feat(ffi): add config server client bindings (#2320)

Add config server client support for the C FFI and Android JNI bindings.

Reuse the existing easytier::web_client::run_web_client path and 
NetworkInstanceManager; OHOS is unchanged.

Report successful remote config apply/delete operations through a 
callback, with one JSON event per affected instance.

Keep the config server client and FFI data plane mutually exclusive: once 
either side is in use, the other side returns an error instead of sharing
lifecycle state.

Cargo.lock

@@ -2385,6 +2385,7 @@ version = "0.1.0"
 dependencies = [
  "android_logger",
  "easytier",
+ "easytier-ffi",
  "jni",
  "log",
  "once_cell",
@@ -2396,13 +2397,17 @@ dependencies = [
 name = "easytier-ffi"
 version = "0.1.0"
 dependencies = [
+ "async-trait",
  "dashmap",
  "easytier",
+ "log",
  "once_cell",
+ "percent-encoding",
  "serde",
  "serde_json",
  "tokio",
  "tokio-util",
+ "url",
  "uuid",
 ]
 

easytier-contrib/easytier-android-jni/Cargo.toml

@@ -13,4 +13,5 @@ log = "0.4"
 android_logger = "0.13"
 serde = { version = "1.0.220", features = ["derive"] }
 serde_json = "1.0"
-easytier = { path = "../../easytier" }
+easytier = { path = "../../easytier" }
+easytier-ffi = { path = "../easytier-ffi", default-features = false }

easytier-contrib/easytier-android-jni/build.rs

@@ -0,0 +1,17 @@
+use std::{env, path::PathBuf};
+
+fn main() {
+    let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap_or_default();
+    if !matches!(target_os.as_str(), "android" | "linux") {
+        return;
+    }
+
+    let manifest_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());
+    let exports = manifest_dir.join("exports.map");
+    println!("cargo:rerun-if-changed={}", exports.display());
+    println!(
+        "cargo:rustc-cdylib-link-arg=-Wl,--version-script={}",
+        exports.display()
+    );
+    println!("cargo:rustc-cdylib-link-arg=-Wl,--exclude-libs,ALL");
+}

easytier-contrib/easytier-android-jni/exports.map

@@ -0,0 +1,6 @@
+{
+    global:
+        Java_com_easytier_jni_EasyTierJNI_*;
+    local:
+        *;
+};

easytier-contrib/easytier-android-jni/kotlin/com/easytier/jni/EasyTierJNI.kt

@@ -1,5 +1,9 @@
 package com.easytier.jni
 
+fun interface ConfigServerEventCallback {
+    fun onEvent(eventJson: String)
+}
+
 /** EasyTier JNI 接口类 提供 Android 应用调用 EasyTier 网络功能的接口 */
 object EasyTierJNI {
 
@@ -33,6 +37,35 @@ object EasyTierJNI {
      */
     @JvmStatic external fun runNetworkInstance(config: String): Int
 
+    /**
+     * 启动配置服务器客户端
+     * @param url 配置服务器 URL
+     * @param hostname 主机名，传入 null 使用系统主机名
+     * @param machineId 稳定机器 ID，由调用方负责持久化
+     * @param secureMode 是否启用 secure mode
+     * @param callback 远程配置应用/删除事件回调
+     * @return 0 表示成功，-1 表示失败
+     * @throws RuntimeException 当客户端启动失败时抛出异常
+     */
+    @JvmStatic
+    external fun startConfigServerClient(
+            url: String,
+            hostname: String?,
+            machineId: String,
+            secureMode: Boolean,
+            callback: ConfigServerEventCallback?
+    ): Int
+
+    /**
+     * 停止配置服务器客户端
+     * @return 0 表示成功，-1 表示失败
+     * @throws RuntimeException 当客户端停止失败时抛出异常
+     */
+    @JvmStatic external fun stopConfigServerClient(): Int
+
+    /** 查询配置服务器客户端是否已连接 */
+    @JvmStatic external fun isConfigServerClientConnected(): Boolean
+
     /**
      * 保留指定的网络实例，停止其他实例
      * @param instanceNames 要保留的实例名称数组，传入 null 或空数组将停止所有实例
@@ -44,7 +77,7 @@ object EasyTierJNI {
     /**
      * 收集网络信息
      * @param maxLength 最大返回条目数
-     * @return 包含网络信息的字符串数组，每个元素格式为 "key=value"
+     * @return 包含网络信息的 JSON 字符串
      * @throws RuntimeException 当操作失败时抛出异常
      */
     @JvmStatic external fun collectNetworkInfos(maxLength: Int): String?

easytier-contrib/easytier-android-jni/src/callback.rs

@@ -0,0 +1,124 @@
+use std::{
+    ffi::{CStr, c_char, c_void},
+    sync::{Arc, Mutex, MutexGuard},
+};
+
+use easytier_ffi::ConfigServerEventCallback;
+use jni::JNIEnv;
+use jni::objects::{GlobalRef, JObject, JValue};
+use once_cell::sync::Lazy;
+
+use crate::error;
+
+pub(crate) struct JniConfigServerCallback {
+    java_vm: jni::JavaVM,
+    callback: GlobalRef,
+}
+
+static CONFIG_SERVER_CALLBACK: Lazy<Mutex<Option<Arc<JniConfigServerCallback>>>> =
+    Lazy::new(|| Mutex::new(None));
+
+pub(crate) fn lock_callback_storage()
+-> Result<MutexGuard<'static, Option<Arc<JniConfigServerCallback>>>, String> {
+    CONFIG_SERVER_CALLBACK
+        .lock()
+        .map_err(|e| format!("Failed to lock config server callback: {}", e))
+}
+
+pub(crate) fn new_callback(
+    env: &mut JNIEnv,
+    callback: &JObject,
+) -> Result<Arc<JniConfigServerCallback>, String> {
+    let java_vm = env
+        .get_java_vm()
+        .map_err(|e| format!("Failed to get JavaVM: {:?}", e))?;
+    let callback = env
+        .new_global_ref(callback)
+        .map_err(|e| format!("Failed to create callback global ref: {:?}", e))?;
+    Ok(Arc::new(JniConfigServerCallback { java_vm, callback }))
+}
+
+pub(crate) fn callback_fn(
+    callback: &Option<Arc<JniConfigServerCallback>>,
+) -> ConfigServerEventCallback {
+    callback
+        .as_ref()
+        .map(|_| config_server_event_callback as unsafe extern "C" fn(*const c_char, *mut c_void))
+}
+
+pub(crate) fn user_data(callback: &Option<Arc<JniConfigServerCallback>>) -> *mut c_void {
+    callback
+        .as_ref()
+        .map(|callback| Arc::as_ptr(callback) as *mut c_void)
+        .unwrap_or(std::ptr::null_mut())
+}
+
+impl JniConfigServerCallback {
+    fn clear_pending_exception(
+        env: &mut JNIEnv,
+        context: &str,
+        error: &dyn std::fmt::Debug,
+    ) -> String {
+        match env.exception_check() {
+            Ok(true) => {
+                if let Err(clear_err) = env.exception_clear() {
+                    return format!(
+                        "{}: {:?}; failed to clear pending Java exception: {:?}",
+                        context, error, clear_err
+                    );
+                }
+            }
+            Ok(false) => {}
+            Err(check_err) => {
+                return format!(
+                    "{}: {:?}; failed to check pending Java exception: {:?}",
+                    context, error, check_err
+                );
+            }
+        }
+
+        format!("{}: {:?}", context, error)
+    }
+
+    fn on_event(&self, event_json: *const c_char) -> Result<(), String> {
+        let event_json = unsafe { CStr::from_ptr(event_json) }
+            .to_str()
+            .map_err(|e| format!("Invalid config server event JSON: {:?}", e))?;
+        let mut env = self
+            .java_vm
+            .attach_current_thread()
+            .map_err(|e| format!("Failed to attach callback thread: {:?}", e))?;
+        let event_json = env.new_string(event_json).map_err(|e| {
+            Self::clear_pending_exception(&mut env, "Failed to create event string", &e)
+        })?;
+
+        if let Err(e) = env.call_method(
+            self.callback.as_obj(),
+            "onEvent",
+            "(Ljava/lang/String;)V",
+            &[JValue::from(&event_json)],
+        ) {
+            return Err(Self::clear_pending_exception(
+                &mut env,
+                "Failed to call config server callback",
+                &e,
+            ));
+        }
+        Ok(())
+    }
+}
+
+unsafe extern "C" fn config_server_event_callback(
+    event_json: *const c_char,
+    user_data: *mut c_void,
+) {
+    if event_json.is_null() || user_data.is_null() {
+        return;
+    }
+
+    let callback = unsafe { &*(user_data as *const JniConfigServerCallback) };
+
+    if let Err(error) = callback.on_event(event_json) {
+        error::set_callback_error(error);
+    }
+}

easytier-contrib/easytier-android-jni/src/config_server_api.rs

@@ -0,0 +1,140 @@
+use std::ptr;
+
+use easytier_ffi::{
+    in_config_server_callback, is_config_server_client_connected, start_config_server_client,
+    stop_config_server_client,
+};
+use jni::JNIEnv;
+use jni::objects::{JClass, JObject, JString};
+use jni::sys::{JNI_FALSE, JNI_TRUE, jboolean, jint};
+
+use crate::{
+    callback, error,
+    strings::{jstring_to_cstring, optional_jstring_to_cstring},
+};
+
+pub(crate) fn start_config_server_client_jni(
+    env: &mut JNIEnv,
+    config_server_url: JString,
+    hostname: JString,
+    machine_id: JString,
+    secure_mode: jboolean,
+    callback_obj: JObject,
+) -> jint {
+    if in_config_server_callback() {
+        error::throw_exception(
+            env,
+            "Cannot start config server client from config server callback",
+        );
+        return -1;
+    }
+
+    let config_server_url = match jstring_to_cstring(env, &config_server_url) {
+        Ok(cstr) => cstr,
+        Err(e) => {
+            error::throw_exception(env, &format!("Invalid config server URL: {}", e));
+            return -1;
+        }
+    };
+    let hostname = match optional_jstring_to_cstring(env, &hostname) {
+        Ok(cstr) => cstr,
+        Err(e) => {
+            error::throw_exception(env, &format!("Invalid hostname: {}", e));
+            return -1;
+        }
+    };
+    let machine_id = match jstring_to_cstring(env, &machine_id) {
+        Ok(cstr) => cstr,
+        Err(e) => {
+            error::throw_exception(env, &format!("Invalid machine ID: {}", e));
+            return -1;
+        }
+    };
+
+    let callback_ref = if callback_obj.is_null() {
+        None
+    } else {
+        match callback::new_callback(env, &callback_obj) {
+            Ok(state) => Some(state),
+            Err(e) => {
+                error::throw_exception(env, &e);
+                return -1;
+            }
+        }
+    };
+
+    let mut callback_guard = match callback::lock_callback_storage() {
+        Ok(guard) => guard,
+        Err(e) => {
+            error::throw_exception(env, &e);
+            return -1;
+        }
+    };
+    if callback_guard.is_none() {
+        error::clear_callback_error();
+    }
+
+    let callback_fn = callback::callback_fn(&callback_ref);
+    let user_data = callback::user_data(&callback_ref);
+    let result = unsafe {
+        start_config_server_client(
+            config_server_url.as_ptr(),
+            hostname
+                .as_ref()
+                .map(|value| value.as_ptr())
+                .unwrap_or(ptr::null()),
+            machine_id.as_ptr(),
+            secure_mode == JNI_TRUE,
+            callback_fn,
+            user_data,
+        )
+    };
+    if result != 0 {
+        if let Some(error_msg) = error::get_last_error() {
+            error::throw_exception(env, &error_msg);
+        }
+        return result;
+    }
+
+    *callback_guard = callback_ref;
+    result
+}
+
+pub(crate) fn stop_config_server_client_jni(mut env: JNIEnv, _class: JClass) -> jint {
+    if in_config_server_callback() {
+        let result = stop_config_server_client();
+        if result != 0
+            && let Some(error_msg) = error::get_last_error()
+        {
+            error::throw_exception(&mut env, &error_msg);
+        }
+        return result;
+    }
+
+    let mut callback_guard = match callback::lock_callback_storage() {
+        Ok(guard) => guard,
+        Err(e) => {
+            error::throw_exception(&mut env, &e);
+            return -1;
+        }
+    };
+
+    let result = stop_config_server_client();
+    if result != 0 {
+        if let Some(error_msg) = error::get_last_error() {
+            error::throw_exception(&mut env, &error_msg);
+        }
+        return result;
+    }
+
+    *callback_guard = None;
+    result
+}
+
+pub(crate) fn is_config_server_client_connected_jni(_env: JNIEnv, _class: JClass) -> jboolean {
+    if is_config_server_client_connected() != 0 {
+        JNI_TRUE
+    } else {
+        JNI_FALSE
+    }
+}

easytier-contrib/easytier-android-jni/src/error.rs

@@ -0,0 +1,74 @@
+use std::{
+    ffi::{CStr, c_char},
+    ptr,
+    sync::Mutex,
+};
+
+use easytier_ffi::{free_string, get_error_msg};
+use jni::JNIEnv;
+use jni::objects::JClass;
+use jni::sys::jstring;
+use once_cell::sync::Lazy;
+
+static JNI_CALLBACK_ERROR: Lazy<Mutex<Option<String>>> = Lazy::new(|| Mutex::new(None));
+
+pub(crate) fn set_callback_error(error: String) {
+    log::error!("{}", error);
+    if let Ok(mut guard) = JNI_CALLBACK_ERROR.lock() {
+        *guard = Some(error);
+    }
+}
+
+pub(crate) fn clear_callback_error() {
+    if let Ok(mut guard) = JNI_CALLBACK_ERROR.lock() {
+        *guard = None;
+    }
+}
+
+fn take_callback_error() -> Option<String> {
+    JNI_CALLBACK_ERROR
+        .lock()
+        .ok()
+        .and_then(|mut guard| guard.take())
+}
+
+fn get_ffi_last_error() -> Option<String> {
+    unsafe {
+        let mut error_ptr: *const c_char = ptr::null();
+        get_error_msg(&mut error_ptr);
+        if error_ptr.is_null() {
+            None
+        } else {
+            let error_cstr = CStr::from_ptr(error_ptr);
+            let error_str = error_cstr.to_string_lossy().into_owned();
+            free_string(error_ptr);
+            Some(error_str)
+        }
+    }
+}
+
+pub(crate) fn get_last_error() -> Option<String> {
+    match (get_ffi_last_error(), take_callback_error()) {
+        (Some(ffi_error), Some(callback_error)) => Some(format!(
+            "{}; config server callback error: {}",
+            ffi_error, callback_error
+        )),
+        (Some(ffi_error), None) => Some(ffi_error),
+        (None, Some(callback_error)) => Some(callback_error),
+        (None, None) => None,
+    }
+}
+
+pub(crate) fn throw_exception(env: &mut JNIEnv, message: &str) {
+    let _ = env.throw_new("java/lang/RuntimeException", message);
+}
+
+pub(crate) fn get_last_error_jni(env: JNIEnv, _class: JClass) -> jstring {
+    match get_last_error() {
+        Some(error) => match env.new_string(&error) {
+            Ok(jstr) => jstr.into_raw(),
+            Err(_) => ptr::null_mut(),
+        },
+        None => ptr::null_mut(),
+    }
+}

easytier-contrib/easytier-android-jni/src/lib.rs

@@ -1,319 +1,203 @@
-use easytier::proto::api::manage::{NetworkInstanceRunningInfo, NetworkInstanceRunningInfoMap};
+//! JNI facade for Android callers of EasyTier.
+//!
+//! This file intentionally lists every Java-visible native method exported by
+//! `libeasytier_android_jni.so`. The implementation details live in sibling
+//! modules so this facade stays readable as an API map.
+//!
+//! Network management APIs:
+//! - `setTunFd(instanceName, fd)`: attach an Android TUN fd to an instance.
+//! - `parseConfig(config)`: validate TOML config text.
+//! - `runNetworkInstance(config)`: start a local network instance.
+//! - `retainNetworkInstance(instanceNames)`: retain named instances and stop the rest.
+//! - `collectNetworkInfos()`: return running instance info as a JSON string.
+//!
+//! Config server client APIs:
+//! - `startConfigServerClient(url, hostname, machineId, secureMode, callback)`:
+//!   start the managed remote config client.
+//! - `stopConfigServerClient()`: stop the managed client and release its Java callback.
+//! - `isConfigServerClientConnected()`: return whether the managed client is connected.
+//!
+//! Error API:
+//! - `getLastError()`: return the latest FFI/JNI error string for the calling thread.
+
+mod callback;
+mod config_server_api;
+mod error;
+mod logger;
+mod network_api;
+mod strings;
+
 use jni::JNIEnv;
-use jni::objects::{JClass, JObjectArray, JString};
-use jni::sys::{jint, jstring};
-use once_cell::sync::Lazy;
-use std::ffi::{CStr, CString};
-use std::ptr;
+use jni::objects::{JClass, JObject, JObjectArray, JString};
+use jni::sys::{jboolean, jint, jstring};
 
