Could not determine IPv4/IPv6 protocol. Using AF_INET

[Antonio Quartulli]

Every time I run OpenVPN server on linux I get the message "Could not determine IPv4/IPv6 protocol. Using AF_INET" in the log. The message was introduced by commit 45184804c477aed2ae91ce23d6606da1bfccbaa7 ("Fix for server selecting address family").

Bisecting this issue was not needed, because the message is printed since its introduction.

I couldn't find any runtime problem after reading this message. However, I am not sure what happens if I set the server to listen on IPv6.

[Antonio Quartulli]

When listening on an IPv6 socket (by means of "proto udp6") no warning is printed and IPv6 clients can properly connect.

[Antonio Quartulli]

After digging deeper and deeper and after discussing with cron2 on IRC, the conclusion is that this message is printed when no IPv4/v6 preference is given in the config (i.e. proto udp/tcp is used) and OpenVPN is running as a server. In this case OpenVPN falls back on what the OS prefers (based on getaddrinfo() result) - in my case AF_INET - and the message is printed to show the decision.

When using udp4/udp6 (or tcp4/tcp6) no message is printed because the socket family to use has been provided by the user.

I think this ticket can be classified as noise and closed :)

[Gert Döring]

Oh, indeed. *Now* I understand that "error" message, finally :-) - I knew what was happening behind the scenes, but it did not "click" yet.

Now it did - it's informational, and we inform the user what the outcome of "ask getaddrinfo() what we'll get?" was.

But it's useful to have in here in case someone else is searching for it.