change the type of mtu to u16 (#38)

* change the type of mtu to u16

examples/read-async.rs

@@ -47,7 +47,7 @@ async fn main_entry(
     });
 
     let mut dev = tun2::create_as_async(&config)?;
-    let size = dev.as_ref().mtu()? + tun2::PACKET_INFORMATION_LENGTH;
+    let size = dev.as_ref().mtu()? as usize + tun2::PACKET_INFORMATION_LENGTH;
     let mut buf = vec![0; size];
     loop {
         tokio::select! {

src/async/unix_device.rs

@@ -55,9 +55,9 @@ impl AsyncDevice {
     /// Consumes this AsyncDevice and return a Framed object (unified Stream and Sink interface)
     pub fn into_framed(self) -> Framed<Self, TunPacketCodec> {
         let mtu = self.as_ref().mtu().unwrap_or(crate::DEFAULT_MTU);
-        let codec = TunPacketCodec::new(mtu);
+        let codec = TunPacketCodec::new(mtu as usize);
         // associate mtu with the capacity of ReadBuf
-        Framed::with_capacity(self, codec, mtu)
+        Framed::with_capacity(self, codec, mtu as usize)
     }
 }
 

src/async/win_device.rs

@@ -56,9 +56,9 @@ impl AsyncDevice {
     /// Consumes this AsyncDevice and return a Framed object (unified Stream and Sink interface)
     pub fn into_framed(self) -> Framed<Self, TunPacketCodec> {
         let mtu = self.as_ref().mtu().unwrap_or(crate::DEFAULT_MTU);
-        let codec = TunPacketCodec::new(mtu);
-        // guarantee to avoid the mtu of wintun may far away larger than the default provided capacity of RedBuff of Framed
-        Framed::with_capacity(self, codec, mtu)
+        let codec = TunPacketCodec::new(mtu as usize);
+        // guarantee to avoid the mtu of wintun may far away larger than the default provided capacity of ReadBuf of Framed
+        Framed::with_capacity(self, codec, mtu as usize)
     }
 }
 

src/configuration.rs

@@ -38,7 +38,7 @@ pub struct Configuration {
     pub(crate) destination: Option<IpAddr>,
     pub(crate) broadcast: Option<IpAddr>,
     pub(crate) netmask: Option<IpAddr>,
-    pub(crate) mtu: Option<usize>,
+    pub(crate) mtu: Option<u16>,
     pub(crate) enabled: Option<bool>,
     pub(crate) layer: Option<Layer>,
     pub(crate) queues: Option<usize>,
@@ -95,7 +95,7 @@ impl Configuration {
     /// Set the MTU.
     ///
     /// [Note: mtu on the Windows platform is always 65535 due to wintun -- end note]
-    pub fn mtu(&mut self, value: usize) -> &mut Self {
+    pub fn mtu(&mut self, value: u16) -> &mut Self {
         // mtu on windows platform is always 65535 due to wintun
         if cfg!(target_family = "unix") {
             self.mtu = Some(value);

src/device.rs

@@ -82,12 +82,12 @@ pub trait AbstractDevice: Read + Write {
     fn set_netmask(&mut self, value: IpAddr) -> Result<()>;
 
     /// Get the MTU.
-    fn mtu(&self) -> Result<usize>;
+    fn mtu(&self) -> Result<u16>;
 
     /// Set the MTU.
     ///
     /// [Note: This setting has no effect on the Windows platform due to the mtu of wintun is always 65535. --end note]
-    fn set_mtu(&mut self, value: usize) -> Result<()>;
+    fn set_mtu(&mut self, value: u16) -> Result<()>;
 
     /// Return whether the underlying tun device on the platform has packet information
     ///

src/error.rs

@@ -38,6 +38,9 @@ pub enum Error {
     #[error("invalid queues number")]
     InvalidQueuesNumber,
 
+    #[error("out of range integral type conversion attempted")]
+    TryFromIntError,
+
     #[error(transparent)]
     Io(#[from] std::io::Error),
 

src/lib.rs

@@ -37,8 +37,8 @@ pub fn configure() -> Configuration {
 }
 
 #[cfg(unix)]
-pub const DEFAULT_MTU: usize = 1500;
+pub const DEFAULT_MTU: u16 = 1500;
 #[cfg(windows)]
-pub const DEFAULT_MTU: usize = 0xFFFF; // 65535
+pub const DEFAULT_MTU: u16 = 0xFFFF; // 65535
 
 pub const PACKET_INFORMATION_LENGTH: usize = 4;

src/platform/android/device.rs

@@ -131,12 +131,12 @@ impl AbstractDevice for Device {
         Ok(())
     }
 
-    fn mtu(&self) -> Result<usize> {
+    fn mtu(&self) -> Result<u16> {
         // TODO: must get the mtu from the underlying device driver
         Ok(self.tun.mtu())
     }
 
-    fn set_mtu(&mut self, value: usize) -> Result<()> {
+    fn set_mtu(&mut self, value: u16) -> Result<()> {
         // TODO: must set the mtu to the underlying device driver
         self.tun.set_mtu(value);
         Ok(())

src/platform/ios/device.rs

@@ -140,12 +140,12 @@ impl AbstractDevice for Device {
         Ok(())
     }
 
-    fn mtu(&self) -> Result<usize> {
+    fn mtu(&self) -> Result<u16> {
         // TODO: must get the mtu from the underlying device driver
         Ok(self.tun.mtu())
     }
 
