All fields in ucred struct are private

[Roguelazer]

I'm using PeerCredentials functionality to extract the remote end of a unix domain socket, but all of the fields in the resulting ucred struct are private. I can work around this by doing an unsafe reinterepret cast (err, transmute) to a #struct of my own definition with the same fields and layout, but would it be reasonable to just redefine struct ucred to have public fields?

[fiveop]

The definition of ucred in nix is pretty old. We usually wrap the definition in rust-lang/libc in a new struct (here, we might name it UserCredentials) and then provide accessor functions as needed. See for example SigSet.

[icorderi]

The issue still remains, we are missing a way to access the result of SO_PEERCRED:

let cred = getsockopt(fd, PeerCredentials)?;
//  cred is all private...

Based on @fiveop comments, we would need something on the lines of:

#[derive(Clone, Copy)]
pub struct UserCredentials {
    ucred: libc::ucred
}

impl UserCredentials {
    fn group(&self) -> u32 {
        self.ucred.gid
    }
    fn user(&self) -> u32 {
        self.ucred.uid
    }
    fn pid(&self) -> u32 {
        self.ucred.pid
    }
}

@fiveop is this what you had in mind? If so, I'm happy to get going with this.

[Susurrus]

Usually this is done via newtypes, like pub struct UserCredentials(libc::ucred), so it works like a tuple. Accessing it's internal member can be done with .0.

This also brings up the question of setters. Are those necessary for this structure or is there really a read-only structure?

[icorderi]

Should be read-only, you are querying the values from the OS.
Sure, we can use a newtype instead.

[Susurrus]

@icorderi Then this design makes sense. Would you be interested in filing a PR for this?

[icorderi]

The PR is #608, let me know what other changes are needed.