1 files changed, 65 insertions, 17 deletions

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index 4f6d6f9d1274..39579c3e0d14 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -1395,35 +1395,44 @@ static inline bool sctp_peer_needs_update(struct sctp_association *asoc)
         return false;
 }
 
-/* Update asoc's rwnd for the approximated state in the buffer,
- * and check whether SACK needs to be sent.
- */
-void sctp_assoc_rwnd_update(struct sctp_association *asoc, bool update_peer)
+/* Increase asoc's rwnd by len and send any window update SACK if needed. */
+void sctp_assoc_rwnd_increase(struct sctp_association *asoc, unsigned int len)
 {
-        int rx_count;
         struct sctp_chunk *sack;
         struct timer_list *timer;
 
-        if (asoc->ep->rcvbuf_policy)
-                rx_count = atomic_read(&asoc->rmem_alloc);
-        else
-                rx_count = atomic_read(&asoc->base.sk->sk_rmem_alloc);
+        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;
+        }
 
-        if ((asoc->base.sk->sk_rcvbuf - rx_count) > 0)
-                asoc->rwnd = (asoc->base.sk->sk_rcvbuf - rx_count) >> 1;
-        else
-                asoc->rwnd = 0;
+        /* If we had window pressure, start recovering it
+         * once our rwnd had reached the accumulated pressure
+         * threshold.  The idea is to recover slowly, but up
+         * to the initial advertised window.
+         */
+        if (asoc->rwnd_press && asoc->rwnd >= asoc->rwnd_press) {
+                int change = min(asoc->pathmtu, asoc->rwnd_press);
+                asoc->rwnd += change;
+                asoc->rwnd_press -= change;
+        }
 
-        pr_debug("%s: asoc:%p rwnd=%u, rx_count=%d, sk_rcvbuf=%d\n",
-                 __func__, asoc, asoc->rwnd, rx_count,
-                 asoc->base.sk->sk_rcvbuf);
+        pr_debug("%s: asoc:%p rwnd increased by %d to (%u, %u) - %u\n",
+                 __func__, 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 (update_peer && sctp_peer_needs_update(asoc)) {
+        if (sctp_peer_needs_update(asoc)) {
                 asoc->a_rwnd = asoc->rwnd;
 
                 pr_debug("%s: sending window update SACK- asoc:%p rwnd:%u "
@@ -1445,6 +1454,45 @@ void sctp_assoc_rwnd_update(struct sctp_association *asoc, bool update_peer)
         }
 }
 
+/* Decrease asoc's rwnd by len. */
+void sctp_assoc_rwnd_decrease(struct sctp_association *asoc, unsigned int len)
+{
+        int rx_count;
+        int over = 0;
+
+        if (unlikely(!asoc->rwnd || asoc->rwnd_over))
+                pr_debug("%s: association:%p has asoc->rwnd:%u, "
+                         "asoc->rwnd_over:%u!\n", __func__, asoc,
+                         asoc->rwnd, asoc->rwnd_over);
+
+        if (asoc->ep->rcvbuf_policy)
+                rx_count = atomic_read(&asoc->rmem_alloc);
+        else
+                rx_count = atomic_read(&asoc->base.sk->sk_rmem_alloc);
+
+        /* If we've reached or overflowed our receive buffer, announce
+         * a 0 rwnd if rwnd would still be positive.  Store the
+         * the potential pressure overflow so that the window can be restored
+         * back to original value.
+         */
+        if (rx_count >= asoc->base.sk->sk_rcvbuf)
+                over = 1;
+
+        if (asoc->rwnd >= len) {
+                asoc->rwnd -= len;
+                if (over) {
+                        asoc->rwnd_press += asoc->rwnd;
+                        asoc->rwnd = 0;
+                }
+        } else {
+                asoc->rwnd_over = len - asoc->rwnd;
+                asoc->rwnd = 0;
+        }
+
+        pr_debug("%s: asoc:%p rwnd decreased by %d to (%u, %u, %u)\n",
+                 __func__, asoc, len, asoc->rwnd, asoc->rwnd_over,
+                 asoc->rwnd_press);
+}
 
 /* Build the bind address list for the association based on info from the
  * local endpoint and the remote peer.