#! /usr/bin/perl -w

# John Hay -- John.Hay@icomtek.csir.co.za / jhay@FreeBSD.org

use Socket;
use Getopt::Std;
use vars qw($opt_n $opt_m);

$ntpq = "ntpq";

$Getopt::Std::STANDARD_HELP_VERSION=1;
getopts('nm:');

$dodns = 1;
$dodns = 0 if (defined($opt_n));

$max_hosts = (defined($opt_m) ? $opt_m :  99);
$max_hosts = 0 if ( $max_hosts !~ /^\d+$/ );
$nb_host = 1;

$host = shift;
$host ||= "127.0.0.1";

for (;;) {
	$nb_host++;
	$rootdelay = 0;
	$rootdispersion = 0;
	$stratum = 255;
	$cmd = "$ntpq -n -c rv $host";
	open(PH, $cmd . "|") || die "failed to start command $cmd: $!";
	while (<PH>) {
		$stratum = $1 if (/stratum=(\d+)/);
		$peer = $1 if (/peer=(\d+)/);
		# Very old servers report phase and not offset.
		$offset = $1 if (/(?:offset|phase)=([^\s,]+)/);
		$rootdelay = $1 if (/rootdelay=([^\s,]+)/);
		$rootdispersion = $1 if (/rootdispersion=([^\s,]+)/);
		$refid = $1 if (/refid=([^\s,]+)/);
	}
	close(PH) || die "$cmd failed";
	last if ($stratum == 255);
	$offset /= 1000;
	$syncdistance = ($rootdispersion + ($rootdelay / 2)) / 1000;
	$dhost = $host;
	# Only do lookups of IPv4 addresses. The standard lookup functions
	# of perl only do IPv4 and I don't know if we should require extras.
	if ($dodns && $host =~ /^(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})$/) {
		$iaddr = inet_aton($host);
		$name = (gethostbyaddr($iaddr, AF_INET))[0];
		$dhost = $name if (defined($name));
	}
	printf("%s: stratum %d, offset %f, synch distance %f",
	    $dhost, $stratum, $offset, $syncdistance);
	printf(", refid '%s'", $refid) if ($stratum == 1);
	printf("\n");
	last if ($stratum == 0 || $stratum == 1 || $stratum == 16);
	last if ($refid =~ /^127\.127\.\d{1,3}\.\d{1,3}$/);
	last if ($nb_host > $max_hosts);

	$cmd = "$ntpq -n -c \"pstat $peer\" $host";
	open(PH, $cmd . "|") || die "failed to start command $cmd: $!";
	$thost = "";
	while (<PH>) {
		$thost = $1, last if (/srcadr=(\S+),/);
	}
	close(PH) || die "$cmd failed";
	last if ($thost eq "");
	last if ($thost =~ /^127\.127\.\d{1,3}\.\d{1,3}$/);
	$host = $thost;
}