<?php
require_once './marccore.php';

$dns_opcode = array(0 => 'QUERY', 1 => 'IQUERY', 2 => 'STATUS');
$dns_responsecode = array(0 => 'NOERROR', 1 => 'FORMERR', 2 => 'SERVFAIL', 3 => 'NXDOMAIN', 4 => 'NOTIMPL', 5 => 'REFUSED');
$dns_rr_class = array(1 => 'IN', 2 => 'CS', 3 => 'CH', 4 => 'HS', 255 => 'ANY');
$dns_rr_type = array(1 => 'A', 2 => 'NS', 5 => 'CNAME', 6 => 'SOA', 10 => 'NULL', 12 => 'PTR', 15 => 'MX', 16 => 'TXT', 28 => 'AAAA', 252 => 'AXFR', 255 => 'ANY');
$dns_opcode_rev = array_flip($dns_opcode);
$dns_responsecode_rev = array_flip($dns_responsecode);
$dns_rr_class_rev = array_flip($dns_rr_class);
$dns_rr_type_rev = array_flip($dns_rr_type);

error_reporting(E_ALL);

if (!isset($argv)) $argv = $_SERVER['argv'];
if (count($argv) < 3) {
	echo "Usage: ".$argv[0]." [marc-flatfile-database-filename] [listen-ip-address] [listen-port-number]\n";
	die();
}

$dbfile = $argv[1];
$listenaddress = $argv[2];
$listenport = $argv[3];

$database = new MARCDatabaseFlatFile();

function dbreload() {
	global $database, $dbfile;
	$database->Open($dbfile);
	$database->Close();
}

dbreload();

$socket = socket_create(strpos($listenaddress, ':') === FALSE ? AF_INET : AF_INET6, SOCK_DGRAM, SOL_UDP);
socket_bind($socket, $listenaddress, $listenport);

while (true) {
	$buffer = $remoteaddr = $remoteport = NULL;
	$readlen = socket_recvfrom($socket, $buffer, 0xFFFF, 0, $remoteaddr, $remoteport);
	if ($readlen === FALSE) continue;
	$buffer = dns_process($buffer, $remoteaddr);
	if ($buffer === FALSE) continue;
	socket_sendto($socket, $buffer, strlen($buffer), 0, $remoteaddr, $remoteport);
}

function dns_process($reqbuffer, $remoteaddr) {
	$req = dns_decode($reqbuffer);
	if ($req['isresponse']) return;
	$res = array('id' => $req['id'], 'isresponse' => true, 'opcode' => $req['opcode'], 'responsecode' => 'NOERROR', 'recursiondesired' => $req['recursiondesired'], 'question' => $req['question'], 'answer' => array(), 'authority' => array(), 'additional' => array());
	if ($req['opcode'] != 'QUERY') {
		$res['responsecode'] = 'NOTIMPL';
	} else {
		foreach ($req['question'] as $q) {
			if ($q['class'] == 'IN') {
				if (dns_get_response($res, $q)) {
					$res['authoritative'] = true;
				} else {
					$res['responsecode'] = 'NXDOMAIN';
				}
			} else if ($q['class'] == 'CH' && $q['type'] == 'TXT') {
				switch ($q['name']) {
					case 'version.bind': $res['answer'][] = array('name' => $q['name'], 'class' => $q['class'], 'type' => $q['type'], 'value' => 'UCIS MARNS - http://www.ucis.nl'); break;
					case 'reload.marns':
						if ($remoteaddr == '127.0.0.1' || $remoteaddr == '::1' || $remoteaddr == $GLOBALS['listenaddress']) {
							dbreload();
							$res['answer'][] = array('name' => $q['name'], 'class' => $q['class'], 'type' => $q['type'], 'value' => 'RELOAD OK');
						} else {
							$res['responsecode'] = 'REFUSED';
						}
						break;
					default: $res['responsecode'] = 'NOTIMPL'; break;
				}
			} else {
				$res['responsecode'] = 'NOTIMPL';
			}
		}
	}
	return dns_encode($res);
}

