1 files changed, 96 insertions, 115 deletions

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index 5ae609200674..ee13d28d39d1 100644
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -1239,78 +1239,107 @@ void sctp_assoc_update(struct sctp_association *asoc,
 }
 
 /* Update the retran path for sending a retransmitted packet.
- * Round-robin through the active transports, else round-robin
- * through the inactive transports as this is the next best thing
- * we can try.
+ * See also RFC4960, 6.4. Multi-Homed SCTP Endpoints:
+ *
+ *   When there is outbound data to send and the primary path
+ *   becomes inactive (e.g., due to failures), or where the
+ *   SCTP user explicitly requests to send data to an
+ *   inactive destination transport address, before reporting
+ *   an error to its ULP, the SCTP endpoint should try to send
+ *   the data to an alternate active destination transport
+ *   address if one exists.
+ *
+ *   When retransmitting data that timed out, if the endpoint
+ *   is multihomed, it should consider each source-destination
+ *   address pair in its retransmission selection policy.
+ *   When retransmitting timed-out data, the endpoint should
+ *   attempt to pick the most divergent source-destination
+ *   pair from the original source-destination pair to which
+ *   the packet was transmitted.
+ *
+ *   Note: Rules for picking the most divergent source-destination
+ *   pair are an implementation decision and are not specified
+ *   within this document.
+ *
+ * Our basic strategy is to round-robin transports in priorities
+ * according to sctp_state_prio_map[] e.g., if no such
+ * transport with state SCTP_ACTIVE exists, round-robin through
+ * SCTP_UNKNOWN, etc. You get the picture.
  */
-void sctp_assoc_update_retran_path(struct sctp_association *asoc)
+static const u8 sctp_trans_state_to_prio_map[] = {
+        [SCTP_ACTIVE]   = 3,    /* best case */
+        [SCTP_UNKNOWN]  = 2,
+        [SCTP_PF]       = 1,
+        [SCTP_INACTIVE] = 0,    /* worst case */
+};
+
+static u8 sctp_trans_score(const struct sctp_transport *trans)
 {
-        struct sctp_transport *t, *next;
-        struct list_head *head = &asoc->peer.transport_addr_list;
-        struct list_head *pos;
+        return sctp_trans_state_to_prio_map[trans->state];
+}
 
-        if (asoc->peer.transport_count == 1)
-                return;
+static struct sctp_transport *sctp_trans_elect_best(struct sctp_transport *curr,
+                                                    struct sctp_transport *best)
+{
+        if (best == NULL)
+                return curr;
 
-        /* Find the next transport in a round-robin fashion. */
-        t = asoc->peer.retran_path;
-        pos = &t->transports;
-        next = NULL;
+        return sctp_trans_score(curr) > sctp_trans_score(best) ? curr : best;
+}
 
-        while (1) {
-                /* Skip the head. */
-                if (pos->next == head)
-                        pos = head->next;
-                else
-                        pos = pos->next;
+void sctp_assoc_update_retran_path(struct sctp_association *asoc)
+{
+        struct sctp_transport *trans = asoc->peer.retran_path;
+        struct sctp_transport *trans_next = NULL;
 
-                t = list_entry(pos, struct sctp_transport, transports);
+        /* We're done as we only have the one and only path. */
+        if (asoc->peer.transport_count == 1)
+                return;
+        /* If active_path and retran_path are the same and active,
+         * then this is the only active path. Use it.
+         */
+        if (asoc->peer.active_path == asoc->peer.retran_path &&
+            asoc->peer.active_path->state == SCTP_ACTIVE)
+                return;
 
-                /* We have exhausted the list, but didn't find any
-                 * other active transports.  If so, use the next
-                 * transport.
-                 */
-                if (t == asoc->peer.retran_path) {
-                        t = next;
+        /* Iterate from retran_path's successor back to retran_path. */
+        for (trans = list_next_entry(trans, transports); 1;
+             trans = list_next_entry(trans, transports)) {
+                /* Manually skip the head element. */
+                if (&trans->transports == &asoc->peer.transport_addr_list)
+                        continue;
+                if (trans->state == SCTP_UNCONFIRMED)
+                        continue;
+                trans_next = sctp_trans_elect_best(trans, trans_next);
+                /* Active is good enough for immediate return. */
+                if (trans_next->state == SCTP_ACTIVE)
                         break;
-                }
-
-                /* Try to find an active transport. */
-
-                if ((t->state == SCTP_ACTIVE) ||
-                    (t->state == SCTP_UNKNOWN)) {
+                /* We've reached the end, time to update path. */
+                if (trans == asoc->peer.retran_path)
                         break;
-                } else {
-                        /* Keep track of the next transport in case
-                         * we don't find any active transport.
-                         */
-                        if (t->state != SCTP_UNCONFIRMED && !next)
-                                next = t;
-                }
         }
 
-        if (t)
-                asoc->peer.retran_path = t;
-        else
-                t = asoc->peer.retran_path;
+        if (trans_next != NULL)
+                asoc->peer.retran_path = trans_next;
 
-        pr_debug("%s: association:%p addr:%pISpc\n", __func__, asoc,
-                 &t->ipaddr.sa);
+        pr_debug("%s: association:%p updated new path to addr:%pISpc\n",
+                 __func__, asoc, &asoc->peer.retran_path->ipaddr.sa);
 }
 
-/* Choose the transport for sending retransmit packet.  */
-struct sctp_transport *sctp_assoc_choose_alter_transport(
-        struct sctp_association *asoc, struct sctp_transport *last_sent_to)
+struct sctp_transport *
+sctp_assoc_choose_alter_transport(struct sctp_association *asoc,
+                                  struct sctp_transport *last_sent_to)
 {
         /* If this is the first time packet is sent, use the active path,
          * else use the retran path. If the last packet was sent over the
          * retran path, update the retran path and use it.
          */
-        if (!last_sent_to)
+        if (last_sent_to == NULL) {
                 return asoc->peer.active_path;
-        else {
+        } else {
                 if (last_sent_to == asoc->peer.retran_path)
                         sctp_assoc_update_retran_path(asoc);
+
                 return asoc->peer.retran_path;
         }
 }
@@ -1367,44 +1396,35 @@ static inline bool sctp_peer_needs_update(struct sctp_association *asoc)
         return false;
 }
 
-/* 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)
+/* 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)
 {
+        int rx_count;
         struct sctp_chunk *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;
-        }
+        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 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;
-        }
+        if ((asoc->base.sk->sk_rcvbuf - rx_count) > 0)
+                asoc->rwnd = (asoc->base.sk->sk_rcvbuf - rx_count) >> 1;
+        else
+                asoc->rwnd = 0;
 
-        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);
+        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);
 
         /* 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 (sctp_peer_needs_update(asoc)) {
+        if (update_peer && sctp_peer_needs_update(asoc)) {
                 asoc->a_rwnd = asoc->rwnd;
 
                 pr_debug("%s: sending window update SACK- asoc:%p rwnd:%u "
@@ -1426,45 +1446,6 @@ void sctp_assoc_rwnd_increase(struct sctp_association *asoc, unsigned int len)
         }
 }
 
-/* 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.