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This is an initial step in implementing the new congestion window

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validation as specified in RFC 7661.

Submitted by:		Richard Scheffenegger
Reviewed by:		rrs@, tuexen@
Differential Revision:	https://reviews.freebsd.org/D21798
This commit is contained in:
Michael Tuexen 2019-12-01 20:35:41 +00:00
parent f09a6a3538
commit b72e56e758
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=355269
4 changed files with 19 additions and 2 deletions
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6
share/man/man4/tcp.4
View File

@ -538,6 +538,12 @@ The value should be relative to the link capacity.
Start with small values for lower-capacity links.
Large bursts can cause buffer overruns and packet drops if routers have small
buffers or the link is experiencing congestion.
.It Va newcwd
Enable the New Congestion Window Validation mechanism as described in RFC 7661.
This gently reduces the congestion window during periods, where TCP is
application limited and the network bandwidth is not utilized completely.
That prevents self-inflicted packet losses once the application starts to
transmit data at a higher speed.
.It Va rfc6675_pipe
Calculate the bytes in flight using the algorithm described in RFC 6675, and
is also a prerequisite to enable Proportional Rate Reduction.

9
sys/netinet/tcp_input.c
View File

@ -150,6 +150,11 @@ SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(drop_synfin), 0,
"Drop TCP packets with SYN+FIN set");
VNET_DEFINE(int, tcp_do_newcwv) = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, newcwv, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(tcp_do_newcwv), 0,
"Enable New Congestion Window Validation per RFC7661");
VNET_DEFINE(int, tcp_do_rfc6675_pipe) = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_pipe, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(tcp_do_rfc6675_pipe), 0,
@ -297,7 +302,9 @@ cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t nsegs,
tp->ccv->nsegs = nsegs;
tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th);
if (tp->snd_cwnd <= tp->snd_wnd)
if ((!V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd)) ||
(V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd) &&
(tp->snd_cwnd < (tcp_compute_pipe(tp) * 2))))
tp->ccv->flags |= CCF_CWND_LIMITED;
else
tp->ccv->flags &= ~CCF_CWND_LIMITED;

4
sys/netinet/tcp_stacks/rack.c
View File

@ -1663,7 +1663,9 @@ rack_ack_received(struct tcpcb *tp, struct tcp_rack *rack, struct tcphdr *th, ui
tp->ccv->bytes_this_ack = max;
}
}
if (tp->snd_cwnd <= tp->snd_wnd)
if ((!V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd)) ||
(V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd) &&
(tp->snd_cwnd < (ctf_flight_size(tp, rack->r_ctl.rc_sacked) * 2))))
tp->ccv->flags |= CCF_CWND_LIMITED;
else
tp->ccv->flags &= ~CCF_CWND_LIMITED;

2
sys/netinet/tcp_var.h
View File

@ -767,6 +767,7 @@ VNET_DECLARE(int, tcp_delack_enabled);
VNET_DECLARE(int, tcp_do_autorcvbuf);
VNET_DECLARE(int, tcp_do_autosndbuf);
VNET_DECLARE(int, tcp_do_ecn);
VNET_DECLARE(int, tcp_do_newcwv);
VNET_DECLARE(int, tcp_do_rfc1323);
VNET_DECLARE(int, tcp_do_rfc3042);
VNET_DECLARE(int, tcp_do_rfc3390);
@ -789,6 +790,7 @@ VNET_DECLARE(int, tcp_sendspace);
VNET_DECLARE(struct inpcbhead, tcb);
VNET_DECLARE(struct inpcbinfo, tcbinfo);
#define V_tcp_do_newcwv VNET(tcp_do_newcwv)
#define V_drop_synfin VNET(drop_synfin)
#define V_path_mtu_discovery VNET(path_mtu_discovery)
#define V_tcb VNET(tcb)