dns: hosts file was consulted after nameservers
This bug was introduced in v0.20.1 Now the behavior is as expected: first check hosts file, if it contains address - short return without querying nameservers. https://github.com/eventlet/eventlet/issues/387
This commit is contained in:
Sergey Shepelev
parent
f657c22eff
commit
503aed1310
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@ -306,6 +306,12 @@ class ResolverProxy(object):
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tcp=False, source=None, raise_on_no_answer=True,
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_hosts_rdtypes=(dns.rdatatype.A, dns.rdatatype.AAAA)):
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"""Query the resolver, using /etc/hosts if enabled.
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Behavior:
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1. if hosts is enabled and contains answer, return it now
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2. query nameservers for qname
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3. if qname did not contain dots, pretend it was top-level domain,
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query "foobar." and append to previous result
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"""
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result = [None, None, 0]
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@ -328,6 +334,21 @@ class ResolverProxy(object):
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result[2] += len(a.rrset)
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return True
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def end():
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if result[0] is not None:
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if raise_on_no_answer and result[2] == 0:
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raise dns.resolver.NoAnswer
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return result[0]
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if result[1] is not None:
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if raise_on_no_answer or not isinstance(result[1], dns.resolver.NoAnswer):
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raise result[1]
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raise dns.resolver.NXDOMAIN(qnames=(qname,))
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if (self._hosts and (rdclass == dns.rdataclass.IN) and (rdtype in _hosts_rdtypes)):
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if step(self._hosts.query, qname, rdtype, raise_on_no_answer=False):
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if (result[0] is not None) or (result[1] is not None):
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return end()
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# Main query
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step(self._resolver.query, qname, rdtype, rdclass, tcp, source, raise_on_no_answer=False)
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@ -341,20 +362,7 @@ class ResolverProxy(object):
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step(self._resolver.query, qname.concatenate(dns.name.root),
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rdtype, rdclass, tcp, source, raise_on_no_answer=False)
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# Return answers from /etc/hosts despite nameserver errors
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# https://github.com/eventlet/eventlet/pull/354
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if ((result[2] == 0) and self._hosts and
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(rdclass == dns.rdataclass.IN) and (rdtype in _hosts_rdtypes)):
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step(self._hosts.query, qname, rdtype, raise_on_no_answer=False)
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if result[0] is not None:
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if raise_on_no_answer and result[2] == 0:
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raise dns.resolver.NoAnswer
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return result[0]
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if result[1] is not None:
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if raise_on_no_answer or not isinstance(result[1], dns.resolver.NoAnswer):
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raise result[1]
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raise dns.resolver.NXDOMAIN(qnames=(qname,))
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return end()
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def getaliases(self, hostname):
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"""Return a list of all the aliases of a given hostname"""
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@ -376,8 +384,8 @@ class ResolverProxy(object):
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resolver = ResolverProxy(hosts_resolver=HostsResolver())
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def resolve(name, family=socket.AF_INET, raises=True):
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"""Resolve a name for a given family using the global resolver proxy
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def resolve(name, family=socket.AF_INET, raises=True, _proxy=None):
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"""Resolve a name for a given family using the global resolver proxy.
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This method is called by the global getaddrinfo() function.
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@ -391,9 +399,12 @@ def resolve(name, family=socket.AF_INET, raises=True):
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else:
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raise socket.gaierror(socket.EAI_FAMILY,
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'Address family not supported')
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if _proxy is None:
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_proxy = resolver
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try:
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try:
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return resolver.query(name, rdtype, raise_on_no_answer=raises)
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return _proxy.query(name, rdtype, raise_on_no_answer=raises)
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except dns.resolver.NXDOMAIN:
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if not raises:
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return HostsAnswer(dns.name.Name(name),
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@ -12,26 +12,27 @@ import tests
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import tests.mock
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def _make_host_resolver():
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"""Returns a HostResolver instance
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The hosts file will be empty but accessible as a py.path.local
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instance using the ``hosts`` attribute.
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"""
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hosts = tempfile.NamedTemporaryFile()
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hr = greendns.HostsResolver(fname=hosts.name)
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hr.hosts = hosts
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hr._last_stat = 0
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return hr
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class TestHostsResolver(tests.LimitedTestCase):
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def _make_host_resolver(self):
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"""Returns a HostResolver instance
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The hosts file will be empty but accessible as a py.path.local
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instance using the ``hosts`` attribute.
