Function readDomainFromPacket

test/common/dns.js:27–50

(buffer, offset)

// Naïve DNS parser/serializer.

function readDomainFromPacket(buffer, offset) {
  assert.ok(offset < buffer.length);
  const length = buffer[offset];
  if (length === 0) {
    return { nread: 1, domain: '' };
  } else if ((length & 0xC0) === 0) {
    offset += 1;
    const chunk = buffer.toString('ascii', offset, offset + length);
    // Read the rest of the domain.
    const { nread, domain } = readDomainFromPacket(buffer, offset + length);
    return {
      nread: 1 + length + nread,
      domain: domain ? `${chunk}.${domain}` : chunk,
    };
  }
  // Pointer to another part of the packet.
  assert.strictEqual(length & 0xC0, 0xC0);
  // eslint-disable-next-line @stylistic/js/space-infix-ops, @stylistic/js/space-unary-ops
  const pointeeOffset = buffer.readUInt16BE(offset) &~ 0xC000;
  return {
    nread: 2,
    domain: readDomainFromPacket(buffer, pointeeOffset),
  };
}

function parseDNSPacket(buffer) {
  assert.ok(buffer.length > 12);