From 4ccbd0b0b9b8b09d87c7e7b0f868eda2bed03189 Mon Sep 17 00:00:00 2001 From: Marcelo Ricardo Leitner Date: Fri, 23 Jun 2017 19:59:35 -0300 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- net/sctp/transport.c | 26 ++++++++++++++++++-------- 1 file changed, 18 insertions(+), 8 deletions(-) diff --git a/net/sctp/transport.c b/net/sctp/transport.c index 9d3589451a96..e3ebf04ddbd0 100644 --- a/net/sctp/transport.c +++ b/net/sctp/transport.c @@ -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; } -- 2.30.2