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"""
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hosts = tempfile.NamedTemporaryFile()
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hr = greendns.HostsResolver(fname=hosts.name)
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hr.hosts = hosts
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hr._last_stat = 0
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return hr
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def test_default_fname(self):
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hr = greendns.HostsResolver()
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assert os.path.exists(hr.fname)
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def test_readlines_lines(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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hr.hosts.write(b'line0\n')
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hr.hosts.flush()
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assert hr._readlines() == ['line0']
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@ -44,20 +45,20 @@ class TestHostsResolver(tests.LimitedTestCase):
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assert hr._readlines() == ['line0', 'line1']
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def test_readlines_missing_file(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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hr.hosts.close()
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hr._last_stat = 0
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assert hr._readlines() == []
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def test_load_no_contents(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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hr._load()
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assert not hr._v4
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assert not hr._v6
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assert not hr._aliases
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def test_load_v4_v6_cname_aliases(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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hr.hosts.write(b'1.2.3.4 v4.example.com v4\n'
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b'dead:beef::1 v6.example.com v6\n')
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hr.hosts.flush()
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@ -69,7 +70,7 @@ class TestHostsResolver(tests.LimitedTestCase):
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'v6': 'v6.example.com'}
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def test_load_v6_link_local(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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hr.hosts.write(b'fe80:: foo\n'
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b'fe80:dead:beef::1 bar\n')
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hr.hosts.flush()
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@ -78,14 +79,14 @@ class TestHostsResolver(tests.LimitedTestCase):
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assert not hr._v6
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def test_query_A(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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hr._v4 = {'v4.example.com': '1.2.3.4'}
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ans = hr.query('v4.example.com')
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assert ans[0].address == '1.2.3.4'
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def test_query_ans_types(self):
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# This assumes test_query_A above succeeds
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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hr._v4 = {'v4.example.com': '1.2.3.4'}
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hr._last_stat = time.time()
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ans = hr.query('v4.example.com')
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@ -108,18 +109,18 @@ class TestHostsResolver(tests.LimitedTestCase):
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assert rr.address == '1.2.3.4'
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def test_query_AAAA(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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hr._v6 = {'v6.example.com': 'dead:beef::1'}
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ans = hr.query('v6.example.com', dns.rdatatype.AAAA)
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assert ans[0].address == 'dead:beef::1'
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def test_query_unknown_raises(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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with tests.assert_raises(greendns.dns.resolver.NoAnswer):
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hr.query('example.com')
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def test_query_unknown_no_raise(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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ans = hr.query('example.com', raise_on_no_answer=False)
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assert isinstance(ans, greendns.dns.resolver.Answer)
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assert ans.response is None
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@ -134,30 +135,30 @@ class TestHostsResolver(tests.LimitedTestCase):
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assert len(ans.rrset) == 0
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def test_query_CNAME(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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hr._aliases = {'host': 'host.example.com'}
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ans = hr.query('host', dns.rdatatype.CNAME)
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assert ans[0].target == dns.name.from_text('host.example.com')
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assert str(ans[0].target) == 'host.example.com.'
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def test_query_unknown_type(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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with tests.assert_raises(greendns.dns.resolver.NoAnswer):
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hr.query('example.com', dns.rdatatype.MX)
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def test_getaliases(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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hr._aliases = {'host': 'host.example.com',
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'localhost': 'host.example.com'}
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res = set(hr.getaliases('host'))
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assert res == set(['host.example.com', 'localhost'])
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def test_getaliases_unknown(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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assert hr.getaliases('host.example.com') == []
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def test_getaliases_fqdn(self):
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hr = self._make_host_resolver()
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hr = _make_host_resolver()
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hr._aliases = {'host': 'host.example.com'}
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res = set(hr.getaliases('host.example.com'))
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assert res == set(['host'])
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@ -791,3 +792,29 @@ def test_proxy_resolve_unqualified():
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pass
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assert any(call[0][0] == dns.name.from_text('machine') for call in m.call_args_list)
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assert any(call[0][0] == dns.name.from_text('machine.') for call in m.call_args_list)
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def test_hosts_priority():
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name = 'example.com'
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addr_from_ns = '1.0.2.0'
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hr = _make_host_resolver()
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rp = greendns.ResolverProxy(hosts_resolver=hr, filename=None)
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base = _make_mock_base_resolver()
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base.rr.address = addr_from_ns
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rp._resolver = base()
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# Default behavior
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rrns = greendns.resolve(name, _proxy=rp).rrset[0]
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assert rrns.address == addr_from_ns
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# Hosts result must shadow that from nameservers
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hr.hosts.write(b'1.2.3.4 example.com\ndead:beef::1 example.com\n')
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hr.hosts.flush()
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hr._load()
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rrs4 = greendns.resolve(name, family=socket.AF_INET, _proxy=rp).rrset
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assert len(rrs4) == 1
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assert rrs4[0].address == '1.2.3.4', rrs4[0].address
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rrs6 = greendns.resolve(name, family=socket.AF_INET6, _proxy=rp).rrset
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assert len(rrs6) == 1
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assert rrs6[0].address == 'dead:beef::1', rrs6[0].address
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