Wrong answer for DNS queries after an internet outage

[mberdyshev]

My application works in a Windows environment where internet dropouts may happen. If the app makes a DNS query at such a moment, it can't get the answer even when the connection has been re-established.
Let's look at an example - I've taken the code from the repository __main__.py file and have changed only two last lines to make a cycle:

while True:
    channel.query(hostname, query_type, cb)
    wait_channel(channel)
    time.sleep(1)

For imitations of a network outage, I apply the following command (Windows):

netsh wlan add filter permission=block ssid="<Wi-Fi ssid>" networktype=infrastructure

After running the changed __main__.py I get: Error: (11) Could not contact DNS servers. Even after the network establishment (or filter removal via netsh wlan delete filter <...>) during the working script, I still receive the same error message with no successful answer. Only a full script re-run helps in this situation.

I'm not sure whether this issue lies inside c-ares or not, as I wasn't able to make it run on Windows, but presumably you may know better.

[saghul]

I honestly have no idea 😅

[mberdyshev]

Could you take the time to investigate the problem?

[saghul]

I don't have time, now, sorry. The solution proposed in aio-libs/aiodns#124 is correct though, so adding the extra required API to pycares is acceptable. Feel free to send a PR, or I'll get to it when I have time.