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Add a sysctl variable ts_offset_per_conn to change the computation

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of the TCP TS offset from taking the IP addresses and the TCP port
numbers into account to a version just taking only the IP addresses
into account. This works around broken middleboxes or endpoints.
The default is to keep the behaviour, which is also the behaviour
recommended in RFC 7323.

Reported by:		devgs@ukr.net
Reviewed by:		rrs@
MFC after:		2 weeks
Sponsored by:		Netflix, Inc.
Differential Revision:	https://reviews.freebsd.org/D20980
This commit is contained in:
Michael Tuexen 2019-07-23 21:28:20 +00:00
parent 051e692a99
commit d21036e033
3 changed files with 22 additions and 2 deletions
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6
share/man/man4/tcp.4
View File

@ -34,7 +34,7 @@
.\" From: @(#)tcp.4 8.1 (Berkeley) 6/5/93
.\" $FreeBSD$
.\"
.Dd March 23, 2019
.Dd July 23, 2019
.Dt TCP 4
.Os
.Sh NAME
@ -606,6 +606,10 @@ Default is false.
.It Va insecure_syn
Use criteria defined in RFC793 instead of RFC5961 for accepting SYN segments.
Default is false.
.It Va ts_offset_per_conn
When initializing the TCP timestamps, use a per connection offset instead of a
per host pair offset.
Default is to use per connection offsets as recommended in RFC 7323.
.El
.Sh ERRORS
A socket operation may fail with one of the following errors returned:

17
sys/netinet/tcp_subr.c
View File

@ -195,6 +195,11 @@ SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(tcp_do_rfc1323), 0,
"Enable rfc1323 (high performance TCP) extensions");
VNET_DEFINE(int, tcp_ts_offset_per_conn) = 1;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, ts_offset_per_conn, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(tcp_ts_offset_per_conn), 0,
"Initialize TCP timestamps per connection instead of per host pair");
static int tcp_log_debug = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_debug, CTLFLAG_RW,
&tcp_log_debug, 0, "Log errors caused by incoming TCP segments");
@ -2634,7 +2639,17 @@ tcp_keyed_hash(struct in_conninfo *inc, u_char *key, u_int len)
uint32_t
tcp_new_ts_offset(struct in_conninfo *inc)
{
return (tcp_keyed_hash(inc, V_ts_offset_secret,
struct in_conninfo inc_store, *local_inc;
if (!V_tcp_ts_offset_per_conn) {
memcpy(&inc_store, inc, sizeof(struct in_conninfo));
inc_store.inc_lport = 0;
inc_store.inc_fport = 0;
local_inc = &inc_store;
} else {
local_inc = inc;
}
return (tcp_keyed_hash(local_inc, V_ts_offset_secret,
sizeof(V_ts_offset_secret)));
}

1
sys/netinet/tcp_var.h
View File

@ -802,6 +802,7 @@ VNET_DECLARE(struct inpcbinfo, tcbinfo);
#define V_tcp_do_autosndbuf VNET(tcp_do_autosndbuf)
#define V_tcp_do_ecn VNET(tcp_do_ecn)
#define V_tcp_do_rfc1323 VNET(tcp_do_rfc1323)
#define V_tcp_ts_offset_per_conn VNET(tcp_ts_offset_per_conn)
#define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042)
#define V_tcp_do_rfc3390 VNET(tcp_do_rfc3390)
#define V_tcp_do_rfc3465 VNET(tcp_do_rfc3465)