Async dns error (#2237)

* Fix #2231: raise OSError if DNS lookup found no hosts

* Add tests

* Add changes

aiohttp/resolver.py

@@ -60,38 +60,52 @@ def __init__(self, loop=None, *args, **kwargs):
 
         if not hasattr(self._resolver, 'gethostbyname'):
             # aiodns 1.1 is not available, fallback to DNSResolver.query
-            self.resolve = self.resolve_with_query
+            self.resolve = self._resolve_with_query
 
     @asyncio.coroutine
     def resolve(self, host, port=0, family=socket.AF_INET):
+        try:
+            resp = yield from self._resolver.gethostbyname(host, family)
+        except aiodns.error.DNSError as exc:
+            msg = exc.args[1] if len(exc.args) >= 1 else "DNS lookup failed"
+            raise OSError(msg) from exc
         hosts = []
-        resp = yield from self._resolver.gethostbyname(host, family)
-
         for address in resp.addresses:
             hosts.append(
                 {'hostname': host,
                  'host': address, 'port': port,
                  'family': family, 'proto': 0,
                  'flags': socket.AI_NUMERICHOST})
+
+        if not hosts:
+            raise OSError("DNS lookup failed")
+
         return hosts
 
     @asyncio.coroutine
-    def resolve_with_query(self, host, port=0, family=socket.AF_INET):
+    def _resolve_with_query(self, host, port=0, family=socket.AF_INET):
         if family == socket.AF_INET6:
             qtype = 'AAAA'
         else:
             qtype = 'A'
 
-        hosts = []
-        resp = yield from self._resolver.query(host, qtype)
+        try:
+            resp = yield from self._resolver.query(host, qtype)
+        except aiodns.error.DNSError as exc:
+            msg = exc.args[1] if len(exc.args) >= 1 else "DNS lookup failed"
+            raise OSError(msg) from exc
 
+        hosts = []
         for rr in resp:
             hosts.append(
                 {'hostname': host,
                  'host': rr.host, 'port': port,
                  'family': family, 'proto': 0,
                  'flags': socket.AI_NUMERICHOST})
 
+        if not hosts:
+            raise OSError("DNS lookup failed")
+
         return hosts
 
     @asyncio.coroutine

changes/2231.bugfix

@@ -0,0 +1,2 @@
+Raise OSError on async DNS lookup if resolved domain is an alias for
+another one, which does not have an A or CNAME record.

tests/test_resolver.py

@@ -103,7 +103,7 @@ def test_async_resolver_negative_lookup(loop):
     with patch('aiodns.DNSResolver') as mock:
         mock().gethostbyname.side_effect = aiodns.error.DNSError()
         resolver = AsyncResolver(loop=loop)
-        with pytest.raises(aiodns.error.DNSError):
+        with pytest.raises(OSError):
             yield from resolver.resolve('doesnotexist.bla')
 
 
@@ -114,7 +114,28 @@ def test_async_resolver_query_negative_lookup(loop):
         del mock().gethostbyname
         mock().query.side_effect = aiodns.error.DNSError()
         resolver = AsyncResolver(loop=loop)
-        with pytest.raises(aiodns.error.DNSError):
+        with pytest.raises(OSError):
+            yield from resolver.resolve('doesnotexist.bla')
+
+
+@pytest.mark.skipif(aiodns is None, reason="aiodns required")
+@asyncio.coroutine
+def test_async_resolver_no_hosts_in_query(loop):
+    with patch('aiodns.DNSResolver') as mock:
+        del mock().gethostbyname
+        mock().query.return_value = fake_query_result([])
+        resolver = AsyncResolver(loop=loop)
+        with pytest.raises(OSError):
+            yield from resolver.resolve('doesnotexist.bla')
+
+
+@pytest.mark.skipif(not gethostbyname, reason="aiodns 1.1 required")
+@asyncio.coroutine
+def test_async_resolver_no_hosts_in_gethostbyname(loop):
+    with patch('aiodns.DNSResolver') as mock:
+        mock().gethostbyname.return_value = fake_result([])
+        resolver = AsyncResolver(loop=loop)
+        with pytest.raises(OSError):
             yield from resolver.resolve('doesnotexist.bla')