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use std::ffi::CString;
use std::io;
use std::os::fd::{AsRawFd, FromRawFd, OwnedFd};
use tokio::io::Interest;
use tokio::io::unix::AsyncFd;
pub const TUN_CLONE_DEVICE: &str = "/dev/net/tun";
pub struct Tun {
fd: AsyncFd<OwnedFd>,
name: String,
}
impl Tun {
pub fn create(name: &str) -> io::Result<Tun> {
if name.is_empty() || name.len() >= libc::IFNAMSIZ {
return Err(io::Error::new(
io::ErrorKind::InvalidInput,
format!("tun name {name:?} must be 1..{} bytes", libc::IFNAMSIZ - 1),
));
}
let path = CString::new(TUN_CLONE_DEVICE).map_err(io::Error::other)?;
let raw = unsafe {
libc::open(
path.as_ptr(),
libc::O_RDWR | libc::O_NONBLOCK | libc::O_CLOEXEC,
)
};
if raw < 0 {
return Err(io::Error::last_os_error());
}
let owned = unsafe { OwnedFd::from_raw_fd(raw) };
let mut request: libc::ifreq = unsafe { std::mem::zeroed() };
for (slot, byte) in request.ifr_name.iter_mut().zip(name.as_bytes()) {
*slot = *byte as libc::c_char;
}
request.ifr_ifru.ifru_flags = (libc::IFF_TUN | libc::IFF_NO_PI) as libc::c_short;
let rc = unsafe { libc::ioctl(owned.as_raw_fd(), libc::TUNSETIFF, &mut request) };
if rc < 0 {
return Err(io::Error::last_os_error());
}
let assigned: Vec<u8> = request
.ifr_name
.iter()
.take_while(|c| **c != 0)
.map(|c| *c as u8)
.collect();
Ok(Tun {
fd: AsyncFd::new(owned)?,
name: String::from_utf8_lossy(&assigned).into_owned(),
})
}
pub fn name(&self) -> &str {
&self.name
}
pub fn index(&self) -> io::Result<u32> {
let name = CString::new(self.name.as_str()).map_err(io::Error::other)?;
let index = unsafe { libc::if_nametoindex(name.as_ptr()) };
if index == 0 {
return Err(io::Error::last_os_error());
}
Ok(index)
}
pub async fn recv(&self, buf: &mut [u8]) -> io::Result<usize> {
self.fd
.async_io(Interest::READABLE, |fd| {
let n = unsafe { libc::read(fd.as_raw_fd(), buf.as_mut_ptr().cast(), buf.len()) };
if n < 0 {
Err(io::Error::last_os_error())
} else {
Ok(n as usize)
}
})
.await
}
pub async fn send(&self, packet: &[u8]) -> io::Result<usize> {
self.fd
.async_io(Interest::WRITABLE, |fd| {
let n =
unsafe { libc::write(fd.as_raw_fd(), packet.as_ptr().cast(), packet.len()) };
if n < 0 {
Err(io::Error::last_os_error())
} else {
Ok(n as usize)
}
})
.await
}
}
