UDP connection fails when local_addr and remote_addr are used together

[primal100]

• uvloop version: 0.13.0
• Python version: 3.7.4
• Platform: Ubuntu
• Can you reproduce the bug with PYTHONASYNCIODEBUG in env?: Yes

The following code, using local_addr and remote_addr together:

import asyncio
try:
    import uvloop
    uvloop.install()
except ImportError:
    uvloop = None


server_addr = ('127.0.0.1', 8888)
client_addr = ('127.0.0.1', 0)


async def run():
    print(asyncio.get_event_loop())
    server_transport, client_protocol = await asyncio.get_event_loop().create_datagram_endpoint(asyncio.DatagramProtocol,
                                                                              local_addr=server_addr)
    print('SERVER RUNNING')
    client_transport, client_conn = await asyncio.get_event_loop().create_datagram_endpoint(asyncio.DatagramProtocol,
                                                                              remote_addr=server_addr,
                                                                              local_addr=client_addr)
    client_transport.close()
    print('CLIENT DONE')
    server_transport.close()
    print('SERVER STOPPED')

if __name__ == '__main__':
    asyncio.run(run())

produces the following error:

<uvloop.Loop running=True closed=False debug=False>
Traceback (most recent call last):
  File "scratch_144.py", line 35, in <module>
    asyncio.run(run())
  File "/usr/lib/python3.7/asyncio/runners.py", line 43, in run
    return loop.run_until_complete(main)
  File "uvloop/loop.pyx", line 1417, in uvloop.loop.Loop.run_until_complete
  File "scratch_144.py", line 29, in run
    await run_client()
  File "scratch_144.py", line 20, in run_client
    transport, conn = await asyncio.get_event_loop().create_datagram_endpoint(asyncio.DatagramProtocol, remote_addr=server_addr, local_addr=client_addr)
  File "uvloop/loop.pyx", line 2980, in create_datagram_endpoint
  File "uvloop/handles/udp.pyx", line 86, in uvloop.loop.UDPTransport._connect
OSError: [Errno 106] Transport endpoint is already connected

If I remove the local_addr argument from the second create_datagram_endpoint, it works.
The above example works ok in Selector and Proactor.

[jlaine]

The code in create_datagram_endpoint indeed looks suspicious, there are two calls to _connect:

uvloop/uvloop/loop.pyx

Line 2973 in 82104fb

udp._connect(rai.ai_addr, rai.ai_addrlen)

uvloop/uvloop/loop.pyx

Line 2980 in 82104fb

udp._connect(rai.ai_addr, rai.ai_addrlen)

[1st1]

Yeah, weird. Probably was a remnant of the old UDP implementation surfaced because of the three-way merge I had to do.

[1st1]

I've just published https://github.com/MagicStack/uvloop/releases/tag/v0.14.0rc1. Please test. The final release will be published some time next week if RC1 is OK.