sctp: Optimize SFR-CACC transport list walking during SACK processing

There is a possibility of walking the transport list twice during
SACK processing when doing SFR-CACC algorithm.  We can restructure
the code to only do this once.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

1 files changed, 19 insertions, 15 deletions

diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index ef5ea7423cc8..c8de4da57f36 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -1145,27 +1145,31 @@ int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
          * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
          * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
          * all destinations.
-         */
-        if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
-                primary->cacc.changeover_active = 0;
-                list_for_each_entry(transport, transport_list,
-                                transports) {
-                        transport->cacc.cycling_changeover = 0;
-                }
-        }
-
-        /*
-         * SFR-CACC algorithm:
          * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
          * is set the receiver of the SACK MUST take the following actions:
          *
          * A) Initialize the cacc_saw_newack to 0 for all destination
          * addresses.
+         *
+         * Only bother if changeover_active is set. Otherwise, this is
+         * totally suboptimal to do on every SACK.
          */
-        if (gap_ack_blocks &&
-            primary->cacc.changeover_active) {
-                list_for_each_entry(transport, transport_list, transports) {
-                        transport->cacc.cacc_saw_newack = 0;
+        if (primary->cacc.changeover_active) {
+                u8 clear_cycling = 0;
+
+                if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
+                        primary->cacc.changeover_active = 0;
+                        clear_cycling = 1;
+                }
+
+                if (clear_cycling || gap_ack_blocks) {
+                        list_for_each_entry(transport, transport_list,
+                                        transports) {
+                                if (clear_cycling)
+                                        transport->cacc.cycling_changeover = 0;
+                                if (gap_ack_blocks)
+                                        transport->cacc.cacc_saw_newack = 0;
+                        }
                 }
         }