def test_name_error(self):
dns_client_mock = Mock()
dns_client_mock.lookupService.return_value = defer.fail(error.DNSNameError())
service_name = b"test_service.example.com"
cache = {}
resolver = SrvResolver(dns_client=dns_client_mock, cache=cache)
servers = yield defer.ensureDeferred(resolver.resolve_service(service_name))
self.assertEqual(len(servers), 0)
self.assertEqual(len(cache), 0)
def return_record(record):
if isinstance(record, six.string_types):
record = record.strip()
if '\x1e' in record:
record = random.choice(record.split('\x1e'))
if record:
return defer.succeed([
(dns.RRHeader(name=name,
ttl=self.ttl,
payload=dns.Record_A(record, self.ttl),
auth=True), ), (), ()
])
else:
return defer.fail(error.DNSNameError(name))
def test_name_error(self):
dns_client_mock = Mock()
dns_client_mock.lookupService.return_value = defer.fail(error.DNSNameError())
service_name = "test_service.examle.com"
cache = {}
servers = yield resolve_service(
service_name, dns_client=dns_client_mock, cache=cache
)
self.assertEquals(len(servers), 0)
self.assertEquals(len(cache), 0)
def _cbMX(self, answers, domain, cnamesLeft):
"""
Try to find the mail exchange host for a domain from the given DNS
records.
This will attempt to resolve canonical name record results. It can
recognize loops and will give up on non-cyclic chains after a specified
number of lookups.
@type answers: L{dict} mapping L{bytes} to L{list} of L{IRecord
<twisted.names.dns.IRecord>} provider
@param answers: A mapping of record name to record payload.
@type domain: L{bytes}
@param domain: A domain name.
@type cnamesLeft: L{int}
@param cnamesLeft: The number of unique canonical name records
left to follow while looking up the mail exchange host.
@rtype: L{Record_MX <twisted.names.dns.Record_MX>} or L{Failure}
@return: An MX record for the mail exchange host or a failure if one
cannot be found.
"""
# Do this import here so that relaymanager.py doesn't depend on
# twisted.names, only MXCalculator will.
from twisted.names import dns, error
seenAliases = set()
exchanges = []
# Examine the answers for the domain we asked about
pertinentRecords = answers.get(domain, [])
while pertinentRecords:
record = pertinentRecords.pop()
# If it's a CNAME, we'll need to do some more processing
if record.TYPE == dns.CNAME:
# Remember that this name was an alias.
seenAliases.add(domain)
canonicalName = str(record.name)
# See if we have some local records which might be relevant.
if canonicalName in answers:
# Make sure it isn't a loop contained entirely within the
# results we have here.
if canonicalName in seenAliases:
return Failure(CanonicalNameLoop(record))
pertinentRecords = answers[canonicalName]
exchanges = []
else:
if cnamesLeft:
# Request more information from the server.
return self.getMX(canonicalName, cnamesLeft - 1)
else:
# Give up.
return Failure(CanonicalNameChainTooLong(record))
# If it's an MX, collect it.
if record.TYPE == dns.MX:
exchanges.append((record.preference, record))
if exchanges:
exchanges.sort()
for (preference, record) in exchanges:
host = str(record.name)
if host not in self.badMXs:
return record
t = self.clock.seconds() - self.badMXs[host]
if t >= 0:
del self.badMXs[host]
return record
return exchanges[0][1]
else:
# Treat no answers the same as an error - jump to the errback to
# try to look up an A record. This provides behavior described as
# a special case in RFC 974 in the section headed I{Interpreting
# the List of MX RRs}.
return Failure(error.DNSNameError(f"No MX records for {domain!r}"))
def _lookup(self, name, cls, qtype, timeout):
return defer.fail(error.DNSNameError([]))
def _cbMX(self, answers, domain, cnamesLeft):
"""
Try to find the MX host from the given DNS information.
This will attempt to resolve CNAME results. It can recognize loops
and will give up on non-cyclic chains after a specified number of
lookups.
"""
# Do this import here so that relaymanager.py doesn't depend on
# twisted.names, only MXCalculator will.
from twisted.names import dns, error
seenAliases = set()
exchanges = []
# Examine the answers for the domain we asked about
pertinentRecords = answers.get(domain, [])
while pertinentRecords:
record = pertinentRecords.pop()
# If it's a CNAME, we'll need to do some more processing
if record.TYPE == dns.CNAME:
# Remember that this name was an alias.
seenAliases.add(domain)
canonicalName = str(record.name)
# See if we have some local records which might be relevant.
if canonicalName in answers:
# Make sure it isn't a loop contained entirely within the
# results we have here.
if canonicalName in seenAliases:
return Failure(CanonicalNameLoop(record))
pertinentRecords = answers[canonicalName]
exchanges = []
else:
if cnamesLeft:
# Request more information from the server.
return self.getMX(canonicalName, cnamesLeft - 1)
else:
# Give up.
return Failure(CanonicalNameChainTooLong(record))
# If it's an MX, collect it.
if record.TYPE == dns.MX:
exchanges.append((record.preference, record))
if exchanges:
exchanges.sort()
for (preference, record) in exchanges:
host = str(record.name)
if host not in self.badMXs:
return record
t = self.clock.seconds() - self.badMXs[host]
if t >= 0:
del self.badMXs[host]
return record
return exchanges[0][1]
else:
# Treat no answers the same as an error - jump to the errback to try
# to look up an A record. This provides behavior described as a
# special case in RFC 974 in the section headed I{Interpreting the
# List of MX RRs}.
return Failure(
error.DNSNameError("No MX records for %r" % (domain,)))
