[SCTP] Fix to update rwnd on partial reads.

include/net/sctp/structs.h

@@ -1633,6 +1633,8 @@ __u32 __sctp_association_get_tsn_block(sctp_association_t *, int);
 __u16 __sctp_association_get_next_ssn(sctp_association_t *, __u16 sid);
 
 void sctp_assoc_sync_pmtu(sctp_association_t *);
+void sctp_assoc_rwnd_increase(sctp_association_t *, int);
+void sctp_assoc_rwnd_decrease(sctp_association_t *, int);
 
 int sctp_cmp_addr_exact(const union sctp_addr *ss1,
 		        const union sctp_addr *ss2);

net/sctp/associola.c

@@ -977,3 +977,70 @@ void sctp_assoc_sync_pmtu(sctp_association_t *asoc)
 	SCTP_DEBUG_PRINTK("%s: asoc:%p, pmtu:%d, frag_point:%d\n",
 			  __FUNCTION__, asoc, asoc->pmtu, asoc->frag_point);
 }
+
+/* Increase asoc's rwnd by len and send any window update SACK if needed. */
+void sctp_assoc_rwnd_increase(sctp_association_t *asoc, int len)
+{
+	sctp_chunk_t *sack;
+	struct timer_list *timer;
+
+	if (asoc->rwnd_over) {
+		if (asoc->rwnd_over >= len) {
+			asoc->rwnd_over -= len;
+		} else {
+			asoc->rwnd += (len - asoc->rwnd_over);
+			asoc->rwnd_over = 0;
+		}
+	} else {
+		asoc->rwnd += len;
+	}
+
+	SCTP_DEBUG_PRINTK("%s: asoc %p rwnd increased by %d to (%u, %u) - %u\n",
+			  __FUNCTION__, asoc, len, asoc->rwnd, asoc->rwnd_over,
+			  asoc->a_rwnd);
+
+	/* Send a window update SACK if the rwnd has increased by at least the
+	 * minimum of the association's PMTU and half of the receive buffer.
+	 * The algorithm used is similar to the one described in 
+	 * Section 4.2.3.3 of RFC 1122.
+	 */
+	if ((asoc->state == SCTP_STATE_ESTABLISHED) &&
+	    (asoc->rwnd > asoc->a_rwnd) &&
+	    ((asoc->rwnd - asoc->a_rwnd) >=
+		     min_t(__u32, (asoc->base.sk->rcvbuf >> 1), asoc->pmtu))) {
+		SCTP_DEBUG_PRINTK("%s: Sending window update SACK- asoc: %p "
+				  "rwnd: %u a_rwnd: %u\n",
+				  __FUNCTION__, asoc, asoc->rwnd, asoc->a_rwnd);
+		sack = sctp_make_sack(asoc); 
+		if (!sack)
+			return;	
+
+		/* Update the last advertised rwnd value. */
+		asoc->a_rwnd = asoc->rwnd;
+
+		asoc->peer.sack_needed = 0;
+		asoc->peer.next_dup_tsn = 0;
+
+		sctp_outq_tail(&asoc->outqueue, sack);
+
+		/* Stop the SACK timer.  */
+		timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
+		if (timer_pending(timer) && del_timer(timer))
+			sctp_association_put(asoc);
+	} 
+}
+
+/* Decrease asoc's rwnd by len. */
+void sctp_assoc_rwnd_decrease(sctp_association_t *asoc, int len)
+{
+	SCTP_ASSERT(asoc->rwnd, "rwnd zero", return);
+	SCTP_ASSERT(!asoc->rwnd_over, "rwnd_over not zero", return);
+	if (asoc->rwnd >= len) {
+		asoc->rwnd -= len;
+	} else {
+		asoc->rwnd_over = len - asoc->rwnd;
+		asoc->rwnd = 0;
+	}
+	SCTP_DEBUG_PRINTK("%s: asoc %p rwnd decreased by %d to (%u, %u)\n",
+			  __FUNCTION__, asoc, len, asoc->rwnd, asoc->rwnd_over);
+}

net/sctp/socket.c

@@ -1191,6 +1191,12 @@ SCTP_STATIC int sctp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr
 			goto out_free;
 		sctp_skb_pull(skb, copied);
 		skb_queue_head(&sk->receive_queue, skb);
+		/* When only partial message is copied to the user, increase
+		 * rwnd by that amount. If all the data in the skb is read,
+		 * rwnd is updated when the skb's destructor is called via
+		 * sctp_ulpevent_free().
+		 */
+		sctp_assoc_rwnd_increase(event->asoc, copied);
 		goto out;
 	} else {
 		 msg->msg_flags |= MSG_EOR;

net/sctp/ulpevent.c

@@ -772,9 +772,6 @@ static void sctp_rcvmsg_rfree(struct sk_buff *skb)
 {
 	sctp_association_t *asoc;
 	sctp_ulpevent_t *event;
-	sctp_chunk_t *sack;
-	struct timer_list *timer;
-	int skb_len = skb_headlen(skb);
 
