TUN/TAP support

[SwagColoredKitteh]

It would be nice to have support for TUN/TAP devices. I guess this would involve adding a few ioctls and structs? I wouldn't mind implementing this myself, but would like some pointers for how to get started.

[posborne]

I would be open to considering adding TUN/TAP support to nix; It would definitely be good to have support for these types of devices in the Rust ecosystem.

Initially, I think it might be a better approach to consider adding the support as a separate crate outside of nix itself as it is a little bit more specific than what we typically handle. If there are specific system calls that need to be exposed safely that aren't currently exposed by nix, we would be very open to adding them.

Nix already has basic support for ioctls and, at present, we have avoided being in the business of providing a full list of ioctl definitions and safe wrappers as there are a lot of different ioctls out there and many of them are OS-specific.

I initially added the ioctl support we have in rust in order to implement libraries like i2cdev. Like TUN/TAP devices, the APIs for I2C are somewhat specific and don't really belong in nix.

[Susurrus]

It seems like this is something that should be left out of nix. @SwagColoredKitteh have you done any work implementing what you need in a separate crate or anything?

[LuoZijun]

meh/rust-tun Supoort macOS and Linux.