New Hot-Reload method + TLS-F New Methods + TLS-F/TCP-S Docs: merge pull request #420 from telemt/flow

New Hot-Reload method + TLS-F New Methods + TLS-F/TCP-S Docs

docs/fronting-splitting/TLS-F-TCP-S.ru.md

@@ -0,0 +1,274 @@
+# TLS-F и TCP-S в Telemt
+
+## Общая архитектура
+
+**Telemt** - это прежде всего реализация **MTProxy**, через которую проходит payload Telegram
+
+Подсистема **TLS-Fronting / TCP-Splitting** служит **маскировочным транспортным слоем**, задача которого - сделать MTProxy-соединение внешне похожим на обычное TLS-подключение к легитимному сайту
+
+Таким образом:
+
+- **MTProxy** - основной функциональный слой Telemt для обработки Telegram-трафика
+- **TLS-Fronting / TCP-Splitting** - подсистема маскировки транспорта
+
+С точки зрения сети Telemt ведёт себя как **TLS-сервер**, но фактически:
+
+- валидные MTProxy-клиенты остаются внутри контура Telemt
+- любые другие TLS-клиенты проксируются на обычный HTTPS-сервер-заглушку
+
+# Базовый сценарий / Best-practice
+
+Предположим, у вас есть домен:
+
+```
+umweltschutz.de
+```
+
+### 1 DNS
+
+Вы создаёте A-запись:
+
+```
+umweltschutz.de -> A-запись 198.18.88.88
+```
+
+где `198.18.88.88` - IP вашего сервера с telemt
+
+### 2 TLS-домен
+
+В конфигурации Telemt:
+
+```
+tls_domain = umweltschutz.de
+```
+
+Этот домен используется клиентом как SNI в ClientHello
+
+### 3 Сервер-заглушка
+
+Вы поднимаете обычный HTTPS-сервер, например **nginx**, с сертификатом для этого домена.
+
+Он может работать:
+
+- на том же сервере
+- на другом сервере
+- на другом порту
+
+В конфигурации Telemt:
+
+```
+mask_host = 127.0.0.1
+mask_port = 8443
+```
+
+где `127.0.0.1` - IP сервера-заглушки, а 8443 - порт, который он слушает
+
+Этот сервер нужен **для обработки любых non-MTProxy запросов**
+
+### 4 Работа Telemt
+
+После запуска Telemt действует следующим образом:
+
+1) принимает входящее TCP-соединение
+2) анализирует TLS-ClientHello
+3) пытается определить, является ли соединение валидным **MTProxy FakeTLS**
+
+Далее работают два варианта логики:
+
+---
+
+# Сценарий 1 - MTProxy клиент с валидным ключом
+
+Если клиент предъявил **валидный MTProxy-ключ**:
+
+- соединение **остаётся внутри Telemt**
+- TLS используется только как **транспортная маскировка**
+- далее запускается обычная логика **MTProxy**
+
+Для внешнего наблюдателя это выглядит как:
+
+```
+TLS connection -> umweltschutz.de
+```
+
+Хотя внутри передаётся **MTProto-трафик Telegram**
+
+# Сценарий 2 - обычный TLS-клиент - crawler / scanner / browser
+
+Если Telemt не обнаруживает валидный MTProxy-ключ:
+
+соединение **переключается в режим TCP-Splitting / TCP-Splicing**.
+
+В этом режиме Telemt:
+
+1. открывает новое TCP-соединение к
+
+```
+mask_host:mask_port
+```
+
+2. начинает **проксировать TCP-трафик**
+
+Важно:
+
+* клиентский TLS-запрос **НЕ модифицируется**
+* **ClientHello передаётся "как есть", без изменений**
+* **SNI остаётся неизменным**
+* Telemt **не завершает TLS-рукопожатие**, а только перенаправляет его на более низком уровне сетевого стека - L4
+
+Таким образом upstream-сервер получает **оригинальное TLS-соединение клиента**:
+
+- если это nginx-заглушка, он просто отдаёт обычный сайт
+- для внешнего наблюдателя это выглядит как обычный HTTPS-сервер
+
+# TCP-S / TCP-Splitting / TCP-Splicing
+
+Ключевые свойства механизма:
+
+**Telemt работает как TCP-переключатель:**
+
+1) принимает соединение
+2️) определяет тип клиента
+3) либо:
+
+- обрабатывает MTProxy внутри
+- либо проксирует TCP-поток
+
+При проксировании:
+
+- Telemt **разрешает `mask_host` в IP**
+- устанавливает TCP-соединение
+- начинает **bidirectional TCP relay**
+
+При этом:
+
+- TLS-рукопожатие происходит **между клиентом и `mask_host`**
+- Telemt выступает только **на уровне L4 - как TCP-релей**, такой же как HAProxy в TCP-режиме
+
+# Использование чужого домена
+
+Можно использовать и внешний сайт.
+
+Например:
+
+```
+tls_domain = github.com
+mask_host = github.com
+mask_port = 443
+```
+
+или
+
+```
+mask_host = 140.82.121.4
+```
+
+В этом случае:
+
+- цензор видит **TLS-подключение к github.com**
+- обычные клиенты/краулер действительно получают **настоящий GitHub**
+
+Telemt просто **проксирует TCP-соединение на GitHub**
+
+# Что видит анализатор трафика?
+
+Для DPI это выглядит так:
+
+```
+client -> TLS -> github.com
+```
+
+или
+
+```
+client -> TLS -> umweltschutz.de
+```
+
+TLS-handshake выглядит валидным, SNI соответствует домену, сертификат корректный - от целевого `mask_host:mask_port`
+
+# Что видит сканер / краулер?
+
+Если сканер попытается подключиться:
+
+```
+openssl s_client -connect 198.18.88.88:443 -servername umweltschutz.de
+```
+
+он получит **обычный HTTPS-сайт-заглушку**
+
+Потому что:
+
+- он не предъявил MTProxy-ключ
+- Telemt отправил соединение на `mask_host:mask_port`, на котором находится nginx 
+
+# Какую проблему решает TLS-Fronting / TCP-Splitting?
+
+Эта архитектура решает сразу несколько проблем обхода цензуры.
+
+## 1 Закрытие плоскости MTProxy от активного сканирования
+
+Многие цензоры:
+
+- сканируют IP-адреса
+- проверяют известные сигнатуры прокси
+
+Telemt отвечает на такие проверки **обычным HTTPS-сайтом**, поэтому прокси невозможно обнаружить простым сканированием
+
+---
+
+## 2 Маскировка трафика под легитимный TLS
+
+Для DPI-систем соединение выглядит как:
+
+```
+обычный TLS-трафик к популярному домену
+```
+
+Это делает блокировку значительно сложнее и непредсказуемее
+
+---
+
+## 3 Устойчивость к протокольному анализу
+
+MTProxy трафик проходит **внутри TLS-like-потока**, поэтому:
+
+- не видны характерные сигнатуры MTProto
+- соединение выглядит как обычный HTTPS
+
+---
+
+## 4 Правдоподобное поведение сервера
+
+Даже если краулер:
+
+- подключится сам
+- выполнит TLS-handshake
+- попытается получить HTTP-ответ
+
+он увидит **реальный сайт**, а не telemt
+
+Это устраняет один из главных признаков для антифрод-краулеров мобильных операторов
+
+# Схема
+
+```text
+			Client
+			  │
+			  │ TCP
+			  │
+			  V
+			Telemt
+			  │
+			  ├── valid MTProxy key
+			  │        │
+			  │        V
+			  │     MTProxy logic
+			  │
+			  └── обычный TLS клиент
+			  │
+			  V
+		 TCP-Splitting
+			  │
+			  V
+	  mask_host:mask_port
+```

