Add KEEPALIVE_TIME for haiku and openbsd (compilation was broken)

[epilys]

No description provided.

[Thomasdezeeuw]

SO_KEEPALIVE is not the same as KEEPALIVE_TIME, also see #251.

[Thomasdezeeuw]

Oh. I read the manpage and it doesn't mention something like that.

KEEPALIVE_TIME is TCP_KEEPALIVE, thus on the TCP socket level, while SO_KEEPALIVE is on the more general socket level (SO).

Would returning an error be acceptable? Otherwise it won't build at all.

I'm afraid not, but we can remove the function from OpenBSD by using something like:

#[cfg(not(target_os = "openbsd"))]

on keepalive_time and set_keepalive_time.

And on sysctl(3) it mentions KEEPALIVE set on TCP sockets.

That is a boolean to enable keepalive, while KEEPALIVE_TIME sets a duration, see TCP_KEEPIDLE for Linux or TCP_KEEPALIVE for macOS.