only use AI_ADDRCONFIG when supported by getaddrinfo (#10542)

The fallback implementation for getaddrinfo in CPython doesn't support
`AI_ADDRCONFIG` and currently fails with a bad flags error. This changes
the implementation to only set the flag if it's part of `AI_MASK`. Since
`AI_MASK` isn't necessarily available either this has to be checked
first.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: J. Nick Koston <[email protected]>

Author: 3 people

CHANGES/10542.bugfix

@@ -0,0 +1 @@
+Fixed DNS resolution on platforms that don't support ``socket.AI_ADDRCONFIG`` -- by :user:`maxbachmann`.

aiohttp/resolver.py

@@ -18,6 +18,9 @@
 
 _NUMERIC_SOCKET_FLAGS = socket.AI_NUMERICHOST | socket.AI_NUMERICSERV
 _NAME_SOCKET_FLAGS = socket.NI_NUMERICHOST | socket.NI_NUMERICSERV
+_AI_ADDRCONFIG = socket.AI_ADDRCONFIG
+if hasattr(socket, "AI_MASK"):
+    _AI_ADDRCONFIG &= socket.AI_MASK
 
 
 class ThreadedResolver(AbstractResolver):
@@ -38,7 +41,7 @@ async def resolve(
             port,
             type=socket.SOCK_STREAM,
             family=family,
-            flags=socket.AI_ADDRCONFIG,
+            flags=_AI_ADDRCONFIG,
         )
 
         hosts: List[ResolveResult] = []
@@ -96,7 +99,7 @@ async def resolve(
                 port=port,
                 type=socket.SOCK_STREAM,
                 family=family,
-                flags=socket.AI_ADDRCONFIG,
+                flags=_AI_ADDRCONFIG,
             )
         except aiodns.error.DNSError as exc:
             msg = exc.args[1] if len(exc.args) >= 1 else "DNS lookup failed"