fix wrong xattr syscalls on NetBSD

[SteveLauC]

I am not 100% sure that these bindings are wrong because I can not find them in the NetBSD manual.

But according to sys/sys/xattr.h, they seems to be wrong:

int	setxattr(const char *, const char *, const void *, size_t, int);
int	lsetxattr(const char *, const char *, const void *, size_t, int);

int	fremovexattr(int, const char *);

// Current bindings in `libc`:

pub fn setxattr(
    path: *const ::c_char,
    name: *const ::c_char,
    value: *const ::c_void,
    size: ::size_t,
) -> ::c_int;
pub fn lsetxattr(
    path: *const ::c_char,
    name: *const ::c_char,
    value: *const ::c_void,
    size: ::size_t,
) -> ::c_int;
pub fn fremovexattr(
    fd: ::c_int, 
    path: *const ::c_char, 
    name: *const ::c_char
) -> ::c_int;

Friendly ping @devnexen who originally added them in #2514 .

[rust-highfive]

r? @JohnTitor

(rust-highfive has picked a reviewer for you, use r? to override)

[JohnTitor]

I think this is a breaking change as it changes the interface. I'm, however, fine to accept it as long as they aren't usable at all across all NetBSD versions (that makes it possible to assume there's no real user). Could you make sure of that?

[SteveLauC]

Yes, this is a breaking change. I will try to fire up a NetBSD VM to test the current APIs.

[SteveLauC]

Hi, guys, I just have NetBSD installed (including Rust toolchain and the GCC compiler), so I am ready to test the existing bindings.

But I may need some help on how to test them.

What values should be passed for those function parameters that do not exist? (the path argument in removexattr) For parameters that are not exposed, should we just ignore them (flag argument of setxattr and lsetxattr)?

Friendly ping @JohnTitor

---

UPDATE: I just found that the extended attribute is not enabled by default on NetBSD.

#include <sys/xattr.h>
#include <stdio.h>   
#include <errno.h>
 
int main(int ac, char *av[]) {
        int res = setxattr("/home/steve/workspace/c/file", "user.first_ea", "first_ea", 8, 0);
 
 
        if (res == -1) {
                printf("errno = %d\n", errno);
                perror(NULL);
        } else {
                printf("success");
        }
        return 0;
}

$ gcc main.c && ./a.out
errno = 86
Not supported

So now I need to find a way to enable it...

[SteveLauC]

Though EA is not enabled, I still tested the following code snippet:

use libc::{__errno, c_char, c_void, lsetxattr, perror, fremovexattr, setxattr};
use std::{        
    ptr::null_mut,
    os::unix::io::AsRawFd,     
    fs::File,                                  
};       
            
fn test_setxattr() {        
    println!("Testing setxattr:");
    let res = unsafe {
        setxattr(
            "/home/steve/workspace/rust/Cargo.toml\0".as_ptr() as *mut c_char,
            "user.first\0".as_ptr() as *mut c_char,
            "first\0".as_ptr() as *mut c_void,
            5,                                                              
        )                     
    };               
                                                                                          
    if res == -1 {
        unsafe {
            perror(null_mut());
            println!("errno = {}", *__errno());
        }                      
    } else {                                   
        println!("success");
    }       
    println!();             
}    
               
 
fn test_lsetxattr() {
    println!("Testing lsetxattr:");
    let res = unsafe {
        lsetxattr(   
            "/home/steve/workspace/rust/Cargo.toml\0".as_ptr() as *mut c_char,
            "user.first\0".as_ptr() as *mut c_char,
            "user.first\0".as_ptr() as *mut c_char,
            "first\0".as_ptr() as *mut c_void,
            5,
        )
    };

    if res == -1 {
        unsafe {
            perror(null_mut());
            println!("errno = {}", *__errno());
        }
    } else {
        println!("success");
    }
    println!();
}

fn test_fremovexattr() {
    println!("Testing fremovexattr:");
    let file = File::open("/home/steve/workspace/rust/Cargo.toml").unwrap();
    let fd = file.as_raw_fd();
    let res = unsafe{
        fremovexattr(fd, "user.fist\0".as_ptr() as *mut c_char, null_mut() as *mut c_char)
    };
    if res == -1 {
        unsafe {
            perror(null_mut());
            println!("errno = {}", *__errno());
        }
    } else {
        println!("success");
    }
    println!();
}

fn main() {
    test_setxattr();
    test_lsetxattr();
    test_fremovexattr();
}

$ cargo r -q
Testing setxattr:
Not supported
errno = 86

Testing lsetxattr:
Not supported
errno = 86

Testing fremovexattr:
Not supported
errno = 86

The existing bindings seemed to work, at least they showed me that EA is not supported.

[SteveLauC]

NetBSD 10 will be the first official release with full extended attribute support in FFS

If we would like to test these bindings further, we have to wait for the NetBSD 10 release