dns-suite.js/dns.packer.js

(function (exports) {
'use strict';

var classes = exports.DNS_CLASSES || require('./dns.classes.js').DNS_CLASSES;
var types = exports.DNS_TYPES || require('./dns.types.js').DNS_TYPES;

var dnspack = exports.DNS_PACKER = {
  pack: function (packet) {

    // TODO update for edns payload size
    var ab = new ArrayBuffer(576);                  // http://serverfault.com/a/587626/93930
    var dv = new DataView(ab);
    var labelsMap = {};
    var total = 0;
    var id = packet.header.id;                      // 2 bytes
    var header = dnspack.packHeader(packet.header); // 2 bytes
    total = 12;                                     // 2+2+2+2 bytes ({qd,an,ns,ar}count)

    if (!id) {
      throw new Error("'id' should be set to a crypto random id");
    }

    dv.setUint16(0, id, false);
    dv.setUint16(2, header, false);
    dv.setUint16(4, packet.question.length, false);
    dv.setUint16(6, (packet.answer||[]).length, false);
    dv.setUint16(8, (packet.authority||[]).length, false);
    // EDNS is added as an additional with TYPE 41 (OPT, 0x29)
    dv.setUint16(10, (packet.additional||[]).length + (packet.payload ? 1 : 0), false);

    function lint(r) {
      if (!r.name) {
        throw new Error("missing name");
      }

      if (!r.class) {
        if (!r.className) {
          throw new Error("no className");
        }
      }

      if (!r.type) {
        if (!r.typeName) {
          throw new Error("no typeName");
        }
        if (!types[r.typeName]) {
          console.warn("ignoring invalid type '" + r.type + "' for '" + r.name + "', ignoring");
        }
      }
    }

    function packLabelSequence(sequence, terminates) {
      if (labelsMap[sequence]) {
        // minimal compression pointer 0xc0 (192)
        dv.setUint8(total, 0xc0, false);
        total += 1;
        dv.setUint8(total, labelsMap[sequence].total, false);
        total += 1;
        return;
      }
      if (terminates) {
        // we don't want non-terminating rdata cached, just terminating names
        labelsMap[total] = { total: total, name: sequence };
        labelsMap[sequence] = labelsMap[total];
      }
      sequence.split('.').forEach(function (label) {
        dv.setUint8(total, label.length, false);
        total += 1;

        label.split('').forEach(function (ch) {
          dv.setUint8(total, ch.charCodeAt(0), false);
          total += 1;
        });
      });
      if (terminates) {
        // trailing 0 (null) as label sequence terminator
        dv.setUint8(total, 0, false);
        total += 1;
      }
    }

    function packQuestion(q) {
      lint(q);

      packLabelSequence(q.name, true);

      dv.setUint16(total, q.type || types[q.typeName], false);
      total += 2;
      dv.setUint16(total, q.class || classes[q.className], false);
      total += 2;
    }

    function packAnswer(a) {
      packQuestion(a);

      if ('undefined' === typeof a.ttl) {
        throw new Error("missing ttl");
      }

      // 32-bit ttl
      dv.setUint32(total, a.ttl, false);
      total += 4;

      if (a.rdata) {
        // 16-bit
        dv.setUint16(total, a.rdata.byteLength, false);
        total += 2;
        (new Uint8Array(a.rdata)).forEach(function (b) {
          dv.setUint8(total, b, false);
          total += 1;
        });
      } else {
        total = dnspack.packRdata(ab, dv, total, a);
      }
    }

    packet.question.forEach(packQuestion);
    (packet.answer||[]).forEach(packAnswer);
    (packet.authority||[]).forEach(packAnswer);
    (packet.additional||[]).forEach(packAnswer);

    // TODO handle compression pointers
    // TODO handle edns

    return ab.slice(0, total);
  }

  /*
, packLabels: function(map, labels) {
  }
  */

, packHeader: function(h) {
    var val = 0;
    var req = h.opcode;
    var res = h.qr || h.aa || h.ra || h.rcode;

    if (req && res) {
      throw new Error("Both request-only and response-only headers are set: " + JSON.stringify(h));
    }

    // TODO check if is request or response

    val += ((h.qr || 0)     << 15) & 0x8000;
    val += ((h.opcode || 0) << 11) & 0x7800;
    val += ((h.aa || 0)     << 10) &  0x400;
    val += ((h.tc || 0)     <<  9) &  0x200;
    val += ((h.rd || 0)     <<  8) &  0x100;
    val += ((h.ra || 0)     <<  7) &   0x80;
    val += ((h.res1 || 0)   <<  6) &   0x40;
    val += ((h.res2 || 0)   <<  5) &   0x20;
    val += ((h.res3 || 0)   <<  4) &   0x10;
    val += (h.rcode || 0)          &    0xF;

    return val;
  }

};
dnspack.packRdata = exports.DNS_RDATA_PACK || require('./dns.rdata.pack.js').DNS_RDATA_PACK;

}('undefined' !== typeof window ? window : exports));