-// 定义 KeyValuePair 结构体
-#[repr(C)]
-#[derive(Clone, Copy)]
-pub struct KeyValuePair {
-    pub key: *const std::ffi::c_char,
-    pub value: *const std::ffi::c_char,
-}
-
-// 声明外部 C 函数
-unsafe extern "C" {
-    fn set_tun_fd(inst_name: *const std::ffi::c_char, fd: std::ffi::c_int) -> std::ffi::c_int;
-    fn get_error_msg(out: *mut *const std::ffi::c_char);
-    fn free_string(s: *const std::ffi::c_char);
-    fn parse_config(cfg_str: *const std::ffi::c_char) -> std::ffi::c_int;
-    fn run_network_instance(cfg_str: *const std::ffi::c_char) -> std::ffi::c_int;
-    fn retain_network_instance(
-        inst_names: *const *const std::ffi::c_char,
-        length: usize,
-    ) -> std::ffi::c_int;
-    fn collect_network_infos(infos: *mut KeyValuePair, max_length: usize) -> std::ffi::c_int;
-}
-
-// 初始化 Android 日志
-static LOGGER_INIT: Lazy<()> = Lazy::new(|| {
-    android_logger::init_once(
-        android_logger::Config::default()
-            .with_max_level(log::LevelFilter::Debug)
-            .with_tag("EasyTier-JNI"),
-    );
-});
-
-// 辅助函数：从 Java String 转换为 CString
-fn jstring_to_cstring(env: &mut JNIEnv, jstr: &JString) -> Result<CString, String> {
-    let java_str = env
-        .get_string(jstr)
-        .map_err(|e| format!("Failed to get string: {:?}", e))?;
-    let rust_str = java_str.to_str().map_err(|_| "Invalid UTF-8".to_string())?;
-    CString::new(rust_str).map_err(|_| "String contains null byte".to_string())
-}
-
-// 辅助函数：获取错误消息
-fn get_last_error() -> Option<String> {
-    unsafe {
-        let mut error_ptr: *const std::ffi::c_char = ptr::null();
-        get_error_msg(&mut error_ptr);
-        if error_ptr.is_null() {
-            None
-        } else {
-            let error_cstr = CStr::from_ptr(error_ptr);
-            let error_str = error_cstr.to_string_lossy().into_owned();
-            free_string(error_ptr);
-            Some(error_str)
-        }
-    }
-}
-
-// 辅助函数：抛出 Java 异常
-fn throw_exception(env: &mut JNIEnv, message: &str) {
-    let _ = env.throw_new("java/lang/RuntimeException", message);
-}
-
-/// 设置 TUN 文件描述符
+/// Attach a TUN file descriptor to an EasyTier network instance.
+///
+/// Java signature:
+/// `EasyTierJNI.setTunFd(instanceName: String, fd: Int): Int`
+///
+/// `instanceName` must name an instance known to the shared FFI instance cache.
+/// The `fd` must be a valid Android TUN file descriptor. On failure this
+/// returns `-1` and throws `RuntimeException` with the FFI error message when
+/// one is available.
 #[unsafe(no_mangle)]
 pub extern "system" fn Java_com_easytier_jni_EasyTierJNI_setTunFd(
-    mut env: JNIEnv,
-    _class: JClass,
+    env: JNIEnv,
+    class: JClass,
     inst_name: JString,
     fd: jint,
 ) -> jint {
-    Lazy::force(&LOGGER_INIT);
-
-    let inst_name_cstr = match jstring_to_cstring(&mut env, &inst_name) {
-        Ok(cstr) => cstr,
-        Err(e) => {
-            throw_exception(&mut env, &format!("Invalid instance name: {}", e));
-            return -1;
-        }
-    };
-
-    unsafe {
-        let result = set_tun_fd(inst_name_cstr.as_ptr(), fd);
-        if result != 0
-            && let Some(error) = get_last_error()
-        {
-            throw_exception(&mut env, &error);
-        }
-        result
-    }
+    logger::init();
+    network_api::set_tun_fd_jni(env, class, inst_name, fd)
 }
 
-/// 解析配置
+/// Validate a TOML network config string.
+///
+/// Java signature:
+/// `EasyTierJNI.parseConfig(config: String): Int`
+///
+/// This only validates the config text; it does not start or mutate any
+/// instance. On failure this returns `-1` and throws `RuntimeException`.
 #[unsafe(no_mangle)]
 pub extern "system" fn Java_com_easytier_jni_EasyTierJNI_parseConfig(
-    mut env: JNIEnv,
-    _class: JClass,
+    env: JNIEnv,
+    class: JClass,
     config: JString,
 ) -> jint {
-    Lazy::force(&LOGGER_INIT);
-
-    let config_cstr = match jstring_to_cstring(&mut env, &config) {
-        Ok(cstr) => cstr,
-        Err(e) => {
-            throw_exception(&mut env, &format!("Invalid config string: {}", e));
-            return -1;
-        }
-    };
-
-    unsafe {
-        let result = parse_config(config_cstr.as_ptr());
-        if result != 0
-            && let Some(error) = get_last_error()
-        {
-            throw_exception(&mut env, &error);
-        }
-        result
-    }
+    logger::init();
+    network_api::parse_config_jni(env, class, config)
 }
 
-/// 运行网络实例
+/// Start one local EasyTier network instance from TOML config text.
+///
+/// Java signature:
+/// `EasyTierJNI.runNetworkInstance(config: String): Int`
+///
+/// The instance name in the config must be unique in the FFI instance cache.
+/// On failure this returns `-1` and throws `RuntimeException`.
 #[unsafe(no_mangle)]
 pub extern "system" fn Java_com_easytier_jni_EasyTierJNI_runNetworkInstance(
-    mut env: JNIEnv,
-    _class: JClass,
+    env: JNIEnv,
+    class: JClass,
     config: JString,
 ) -> jint {
-    Lazy::force(&LOGGER_INIT);
-
-    let config_cstr = match jstring_to_cstring(&mut env, &config) {
-        Ok(cstr) => cstr,
-        Err(e) => {
-            throw_exception(&mut env, &format!("Invalid config string: {}", e));
-            return -1;
-        }
-    };
-
-    unsafe {
-        let result = run_network_instance(config_cstr.as_ptr());
-        if result != 0
-            && let Some(error) = get_last_error()
-        {
-            throw_exception(&mut env, &error);
-        }
-        result
-    }
+    logger::init();
+    network_api::run_network_instance_jni(env, class, config)
 }
 
-/// 保持网络实例
+/// Retain the named network instances and stop all other instances.
+///
+/// Java signature:
+/// `EasyTierJNI.retainNetworkInstance(instanceNames: Array<String>?): Int`
+///
+/// Passing `null` or an empty array stops all instances. Null elements inside a
+/// non-empty array are skipped. On failure this returns `-1` and throws
+/// `RuntimeException`.
 #[unsafe(no_mangle)]
 pub extern "system" fn Java_com_easytier_jni_EasyTierJNI_retainNetworkInstance(
-    mut env: JNIEnv,
-    _class: JClass,
+    env: JNIEnv,
+    class: JClass,
     instance_names: JObjectArray,
 ) -> jint {
-    Lazy::force(&LOGGER_INIT);
-
-    // 处理 null 数组的情况
-    if instance_names.is_null() {
-        unsafe {
-            let result = retain_network_instance(ptr::null(), 0);
-            if result != 0
-                && let Some(error) = get_last_error()
-            {
-                throw_exception(&mut env, &error);
-            }
-            return result;
-        }
-    }
-
-    // 获取数组长度
-    let array_length = match env.get_array_length(&instance_names) {
-        Ok(len) => len as usize,
-        Err(e) => {
-            throw_exception(&mut env, &format!("Failed to get array length: {:?}", e));
-            return -1;
-        }
-    };
-
-    // 如果数组为空，停止所有实例
-    if array_length == 0 {
-        unsafe {
-            let result = retain_network_instance(ptr::null(), 0);
-            if result != 0
-                && let Some(error) = get_last_error()
-            {
-                throw_exception(&mut env, &error);
-            }
-            return result;
-        }
-    }
-
-    // 转换 Java 字符串数组为 C 字符串数组
-    let mut c_strings = Vec::with_capacity(array_length);
-    let mut c_string_ptrs = Vec::with_capacity(array_length);
-
-    for i in 0..array_length {
-        let java_string = match env.get_object_array_element(&instance_names, i as i32) {
-            Ok(obj) => obj,
-            Err(e) => {
-                throw_exception(
-                    &mut env,
-                    &format!("Failed to get array element {}: {:?}", i, e),
-                );
-                return -1;
-            }
-        };
-
-        if java_string.is_null() {
-            continue; // 跳过 null 元素
-        }
-
-        let jstring = JString::from(java_string);
-        let c_string = match jstring_to_cstring(&mut env, &jstring) {
-            Ok(cstr) => cstr,
-            Err(e) => {
-                throw_exception(
-                    &mut env,
-                    &format!("Invalid instance name at index {}: {}", i, e),
-                );
-                return -1;
-            }
-        };
-
-        c_string_ptrs.push(c_string.as_ptr());
-        c_strings.push(c_string); // 保持 CString 的所有权
-    }
-
-    unsafe {
-        let result = retain_network_instance(c_string_ptrs.as_ptr(), c_string_ptrs.len());
-        if result != 0
-            && let Some(error) = get_last_error()
-        {
-            throw_exception(&mut env, &error);
-        }
-        result
-    }
+    logger::init();
+    network_api::retain_network_instance_jni(env, class, instance_names)
 }
 
-/// 收集网络信息
+/// Collect running network instance information.
+///
+/// Java signature:
+/// `EasyTierJNI.collectNetworkInfos(maxLength: Int): String?`
+///
+/// Returns a JSON string containing `NetworkInstanceRunningInfoMap`, or null if
+/// collection fails. `maxLength` limits how many FFI entries are collected. On
+/// failure this throws `RuntimeException` when an error message is available.
 #[unsafe(no_mangle)]
 pub extern "system" fn Java_com_easytier_jni_EasyTierJNI_collectNetworkInfos(
-    mut env: JNIEnv,
-    _class: JClass,
+    env: JNIEnv,
+    class: JClass,
+    max_length: jint,
 ) -> jstring {
-    Lazy::force(&LOGGER_INIT);
-
-    const MAX_INFOS: usize = 100;
-    let mut infos = vec![
-        KeyValuePair {
-            key: ptr::null(),
-            value: ptr::null(),
-        };
-        MAX_INFOS
-    ];
-
-    unsafe {
-        let count = collect_network_infos(infos.as_mut_ptr(), MAX_INFOS);
-        if count < 0 {
-            if let Some(error) = get_last_error() {
-                throw_exception(&mut env, &error);
-            }
-            return ptr::null_mut();
-        }
-
-        let mut ret = NetworkInstanceRunningInfoMap::default();
-
-        // 使用 serde_json 构建 JSON
-        for info in infos.iter().take(count as usize) {
-            let key_ptr = info.key;
-            let val_ptr = info.value;
-            if key_ptr.is_null() || val_ptr.is_null() {
-                break;
-            }
-
-            let key = CStr::from_ptr(key_ptr).to_string_lossy();
-            let val = CStr::from_ptr(val_ptr).to_string_lossy();
-            let value = match serde_json::from_str::<NetworkInstanceRunningInfo>(val.as_ref()) {
-                Ok(v) => v,
-                Err(_) => {
-                    throw_exception(&mut env, "Failed to parse JSON");
-                    continue;
-                }
-            };
-            ret.map.insert(key.to_string(), value);
-        }
-
-        let json_str = serde_json::to_string(&ret).unwrap_or_else(|_| "{}".to_string());
-
-        match env.new_string(&json_str) {
-            Ok(jstr) => jstr.into_raw(),
-            Err(_) => {
-                throw_exception(&mut env, "Failed to create JSON string");
-                ptr::null_mut()
-            }
-        }
-    }
+    logger::init();
+    network_api::collect_network_infos_jni(env, class, max_length)
 }
 
-/// 获取最后的错误信息
+/// Return the latest FFI/JNI error string for the calling thread.
+///
+/// Java signature:
+/// `EasyTierJNI.getLastError(): String?`
+///
+/// This combines the FFI thread-local error with any pending config-server Java
+/// callback error. It returns null when no error is available.
 #[unsafe(no_mangle)]
 pub extern "system" fn Java_com_easytier_jni_EasyTierJNI_getLastError(
     env: JNIEnv,
-    _class: JClass,
+    class: JClass,
 ) -> jstring {
-    match get_last_error() {
-        Some(error) => match env.new_string(&error) {
-            Ok(jstr) => jstr.into_raw(),
-            Err(_) => ptr::null_mut(),
-        },
-        None => ptr::null_mut(),
-    }
+    error::get_last_error_jni(env, class)
+}
+
+/// Start the managed config-server client.
+///
+/// Java signature:
+/// `EasyTierJNI.startConfigServerClient(url, hostname, machineId, secureMode, callback): Int`
+///
+/// JNI only converts Java values and keeps the Java callback alive. The FFI
+/// layer owns singleton lifecycle, config-server/data-plane mutual exclusion,
+/// remote instance tracking, and callback event timing. If `callback` is
+/// non-null, each remote apply/delete event is delivered to
+/// `ConfigServerEventCallback.onEvent(eventJson)`.
+///
+/// On failure this returns `-1` and throws `RuntimeException`.
+#[unsafe(no_mangle)]
+pub extern "system" fn Java_com_easytier_jni_EasyTierJNI_startConfigServerClient(
+    mut env: JNIEnv,
+    _class: JClass,
+    config_server_url: JString,
+    hostname: JString,
+    machine_id: JString,
+    secure_mode: jboolean,
+    callback: JObject,
+) -> jint {
+    logger::init();
+    config_server_api::start_config_server_client_jni(
+        &mut env,
+        config_server_url,
+        hostname,
+        machine_id,
+        secure_mode,
+        callback,
+    )
+}
+
+/// Stop the managed config-server client.
+///
+/// Java signature:
+/// `EasyTierJNI.stopConfigServerClient(): Int`
+///
+/// The FFI layer performs the actual stop and managed instance cleanup. JNI
+/// releases the Java callback reference after FFI stop succeeds. On failure
+/// this returns `-1` and throws `RuntimeException`.
+#[unsafe(no_mangle)]
+pub extern "system" fn Java_com_easytier_jni_EasyTierJNI_stopConfigServerClient(
+    env: JNIEnv,
+    class: JClass,
+) -> jint {
+    logger::init();
+    config_server_api::stop_config_server_client_jni(env, class)
+}
+
+/// Report whether the managed config-server client is connected.
+///
+/// Java signature:
+/// `EasyTierJNI.isConfigServerClientConnected(): Boolean`
+///
+/// Returns `JNI_TRUE` only when the FFI config-server client exists and reports
+/// connected.
+#[unsafe(no_mangle)]
+pub extern "system" fn Java_com_easytier_jni_EasyTierJNI_isConfigServerClientConnected(
+    env: JNIEnv,
+    class: JClass,
+) -> jboolean {
+    logger::init();
+    config_server_api::is_config_server_client_connected_jni(env, class)
 }

