1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105

use libc::ioctl;
use std::error::Error;
use std::fmt;
use std::fmt::Debug;
use nix::fcntl::OFlag;
use nix::{fcntl};
use nix::errno::Errno;
use nix::sys::stat::Mode;
use nix::unistd::close;

const VT_ACTIVATE: u64 = 0x5606;
const VT_WAITACTIVE: u64 = 0x5607;
const KDGKBTYPE: u64 = 0x4B33;
const KB_101: u8 = 0x02;
const KB_84: u8 = 0x01;

#[derive(Debug)]
pub enum ErrorKind {
    ActivateError(i32),
    WaitActiveError(i32),
    CloseError,
    OpenConsoleError,
    NotAConsoleError,
    GetFDError,
}
impl Error for ErrorKind {}
impl fmt::Display for ErrorKind {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        <dyn Debug>::fmt(self, f)
    }
}

fn is_a_console(fd: i32) -> bool {
    unsafe {
        let mut arg = 0;
        ioctl(fd, KDGKBTYPE, &mut arg) == 0 && ((arg == KB_101) || (arg == KB_84))
    }
}

fn open_a_console(filename: &str) -> Result<i32, ErrorKind> {
    for oflag in &[OFlag::O_RDWR, OFlag::O_RDONLY, OFlag::O_WRONLY] {
        match fcntl::open(filename, *oflag, Mode::empty()) {
            Ok(fd) => {
                if !is_a_console(fd) {
                    close(fd).map_err(|_| ErrorKind::CloseError)?;
                    return Err(ErrorKind::NotAConsoleError);
                }

                return Ok(fd)
            },
            Err(error) => match error.as_errno() {
                Some(errno) => match errno {
                    Errno::EACCES => continue,
                    _ => break
                }
                _ => break
            }
        }
    }

    Err(ErrorKind::OpenConsoleError)
}

fn get_fd() -> Result<i32, ErrorKind> {

    if let Ok(fd) = open_a_console("/dev/tty") { return Ok(fd) }

    if let Ok(fd) = open_a_console("/dev/tty") { return Ok(fd) }

    if let Ok(fd) = open_a_console("/dev/tty0") { return Ok(fd) }

    if let Ok(fd) = open_a_console("/dev/vc/0") { return Ok(fd) }

    if let Ok(fd) = open_a_console("/dev/console") { return Ok(fd) }

    for fd in 0..3 {
        if is_a_console(fd) {
            return Ok(fd);
        }
    }

    // If all attempts fail Error
    Err(ErrorKind::GetFDError)
}

pub fn chvt(ttynum: i32) -> Result<(), ErrorKind> {

    let fd = get_fd()?;

    unsafe {
        let activate = ioctl(fd, VT_ACTIVATE, ttynum);

        if activate > 0 {
            return Err(ErrorKind::ActivateError(activate));
        }
        let wait = ioctl(fd, VT_WAITACTIVE, ttynum);
        if wait > 0 {
            return Err(ErrorKind::WaitActiveError(wait));
        }
    }

    close(fd).map_err(|_| ErrorKind::CloseError)?;

    Ok(())
}