From a08fd4002bfae92072f64f8d5e0084e6f248f139 Mon Sep 17 00:00:00 2001
From: Mathias Hall-Andersen <mathias@hall-andersen.dk>
Date: Sun, 13 Oct 2019 22:26:12 +0200
Subject: Work on Linux platform code

---
 src/platform/linux/mod.rs | 179 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 179 insertions(+)
 create mode 100644 src/platform/linux/mod.rs

(limited to 'src/platform/linux/mod.rs')

diff --git a/src/platform/linux/mod.rs b/src/platform/linux/mod.rs
new file mode 100644
index 0000000..ad2b8be
--- /dev/null
+++ b/src/platform/linux/mod.rs
@@ -0,0 +1,179 @@
+use super::Tun;
+use super::TunBind;
+
+use super::super::wireguard::tun::*;
+
+use libc::*;
+
+use std::os::raw::c_short;
+use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
+
+const IFNAMSIZ: usize = 16;
+const TUNSETIFF: u64 = 0x4004_54ca;
+
+const IFF_UP: i16 = 0x1;
+const IFF_RUNNING: i16 = 0x40;
+
+const IFF_TUN: c_short = 0x0001;
+const IFF_NO_PI: c_short = 0x1000;
+
+use std::error::Error;
+use std::fmt;
+use std::sync::atomic::AtomicUsize;
+use std::sync::Arc;
+
+const CLONE_DEVICE_PATH: &'static [u8] = b"/dev/net/tun\0";
+
+const TUN_MAGIC: u8 = b'T';
+const TUN_SET_IFF: u8 = 202;
+
+#[repr(C)]
+struct Ifreq {
+    name: [u8; libc::IFNAMSIZ],
+    flags: c_short,
+    _pad: [u8; 64],
+}
+
+pub struct PlatformTun {}
+
+pub struct PlatformTunReader {
+    fd: RawFd,
+}
+
+pub struct PlatformTunWriter {
+    fd: RawFd,
+}
+
+/* Listens for netlink messages
+ * announcing an MTU update for the interface
+ */
+#[derive(Clone)]
+pub struct PlatformTunMTU {
+    value: Arc<AtomicUsize>,
+}
+
+#[derive(Debug)]
+pub enum LinuxTunError {
+    InvalidTunDeviceName,
+    FailedToOpenCloneDevice,
+    SetIFFIoctlFailed,
+    Closed, // TODO
+}
+
+impl fmt::Display for LinuxTunError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        unimplemented!()
+    }
+}
+
+impl Error for LinuxTunError {
+    fn description(&self) -> &str {
+        unimplemented!()
+    }
+
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        unimplemented!()
+    }
+}
+
+impl MTU for PlatformTunMTU {
+    fn mtu(&self) -> usize {
+        1500
+    }
+}
+
+impl Reader for PlatformTunReader {
+    type Error = LinuxTunError;
+
+    fn read(&self, buf: &mut [u8], offset: usize) -> Result<usize, Self::Error> {
+        debug_assert!(
+            offset < buf.len(),
+            "There is no space for the body of the TUN read"
+        );
+        let n = unsafe { read(self.fd, buf[offset..].as_mut_ptr() as _, buf.len() - offset) };
+        if n < 0 {
+            Err(LinuxTunError::Closed)
+        } else {
+            // conversion is safe
+            Ok(n as usize)
+        }
+    }
+}
+
+impl Writer for PlatformTunWriter {
+    type Error = LinuxTunError;
+
+    fn write(&self, src: &[u8]) -> Result<(), Self::Error> {
+        match unsafe { write(self.fd, src.as_ptr() as _, src.len() as _) } {
+            -1 => Err(LinuxTunError::Closed),
+            _ => Ok(()),
+        }
+    }
+}
+
+impl Tun for PlatformTun {
+    type Error = LinuxTunError;
+    type Reader = PlatformTunReader;
+    type Writer = PlatformTunWriter;
+    type MTU = PlatformTunMTU;
+}
+
+impl TunBind for PlatformTun {
+    fn create(name: &str) -> Result<(Vec<Self::Reader>, Self::Writer, Self::MTU), Self::Error> {
+        // construct request struct
+        let mut req = Ifreq {
+            name: [0u8; libc::IFNAMSIZ],
+            flags: (libc::IFF_TUN | libc::IFF_NO_PI) as c_short,
+            _pad: [0u8; 64],
+        };
+
+        // sanity check length of device name
+        let bs = name.as_bytes();
+        if bs.len() > libc::IFNAMSIZ - 1 {
+            return Err(LinuxTunError::InvalidTunDeviceName);
+        }
+        req.name[..bs.len()].copy_from_slice(bs);
+
+        // open clone device
+        let fd = match unsafe { open(CLONE_DEVICE_PATH.as_ptr() as _, O_RDWR) } {
+            -1 => return Err(LinuxTunError::FailedToOpenCloneDevice),
+            fd => fd,
+        };
+
+        // create TUN device
+        if unsafe { ioctl(fd, TUNSETIFF as _, &req) } < 0 {
+            return Err(LinuxTunError::SetIFFIoctlFailed);
+        }
+
+        // create PlatformTunMTU instance
+
+        Ok((
+            vec![PlatformTunReader { fd }],
+            PlatformTunWriter { fd },
+            PlatformTunMTU {
+                value: Arc::new(AtomicUsize::new(1500)),
+            },
+        ))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::env;
+
+    fn is_root() -> bool {
+        match env::var("USER") {
+            Ok(val) => val == "root",
+            Err(e) => false,
+        }
+    }
+
+    #[test]
+    fn test_tun_create() {
+        if !is_root() {
+            return;
+        }
+        let (readers, writers, mtu) = PlatformTun::create("test").unwrap();
+    }
+}
-- 
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