easytier-contrib/easytier-android-jni/src/logger.rs

@@ -0,0 +1,13 @@
+use once_cell::sync::Lazy;
+
+static LOGGER_INIT: Lazy<()> = Lazy::new(|| {
+    android_logger::init_once(
+        android_logger::Config::default()
+            .with_max_level(log::LevelFilter::Debug)
+            .with_tag("EasyTier-JNI"),
+    );
+});
+
+pub(crate) fn init() {
+    Lazy::force(&LOGGER_INIT);
+}

easytier-contrib/easytier-android-jni/src/network_api.rs

@@ -0,0 +1,210 @@
+use std::{ffi::CStr, ptr};
+
+use easytier::proto::api::manage::{NetworkInstanceRunningInfo, NetworkInstanceRunningInfoMap};
+use easytier_ffi::{
+    KeyValuePair, collect_network_infos, parse_config, retain_network_instance,
+    run_network_instance, set_tun_fd,
+};
+use jni::JNIEnv;
+use jni::objects::{JClass, JObjectArray, JString};
+use jni::sys::{jint, jstring};
+
+use crate::{
+    error::{get_last_error, throw_exception},
+    strings::jstring_to_cstring,
+};
+
+pub(crate) fn set_tun_fd_jni(
+    mut env: JNIEnv,
+    _class: JClass,
+    inst_name: JString,
+    fd: jint,
+) -> jint {
+    let inst_name_cstr = match jstring_to_cstring(&mut env, &inst_name) {
+        Ok(cstr) => cstr,
+        Err(e) => {
+            throw_exception(&mut env, &format!("Invalid instance name: {}", e));
+            return -1;
+        }
+    };
+    unsafe {
+        let result = set_tun_fd(inst_name_cstr.as_ptr(), fd);
+        if result != 0
+            && let Some(error) = get_last_error()
+        {
+            throw_exception(&mut env, &error);
+        }
+        result
+    }
+}
+
+pub(crate) fn parse_config_jni(mut env: JNIEnv, _class: JClass, config: JString) -> jint {
+    let config_cstr = match jstring_to_cstring(&mut env, &config) {
+        Ok(cstr) => cstr,
+        Err(e) => {
+            throw_exception(&mut env, &format!("Invalid config string: {}", e));
+            return -1;
+        }
+    };
+    unsafe {
+        let result = parse_config(config_cstr.as_ptr());
+        if result != 0
+            && let Some(error) = get_last_error()
+        {
+            throw_exception(&mut env, &error);
+        }
+        result
+    }
+}
+
+pub(crate) fn run_network_instance_jni(mut env: JNIEnv, _class: JClass, config: JString) -> jint {
+    let config_cstr = match jstring_to_cstring(&mut env, &config) {
+        Ok(cstr) => cstr,
+        Err(e) => {
+            throw_exception(&mut env, &format!("Invalid config string: {}", e));
+            return -1;
+        }
+    };
+    unsafe {
+        let result = run_network_instance(config_cstr.as_ptr());
+        if result != 0
+            && let Some(error) = get_last_error()
+        {
+            throw_exception(&mut env, &error);
+        }
+        result
+    }
+}
+
+pub(crate) fn retain_network_instance_jni(
+    mut env: JNIEnv,
+    _class: JClass,
+    instance_names: JObjectArray,
+) -> jint {
+    if instance_names.is_null() {
+        return retain_all(&mut env);
+    }
+
+    let array_length = match env.get_array_length(&instance_names) {
+        Ok(len) => len as usize,
+        Err(e) => {
+            throw_exception(&mut env, &format!("Failed to get array length: {:?}", e));
+            return -1;
+        }
+    };
+
+    if array_length == 0 {
+        return retain_all(&mut env);
+    }
+
+    let mut c_strings = Vec::with_capacity(array_length);
+    let mut c_string_ptrs = Vec::with_capacity(array_length);
+
+    for i in 0..array_length {
+        let java_string = match env.get_object_array_element(&instance_names, i as i32) {
+            Ok(obj) => obj,
+            Err(e) => {
+                throw_exception(
+                    &mut env,
+                    &format!("Failed to get array element {}: {:?}", i, e),
+                );
+                return -1;
+            }
+        };
+
+        if java_string.is_null() {
+            continue;
+        }
+
+        let jstring = JString::from(java_string);
+        let c_string = match jstring_to_cstring(&mut env, &jstring) {
+            Ok(cstr) => cstr,
+            Err(e) => {
+                throw_exception(
+                    &mut env,
+                    &format!("Invalid instance name at index {}: {}", i, e),
+                );
+                return -1;
+            }
+        };
+
+        c_string_ptrs.push(c_string.as_ptr());
+        c_strings.push(c_string);
+    }
+
+    unsafe {
+        let result = retain_network_instance(c_string_ptrs.as_ptr(), c_string_ptrs.len());
+        if result != 0
+            && let Some(error) = get_last_error()
+        {
+            throw_exception(&mut env, &error);
+        }
+        result
+    }
+}
+
+fn retain_all(env: &mut JNIEnv) -> jint {
+    unsafe {
+        let result = retain_network_instance(ptr::null(), 0);
+        if result != 0
+            && let Some(error) = get_last_error()
+        {
+            throw_exception(env, &error);
+        }
+        result
+    }
+}
+
+pub(crate) fn collect_network_infos_jni(
+    mut env: JNIEnv,
+    _class: JClass,
+    max_length: jint,
+) -> jstring {
+    let max_length = max_length.max(0) as usize;
+    let mut infos = vec![
+        KeyValuePair {
+            key: ptr::null(),
+            value: ptr::null(),
+        };
+        max_length
+    ];
+
+    unsafe {
+        let count = collect_network_infos(infos.as_mut_ptr(), max_length);
+        if count < 0 {
+            if let Some(error) = get_last_error() {
+                throw_exception(&mut env, &error);
+            }
+            return ptr::null_mut();
+        }
+
+        let mut ret = NetworkInstanceRunningInfoMap::default();
+        for info in infos.iter().take(count as usize) {
+            let key_ptr = info.key;
+            let val_ptr = info.value;
+            if key_ptr.is_null() || val_ptr.is_null() {
+                break;
+            }
+
+            let key = CStr::from_ptr(key_ptr).to_string_lossy();
+            let val = CStr::from_ptr(val_ptr).to_string_lossy();
+            let value = match serde_json::from_str::<NetworkInstanceRunningInfo>(val.as_ref()) {
+                Ok(v) => v,
+                Err(_) => {
+                    throw_exception(&mut env, "Failed to parse JSON");
+                    continue;
+                }
+            };
+            ret.map.insert(key.to_string(), value);
+        }
+
+        let json_str = serde_json::to_string(&ret).unwrap_or_else(|_| "{}".to_string());
+        match env.new_string(&json_str) {
+            Ok(jstr) => jstr.into_raw(),
+            Err(_) => {
+                throw_exception(&mut env, "Failed to create JSON string");
+                ptr::null_mut()
+            }
+        }
+    }
+}

easytier-contrib/easytier-android-jni/src/strings.rs

@@ -0,0 +1,23 @@
+use std::ffi::CString;
+
+use jni::JNIEnv;
+use jni::objects::JString;
+
+pub(crate) fn jstring_to_cstring(env: &mut JNIEnv, jstr: &JString) -> Result<CString, String> {
+    let java_str = env
+        .get_string(jstr)
+        .map_err(|e| format!("Failed to get string: {:?}", e))?;
+    let rust_str = java_str.to_str().map_err(|_| "Invalid UTF-8".to_string())?;
+    CString::new(rust_str).map_err(|_| "String contains null byte".to_string())
+}
+
+pub(crate) fn optional_jstring_to_cstring(
+    env: &mut JNIEnv,
+    jstr: &JString,
+) -> Result<Option<CString>, String> {
+    if jstr.is_null() {
+        return Ok(None);
+    }
+
+    jstring_to_cstring(env, jstr).map(Some)
+}

easytier-contrib/easytier-ffi/Cargo.toml

@@ -4,10 +4,11 @@ version = "0.1.0"
 edition.workspace = true
 
 [lib]
-crate-type = ["cdylib"]
+crate-type = ["cdylib", "rlib"]
 
 [features]
-default = ["ffi-dataplane"]
+default = ["c-abi", "ffi-dataplane"]
+c-abi = []
 ffi-dataplane = ["easytier/ffi-dataplane"]
 
 [dependencies]
@@ -15,9 +16,13 @@ easytier = { path = "../../easytier" }
 
 once_cell = "1.18.0"
 dashmap = "6.0"
+tokio = { version = "1", features = ["rt-multi-thread", "io-util", "time", "sync", "macros"] }
+async-trait = "0.1"
+log = "0.4"
+percent-encoding = "2.3"
+url = "2"
 
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1"
 uuid = "1.17.0"
-tokio = { version = "1", features = ["rt-multi-thread", "io-util", "time", "sync", "macros"] }
 tokio-util = "0.7"

easytier-contrib/easytier-ffi/examples/example_ffi_call.c

@@ -0,0 +1,100 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <unistd.h> // for sleep
+
+// FFI struct and function declarations
+typedef struct {
+    const char* key;
+    const char* value;
+} KeyValuePair;
+
+typedef void (*config_server_event_callback)(
+    const char* event_json,
+    void* user_data
+);
+
+extern int parse_config(const char* cfg_str);
+extern int run_network_instance(const char* cfg_str);
+extern void get_error_msg(const char** out);
+extern void free_string(const char* s);
+extern int collect_network_infos(KeyValuePair* infos, size_t max_length);
+extern int start_config_server_client(
+    const char* config_server_url,
+    const char* hostname,
+    const char* machine_id,
+    bool secure_mode,
+    config_server_event_callback callback,
+    void* user_data
+);
+extern int stop_config_server_client(void);
+extern int is_config_server_client_connected(void);
+
+static void on_config_server_event(const char* event_json, void* user_data) {
+    (void)user_data;
+    printf("config server event: %s\n", event_json);
+}
+
+int main() {
+    const char* config = "inst_name = \"test\"\nnetwork = \"test_network\"\n";
+    int ret;
+
+    // 调用 parse_config
+    ret = parse_config(config);
+    if (ret != 0) {
+        const char* err = NULL;
+        get_error_msg(&err);
+        if (err) {
+            printf("parse_config error: %s\n", err);
+            free_string(err);
+        }
+        return 1;
+    }
+    printf("parse_config success\n");
+
+    // 调用 run_network_instance
+    ret = run_network_instance(config);
+    if (ret != 0) {
+        const char* err = NULL;
+        get_error_msg(&err);
+        if (err) {
+            printf("run_network_instance error: %s\n", err);
+            free_string(err);
+        }
+        return 1;
+    }
+    printf("run_network_instance success\n");
+
+    // 周期性调用 collect_network_infos 并打印
+    const size_t max_infos = 8;
+    KeyValuePair* infos = (KeyValuePair*)malloc(sizeof(KeyValuePair) * max_infos);
+    if (!infos) {
+        fprintf(stderr, "malloc failed\n");
+        return 1;
+    }
+
+    for (int i = 0; i < 5; ++i) { // 循环5次作为示例
+        memset(infos, 0, sizeof(KeyValuePair) * max_infos);
+        int count = collect_network_infos(infos, max_infos);
+        if (count < 0) {
+            const char* err = NULL;
+            get_error_msg(&err);
+            if (err) {
+                printf("collect_network_infos error: %s\n", err);
+                free_string(err);
+            }
+            break;
+        }
+        printf("collect_network_infos: %d instance(s)\n", count);
+        for (int j = 0; j < count; ++j) {
+            printf("  [%d] key: %s\n      value: %s\n", j, infos[j].key, infos[j].value);
+            free_string(infos[j].key);
+            free_string(infos[j].value);
+        }
+        sleep(1);
+    }
+    free(infos);
+
+    return 0;
+}

