started dns parser anew
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AJ ONeal
parent
4a1ea2d791
commit
d5a36adeec
235
pure-parser.js
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235
pure-parser.js
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'use strict';
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// pass a terminal arg
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var filename = process.argv[2];
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if (!filename) {
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console.error("Usage: node aj-listener.js <type> [count]");
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console.error("Example: node aj-listener.js _service 0");
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process.exit(1);
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}
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var PromiseA = require('bluebird');
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var fs = PromiseA.promisifyAll(require('fs'));
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fs.readFileAsync(filename, null).then(function (nb) {
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// nb is a Uint8Array (ArrayBufferView) for nb.buffer
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// nb.buffer is the actual ArrayBuffer
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pdns.unpack(nb.buffer);
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});
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var pdns = module.exports;
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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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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.packHeader = function(h) {
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var val = 0;
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val += (h.qr << 15) & 0x8000;
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val += (h.opcode << 11) & 0x7800;
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val += (h.aa << 10) & 0x400;
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val += (h.tc << 9) & 0x200;
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val += (h.rd << 8) & 0x100;
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val += (h.ra << 7) & 0x80;
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val += (h.res1 << 6) & 0x40;
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val += (h.res2 << 5) & 0x20;
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val += (h.res3 << 4) & 0x10;
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val += h.rcode & 0xF;
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return val;
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};
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pdns.unpackQname = function (ui8) {
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var total = 0;
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var i;
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var len;
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var q = {
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byteLength: 0
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, name: ''
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, type: 0
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, class: 0
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};
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var str = [];
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do {
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len = ui8[total];
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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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str.push(String.fromCharCode(ui8[total]));
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}
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total += 1;
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if (ui8[total]) {
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// pushd connecting '.', but not trailing
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str.push('.');
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}
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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 = str.join('');
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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 data;
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var i;
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var q;
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//console.log('datalen', data.length);
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console.log(dv, qdcount);
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// TODO move to pdns.unpackQuestion to make testable
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function unpackQuestion() {
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data = new Uint8Array(ab).slice(total);
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q = pdns.unpackQname(data);
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total += q.name.length + 2; // account for leading and trailing string length byte
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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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console.log('type', q.type, total);
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total += 2;
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q.class = dv.getUint16(total);
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console.log('class', q.class, total);
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total += 2;
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console.log('total', total);
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header.questions.push(q);
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}
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function unpackAnswer(answers) {
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data = new Uint8Array(ab).slice(total);
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q = pdns.unpackQname(data);
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total += q.name.length + 2; // account for leading and trailing string length byte
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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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console.log('type', q.type, total);
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total += 2;
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q.class = dv.getUint16(total);
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console.log('class', q.class, total);
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total += 2;
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q.ttl = dv.getUint32(total);
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console.log('ttl', q.ttl, total);
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total += 4;
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q.rdlength = dv.getUint16(total);
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console.log('rdlength', q.rdlength, total);
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total += 2;
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// TODO actually parse rdata
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q.rdata = new Uint8Array(ab).slice(ab.byteLength - total, ab.byteLength + -total + q.rdlength);
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q.rdata = Array.prototype.slice(q.data);
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console.log('total', total);
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total += q.rdlength;
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console.log('total', total);
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answers.push(q);
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}
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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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unpackQuestion();
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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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unpackAnswer(header.answers);
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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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unpackAnswer(header.authority);
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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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unpackAnswer(header.additional);
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}
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console.log('packet', header);
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};
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