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| author | Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> | 2017-06-23 19:59:33 -0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-06-25 14:43:53 -0400 |
| commit | d0b53f40977446fdf2460b14d4544d1375a3138d (patch) | |
| tree | 410a4d86328858a353481cc860916648d3aa7a4a /net/sctp/transport.c | |
| parent | f3ecab38240b624b37e003b5089a93682b109699 (diff) | |
| download | lwn-d0b53f40977446fdf2460b14d4544d1375a3138d.tar.gz lwn-d0b53f40977446fdf2460b14d4544d1375a3138d.zip | |
sctp: update order of adjustments of partial_bytes_acked and cwnd
RFC4960 Errata 3.12 says RFC4960 is unclear about the order of
adjustments applied to partial_bytes_acked and cwnd in the congestion
avoidance phase, and that the actual order should be:
partial_bytes_acked is reset to (partial_bytes_acked - cwnd). Next, cwnd
is increased by MTU.
We were first increasing cwnd, and then subtracting the new value pba,
which leads to a different result as pba is smaller than what it should
and could cause cwnd to not grow as much.
See-also: https://tools.ietf.org/html/draft-ietf-tsvwg-rfc4960-errata-01#section-3.12
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sctp/transport.c')
| -rw-r--r-- | net/sctp/transport.c | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/net/sctp/transport.c b/net/sctp/transport.c index 721eeebfcd8a..04b6dd1a07de 100644 --- a/net/sctp/transport.c +++ b/net/sctp/transport.c @@ -452,17 +452,18 @@ void sctp_transport_raise_cwnd(struct sctp_transport *transport, * chunks acknowledged by the new Cumulative TSN Ack and by * Gap Ack Blocks. * - * 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., before arrival of the - * SACK, flightsize was greater than or equal to cwnd), - * increase cwnd by MTU, and reset partial_bytes_acked to - * (partial_bytes_acked - cwnd). + * 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., + * before arrival of the SACK, flightsize was greater + * than or equal to cwnd), partial_bytes_acked is reset + * to (partial_bytes_acked - cwnd). Next, cwnd is + * increased by MTU. (RFC 4960 Errata 3.12) */ pba += bytes_acked; if (pba >= cwnd) { + pba = pba - cwnd; cwnd += pmtu; - pba = ((cwnd < pba) ? (pba - cwnd) : 0); } pr_debug("%s: congestion avoidance: transport:%p, " |