sctp: Correctly implement Fast Recovery cwnd manipulations.
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>
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@ -902,7 +902,10 @@ struct sctp_transport {
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* calculation completes (i.e. the DATA chunk
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* is SACK'd) clear this flag.
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*/
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int rto_pending;
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__u8 rto_pending;
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/* Flag to track the current fast recovery state */
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__u8 fast_recovery;
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/*
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* These are the congestion stats.
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@ -921,6 +924,9 @@ struct sctp_transport {
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/* Data that has been sent, but not acknowledged. */
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__u32 flight_size;
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/* TSN marking the fast recovery exit point */
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__u32 fast_recovery_exit;
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/* Destination */
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struct dst_entry *dst;
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/* Source address. */
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@ -79,6 +79,7 @@ static struct sctp_transport *sctp_transport_init(struct sctp_transport *peer,
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peer->rttvar = 0;
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peer->srtt = 0;
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peer->rto_pending = 0;
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peer->fast_recovery = 0;
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peer->last_time_heard = jiffies;
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peer->last_time_used = jiffies;
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@ -403,11 +404,16 @@ void sctp_transport_raise_cwnd(struct sctp_transport *transport,
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cwnd = transport->cwnd;
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flight_size = transport->flight_size;
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/* See if we need to exit Fast Recovery first */
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if (transport->fast_recovery &&
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TSN_lte(transport->fast_recovery_exit, sack_ctsn))
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transport->fast_recovery = 0;
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/* The appropriate cwnd increase algorithm is performed if, and only
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* if the cumulative TSN has advanced and the congestion window is
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* if the cumulative TSN whould advanced and the congestion window is
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* being fully utilized.
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*/
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if ((transport->asoc->ctsn_ack_point >= sack_ctsn) ||
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if (TSN_lte(sack_ctsn, transport->asoc->ctsn_ack_point) ||
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(flight_size < cwnd))
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return;
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@ -416,17 +422,23 @@ void sctp_transport_raise_cwnd(struct sctp_transport *transport,
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pmtu = transport->asoc->pathmtu;
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if (cwnd <= ssthresh) {
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/* RFC 2960 7.2.1, sctpimpguide-05 2.14.2 When cwnd is less
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* than or equal to ssthresh an SCTP endpoint MUST use the
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* slow start algorithm to increase cwnd only if the current
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* congestion window is being fully utilized and an incoming
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* SACK advances the Cumulative TSN Ack Point. Only when these
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* two conditions are met can the cwnd be increased otherwise
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* the cwnd MUST not be increased. If these conditions are met
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* then cwnd MUST be increased by at most the lesser of
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* 1) the total size of the previously outstanding DATA
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* chunk(s) acknowledged, and 2) the destination's path MTU.
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/* RFC 4960 7.2.1
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* o When cwnd is less than or equal to ssthresh, an SCTP
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* endpoint MUST use the slow-start algorithm to increase
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* cwnd only if the current congestion window is being fully
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* utilized, an incoming SACK advances the Cumulative TSN
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* Ack Point, and the data sender is not in Fast Recovery.
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* Only when these three conditions are met can the cwnd be
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* increased; otherwise, the cwnd MUST not be increased.
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* If these conditions are met, then cwnd MUST be increased
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* by, at most, the lesser of 1) the total size of the
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* previously outstanding DATA chunk(s) acknowledged, and
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* 2) the destination's path MTU. This upper bound protects
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* against the ACK-Splitting attack outlined in [SAVAGE99].
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*/
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if (transport->fast_recovery)
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return;
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if (bytes_acked > pmtu)
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cwnd += pmtu;
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else
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@ -502,6 +514,13 @@ void sctp_transport_lower_cwnd(struct sctp_transport *transport,
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* cwnd = ssthresh
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* partial_bytes_acked = 0
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*/
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if (transport->fast_recovery)
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return;
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/* Mark Fast recovery */
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transport->fast_recovery = 1;
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transport->fast_recovery_exit = transport->asoc->next_tsn - 1;
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transport->ssthresh = max(transport->cwnd/2,
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4*transport->asoc->pathmtu);
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transport->cwnd = transport->ssthresh;
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@ -586,6 +605,7 @@ void sctp_transport_reset(struct sctp_transport *t)
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t->flight_size = 0;
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t->error_count = 0;
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t->rto_pending = 0;
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t->fast_recovery = 0;
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/* Initialize the state information for SFR-CACC */
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t->cacc.changeover_active = 0;
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