easytier-contrib/easytier-ffi/src/config_server.rs

@@ -0,0 +1,565 @@
+use std::{
+    cell::Cell,
+    collections::HashSet,
+    ffi::{CString, c_char, c_int, c_void},
+    sync::{
+        Arc, Mutex,
+        atomic::{AtomicBool, Ordering},
+    },
+};
+
+use easytier::{
+    common::{
+        MachineIdOptions,
+        config::{ConfigLoader as _, TomlConfigLoader},
+    },
+    tunnel::TunnelScheme,
+    web_client::{WebClient, WebClientHooks, run_web_client},
+};
+use uuid::Uuid;
+
+use crate::{
+    data_plane::remove_data_plane_handles_by_instance_ids,
+    error::set_error_msg,
+    state::{
+        ASYNC_RUNTIME, INSTANCE_MANAGER, INSTANCE_MUTATION_LOCK, INSTANCE_NAME_ID_MAP,
+        lock_remote_instance_mutation, remove_instance_name_ids,
+    },
+    strings::{c_str_to_string, optional_c_str_to_string},
+    types::ConfigServerEventCallback,
+};
+
+thread_local! {
+    static IN_CONFIG_SERVER_CALLBACK: Cell<bool> = const { Cell::new(false) };
+}
+
+static CONFIG_SERVER_CLIENT: once_cell::sync::Lazy<Mutex<Option<ManagedConfigServerClient>>> =
+    once_cell::sync::Lazy::new(|| Mutex::new(None));
+static CONFIG_SERVER_CLIENT_ACTIVE: once_cell::sync::Lazy<AtomicBool> =
+    once_cell::sync::Lazy::new(|| AtomicBool::new(false));
+static CONFIG_SERVER_CLIENT_STOPPING: once_cell::sync::Lazy<AtomicBool> =
+    once_cell::sync::Lazy::new(|| AtomicBool::new(false));
+static LAST_CONFIG_SERVER_CALLBACK_ERROR: once_cell::sync::Lazy<Mutex<Option<String>>> =
+    once_cell::sync::Lazy::new(|| Mutex::new(None));
+
+pub(crate) struct ConfigServerCallbackScope;
+
+impl ConfigServerCallbackScope {
+    pub(crate) fn enter() -> Self {
+        IN_CONFIG_SERVER_CALLBACK.with(|in_callback| in_callback.set(true));
+        Self
+    }
+}
+
+impl Drop for ConfigServerCallbackScope {
+    fn drop(&mut self) {
+        IN_CONFIG_SERVER_CALLBACK.with(|in_callback| in_callback.set(false));
+    }
+}
+
+pub fn in_config_server_callback() -> bool {
+    IN_CONFIG_SERVER_CALLBACK.with(Cell::get)
+}
+
+fn config_server_machine_id_options(machine_id: String) -> MachineIdOptions {
+    MachineIdOptions {
+        explicit_machine_id: Some(machine_id),
+        state_dir: None,
+    }
+}
+
+pub fn validate_config_server_client_options(
+    config_server_url_s: &str,
+    machine_id: &str,
+) -> Result<(), String> {
+    if machine_id.trim().is_empty() {
+        return Err("machine_id is empty".to_string());
+    }
+
+    let config_server_url = match url::Url::parse(config_server_url_s) {
+        Ok(url) => url,
+        Err(_) => format!(
+            "udp://config-server.easytier.cn:22020/{}",
+            config_server_url_s
+        )
+        .parse()
+        .map_err(|err| format!("failed to parse config server URL: {}", err))?,
+    };
+
+    TunnelScheme::try_from(&config_server_url).map_err(|_| {
+        format!(
+            "unsupported config server scheme: {}",
+            config_server_url.scheme()
+        )
+    })?;
+
+    let token = config_server_url
+        .path_segments()
+        .and_then(|mut segments| segments.next_back())
+        .map(|segment| percent_encoding::percent_decode_str(segment).decode_utf8())
+        .transpose()
+        .map_err(|err| format!("failed to decode config server token: {}", err))?
+        .map(|token| token.to_string())
+        .unwrap_or_default();
+
+    if token.is_empty() {
+        return Err("empty token".to_string());
+    }
+
+    Ok(())
+}
+
+struct ManagedConfigServerClient {
+    client: WebClient,
+    hooks: Arc<ManagedConfigServerClientHooks>,
+}
+
+pub(crate) struct ManagedConfigServerClientHooks {
+    pub(crate) instance_ids: Mutex<HashSet<Uuid>>,
+    callback_delivery: Mutex<()>,
+    stopping: AtomicBool,
+    callback: ConfigServerEventCallback,
+    user_data: usize,
+}
+
+impl ManagedConfigServerClientHooks {
+    pub(crate) fn new(callback: ConfigServerEventCallback, user_data: *mut c_void) -> Self {
+        Self {
+            instance_ids: Mutex::new(HashSet::new()),
+            callback_delivery: Mutex::new(()),
+            stopping: AtomicBool::new(false),
+            callback,
+            user_data: user_data as usize,
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn tracked_instance_ids(&self) -> Vec<Uuid> {
+        self.instance_ids
+            .lock()
+            .map(|guard| guard.iter().copied().collect())
+            .unwrap_or_default()
+    }
+
+    fn remove_tracked_instance_ids(&self, ids: &[Uuid]) -> Result<Vec<Uuid>, String> {
+        let mut guard = self.instance_ids.lock().map_err(|err| err.to_string())?;
+        Ok(ids
+            .iter()
+            .filter_map(|id| guard.remove(id).then_some(*id))
+            .collect())
+    }
+
+    fn validate_instance_name(&self, inst_name: &str, inst_id: Uuid) -> Result<(), String> {
+        if let Some(existing_id) = INSTANCE_NAME_ID_MAP.get(inst_name).map(|id| *id)
+            && existing_id != inst_id
+        {
+            return Err(format!("instance name {} already exists", inst_name));
+        }
+
+        Ok(())
+    }
+
+    fn commit_instance_name(&self, inst_name: String, inst_id: Uuid) -> Result<(), String> {
+        INSTANCE_NAME_ID_MAP.retain(|_, existing_id| *existing_id != inst_id);
+        self.validate_instance_name(&inst_name, inst_id)?;
+        INSTANCE_NAME_ID_MAP.insert(inst_name, inst_id);
+        Ok(())
+    }
+
+    pub(crate) fn start_stopping(&self) -> Vec<Uuid> {
+        let _delivery_guard = if in_config_server_callback() {
+            None
+        } else {
+            self.callback_delivery.lock().ok()
+        };
+        let mut guard = match self.instance_ids.lock() {
+            Ok(guard) => guard,
+            Err(_) => return Vec::new(),
+        };
+        self.stopping.store(true, Ordering::Release);
+        guard.drain().collect()
+    }
+
+    pub(crate) fn note_callback_error(&self, error: String) {
+        log::warn!("config server event callback failed: {}", error);
+        if let Ok(mut guard) = LAST_CONFIG_SERVER_CALLBACK_ERROR.lock() {
+            *guard = Some(error);
+        }
+    }
+
+    fn emit_event_with_delivery_locked(
+        &self,
+        event: &str,
+        instance_id: Uuid,
+    ) -> Result<(), String> {
+        if self.stopping.load(Ordering::Acquire) {
+            return Ok(());
+        }
+
+        let Some(callback) = self.callback else {
+            return Ok(());
+        };
+
+        let event_json = serde_json::json!({
+            "event": event,
+            "success": true,
+            "instance_id": instance_id.to_string(),
+            "error": null,
+        })
+        .to_string();
+        let event_json = CString::new(event_json).map_err(|err| err.to_string())?;
+        let _callback_scope = ConfigServerCallbackScope::enter();
+        unsafe {
+            callback(event_json.as_ptr(), self.user_data as *mut c_void);
+        }
+        Ok(())
+    }
+
+    fn emit_event(&self, event: &str, instance_id: Uuid) -> Result<(), String> {
+        let _delivery_guard = self
+            .callback_delivery
+            .lock()
+            .map_err(|err| err.to_string())?;
+        self.emit_event_with_delivery_locked(event, instance_id)
+    }
+
+    fn wait_for_callback_delivery(&self) {
+        if in_config_server_callback() {
+            return;
+        }
+
+        if let Ok(guard) = self.callback_delivery.lock() {
+            drop(guard);
+        }
+    }
+}
+
+#[async_trait::async_trait]
+impl WebClientHooks for ManagedConfigServerClientHooks {
+    fn manages_remote_config_instances(&self) -> bool {
+        true
+    }
+
+    async fn pre_run_network_instance(&self, cfg: &TomlConfigLoader) -> Result<(), String> {
+        if self.stopping.load(Ordering::Acquire) {
+            return Err("config server client is stopping".to_string());
+        }
+
+        let inst_name = cfg.get_inst_name();
+        let inst_id = cfg.get_id();
+
+        self.validate_instance_name(&inst_name, inst_id)
+    }
+
+    async fn post_run_network_instance(&self, id: &Uuid) -> Result<(), String> {
+        let _delivery_guard = self
+            .callback_delivery
+            .lock()
+            .map_err(|err| err.to_string())?;
+        let Some(inst_name) = INSTANCE_MANAGER.get_instance_name(id) else {
+            if !self.stopping.load(Ordering::Acquire) {
+                return Err(format!("instance {} not found after start", id));
+            }
+            return Ok(());
+        };
+
+        {
+            let _mutation_guard = INSTANCE_MUTATION_LOCK
+                .lock()
+                .map_err(|err| err.to_string())?;
+            if INSTANCE_MANAGER.get_instance_name(id).is_none() {
+                if !self.stopping.load(Ordering::Acquire) {
+                    return Err(format!("instance {} not found after start", id));
+                }
+                return Ok(());
+            }
+
+            let should_delete = {
+                let mut guard = self.instance_ids.lock().map_err(|err| err.to_string())?;
+                if self.stopping.load(Ordering::Acquire) {
+                    true
+                } else {
+                    guard.insert(*id);
+                    false
+                }
+            };
+
+            if should_delete {
+                if let Err(err) = INSTANCE_MANAGER.delete_network_instance(vec![*id]) {
+                    return Err(err.to_string());
+                }
+                remove_instance_name_ids(&[*id]);
+                return Ok(());
+            }
+
+            if self.stopping.load(Ordering::Acquire) {
+                self.remove_tracked_instance_ids(&[*id])?;
+                remove_instance_name_ids(&[*id]);
+                return Ok(());
+            }
+
+            if let Err(err) = self.commit_instance_name(inst_name.clone(), *id) {
+                self.remove_tracked_instance_ids(&[*id])?;
+                if let Err(delete_err) = INSTANCE_MANAGER.delete_network_instance(vec![*id]) {
+                    return Err(format!(
+                        "{}; failed to delete duplicate instance: {}",
+                        err, delete_err
+                    ));
+                }
+                return Err(err);
+            }
+
+            if self.stopping.load(Ordering::Acquire) {
+                self.remove_tracked_instance_ids(&[*id])?;
+                remove_instance_name_ids(&[*id]);
+                return Ok(());
+            }
+            if INSTANCE_MANAGER.get_instance_name(id).is_none() {
+                self.remove_tracked_instance_ids(&[*id])?;
+                remove_instance_name_ids(&[*id]);
+                return Err(format!(
+                    "instance {} was removed before post-run completed",
+                    id
+                ));
+            }
+        }
+
+        remove_data_plane_handles_by_instance_ids(&[*id]);
+
+        if let Err(err) = self.emit_event_with_delivery_locked("run_network_instance", *id) {
+            self.note_callback_error(err);
+        }
+        Ok(())
+    }
+
+    async fn post_remove_network_instances(&self, ids: &[Uuid]) -> Result<(), String> {
+        let removed_ids = {
+            let _mutation_guard = INSTANCE_MUTATION_LOCK
+                .lock()
+                .map_err(|err| err.to_string())?;
+            let removed_ids = self.remove_tracked_instance_ids(ids)?;
+            remove_instance_name_ids(ids);
+            remove_data_plane_handles_by_instance_ids(&removed_ids);
+            removed_ids
+        };
+
+        for id in removed_ids {
+            if let Err(err) = self.emit_event("delete_network_instance", id) {
+                self.note_callback_error(err);
+            }
+        }
+        Ok(())
+    }
+}
+
+pub(crate) fn remove_config_server_tracked_instance_ids(ids: &[Uuid]) {
+    if ids.is_empty() {
+        return;
+    }
+
+    if let Ok(guard) = CONFIG_SERVER_CLIENT.lock()
+        && let Some(managed) = guard.as_ref()
+        && let Err(err) = managed.hooks.remove_tracked_instance_ids(ids)
+    {
+        log::warn!("failed to remove config server tracked ids: {}", err);
+    }
+}
+
+pub(crate) fn wait_for_config_server_delivery() {
+    let hooks = CONFIG_SERVER_CLIENT
+        .lock()
+        .ok()
+        .and_then(|guard| guard.as_ref().map(|managed| managed.hooks.clone()));
+    if let Some(hooks) = hooks {
+        hooks.wait_for_callback_delivery();
+    }
+}
+
+pub(crate) fn last_callback_error() -> Option<String> {
+    LAST_CONFIG_SERVER_CALLBACK_ERROR
+        .lock()
+        .ok()
+        .and_then(|guard| guard.clone())
+}
+
+pub(crate) fn clear_last_callback_error() {
+    if let Ok(mut guard) = LAST_CONFIG_SERVER_CALLBACK_ERROR.lock() {
+        *guard = None;
+    }
+}
+
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) fn is_config_server_active_or_stopping() -> bool {
+    CONFIG_SERVER_CLIENT_ACTIVE.load(Ordering::Acquire)
+        || CONFIG_SERVER_CLIENT_STOPPING.load(Ordering::Acquire)
+}
+
+#[cfg(test)]
+pub(crate) fn set_active_for_test(active: bool) {
+    CONFIG_SERVER_CLIENT_ACTIVE.store(active, Ordering::Release);
+}
+
+/// # Safety
+/// Start the config server client.
+///
+/// `config_server_url` must be a valid null-terminated UTF-8 string.
+/// `hostname` may be null; if non-null it must be a valid null-terminated UTF-8 string.
+/// `machine_id` must be a valid null-terminated UTF-8 string.
+/// `event_json` passed to `callback` is valid only during that callback invocation.
+pub(crate) unsafe fn start_config_server_client(
+    config_server_url: *const c_char,
+    hostname: *const c_char,
+    machine_id: *const c_char,
+    secure_mode: bool,
+    callback: ConfigServerEventCallback,
+    user_data: *mut c_void,
+) -> c_int {
+    if in_config_server_callback() {
+        set_error_msg("cannot start config server client from config server callback");
+        return -1;
+    }
+
+    let config_server_url = match unsafe { c_str_to_string(config_server_url, "config_server_url") }
+    {
+        Ok(value) => value,
+        Err(err) => {
+            set_error_msg(&err);
+            return -1;
+        }
+    };
+    let hostname = match unsafe { optional_c_str_to_string(hostname, "hostname") } {
+        Ok(value) => value,
+        Err(err) => {
+            set_error_msg(&err);
+            return -1;
+        }
+    };
+    let machine_id = match unsafe { c_str_to_string(machine_id, "machine_id") } {
+        Err(err) => {
+            set_error_msg(&err);
+            return -1;
+        }
+        Ok(value) => value,
+    };
+    if let Err(err) = validate_config_server_client_options(&config_server_url, &machine_id) {
+        set_error_msg(&err);
+        return -1;
+    }
+
+    let mut guard = match CONFIG_SERVER_CLIENT.lock() {
+        Ok(guard) => guard,
+        Err(err) => {
+            set_error_msg(&format!("failed to lock config server client: {}", err));
+            return -1;
+        }
+    };
+
+    if guard.is_some() {
+        set_error_msg("config server client already exists");
+        return -1;
+    }
+    if CONFIG_SERVER_CLIENT_STOPPING.load(Ordering::Acquire) {
+        set_error_msg("config server client is stopping");
+        return -1;
+    }
+    clear_last_callback_error();
+
+    #[cfg(feature = "ffi-dataplane")]
+    let _data_plane_usage_guard = match crate::data_plane::lock_for_config_server_start() {
+        Ok(guard) => guard,
+        Err(err) => {
+            set_error_msg(&err);
+            return -1;
+        }
+    };
+
+    CONFIG_SERVER_CLIENT_ACTIVE.store(true, Ordering::Release);
+    let hooks = Arc::new(ManagedConfigServerClientHooks::new(callback, user_data));
+    let client = match ASYNC_RUNTIME.block_on(run_web_client(
+        &config_server_url,
+        config_server_machine_id_options(machine_id),
+        hostname,
+        secure_mode,
+        INSTANCE_MANAGER.clone(),
+        Some(hooks.clone()),
+    )) {
+        Ok(client) => client,
+        Err(err) => {
+            CONFIG_SERVER_CLIENT_ACTIVE.store(false, Ordering::Release);
+            set_error_msg(&format!("failed to start config server client: {}", err));
+            return -1;
+        }
+    };
+
+    *guard = Some(ManagedConfigServerClient { client, hooks });
+    0
+}
+
+pub(crate) fn stop_config_server_client() -> c_int {
+    if in_config_server_callback() {
+        set_error_msg("cannot stop config server client from config server callback");
+        return -1;
+    }
+
+    let mut guard = match CONFIG_SERVER_CLIENT.lock() {
+        Ok(guard) => guard,
+        Err(err) => {
+            set_error_msg(&format!("failed to lock config server client: {}", err));
+            return -1;
+        }
+    };
+
+    let Some(managed) = guard.as_ref() else {
+        CONFIG_SERVER_CLIENT_ACTIVE.store(false, Ordering::Release);
+        return 0;
+    };
+    if CONFIG_SERVER_CLIENT_STOPPING.swap(true, Ordering::AcqRel) {
+        set_error_msg("config server client is stopping");
+        return -1;
+    }
+    let hooks = managed.hooks.clone();
+    let managed = guard.take().expect("config server client exists");
+    drop(guard);
+
+    let _remote_mutation_guard = lock_remote_instance_mutation();
+    let tracked_ids = hooks.start_stopping();
+    drop(managed);
+
+    let _mutation_guard = match INSTANCE_MUTATION_LOCK.lock() {
+        Ok(guard) => guard,
+        Err(err) => {
+            hooks.wait_for_callback_delivery();
+            CONFIG_SERVER_CLIENT_ACTIVE.store(false, Ordering::Release);
+            CONFIG_SERVER_CLIENT_STOPPING.store(false, Ordering::Release);
+            set_error_msg(&format!("failed to lock instance mutation: {}", err));
+            return -1;
+        }
+    };
+    let delete_result = INSTANCE_MANAGER.delete_network_instance(tracked_ids.clone());
+    if delete_result.is_ok() {
+        remove_instance_name_ids(&tracked_ids);
+        remove_data_plane_handles_by_instance_ids(&tracked_ids);
+    }
+    drop(_mutation_guard);
+    hooks.wait_for_callback_delivery();
+    CONFIG_SERVER_CLIENT_ACTIVE.store(false, Ordering::Release);
+    CONFIG_SERVER_CLIENT_STOPPING.store(false, Ordering::Release);
+
+    if let Err(err) = delete_result {
+        set_error_msg(&format!(
+            "failed to delete config server instances: {}",
+            err
+        ));
+        return -1;
+    }
+    0
+}
+
+pub(crate) fn is_config_server_client_connected() -> c_int {
+    CONFIG_SERVER_CLIENT
+        .lock()
+        .ok()
+        .and_then(|guard| guard.as_ref().map(|managed| managed.client.is_connected()))
+        .map(i32::from)
+        .unwrap_or(0)
+}

