[SCTP]: Rewrite of sctp buffer management code

This patch introduces autotuning to the sctp buffer management code
similar to the TCP.  The buffer space can be grown if the advertised
receive window still has room.  This might happen if small message
sizes are used, which is common in telecom environmens.
New tunables are introduced that provide limits to buffer growth
and memory pressure is entered if to much buffer spaces is used.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 56 deletions

diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index a583d67cab6..ec0328b1cdb 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -5428,10 +5428,8 @@ static int sctp_eat_data(const struct sctp_association *asoc,
 	sctp_verb_t deliver;
 	int tmp;
 	__u32 tsn;
-	int account_value;
 	struct sctp_tsnmap *map = (struct sctp_tsnmap *)&asoc->peer.tsn_map;
 	struct sock *sk = asoc->base.sk;
-	int rcvbuf_over = 0;
 
 	data_hdr = chunk->subh.data_hdr = (sctp_datahdr_t *)chunk->skb->data;
 	skb_pull(chunk->skb, sizeof(sctp_datahdr_t));
@@ -5441,48 +5439,6 @@ static int sctp_eat_data(const struct sctp_association *asoc,
 
 	/* ASSERT:  Now skb->data is really the user data.  */
 
-	/*
-	 * If we are established, and we have used up our receive buffer
-	 * memory, think about droping the frame.
-	 * Note that we have an opportunity to improve performance here.
-	 * If we accept one chunk from an skbuff, we have to keep all the
-	 * memory of that skbuff around until the chunk is read into user
-	 * space. Therefore, once we accept 1 chunk we may as well accept all
-	 * remaining chunks in the skbuff. The data_accepted flag helps us do
-	 * that.
-	 */
-	if ((asoc->state == SCTP_STATE_ESTABLISHED) && (!chunk->data_accepted)) {
-		/*
-		 * If the receive buffer policy is 1, then each
-		 * association can allocate up to sk_rcvbuf bytes
-		 * otherwise, all the associations in aggregate
-		 * may allocate up to sk_rcvbuf bytes
-		 */
-		if (asoc->ep->rcvbuf_policy)
-			account_value = atomic_read(&asoc->rmem_alloc);
-		else
-			account_value = atomic_read(&sk->sk_rmem_alloc);
-		if (account_value > sk->sk_rcvbuf) {
-			/*
-			 * We need to make forward progress, even when we are
-			 * under memory pressure, so we always allow the
-			 * next tsn after the ctsn ack point to be accepted.
-			 * This lets us avoid deadlocks in which we have to
-			 * drop frames that would otherwise let us drain the
-			 * receive queue.
-			 */
-			if ((sctp_tsnmap_get_ctsn(map) + 1) != tsn)
-				return SCTP_IERROR_IGNORE_TSN;
-
-			/*
-			 * We're going to accept the frame but we should renege
-			 * to make space for it. This will send us down that
-			 * path later in this function.
-			 */
-			rcvbuf_over = 1;
-		}
-	}
-
 	/* Process ECN based congestion.
 	 *
 	 * Since the chunk structure is reused for all chunks within
@@ -5542,18 +5498,9 @@ static int sctp_eat_data(const struct sctp_association *asoc,
 	 * seems a bit troublesome in that frag_point varies based on
 	 * PMTU.  In cases, such as loopback, this might be a rather
 	 * large spill over.
-	 * NOTE: If we have a full receive buffer here, we only renege if
-	 * our receiver can still make progress without the tsn being
-	 * received. We do this because in the event that the associations
-	 * receive queue is empty we are filling a leading gap, and since
-	 * reneging moves the gap to the end of the tsn stream, we are likely
-	 * to stall again very shortly. Avoiding the renege when we fill a
-	 * leading gap is a good heuristic for avoiding such steady state
-	 * stalls.
-	 */
-	if (!asoc->rwnd || asoc->rwnd_over ||
-	    (datalen > asoc->rwnd + asoc->frag_point) ||
-	    (rcvbuf_over && (!skb_queue_len(&sk->sk_receive_queue)))) {
+	 */
+	if ((!chunk->data_accepted) && (!asoc->rwnd || asoc->rwnd_over ||
+	    (datalen > asoc->rwnd + asoc->frag_point))) {
 
 		/* If this is the next TSN, consider reneging to make
 		 * room.   Note: Playing nice with a confused sender.  A
@@ -5574,6 +5521,21 @@ static int sctp_eat_data(const struct sctp_association *asoc,
 	}
 
 	/*
+	 * Also try to renege to limit our memory usage in the event that
+	 * we are under memory pressure
+	 * If we can't renege, don't worry about it, the sk_stream_rmem_schedule
+	 * in sctp_ulpevent_make_rcvmsg will drop the frame if we grow our
+	 * memory usage too much
+	 */
+	if (*sk->sk_prot_creator->memory_pressure) {
+		if (sctp_tsnmap_has_gap(map) &&
+	           (sctp_tsnmap_get_ctsn(map) + 1) == tsn) {
+			SCTP_DEBUG_PRINTK("Under Pressure! Reneging for tsn:%u\n", tsn);
+			deliver = SCTP_CMD_RENEGE;
+		 }
+	}
+
+	/*
 	 * Section 3.3.10.9 No User Data (9)
 	 *
 	 * Cause of error