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Use AF_UNSPEC for name resolution #389

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merged 2 commits into from
Apr 8, 2022
Merged

Use AF_UNSPEC for name resolution #389

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1465a70
Use AF_UNSPEC for name resolution
jeckersb Mar 23, 2022
2b2f2a8
tests: ensure getaddrinfo is called with AF_UNSPEC
jeckersb Mar 24, 2022
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70 changes: 19 additions & 51 deletions amqp/transport.py
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Original file line number Diff line number Diff line change
Expand Up @@ -169,59 +169,27 @@ def having_timeout(self, timeout):
sock.settimeout(prev)

def _connect(self, host, port, timeout):
e = None

# Below we are trying to avoid additional DNS requests for AAAA if A
# succeeds. This helps a lot in case when a hostname has an IPv4 entry
# in /etc/hosts but not IPv6. Without the (arguably somewhat twisted)
# logic below, getaddrinfo would attempt to resolve the hostname for
# both IP versions, which would make the resolver talk to configured
# DNS servers. If those servers are for some reason not available
# during resolution attempt (either because of system misconfiguration,
# or network connectivity problem), resolution process locks the
# _connect call for extended time.
addr_types = (socket.AF_INET, socket.AF_INET6)
addr_types_num = len(addr_types)
for n, family in enumerate(addr_types):
# first, resolve the address for a single address family
entries = socket.getaddrinfo(
host, port, socket.AF_UNSPEC, socket.SOCK_STREAM, SOL_TCP,
)
for i, res in enumerate(entries):
af, socktype, proto, canonname, sa = res
try:
entries = socket.getaddrinfo(
host, port, family, socket.SOCK_STREAM, SOL_TCP)
entries_num = len(entries)
except socket.gaierror:
# we may have depleted all our options
if n + 1 >= addr_types_num:
# if getaddrinfo succeeded before for another address
# family, reraise the previous socket.error since it's more
# relevant to users
raise (e
if e is not None
else socket.error(
"failed to resolve broker hostname"))
continue # pragma: no cover

# now that we have address(es) for the hostname, connect to broker
for i, res in enumerate(entries):
af, socktype, proto, _, sa = res
self.sock = socket.socket(af, socktype, proto)
try:
self.sock = socket.socket(af, socktype, proto)
try:
set_cloexec(self.sock, True)
except NotImplementedError:
pass
self.sock.settimeout(timeout)
self.sock.connect(sa)
except OSError as ex:
e = ex
if self.sock is not None:
self.sock.close()
self.sock = None
# we may have depleted all our options
if i + 1 >= entries_num and n + 1 >= addr_types_num:
raise
else:
# hurray, we established connection
return
set_cloexec(self.sock, True)
except NotImplementedError:
pass
self.sock.settimeout(timeout)
self.sock.connect(sa)
except socket.error:
if self.sock:
self.sock.close()
self.sock = None
if i + 1 >= len(entries):
raise
else:
break

def _init_socket(self, socket_settings, read_timeout, write_timeout):
self.sock.settimeout(None) # set socket back to blocking mode
Expand Down
40 changes: 3 additions & 37 deletions t/unit/test_transport.py
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Original file line number Diff line number Diff line change
Expand Up @@ -520,54 +520,20 @@ def test_connect_multiple_addr_entries_succeed(self):
side_effect=(socket.error, None)):
self.t.connect()

def test_connect_short_curcuit_on_INET_succeed(self):
def test_connect_calls_getaddrinfo_with_af_unspec(self):
with patch('socket.socket', return_value=MockSocket()), \
patch('socket.getaddrinfo',
side_effect=[
[(socket.AF_INET, 1, socket.IPPROTO_TCP,
'', ('127.0.0.1', 5672))],
[(socket.AF_INET6, 1, socket.IPPROTO_TCP,
'', ('::1', 5672))]
]) as getaddrinfo:
patch('socket.getaddrinfo') as getaddrinfo:
self.t.sock = Mock()
self.t.close()
self.t.connect()
getaddrinfo.assert_called_with(
'localhost', 5672, socket.AF_INET, ANY, ANY)

def test_connect_short_curcuit_on_INET_fails(self):
with patch('socket.socket', return_value=MockSocket()) as sock_mock, \
patch('socket.getaddrinfo',
side_effect=[
[(socket.AF_INET, 1, socket.IPPROTO_TCP,
'', ('127.0.0.1', 5672))],
[(socket.AF_INET6, 1, socket.IPPROTO_TCP,
'', ('::1', 5672))]
]) as getaddrinfo:
self.t.sock = Mock()
self.t.close()
with patch.object(sock_mock.return_value, 'connect',
side_effect=(socket.error, None)):
self.t.connect()
getaddrinfo.assert_has_calls(
[call('localhost', 5672, addr_type, ANY, ANY)
for addr_type in (socket.AF_INET, socket.AF_INET6)])
'localhost', 5672, socket.AF_UNSPEC, ANY, ANY)

def test_connect_getaddrinfo_raises_gaierror(self):
with patch('socket.getaddrinfo', side_effect=socket.gaierror):
with pytest.raises(socket.error):
self.t.connect()

def test_connect_getaddrinfo_raises_gaierror_once_recovers(self):
with patch('socket.socket', return_value=MockSocket()), \
patch('socket.getaddrinfo',
side_effect=[
socket.gaierror,
[(socket.AF_INET6, 1, socket.IPPROTO_TCP,
'', ('::1', 5672))]
]):
self.t.connect()

def test_connect_survives_not_implemented_set_cloexec(self):
with patch('socket.socket', return_value=MockSocket()), \
patch('socket.getaddrinfo',
Expand Down