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sctp: adjust cwnd increase in Congestion Avoidance phase 

RFC4960 Errata 3.26 identified that at the same time RFC4960 states that
cwnd should never grow more than 1*MTU per RTT, Section 7.2.2 was
underspecified and as described could allow increasing cwnd more than
that.

This patch updates it so partial_bytes_acked is maxed to cwnd if
flight_size doesn't reach cwnd, protecting it from such case.

See-also: https://tools.ietf.org/html/draft-ietf-tsvwg-rfc4960-errata-01#section-3.26
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Marcelo Ricardo Leitner 2017-06-23 19:59:35 -03:00 committed by David S. Miller
parent e56f777af8
commit 4ccbd0b0b9
1 changed files with 18 additions and 8 deletions
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26
net/sctp/transport.c
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@ -405,13 +405,6 @@ void sctp_transport_raise_cwnd(struct sctp_transport *transport,
TSN_lte(asoc->fast_recovery_exit, sack_ctsn))
asoc->fast_recovery = 0;
/* The appropriate cwnd increase algorithm is performed if, and only
* if the congestion window is being fully utilized.
* Note that RFC4960 Errata 3.22 removed the other condition.
*/
if (flight_size < cwnd)
return;
ssthresh = transport->ssthresh;
pba = transport->partial_bytes_acked;
pmtu = transport->asoc->pathmtu;
@ -434,6 +427,14 @@ void sctp_transport_raise_cwnd(struct sctp_transport *transport,
if (asoc->fast_recovery)
return;
/* The appropriate cwnd increase algorithm is performed
* if, and only if the congestion window is being fully
* utilized. Note that RFC4960 Errata 3.22 removed the
* other condition on ctsn moving.
*/
if (flight_size < cwnd)
return;
if (bytes_acked > pmtu)
cwnd += pmtu;
else
@ -451,6 +452,13 @@ void sctp_transport_raise_cwnd(struct sctp_transport *transport,
* acknowledged by the new Cumulative TSN Ack and by Gap
* Ack Blocks. (updated by RFC4960 Errata 3.22)
*
* When partial_bytes_acked is greater than cwnd and
* before the arrival of the SACK the sender had less
* bytes of data outstanding than cwnd (i.e., before
* arrival of the SACK, flightsize was less than cwnd),
* reset partial_bytes_acked to cwnd. (RFC 4960 Errata
* 3.26)
*
* When partial_bytes_acked is equal to or greater than
* cwnd and before the arrival of the SACK the sender
* had cwnd or more bytes of data outstanding (i.e.,
@ -460,7 +468,9 @@ void sctp_transport_raise_cwnd(struct sctp_transport *transport,
* increased by MTU. (RFC 4960 Errata 3.12)
*/
pba += bytes_acked;
if (pba >= cwnd) {
if (pba > cwnd && flight_size < cwnd)
pba = cwnd;
if (pba >= cwnd && flight_size >= cwnd) {
pba = pba - cwnd;
cwnd += pmtu;
}