src/config/hot_reload.rs

@@ -21,9 +21,11 @@
 //! `network.*`, `use_middle_proxy`) are **not** applied; a warning is emitted.
 //! Non-hot changes are never mixed into the runtime config snapshot.
 
+use std::collections::BTreeSet;
 use std::net::IpAddr;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
-use std::sync::Arc;
+use std::sync::{Arc, RwLock as StdRwLock};
+use std::time::Duration;
 
 use notify::{EventKind, RecursiveMode, Watcher, recommended_watcher};
 use tokio::sync::{mpsc, watch};
@@ -33,7 +35,10 @@ use crate::config::{
     LogLevel, MeBindStaleMode, MeFloorMode, MeSocksKdfPolicy, MeTelemetryLevel,
     MeWriterPickMode,
 };
-use super::load::ProxyConfig;
+use super::load::{LoadedConfig, ProxyConfig};
+
+const HOT_RELOAD_STABLE_SNAPSHOTS: u8 = 2;
+const HOT_RELOAD_DEBOUNCE: Duration = Duration::from_millis(50);
 
 // ── Hot fields ────────────────────────────────────────────────────────────────
 
@@ -287,6 +292,149 @@ fn listeners_equal(
     })
 }
 
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
+struct WatchManifest {
+    files: BTreeSet<PathBuf>,
+    dirs: BTreeSet<PathBuf>,
+}
+
+impl WatchManifest {
+    fn from_source_files(source_files: &[PathBuf]) -> Self {
+        let mut files = BTreeSet::new();
+        let mut dirs = BTreeSet::new();
+
+        for path in source_files {
+            let normalized = normalize_watch_path(path);
+            files.insert(normalized.clone());
+            if let Some(parent) = normalized.parent() {
+                dirs.insert(parent.to_path_buf());
+            }
+        }
+
+        Self { files, dirs }
+    }
+
+    fn matches_event_paths(&self, event_paths: &[PathBuf]) -> bool {
+        event_paths
+            .iter()
+            .map(|path| normalize_watch_path(path))
+            .any(|path| self.files.contains(&path))
+    }
+}
+
+#[derive(Debug, Default)]
+struct ReloadState {
+    applied_snapshot_hash: Option<u64>,
+    candidate_snapshot_hash: Option<u64>,
+    candidate_hits: u8,
+}
+
+impl ReloadState {
+    fn new(applied_snapshot_hash: Option<u64>) -> Self {
+        Self {
+            applied_snapshot_hash,
+            candidate_snapshot_hash: None,
+            candidate_hits: 0,
+        }
+    }
+
+    fn is_applied(&self, hash: u64) -> bool {
+        self.applied_snapshot_hash == Some(hash)
+    }
+
+    fn observe_candidate(&mut self, hash: u64) -> u8 {
+        if self.candidate_snapshot_hash == Some(hash) {
+            self.candidate_hits = self.candidate_hits.saturating_add(1);
+        } else {
+            self.candidate_snapshot_hash = Some(hash);
+            self.candidate_hits = 1;
+        }
+        self.candidate_hits
+    }
+
+    fn reset_candidate(&mut self) {
+        self.candidate_snapshot_hash = None;
+        self.candidate_hits = 0;
+    }
+
+    fn mark_applied(&mut self, hash: u64) {
+        self.applied_snapshot_hash = Some(hash);
+        self.reset_candidate();
+    }
+}
+
+fn normalize_watch_path(path: &Path) -> PathBuf {
+    path.canonicalize().unwrap_or_else(|_| {
+        if path.is_absolute() {
+            path.to_path_buf()
+        } else {
+            std::env::current_dir()
+                .map(|cwd| cwd.join(path))
+                .unwrap_or_else(|_| path.to_path_buf())
+        }
+    })
+}
+
+fn sync_watch_paths<W: Watcher>(
+    watcher: &mut W,
+    current: &BTreeSet<PathBuf>,
+    next: &BTreeSet<PathBuf>,
+    recursive_mode: RecursiveMode,
+    kind: &str,
+) {
+    for path in current.difference(next) {
+        if let Err(e) = watcher.unwatch(path) {
+            warn!(path = %path.display(), error = %e, "config watcher: failed to unwatch {kind}");
+        }
+    }
+
+    for path in next.difference(current) {
+        if let Err(e) = watcher.watch(path, recursive_mode) {
+            warn!(path = %path.display(), error = %e, "config watcher: failed to watch {kind}");
+        }
+    }
+}
+
+fn apply_watch_manifest<W1: Watcher, W2: Watcher>(
+    notify_watcher: Option<&mut W1>,
+    poll_watcher: Option<&mut W2>,
+    manifest_state: &Arc<StdRwLock<WatchManifest>>,
+    next_manifest: WatchManifest,
+) {
+    let current_manifest = manifest_state
+        .read()
+        .map(|manifest| manifest.clone())
+        .unwrap_or_default();
+
+    if current_manifest == next_manifest {
+        return;
+    }
+
+    if let Some(watcher) = notify_watcher {
+        sync_watch_paths(
+            watcher,
+            &current_manifest.dirs,
+            &next_manifest.dirs,
+            RecursiveMode::NonRecursive,
+            "config directory",
+        );
+    }
+
+    if let Some(watcher) = poll_watcher {
+        sync_watch_paths(
+            watcher,
+            &current_manifest.files,
+            &next_manifest.files,
+            RecursiveMode::NonRecursive,
+            "config file",
+        );
+    }
+
+    if let Ok(mut manifest) = manifest_state.write() {
+        *manifest = next_manifest;
+    }
+}
+
 fn overlay_hot_fields(old: &ProxyConfig, new: &ProxyConfig) -> ProxyConfig {
     let mut cfg = old.clone();
 
