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sctp: Correctly implement Fast Recovery cwnd manipulations.

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Correctly keep track of Fast Recovery state and do not reduce
congestion window multiple times during sucht state.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Tested-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vlad Yasevich 2008-06-04 12:38:43 -07:00 committed by David S. Miller
parent 159c6bea37
commit a646523481
2 changed files with 39 additions and 13 deletions
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8
include/net/sctp/structs.h
View File

@ -902,7 +902,10 @@ struct sctp_transport {
* calculation completes (i.e. the DATA chunk
* is SACK'd) clear this flag.
*/
int rto_pending;
__u8 rto_pending;
/* Flag to track the current fast recovery state */
__u8 fast_recovery;
/*
* These are the congestion stats.
@ -921,6 +924,9 @@ struct sctp_transport {
/* Data that has been sent, but not acknowledged. */
__u32 flight_size;
/* TSN marking the fast recovery exit point */
__u32 fast_recovery_exit;
/* Destination */
struct dst_entry *dst;
/* Source address. */

44
net/sctp/transport.c
View File

@ -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->fast_recovery = 0;
peer->last_time_heard = jiffies;
peer->last_time_used = jiffies;
@ -403,11 +404,16 @@ void sctp_transport_raise_cwnd(struct sctp_transport *transport,
cwnd = transport->cwnd;
flight_size = transport->flight_size;
/* See if we need to exit Fast Recovery first */
if (transport->fast_recovery &&
TSN_lte(transport->fast_recovery_exit, sack_ctsn))
transport->fast_recovery = 0;
/* The appropriate cwnd increase algorithm is performed if, and only
* if the cumulative TSN has advanced and the congestion window is
* if the cumulative TSN whould advanced and the congestion window is
* being fully utilized.
*/
if ((transport->asoc->ctsn_ack_point >= sack_ctsn) ||
if (TSN_lte(sack_ctsn, transport->asoc->ctsn_ack_point) ||
(flight_size < cwnd))
return;
@ -416,17 +422,23 @@ void sctp_transport_raise_cwnd(struct sctp_transport *transport,
pmtu = transport->asoc->pathmtu;
if (cwnd <= ssthresh) {
/* RFC 2960 7.2.1, sctpimpguide-05 2.14.2 When cwnd is less
* than or equal to ssthresh an SCTP endpoint MUST use the
* slow start algorithm to increase cwnd only if the current
* congestion window is being fully utilized and an incoming
* SACK advances the Cumulative TSN Ack Point. Only when these
* two conditions are met can the cwnd be increased otherwise
* the cwnd MUST not be increased. If these conditions are met
* then cwnd MUST be increased by at most the lesser of
* 1) the total size of the previously outstanding DATA
* chunk(s) acknowledged, and 2) the destination's path MTU.
/* RFC 4960 7.2.1
* o When cwnd is less than or equal to ssthresh, an SCTP
* endpoint MUST use the slow-start algorithm to increase
* cwnd only if the current congestion window is being fully
* utilized, an incoming SACK advances the Cumulative TSN
* Ack Point, and the data sender is not in Fast Recovery.
* Only when these three conditions are met can the cwnd be
* increased; otherwise, the cwnd MUST not be increased.
* If these conditions are met, then cwnd MUST be increased
* by, at most, the lesser of 1) the total size of the
* previously outstanding DATA chunk(s) acknowledged, and
* 2) the destination's path MTU. This upper bound protects
* against the ACK-Splitting attack outlined in [SAVAGE99].
*/
if (transport->fast_recovery)
return;
if (bytes_acked > pmtu)
cwnd += pmtu;
else
@ -502,6 +514,13 @@ void sctp_transport_lower_cwnd(struct sctp_transport *transport,
* cwnd = ssthresh
* partial_bytes_acked = 0
*/
if (transport->fast_recovery)
return;
/* Mark Fast recovery */
transport->fast_recovery = 1;
transport->fast_recovery_exit = transport->asoc->next_tsn - 1;
transport->ssthresh = max(transport->cwnd/2,
4*transport->asoc->pathmtu);
transport->cwnd = transport->ssthresh;
@ -586,6 +605,7 @@ void sctp_transport_reset(struct sctp_transport *t)
t->flight_size = 0;
t->error_count = 0;
t->rto_pending = 0;
t->fast_recovery = 0;
/* Initialize the state information for SFR-CACC */
t->cacc.changeover_active = 0;