function dns_find_zone(&$name, &$zone) {
	global $database;
	$zone = strtolower(rtrim($name, '.'));
	$name = '';
	while (strlen($zone)) {
		$dbzone = $database->GetResource(chr(4).$zone);
		if ($dbzone != NULL) return $dbzone;
		$i = strpos($zone, '.');
		if ($i === FALSE) break;
		if (strlen($name)) $name .= '.';
		$name .= substr($zone, 0, $i);
		$zone = substr($zone, $i + 1);
	}
	return NULL;
}
function dns_convert_record($item, $realname, $zonename) {
		if (isset($item['class']) && strcasecmp($item['class'], 'IN')) return FALSE;
		if (!is_array($item) || !isset($item['type'])) return FALSE;
		if (strlen($realname)) $realname .= '.';
		$realname .= $zonename;
		$type = strtoupper($item['type']);
		$rr = array('name' => $realname, 'type' => $type);
		if (($type == 'A' || $type == 'AAAA') && isset($item['target'])) $rr['address'] = $item['target'];
		elseif (($type == 'CNAME' || $type == 'NS' || $type == 'PTR') && isset($item['target'])) $rr['target'] = $item['target'];
		elseif ($type == 'MX' && isset($item['target'])) { $rr['target'] = $item['target']; if (isset($item['priority'])) $rr['priority'] = $item['priority']; }
		else return FALSE;
		if (isset($rr['target'])) {
			if (!strlen($rr['target'])) $rr['target'] = $zonename;
			elseif ($rr['target'][strlen($rr['target']) - 1] != '.') $rr['target'] .= '.'.$zonename;
		}
		$rr['ttl'] = isset($item['ttl']) ? $item['ttl'] : 3600;
		return $rr;
}
function dns_find_records_real(&$response, $dbzone, $findname, $realname, $zonename, $qtype) {
	if (!isset($dbzone[$findname])) return FALSE;
	foreach ($dbzone[$findname] as $item) {
		if (!is_array($item) || !isset($item['type'])) continue;
		if (isset($item['class']) && strcasecmp($item['class'], 'IN')) continue;
		if (strcasecmp($item['type'], $qtype) && strcasecmp($qtype, 'ANY') && strcasecmp($item['type'], 'CNAME')) continue;
		$record = dns_convert_record($item, $realname, $zonename);
		if ($record === FALSE) continue;
		$response[] = $record;
	}
	return TRUE;
}
function dns_find_ns_records(&$res, $dbzone, $findname, $realname, $zonename) {
	if (!isset($dbzone[$findname])) return FALSE;
	$foundns = FALSE;
	foreach ($dbzone[$findname] as $item) {
		if (!is_array($item) || !isset($item['type'])) continue;
		if (isset($item['class']) && strcasecmp($item['class'], 'IN')) continue;
		if (strcasecmp($item['type'], 'NS')) continue;
