--- bin/dhcpd.pl	2009/07/29 00:59:55	28
+++ bin/dhcpd.pl	2009/07/29 13:03:39	36
@@ -10,6 +10,7 @@
 use IO::Socket::INET;
 use File::Slurp;
 use Data::Dump qw/dump/;
+use Net::Ping;
 
 use lib 'lib';
 use Net::DHCP::Packet;
@@ -60,17 +61,22 @@
 
 	mkdir $_ foreach grep { ! -e $_ } map { "$conf/$_" } ( 'ip', 'mac' );
 
+	my $p = Net::Ping->new;
+
 	my $prefix = $server_ip;
 	$prefix =~ s{\.\d+$}{.};
 	my $ip = $prefix . $addr;
-	while ( -e "conf/ip/$ip" ) {
+	while ( -e "conf/ip/$ip" || $p->ping( $ip ) ) {
 		$ip = $prefix . $addr++;
 		die "all addresses allocated!" if $addr == $ip_to;
 	}
 
 	write_file "$conf/mac/$mac", $ip;
-	unlink     "$conf/ip/$ip" if -e "$conf/ip/$ip";
-	symlink    "$conf/mac/$mac", "$conf/ip/$ip";
+	if ( -l "$conf/ip/$ip" && readlink "$conf/ip/$ip" ne "$conf/mac/$mac") {
+		unlink     "$conf/ip/$ip";
+		symlink    "$conf/mac/$mac", "$conf/ip/$ip";
+		warn "$mac IP changed to $ip";
+	}
 
 	print "$mac NEW $ip\n";