@@ -970,18 +1118,42 @@ fn reload_config(
     log_tx: &watch::Sender<LogLevel>,
     detected_ip_v4: Option<IpAddr>,
     detected_ip_v6: Option<IpAddr>,
-) {
+    reload_state: &mut ReloadState,
-    let new_cfg = match ProxyConfig::load(config_path) {
+) -> Option<WatchManifest> {
-        Ok(c) => c,
+    let loaded = match ProxyConfig::load_with_metadata(config_path) {
+        Ok(loaded) => loaded,
         Err(e) => {
+            reload_state.reset_candidate();
             error!("config reload: failed to parse {:?}: {}", config_path, e);
-            return;
+            return None;
         }
     };
+    let LoadedConfig {
+        config: new_cfg,
+        source_files,
+        rendered_hash,
+    } = loaded;
+    let next_manifest = WatchManifest::from_source_files(&source_files);
 
     if let Err(e) = new_cfg.validate() {
+        reload_state.reset_candidate();
         error!("config reload: validation failed: {}; keeping old config", e);
-        return;
+        return Some(next_manifest);
+    }
+
+    if reload_state.is_applied(rendered_hash) {
+        return Some(next_manifest);
+    }
+
+    let candidate_hits = reload_state.observe_candidate(rendered_hash);
+    if candidate_hits < HOT_RELOAD_STABLE_SNAPSHOTS {
+        info!(
+            snapshot_hash = rendered_hash,
+            candidate_hits,
+            required_hits = HOT_RELOAD_STABLE_SNAPSHOTS,
+            "config reload: candidate snapshot observed but not stable yet"
+        );
+        return Some(next_manifest);
     }
 
     let old_cfg = config_tx.borrow().clone();
@@ -996,17 +1168,19 @@ fn reload_config(
     }
 
     if !hot_changed {
-        return;
+        reload_state.mark_applied(rendered_hash);
+        return Some(next_manifest);
     }
 
     if old_hot.dns_overrides != applied_hot.dns_overrides
         && let Err(e) = crate::network::dns_overrides::install_entries(&applied_hot.dns_overrides)
     {
+        reload_state.reset_candidate();
         error!(
             "config reload: invalid network.dns_overrides: {}; keeping old config",
             e
         );
-        return;
+        return Some(next_manifest);
     }
 
     log_changes(
@@ -1018,6 +1192,8 @@ fn reload_config(
         detected_ip_v6,
     );
     config_tx.send(Arc::new(applied_cfg)).ok();
+    reload_state.mark_applied(rendered_hash);
+    Some(next_manifest)
 }
 
 // ── Public API ────────────────────────────────────────────────────────────────
@@ -1040,80 +1216,86 @@ pub fn spawn_config_watcher(
     let (config_tx, config_rx) = watch::channel(initial);
     let (log_tx, log_rx)       = watch::channel(initial_level);
 
-    // Bridge: sync notify callbacks → async task via mpsc.
+    let config_path = normalize_watch_path(&config_path);
+    let initial_loaded = ProxyConfig::load_with_metadata(&config_path).ok();
+    let initial_manifest = initial_loaded
+        .as_ref()
+        .map(|loaded| WatchManifest::from_source_files(&loaded.source_files))
+        .unwrap_or_else(|| WatchManifest::from_source_files(std::slice::from_ref(&config_path)));
+    let initial_snapshot_hash = initial_loaded.as_ref().map(|loaded| loaded.rendered_hash);
+
+    tokio::spawn(async move {
         let (notify_tx, mut notify_rx) = mpsc::channel::<()>(4);
+        let manifest_state = Arc::new(StdRwLock::new(WatchManifest::default()));
+        let mut reload_state = ReloadState::new(initial_snapshot_hash);
 
-    // Canonicalize so path matches what notify returns (absolute) in events.
-    let config_path = match config_path.canonicalize() {
-        Ok(p) => p,
-        Err(_) => config_path.to_path_buf(),
-    };
-
-    // Watch the parent directory rather than the file itself, because many
-    // editors (vim, nano) and systemd write via rename, which would cause
-    // inotify to lose track of the original inode.
-    let watch_dir = config_path
-        .parent()
-        .unwrap_or_else(|| std::path::Path::new("."))
-        .to_path_buf();
-
-    // ── inotify watcher (instant on local fs) ────────────────────────────
-    let config_file = config_path.clone();
         let tx_inotify = notify_tx.clone();
-    let inotify_ok = match recommended_watcher(move |res: notify::Result<notify::Event>| {
+        let manifest_for_inotify = manifest_state.clone();
+        let mut inotify_watcher = match recommended_watcher(move |res: notify::Result<notify::Event>| {
             let Ok(event) = res else { return };
-        let is_our_file = event.paths.iter().any(|p| p == &config_file);
+            if !matches!(event.kind, EventKind::Modify(_) | EventKind::Create(_) | EventKind::Remove(_)) {
-        if !is_our_file { return; }
+                return;
-        if matches!(event.kind, EventKind::Modify(_) | EventKind::Create(_) | EventKind::Remove(_)) {
+            }
+            let is_our_file = manifest_for_inotify
+                .read()
+                .map(|manifest| manifest.matches_event_paths(&event.paths))
+                .unwrap_or(false);
+            if is_our_file {
                 let _ = tx_inotify.try_send(());
             }
         }) {
-        Ok(mut w) => match w.watch(&watch_dir, RecursiveMode::NonRecursive) {
+            Ok(watcher) => Some(watcher),
-            Ok(()) => {
+            Err(e) => {
-                info!("config watcher: inotify active on {:?}", config_path);
+                warn!("config watcher: inotify unavailable: {}", e);
-                Box::leak(Box::new(w));
+                None
-                true
             }
-            Err(e) => { warn!("config watcher: inotify watch failed: {}", e); false }
-        },
-        Err(e) => { warn!("config watcher: inotify unavailable: {}", e); false }
         };
+        apply_watch_manifest(
+            inotify_watcher.as_mut(),
+            Option::<&mut notify::poll::PollWatcher>::None,
+            &manifest_state,
+            initial_manifest.clone(),
+        );
+        if inotify_watcher.is_some() {
+            info!("config watcher: inotify active on {:?}", config_path);
+        }
 
