Finding available utun name for MacOS

Cargo.lock

@@ -1044,6 +1044,15 @@ version = "2.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8f518f335dce6725a761382244631d86cf0ccb2863413590b31338feb467f9c3"
 
+[[package]]
+name = "ipnetwork"
+version = "0.20.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bf466541e9d546596ee94f9f69590f89473455f88372423e0008fc1a7daf100e"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "is-terminal"
 version = "0.4.12"
@@ -1254,6 +1263,7 @@ dependencies = [
  "netdev",
  "nix 0.29.0",
  "openssl",
+ "pnet",
  "quinn",
  "rand",
  "rcgen",
@@ -1435,6 +1445,12 @@ dependencies = [
  "memoffset",
 ]
 
+[[package]]
+name = "no-std-net"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "43794a0ace135be66a25d3ae77d41b91615fb68ae937f904090203e81f755b65"
+
 [[package]]
 name = "nom"
 version = "7.1.3"
@@ -1668,6 +1684,97 @@ version = "0.3.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d231b230927b5e4ad203db57bbcbee2802f6bce620b1e4a9024a07d94e2907ec"
 
+[[package]]
+name = "pnet"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "682396b533413cc2e009fbb48aadf93619a149d3e57defba19ff50ce0201bd0d"
+dependencies = [
+ "ipnetwork",
+ "pnet_base",
+ "pnet_datalink",
+ "pnet_packet",
+ "pnet_sys",
+ "pnet_transport",
+]
+
+[[package]]
+name = "pnet_base"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ffc190d4067df16af3aba49b3b74c469e611cad6314676eaf1157f31aa0fb2f7"
+dependencies = [
+ "no-std-net",
+]
+
+[[package]]
+name = "pnet_datalink"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e79e70ec0be163102a332e1d2d5586d362ad76b01cec86f830241f2b6452a7b7"
+dependencies = [
+ "ipnetwork",
+ "libc",
+ "pnet_base",
+ "pnet_sys",
+ "winapi",
+]
+
+[[package]]
+name = "pnet_macros"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "13325ac86ee1a80a480b0bc8e3d30c25d133616112bb16e86f712dcf8a71c863"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "regex",
+ "syn 2.0.48",
+]
+
+[[package]]
+name = "pnet_macros_support"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eed67a952585d509dd0003049b1fc56b982ac665c8299b124b90ea2bdb3134ab"
+dependencies = [
+ "pnet_base",
+]
+
+[[package]]
+name = "pnet_packet"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c96ebadfab635fcc23036ba30a7d33a80c39e8461b8bd7dc7bb186acb96560f"
+dependencies = [
+ "glob",
+ "pnet_base",
+ "pnet_macros",
+ "pnet_macros_support",
+]
+
+[[package]]
+name = "pnet_sys"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7d4643d3d4db6b08741050c2f3afa9a892c4244c085a72fcda93c9c2c9a00f4b"
+dependencies = [
+ "libc",
+ "winapi",
+]
+
+[[package]]
+name = "pnet_transport"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5f604d98bc2a6591cf719b58d3203fd882bdd6bf1db696c4ac97978e9f4776bf"
+dependencies = [
+ "libc",
+ "pnet_base",
+ "pnet_packet",
+ "pnet_sys",
+]
+
 [[package]]
 name = "polyval"
 version = "0.6.1"

mycelium/Cargo.toml

@@ -46,6 +46,7 @@ netdev = "0.30.0"
 openssl = { version = "0.10.66", optional = true }
 tokio-openssl = { version = "0.6.4", optional = true }
 arc-swap = "1.7.1"
+pnet = "0.35.0"
 
 [target.'cfg(target_os = "linux")'.dependencies]
 rtnetlink = "0.14.1"

mycelium/src/tun/darwin.rs

@@ -81,13 +81,9 @@ pub async fn new(
     ),
     Box<dyn std::error::Error>,
 > {
-    if !validate_utun_name(&tun_config.name) {
-        return Err(std::io::Error::new(
-            std::io::ErrorKind::InvalidInput,
-            "TUN device name must be of the form 'utunXXX...' where X is a digit",
-        ))?;
-    }
-    let mut tun = match create_tun_interface(&tun_config.name) {
+    let tun_name = find_available_utun_name(&tun_config.name)?;
+
+    let mut tun = match create_tun_interface(&tun_name) {
         Ok(tun) => tun,
         Err(e) => {
             error!(
@@ -97,7 +93,7 @@ pub async fn new(
             return Err(e);
         }
     };
-    let iface = Iface::by_name(&tun_config.name)?;
+    let iface = Iface::by_name(&tun_name)?;
     iface.add_address(tun_config.node_subnet, tun_config.route_subnet)?;
 
     let (tun_sink, mut sink_receiver) = mpsc::channel::<PacketBuffer>(1000);
@@ -174,6 +170,40 @@ fn validate_utun_name(input: &str) -> bool {
         .is_ok()
 }
 
+/// Find an available utun interface name
+fn find_available_utun_name(preferred_name: &str) -> Result<String, Box<dyn std::error::Error>> {
+    let interfaces = datalink::interfaces();
+    let utun_interfaces: Vec<_> = interfaces
+        .iter()
+        .filter(|iface| iface.name.starts_with("utun"))
+        .collect();
+
+    if !preferred_name.is_empty() && validate_utun_name(preferred_name) {
+        if !utun_interfaces
+            .iter()
+            .any(|iface| iface.name == preferred_name)
+        {
+            return Ok(preferred_name.to_string());
+        }
+        error!("Preferred utun name '{}' is already in use", preferred_name);
+    }
+
+    let max_utun_number = utun_interfaces
+        .iter()
+        .filter_map(|iface| iface.name[4..].parse::<u64>().ok())
+        .max()
+        .unwrap_or(0);
+
+    let new_utun_number = max_utun_number + 1;
+    let new_utun_name = format!("utun{}", new_utun_number);
+
+    if validate_utun_name(&new_utun_name) {
+        Ok(new_utun_name)
+    } else {
+        Err("Could not find an available utun interface name".into())
+    }
+}
+
 /// Create a new TUN interface
 fn create_tun_interface(name: &str) -> Result<tun::AsyncDevice, Box<dyn std::error::Error>> {
     let mut config = tun::Configuration::default();