		$record = dns_convert_record($item, $realname, $zonename);
		if ($record === FALSE) continue;
		$res['authority'][] = $record;
		if (strcasecmp(substr($record['target'], -strlen($zonename)), $zonename) == 0) dns_find_records_realwild($res['additional'], $dbzone, rtrim(substr($record['target'], 0, -strlen($zonename)), '.'), $zonename, 'ANY');
		$foundns = TRUE;
	}
	return $foundns;
}
function dns_find_records_realwild(&$res, $dbzone, $name, $zonename, $qtype) {
	if (dns_find_records_real($res, $dbzone, $name, $name, $zonename, $qtype)) return TRUE;
	$nameparts = strlen($name) ? explode('.', strtolower($name)) : array();
	for ($i = 1; $i < count($nameparts); $i++) {
		if (dns_find_records_real($res, $dbzone, '*.'.implode('.', array_slice($nameparts, $i)), $name, $zonename, $qtype)) return TRUE;
	}
	if (dns_find_records_real($res, $dbzone, '*', $name, $zonename, $qtype)) return TRUE;
	return FALSE;
}
function dns_find_records(&$res, $dbzone, $name, $zone, $qtype) {
	if (!isset($dbzone->value['dnsrecords']) || !is_array($dbzone->value['dnsrecords'])) return FALSE;
	$dbzone = $dbzone->value['dnsrecords'];
	$nameparts = strlen($name) ? explode('.', strtolower($name)) : array();
	for ($i = count($nameparts) - 1; $i >= 0; $i--) {
		$realname = implode('.', array_slice($nameparts, $i));
		if (dns_find_ns_records($res, $dbzone, $realname, $realname, $zone)) return TRUE;
		if (dns_find_ns_records($res, $dbzone, '*.'.implode('.', array_slice($nameparts, $i + 1)), $realname, $zone)) return TRUE;
	}
	return dns_find_records_realwild($res['answer'], $dbzone, $name, $zone, $qtype);
}
function dns_find_authority(&$res, $dbzone, $zone, $nsquery = FALSE) {
	if (!isset($dbzone->value['ns']) || !is_array($dbzone->value['ns'])) return FALSE;
	foreach ($dbzone->value['ns'] as $nsname => $nsglues) {
		$rr = array('name' => $zone, 'type' => 'NS', 'ttl' => 3600, 'target' => (strlen($nsname) && $nsname[strlen($nsname) - 1] != '.') ? $nsname.'.'.$zone : $nsname);
		if ($nsquery) $res['answer'][] = $rr;
		else $res['authority'][] = $rr;
		if (is_array($nsglues)) {
			foreach ($nsglues as $glue) {
				$glue = inet_pton($glue);
				if (!strlen($glue)) continue;
				$res['additional'][] = array('name' => $rr['target'], 'ttl' => 3600, 'type' => strlen($glue) == 4 ? 'A' : 'AAAA', 'data' => $glue);
			}
		}
	}
	return TRUE;
}