-    // ── poll watcher (always active, fixes Docker bind mounts / NFS) ─────
-    // inotify does not receive events for files mounted from the host into
-    // a container. PollWatcher compares file contents every 3 s and fires
-    // on any change regardless of the underlying fs.
-    let config_file2 = config_path.clone();
         let tx_poll = notify_tx.clone();
-    match notify::poll::PollWatcher::new(
+        let manifest_for_poll = manifest_state.clone();
+        let mut poll_watcher = match notify::poll::PollWatcher::new(
             move |res: notify::Result<notify::Event>| {
                 let Ok(event) = res else { return };
-            let is_our_file = event.paths.iter().any(|p| p == &config_file2);
+                if !matches!(event.kind, EventKind::Modify(_) | EventKind::Create(_) | EventKind::Remove(_)) {
-            if !is_our_file { return; }
+                    return;
-            if matches!(event.kind, EventKind::Modify(_) | EventKind::Create(_) | EventKind::Remove(_)) {
+                }
+                let is_our_file = manifest_for_poll
+                    .read()
+                    .map(|manifest| manifest.matches_event_paths(&event.paths))
+                    .unwrap_or(false);
+                if is_our_file {
                     let _ = tx_poll.try_send(());
                 }
             },
             notify::Config::default()
-            .with_poll_interval(std::time::Duration::from_secs(3))
+                .with_poll_interval(Duration::from_secs(3))
                 .with_compare_contents(true),
         ) {
-        Ok(mut w) => match w.watch(&config_path, RecursiveMode::NonRecursive) {
+            Ok(watcher) => Some(watcher),
-            Ok(()) => {
+            Err(e) => {
-                if inotify_ok {
+                warn!("config watcher: poll watcher unavailable: {}", e);
-                    info!("config watcher: poll watcher also active (Docker/NFS safe)");
+                None
-                } else {
-                    info!("config watcher: poll watcher active on {:?} (3s interval)", config_path);
             }
-                Box::leak(Box::new(w));
+        };
-            }
+        apply_watch_manifest(
-            Err(e) => warn!("config watcher: poll watch failed: {}", e),
+            Option::<&mut notify::RecommendedWatcher>::None,
-        },
+            poll_watcher.as_mut(),
-        Err(e) => warn!("config watcher: poll watcher unavailable: {}", e),
+            &manifest_state,
+            initial_manifest.clone(),
+        );
+        if poll_watcher.is_some() {
+            info!("config watcher: poll watcher active (Docker/NFS safe)");
         }
 
-    // ── event loop ───────────────────────────────────────────────────────
-    tokio::spawn(async move {
         #[cfg(unix)]
         let mut sighup = {
             use tokio::signal::unix::{SignalKind, signal};
@@ -1133,11 +1315,25 @@ pub fn spawn_config_watcher(
             #[cfg(not(unix))]
             if notify_rx.recv().await.is_none() { break; }
 
-            // Debounce: drain extra events that arrive within 50 ms.
+            // Debounce: drain extra events that arrive within a short quiet window.
-            tokio::time::sleep(std::time::Duration::from_millis(50)).await;
+            tokio::time::sleep(HOT_RELOAD_DEBOUNCE).await;
             while notify_rx.try_recv().is_ok() {}
 
-            reload_config(&config_path, &config_tx, &log_tx, detected_ip_v4, detected_ip_v6);
+            if let Some(next_manifest) = reload_config(
+                &config_path,
+                &config_tx,
+                &log_tx,
+                detected_ip_v4,
+                detected_ip_v6,
+                &mut reload_state,
+            ) {
+                apply_watch_manifest(
+                    inotify_watcher.as_mut(),
+                    poll_watcher.as_mut(),
+                    &manifest_state,
+                    next_manifest,
+                );
+            }
         }
     });
 
@@ -1152,6 +1348,40 @@ mod tests {
         ProxyConfig::default()
     }
 
+    fn write_reload_config(path: &Path, ad_tag: Option<&str>, server_port: Option<u16>) {
+        let mut config = String::from(
+            r#"
+                [censorship]
+                tls_domain = "example.com"
+
+                [access.users]
+                user = "00000000000000000000000000000000"
+            "#,
+        );
+
+        if ad_tag.is_some() {
+            config.push_str("\n[general]\n");
+            if let Some(tag) = ad_tag {
+                config.push_str(&format!("ad_tag = \"{tag}\"\n"));
+            }
+        }
+
+        if let Some(port) = server_port {
+            config.push_str("\n[server]\n");
+            config.push_str(&format!("port = {port}\n"));
+        }
+
+        std::fs::write(path, config).unwrap();
+    }
+
+    fn temp_config_path(prefix: &str) -> PathBuf {
+        let nonce = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap()
+            .as_nanos();
+        std::env::temp_dir().join(format!("{prefix}_{nonce}.toml"))
+    }
+
     #[test]
     fn overlay_applies_hot_and_preserves_non_hot() {
         let old = sample_config();
@@ -1219,4 +1449,61 @@ mod tests {
         assert_eq!(applied.general.use_middle_proxy, old.general.use_middle_proxy);
         assert!(!config_equal(&applied, &new));
     }
+
+    #[test]
+    fn reload_requires_stable_snapshot_before_hot_apply() {
+        let initial_tag = "11111111111111111111111111111111";
+        let final_tag = "22222222222222222222222222222222";
+        let path = temp_config_path("telemt_hot_reload_stable");
+
+        write_reload_config(&path, Some(initial_tag), None);
+        let initial_cfg = Arc::new(ProxyConfig::load(&path).unwrap());
+        let initial_hash = ProxyConfig::load_with_metadata(&path).unwrap().rendered_hash;
+        let (config_tx, _config_rx) = watch::channel(initial_cfg.clone());
+        let (log_tx, _log_rx) = watch::channel(initial_cfg.general.log_level.clone());
+        let mut reload_state = ReloadState::new(Some(initial_hash));
+
+        write_reload_config(&path, None, None);
+        reload_config(&path, &config_tx, &log_tx, None, None, &mut reload_state).unwrap();
+        assert_eq!(
+            config_tx.borrow().general.ad_tag.as_deref(),
+            Some(initial_tag)
+        );
+
+        write_reload_config(&path, Some(final_tag), None);
+        reload_config(&path, &config_tx, &log_tx, None, None, &mut reload_state).unwrap();
+        assert_eq!(
+            config_tx.borrow().general.ad_tag.as_deref(),
+            Some(initial_tag)
+        );
+
+        reload_config(&path, &config_tx, &log_tx, None, None, &mut reload_state).unwrap();
+        assert_eq!(config_tx.borrow().general.ad_tag.as_deref(), Some(final_tag));
+
+        let _ = std::fs::remove_file(path);
+    }
+
+    #[test]
+    fn reload_keeps_hot_apply_when_non_hot_fields_change() {
+        let initial_tag = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+        let final_tag = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb";
+        let path = temp_config_path("telemt_hot_reload_mixed");
+
+        write_reload_config(&path, Some(initial_tag), None);
+        let initial_cfg = Arc::new(ProxyConfig::load(&path).unwrap());
+        let initial_hash = ProxyConfig::load_with_metadata(&path).unwrap().rendered_hash;
+        let (config_tx, _config_rx) = watch::channel(initial_cfg.clone());
+        let (log_tx, _log_rx) = watch::channel(initial_cfg.general.log_level.clone());
+        let mut reload_state = ReloadState::new(Some(initial_hash));
+
+        write_reload_config(&path, Some(final_tag), Some(initial_cfg.server.port + 1));
+        reload_config(&path, &config_tx, &log_tx, None, None, &mut reload_state).unwrap();
+        reload_config(&path, &config_tx, &log_tx, None, None, &mut reload_state).unwrap();
+
+        let applied = config_tx.borrow().clone();
+        assert_eq!(applied.general.ad_tag.as_deref(), Some(final_tag));
+        assert_eq!(applied.server.port, initial_cfg.server.port);
+
+        let _ = std::fs::remove_file(path);
+    }
 }

