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rtsol/rtsold: Add option to skip random delay

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In accordance with a SHOULD in RFC 4861, rtsol and rtsold wait a
random time between zero and one (aka MAX_RTR_SOLICITATION_DELAY)
seconds before sending a Router Solicitation, in order to avoid
network congestion if many hosts come online at once.  (The
question of how many hosts would be required to cause congestion
by each sending a single packet on a Gbps+ network is left to the
reader.)

The new option -i disables this wait and instructs rtsol and rtsold
to send the Router Solicitation immediately.

Reviewed by:	bz, kp (earlier version)
MFC after:	1 week
Relnotes:	yes
Sponsored by:	https://www.patreon.com/cperciva
Differential Revision:	https://reviews.freebsd.org/D32956
This commit is contained in:
Colin Percival 2021-11-16 10:24:05 -08:00
parent 57a8fa6f01
commit 231bac4ccc
2 changed files with 21 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

16
usr.sbin/rtsold/rtsold.8
View file

@ -29,7 +29,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd August 14, 2021
.Dd November 12, 2021
.Dt RTSOLD 8
.Os
.\"
@ -39,27 +39,27 @@
.\"
.Sh SYNOPSIS
.Nm
.Op Fl dDfFmu1
.Op Fl dDfFimu1
.Op Fl M Ar script-name
.Op Fl O Ar script-name
.Op Fl p Ar pidfile
.Op Fl R Ar script-name
.Ar interface ...
.Nm
.Op Fl dDfFmu1
.Op Fl dDfFimu1
.Op Fl M Ar script-name
.Op Fl O Ar script-name
.Op Fl p Ar pidfile
.Op Fl R Ar script-name
.Fl a
.Nm rtsol
.Op Fl dDu
.Op Fl dDiu
.Op Fl M Ar script-name
.Op Fl O Ar script-name
.Op Fl R Ar script-name
.Ar interface ...
.Nm rtsol
.Op Fl dDu
.Op Fl dDiu
.Op Fl M Ar script-name
.Op Fl O Ar script-name
.Op Fl R Ar script-name
@ -194,6 +194,12 @@ The settings may be changed manually with
.Xr sysctl 8
and
.Xr ifconfig 8 .
.It Fl i
Transmit Router Solicitation packets immediately, without waiting the
normal random (between 0 and 1 second) delay.
This option should not be used on networks where it might result in
congestion due to many hosts simultaneously (re)connecting and
sending such packets.
.It Fl m
Enable mobility support.
If this option is specified,

13
usr.sbin/rtsold/rtsold.c
View file

@ -99,6 +99,7 @@ cap_channel_t *capllflags, *capscript, *capsendmsg, *capsyslog;
/* static variables and functions */
static int mobile_node = 0;
static int no_solicitation_delay = 0;
static sig_atomic_t do_dump, do_exit;
static struct pidfh *pfh;
@ -125,11 +126,11 @@ main(int argc, char **argv)
progname = basename(argv[0]);
if (strcmp(progname, "rtsold") == 0) {
opts = "adDfFm1M:O:p:R:u";
opts = "adDfFim1M:O:p:R:u";
once = 0;
pidfilepath = NULL;
} else {
opts = "adDFM:O:R:u";
opts = "adDFiM:O:R:u";
fflag = 1;
once = 1;
}
@ -151,6 +152,9 @@ main(int argc, char **argv)
case 'F':
Fflag = 1;
break;
case 'i':
no_solicitation_delay = 1;
break;
case 'm':
mobile_node = 1;
break;
@ -717,7 +721,10 @@ rtsol_timer_update(struct ifinfo *ifi)
ifi->timer = tm_max; /* stop timer(valid?) */
break;
case IFS_DELAY:
interval = arc4random_uniform(MAX_RTR_SOLICITATION_DELAY * MILLION);
if (no_solicitation_delay)
interval = 0;
else
interval = arc4random_uniform(MAX_RTR_SOLICITATION_DELAY * MILLION);
ifi->timer.tv_sec = interval / MILLION;
ifi->timer.tv_nsec = (interval % MILLION) * 1000;
break;