#!/usr/bin/perl

# The TIMECRISIS TIME SYNC PROGRAM! YEAH! YEAH! YEAH! BOOOOOOYEAH!
# TIME SYNCH! YOU BET YOUR BE-YOOOOOOOOOOOOOUTIFUL SELF!
# There's no time like the present, and darn it, we'll drag you there!
# A Quinn Martin^W^WCameron Kaiser production, based on RFC 868

# This code is actually based on the fault-tolerant Gopher network client
# used in the helsinki-generation V-2 robot.

select(stdout);
$|++;

$TIMEOUT = 60; # longer for thule because it's slow, sigh
$MAX_SOCK_RETRIES = 5;

$NET_OK = 0;
$NET_ERROR = 1;

sub network {
	my ($them, $port) = (@_);
	local $kid;
	local $buffer;

	$kid = 0;

	die if (!length($them));
	$port ||= 37;

	my $child = open(NETW, "-|");
	if ($child) {
		my $rc;

		# parent process
		while(<NETW>) {
			$buffer .= $_;
		}
		close(NETW);
		$rc = $?;
		if ($rc) {
			return ($NET_ERROR, $buffer);
		} else {
			return ($NET_OK, $buffer);
		}
		die;
	}

	# child
	
	$SIG{'USR1'} = $SIG{'ALRM'} = sub {
		print "Timeout/user signal";
		exit 255;
	};
	$SIG{'INT'} = sub {
		print "Interrupt";
		exit 1;
	};
	alarm $TIMEOUT;

	RETRY: sleep 2 if ($sockaddr);
	$stries++;
	if ($stries >= $MAX_SOCK_RETRIES) {
		print "Repeated connect failure";
		exit 255;
	}

	$sockaddr = 'S n a4 x8';
	($name, $aliases, $type, $len, $thataddr) = gethostbyname($them);
	if (!$name) {
		print "No such server"; 
		exit 254;
	}
	$that = pack($sockaddr, 2, $port, $thataddr, 0);

	# AF_INET SOCK_STREAM IPPROTO_TCP
	socket(SOCK, 2, 1, 6) || (goto RETRY);
	if (!connect(SOCK, $that)) {
		if ($! =~ /refused/i) {
			print "connect: $!";
			exit 254;
		}
		if ($! =~ /socket name/i) {
			print "connect: $!";
			exit 254;
		}
		goto RETRY;
	}
	# Read the 32 bit network order time code.
	sysread(SOCK, $buffer, 4);
	print $buffer;
	close(SOCK);
	exit 0;
}

($rc, $data) = &network('oslo');
die("Network failure: $data\n") if ($rc != $NET_OK);
die("Time signal corrupt\n") if (length($data) != 4);

# convert to seconds past the time(1) epoch
# range 1 year of fudging to ensure we don't get crap from our server
$w = unpack("N", $data) - 2240524800; # not 2208988800 ;
die("Epoch range fault! The end of the world is near! => $w") if ($w < 1);
$w += 31536000; # 365*24*60*60; # add back one year to get the right time

$compiler = "/bin/cc";
$compiler = "/usr/bin/gcc" if (! -x $compiler);

$temp = "/tmp/settime-$$";

open(W, ">${temp}.c") || die("Unable to write $temp for timeset: $!\n");
print W <<"EOF";

#include <stdlib.h>
#include <sys/time.h>
#include <errno.h>
#include <sys/errno.h>

main(argc, argv)
int argc;
char **argv; {
	struct timeval tp;

	tp.tv_sec = $w;
	tp.tv_usec = 0;
	exit((settimeofday(&tp,0)) ? errno : 0);
}
EOF
close(W);
system("$compiler -o $temp ${temp}.c");
die("Compile step failure\n") if (! -x $temp);
system("$temp");
warn("Unable to set time: errno = $?\n") if ($?);
unlink($temp, "${temp}.c");
exit;