src/config/load.rs

@@ -1,8 +1,9 @@
 #![allow(deprecated)]
 
-use std::collections::HashMap;
+use std::collections::{BTreeSet, HashMap};
+use std::hash::{DefaultHasher, Hash, Hasher};
 use std::net::{IpAddr, SocketAddr};
-use std::path::Path;
+use std::path::{Path, PathBuf};
 
 use rand::Rng;
 use tracing::warn;
@@ -13,7 +14,37 @@ use crate::error::{ProxyError, Result};
 use super::defaults::*;
 use super::types::*;
 
-fn preprocess_includes(content: &str, base_dir: &Path, depth: u8) -> Result<String> {
+#[derive(Debug, Clone)]
+pub(crate) struct LoadedConfig {
+    pub(crate) config: ProxyConfig,
+    pub(crate) source_files: Vec<PathBuf>,
+    pub(crate) rendered_hash: u64,
+}
+
+fn normalize_config_path(path: &Path) -> PathBuf {
+    path.canonicalize().unwrap_or_else(|_| {
+        if path.is_absolute() {
+            path.to_path_buf()
+        } else {
+            std::env::current_dir()
+                .map(|cwd| cwd.join(path))
+                .unwrap_or_else(|_| path.to_path_buf())
+        }
+    })
+}
+
+fn hash_rendered_snapshot(rendered: &str) -> u64 {
+    let mut hasher = DefaultHasher::new();
+    rendered.hash(&mut hasher);
+    hasher.finish()
+}
+
+fn preprocess_includes(
+    content: &str,
+    base_dir: &Path,
+    depth: u8,
+    source_files: &mut BTreeSet<PathBuf>,
+) -> Result<String> {
     if depth > 10 {
         return Err(ProxyError::Config("Include depth > 10".into()));
     }
@@ -25,10 +56,16 @@ fn preprocess_includes(content: &str, base_dir: &Path, depth: u8) -> Result<Stri
             if let Some(rest) = rest.strip_prefix('=') {
                 let path_str = rest.trim().trim_matches('"');
                 let resolved = base_dir.join(path_str);
+                source_files.insert(normalize_config_path(&resolved));
                 let included = std::fs::read_to_string(&resolved)
                     .map_err(|e| ProxyError::Config(e.to_string()))?;
                 let included_dir = resolved.parent().unwrap_or(base_dir);
-                output.push_str(&preprocess_includes(&included, included_dir, depth + 1)?);
+                output.push_str(&preprocess_includes(
+                    &included,
+                    included_dir,
+                    depth + 1,
+                    source_files,
+                )?);
                 output.push('\n');
                 continue;
             }
@@ -138,10 +175,16 @@ pub struct ProxyConfig {
 
 impl ProxyConfig {
     pub fn load<P: AsRef<Path>>(path: P) -> Result<Self> {
-        let content =
+        Self::load_with_metadata(path).map(|loaded| loaded.config)
-            std::fs::read_to_string(&path).map_err(|e| ProxyError::Config(e.to_string()))?;
+    }
-        let base_dir = path.as_ref().parent().unwrap_or(Path::new("."));
+
-        let processed = preprocess_includes(&content, base_dir, 0)?;
+    pub(crate) fn load_with_metadata<P: AsRef<Path>>(path: P) -> Result<LoadedConfig> {
+        let path = path.as_ref();
+        let content = std::fs::read_to_string(path).map_err(|e| ProxyError::Config(e.to_string()))?;
+        let base_dir = path.parent().unwrap_or(Path::new("."));
+        let mut source_files = BTreeSet::new();
+        source_files.insert(normalize_config_path(path));
+        let processed = preprocess_includes(&content, base_dir, 0, &mut source_files)?;
 
         let parsed_toml: toml::Value =
             toml::from_str(&processed).map_err(|e| ProxyError::Config(e.to_string()))?;
@@ -786,7 +829,11 @@ impl ProxyConfig {
             .entry("203".to_string())
             .or_insert_with(|| vec!["91.105.192.100:443".to_string()]);
 
-        Ok(config)
+        Ok(LoadedConfig {
+            config,
+            source_files: source_files.into_iter().collect(),
+            rendered_hash: hash_rendered_snapshot(&processed),
+        })
     }
 
     pub fn validate(&self) -> Result<()> {
@@ -1111,6 +1158,48 @@ mod tests {
         );
     }
 
