mac_addr should have its own type, instead of String

[mllken]

Hi,

Currently, NetworkInterface's mac_addr member is a Option<String>. It would be nice to have a simple MacAddr type, like:

pub struct MacAddr([u8; 6]);

with a From<[u8; 6]> impl and an octets method that returns [u8; 6].

Since mac_addr currently uses a String, it's unclear if it's uppercase, lowercase, in xx:xx:xx:xx:xx:xx format, or in xx-xx-xx-xx-xx-xx format. This will make comparisons easier. I can attempt a pull request if you agree with the idea. Thanks

[EstebanBorai]

Hi @mllken! Thanks for opening this issue!

Yeah I agree, I think we could have a dedicated type which also allow us to work with MAC addresses with ease.
Would you like to work on this? As a first iteration I think we could:

1. Introduce a type MacAddr just as the one you shared in your comment: MacAddr([u8; 6]).
2. Replace instances of Option<String> with Option<MacAddr>
3. Make sure we can serialize it into its string representation

I think now its a good time to introduce such a change due to the improvement suggested on #37, a single major release could introduce both changes!

[mllken]

Looking into this. It seems winapi defines PhysicalAddress as [u8; 8] (8, instead of 6). The current linux code in your crate can also handle mac addresses of any size. The proposed type might be too restrictive to support all your currently supported platforms.

[EstebanBorai]

Looking into this. It seems winapi defines PhysicalAddress as [u8; 8] (8, instead of 6). The current linux code in your crate can also handle mac addresses of any size. The proposed type might be too restrictive to support all your currently supported platforms.

Yeah theres two main schemes for Mac Addresses, one being the EUI-48 and the second is the EUI-64 scheme.

Theres more details in this RFC document: https://www.rfc-editor.org/rfc/rfc7042#page-6

I think we could have an approach to support both scenarios using an approach similar to std's for IpAddr and have an enum like:

enum MacAddress {
    Eui48(Eui48),
    Eui64(Eui64),
}

I think we could construct at the moment of parsing the Mac Address bytes in question.

WDYT?