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authorMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>2017-06-24 01:59:33 +0300
committerDavid S. Miller <davem@davemloft.net>2017-06-25 21:43:53 +0300
commitd0b53f40977446fdf2460b14d4544d1375a3138d (patch)
tree410a4d86328858a353481cc860916648d3aa7a4a /net/sctp/transport.c
parentf3ecab38240b624b37e003b5089a93682b109699 (diff)
downloadlinux-d0b53f40977446fdf2460b14d4544d1375a3138d.tar.xz
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.c15
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, "