easytier-contrib/easytier-ffi/src/data_plane.rs

@@ -0,0 +1,854 @@
+#[cfg(feature = "ffi-dataplane")]
+use std::{
+    future::Future,
+    net::{IpAddr, SocketAddr},
+    sync::{
+        Arc, RwLock,
+        atomic::{AtomicU64, Ordering},
+    },
+    time::Duration,
+};
+
+#[cfg(feature = "ffi-dataplane")]
+use dashmap::DashMap;
+#[cfg(feature = "ffi-dataplane")]
+use easytier::launcher::{DataPlaneTcpListener, DataPlaneTcpStream, DataPlaneUdpSocket};
+#[cfg(feature = "ffi-dataplane")]
+use tokio::io::{AsyncReadExt, AsyncWriteExt, ReadHalf, WriteHalf};
+#[cfg(feature = "ffi-dataplane")]
+use tokio_util::sync::CancellationToken;
+#[cfg(feature = "ffi-dataplane")]
+use uuid::Uuid;
+
+#[cfg(feature = "ffi-dataplane")]
+use crate::{
+    config_server::{in_config_server_callback, is_config_server_active_or_stopping},
+    error::{free_string, set_error_msg},
+    state::{INSTANCE_MANAGER, INSTANCE_NAME_ID_MAP},
+};
+
+#[cfg(feature = "ffi-dataplane")]
+static NEXT_DATA_PLANE_HANDLE: AtomicU64 = AtomicU64::new(1);
+#[cfg(feature = "ffi-dataplane")]
+static DATA_PLANE_HANDLES: once_cell::sync::Lazy<DashMap<u64, DataPlaneHandle>> =
+    once_cell::sync::Lazy::new(DashMap::new);
+#[cfg(feature = "ffi-dataplane")]
+static DATA_PLANE_USAGE_LOCK: once_cell::sync::Lazy<RwLock<()>> =
+    once_cell::sync::Lazy::new(|| RwLock::new(()));
+
+#[cfg(feature = "ffi-dataplane")]
+struct DataPlaneHandle {
+    instance_id: uuid::Uuid,
+    runtime: tokio::runtime::Handle,
+    // Cancelled by close() to wake any in-flight op on this handle.
+    close_token: CancellationToken,
+    resource: DataPlaneResource,
+}
+
+#[cfg(feature = "ffi-dataplane")]
+struct TcpHalves {
+    read: tokio::sync::Mutex<ReadHalf<DataPlaneTcpStream>>,
+    write: tokio::sync::Mutex<WriteHalf<DataPlaneTcpStream>>,
+}
+
+#[cfg(feature = "ffi-dataplane")]
+enum DataPlaneResource {
+    Tcp(Arc<TcpHalves>),
+    TcpListener(Arc<tokio::sync::Mutex<DataPlaneTcpListener>>),
+    Udp(Arc<DataPlaneUdpSocket>),
+}
+
+// Several helper functions for FFI data plane operations to facilitate logic reuse.
+
+#[cfg(feature = "ffi-dataplane")]
+fn next_handle() -> u64 {
+    NEXT_DATA_PLANE_HANDLE.fetch_add(1, Ordering::Relaxed)
+}
+
+#[cfg(feature = "ffi-dataplane")]
+fn timeout_duration(timeout_ms: u64) -> Duration {
+    Duration::from_millis(timeout_ms)
+}
+
+#[cfg(feature = "ffi-dataplane")]
+unsafe fn cstr_to_string(ptr: *const std::ffi::c_char, name: &str) -> Option<String> {
+    if ptr.is_null() {
+        set_error_msg(&format!("{} is null", name));
+        return None;
+    }
+    Some(
+        unsafe { std::ffi::CStr::from_ptr(ptr) }
+            .to_string_lossy()
+            .into_owned(),
+    )
+}
+
+#[cfg(feature = "ffi-dataplane")]
+fn get_instance_id(inst_name: &str) -> Option<uuid::Uuid> {
+    INSTANCE_NAME_ID_MAP.get(inst_name).map(|id| *id.value())
+}
+
+#[cfg(feature = "ffi-dataplane")]
+fn parse_socket_addr(host: &str, port: u16) -> Option<SocketAddr> {
+    let ip = match host.parse::<IpAddr>() {
+        Ok(ip) => ip,
+        Err(e) => {
+            set_error_msg(&format!("failed to parse ip address: {}", e));
+            return None;
+        }
+    };
+    Some(SocketAddr::new(ip, port))
+}
+
+/// Encode an IP address for FFI return. Returns `*mut c_char` to match
+/// `CString::into_raw`; caller releases it via `free_string`.
+#[cfg(feature = "ffi-dataplane")]
+fn into_ffi_ip_cstring(ip: IpAddr) -> Option<*mut std::ffi::c_char> {
+    match std::ffi::CString::new(ip.to_string()) {
+        Ok(s) => Some(s.into_raw()),
+        Err(e) => {
+            set_error_msg(&format!("failed to encode ip: {}", e));
+            None
+        }
+    }
+}
+
+#[cfg(feature = "ffi-dataplane")]
+fn get_runtime_handle(
+    inst_id: &uuid::Uuid,
+    deadline: std::time::Instant,
+) -> Option<tokio::runtime::Handle> {
+    let remaining = deadline.saturating_duration_since(std::time::Instant::now());
+    let Some(rt) = INSTANCE_MANAGER.data_plane_wait_runtime_handle(inst_id, remaining) else {
+        set_error_msg("instance runtime is not ready");
+        return None;
+    };
+    Some(rt)
+}
+
+#[cfg(feature = "ffi-dataplane")]
+fn insert_tcp_stream_handle(
+    instance_id: uuid::Uuid,
+    runtime: tokio::runtime::Handle,
+    stream: DataPlaneTcpStream,
+) -> u64 {
+    let (rd, wr) = tokio::io::split(stream);
+    let handle = next_handle();
+    DATA_PLANE_HANDLES.insert(
+        handle,
+        DataPlaneHandle {
+            instance_id,
+            runtime,
+            close_token: CancellationToken::new(),
+            resource: DataPlaneResource::Tcp(Arc::new(TcpHalves {
+                read: tokio::sync::Mutex::new(rd),
+                write: tokio::sync::Mutex::new(wr),
+            })),
+        },
+    );
+    handle
+}
+
+#[cfg(feature = "ffi-dataplane")]
+fn get_tcp_stream(
+    handle: u64,
+) -> Option<(Arc<TcpHalves>, tokio::runtime::Handle, CancellationToken)> {
+    let Some(h) = DATA_PLANE_HANDLES.get(&handle) else {
+        set_error_msg("tcp stream handle not found");
+        return None;
+    };
+    match &h.resource {
+        DataPlaneResource::Tcp(halves) => {
+            Some((halves.clone(), h.runtime.clone(), h.close_token.clone()))
+        }
+        DataPlaneResource::TcpListener(_) | DataPlaneResource::Udp(_) => {
+            set_error_msg("handle is not a tcp stream");
+            None
+        }
+    }
+}
+
+#[cfg(feature = "ffi-dataplane")]
+fn get_tcp_listener(
+    handle: u64,
+) -> Option<(
+    Arc<tokio::sync::Mutex<DataPlaneTcpListener>>,
+    tokio::runtime::Handle,
+    CancellationToken,
+    uuid::Uuid,
+)> {
+    let Some(h) = DATA_PLANE_HANDLES.get(&handle) else {
+        set_error_msg("tcp listener handle not found");
+        return None;
+    };
+    match &h.resource {
+        DataPlaneResource::TcpListener(listener) => Some((
+            listener.clone(),
+            h.runtime.clone(),
+            h.close_token.clone(),
+            h.instance_id,
+        )),
+        DataPlaneResource::Tcp(_) | DataPlaneResource::Udp(_) => {
+            set_error_msg("handle is not a tcp listener");
+            None
+        }
+    }
+}
+
+#[cfg(feature = "ffi-dataplane")]
+fn get_udp_socket(
+    handle: u64,
+) -> Option<(
+    Arc<DataPlaneUdpSocket>,
+    tokio::runtime::Handle,
+    CancellationToken,
+)> {
+    let Some(h) = DATA_PLANE_HANDLES.get(&handle) else {
+        set_error_msg("udp socket handle not found");
+        return None;
+    };
+    match &h.resource {
+        DataPlaneResource::Udp(socket) => {
+            Some((socket.clone(), h.runtime.clone(), h.close_token.clone()))
+        }
+        DataPlaneResource::Tcp(_) | DataPlaneResource::TcpListener(_) => {
+            set_error_msg("handle is not a udp socket");
+            None
+        }
+    }
+}
+
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) fn remove_data_plane_handles_by_instance_ids(ids: &[Uuid]) {
+    if ids.is_empty() {
+        return;
+    }
+
+    DATA_PLANE_HANDLES.retain(|_, handle| {
+        if ids.contains(&handle.instance_id) {
+            handle.close_token.cancel();
+            false
+        } else {
+            true
+        }
+    });
+}
+
+#[cfg(not(feature = "ffi-dataplane"))]
+pub(crate) fn remove_data_plane_handles_by_instance_ids(_ids: &[uuid::Uuid]) {}
+
+#[cfg(feature = "ffi-dataplane")]
+fn data_plane_rejected() -> bool {
+    if in_config_server_callback() {
+        set_error_msg("cannot use data plane from config server callback");
+        true
+    } else if is_config_server_active_or_stopping() {
+        set_error_msg("cannot use data plane while config server client is active");
+        true
+    } else {
+        false
+    }
+}
+
+#[cfg(feature = "ffi-dataplane")]
+fn enter_data_plane_operation() -> Option<std::sync::RwLockReadGuard<'static, ()>> {
+    if data_plane_rejected() {
+        return None;
+    }
+
+    let guard = match DATA_PLANE_USAGE_LOCK.read() {
+        Ok(guard) => guard,
+        Err(err) => {
+            set_error_msg(&format!("failed to lock data plane usage: {}", err));
+            return None;
+        }
+    };
+    if data_plane_rejected() {
+        return None;
+    }
+    Some(guard)
+}
+
+/// Run an IO op on the resource's owning runtime, supporting
+/// timeout and cancellation.
+#[cfg(feature = "ffi-dataplane")]
+async fn run_with_cancel<T, F>(
+    close_token: &CancellationToken,
+    timeout_ms: u64,
+    error_prefix: &str,
+    op: F,
+) -> Option<Result<T, std::io::Error>>
+where
+    F: Future<Output = Result<T, std::io::Error>>,
+{
+    tokio::select! {
+        biased;
+        _ = close_token.cancelled() => {
+            set_error_msg(&format!("{}: handle closed", error_prefix));
+            None
+        }
+        res = tokio::time::timeout(timeout_duration(timeout_ms), op) => match res {
+            Ok(r) => Some(r),
+            Err(_) => {
+                set_error_msg(&format!("{} timed out", error_prefix));
+                None
+            }
+        }
+    }
+}
+
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) fn lock_for_config_server_start()
+-> Result<std::sync::RwLockWriteGuard<'static, ()>, String> {
+    let guard = DATA_PLANE_USAGE_LOCK
+        .write()
+        .map_err(|err| format!("failed to lock data plane usage: {}", err))?;
+    if !DATA_PLANE_HANDLES.is_empty() {
+        return Err("cannot start config server client while data plane is in use".to_string());
+    }
+    Ok(guard)
+}
+/// # Safety
+/// Open a TCP stream through an EasyTier instance data plane. Returns 0 on
+/// failure. On success, writes the local socket address chosen for this
+/// connection into `out_local_ip` (a heap-allocated C string the caller must
+/// release via `free_string`) and `out_local_port`. Both out pointers must be
+/// non-null.
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) unsafe fn data_plane_tcp_connect(
+    inst_name: *const std::ffi::c_char,
+    dst_ip: *const std::ffi::c_char,
+    dst_port: std::ffi::c_ushort,
+    timeout_ms: u64,
+    out_local_ip: *mut *const std::ffi::c_char,
+    out_local_port: *mut std::ffi::c_ushort,
+) -> u64 {
+    let _data_plane_usage_guard = match enter_data_plane_operation() {
+        Some(guard) => guard,
+        None => return 0,
+    };
+    if out_local_ip.is_null() || out_local_port.is_null() {
+        set_error_msg("output pointer is null");
+        return 0;
+    }
+    let Some(inst_name) = (unsafe { cstr_to_string(inst_name, "inst_name") }) else {
+        return 0;
+    };
+    let Some(dst_ip) = (unsafe { cstr_to_string(dst_ip, "dst_ip") }) else {
+        return 0;
+    };
+    let Some(inst_id) = get_instance_id(&inst_name) else {
+        set_error_msg("instance not found");
+        return 0;
+    };
+    let Some(dst_addr) = parse_socket_addr(&dst_ip, dst_port) else {
+        return 0;
+    };
+    let deadline = std::time::Instant::now() + timeout_duration(timeout_ms);
+    let Some(runtime) = get_runtime_handle(&inst_id, deadline) else {
+        return 0;
+    };
+
+    let remaining = deadline.saturating_duration_since(std::time::Instant::now());
+    let result =
+        runtime.block_on(INSTANCE_MANAGER.data_plane_tcp_connect(&inst_id, dst_addr, remaining));
+    match result {
+        Ok(stream) => {
+            let local_addr = stream.local_addr();
+            let Some(local_ip) = into_ffi_ip_cstring(local_addr.ip()) else {
+                return 0;
+            };
+            let handle = insert_tcp_stream_handle(inst_id, runtime, stream);
+            unsafe {
+                *out_local_ip = local_ip as *const std::ffi::c_char;
+                *out_local_port = local_addr.port();
+            }
+            handle
+        }
+        Err(e) => {
+            set_error_msg(&format!("failed to connect tcp data plane: {}", e));
+            0
+        }
+    }
+}
+
+/// # Safety
+/// Bind a TCP listener through an EasyTier instance data plane. Returns 0 on
+/// failure. The local address actually bound is written into `out_local_ip` /
+/// `out_local_port`; the caller must release `*out_local_ip` via `free_string`.
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) unsafe fn data_plane_tcp_bind(
+    inst_name: *const std::ffi::c_char,
+    local_port: std::ffi::c_ushort,
+    timeout_ms: u64,
+    out_local_ip: *mut *const std::ffi::c_char,
+    out_local_port: *mut std::ffi::c_ushort,
+) -> u64 {
+    let _data_plane_usage_guard = match enter_data_plane_operation() {
+        Some(guard) => guard,
+        None => return 0,
+    };
+    if out_local_ip.is_null() || out_local_port.is_null() {
+        set_error_msg("output pointer is null");
+        return 0;
+    }
+    let Some(inst_name) = (unsafe { cstr_to_string(inst_name, "inst_name") }) else {
+        return 0;
+    };
+    let Some(inst_id) = get_instance_id(&inst_name) else {
+        set_error_msg("instance not found");
+        return 0;
+    };
+    let deadline = std::time::Instant::now() + timeout_duration(timeout_ms);
+    let Some(runtime) = get_runtime_handle(&inst_id, deadline) else {
+        return 0;
+    };
+
+    let remaining = deadline.saturating_duration_since(std::time::Instant::now());
+    let result =
+        runtime.block_on(INSTANCE_MANAGER.data_plane_tcp_bind(&inst_id, local_port, remaining));
+    match result {
+        Ok(listener) => {
+            let local_addr = listener.local_addr();
+            let Some(local_ip) = into_ffi_ip_cstring(local_addr.ip()) else {
+                return 0;
+            };
+            let handle = next_handle();
+            DATA_PLANE_HANDLES.insert(
+                handle,
+                DataPlaneHandle {
+                    instance_id: inst_id,
+                    runtime,
+                    close_token: CancellationToken::new(),
+                    resource: DataPlaneResource::TcpListener(Arc::new(tokio::sync::Mutex::new(
+                        listener,
+                    ))),
+                },
+            );
+            unsafe {
+                *out_local_ip = local_ip as *const std::ffi::c_char;
+                *out_local_port = local_addr.port();
+            }
+            handle
+        }
+        Err(e) => {
+            set_error_msg(&format!("failed to bind tcp data plane: {}", e));
+            0
+        }
+    }
+}
+
+/// # Safety
+/// Accept one connection from a TCP data-plane listener. Returns a TCP stream
+/// handle, or 0 on failure. Local and peer addresses are written into out
+/// parameters; returned IP strings must be released via `free_string`.
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) unsafe fn data_plane_tcp_accept(
+    handle: u64,
+    timeout_ms: u64,
+    out_local_ip: *mut *const std::ffi::c_char,
+    out_local_port: *mut std::ffi::c_ushort,
+    out_peer_ip: *mut *const std::ffi::c_char,
+    out_peer_port: *mut std::ffi::c_ushort,
+) -> u64 {
+    let _data_plane_usage_guard = match enter_data_plane_operation() {
+        Some(guard) => guard,
+        None => return 0,
+    };
+    if out_local_ip.is_null()
+        || out_local_port.is_null()
+        || out_peer_ip.is_null()
+        || out_peer_port.is_null()
+    {
+        set_error_msg("output pointer is null");
+        return 0;
+    }
+    let Some((listener, runtime, close_token, instance_id)) = get_tcp_listener(handle) else {
+        return 0;
+    };
+
+    let ret = runtime.block_on(async move {
+        let mut listener = listener.lock().await;
+        run_with_cancel(
+            &close_token,
+            timeout_ms,
+            "tcp data plane accept",
+            listener.accept(),
+        )
+        .await
+    });
+
+    match ret {
+        Some(Ok((stream, peer_addr))) => {
+            let local_addr = stream.local_addr();
+            let Some(local_ip) = into_ffi_ip_cstring(local_addr.ip()) else {
+                return 0;
+            };
+            let Some(peer_ip) = into_ffi_ip_cstring(peer_addr.ip()) else {
+                free_string(local_ip);
+                return 0;
+            };
+            let stream_handle = insert_tcp_stream_handle(instance_id, runtime, stream);
+            unsafe {
+                *out_local_ip = local_ip as *const std::ffi::c_char;
+                *out_local_port = local_addr.port();
+                *out_peer_ip = peer_ip as *const std::ffi::c_char;
+                *out_peer_port = peer_addr.port();
+            }
+            stream_handle
+        }
+        Some(Err(e)) => {
+            set_error_msg(&format!("failed to accept tcp data plane: {}", e));
+            0
+        }
+        None => 0,
+    }
+}
+
+/// # Safety
+/// Read from a TCP data-plane stream.
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) unsafe fn data_plane_tcp_read(
+    handle: u64,
+    buf: *mut std::ffi::c_uchar,
+    len: u32,
+    timeout_ms: u64,
+) -> std::ffi::c_int {
+    let _data_plane_usage_guard = match enter_data_plane_operation() {
+        Some(guard) => guard,
+        None => return -1,
+    };
+    if buf.is_null() {
+        set_error_msg("buf is null");
+        return -1;
+    }
+    let Some((halves, runtime, close_token)) = get_tcp_stream(handle) else {
+        return -1;
+    };
+    // Safety: caller-owned buffer outlives this blocking call.
+    let buf = unsafe { std::slice::from_raw_parts_mut(buf, len as usize) };
+    runtime.block_on(async move {
+        let mut rd = halves.read.lock().await;
+        match run_with_cancel(
+            &close_token,
+            timeout_ms,
+            "failed to read tcp data plane",
+            rd.read(buf),
+        )
+        .await
+        {
+            Some(Ok(n)) => n as std::ffi::c_int,
+            Some(Err(e)) => {
+                set_error_msg(&format!("failed to read tcp data plane: {}", e));
+                -1
+            }
+            None => -1,
+        }
+    })
+}
+
+/// # Safety
+/// Write to a TCP data-plane stream.
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) unsafe fn data_plane_tcp_write(
+    handle: u64,
+    buf: *const std::ffi::c_uchar,
+    len: u32,
+    timeout_ms: u64,
+) -> std::ffi::c_int {
+    let _data_plane_usage_guard = match enter_data_plane_operation() {
+        Some(guard) => guard,
+        None => return -1,
+    };
+    if buf.is_null() {
+        set_error_msg("buf is null");
+        return -1;
+    }
+    let Some((halves, runtime, close_token)) = get_tcp_stream(handle) else {
+        return -1;
+    };
+    let total = len as usize;
+    // Safety: caller-owned buffer outlives this blocking call.
+    let buf = unsafe { std::slice::from_raw_parts(buf, total) };
+    runtime.block_on(async move {
+        let mut wr = halves.write.lock().await;
+        // Use `write_all` to honor `net.Conn::Write` semantics on the Go side
+        // (must write everything or return an error); single `write()` can
+        // silently short-write and corrupt streams that the caller assumes are
+        // fully written.
+        match run_with_cancel(
+            &close_token,
+            timeout_ms,
+            "failed to write tcp data plane",
+            wr.write_all(buf),
+        )
+        .await
+        {
+            Some(Ok(())) => total as std::ffi::c_int,
+            Some(Err(e)) => {
+                set_error_msg(&format!("failed to write tcp data plane: {}", e));
+                -1
+            }
+            None => -1,
+        }
+    })
+}
+
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) fn data_plane_tcp_close(handle: u64) -> std::ffi::c_int {
+    let _data_plane_usage_guard = match enter_data_plane_operation() {
+        Some(guard) => guard,
+        None => return -1,
+    };
+    let Some((_, h)) = DATA_PLANE_HANDLES.remove_if(&handle, |_, e| {
+        matches!(e.resource, DataPlaneResource::Tcp(_))
+    }) else {
+        set_error_msg(if DATA_PLANE_HANDLES.contains_key(&handle) {
+            "handle is not a tcp stream"
+        } else {
+            "tcp stream handle not found"
+        });
+        return -1;
+    };
+    h.close_token.cancel();
+    if let DataPlaneResource::Tcp(halves) = h.resource {
+        // Best-effort half-close; if write half is in use, the in-flight call
+        // observes the cancel token and releases the lock shortly after.
+        h.runtime.spawn(async move {
+            if let Ok(mut wr) = halves.write.try_lock() {
+                let _ = wr.shutdown().await;
+            }
+        });
+    }
+    0
+}
+
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) fn data_plane_tcp_listener_close(handle: u64) -> std::ffi::c_int {
+    let _data_plane_usage_guard = match enter_data_plane_operation() {
+        Some(guard) => guard,
+        None => return -1,
+    };
+    let Some((_, h)) = DATA_PLANE_HANDLES.remove_if(&handle, |_, e| {
+        matches!(e.resource, DataPlaneResource::TcpListener(_))
+    }) else {
+        set_error_msg(if DATA_PLANE_HANDLES.contains_key(&handle) {
+            "handle is not a tcp listener"
+        } else {
+            "tcp listener handle not found"
+        });
+        return -1;
+    };
+    h.close_token.cancel();
+    0
+}
+
+/// # Safety
+/// Bind a UDP socket through an EasyTier instance data plane. Returns 0 on
+/// failure. The local address actually bound (which may differ from the
+/// requested port when `local_port == 0`) is written into `out_local_ip` /
+/// `out_local_port`; the caller must release `*out_local_ip` via `free_string`.
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) unsafe fn data_plane_udp_bind(
+    inst_name: *const std::ffi::c_char,
+    local_port: std::ffi::c_ushort,
+    timeout_ms: u64,
+    out_local_ip: *mut *const std::ffi::c_char,
+    out_local_port: *mut std::ffi::c_ushort,
+) -> u64 {
+    let _data_plane_usage_guard = match enter_data_plane_operation() {
+        Some(guard) => guard,
+        None => return 0,
+    };
+    if out_local_ip.is_null() || out_local_port.is_null() {
+        set_error_msg("output pointer is null");
+        return 0;
+    }
+    let Some(inst_name) = (unsafe { cstr_to_string(inst_name, "inst_name") }) else {
+        return 0;
+    };
+    let Some(inst_id) = get_instance_id(&inst_name) else {
+        set_error_msg("instance not found");
+        return 0;
+    };
+    let deadline = std::time::Instant::now() + timeout_duration(timeout_ms);
+    let Some(runtime) = get_runtime_handle(&inst_id, deadline) else {
+        return 0;
+    };
+
+    let remaining = deadline.saturating_duration_since(std::time::Instant::now());
+    let result =
+        runtime.block_on(INSTANCE_MANAGER.data_plane_udp_bind(&inst_id, local_port, remaining));
+    match result {
+        Ok(socket) => {
+            let local_addr = socket.local_addr();
+            let Some(local_ip) = into_ffi_ip_cstring(local_addr.ip()) else {
+                return 0;
+            };
+            let handle = next_handle();
+            DATA_PLANE_HANDLES.insert(
+                handle,
+                DataPlaneHandle {
+                    instance_id: inst_id,
+                    runtime,
+                    close_token: CancellationToken::new(),
+                    resource: DataPlaneResource::Udp(Arc::new(socket)),
+                },
+            );
+            unsafe {
+                *out_local_ip = local_ip as *const std::ffi::c_char;
+                *out_local_port = local_addr.port();
+            }
+            handle
+        }
+        Err(e) => {
+            set_error_msg(&format!("failed to bind udp data plane: {}", e));
+            0
+        }
+    }
+}
+
+/// # Safety
+/// Send a datagram through a UDP data-plane socket.
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) unsafe fn data_plane_udp_send_to(
+    handle: u64,
+    dst_ip: *const std::ffi::c_char,
+    dst_port: std::ffi::c_ushort,
+    buf: *const std::ffi::c_uchar,
+    len: u32,
+    timeout_ms: u64,
+) -> std::ffi::c_int {
+    let _data_plane_usage_guard = match enter_data_plane_operation() {
+        Some(guard) => guard,
+        None => return -1,
+    };
+    if buf.is_null() {
+        set_error_msg("buf is null");
+        return -1;
+    }
+    let Some(dst_ip) = (unsafe { cstr_to_string(dst_ip, "dst_ip") }) else {
+        return -1;
+    };
+    let Some(dst_addr) = parse_socket_addr(&dst_ip, dst_port) else {
+        return -1;
+    };
+    let Some((socket, runtime, close_token)) = get_udp_socket(handle) else {
+        return -1;
+    };
+    let total = len as usize;
+    // Safety: caller-owned buffer outlives this blocking call.
+    let buf = unsafe { std::slice::from_raw_parts(buf, total) };
+    runtime.block_on(async move {
+        match run_with_cancel(
+            &close_token,
+            timeout_ms,
+            "failed to send udp data plane",
+            socket.send_to(buf, dst_addr),
+        )
+        .await
+        {
+            Some(Ok(n)) => n as std::ffi::c_int,
+            Some(Err(e)) => {
+                set_error_msg(&format!("failed to send udp data plane: {}", e));
+                -1
+            }
+            None => -1,
+        }
+    })
+}
+
+/// # Safety
+/// Receive a datagram from a UDP data-plane socket.
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) unsafe fn data_plane_udp_recv_from(
+    handle: u64,
+    buf: *mut std::ffi::c_uchar,
+    len: u32,
+    out_ip: *mut *const std::ffi::c_char,
+    out_port: *mut std::ffi::c_ushort,
+    timeout_ms: u64,
+) -> std::ffi::c_int {
+    let _data_plane_usage_guard = match enter_data_plane_operation() {
+        Some(guard) => guard,
+        None => return -1,
+    };
+    if buf.is_null() || out_ip.is_null() || out_port.is_null() {
+        set_error_msg("output pointer is null");
+        return -1;
+    }
+    let Some((socket, runtime, close_token)) = get_udp_socket(handle) else {
+        return -1;
+    };
+    let total = len as usize;
+    // Safety: caller-owned buffer outlives this blocking call.
+    let buf = unsafe { std::slice::from_raw_parts_mut(buf, total) };
+    let ret = runtime.block_on(run_with_cancel(
+        &close_token,
+        timeout_ms,
+        "udp data plane receive",
+        socket.recv_from(buf),
+    ));
+
+    match ret {
+        Some(Ok((n, addr))) => {
+            // The returned ip pointer must be released by the caller via
+            // `free_string` (which calls `CString::from_raw`, matching
+            // `CString::into_raw` here).
+            let Some(ip_cstr) = into_ffi_ip_cstring(addr.ip()) else {
+                return -1;
+            };
+            unsafe {
+                *out_ip = ip_cstr as *const std::ffi::c_char;
+                *out_port = addr.port() as std::ffi::c_ushort;
+            }
+            n as std::ffi::c_int
+        }
+        Some(Err(e)) => {
+            set_error_msg(&format!("failed to receive udp data plane: {}", e));
+            -1
+        }
+        None => -1,
+    }
+}
+
+#[cfg(feature = "ffi-dataplane")]
+pub(crate) fn data_plane_udp_close(handle: u64) -> std::ffi::c_int {
+    let _data_plane_usage_guard = match enter_data_plane_operation() {
+        Some(guard) => guard,
+        None => return -1,
+    };
+    let Some((_, h)) = DATA_PLANE_HANDLES.remove_if(&handle, |_, e| {
+        matches!(e.resource, DataPlaneResource::Udp(_))
+    }) else {
+        set_error_msg(if DATA_PLANE_HANDLES.contains_key(&handle) {
+            "handle is not a udp socket"
+        } else {
+            "udp socket handle not found"
+        });
+        return -1;
+    };
+    h.close_token.cancel();
+    0
+}
+
+#[cfg(all(test, feature = "ffi-dataplane"))]
+mod tests {
+    use super::*;
+    use std::{sync::mpsc, time::Duration};
+
+    #[test]
+    fn config_server_start_waits_for_data_plane_operation() {
+        let read_guard = DATA_PLANE_USAGE_LOCK.read().unwrap();
+        let (done_tx, done_rx) = mpsc::channel();
+        let waiter = std::thread::spawn(move || {
+            let _write_guard = lock_for_config_server_start().unwrap();
+            done_tx.send(()).unwrap();
+        });
+
+        assert!(done_rx.recv_timeout(Duration::from_millis(100)).is_err());
+        drop(read_guard);
+        done_rx.recv_timeout(Duration::from_secs(5)).unwrap();
+        waiter.join().unwrap();
+    }
+}