+    #[test]
+    fn load_with_metadata_collects_include_files() {
+        let nonce = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap()
+            .as_nanos();
+        let dir = std::env::temp_dir().join(format!("telemt_load_metadata_{nonce}"));
+        std::fs::create_dir_all(&dir).unwrap();
+        let main_path = dir.join("config.toml");
+        let include_path = dir.join("included.toml");
+
+        std::fs::write(
+            &include_path,
+            r#"
+                [access.users]
+                user = "00000000000000000000000000000000"
+            "#,
+        )
+        .unwrap();
+        std::fs::write(
+            &main_path,
+            r#"
+                include = "included.toml"
+
+                [censorship]
+                tls_domain = "example.com"
+            "#,
+        )
+        .unwrap();
+
+        let loaded = ProxyConfig::load_with_metadata(&main_path).unwrap();
+        let main_normalized = normalize_config_path(&main_path);
+        let include_normalized = normalize_config_path(&include_path);
+
+        assert!(loaded.source_files.contains(&main_normalized));
+        assert!(loaded.source_files.contains(&include_normalized));
+
+        let _ = std::fs::remove_file(main_path);
+        let _ = std::fs::remove_file(include_path);
+        let _ = std::fs::remove_dir(dir);
+    }
+
     #[test]
     fn dc_overrides_inject_dc203_default() {
         let toml = r#"

src/tls_front/cache.rs

@@ -8,7 +8,9 @@ use tokio::sync::RwLock;
 use tokio::time::sleep;
 use tracing::{debug, warn, info};
 
-use crate::tls_front::types::{CachedTlsData, ParsedServerHello, TlsFetchResult};
+use crate::tls_front::types::{
+    CachedTlsData, ParsedServerHello, TlsBehaviorProfile, TlsFetchResult,
+};
 
 /// Lightweight in-memory + optional on-disk cache for TLS fronting data.
 #[derive(Debug)]
@@ -37,6 +39,7 @@ impl TlsFrontCache {
             cert_payload: None,
             app_data_records_sizes: vec![default_len],
             total_app_data_len: default_len,
+            behavior_profile: TlsBehaviorProfile::default(),
             fetched_at: SystemTime::now(),
             domain: "default".to_string(),
         });
@@ -189,6 +192,7 @@ impl TlsFrontCache {
             cert_payload: fetched.cert_payload,
             app_data_records_sizes: fetched.app_data_records_sizes.clone(),
             total_app_data_len: fetched.total_app_data_len,
+            behavior_profile: fetched.behavior_profile,
             fetched_at: SystemTime::now(),
             domain: domain.to_string(),
         };

src/tls_front/emulator.rs

@@ -3,7 +3,7 @@ use crate::protocol::constants::{
     TLS_RECORD_APPLICATION, TLS_RECORD_CHANGE_CIPHER, TLS_RECORD_HANDSHAKE, TLS_VERSION,
 };
 use crate::protocol::tls::{TLS_DIGEST_LEN, TLS_DIGEST_POS, gen_fake_x25519_key};
-use crate::tls_front::types::{CachedTlsData, ParsedCertificateInfo};
+use crate::tls_front::types::{CachedTlsData, ParsedCertificateInfo, TlsProfileSource};
 
 const MIN_APP_DATA: usize = 64;
 const MAX_APP_DATA: usize = 16640; // RFC 8446 §5.2 allows up to 2^14 + 256
@@ -108,14 +108,12 @@ pub fn build_emulated_server_hello(
 ) -> Vec<u8> {
     // --- ServerHello ---
     let mut extensions = Vec::new();
-    // KeyShare (x25519)
     let key = gen_fake_x25519_key(rng);
-    extensions.extend_from_slice(&0x0033u16.to_be_bytes()); // key_share
+    extensions.extend_from_slice(&0x0033u16.to_be_bytes());
-    extensions.extend_from_slice(&(2 + 2 + 32u16).to_be_bytes()); // len
+    extensions.extend_from_slice(&(2 + 2 + 32u16).to_be_bytes());
-    extensions.extend_from_slice(&0x001du16.to_be_bytes()); // X25519
+    extensions.extend_from_slice(&0x001du16.to_be_bytes());
     extensions.extend_from_slice(&(32u16).to_be_bytes());
     extensions.extend_from_slice(&key);
-    // supported_versions (TLS1.3)
     extensions.extend_from_slice(&0x002bu16.to_be_bytes());
     extensions.extend_from_slice(&(2u16).to_be_bytes());
     extensions.extend_from_slice(&0x0304u16.to_be_bytes());
@@ -128,7 +126,6 @@ pub fn build_emulated_server_hello(
         extensions.push(alpn_proto.len() as u8);
         extensions.extend_from_slice(alpn_proto);
     }
-
     let extensions_len = extensions.len() as u16;
 
     let body_len = 2 + // version
@@ -173,11 +170,22 @@ pub fn build_emulated_server_hello(
     ];
 
     // --- ApplicationData (fake encrypted records) ---
-    // Use the same number and sizes of ApplicationData records as the cached server.
+    let sizes = match cached.behavior_profile.source {
+        TlsProfileSource::Raw | TlsProfileSource::Merged => cached
+            .app_data_records_sizes
+            .first()
+            .copied()
+            .or_else(|| cached.behavior_profile.app_data_record_sizes.first().copied())
+            .map(|size| vec![size])
+            .unwrap_or_else(|| vec![cached.total_app_data_len.max(1024)]),
+        _ => {
             let mut sizes = cached.app_data_records_sizes.clone();
             if sizes.is_empty() {
                 sizes.push(cached.total_app_data_len.max(1024));
             }
+            sizes
+        }
+    };
     let mut sizes = jitter_and_clamp_sizes(&sizes, rng);
     let compact_payload = cached
         .cert_info
@@ -269,7 +277,9 @@ pub fn build_emulated_server_hello(
 mod tests {
     use std::time::SystemTime;
 
