def test_create_domain_name_query(self):
"""
Test case to create a DNS query to ask for a particular domain name from a dns server.
"""
encoded_dns_message: BytesIO = DNSMessageUtilities.create_domain_name_query(
'www.cs.ubc.ca', 12345, 15)
encoded_dns_message.seek(
0
) # need to start reading the dns message from the start of the BytesIO object
dns_message = DNSMessage.decode_dns_message(encoded_dns_message)
# Check that the query id is correct
self.assertEqual(dns_message.query_id, 12345)
# Check that flags are correct
self.assertEqual(dns_message.is_response, False)
self.assertEqual(dns_message.opcode, 0)
self.assertEqual(dns_message.authoritative, False)
self.assertEqual(dns_message.is_truncated, False)
self.assertEqual(dns_message.recursion_desired, False)
self.assertEqual(dns_message.recursion_available, False)
self.assertEqual(dns_message.rcode, 0)
# Check that record/question counts are correct
self.assertEqual(dns_message.question_count, 1)
self.assertEqual(dns_message.answer_count, 0)
self.assertEqual(dns_message.nameserver_count, 0)
self.assertEqual(dns_message.additional_count, 0)
# Check that the question was properly decoded
self.assertEqual(dns_message.dns_questions[0].name, 'www.cs.ubc.ca')
self.assertEqual(dns_message.dns_questions[0].type, 15)
self.assertEqual(dns_message.dns_questions[0].response_class, 1)
def _handle_tracing_for_dns_query(self, domain_name_query: BytesIO,
next_dns_server_ip: str) -> None:
"""
If the resolver is set to verbose, then print tracing information for the dns query.
:param domain_name_query: the domain name query that is sent to the next_dns_server_ip.
:param next_dns_server_ip: the dns server we send the domain name query to.
:return: None
"""
if self.verbose:
print('')
print('')
domain_name_query.seek(
0) # need to ensure we are at the start of the writer
# to be able to correctly decode into a DNS Question
DNSMessage.decode_dns_message(domain_name_query).print_dns_query(
next_dns_server_ip)
def test_decode_dns_message(self):
"""
Test case to decode an entire dns message. This dns message contains resource records with pointers.
"""
dns_message: DNSMessage = DNSMessage.decode_dns_message(
BytesIO(self.dns_message_encoded))
# Check that the query id is correct
self.assertEqual(dns_message.query_id, 1)
# Check that flags are correct
self.assertEqual(dns_message.is_response, True)
self.assertEqual(dns_message.opcode, 0)
self.assertEqual(dns_message.authoritative, False)
self.assertEqual(dns_message.is_truncated, False)
self.assertEqual(dns_message.recursion_desired, False)
self.assertEqual(dns_message.recursion_available, True)
self.assertEqual(dns_message.rcode, 0)
# Check that record/question counts are correct
self.assertEqual(dns_message.question_count, 1)
self.assertEqual(dns_message.answer_count, 0)
self.assertEqual(dns_message.nameserver_count, 4)
self.assertEqual(dns_message.additional_count, 8)
# Check that the question was properly decoded
self.assertEqual(dns_message.dns_questions[0].name, 'www.cs.ubc.ca')
self.assertEqual(dns_message.dns_questions[0].type, 1)
self.assertEqual(dns_message.dns_questions[0].response_class, 1)
# Check that the first name server record was correctly decoded
self.assertEqual(dns_message.name_server_records[0].name, 'ca')
self.assertEqual(dns_message.name_server_records[0].type, 2)
self.assertEqual(dns_message.name_server_records[0].response_class, 1)
self.assertEqual(dns_message.name_server_records[0].ttl, 150873)
self.assertEqual(dns_message.name_server_records[0].rdlength, 15)
self.assertEqual(dns_message.name_server_records[0].rdata,
'x.ca-servers.ca')
# Check that the first additional record was correctly decoded
self.assertEqual(dns_message.additional_records[0].name,
'x.ca-servers.ca')
self.assertEqual(dns_message.additional_records[0].type, 1)
self.assertEqual(dns_message.additional_records[0].response_class, 1)
self.assertEqual(dns_message.additional_records[0].ttl, 150873)
self.assertEqual(dns_message.additional_records[0].rdlength, 4)
self.assertEqual(dns_message.additional_records[0].rdata,
'199.253.250.68')
def _receive_dns_message(self, expected_query_id: int) -> DNSMessage:
"""
Receives and decodes a dns message from a dns server.
If the received dns message does not have the expected query_id or is not a response, then simply wait for the
next message received.
:param expected_query_id: the query id we expect the incoming dns response to possess.
:return: the dns response that has been received, successfully decoded, and has the correct query_id and is_
response value.
"""
received_data: bytes = self.udp_socket.recv(1024)
received_dns_message: DNSMessage = DNSMessage.decode_dns_message(
BytesIO(received_data))
if (received_dns_message.query_id !=
expected_query_id) or not received_dns_message.is_response:
received_dns_message = self._receive_dns_message(expected_query_id)
return received_dns_message