 	/* Current stack structures assume that the rcv buffer is
 	 * per socket.   For UDP style sockets this is not true as
@@ -784,50 +781,7 @@ static void sctp_rcvmsg_rfree(struct sk_buff *skb)
 	 */
 	event = (sctp_ulpevent_t *) skb->cb;
 	asoc = event->asoc;
-	if (asoc->rwnd_over) {
-		if (asoc->rwnd_over >= skb_len) {
-			asoc->rwnd_over -= skb_len;
-		} else {
-			asoc->rwnd += (skb_len - asoc->rwnd_over);
-			asoc->rwnd_over = 0;
-		}
-	} else {
-		asoc->rwnd += skb_len;
-	}
-
-	SCTP_DEBUG_PRINTK("rwnd increased by %d to (%u, %u) - %u\n",
-			  skb_len, asoc->rwnd, asoc->rwnd_over, asoc->a_rwnd);
-
-	/* Send a window update SACK if the rwnd has increased by at least the
-	 * minimum of the association's PMTU and half of the receive buffer.
-	 * The algorithm used is similar to the one described in 
-	 * Section 4.2.3.3 of RFC 1122.
-	 */
-	if ((asoc->state == SCTP_STATE_ESTABLISHED) &&
-	    (asoc->rwnd > asoc->a_rwnd) &&
-	    ((asoc->rwnd - asoc->a_rwnd) >=
-		     min_t(__u32, (asoc->base.sk->rcvbuf >> 1), asoc->pmtu))) {
-		SCTP_DEBUG_PRINTK("Sending window update SACK- rwnd: %u "
-				  "a_rwnd: %u\n", asoc->rwnd, asoc->a_rwnd);
-		sack = sctp_make_sack(asoc); 
-		if (!sack)
-			goto out;
-
-		/* Update the last advertised rwnd value. */
-		asoc->a_rwnd = asoc->rwnd;
-
-		asoc->peer.sack_needed = 0;
-		asoc->peer.next_dup_tsn = 0;
-
-		sctp_outq_tail(&asoc->outqueue, sack);
-
-		/* Stop the SACK timer.  */
-		timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
-		if (timer_pending(timer) && del_timer(timer))
-			sctp_association_put(asoc);
-	} 
-
-out:
+	sctp_assoc_rwnd_increase(asoc, skb_headlen(skb));
 	sctp_association_put(asoc);
 }
 
@@ -835,7 +789,6 @@ static void sctp_rcvmsg_rfree(struct sk_buff *skb)
 static void sctp_ulpevent_set_owner_r(struct sk_buff *skb, sctp_association_t *asoc)
 {
 	sctp_ulpevent_t *event;
-	int skb_len = skb_headlen(skb);
 
 	/* The current stack structures assume that the rcv buffer is
 	 * per socket.  For UDP-style sockets this is not true as
@@ -850,16 +803,7 @@ static void sctp_ulpevent_set_owner_r(struct sk_buff *skb, sctp_association_t *a
 
 	skb->destructor = sctp_rcvmsg_rfree;
 
-	SCTP_ASSERT(asoc->rwnd, "rwnd zero", return);
-	SCTP_ASSERT(!asoc->rwnd_over, "rwnd_over not zero", return);
-	if (asoc->rwnd >= skb_len) {
-		asoc->rwnd -= skb_len;
-	} else {
-		asoc->rwnd_over = skb_len - asoc->rwnd;
-		asoc->rwnd = 0;
-	}
-	SCTP_DEBUG_PRINTK("rwnd decreased by %d to (%u, %u)\n",
-			  skb_len, asoc->rwnd, asoc->rwnd_over);
+	sctp_assoc_rwnd_decrease(asoc, skb_headlen(skb));
 }
 
 /* A simple destructor to give up the reference to the association. */