Commit faee47cd authored by Vlad Yasevich's avatar Vlad Yasevich Committed by David S. Miller
Browse files

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: default avatarVlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4458f04c

include/net/sctp/structs.h

+2 −0
Original line number Diff line number Diff line
@@ -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;

net/sctp/sm_sideeffect.c

+15 −2
Original line number Diff line number Diff line
@@ -461,10 +461,16 @@ static void sctp_do_8_2_transport_strike(struct sctp_association *asoc, 
	 * expires, set RTO <- RTO * 2 ("back off the timer").  The

	 * maximum value discussed in rule C7 above (RTO.max) may be

	 * used to provide an upper bound to this doubling operation.

	 *

	 * Special Case:  the first HB doesn't trigger exponential backoff.

	 * The first unacknowleged HB triggers it.  We do this with a flag

	 * that indicates that we have an outstanding HB.

	 */

	if (transport->hb_sent) {

		transport->last_rto = transport->rto;

		transport->rto = min((transport->rto * 2), transport->asoc->rto_max);

	}

}



/* Worker routine to handle INIT command failure.  */

static void sctp_cmd_init_failed(sctp_cmd_seq_t *commands,
@@ -621,6 +627,11 @@ static void sctp_cmd_transport_on(sctp_cmd_seq_t *cmds, 
	t->error_count = 0;

	t->asoc->overall_error_count = 0;



	/* Clear the hb_sent flag to signal that we had a good

	 * acknowledgement.

	 */

	t->hb_sent = 0;



	/* Mark the destination transport address as active if it is not so

	 * marked.

	 */
@@ -657,6 +668,8 @@ static void sctp_cmd_transport_reset(sctp_cmd_seq_t *cmds, 


	/* Mark one strike against a transport.  */

	sctp_do_8_2_transport_strike(asoc, t);



	t->hb_sent = 1;

}



/* Helper function to process the process SACK command.  */

net/sctp/transport.c

+2 −0
Original line number Diff line number Diff line
@@ -79,6 +79,7 @@ static struct sctp_transport *sctp_transport_init(struct sctp_transport *peer, 
	peer->rttvar = 0;

	peer->srtt = 0;

	peer->rto_pending = 0;

	peer->hb_sent = 0;

	peer->fast_recovery = 0;



	peer->last_time_heard = jiffies;
@@ -608,6 +609,7 @@ void sctp_transport_reset(struct sctp_transport *t) 
	t->flight_size = 0;

	t->error_count = 0;

	t->rto_pending = 0;

	t->hb_sent = 0;

	t->fast_recovery = 0;



	/* Initialize the state information for SFR-CACC */

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