svn commit: r364754 - in head/sys/netinet: . tcp_stacks

[Michael Tuexen]

Author: tuexen
Date: Tue Aug 25 09:42:03 2020
New Revision: 364754
URL: https://svnweb.freebsd.org/changeset/base/364754

Log:
  RFC 3465 defines a limit L used in TCP slow start for limiting the number
  of acked bytes as described in Section 2.2 of that document.
  This patch ensures that this limit is not also applied in congestion
  avoidance. Applying this limit also in congestion avoidance can result in
  using less bandwidth than allowed.
  
  Reported by:		l.tian.email at gmail.com
  Reviewed by:		rrs, rscheff
  MFC after:		3 days
  Sponsored by:		Netflix, Inc.
  Differential Revision:	https://reviews.freebsd.org/D26120

Modified:
  head/sys/netinet/tcp_input.c
  head/sys/netinet/tcp_stacks/rack.c

Modified: head/sys/netinet/tcp_input.c
==============================================================================
--- head/sys/netinet/tcp_input.c	Tue Aug 25 06:49:10 2020	(r364753)
+++ head/sys/netinet/tcp_input.c	Tue Aug 25 09:42:03 2020	(r364754)
@@ -349,8 +349,7 @@ cc_ack_received(struct tcpcb *tp, struct tcphdr *th, u
 		}
 #endif /* STATS */
 		if (tp->snd_cwnd > tp->snd_ssthresh) {
-			tp->t_bytes_acked += min(tp->ccv->bytes_this_ack,
-			     nsegs * V_tcp_abc_l_var * tcp_maxseg(tp));
+			tp->t_bytes_acked += tp->ccv->bytes_this_ack;
 			if (tp->t_bytes_acked >= tp->snd_cwnd) {
 				tp->t_bytes_acked -= tp->snd_cwnd;
 				tp->ccv->flags |= CCF_ABC_SENTAWND;

Modified: head/sys/netinet/tcp_stacks/rack.c
==============================================================================
--- head/sys/netinet/tcp_stacks/rack.c	Tue Aug 25 06:49:10 2020	(r364753)
+++ head/sys/netinet/tcp_stacks/rack.c	Tue Aug 25 09:42:03 2020	(r364754)
@@ -3911,8 +3911,7 @@ rack_ack_received(struct tcpcb *tp, struct tcp_rack *r
 #endif
 	}
 	if (rack->r_ctl.cwnd_to_use > tp->snd_ssthresh) {
-		tp->t_bytes_acked += min(tp->ccv->bytes_this_ack,
-			 nsegs * V_tcp_abc_l_var * ctf_fixed_maxseg(tp));
+		tp->t_bytes_acked += tp->ccv->bytes_this_ack;
 		if (tp->t_bytes_acked >= rack->r_ctl.cwnd_to_use) {
 			tp->t_bytes_acked -= rack->r_ctl.cwnd_to_use;
 			tp->ccv->flags |= CCF_ABC_SENTAWND;