easytier-contrib/easytier-ffi/src/error.rs

@@ -0,0 +1,65 @@
+use std::{
+    cell::RefCell,
+    ffi::{CString, c_char},
+};
+
+thread_local! {
+    // # Thread Safety
+    // set_error_msg and get_error_msg must be called on the same thread to
+    // get correct error. And since `Handle::block_on` polls the top-level
+    // future on the calling thread, set_error_msg always runs on the same
+    // thread as the corresponding get_error_msg.
+    static ERROR_MSG: RefCell<Vec<u8>> = const { RefCell::new(Vec::new()) };
+}
+
+pub(crate) fn set_error_msg(msg: &str) {
+    ERROR_MSG.with(|cell| {
+        let mut buf = cell.borrow_mut();
+        buf.clear();
+        buf.extend_from_slice(msg.as_bytes());
+    });
+}
+
+fn thread_local_error_msg() -> Option<String> {
+    ERROR_MSG.with(|cell| {
+        let buf = cell.borrow();
+        if buf.is_empty() {
+            None
+        } else {
+            Some(String::from_utf8_lossy(&buf).into_owned())
+        }
+    })
+}
+
+pub(crate) unsafe fn get_error_msg(out: *mut *const c_char) {
+    let msg = match (
+        thread_local_error_msg(),
+        crate::config_server::last_callback_error(),
+    ) {
+        (Some(error), Some(callback_error)) => Some(format!(
+            "{}; config server callback error: {}",
+            error, callback_error
+        )),
+        (Some(error), None) => Some(error),
+        (None, Some(callback_error)) => {
+            Some(format!("config server callback error: {}", callback_error))
+        }
+        (None, None) => None,
+    };
+    let cstr = msg.and_then(|msg| CString::new(msg).ok());
+    unsafe {
+        *out = match cstr {
+            Some(s) => s.into_raw() as *const c_char,
+            None => std::ptr::null(),
+        };
+    }
+}
+
+pub(crate) fn free_string(s: *const c_char) {
+    if s.is_null() {
+        return;
+    }
+    unsafe {
+        let _ = CString::from_raw(s as *mut c_char);
+    }
+}

