started dns parser anew

pure-parser.js

@@ -0,0 +1,235 @@
+'use strict';
+
+// pass a terminal arg
+var filename = process.argv[2];
+if (!filename) {
+  console.error("Usage: node aj-listener.js <type> [count]");
+  console.error("Example: node aj-listener.js _service 0");
+  process.exit(1);
+}
+
+
+var PromiseA = require('bluebird');
+var fs = PromiseA.promisifyAll(require('fs'));
+
+fs.readFileAsync(filename, null).then(function (nb) {
+  // nb is a Uint8Array (ArrayBufferView) for nb.buffer
+  // nb.buffer is the actual ArrayBuffer
+  pdns.unpack(nb.buffer);
+});
+
+var pdns = module.exports;
+
+// Order http://www.zytrax.com/books/dns/ch15/
+
+pdns.unpackHeader = function (i) {
+  // i is one element from a Uint16Array (as a 16-bit unsigned integer)
+
+  var header = {
+    qr:     (i & 0x8000) >> 15  // Query Response (0 is question, 1 is response)
+  , opcode: (i & 0x7800) >> 11  // 0 is question
+  , aa:     (i &  0x400) >> 10  // Authoritative Answer (response-only)
+  , tc:     (i &  0x200) >> 9   // TrunCated - expect another packet with same (?) id
+  , rd:     (i &  0x100) >> 8   // Recursion Desired
+
+  , ra:     (i &  0x80) >> 7
+  , res1:   (i &  0x40) >> 6 // z
+  , res2:   (i &  0x20) >> 5 // ad
+  , res3:   (i &  0x10) >> 4 // cd
+  , rcode:  (i &   0xF)         // Error Code (response-only)
+  };
+
+  return header;
+};
+
+pdns.packHeader = function(h) {
+  var val = 0;
+
+  val += (h.qr << 15) & 0x8000;
+  val += (h.opcode << 11) & 0x7800;
+  val += (h.aa << 10) & 0x400;
+  val += (h.tc << 9) & 0x200;
+  val += (h.rd << 8) & 0x100;
+  val += (h.ra << 7) & 0x80;
+  val += (h.res1 << 6) & 0x40;
+  val += (h.res2 << 5) & 0x20;
+  val += (h.res3 << 4) & 0x10;
+  val += h.rcode & 0xF;
+
+  return val;
+};
+
+pdns.unpackQname = function (ui8) {
+  var total = 0;
+  var i;
+
+  var len;
+  var q = {
+    byteLength: 0
+  , name: ''
+  , type: 0
+  , class: 0
+  };
+  var str = [];
+
+  do {
+    len = ui8[total];
+    //str.length = 0; // fast empty array
+    if (ui8.byteLength - total < len) {
+      throw new Error(
+        "Expected a string of length " + len
+          + " but packet itself has " + (ui8.byteLength - total) + " bytes remaining"
+      );
+    }
+    for (i = 0; i < len; i += 1) {
+      total += 1;
+      // TODO check url-allowable characters
+      str.push(String.fromCharCode(ui8[total]));
+    }
+    total += 1;
+    if (ui8[total]) {
+      // pushd connecting '.', but not trailing
+      str.push('.');
+    }
+    //console.log('total', total, ui8[total], String.fromCharCode(ui8[total]));
+  } while (len);
+
+  //str.pop(); // remove trailing '.'
+
+  q.name = str.join('');
+
+  return q;
+};
+
+pdns.unpack = function (ab) {
+  if (ab.buffer) {
+    ab = ab.buffer;
+  }
+
+  // SANITY Check
+  if (ab.byteLength < 12) {
+    throw new Error(
+      "A DNS header has a minimum length of 12 bytes but this packet has only " + ab.byteLength + "bytes."