-    use crate::tls_front::types::{CachedTlsData, ParsedServerHello, TlsCertPayload};
+    use crate::tls_front::types::{
+        CachedTlsData, ParsedServerHello, TlsBehaviorProfile, TlsCertPayload, TlsProfileSource,
+    };
 
     use super::build_emulated_server_hello;
     use crate::crypto::SecureRandom;
@@ -300,6 +310,7 @@ mod tests {
             cert_payload,
             app_data_records_sizes: vec![64],
             total_app_data_len: 64,
+            behavior_profile: TlsBehaviorProfile::default(),
             fetched_at: SystemTime::now(),
             domain: "example.com".to_string(),
         }
@@ -385,4 +396,34 @@ mod tests {
         let payload = first_app_data_payload(&response);
         assert!(payload.starts_with(b"CN=example.com"));
     }
+
+    #[test]
+    fn test_build_emulated_server_hello_ignores_tail_records_for_raw_profile() {
+        let mut cached = make_cached(None);
+        cached.app_data_records_sizes = vec![27, 3905, 537, 69];
+        cached.total_app_data_len = 4538;
+        cached.behavior_profile.source = TlsProfileSource::Merged;
+        cached.behavior_profile.app_data_record_sizes = vec![27, 3905, 537];
+        cached.behavior_profile.ticket_record_sizes = vec![69];
+
+        let rng = SecureRandom::new();
+        let response = build_emulated_server_hello(
+            b"secret",
+            &[0x12; 32],
+            &[0x34; 16],
+            &cached,
+            false,
+            &rng,
+            None,
+            0,
+        );
+
+        let hello_len = u16::from_be_bytes([response[3], response[4]]) as usize;
+        let ccs_start = 5 + hello_len;
+        let app_start = ccs_start + 6;
+        let app_len = u16::from_be_bytes([response[app_start + 3], response[app_start + 4]]) as usize;
+
+        assert_eq!(response[app_start], TLS_RECORD_APPLICATION);
+        assert_eq!(app_start + 5 + app_len, response.len());
+    }
 }

src/tls_front/fetcher.rs

@@ -21,14 +21,18 @@ use x509_parser::certificate::X509Certificate;
 
 use crate::crypto::SecureRandom;
 use crate::network::dns_overrides::resolve_socket_addr;
-use crate::protocol::constants::{TLS_RECORD_APPLICATION, TLS_RECORD_HANDSHAKE};
+use crate::protocol::constants::{
+    TLS_RECORD_APPLICATION, TLS_RECORD_CHANGE_CIPHER, TLS_RECORD_HANDSHAKE,
+};
 use crate::transport::proxy_protocol::{ProxyProtocolV1Builder, ProxyProtocolV2Builder};
 use crate::tls_front::types::{
     ParsedCertificateInfo,
     ParsedServerHello,
+    TlsBehaviorProfile,
     TlsCertPayload,
     TlsExtension,
     TlsFetchResult,
+    TlsProfileSource,
 };
 
 /// No-op verifier: accept any certificate (we only need lengths and metadata).
@@ -282,6 +286,41 @@ fn parse_server_hello(body: &[u8]) -> Option<ParsedServerHello> {
     })
 }
 
+fn derive_behavior_profile(records: &[(u8, Vec<u8>)]) -> TlsBehaviorProfile {
+    let mut change_cipher_spec_count = 0u8;
+    let mut app_data_record_sizes = Vec::new();
+
+    for (record_type, body) in records {
+        match *record_type {
+            TLS_RECORD_CHANGE_CIPHER => {
+                change_cipher_spec_count = change_cipher_spec_count.saturating_add(1);
+            }
+            TLS_RECORD_APPLICATION => {
+                app_data_record_sizes.push(body.len());
+            }
+            _ => {}
+        }
+    }
+
+    let mut ticket_record_sizes = Vec::new();
+    while app_data_record_sizes
+        .last()
+        .is_some_and(|size| *size <= 256 && ticket_record_sizes.len() < 2)
+    {
+        if let Some(size) = app_data_record_sizes.pop() {
+            ticket_record_sizes.push(size);
+        }
+    }
+    ticket_record_sizes.reverse();
+
+    TlsBehaviorProfile {
+        change_cipher_spec_count: change_cipher_spec_count.max(1),
+        app_data_record_sizes,
+        ticket_record_sizes,
+        source: TlsProfileSource::Raw,
+    }
+}
+
 fn parse_cert_info(certs: &[CertificateDer<'static>]) -> Option<ParsedCertificateInfo> {
     let first = certs.first()?;
     let (_rem, cert) = X509Certificate::from_der(first.as_ref()).ok()?;
@@ -443,39 +482,50 @@ where
     .await??;
 
     let mut records = Vec::new();
-    // Read up to 4 records: ServerHello, CCS, and up to two ApplicationData.
+    let mut app_records_seen = 0usize;
-    for _ in 0..4 {
+    // Read a bounded encrypted flight: ServerHello, CCS, certificate-like data,
+    // and a small number of ticket-like tail records.
+    for _ in 0..8 {
         match timeout(connect_timeout, read_tls_record(&mut stream)).await {
-            Ok(Ok(rec)) => records.push(rec),
+            Ok(Ok(rec)) => {
+                if rec.0 == TLS_RECORD_APPLICATION {
+                    app_records_seen += 1;
+                }
+                records.push(rec);
+            }
             Ok(Err(e)) => return Err(e),
             Err(_) => break,
         }
-        if records.len() >= 3 && records.iter().any(|(t, _)| *t == TLS_RECORD_APPLICATION) {
+        if app_records_seen >= 4 {
             break;
         }
     }
 
-    let mut app_sizes = Vec::new();
     let mut server_hello = None;
     for (t, body) in &records {
         if *t == TLS_RECORD_HANDSHAKE && server_hello.is_none() {
             server_hello = parse_server_hello(body);
-        } else if *t == TLS_RECORD_APPLICATION {
-            app_sizes.push(body.len());
         }
     }
 
     let parsed = server_hello.ok_or_else(|| anyhow!("ServerHello not received"))?;
+    let behavior_profile = derive_behavior_profile(&records);
+    let mut app_sizes = behavior_profile.app_data_record_sizes.clone();
+    app_sizes.extend_from_slice(&behavior_profile.ticket_record_sizes);
     let total_app_data_len = app_sizes.iter().sum::<usize>().max(1024);
+    let app_data_records_sizes = behavior_profile
+        .app_data_record_sizes
+        .first()
+        .copied()
+        .or_else(|| behavior_profile.ticket_record_sizes.first().copied())
+        .map(|size| vec![size])
+        .unwrap_or_else(|| vec![total_app_data_len]);
 
