Add net::hostname to retrieve the devices host name

[valaphee]

Proposal

Problem statement

There is no std-way of retrieving the devices host name.

Motivating examples or use cases

The devices host name is most commonly used as friendly name, in communication with other devices over the network or for logging purposes.

And just looking at the download count of the gethostname crate it seems to be a small but useful addition to std::net. It is also inspired by std::env which has functions to retrieve the current dir, temp dir or home dir. Every device which uses IP also has an hostname (as its also part of DHCP).

Solution sketch

The implementation would be similar to the gethostname crate gethostname method just with the signature fn std::net::hostname() -> OsString. (hostname might also be written as host_name?)

Alternatives

Using the gethostname or hostname crate

Links and related work

https://github.com/swsnr/gethostname.rs
https://github.com/svartalf/hostname

What happens now?

This issue contains an API change proposal (or ACP) and is part of the libs-api team feature lifecycle. Once this issue is filed, the libs-api team will review open proposals as capability becomes available. Current response times do not have a clear estimate, but may be up to several months.

Possible responses

The libs team may respond in various different ways. First, the team will consider the problem (this doesn't require any concrete solution or alternatives to have been proposed):

• We think this problem seems worth solving, and the standard library might be the right place to solve it.
• We think that this probably doesn't belong in the standard library.

Second, if there's a concrete solution:

• We think this specific solution looks roughly right, approved, you or someone else should implement this. (Further review will still happen on the subsequent implementation PR.)
• We're not sure this is the right solution, and the alternatives or other materials don't give us enough information to be sure about that. Here are some questions we have that aren't answered, or rough ideas about alternatives we'd want to see discussed.

[joshtriplett]

I think this should be io::Result<OsString>, for the benefit of platforms that don't have this or that can produce an error when attempting to get it.

Also, we should document whether this is expected to be a FQDN or just a bare hostname. (I would expect the latter.)

[joshtriplett]

We discussed this in today's libs-api meeting, and we agreed to accept this, with the change to use io::Result.

[orowith2os]

How's this looking? Does someone still have to add the method? I could take a look at part of it, maybe?

[orowith2os]

Never mind my previous comment - I'm already implementing it :) Expect a PR soon!