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#!/usr/bin/perl

#
# rip44d
#
# A naive custom RIPv2 daemon to receive RIP updates from the
# 44/8 ampr.org routing service, and insert them in the
# Linux routing table.
#
#
# This software is free.
# It is licensed under the EVVKTVH / ICCLEIYSIUYA license
# (public domain, no warranty of any sort).
# http://evvk.com/evvktvh.html#english
#
#
# Version history:
#
# see Changes

# Things to do in the future:
#
# - proper logging to syslog
# - support for better authentication, if one would be supported
# - support for multiple RIP masters, to fix the single point of failure
#

use strict;
use warnings;

use IO::Socket::Multicast;
use Getopt::Std;

use constant {
	RIP_HDR_LEN => 4,
	RIP_ENTRY_LEN => 2+2+4*4,
	RIP_CMD_REQUEST => 1,
	RIP_CMD_RESPONSE => 2,
	RIP_AUTH_PASSWD => 2,
	AF_INET => 2,
};

my $rip_passwd;
my $tunnel_if = 'tunl0';
my $routebin = '/sbin/ip';
my $ifconfig = '/sbin/ifconfig';
my $verbose = 0;
# Local gateway addresses (whose routes are skipped)
my %my_addresses;
# Allowed route destination networks
my $net_44_regexp = '^44\.';
# We do not accept routes less specific than /15
my $minimum_prefix_len = 15;
# tcp window to set
my $tcp_window = 840;
# time (in seconds) to use routes which are no longer advertised
# - this is set to a large value, so that if the rip advertisements
# from mirrorshades stop, the network won't go down right away.
my $route_ttl = 7*24*60*60;

my %current_routes;

my $me = 'rip44d';
my $VERSION = '1.1';

# help and version texts
$Getopt::Std::STANDARD_HELP_VERSION = 1;

sub HELP_MESSAGE()
{
	my($fh) = @_;
	
	print $fh "Usage:\n"
		. "  $me [-v] [-d] [-i <tunnelif>] [-a <localaddrs>] [-p <password>]\n"
		. "Options:\n"
		. "  -v   increase verbosity slightly to print error messages on stderr\n"
		. "  -d   increase verbosity greatly (debug mode)\n"
		. "  -i <tunnelinterface>\n"
		. "       use the specified tunnel interface, defaults to tunl0\n"
		. "  -a <comma-separated-ip-list>\n"
		. "       ignore routes pointing to these (local) gateways\n"
		. "       (list contains system's local IP addresses by default)\n"
		. "  -p <password>\n"
		. "       use RIPv2 password 'authentication', defaults to none\n"
		;
}

sub VERSION_MESSAGE()
{
	my($fh) = @_;
	
	print $fh "$me version $VERSION\n";
}

# Figure out local interface IP addresses so that routes to them can be ignored

sub fill_local_ifs()
{
	my $s = `$ifconfig -a`;
	
	while ($s =~ s/inet addr:(\d+\.\d+\.\d+\.\d+)//) {
		warn "found local address: $1\n" if ($verbose);
		$my_addresses{$1} = 1;
	}
}

# Convert a netmask (in integer form) to the corresponding prefix length,
# and validate it too. This is a bit ugly, optimizations are welcome.

sub mask2prefix($)
{
	my($mask) = @_; # integer
	
	# convert to a string of 1's and 0's, like this (/25):
	# 11111111111111111111111110000000
	my($bits) = unpack("B32", pack('N', $mask));