function dns_get_response(&$res, $q) {
	$name = $q['name'];
	$zone = '';
	$dbzone = dns_find_zone($name, $zone);
	if ($dbzone == NULL) return FALSE;
	return dns_find_records($res, $dbzone, $name, $zone, $q['type']);
	//return dns_find_authority($res, $dbzone, $zone, $q['type'] == 'NS');
}

function dns_decode_uint16be($data, $i = 0) { return (ord($data[$i+0]) << 8) | ord($data[$i+1]); }
function dns_decode_uint32be($data, $i = 0) { return (ord($data[$i]) << 24) | (ord($data[$i+1]) << 16) | (ord($data[$i+2]) << 8) | ord($data[$i+3]); }
function dns_encode_uint32be($v) { return pack("N", $v); }
function dns_encode_uint16be($v) { return pack("n", $v); }

function dns_decode($packet) {
	global $dns_opcode, $dns_responsecode;
	$flags1 = ord($packet[2]);
	$flags2 = ord($packet[3]);
	$dp = array(
		'id' => dns_decode_uint16be($packet, 0),
		'isresponse' => ($flags1 & 128) != 0,
		'opcode' => ($flags1 >> 3) & 0x0F,
		'authoritative' => ($flags1 & 4) != 0,
		'truncation' => ($flags1 & 2) != 0,
		'recursiondesired' => ($flags1 & 1) != 0,
		'recursionavailable' => ($flags2 & 128) != 0,
		'responsecode' => ($flags2 & 0x0F),
		'qdcount' => dns_decode_uint16be($packet, 4),
		'ancount' => dns_decode_uint16be($packet, 6),
		'nscount' => dns_decode_uint16be($packet, 8),
		'arcount' => dns_decode_uint16be($packet, 10),
	);
	if (isset($dns_opcode[$dp['opcode']])) $dp['opcode'] = $dns_opcode[$dp['opcode']];
	if (isset($dns_responsecode[$dp['responsecode']])) $dp['responsecode'] = $dns_responsecode[$dp['responsecode']];
	$ptr = 12;
	$dp['question'] = dns_decode_rrs($packet, $ptr, false, $dp['qdcount']);
	$dp['answer'] = dns_decode_rrs($packet, $ptr, true, $dp['ancount']);
	$dp['authority'] = dns_decode_rrs($packet, $ptr, true, $dp['nscount']);
	$dp['additional'] = dns_decode_rrs($packet, $ptr, true, $dp['arcount']);
	return $dp;
}
function dns_decode_rrs($packet, &$ptr, $isanswer, $count) {
	$ret = array();
	for ($i = 0; $i < $count; $i++) $ret[] = dns_decode_rr($packet, $ptr, $isanswer);
	return $ret;
}
function dns_decode_rr($packet, &$ptr, $isanswer) {
	global $dns_rr_class, $dns_rr_type;
	$rr = array();
	$rr['name'] = dns_decode_name($packet, $ptr);
	$rr['type'] = dns_decode_uint16be($packet, $ptr); $ptr += 2;
	$rr['class'] = dns_decode_uint16be($packet, $ptr); $ptr += 2;
	if (isset($dns_rr_class[$rr['class']])) $rr['class'] = $dns_rr_class[$rr['class']];
	if (isset($dns_rr_type[$rr['type']])) $rr['type'] = $dns_rr_type[$rr['type']];
	if ($isanswer) {
		$rr['ttl'] = dns_decode_uint32be($packet, $ptr); $ptr += 4;
		$rrdatalength = dns_decode_uint16be($packet, $ptr); $ptr += 2;
		$rr['data'] = substr($packet, $ptr, $rrdatalength);
		$dataptr = $ptr;
		$ptr += $rrdatalength;
		if ($rr['class'] == 'IN') {
			switch ($rr['type']) {
				case 'A':
				case 'AAAA':
					$rr['address'] = inet_ntop($rr['data']);
					break;
				case 'CNAME':
				case 'NS':
				case 'PTR':
					$rr['target'] = dns_decode_name($packet, $dataptr);
					break;
				case 'MX':
					$rr['priority'] = dns_decode_uint16be($packet, $dataptr); $dataptr += 2;
					$rr['target'] = dns_decode_name($packet, $dataptr);
					break;
				case 'TXT':
					$rr['value'] = dns_decode_name($packet, $dataptr);
					break;
			}
		}
	}
	return $rr;
}
function dns_decode_name($packet, &$ptr) {
	$name = '';
	$canrecurse = 64;
	while ($ptr < strlen($packet)) {
		$l = ord($packet[$ptr++]);
		if ($l == 0) break;
		if (($l & 0xC0) == 0) {
			$name .= substr($packet, $ptr, $l).'.';
			$ptr += $l;
		} else if (($l & 0xC0) == 0xC0 && $canrecurse > 0) {
			$newptr = (($l & 0x3F) << 8) | ord($packet[$ptr++]);
			$ptr = &$newptr;
			$canrecurse--;
		} else {
			return FALSE;
		}
	}
	return substr($name, 0, -1);
}

