sctp: Fix the RTO-doubling on idle-link heartbeats

SCTP incorrectly doubles rto ever time a Hearbeat chunk
is generated.   However RFC 4960 states:

   On an idle destination address that is allowed to heartbeat, it is
   recommended that a HEARTBEAT chunk is sent once per RTO of that
   destination address plus the protocol parameter 'HB.interval', with
   jittering of +/- 50% of the RTO value, and exponential backoff of the
   RTO if the previous HEARTBEAT is unanswered.

Essentially, of if the heartbean is unacknowledged, do we double the RTO.

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

1 files changed, 2 insertions, 0 deletions

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 9f70d54fcefc..23f08fe1d50a 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -910,8 +910,10 @@ struct sctp_transport {
          *              should be set. Every time the RTT
          *              calculation completes (i.e. the DATA chunk
          *              is SACK'd) clear this flag.
+         * hb_sent : a flag that signals that we have a pending heartbeat.
          */
         __u8 rto_pending;
+        __u8 hb_sent;
 
         /* Flag to track the current fast recovery state */
         __u8 fast_recovery;