253 lines
6.8 KiB
JavaScript
253 lines
6.8 KiB
JavaScript
'use strict';
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var pdns = module.exports;
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var classes = exports.DNS_CLASSES || require('./dns.classes.js').DNS_CLASSES;
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var types = exports.DNS_TYPES || require('./dns.types.js').DNS_TYPES;
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// Order http://www.zytrax.com/books/dns/ch15/
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pdns.unpackHeader = function (i) {
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// i is one element from a Uint16Array (as a 16-bit unsigned integer)
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var header = {
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id: 0 // added here to preserve console.log order
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, qr: (i & 0x8000) >> 15 // Query Response (0 is question, 1 is response)
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, opcode: (i & 0x7800) >> 11 // 0 is question
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, aa: (i & 0x400) >> 10 // Authoritative Answer (response-only)
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, tc: (i & 0x200) >> 9 // TrunCated - expect another packet with same (?) id
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, rd: (i & 0x100) >> 8 // Recursion Desired
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, ra: (i & 0x80) >> 7
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, res1: (i & 0x40) >> 6 // z
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, res2: (i & 0x20) >> 5 // ad
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, res3: (i & 0x10) >> 4 // cd
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, rcode: (i & 0xF) // Error Code (response-only)
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};
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return header;
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};
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pdns.unpackQname = function (ui8, ptr, q) {
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return pdns._unpackQname(ui8, ptr, q || {
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name: ''
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, type: 0
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, typeName: ''
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, class: 0
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, className: ''
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, byteLength: 0
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, labels: []
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, cpcount: 0
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});
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};
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pdns._unpackQname = function (ui8, ptr, q) {
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if (q.cpcount > 25) {
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throw new Error("compression pointer loop detected (over 25 pointers seems like a loop)");
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}
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var total = ptr;
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var i;
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var len;
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var label = [];
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do {
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label.length = 0;
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len = ui8[total];
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if (0xc0 === len) {
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var cpptr = ui8[total + 1];
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// we're not coming back!
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ptr = cpptr;
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q.cpcount += 1;
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q.byteLength += 2; // cp and len
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return pdns.unpackQname(ui8, ptr, q);
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}
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//str.length = 0; // fast empty array
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if (ui8.byteLength - total < len) {
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throw new Error(
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"Expected a string of length " + len
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+ " but packet itself has " + (ui8.byteLength - total) + " bytes remaining"
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);
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}
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for (i = 0; i < len; i += 1) {
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total += 1;
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// TODO check url-allowable characters
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label.push(String.fromCharCode(ui8[total]));
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}
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if (label.length) {
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q.labels.push(label.join(''));
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}
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total += 1;
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//console.log('total', total, ui8[total], String.fromCharCode(ui8[total]));
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} while (len);
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//str.pop(); // remove trailing '.'
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q.name = q.labels.join('.');
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if (0 === q.cpcount) {
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q.byteLength = total - ptr;
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}
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return q;
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};
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pdns.unpack = function (ab) {
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if (ab.buffer) {
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ab = ab.buffer;
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}
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// SANITY Check
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if (ab.byteLength < 12) {
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throw new Error(
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"A DNS header has a minimum length of 12 bytes but this packet has only " + ab.byteLength + "bytes."
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);
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}
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// DO: new Uint8Array(arrayBuffer);
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// DO NOT: Uint8Array.from(arrayBuffer); // WILL NOT WORK
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// DO: new DataView(arrayBuffer).getUint16(7);
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// DO NOT: arrayBuffer.slice();
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//
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// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer
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// https://developer.mozilla.org/en-US/docs/Web/API/ArrayBufferView
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// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array
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// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/slice
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// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView
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var dv = new DataView(ab);
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var id = dv.getUint16(0);
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var header = pdns.unpackHeader(dv.getUint16(2));
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var qdcount = dv.getUint16(4); // query count
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var ancount = dv.getUint16(6); // answer count
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var nscount = dv.getUint16(8); // authority count
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var arcount = dv.getUint16(10); // additional count
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var total = 12;
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var i;
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var rec;
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var ui8 = new Uint8Array(ab);
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// TODO move to pdns.unpackQuestion to make testable
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function unpackQuestion(ab, dv, ui8, total) {
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var ototal = total;
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var q = pdns.unpackQname(ui8, total);
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//console.log('unpackQuestion QNAME:');
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//console.log(q);
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total += q.byteLength;
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if (ab.byteLength - total < 4) {
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// console.error(str.join(''));
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throw new Error(
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"Expected a 2-byte QTYPE and 2-byte QCLASS following " + total + "-byte QNAME"
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+ " but packet itself has " + (ab.byteLength - total) + " bytes remaining"
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);
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}
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q.type = dv.getUint16(total);
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total += 2;
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q.class = dv.getUint16(total);
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total += 2;
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q.byteLength = total - ototal;
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q.className = classes[q.class];
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q.typeName = types[q.type];
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console.log('*********************');
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console.log(q.typeName);
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return q;
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}
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function unpackAnswer(ab, dv, ui8, total) {
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var ototal = total;
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var q = pdns.unpackQname(ui8, total);
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//console.log('unpackAnswer QNAME:');
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//console.log(q);
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total += q.byteLength;
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q.className = classes[q.class];
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q.typeName = types[q.type];
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if (ab.byteLength - total < 10) {
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// console.error(str.join(''));
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throw new Error(
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"Expected a 2-byte QTYPE, 2-byte QCLASS, 4-byte TTL, and 2-byte RDLENGTH following " + total + "-byte QNAME"
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+ " but packet itself has " + (ab.byteLength - total) + " bytes remaining"
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);
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}
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q.type = dv.getUint16(total);
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total += 2;
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q.class = dv.getUint16(total);
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total += 2;
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q.ttl = dv.getUint32(total);
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total += 4;
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q.rdlength = dv.getUint16(total);
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total += 2;
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q.className = classes[q.class];
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q.typeName = types[q.type];
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// TODO actually parse RDATA
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q.rdata = new Uint8Array(ab).slice(total, total + q.rdlength);
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console.log('q.rdata', q.rdata.byteLength, 'bytes:');
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console.log(q.rdata);
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//q.rdata = Array.prototype.slice.apply(q.rdata);
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total += q.rdlength;
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q.byteLength = total - ototal;
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return q;
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}
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header.id = id;
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console.log('qdcount', qdcount);
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header.questions = [];
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for (i = 0; i < qdcount; i += 1) {
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rec = unpackQuestion(ab, dv, ui8, total);
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total += rec.byteLength;
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header.questions.push(rec);
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}
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console.log('ancount', ancount);
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header.answers = [];
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for (i = 0; i < ancount; i += 1) {
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rec = unpackAnswer(ab, dv, ui8, total);
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total += rec.byteLength;
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header.answers.push(rec);
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}
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console.log('nscount', nscount);
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header.authority = [];
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for (i = 0; i < nscount; i += 1) {
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rec = unpackAnswer(ab, dv, ui8, total);
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total += rec.byteLength;
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header.authority.push(rec);
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}
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console.log('arcount', arcount);
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header.additional = [];
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for (i = 0; i < arcount; i += 1) {
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rec = unpackAnswer(ab, dv, ui8, total);
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total += rec.byteLength;
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header.additional.push(rec);
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}
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if (ab.byteLength !== total) {
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throw new Error(
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"Parsed " + total + " bytes, but packet is " + ab.byteLength + " bytes."
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);
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}
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header.byteLength = total;
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return header;
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};
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pdns.unpackRdata = require('./dns.rdata.parse.js').DNS_RDATA_PARSE;
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