vpncloud/src/device.rs

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// VpnCloud - Peer-to-Peer VPN
// Copyright (C) 2015-2016 Dennis Schwerdel
// This software is licensed under GPL-3 or newer (see LICENSE.md)
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use std::os::unix::io::{AsRawFd, RawFd};
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use std::io::{self, Error as IoError, Read, Write};
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use std::fs;
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use std::fmt;
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use super::types::Error;
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extern {
fn setup_tap_device(fd: i32, ifname: *mut u8) -> i32;
fn setup_tun_device(fd: i32, ifname: *mut u8) -> i32;
}
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/// The type of a tun/tap device
#[derive(RustcDecodable, Debug, Clone, Copy)]
pub enum Type {
/// Tun interface: This interface transports IP packets.
Tun,
/// Tap interface: This insterface transports Ethernet frames.
Tap
}
impl fmt::Display for Type {
fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
match *self {
Type::Tun => write!(formatter, "tun"),
Type::Tap => write!(formatter, "tap"),
}
}
}
/// Represents a tun/tap device
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pub struct Device {
fd: fs::File,
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ifname: String,
type_: Type,
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}
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impl Device {
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/// Creates a new tun/tap device
///
/// This method creates a new device of the `type_` kind with the name `ifname`.
///
/// The `ifname` must be an interface name not longer than 31 bytes. It can contain the string
/// `%d` which will be replaced with the next free index number that guarantees that the
/// interface name will be free. In this case, the `ifname()` method can be used to obtain the
/// final interface name.
///
/// # Errors
/// This method will return an error when the underlying system call fails. Common cases are:
/// - The special device file `/dev/net/tun` does not exist or is not accessible by the current
/// user.
/// - The interface name is invalid or already in use.
/// - The current user does not have enough permissions to create tun/tap devices (this
/// requires root permissions).
///
/// # Panics
/// This method panics if the interface name is longer than 31 bytes.
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pub fn new(ifname: &str, type_: Type) -> io::Result<Self> {
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let fd = try!(fs::OpenOptions::new().read(true).write(true).open("/dev/net/tun"));
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// Add trailing \0 to interface name
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let mut ifname_string = String::with_capacity(32);
ifname_string.push_str(ifname);
ifname_string.push('\0');
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assert!(ifname_string.len() <= 32);
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let mut ifname_c = ifname_string.into_bytes();
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let res = match type_ {
Type::Tun => unsafe { setup_tun_device(fd.as_raw_fd(), ifname_c.as_mut_ptr()) },
Type::Tap => unsafe { setup_tap_device(fd.as_raw_fd(), ifname_c.as_mut_ptr()) }
};
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match res {
0 => {
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// Remove trailing \0 from name
while ifname_c.last() == Some(&0) {
ifname_c.pop();
}
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Ok(Device{fd: fd, ifname: String::from_utf8(ifname_c).unwrap(), type_: type_})
},
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_ => Err(IoError::last_os_error())
}
}
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/// Returns the interface name of this device.
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#[inline]
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pub fn ifname(&self) -> &str {
&self.ifname
}
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/// Returns the type of this device
#[allow(dead_code)]
#[inline]
pub fn get_type(&self) -> Type {
self.type_
}
/// Creates a dummy device based on an existing file
///
/// This method opens a regular or special file and reads from it to receive packets and
/// writes to it to send packets. This method does not use a networking device and therefore
/// can be used for testing.
///
/// The parameter `path` is the file that should be used. Special files like `/dev/null`,
/// named pipes and unix sockets can be used with this method.
///
/// Both `ifname` and `type_` parameters have no effect.
///
/// # Errors
/// This method will return an error if the file can not be opened for reading and writing.
#[allow(dead_code)]
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pub fn dummy(ifname: &str, path: &str, type_: Type) -> io::Result<Self> {
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Ok(Device{
fd: try!(fs::OpenOptions::new().create(true).read(true).write(true).open(path)),
ifname: ifname.to_string(),
type_: type_
})
}
/// Reads a packet/frame from the device
///
/// This method reads one packet or frame (depending on the device type) into the `buffer`.
/// The `buffer` must be large enough to hold a packet/frame of maximum size, otherwise the
/// packet/frame will be split.
/// The method will block until a packet/frame is ready to be read.
/// On success, the method will return the starting position and the amount of bytes read into
/// the buffer.
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///
/// # Errors
/// This method will return an error if the underlying read call fails.
#[inline]
pub fn read(&mut self, mut buffer: &mut [u8]) -> Result<(usize, usize), Error> {
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let read = try!(self.fd.read(&mut buffer).map_err(|e| Error::TunTapDev("Read error", e)));
let (start, read) = self.correct_data_after_read(&mut buffer, 0, read);
Ok((start, read))
}
#[cfg(any(target_os = "linux", target_os = "android"))]
#[inline]
fn correct_data_after_read(&mut self, _buffer: &mut [u8], start: usize, read: usize) -> (usize, usize) {
(start, read)
}
#[cfg(any(target_os = "bitrig", target_os = "dragonfly",
target_os = "freebsd", target_os = "ios", target_os = "macos",
target_os = "netbsd", target_os = "openbsd"))]
#[inline]
fn correct_data_after_read(&mut self, buffer: &mut [u8], start: usize, read: usize) -> (usize, usize) {
if self.type_ == Type::Tun {
// BSD-based systems add a 4-byte header containing the Ethertype for TUN
assert!(read>=4);
(start+4, read-4)
} else {
(start, read)
}
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}
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/// Writes a packet/frame to the device
///
/// This method writes one packet or frame (depending on the device type) from `data` to the
/// device. The data starts at the position `start` in the buffer. The buffer should have at
/// least 4 bytes of space before the start of the packet.
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/// The method will block until the packet/frame has been written.
///
/// # Errors
/// This method will return an error if the underlying read call fails.
#[inline]
pub fn write(&mut self, mut data: &mut [u8], start: usize) -> Result<(), Error> {
let start = self.correct_data_before_write(&mut data, start);
match self.fd.write_all(&data[start..]) {
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Ok(_) => self.fd.flush().map_err(|e| Error::TunTapDev("Flush error", e)),
Err(e) => Err(Error::TunTapDev("Write error", e))
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}
}
#[cfg(any(target_os = "linux", target_os = "android"))]
#[inline]
fn correct_data_before_write(&mut self, _buffer: &mut [u8], start: usize) -> usize {
start
}
#[cfg(any(target_os = "bitrig", target_os = "dragonfly",
target_os = "freebsd", target_os = "ios", target_os = "macos",
target_os = "netbsd", target_os = "openbsd"))]
#[inline]
fn correct_data_before_write(&mut self, buffer: &mut [u8], start: usize) -> usize {
if self.type_ == Type::Tun {
// BSD-based systems add a 4-byte header containing the Ethertype for TUN
assert!(start>=4);
match buffer[start] >> 4 { // IP version
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4 => buffer[start-4..start].copy_from_slice(&[0x00, 0x00, 0x08, 0x00]),
6 => buffer[start-4..start].copy_from_slice(&[0x00, 0x00, 0x86, 0xdd]),
_ => unreachable!()
}
start-4
} else {
start
}
}
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}
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impl AsRawFd for Device {
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#[inline]
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fn as_raw_fd(&self) -> RawFd {
self.fd.as_raw_fd()
}
}