easytier-contrib/easytier-ffi/src/instance_api.rs

@@ -0,0 +1,236 @@
+use std::ffi::{c_char, c_int};
+
+use easytier::common::config::{ConfigFileControl, ConfigLoader as _, TomlConfigLoader};
+
+use crate::{
+    config_server::{
+        in_config_server_callback, remove_config_server_tracked_instance_ids,
+        wait_for_config_server_delivery,
+    },
+    data_plane::remove_data_plane_handles_by_instance_ids,
+    error::set_error_msg,
+    state::{
+        INSTANCE_MANAGER, INSTANCE_MUTATION_LOCK, INSTANCE_NAME_ID_MAP, instance_name_exists,
+        lock_remote_instance_mutation,
+    },
+    types::KeyValuePair,
+};
+
+/// # Safety
+/// Set the tun fd
+pub(crate) unsafe fn set_tun_fd(inst_name: *const c_char, fd: c_int) -> c_int {
+    let inst_name = unsafe {
+        assert!(!inst_name.is_null());
+        std::ffi::CStr::from_ptr(inst_name)
+            .to_string_lossy()
+            .into_owned()
+    };
+    if !INSTANCE_NAME_ID_MAP.contains_key(&inst_name) {
+        return -1;
+    }
+
+    let inst_id = *INSTANCE_NAME_ID_MAP
+        .get(&inst_name)
+        .as_ref()
+        .unwrap()
+        .value();
+
+    match INSTANCE_MANAGER.set_tun_fd(&inst_id, fd) {
+        Ok(_) => 0,
+        Err(_) => -1,
+    }
+}
+
+/// # Safety
+/// Parse the config
+pub(crate) unsafe fn parse_config(cfg_str: *const std::ffi::c_char) -> std::ffi::c_int {
+    let cfg_str = unsafe {
+        assert!(!cfg_str.is_null());
+        std::ffi::CStr::from_ptr(cfg_str)
+            .to_string_lossy()
+            .into_owned()
+    };
+
+    if let Err(e) = TomlConfigLoader::new_from_str(&cfg_str) {
+        set_error_msg(&format!("failed to parse config: {:?}", e));
+        return -1;
+    }
+
+    0
+}
+
+/// # Safety
+/// Run the network instance
+pub(crate) unsafe fn run_network_instance(cfg_str: *const std::ffi::c_char) -> std::ffi::c_int {
+    if in_config_server_callback() {
+        set_error_msg("cannot run network instance from config server callback");
+        return -1;
+    }
+
+    let cfg_str = unsafe {
+        assert!(!cfg_str.is_null());
+        std::ffi::CStr::from_ptr(cfg_str)
+            .to_string_lossy()
+            .into_owned()
+    };
+    let cfg = match TomlConfigLoader::new_from_str(&cfg_str) {
+        Ok(cfg) => cfg,
+        Err(e) => {
+            set_error_msg(&format!("failed to parse config: {}", e));
+            return -1;
+        }
+    };
+
+    let inst_name = cfg.get_inst_name();
+
+    wait_for_config_server_delivery();
+    let _remote_mutation_guard = lock_remote_instance_mutation();
+    let _mutation_guard = match INSTANCE_MUTATION_LOCK.lock() {
+        Ok(guard) => guard,
+        Err(err) => {
+            set_error_msg(&format!("failed to lock instance mutation: {}", err));
+            return -1;
+        }
+    };
+
+    if instance_name_exists(&inst_name) {
+        set_error_msg("instance already exists");
+        return -1;
+    }
+
+    let instance_id =
+        match INSTANCE_MANAGER.run_network_instance(cfg, false, ConfigFileControl::STATIC_CONFIG) {
+            Ok(id) => id,
+            Err(e) => {
+                set_error_msg(&format!("failed to start instance: {}", e));
+                return -1;
+            }
+        };
+
+    INSTANCE_NAME_ID_MAP.insert(inst_name, instance_id);
+
+    0
+}
+
+/// # Safety
+/// Retain the network instance
+pub(crate) unsafe fn retain_network_instance(
+    inst_names: *const *const std::ffi::c_char,
+    length: usize,
+) -> std::ffi::c_int {
+    if in_config_server_callback() {
+        set_error_msg("cannot retain network instances from config server callback");
+        return -1;
+    }
+
+    wait_for_config_server_delivery();
+    let _remote_mutation_guard = lock_remote_instance_mutation();
+    let _mutation_guard = match INSTANCE_MUTATION_LOCK.lock() {
+        Ok(guard) => guard,
+        Err(err) => {
+            set_error_msg(&format!("failed to lock instance mutation: {}", err));
+            return -1;
+        }
+    };
+
+    if length == 0 {
+        let removed_ids = INSTANCE_MANAGER.list_network_instance_ids();
+        if let Err(e) = INSTANCE_MANAGER.delete_network_instance(removed_ids.clone()) {
+            set_error_msg(&format!("failed to delete instances: {}", e));
+            return -1;
+        }
+        remove_config_server_tracked_instance_ids(&removed_ids);
+        remove_data_plane_handles_by_instance_ids(&removed_ids);
+        INSTANCE_NAME_ID_MAP.clear();
+        return 0;
+    }
+
+    let inst_names = unsafe {
+        assert!(!inst_names.is_null());
+        std::slice::from_raw_parts(inst_names, length)
+            .iter()
+            .map(|&name| {
+                assert!(!name.is_null());
+                std::ffi::CStr::from_ptr(name)
+                    .to_string_lossy()
+                    .into_owned()
+            })
+            .collect::<Vec<_>>()
+    };
+
+    let removed_ids = INSTANCE_MANAGER
+        .list_network_instance_ids()
+        .into_iter()
+        .filter(|id| {
+            INSTANCE_MANAGER
+                .get_instance_name(id)
+                .is_none_or(|name| !inst_names.contains(&name))
+        })
+        .collect::<Vec<_>>();
+
+    if let Err(e) = INSTANCE_MANAGER.delete_network_instance(removed_ids.clone()) {
+        set_error_msg(&format!("failed to delete instances: {}", e));
+        return -1;
+    }
+
+    remove_config_server_tracked_instance_ids(&removed_ids);
+    remove_data_plane_handles_by_instance_ids(&removed_ids);
+    INSTANCE_NAME_ID_MAP.retain(|k, _| inst_names.contains(k));
+
+    0
+}
+
+/// # Safety
+/// Collect the network infos
+pub(crate) unsafe fn collect_network_infos(
+    infos: *mut KeyValuePair,
+    max_length: usize,
+) -> std::ffi::c_int {
+    if in_config_server_callback() {
+        set_error_msg("cannot collect network infos from config server callback");
+        return -1;
+    }
+
+    if max_length == 0 {
+        return 0;
+    }
+
+    let infos = unsafe {
+        assert!(!infos.is_null());
+        std::slice::from_raw_parts_mut(infos, max_length)
+    };
+
+    let collected_infos = match INSTANCE_MANAGER.collect_network_infos_sync() {
+        Ok(infos) => infos,
+        Err(e) => {
+            set_error_msg(&format!("failed to collect network infos: {}", e));
+            return -1;
+        }
+    };
+
+    let mut index = 0;
+    for (instance_id, value) in collected_infos.iter() {
+        if index >= max_length {
+            break;
+        }
+        let Some(key) = INSTANCE_MANAGER.get_instance_name(instance_id) else {
+            continue;
+        };
+        // convert value to json string
+        let value = match serde_json::to_string(&value) {
+            Ok(value) => value,
+            Err(e) => {
+                set_error_msg(&format!("failed to serialize instance info: {}", e));
+                return -1;
+            }
+        };
+
+        infos[index] = KeyValuePair {
+            key: std::ffi::CString::new(key).unwrap().into_raw(),
+            value: std::ffi::CString::new(value).unwrap().into_raw(),
+        };
+        index += 1;
+    }
+
+    index as std::ffi::c_int
+}

easytier-contrib/easytier-ffi/src/state.rs

@@ -0,0 +1,54 @@
+use std::sync::{Arc, Mutex};
+
+use dashmap::DashMap;
+use easytier::instance_manager::NetworkInstanceManager;
+use tokio::runtime::{Builder, Runtime};
+use uuid::Uuid;
+
+pub(crate) static INSTANCE_NAME_ID_MAP: once_cell::sync::Lazy<DashMap<String, Uuid>> =
+    once_cell::sync::Lazy::new(DashMap::new);
+pub(crate) static INSTANCE_MANAGER: once_cell::sync::Lazy<Arc<NetworkInstanceManager>> =
+    once_cell::sync::Lazy::new(|| Arc::new(NetworkInstanceManager::new()));
+pub(crate) static ASYNC_RUNTIME: once_cell::sync::Lazy<Runtime> =
+    once_cell::sync::Lazy::new(|| {
+        Builder::new_multi_thread()
+            .enable_all()
+            .build()
+            .expect("tokio runtime for easytier-ffi")
+    });
+pub(crate) static INSTANCE_MUTATION_LOCK: once_cell::sync::Lazy<Mutex<()>> =
+    once_cell::sync::Lazy::new(|| Mutex::new(()));
+
+pub(crate) fn remove_instance_name_ids(ids: &[Uuid]) {
+    if ids.is_empty() {
+        return;
+    }
+
+    INSTANCE_NAME_ID_MAP.retain(|_, instance_id| !ids.contains(instance_id));
+}
+
+pub(crate) fn lock_remote_instance_mutation() -> tokio::sync::OwnedMutexGuard<()> {
+    INSTANCE_MANAGER
+        .remote_mutation_lock()
+        .blocking_lock_owned()
+}
+
+pub(crate) fn instance_name_exists(inst_name: &str) -> bool {
+    find_instance_id_by_name(inst_name).is_some()
+}
+
+pub(crate) fn find_instance_id_by_name(inst_name: &str) -> Option<Uuid> {
+    INSTANCE_NAME_ID_MAP
+        .get(inst_name)
+        .map(|id| *id)
+        .or_else(|| {
+            INSTANCE_MANAGER
+                .list_network_instance_ids()
+                .into_iter()
+                .find(|id| {
+                    INSTANCE_MANAGER
+                        .get_instance_name(id)
+                        .is_some_and(|name| name == inst_name)
+                })
+        })
+}

easytier-contrib/easytier-ffi/src/strings.rs

@@ -0,0 +1,23 @@
+use std::ffi::{CStr, c_char};
+
+pub(crate) unsafe fn c_str_to_string(ptr: *const c_char, name: &str) -> Result<String, String> {
+    if ptr.is_null() {
+        return Err(format!("{} is null", name));
+    }
+
+    unsafe { CStr::from_ptr(ptr) }
+        .to_str()
+        .map(|value| value.to_string())
+        .map_err(|err| format!("{} is not valid UTF-8: {}", name, err))
+}
+
+pub(crate) unsafe fn optional_c_str_to_string(
+    ptr: *const c_char,
+    name: &str,
+) -> Result<Option<String>, String> {
+    if ptr.is_null() {
+        return Ok(None);
+    }
+
+    unsafe { c_str_to_string(ptr, name) }.map(Some)
+}

