Add set_mtu for linux

Author: Serock3

talpid-wireguard/src/lib.rs

@@ -51,6 +51,8 @@ mod connectivity_check;
 mod logging;
 mod ping_monitor;
 mod stats;
+#[cfg(target_os = "linux")]
+mod unix;
 #[cfg(wireguard_go)]
 mod wireguard_go;
 #[cfg(target_os = "linux")]

talpid-wireguard/src/unix.rs

@@ -0,0 +1,41 @@
+use std::{io, os::fd::AsRawFd};
+
+use socket2::Domain;
+use talpid_types::ErrorExt;
+
+pub fn set_mtu(interface_name: &str, mtu: u16) -> Result<(), io::Error> {
+    debug_assert_ne!(
+        interface_name, "eth0",
+        "Should be name of mullvad tunnel interface, e.g. 'wg0-mullvad'"
+    );
+
+    let sock = socket2::Socket::new(
+        Domain::IPV4,
+        socket2::Type::STREAM,
+        Some(socket2::Protocol::TCP),
+    )?;
+
+    let mut ifr: libc::ifreq = unsafe { std::mem::zeroed() };
+    if interface_name.len() >= ifr.ifr_name.len() {
+        return Err(io::Error::new(
+            io::ErrorKind::InvalidInput,
+            "Interface name too long",
+        ));
+    }
+
+    unsafe {
+        std::ptr::copy_nonoverlapping(
+            interface_name.as_ptr() as *const i8,
+            &mut ifr.ifr_name as *mut _,
+            interface_name.len(),
+        )
+    };
+    ifr.ifr_ifru.ifru_mtu = mtu as i32;
+
+    if unsafe { libc::ioctl(sock.as_raw_fd(), libc::SIOCSIFMTU, &ifr) } < 0 {
+        let e = std::io::Error::last_os_error();
+        log::error!("{}", e.display_chain_with_msg("SIOCSIFMTU failed"));
+        return Err(e);
+    }
+    Ok(())
+}