fix(webrtc): use public STUN by default (#427)

## Summary

- disable the built-in SyncTV STUN server by default across application,
Compose, image, environment, and Helm configuration
- default `webrtc.externalIceServers` to Cloudflare and Google public
STUN endpoints while preserving persisted overrides and explicit `[]`
- update deployment validation, tests, examples, and English/Chinese
documentation

Tailscale is not included because it publishes STUN endpoints through
its dynamic DERP map and does not provide a stable general-purpose
hostname suitable for this default.

## Testing

- `cargo fmt --all -- --check`
- `cargo test -p synctv-core --test global_settings_registry_tests`
- `cargo test -p synctv-core
test_runtime_settings_default_to_public_stun_servers`
- `cargo test -p synctv default_webrtc_config_disables_builtin_stun`
- `cargo check --workspace --all-targets`
- `bash scripts/validate-helm.sh`
- Compose configuration rendering
- `npm run validate:content`
- `npm run check`
- `git diff --check`

.env.synctv.example

@@ -236,7 +236,9 @@ SYNCTV_WEBRTC_LOGGING_COLOR=auto
 
 SYNCTV_WEBRTC_MODE=peer_to_peer
 SYNCTV_WEBRTC_STUN_PORT=3478
-SYNCTV_WEBRTC_ENABLE_BUILTIN_STUN=true
+SYNCTV_WEBRTC_ENABLE_BUILTIN_STUN=false
+# Clients use Cloudflare and Google public STUN servers by default. Enable the
+# built-in server only when this deployment should provide STUN.
 # Built-in STUN needs a client-reachable public ip:port or DNS name:port.
 # Do not set this to a Pod IP or ClusterIP Service IP.
 # SYNCTV_WEBRTC_STUN_EXTERNAL_ADDR=stun.example.com:3478

Dockerfile

@@ -110,8 +110,7 @@ RUN command -v synctv && synctv --version
 # 50051: dedicated cluster gRPC
 # 9090: internal Prometheus metrics listener
 # 1935: RTMP (livestream)
-# 3478/udp: STUN (WebRTC)
-EXPOSE 8080 8081 50051 9090 1935 3478/udp
+EXPOSE 8080 8081 50051 9090 1935
 
 # Health check against the HTTP health endpoint
 HEALTHCHECK --interval=30s --timeout=5s --start-period=30s --retries=3 \

docker-compose.yml

@@ -47,7 +47,6 @@ services:
     ports:
       - "8080:8080"
       - "1935:1935"
-      - "3478:3478/udp"
     depends_on:
       postgres:
         condition: service_healthy

docs/src/content/docs/configuration/full-example.mdx

@@ -395,7 +395,7 @@ media_providers:
 
 webrtc:
   mode: "peer_to_peer"
-  enable_builtin_stun: true
+  enable_builtin_stun: false
   stun_port: 3478
   stun_host: "0.0.0.0"
   stun_external_addr: ""

docs/src/content/docs/configuration/webrtc.mdx

@@ -42,7 +42,7 @@ webrtc:
 
 STUN 帮助客户端发现自己的公网映射地址，是 NAT 穿透的一部分。
 
-关闭场景：
+仅当此 SyncTV 部署需要提供 STUN，且客户端能够访问其 UDP 端口时开启。以下场景保持关闭：
 
 - 你使用外部 STUN/TURN。
 - 当前部署环境不能暴露 UDP 端口。
@@ -52,9 +52,9 @@ STUN 帮助客户端发现自己的公网映射地址，是 NAT 穿透的一部
 
 默认值：`3478`。
 
-这是 STUN 常用端口。
+这是 STUN 常用端口，仅在启用内置 STUN 时监听。
 
-Kubernetes 或云服务器上要确保 UDP 3478 能被客户端访问。
+启用内置 STUN 后，Kubernetes 或云服务器上要确保 UDP 3478 能被客户端访问。
 
 ## `webrtc.stun_host`
 
@@ -103,11 +103,19 @@ webrtc:
 webrtc.external_ice_servers
 ```
 
-值是 ICE server 对象数组，例如：
+默认使用 Cloudflare 和 Google 的公开 STUN 服务：
+
+```json
+[
+  { "urls": ["stun:stun.cloudflare.com:3478"] },
+  { "urls": ["stun:stun.l.google.com:19302"] }
+]
+```
+
+修改此运行时设置会替换默认列表，设置为 `[]` 可禁用全部外部 ICE server。TURN server 使用相同的数据格式：
 