easytier-contrib/easytier-ffi/src/tests.rs

@@ -0,0 +1,477 @@
+use crate::{
+    config_server::{
+        ConfigServerCallbackScope, ManagedConfigServerClientHooks, set_active_for_test,
+    },
+    state::{
+        INSTANCE_MANAGER, INSTANCE_NAME_ID_MAP, find_instance_id_by_name,
+        lock_remote_instance_mutation, remove_instance_name_ids,
+    },
+    *,
+};
+use easytier::{
+    common::config::{ConfigFileControl, ConfigLoader as _, TomlConfigLoader},
+    web_client::WebClientHooks,
+};
+use serde_json::Value;
+use std::{
+    collections::HashSet,
+    ffi::{CStr, CString, c_char, c_void},
+    sync::{Mutex, mpsc},
+    time::Duration,
+};
+use uuid::Uuid;
+
+#[test]
+fn test_parse_config() {
+    let cfg_str = r#"
+            inst_name = "test"
+            network = "test_network"
+        "#;
+    let cstr = std::ffi::CString::new(cfg_str).unwrap();
+    unsafe {
+        assert_eq!(parse_config(cstr.as_ptr()), 0);
+    }
+}
+
+#[test]
+fn test_run_network_instance() {
+    let cfg_str = r#"
+            inst_name = "test"
+            network = "test_network"
+        "#;
+    let cstr = std::ffi::CString::new(cfg_str).unwrap();
+    unsafe {
+        assert_eq!(run_network_instance(cstr.as_ptr()), 0);
+    }
+}
+
+#[test]
+fn get_error_msg_returns_config_server_callback_error() {
+    let hooks = ManagedConfigServerClientHooks::new(None, std::ptr::null_mut());
+    let callback_error = format!("callback delivery failed {}", Uuid::new_v4());
+    crate::config_server::clear_last_callback_error();
+    hooks.note_callback_error(callback_error.clone());
+
+    unsafe {
+        let mut error_ptr: *const c_char = std::ptr::null();
+        get_error_msg(&mut error_ptr);
+        assert!(!error_ptr.is_null());
+        let error_msg = CStr::from_ptr(error_ptr).to_string_lossy().into_owned();
+        free_string(error_ptr);
+        assert!(error_msg.contains(&callback_error));
+    }
+
+    crate::config_server::clear_last_callback_error();
+}
+
+unsafe extern "C" fn record_config_server_event(event_json: *const c_char, user_data: *mut c_void) {
+    let events = unsafe { &*(user_data as *const Mutex<Vec<String>>) };
+    events.lock().unwrap().push(
+        unsafe { CStr::from_ptr(event_json) }
+            .to_string_lossy()
+            .into_owned(),
+    );
+}
+
+#[tokio::test]
+async fn config_server_hooks_emit_run_event() {
+    let events: Mutex<Vec<String>> = Mutex::new(Vec::new());
+    let hooks = ManagedConfigServerClientHooks::new(
+        Some(record_config_server_event),
+        &events as *const _ as *mut c_void,
+    );
+    let instance_id = Uuid::new_v4();
+    let cfg = TomlConfigLoader::default();
+    cfg.set_id(instance_id);
+    let inst_name = format!("test-{}", instance_id);
+    cfg.set_inst_name(inst_name.clone());
+    hooks.pre_run_network_instance(&cfg).await.unwrap();
+    INSTANCE_MANAGER
+        .run_network_instance(cfg, false, ConfigFileControl::STATIC_CONFIG)
+        .unwrap();
+
+    hooks.post_run_network_instance(&instance_id).await.unwrap();
+
+    let duplicate_cfg = TomlConfigLoader::default();
+    duplicate_cfg.set_inst_name(inst_name);
+    duplicate_cfg.set_id(Uuid::new_v4());
+    assert!(
+        hooks
+            .pre_run_network_instance(&duplicate_cfg)
+            .await
+            .is_err()
+    );
+
+    assert_eq!(hooks.tracked_instance_ids(), vec![instance_id]);
+    let events = events.lock().unwrap();
+    assert_eq!(events.len(), 1);
+    let event: Value = serde_json::from_str(&events[0]).unwrap();
+    assert_eq!(event["event"], "run_network_instance");
+    assert_eq!(event["success"], true);
+    assert_eq!(event["instance_id"], instance_id.to_string());
+    assert!(event["error"].is_null());
+    INSTANCE_MANAGER
+        .delete_network_instance(vec![instance_id])
+        .unwrap();
+    remove_instance_name_ids(&[instance_id]);
+}
+
+#[tokio::test]
+async fn config_server_hooks_emit_delete_events_for_tracked_instances() {
+    let events: Mutex<Vec<String>> = Mutex::new(Vec::new());
+    let hooks = ManagedConfigServerClientHooks::new(
+        Some(record_config_server_event),
+        &events as *const _ as *mut c_void,
+    );
+    let instance_id_1 = Uuid::new_v4();
+    let instance_id_2 = Uuid::new_v4();
+    let unknown_instance_id = Uuid::new_v4();
+    for id in [instance_id_1, instance_id_2] {
+        let cfg = TomlConfigLoader::default();
+        cfg.set_id(id);
+        cfg.set_inst_name(format!("test-{}", id));
+        hooks.pre_run_network_instance(&cfg).await.unwrap();
+        INSTANCE_MANAGER
+            .run_network_instance(cfg, false, ConfigFileControl::STATIC_CONFIG)
+            .unwrap();
+    }
+
+    hooks
+        .post_run_network_instance(&instance_id_1)
+        .await
+        .unwrap();
+    hooks
+        .post_run_network_instance(&instance_id_2)
+        .await
+        .unwrap();
+    events.lock().unwrap().clear();
+
+    hooks
+        .post_remove_network_instances(&[instance_id_1, unknown_instance_id, instance_id_2])
+        .await
+        .unwrap();
+
+    assert!(hooks.tracked_instance_ids().is_empty());
+    let events = events.lock().unwrap();
+    assert_eq!(events.len(), 2);
+    let event_ids = events
+        .iter()
+        .map(|event| {
+            let event: Value = serde_json::from_str(event).unwrap();
+            assert_eq!(event["event"], "delete_network_instance");
+            assert_eq!(event["success"], true);
+            assert!(event["error"].is_null());
+            event["instance_id"].as_str().unwrap().to_string()
+        })
+        .collect::<HashSet<_>>();
+    assert_eq!(
+        event_ids,
+        HashSet::from([instance_id_1.to_string(), instance_id_2.to_string()])
+    );
+    INSTANCE_MANAGER
+        .delete_network_instance(vec![instance_id_1, instance_id_2])
+        .unwrap();
+    remove_instance_name_ids(&[instance_id_1, instance_id_2]);
+}
+
+#[tokio::test]
+async fn config_server_hooks_remove_untracked_name_mapping_without_event() {
+    let events: Mutex<Vec<String>> = Mutex::new(Vec::new());
+    let hooks = ManagedConfigServerClientHooks::new(
+        Some(record_config_server_event),
+        &events as *const _ as *mut c_void,
+    );
+    let local_id = Uuid::new_v4();
+    let inst_name = format!("local-{}", local_id);
+    INSTANCE_NAME_ID_MAP.insert(inst_name.clone(), local_id);
+
+    hooks
+        .post_remove_network_instances(&[local_id])
+        .await
+        .unwrap();
+
+    assert!(INSTANCE_NAME_ID_MAP.get(&inst_name).is_none());
+    assert!(events.lock().unwrap().is_empty());
+}
+
+#[tokio::test]
+async fn config_server_hooks_reject_duplicate_instance_name() {
+    let hooks = ManagedConfigServerClientHooks::new(None, std::ptr::null_mut());
+    let inst_name = format!("test-{}", Uuid::new_v4());
+    let existing_id = Uuid::new_v4();
+    let new_id = Uuid::new_v4();
+    INSTANCE_NAME_ID_MAP.insert(inst_name.clone(), existing_id);
+
+    let cfg = TomlConfigLoader::default();
+    cfg.set_inst_name(inst_name.clone());
+    cfg.set_id(new_id);
+
+    assert!(hooks.pre_run_network_instance(&cfg).await.is_err());
+    assert_eq!(*INSTANCE_NAME_ID_MAP.get(&inst_name).unwrap(), existing_id);
+    INSTANCE_NAME_ID_MAP.remove(&inst_name);
+}
+
+#[tokio::test]
+async fn config_server_hooks_remove_overwritten_id_before_duplicate_name_error() {
+    let events: Mutex<Vec<String>> = Mutex::new(Vec::new());
+    let hooks = ManagedConfigServerClientHooks::new(
+        Some(record_config_server_event),
+        &events as *const _ as *mut c_void,
+    );
+    let old_name = format!("old-{}", Uuid::new_v4());
+    let duplicate_name = format!("duplicate-{}", Uuid::new_v4());
+    let overwritten_id = Uuid::new_v4();
+    let duplicate_id = Uuid::new_v4();
+    hooks.instance_ids.lock().unwrap().insert(overwritten_id);
+    INSTANCE_NAME_ID_MAP.insert(old_name.clone(), overwritten_id);
+    INSTANCE_NAME_ID_MAP.insert(duplicate_name.clone(), duplicate_id);
+
+    hooks
+        .post_remove_network_instances(&[overwritten_id])
+        .await
+        .unwrap();
+
+    let cfg = TomlConfigLoader::default();
+    cfg.set_inst_name(duplicate_name.clone());
+    cfg.set_id(overwritten_id);
+
+    assert!(hooks.pre_run_network_instance(&cfg).await.is_err());
+    assert!(hooks.tracked_instance_ids().is_empty());
+    assert!(INSTANCE_NAME_ID_MAP.get(&old_name).is_none());
+    assert_eq!(
+        *INSTANCE_NAME_ID_MAP.get(&duplicate_name).unwrap(),
+        duplicate_id
+    );
+    assert_eq!(events.lock().unwrap().len(), 1);
+    INSTANCE_NAME_ID_MAP.remove(&duplicate_name);
+}
+
+#[tokio::test]
+async fn config_server_hooks_remove_tracked_state_before_overwrite_retry() {
+    let hooks = ManagedConfigServerClientHooks::new(None, std::ptr::null_mut());
+    let inst_name = format!("test-{}", Uuid::new_v4());
+    let instance_id = Uuid::new_v4();
+    hooks.instance_ids.lock().unwrap().insert(instance_id);
+    INSTANCE_NAME_ID_MAP.insert(inst_name.clone(), instance_id);
+
+    let cfg = TomlConfigLoader::default();
+    cfg.set_inst_name(inst_name.clone());
+    cfg.set_id(instance_id);
+
+    hooks
+        .post_remove_network_instances(&[instance_id])
+        .await
+        .unwrap();
+    hooks.pre_run_network_instance(&cfg).await.unwrap();
+
+    assert!(hooks.tracked_instance_ids().is_empty());
+    assert!(INSTANCE_NAME_ID_MAP.get(&inst_name).is_none());
+}
+
+#[tokio::test]
+async fn config_server_hooks_reject_post_run_after_external_delete() {
+    let hooks = ManagedConfigServerClientHooks::new(None, std::ptr::null_mut());
+    let instance_id = Uuid::new_v4();
+    let cfg = TomlConfigLoader::default();
+    cfg.set_id(instance_id);
+    cfg.set_inst_name(format!("test-{}", instance_id));
+    hooks.pre_run_network_instance(&cfg).await.unwrap();
+    INSTANCE_MANAGER
+        .run_network_instance(cfg, false, ConfigFileControl::STATIC_CONFIG)
+        .unwrap();
+    INSTANCE_MANAGER
+        .delete_network_instance(vec![instance_id])
+        .unwrap();
+
+    assert!(hooks.post_run_network_instance(&instance_id).await.is_err());
+}
+
+#[test]
+fn find_instance_id_by_name_resolves_uncommitted_manager_instance_name() {
+    let instance_id = Uuid::new_v4();
+    let inst_name = format!("test-{}", instance_id);
+    let cfg = TomlConfigLoader::default();
+    cfg.set_id(instance_id);
+    cfg.set_inst_name(inst_name.clone());
+    INSTANCE_MANAGER
+        .run_network_instance(cfg, false, ConfigFileControl::STATIC_CONFIG)
+        .unwrap();
+
+    assert_eq!(find_instance_id_by_name(&inst_name), Some(instance_id));
+    INSTANCE_MANAGER
+        .delete_network_instance(vec![instance_id])
+        .unwrap();
+    remove_instance_name_ids(&[instance_id]);
+}
+
+#[test]
+fn ffi_remote_mutation_lock_uses_manager_lock() {
+    let manager_guard = INSTANCE_MANAGER
+        .remote_mutation_lock()
+        .blocking_lock_owned();
+    let (done_tx, done_rx) = mpsc::channel();
+    let waiter = std::thread::spawn(move || {
+        let _ffi_guard = lock_remote_instance_mutation();
+        done_tx.send(()).unwrap();
+    });
+
+    assert!(done_rx.recv_timeout(Duration::from_millis(100)).is_err());
+    drop(manager_guard);
+    done_rx.recv_timeout(Duration::from_secs(5)).unwrap();
+    waiter.join().unwrap();
+}
+
+#[tokio::test]
+async fn config_server_hooks_suppress_late_run_events_while_stopping() {
+    let events: Mutex<Vec<String>> = Mutex::new(Vec::new());
+    let hooks = ManagedConfigServerClientHooks::new(
+        Some(record_config_server_event),
+        &events as *const _ as *mut c_void,
+    );
+    hooks.start_stopping();
+
+    hooks
+        .post_run_network_instance(&Uuid::new_v4())
+        .await
+        .unwrap();
+
+    assert!(hooks.tracked_instance_ids().is_empty());
+    assert!(events.lock().unwrap().is_empty());
+}
+
+#[test]
+fn config_server_callback_context_rejects_nested_blocking_ffi_calls() {
+    let _callback_scope = ConfigServerCallbackScope::enter();
+    assert_eq!(is_config_server_client_connected(), 0);
+    assert_eq!(
+        unsafe { collect_network_infos(std::ptr::null_mut(), 0) },
+        -1
+    );
+    let cfg = CString::new("inst_name = \"callback-test\"\nlisteners = []").unwrap();
+    assert_eq!(unsafe { run_network_instance(cfg.as_ptr()) }, -1);
+    assert_eq!(unsafe { retain_network_instance(std::ptr::null(), 0) }, -1);
+    let url = CString::new("ring://test/token").unwrap();
+    let machine_id = CString::new("test-machine").unwrap();
+    assert_eq!(
+        unsafe {
+            start_config_server_client(
+                url.as_ptr(),
+                std::ptr::null(),
+                machine_id.as_ptr(),
+                false,
+                None,
+                std::ptr::null_mut(),
+            )
+        },
+        -1
+    );
+    assert_eq!(stop_config_server_client(), -1);
+
+    #[cfg(feature = "ffi-dataplane")]
+    {
+        assert_eq!(
+            unsafe {
+                data_plane_tcp_connect(
+                    std::ptr::null(),
+                    std::ptr::null(),
+                    0,
+                    0,
+                    std::ptr::null_mut(),
+                    std::ptr::null_mut(),
+                )
+            },
+            0
+        );
+        assert_eq!(
+            unsafe {
+                data_plane_tcp_bind(
+                    std::ptr::null(),
+                    0,
+                    0,
+                    std::ptr::null_mut(),
+                    std::ptr::null_mut(),
+                )
+            },
+            0
+        );
+        assert_eq!(
+            unsafe {
+                data_plane_tcp_accept(
+                    0,
+                    0,
+                    std::ptr::null_mut(),
+                    std::ptr::null_mut(),
+                    std::ptr::null_mut(),
+                    std::ptr::null_mut(),
+                )
+            },
+            0
+        );
+        assert_eq!(
+            unsafe { data_plane_tcp_read(0, std::ptr::null_mut(), 0, 0) },
+            -1
+        );
+        assert_eq!(
+            unsafe { data_plane_tcp_write(0, std::ptr::null(), 0, 0) },
+            -1
+        );
+        assert_eq!(data_plane_tcp_close(0), -1);
+        assert_eq!(data_plane_tcp_listener_close(0), -1);
+        assert_eq!(
+            unsafe {
+                data_plane_udp_bind(
+                    std::ptr::null(),
+                    0,
+                    0,
+                    std::ptr::null_mut(),
+                    std::ptr::null_mut(),
+                )
+            },
+            0
+        );
+        assert_eq!(
+            unsafe { data_plane_udp_send_to(0, std::ptr::null(), 0, std::ptr::null(), 0, 0) },
+            -1
+        );
+        assert_eq!(
+            unsafe {
+                data_plane_udp_recv_from(
+                    0,
+                    std::ptr::null_mut(),
+                    0,
+                    std::ptr::null_mut(),
+                    std::ptr::null_mut(),
+                    0,
+                )
+            },
+            -1
+        );
+        assert_eq!(data_plane_udp_close(0), -1);
+    }
+}
+
+#[cfg(feature = "ffi-dataplane")]
+#[test]
+fn active_config_server_rejects_data_plane() {
+    set_active_for_test(true);
+
+    assert_eq!(
+        unsafe {
+            data_plane_tcp_connect(
+                std::ptr::null(),
+                std::ptr::null(),
+                0,
+                0,
+                std::ptr::null_mut(),
+                std::ptr::null_mut(),
+            )
+        },
+        0
+    );
+    assert_eq!(
+        unsafe { data_plane_tcp_read(0, std::ptr::null_mut(), 0, 0) },
+        -1
+    );
+
+    set_active_for_test(false);
+}

easytier-contrib/easytier-ffi/src/types.rs

@@ -0,0 +1,10 @@
+use std::ffi::{c_char, c_void};
+
+#[repr(C)]
+#[derive(Clone, Copy)]
+pub struct KeyValuePair {
+    pub key: *const c_char,
+    pub value: *const c_char,
+}
+
+pub type ConfigServerEventCallback = Option<unsafe extern "C" fn(*const c_char, *mut c_void)>;

easytier/src/instance_manager.rs

@@ -34,6 +34,7 @@ pub struct NetworkInstanceManager {
     instance_error_messages: Arc<DashMap<uuid::Uuid, String>>,
     config_dir: Option<PathBuf>,
     guard_counter: Arc<()>,
+    remote_mutation_lock: Arc<tokio::sync::Mutex<()>>,
 }
 
 impl Default for NetworkInstanceManager {
@@ -51,6 +52,7 @@ impl NetworkInstanceManager {
             instance_error_messages: Arc::new(DashMap::new()),
             config_dir: None,
             guard_counter: Arc::new(()),
+            remote_mutation_lock: Arc::new(tokio::sync::Mutex::new(())),
         }
     }
 
@@ -59,6 +61,10 @@ impl NetworkInstanceManager {
         self
     }
 
+    pub fn remote_mutation_lock(&self) -> Arc<tokio::sync::Mutex<()>> {
+        self.remote_mutation_lock.clone()
+    }
+
     fn start_instance_task(&self, instance_id: uuid::Uuid) -> Result<(), anyhow::Error> {
         if tokio::runtime::Handle::try_current().is_err() {
             return Err(anyhow::anyhow!(
@@ -272,6 +278,12 @@ impl NetworkInstanceManager {
             .map(|instance| instance.value().get_config_file_control().clone())
     }
 
+    pub fn get_instance_config(&self, instance_id: &uuid::Uuid) -> Option<TomlConfigLoader> {
+        self.instance_map
+            .get(instance_id)
+            .map(|instance| instance.value().get_config())
+    }
+
     pub fn get_instance_network_config_source(
         &self,
         instance_id: &uuid::Uuid,

easytier/src/launcher.rs

@@ -500,6 +500,10 @@ impl NetworkInstance {
         &self.config_file_control
     }
 
+    pub fn get_config(&self) -> TomlConfigLoader {
+        self.config.clone()
+    }
+
     pub fn get_network_config_source(&self) -> ConfigSource {
         self.config.get_network_config_source()
     }

easytier/src/web_client/mod.rs

@@ -23,6 +23,10 @@ use uuid::Uuid;
 
 #[async_trait]
 pub trait WebClientHooks: Send + Sync {
+    fn manages_remote_config_instances(&self) -> bool {
+        false
+    }
+
     async fn pre_run_network_instance(&self, _cfg: &TomlConfigLoader) -> Result<(), String> {
         Ok(())
     }