Re: [LARTC] Perl script to adjust default routing on 2 Net connections

[Whit Blauvelt <whit@transpect.com>]

Slightly updated - the "die" error catchers didn't always do what I
expected, so gone for now. Otherwise this has been behaving well.

Whit

--- cut --- 

#!/usr/local/bin/perl

# checkroutes.pl version 0.05, 18 Feb. 2002, whit@transpect.com
# changed from 0.04: (1) removed disfunctional "die" statements
#                    (2) added double check that for extra "default"

# Extends stock Nano-Howto setup with upstream route accessibility checking
# See http://www.linuxvirtualserver.org/~julian/nano.txt and patches at
# http://www.linuxvirtualserver.org/~julian/#routes
# (if not using Julian's patchs, remove "proto static" occurrences below)

# Run from cron (set with "crontab -e")
# example: "0-59/2 * * * * /path/to/checkroutes.pl" runs this every 2 minutes

# Best IPs to test may be last IPs at ISP before routing out to Net

# If perl not at /usr/local/bin/perl change first line to point to it

# Before running install Net::Ping from http://freeware.roobik.com/netping/
# (untar, cd to directory, "perl Makefile.PL; make; make install")

use Net::Ping;

# User settings
# _____________

$ip	= "/usr/sbin/ip";	# Location of "ip" on system

$gw1 	= "";	# Gateway 1 IP
$dev1	= "";		# Device (e.g., eth1)
$tip1	= "";	# Upstream IP to test
$src1	= "";	# Source address for outgoing packets
$wei1	= "";			# Weight

$gw2	= "";	# Gateway 2 IP
$dev2	= "";		# Device (e.g., eth2)
$tip2	= "";	# Upstream IP to test
$src2	= "";	# Source address for outgoing packets
$wei2	= "";			# Weight

$tab	= "222";		# Table to set routes in

$logfile = "/var/log/checkroutes.log"; # File to log messages to 

# create timestamp for log
# ________________________

sub TimeStamp {

	# subroutine to create a "nice" looking timestamp
	# that doesn't rely on the system's 'date' command

	my @days = ('Sun','Mon','Tue','Wed','Thu','Fri','Sat');
	my @months = ('Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep',
		'Oct','Nov','Dec');

	my ($sec,$min,$hour,$dom,$mon,$year,$wday,$yday,$isd) = localtime(time);
	my $timestamp = sprintf("%3s %3s %02d %4d  %02d:%02d:%02d", $days[$wday],
		$months[$mon], $dom, $year+1900, $hour, $min, $sec);

	return $timestamp;
} 

# be sure routes are set via appropriate gateways to test IPs 
# ___________________________________________________________

$checkro = `$ip ro ls`;
if (!($checkro =~ /$tip1/)) {
	system ("$ip ro add to $tip1 via $gw1 src $src1 proto static");
}
if (!($checkro =~ /$tip2/)) {
	system ("$ip ro add to $tip2 via $gw2 src $src2 proto static");
}

# test if $gw1 and/or $gw2 currently in table $tab
# ________________________________________________

$checkgw = qx/$ip ro ls tab $tab/;

if ($checkgw =~ /$gw1/) {
	$check1 = 1;
} else {
	$check1 = 0;
}

if ($checkgw =~ /$gw2/) {
	$check2 = 1;
} else {
	$check2 = 0;
}

# ping the test IPs $tip1 and $tip2
# _________________________________

$p = Net::Ping->new("icmp");
if ($p->ping($tip1)) {
	$live1 = 1;
} else {
	$live1 = 0;
}
$p->close();
$p = Net::Ping->new("icmp");
if ($p->ping($tip2)) {
	$live2 = 1;
} else {
	$live2 = 0;
}
$p->close();

# If the current default in table $tab does not match the ping results then
# if only one route's test IP is pingable change the default to that route
# or if both test IPs are pingable change the default to use both
# or if neither test IPs are pingable change the default to use both 
# (might as well continue to try them, if we're not going anywhere anyway)
# _________________________________________________________________________

if (($check1 != $live1)||($check2 != $live2)) {
	if ((($live1 = 1)&&($live2 = 1))||(($live1 = 0)&&($live2 = 0))) {
		system ("$ip ro ap default tab $tab proto static nexthop via $gw1 dev $dev1 weight $wei1 nexthop via $gw2 dev $dev2 weight $wei2");
	} elsif (($live1 = 1)&&($live2 = 0)) {
		system ("$ip ro ap default tab $tab proto static via $gw1 dev $dev1");
	} elsif (($live1 = 0)&&($live2 = 1)) {
		system ("$ip ro ap default tab $tab proto static via $gw2 dev $dev2");
	} else {
		die ("value out of bounds\n");
	}
	system ("$ip ro del default tab $tab");
	system ("$ip ro flush cache");
}

# log
# ___

if (($live1 = 1)&&($live2 = 1)) {
	$log = "both UP";
} elsif (($live1 = 0)&&($live2 = 0)) {
	$log = "both DOWN (set UP)";
} elsif (($live1 = 1)&&($live2 = 0)) {
	$log = "$gw1 up, $gw2 DOWN";
} elsif (($live1 = 0)&&($live2 = 1)) {
	$log = "$gw2 up, $gw1 DOWN";
}

open(LOG, ">>$logfile");
print LOG &TimeStamp . " - $log\n";
close(LOG);

# double check that only one default is set
# _________________________________________

$checkdup = qx/$ip ro ls tab $tab/;
if ($checkdup =~ /default.*default/s) {
	system ("$ip ro del default tab $tab");
}
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