Use kldload instead of kld_load

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "defguard_wireguard_rs"
-version = "0.9.5"
+version = "0.9.6"
 edition = "2024"
 rust-version = "1.87"
 description = "A unified multi-platform high-level API for managing WireGuard interfaces"
@@ -44,7 +44,7 @@ wireguard-nt = "0.5"
 [target.'cfg(target_os = "linux")'.dependencies]
 netlink-packet-core = "0.8"
 netlink-packet-generic = "0.4"
-netlink-packet-route = "0.29"
+netlink-packet-route = "0.30"
 netlink-packet-utils = "0.6"
 netlink-packet-wireguard = "0.3"
 netlink-sys = "0.8"

src/bsd/mod.rs

@@ -311,15 +311,26 @@ pub fn delete_peer(if_name: &str, public_key: &Key) -> Result<(), IoError> {
     wg_data.write_data()
 }
 
+#[cfg(target_os = "freebsd")]
+#[link(name = "c")]
+unsafe extern "C" {
+    // Note: libc crate doesn't export kldload.
+    fn kldload(file: *const libc::c_char) -> libc::c_int;
+}
+
 #[cfg(target_os = "freebsd")]
 pub fn load_wireguard_kernel_module() -> Result<(), IoError> {
-    // Ignore the return value for the time being.
-    let retval = unsafe { libc::kld_load(c"if_wg".as_ptr()) };
-    if retval == 0 {
-        Ok(())
-    } else {
-        Err(IoError::KernelModule)
+    // Prefer kldload(2) to kld_load(3).
+    // The latter needs libutil, which differs between FreeBSD 14 and 15.
+    let retval = unsafe { kldload(c"if_wg".as_ptr()) };
+    // Based on https://github.com/freebsd/freebsd-src/blob/main/lib/libutil/kld.c#L70
+    if retval == -1 {
+        let err = std::io::Error::last_os_error();
+        if err.raw_os_error() != Some(libc::EEXIST) {
+            return Err(IoError::KernelModule);
+        }
     }
+    Ok(())
 }
 
 pub fn create_interface(if_name: &str) -> Result<(), IoError> {