create_datagram_endpoint does not work with IPv6

[chrysn]

• uvloop version: 0.8.1
• Python version: 3.5.4rc1
• Platform: Debian GNU/Linux
• Can you reproduce the bug with PYTHONASYNCIODEBUG in env?: yes

While the default asyncio main loop can easily accept both IPv4 and IPv6 addresses n create_datagram_endpoint(remote_addr=...), uvloop accepts IPv4 address only.

The attached example shows this; call it ./echo.py 0 127.0.0.1 and ./echo.py 0 ::1 to use asyncio's main loop and try to reach localhost:9999 (usually gives you "Connection refused" errors for both). Running it as ./echo 1 127.0.0.1 sends the datagram using uvloop (it doesn't show an error, but that's probably a different bug), and running it as ./echo 1 ::1 tries IPv6 on uvloop, but raises a socket.gaierror: [Errno -9] Address family for hostname not supported.

The example is almost verbatim the example from the Python documentation, adapted to take arguments and start uvloop.

[chrysn]

More precisely, it does not work without further options with IPv6; setting family=AF_INET6 does make a ::1 connection work, but then again doesn't allow v4 addresses to be used without prior inspection of the address for which family to set. Passing flags=socket.AI_V4MAPPED in addition to family creates a default behavior that seems to be equivalent to asyncio's. (asyncio claims that it decides based on host's value which family it chooses; I did not verify that, and only looked at the simple test's behavior).

[1st1]

asyncio claims that it decides based on host's value which family it chooses

Alright, I'll take a look how Python/asyncio implements that.

[1st1]

BTW, feel free to submit a PR if you have a good idea how to fix this before I find time.

[1st1]

Fixed in master. Will be in the next uvloop release next week.

[1st1]

Please try uvloop v0.9.0!