     Ok(TlsFetchResult {
         server_hello_parsed: parsed,
-        app_data_records_sizes: if app_sizes.is_empty() {
+        app_data_records_sizes,
-            vec![total_app_data_len]
-        } else {
-            app_sizes
-        },
         total_app_data_len,
+        behavior_profile,
         cert_info: None,
         cert_payload: None,
     })
@@ -608,6 +658,12 @@ where
         server_hello_parsed: parsed,
         app_data_records_sizes: app_data_records_sizes.clone(),
         total_app_data_len: app_data_records_sizes.iter().sum(),
+        behavior_profile: TlsBehaviorProfile {
+            change_cipher_spec_count: 1,
+            app_data_record_sizes: app_data_records_sizes,
+            ticket_record_sizes: Vec::new(),
+            source: TlsProfileSource::Rustls,
+        },
         cert_info,
         cert_payload,
     })
@@ -706,6 +762,7 @@ pub async fn fetch_real_tls(
             if let Some(mut raw) = raw_result {
                 raw.cert_info = rustls_result.cert_info;
                 raw.cert_payload = rustls_result.cert_payload;
+                raw.behavior_profile.source = TlsProfileSource::Merged;
                 debug!(sni = %sni, "Fetched TLS metadata via raw probe + rustls cert chain");
                 Ok(raw)
             } else {
@@ -725,7 +782,11 @@ pub async fn fetch_real_tls(
 
 #[cfg(test)]
 mod tests {
-    use super::encode_tls13_certificate_message;
+    use super::{derive_behavior_profile, encode_tls13_certificate_message};
+    use crate::protocol::constants::{
+        TLS_RECORD_APPLICATION, TLS_RECORD_CHANGE_CIPHER, TLS_RECORD_HANDSHAKE,
+    };
+    use crate::tls_front::types::TlsProfileSource;
 
     fn read_u24(bytes: &[u8]) -> usize {
         ((bytes[0] as usize) << 16) | ((bytes[1] as usize) << 8) | (bytes[2] as usize)
@@ -753,4 +814,20 @@ mod tests {
     fn test_encode_tls13_certificate_message_empty_chain() {
         assert!(encode_tls13_certificate_message(&[]).is_none());
     }
+
+    #[test]
+    fn test_derive_behavior_profile_splits_ticket_like_tail_records() {
+        let profile = derive_behavior_profile(&[
+            (TLS_RECORD_HANDSHAKE, vec![0u8; 90]),
+            (TLS_RECORD_CHANGE_CIPHER, vec![0x01]),
+            (TLS_RECORD_APPLICATION, vec![0u8; 1400]),
+            (TLS_RECORD_APPLICATION, vec![0u8; 220]),
+            (TLS_RECORD_APPLICATION, vec![0u8; 180]),
+        ]);
+
+        assert_eq!(profile.change_cipher_spec_count, 1);
+        assert_eq!(profile.app_data_record_sizes, vec![1400]);
+        assert_eq!(profile.ticket_record_sizes, vec![220, 180]);
+        assert_eq!(profile.source, TlsProfileSource::Raw);
+    }
 }

src/tls_front/types.rs

@@ -39,6 +39,53 @@ pub struct TlsCertPayload {
     pub certificate_message: Vec<u8>,
 }
 
+/// Provenance of the cached TLS behavior profile.
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Default)]
+#[serde(rename_all = "snake_case")]
+pub enum TlsProfileSource {
+    /// Built from hardcoded defaults or legacy cache entries.
+    #[default]
+    Default,
+    /// Derived from raw TLS record capture only.
+    Raw,
+    /// Derived from rustls-only metadata fallback.
+    Rustls,
+    /// Merged from raw TLS capture and rustls certificate metadata.
+    Merged,
+}
+
+/// Coarse-grained TLS response behavior captured per SNI.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct TlsBehaviorProfile {
+    /// Number of ChangeCipherSpec records observed before encrypted flight.
+    #[serde(default = "default_change_cipher_spec_count")]
+    pub change_cipher_spec_count: u8,
+    /// Sizes of the primary encrypted flight records carrying cert-like payload.
+    #[serde(default)]
+    pub app_data_record_sizes: Vec<usize>,
+    /// Sizes of small tail ApplicationData records that look like tickets.
+    #[serde(default)]
+    pub ticket_record_sizes: Vec<usize>,
+    /// Source of this behavior profile.
+    #[serde(default)]
+    pub source: TlsProfileSource,
+}
+
+fn default_change_cipher_spec_count() -> u8 {
+    1
+}
+
+impl Default for TlsBehaviorProfile {
+    fn default() -> Self {
+        Self {
+            change_cipher_spec_count: default_change_cipher_spec_count(),
+            app_data_record_sizes: Vec::new(),
+            ticket_record_sizes: Vec::new(),
+            source: TlsProfileSource::Default,
+        }
+    }
+}
+
 /// Cached data per SNI used by the emulator.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct CachedTlsData {
@@ -48,6 +95,8 @@ pub struct CachedTlsData {
     pub cert_payload: Option<TlsCertPayload>,
     pub app_data_records_sizes: Vec<usize>,
     pub total_app_data_len: usize,
+    #[serde(default)]
+    pub behavior_profile: TlsBehaviorProfile,
     #[serde(default = "now_system_time", skip_serializing, skip_deserializing)]
     pub fetched_at: SystemTime,
     pub domain: String,
@@ -63,6 +112,40 @@ pub struct TlsFetchResult {
     pub server_hello_parsed: ParsedServerHello,
     pub app_data_records_sizes: Vec<usize>,
     pub total_app_data_len: usize,
+    #[serde(default)]
+    pub behavior_profile: TlsBehaviorProfile,
     pub cert_info: Option<ParsedCertificateInfo>,
     pub cert_payload: Option<TlsCertPayload>,
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn cached_tls_data_deserializes_without_behavior_profile() {
+        let json = r#"
+        {
+            "server_hello_template": {
+                "version": [3, 3],
+                "random": [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
+                "session_id": [],
+                "cipher_suite": [19, 1],
+                "compression": 0,
+                "extensions": []
+            },
+            "cert_info": null,
+            "cert_payload": null,
+            "app_data_records_sizes": [1024],
+            "total_app_data_len": 1024,
+            "domain": "example.com"
+        }
+        "#;
+
+        let cached: CachedTlsData = serde_json::from_str(json).unwrap();
+        assert_eq!(cached.behavior_profile.change_cipher_spec_count, 1);
+        assert!(cached.behavior_profile.app_data_record_sizes.is_empty());
+        assert!(cached.behavior_profile.ticket_record_sizes.is_empty());
+        assert_eq!(cached.behavior_profile.source, TlsProfileSource::Default);
+    }
+}