over-the-wire/test/DNS.test.js

Network inspection library for Node

const { strict: assert } = require('node:assert');
const test = require('node:test');

const { DNS } = require('#lib/layers/DNS');
const { DNSRecordType, DNSRecordClass } = require('#lib/layers/DNSEnums');

// Sample DNS query packet for google.com
const queryBuf = Buffer.from('00000100000100000000000006676f6f676c6503636f6d0000010001', 'hex');

// Sample DNS response packet for google.com
const responseBuf = Buffer.from('00008180000100010000000006676f6f676c6503636f6d0000010001c00c000100010000012c0004d83ad6e7', 'hex');

function roundtrip(buf, Cls = DNS) {
  const parsed = new Cls(buf);
  const obj = parsed.toObject();
  const reparsed = new Cls(obj);
  if (Buffer.compare(parsed.buffer.slice(0, reparsed.buffer.length), reparsed.buffer)) {
    console.log('roundtrip', obj, parsed.buffer.slice(0, reparsed.buffer.length), reparsed.buffer, reparsed.toObject());
  }
  assert.equal(Buffer.compare(parsed.buffer.slice(0, reparsed.buffer.length), reparsed.buffer), 0, 'buffer -> parse -> object -> buffer roundtrip');
  assert.deepEqual(reparsed.toObject(), obj, 'object roundtrip');
}

test('DNS Query', async () => {
  const dns = new DNS(queryBuf);
  assert.equal(dns.id, 0);
  assert.equal(dns.flags, 0x0100);
  assert.equal(dns.qdcount, 1);
  assert.equal(dns.ancount, 0);
  assert.equal(dns.nscount, 0);
  assert.equal(dns.arcount, 0);
  assert.ok(dns.isQuery);
  assert.equal(dns.opcode, 0);
  assert.equal(dns.recursionDesired, true);
  assert.equal(dns.recursionAvailable, false);
  assert.equal(dns.responseCode, 0);

  const query = dns.getFirstQuery();
  assert.ok(query);
  assert.equal(query.name, 'google.com');
  assert.equal(query.type, DNSRecordType.A);
  assert.equal(query.class, DNSRecordClass.IN);

  roundtrip(queryBuf);
});

test('DNS Response', async () => {
  const dns = new DNS(responseBuf);
  assert.equal(dns.id, 0);
  assert.equal(dns.flags, 0x8180);
  assert.equal(dns.qdcount, 1);
  assert.equal(dns.ancount, 1);
  assert.equal(dns.nscount, 0);
  assert.equal(dns.arcount, 0);
  assert.ok(dns.isResponse);
  assert.equal(dns.opcode, 0);
  assert.equal(dns.authoritativeAnswer, false);
  assert.equal(dns.truncation, false);
  assert.equal(dns.recursionDesired, true);
  assert.equal(dns.recursionAvailable, true);
  assert.equal(dns.responseCode, 0);

  const query = dns.getFirstQuery();
  assert.ok(query);
  assert.equal(query.name, 'google.com');
  assert.equal(query.type, DNSRecordType.A);
  assert.equal(query.class, DNSRecordClass.IN);

  const answer = dns.getFirstAnswer();
  assert.ok(answer);
  assert.equal(answer.name, 'google.com');
  assert.equal(answer.type, DNSRecordType.A);
  assert.equal(answer.class, DNSRecordClass.IN);
  assert.equal(answer.ttl, 300);
  assert.equal(answer.data.toString('hex'), 'd83ad6e7');

  roundtrip(responseBuf);
});