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>
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index 9d358945..e3ebf04 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -405,13 +405,6 @@
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 @@
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 @@
* 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 @@
* 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;
}