add apply_settings switch for Linux configutation

README.md

@@ -43,6 +43,7 @@ fn main() {
 	#[cfg(target_os = "linux")]
 	config.platform(|config| {
 		config.packet_information(true);
+        config.apply_settings(true);
 	});
 
 	let mut dev = tun::create(&config).unwrap();

examples/ping-tun.rs

@@ -29,6 +29,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     #[cfg(target_os = "linux")]
     config.platform(|config| {
         config.packet_information(true);
+        config.apply_settings(true);
     });
 
     #[cfg(target_os = "windows")]

examples/read-async.rs

@@ -27,6 +27,7 @@ async fn main() {
     #[cfg(target_os = "linux")]
     config.platform(|config| {
         config.packet_information(true);
+        config.apply_settings(true);
     });
 
     let dev = tun::create_as_async(&config).unwrap();

examples/read.rs

@@ -26,6 +26,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     #[cfg(target_os = "linux")]
     config.platform(|config| {
         config.packet_information(true);
+        config.apply_settings(true);
     });
 
     let mut dev = tun::create(&config)?;

src/platform/linux/device.rs

@@ -108,7 +108,9 @@ impl Device {
             Device { name, queues, ctl }
         };
 
-        device.configure(config)?;
+        if config.platform.apply_settings {
+            device.configure(config)?;
+        }
 
         Ok(device)
     }

src/platform/linux/mod.rs

@@ -23,9 +23,19 @@ use crate::configuration::Configuration as C;
 use crate::error::*;
 
 /// Linux-only interface configuration.
-#[derive(Copy, Clone, Default, Debug)]
+#[derive(Copy, Clone, Debug)]
 pub struct Configuration {
     pub(crate) packet_information: bool,
+    pub(crate) apply_settings: bool,
+}
+
+impl Default for Configuration {
+    fn default() -> Self {
+        Configuration {
+            packet_information: false,
+            apply_settings: true,
+        }
+    }
 }
 
 impl Configuration {
@@ -35,6 +45,12 @@ impl Configuration {
         self.packet_information = value;
         self
     }
+
+    /// Enable or disable to assign IP/netmask/destination etc.
+    pub fn apply_settings(&mut self, value: bool) -> &mut Self {
+        self.apply_settings = value;
+        self
+    }
 }
 
 /// Create a TUN device with the given name.