+    );
+  }
+
+  // DO: new Uint8Array(arrayBuffer);
+  // DO NOT: Uint8Array.from(arrayBuffer); // WILL NOT WORK
+
+  // DO: new DataView(arrayBuffer).getUint16(7);
+  // DO NOT: arrayBuffer.slice();
+  //
+  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer
+  // https://developer.mozilla.org/en-US/docs/Web/API/ArrayBufferView
+  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array
+  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/slice
+
+  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView
+  var dv = new DataView(ab);
+  var id = dv.getUint16(0);
+  var header = pdns.unpackHeader(dv.getUint16(2));
+  var qdcount = dv.getUint16(4);  // query count
+  var ancount = dv.getUint16(6);  // answer count
+  var nscount = dv.getUint16(8);  // authority count
+  var arcount = dv.getUint16(10); // additional count
+  var total = 12;
+  var data;
+  var i;
+  var q;
+
+  //console.log('datalen', data.length);
+  console.log(dv, qdcount);
+
+  // TODO move to pdns.unpackQuestion to make testable
+  function unpackQuestion() {
+    data = new Uint8Array(ab).slice(total);
+    q = pdns.unpackQname(data);
+    total += q.name.length + 2; // account for leading and trailing string length byte
+
+
+    if (ab.byteLength - total < 4) {
+      // console.error(str.join(''));
+      throw new Error(
+        "Expected a 2-byte QTYPE and 2-byte QCLASS following " + total + "-byte QNAME"
+          + " but packet itself has " + (ab.byteLength - total) + " bytes remaining"
+      );
+    }
+
+    q.type = dv.getUint16(total);
+    console.log('type', q.type, total);
+    total += 2;
+    q.class = dv.getUint16(total);
+    console.log('class', q.class, total);
+    total += 2;
+    console.log('total', total);
+
+    header.questions.push(q);
+  }
+
+  function unpackAnswer(answers) {
+    data = new Uint8Array(ab).slice(total);
+    q = pdns.unpackQname(data);
+    total += q.name.length + 2; // account for leading and trailing string length byte
+
+
+    if (ab.byteLength - total < 10) {
+      // console.error(str.join(''));
+      throw new Error(
+        "Expected a 2-byte QTYPE, 2-byte QCLASS, 4-byte TTL, and 2-byte RDLENGTH following " + total + "-byte QNAME"
+          + " but packet itself has " + (ab.byteLength - total) + " bytes remaining"
+      );
+    }
+
+    q.type = dv.getUint16(total);
+    console.log('type', q.type, total);
+
+    total += 2;
+    q.class = dv.getUint16(total);
+    console.log('class', q.class, total);
+
+    total += 2;
+    q.ttl = dv.getUint32(total);
+    console.log('ttl', q.ttl, total);
+
+    total += 4;
+    q.rdlength = dv.getUint16(total);
+    console.log('rdlength', q.rdlength, total);
+
+    total += 2;
+    // TODO actually parse rdata
+    q.rdata = new Uint8Array(ab).slice(ab.byteLength - total, ab.byteLength + -total + q.rdlength);
+    q.rdata = Array.prototype.slice(q.data);
+    console.log('total', total);
+
+    total += q.rdlength;
+    console.log('total', total);
+
+    answers.push(q);
+  }
+
+  console.log('qdcount', qdcount);
+  header.questions = [];
+  for (i = 0; i < qdcount; i += 1) {
+    unpackQuestion();
+  }
+
+  console.log('ancount', ancount);
+  header.answers = [];
+  for (i = 0; i < ancount; i += 1) {
+    unpackAnswer(header.answers);
+  }
+
+  console.log('nscount', nscount);
+  header.authority = [];
+  for (i = 0; i < nscount; i += 1) {
+    unpackAnswer(header.authority);
+  }
+
+  console.log('arcount', arcount);
+  header.additional = [];
+  for (i = 0; i < arcount; i += 1) {
+    unpackAnswer(header.additional);
+  }
+
+  console.log('packet', header);
+};