Commit 4ccbd0b0 authored by Marcelo Ricardo Leitner's avatar Marcelo Ricardo Leitner Committed by David S. Miller
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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: default avatarMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e56f777a

net/sctp/transport.c

+18 −8
Original line number Diff line number Diff line
@@ -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;

		}