow.  Being unable to
-		 * alloc mem is not deadly.  We are just unable to help
-		 * out the network.  If we run out of memory, just return
-		 * NULL.
+	/* Send ECNE if needed. 
+	 * Not being able to allocate a chunk here is not deadly. 
 	 */
-	} else {
+	if (asoc->need_ecne)
+		chunk = sctp_make_ecne(asoc, asoc->last_ecne_tsn);
+	else
 		chunk = NULL;
-	}
 	
 	return chunk;
 }
@@ -986,8 +974,7 @@ void sctp_assoc_sync_pmtu(sctp_association_t *asoc)
 
 	if (pmtu) {
 		asoc->pmtu = pmtu;
-		asoc->frag_point = pmtu - (SCTP_IP_OVERHEAD +
-					   sizeof(sctp_data_chunk_t));
+		asoc->frag_point = sctp_frag_point(pmtu);
 	}
 
 	SCTP_DEBUG_PRINTK("%s: asoc:%p, pmtu:%d, frag_point:%d\n",

net/sctp/output.c

@@ -79,6 +79,7 @@ struct sctp_packet *sctp_packet_config(struct sctp_packet *packet,
 	packet->ecn_capable = ecn_capable;
 	packet->get_prepend_chunk = prepend_handler;
 	packet->has_cookie_echo = 0;
+	packet->has_sack = 0;
 	packet->ipfragok = 0;
 
 	/* We might need to call the prepend_handler right away.  */
@@ -100,6 +101,7 @@ struct sctp_packet *sctp_packet_init(struct sctp_packet *packet,
 	packet->ecn_capable = 0;
 	packet->get_prepend_chunk = NULL;
 	packet->has_cookie_echo = 0;
+	packet->has_sack = 0;
 	packet->ipfragok = 0;
 	packet->malloced = 0;
 	sctp_packet_reset(packet);
@@ -155,6 +157,37 @@ sctp_xmit_t sctp_packet_transmit_chunk(struct sctp_packet *packet,
 	return retval;
 }
 
+/* Try to bundle a SACK with the packet. */
+static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt,
+					   struct sctp_chunk *chunk)
+{
+	sctp_xmit_t retval = SCTP_XMIT_OK;
+
+	/* If sending DATA and haven't aleady bundled a SACK, try to
+	 * bundle one in to the packet.
+	 */
+	if (sctp_chunk_is_data(chunk) && !pkt->has_sack && 
+	    !pkt->has_cookie_echo) {
+		struct sctp_association *asoc;
+		asoc = pkt->transport->asoc;
+			
+		if (asoc->a_rwnd > asoc->rwnd) {
+			struct sctp_chunk *sack;
+			asoc->a_rwnd = asoc->rwnd;
+			sack = sctp_make_sack(asoc);
+			if (sack) {
+				struct timer_list *timer;
+				retval = sctp_packet_append_chunk(pkt, sack);
+				asoc->peer.sack_needed = 0;
+				timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
+				if (timer_pending(timer) && del_timer(timer))
+					sctp_association_put(asoc);
+			}
+		}
+	}
+	return retval;
+}
+
 /* Append a chunk to the offered packet reporting back any inability to do
  * so.
  */
@@ -167,6 +200,10 @@ sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
 	size_t pmtu;
 	int too_big;
 
+	retval = sctp_packet_bundle_sack(packet, chunk);
+	if (retval != SCTP_XMIT_OK)
+		goto finish;
+		
 	pmtu  = ((packet->transport->asoc) ?
 		 (packet->transport->asoc->pmtu) :
 		 (packet->transport->pmtu));
@@ -216,9 +253,10 @@ sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
 		retval = sctp_packet_append_data(packet, chunk);
 		if (SCTP_XMIT_OK != retval)
 			goto finish;
-	} else if (SCTP_CID_COOKIE_ECHO == chunk->chunk_hdr->type) {
+	} else if (SCTP_CID_COOKIE_ECHO == chunk->chunk_hdr->type)
 		packet->has_cookie_echo = 1;
-	}
+	else if (SCTP_CID_SACK == chunk->chunk_hdr->type) 
+		packet->has_sack = 1;
 
 	/* It is OK to send this chunk.  */
 	__skb_queue_tail(&packet->chunks, (struct sk_buff *)chunk);

net/sctp/outqueue.c

@@ -876,7 +876,7 @@ int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
 		start_timer = 0;
 		queue = &q->out;
 
-		while (NULL != (chunk = sctp_outq_dequeue_data(q))) {
+		while (chunk = sctp_outq_dequeue_data(q)) {
 			/* RFC 2960 6.5 Every DATA chunk MUST carry a valid
 			 * stream identifier.
 			 */
@@ -891,9 +891,7 @@ int sctp_outq_flush(struct sctp_outq *q, int rtx_timeout)
 				if (ev)
 					sctp_ulpq_tail_event(&asoc->ulpq, ev);
 
-				/* Free the chunk. This chunk is not on any
-				 * list yet, just free it.
-				 */
+				/* Free the chunk. */
 				sctp_free_chunk(chunk);
 				continue;
 			}