initial

rust/src/tunnel.rs

@@ -0,0 +1,79 @@
+use anyhow::Result;
+use std::net::Ipv4Addr;
+use tracing::info;
+
+/// Configuration for creating a TUN device.
+pub struct TunConfig {
+    pub name: String,
+    pub address: Ipv4Addr,
+    pub netmask: Ipv4Addr,
+    pub mtu: u16,
+}
+
+impl Default for TunConfig {
+    fn default() -> Self {
+        Self {
+            name: "smartvpn0".to_string(),
+            address: Ipv4Addr::new(10, 8, 0, 1),
+            netmask: Ipv4Addr::new(255, 255, 255, 0),
+            mtu: 1420,
+        }
+    }
+}
+
+/// Create and configure a TUN device.
+/// Returns an async TUN device handle.
+pub fn create_tun(config: &TunConfig) -> Result<tun::AsyncDevice> {
+    let mut tun_config = tun::Configuration::default();
+    tun_config
+        .tun_name(&config.name)
+        .address(config.address)
+        .netmask(config.netmask)
+        .mtu(config.mtu as u16)
+        .up();
+
+    #[cfg(target_os = "linux")]
+    tun_config.platform_config(|p| {
+        p.ensure_root_privileges(true);
+    });
+
+    let device = tun::create_as_async(&tun_config)?;
+    info!(
+        "TUN device {} created: addr={}, mtu={}",
+        config.name, config.address, config.mtu
+    );
+    Ok(device)
+}
+
+/// Set up routing: add a route for the VPN subnet through the TUN device.
+pub async fn add_route(subnet: &str, device_name: &str) -> Result<()> {
+    let output = tokio::process::Command::new("ip")
+        .args(["route", "add", subnet, "dev", device_name])
+        .output()
+        .await?;
+
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        // Ignore "File exists" errors (route already set)
+        if !stderr.contains("File exists") {
+            anyhow::bail!("Failed to add route: {}", stderr);
+        }
+    }
+
+    info!("Added route {} via {}", subnet, device_name);
+    Ok(())
+}
+
+/// Remove a route.
+pub async fn remove_route(subnet: &str, device_name: &str) -> Result<()> {
+    let output = tokio::process::Command::new("ip")
+        .args(["route", "del", subnet, "dev", device_name])
+        .output()
+        .await?;
+
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        tracing::warn!("Failed to remove route (may not exist): {}", stderr);
+    }
+    Ok(())
+}