-    fn set_mtu(&mut self, value: usize) -> Result<()> {
+    fn set_mtu(&mut self, value: u16) -> Result<()> {
         // TODO: must set the mtu to the underlying device driver
         self.tun.set_mtu(value);
         Ok(())

src/platform/linux/device.rs

@@ -380,19 +380,22 @@ impl AbstractDevice for Device {
         }
     }
 
-    fn mtu(&self) -> Result<usize> {
+    fn mtu(&self) -> Result<u16> {
         unsafe {
             let mut req = self.request();
 
             if siocgifmtu(self.ctl.as_raw_fd(), &mut req) < 0 {
                 return Err(io::Error::last_os_error().into());
             }
 
-            Ok(req.ifr_ifru.ifru_mtu as usize)
+            req.ifr_ifru
+                .ifru_mtu
+                .try_into()
+                .map_err(|_| Error::TryFromIntError)
         }
     }
 
-    fn set_mtu(&mut self, value: usize) -> Result<()> {
+    fn set_mtu(&mut self, value: u16) -> Result<()> {
         unsafe {
             let mut req = self.request();
             req.ifr_ifru.ifru_mtu = value as i32;

src/platform/linux/mod.rs

@@ -31,6 +31,7 @@ pub struct PlatformConfig {
     pub(crate) ensure_root_privileges: bool,
 }
 
+/// `packet_information` is default to be `false` and `ensure_root_privileges` is default to be `true`.
 impl Default for PlatformConfig {
     fn default() -> Self {
         PlatformConfig {

src/platform/macos/device.rs

@@ -397,7 +397,7 @@ impl AbstractDevice for Device {
         }
     }
 
-    fn mtu(&self) -> Result<usize> {
+    fn mtu(&self) -> Result<u16> {
         let ctl = self.ctl.as_ref().ok_or(Error::InvalidConfig)?;
         unsafe {
             let mut req = self.request()?;
@@ -406,11 +406,14 @@ impl AbstractDevice for Device {
                 return Err(io::Error::last_os_error().into());
             }
 
-            Ok(req.ifr_ifru.ifru_mtu as usize)
+            req.ifr_ifru
+                .ifru_mtu
+                .try_into()
+                .map_err(|_| Error::TryFromIntError)
         }
     }
 
-    fn set_mtu(&mut self, value: usize) -> Result<()> {
+    fn set_mtu(&mut self, value: u16) -> Result<()> {
         let ctl = self.ctl.as_ref().ok_or(Error::InvalidConfig)?;
         unsafe {
             let mut req = self.request()?;

src/platform/posix/split.rs

@@ -71,8 +71,8 @@ pub struct Reader {
 }
 
 impl Reader {
-    pub(crate) fn set_mtu(&mut self, value: usize) {
-        self.buf.resize(value + self.offset, 0);
+    pub(crate) fn set_mtu(&mut self, value: u16) {
+        self.buf.resize(value as usize + self.offset, 0);
     }
 }
 
@@ -115,8 +115,8 @@ pub struct Writer {
 }
 
 impl Writer {
-    pub(crate) fn set_mtu(&mut self, value: usize) {
-        self.buf.resize(value + self.offset, 0);
+    pub(crate) fn set_mtu(&mut self, value: u16) {
+        self.buf.resize(value as usize + self.offset, 0);
     }
 }
 
@@ -164,22 +164,22 @@ pub struct Tun {
 }
 
 impl Tun {
-    pub(crate) fn new(fd: Fd, mtu: usize, packet_information: bool) -> Self {
+    pub(crate) fn new(fd: Fd, mtu: u16, packet_information: bool) -> Self {
         let fd = Arc::new(fd);
         let offset = if packet_information { PIL } else { 0 };
         Self {
             reader: Reader {
                 fd: fd.clone(),
                 offset,
-                buf: vec![0; mtu + offset],
+                buf: vec![0; mtu as usize + offset],
             },
             writer: Writer {
                 fd,
                 offset,
-                buf: vec![0; mtu + offset],
+                buf: vec![0; mtu as usize + offset],
             },
             info: TunInfo {
-                mtu,
+                mtu: mtu as usize,
                 packet_information,
             },
         }
@@ -189,14 +189,14 @@ impl Tun {
         self.reader.fd.set_nonblock()
     }
 
-    pub fn set_mtu(&mut self, value: usize) {
-        self.info.mtu = value;
+    pub fn set_mtu(&mut self, value: u16) {
+        self.info.mtu = value as usize;
         self.reader.set_mtu(value);
         self.writer.set_mtu(value);
     }
 
-    pub fn mtu(&self) -> usize {
-        self.info.mtu
+    pub fn mtu(&self) -> u16 {
+        self.info.mtu as u16
     }
 
     pub fn packet_information(&self) -> bool {

src/platform/windows/device.rs

@@ -25,7 +25,7 @@ use crate::error::{Error, Result};
 /// A TUN device using the wintun driver.
 pub struct Device {
     pub(crate) tun: Tun,
-    mtu: usize,
+    mtu: u16,
 }
 
 impl Device {
@@ -181,13 +181,13 @@ impl AbstractDevice for Device {
     }
 
     /// The return value is always `Ok(65535)` due to wintun
-    fn mtu(&self) -> Result<usize> {
+    fn mtu(&self) -> Result<u16> {
         // Note: wintun mtu is always 65535
         Ok(self.mtu)
     }
 
     /// This setting has no effect since the mtu of wintun is always 65535
-    fn set_mtu(&mut self, _: usize) -> Result<()> {
+    fn set_mtu(&mut self, _: u16) -> Result<()> {
         // Note: no-op due to mtu of wintun is always 65535
         Ok(())
     }