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# delete a route from the kernel's table

sub route_delete($)
{
	my($rkey) = @_;
	
	# This is ugly and slow - we fork /sbin/ip twice for every route change.
	# Should talk to the netlink device instead, but this is easier to
	# do right now, and good enough for this little routing table.
	my($out, $cmd);
	$cmd = "LANG=C $routebin route del $rkey";
	$out = `$cmd 2>&1`;
	if ($?) {
		if ($verbose > 1 || $out !~ /No such process/) {
			warn "route del failed: '$cmd': $out\n";
		}
	}
}

# expire old routes

sub expire_routes()
{
	warn "expiring old routes\n" if ($verbose);
	
	my $exp_t = time() - $route_ttl;
	my $now = time();
	
	foreach my $rkey (keys %current_routes) {
		if ($current_routes{$rkey}->{'t'} < $exp_t) {
			# expire route
			warn "route $rkey has expired, deleting\n" if ($verbose);
			route_delete($rkey);
			delete $current_routes{$rkey};
		} elsif ($current_routes{$rkey}->{'t'} > $now) {
			# clock has jumped backwards, the time is in
			# the future - set 't' to $now so that the route
			# will be expired eventually
			$current_routes{$rkey}->{'t'} = $now;
		}
	}
}

# Consider adding a route in the routing table

sub consider_route($$$$)
{
	my($net, $mask, $nexthop, $rtag) = @_;
	
	my $rkey = "$net/$mask";
	if (defined $current_routes{$rkey}
		&& $current_routes{$rkey}->{'nh'} eq $nexthop
		&& $current_routes{$rkey}->{'rtag'} eq $rtag) {
		# ok, current route is fine
		warn "route $rkey is installed and current\n" if ($verbose > 1);
		$current_routes{$rkey}->{'t'} = time();
		return;
	}
	
	warn "route $rkey updated: via $nexthop rtag $rtag\n" if ($verbose > 1);
	
	$current_routes{$rkey} = {
		'nh' => $nexthop,
		'rtag' => $rtag,
		't' => time()
	};
	
	# now go and update the routing table
	route_delete($rkey);
	my($out, $cmd);
	$cmd = "LANG=C $routebin route add $rkey via $nexthop dev $tunnel_if window $tcp_window onlink";
	$out = `$cmd 2>&1\n`;
	if ($?) {
		warn "route add failed: '$cmd': $out\n";
	}
}

# process a RIPv2 password authentication entry

sub process_rip_auth_entry($)
{
	my($entry) = @_;
	
	my $e_af = unpack('n', substr($entry, 0, 2));
	if ($e_af != 0xFFFF) {
		warn "RIPv2 first message does not contain auth password: ignoring\n" if ($verbose);
		return 0;
	}
	
	my $e_type = unpack('n', substr($entry, 2, 2));
	if ($e_type != RIP_AUTH_PASSWD) {
		warn "ignoring unsupported rip auth type $e_type\n" if ($verbose);
		return 0;
	}
	
	my $e_passwd = substr($entry, 4, 16);
	$e_passwd =~ s/\0*$//; # it's null-padded in the end
	
	if (!defined $rip_passwd) {
		warn "RIPv2 packet contains password $e_passwd but we require none\n" if ($verbose);
		return 0;
	}
	
	if ($e_passwd ne $rip_passwd) {
		warn "RIPv2 invalid password $e_passwd\n" if ($verbose);
		return 0;
	}
	
	return 1;
}

# validate a route entry, make sure we can rather safely
# insert it in the routing table

sub validate_route($$$$$)
{
	my($e_net_i, $e_net_s, $e_netmask, $e_netmask_s, $e_nexthop_s) = @_;
	
	# netmask is correct and not too wide
	my $prefix_len = mask2prefix($e_netmask);