function dns_encode($dp) {
	global $dns_opcode_rev, $dns_responsecode_rev;
	$data = '';
	$qdcount = isset($dp['question']) ? count($dp['question']) : 0;
	$ancount = isset($dp['answer']) ? count($dp['answer']) : 0;
	$nscount = isset($dp['authority']) ? count($dp['authority']) : 0;
	$arcount = isset($dp['additional']) ? count($dp['additional']) : 0;
	$opcode = isset($dp['opcode']) ? $dp['opcode'] : 0;
	$responsecode = isset($dp['responsecode']) ? $dp['responsecode'] : 0;
	if (isset($dns_opcode_rev[$opcode])) $opcode = $dns_opcode_rev[$opcode];
	if (isset($dns_responsecode_rev[$responsecode])) $responsecode = $dns_responsecode_rev[$responsecode];
	$isresponse = $ancount || $nscount || $arcount || $responsecode != 0 || (isset($dp['isresponse']) && $dp['isresponse']);
	$data .= dns_encode_uint16be($dp['id']);
	$data .= chr(($isresponse ? 128 : 0) | (($opcode & 0x0F) << 3) | ((isset($dp['authoritative']) && $dp['authoritative']) ? 4 : 0) | ((isset($dp['truncation']) && $dp['truncation']) ? 2 : 0) | ((isset($dp['recursiondesired']) && $dp['recursiondesired']) ? 1 : 0));
	$data .= chr(((isset($dp['recursionavailable']) && $dp['recursionavailable']) ? 128 : 0) | ($responsecode & 0xF));
	$data .= dns_encode_uint16be($qdcount);
	$data .= dns_encode_uint16be($ancount);
	$data .= dns_encode_uint16be($nscount);
	$data .= dns_encode_uint16be($arcount);
	$labels = array();
	if ($qdcount) dns_encode_rrs($data, $dp['question'], false, $labels);
	if ($ancount) dns_encode_rrs($data, $dp['answer'], true, $labels);
	if ($nscount) dns_encode_rrs($data, $dp['authority'], true, $labels);
	if ($arcount) dns_encode_rrs($data, $dp['additional'], true, $labels);
	return $data;
}
function dns_encode_rrs(&$data, $rrs, $isanswer, &$labels) {
	global $dns_rr_type_rev, $dns_rr_class_rev;
	foreach ($rrs as $rr) {
		$rrtype = $rr['type'];
		$rrclass = isset($rr['class']) ? $rr['class'] : 1;
		if (isset($dns_rr_type_rev[$rrtype])) $rrtype = $dns_rr_type_rev[$rrtype];
		if (isset($dns_rr_class_rev[$rrclass])) $rrclass = $dns_rr_class_rev[$rrclass];
		$data .= dns_encode_name($rr['name'], $labels, strlen($data));
		$data .= dns_encode_uint16be($rrtype);
		$data .= dns_encode_uint16be($rrclass);
		if ($isanswer) {
			$rrdata = isset($rr['data']) ? $rr['data'] : '';
			if (($rrtype == 5 || $rrtype == 2 || $rrtype == 12) && isset($rr['target'])) $rrdata = dns_encode_name($rr['target'], $labels, strlen($data) + 6);
			elseif (($rrtype == 16) && isset($rr['value'])) $rrdata = dns_encode_txt($rr['value']);
			elseif ($rrtype == 15 && isset($rr['target'])) $rrdata = dns_encode_uint16be(isset($rr['priority']) ? $rr['priority'] : 0).dns_encode_name($rr['target'], $labels, strlen($data) + 8);
			elseif ($rrclass == 1) {
				if (($rrtype == 1 || $rrtype == 28) && isset($rr['address'])) $rrdata = inet_pton($rr['address']);
			}
			$rrdata = (string)$rrdata;
			$data .= dns_encode_uint32be(isset($rr['ttl']) ? $rr['ttl'] : 0);
			$data .= dns_encode_uint16be(strlen($rrdata));
			$data .= $rrdata;
		}
	}
}
function dns_encode_name($name, &$labels, $offset = FALSE) {
	$name = rtrim($name, '.');
	$data = '';
	while (strlen($name)) {
		$lname = strtolower($name);
		if (isset($labels[$lname])) {
			$ptr = $labels[$lname];
			return $data.chr(0xC0 | (($ptr >> 8) & 0x3F)).chr($ptr & 0xFF);
		} else {
			$dot = strpos($name, '.');
			if ($dot === FALSE) {
				$part = $name;
				$name = '';
			} else {
				$part = substr($name, 0, $dot);
				$name = substr($name, $dot + 1);
			}
			if (strlen($part) > 63) $part = substr($part, 0, 63);
			if ($offset !== FALSE && $offset + strlen($data) <= 0x3FFF) $labels[$lname] = strlen($data) + $offset;
			$data .= chr(strlen($part)).$part;
		}
	}
	return $data.chr(0);
}
function dns_encode_txt($parts) {
	$data = '';
	if (!is_array($parts)) $parts = array($parts);
	foreach ($parts as $part) {
		$part = (string)$part;
		if (strlen($part) > 63) $part = substr($part, 0, 63);
		$data .= chr(strlen($part)).$part;
	}
	return $data;
}