 ```json
 [
-  { "urls": ["stun:stun.l.google.com:19302"] },
   {
     "urls": ["turn:turn.example.com:3478"],
     "username": "user",
@@ -139,7 +147,7 @@ webrtc.external_ice_servers
 如果 WebRTC 连接失败，按顺序检查：
 
 1. 客户端是否能访问 SyncTV HTTP/gRPC API。
-2. UDP 3478 是否开放。
+2. 启用内置 STUN 时，UDP 3478 是否开放。
 3. `stun_external_addr` 是否是客户端可达地址。
    这个地址不能是 Pod IP、ClusterIP、回环地址或私网地址，除非你完全使用外部 ICE/TURN 并关闭内置 STUN。
 4. 反向代理是否只代理了 HTTP，而没有开放 UDP。

docs/src/content/docs/en/configuration/full-example.mdx

@@ -395,7 +395,7 @@ media_providers:
 
 webrtc:
   mode: "peer_to_peer"
-  enable_builtin_stun: true
+  enable_builtin_stun: false
   stun_port: 3478
   stun_host: "0.0.0.0"
   stun_external_addr: ""

docs/src/content/docs/en/configuration/webrtc.mdx

@@ -33,11 +33,11 @@ webrtc:
 
 ## Built-In STUN
 
-`webrtc.enable_builtin_stun` default: `true`.
+`webrtc.enable_builtin_stun` default: `false`.
 
 STUN helps clients discover their public mapped address for NAT traversal.
 
-Disable it when:
+Enable the built-in server only when this SyncTV deployment should provide STUN and clients can reach its UDP port. Keep it disabled when:
 
 - You use external STUN/TURN infrastructure.
 - The deployment cannot expose UDP.
@@ -92,11 +92,19 @@ External ICE servers are managed through runtime settings, not static YAML:
 webrtc.external_ice_servers
 ```
 
-Value format:
+The default uses public STUN services from Cloudflare and Google:
+
+```json
+[
+  { "urls": ["stun:stun.cloudflare.com:3478"] },
+  { "urls": ["stun:stun.l.google.com:19302"] }
+]
+```
+
+Set this runtime setting to replace the defaults. Use `[]` to disable all external ICE servers. TURN servers use the same value format:
 
 ```json
 [
-  { "urls": ["stun:stun.l.google.com:19302"] },
   {
     "urls": ["turn:turn.example.com:3478"],
     "username": "user",

docs/src/content/docs/en/install/docker-compose.mdx

@@ -79,7 +79,7 @@ The HTTP API is available at `http://localhost:8080`. On the first startup with
 
 Docker Compose loads the required `.env.postgres`, `.env.redis`, and `.env.synctv` files through `env_file`: PostgreSQL reads database variables, Redis reads `REDIS_PASSWORD`, and SyncTV reads `SYNCTV_*` application settings. The Compose file also fixes `SYNCTV_DATA_DIR` to `/data` so runtime data stays on the named volume. Reuse the same files across restarts, new shells, host reboots, and upgrades. A missing file causes `docker compose config` to fail immediately.
 
-The production Compose file uses the `latest` image and fixed host ports for HTTP 8080, RTMP 1935, and STUN 3478/udp. Container-only health port `8081` and metrics port `9090` are not published by the default Compose file.
+The production Compose file uses the `latest` image and fixed host ports for HTTP 8080 and RTMP 1935. The built-in STUN server is disabled by default. Container-only health port `8081` and metrics port `9090` are not published by the default Compose file.
 
 ## Volumes
 
@@ -106,10 +106,11 @@ Host mappings and container listeners are managed separately:
 | --- | --- | --- |
 | `8080` | `8080` | HTTP REST + public gRPC |
 | `1935` | `1935` | RTMP |
-| `3478/udp` | `3478/udp` | STUN |
 | No host mapping | `8081` | liveness/readiness for the container healthcheck |
 | No host mapping | `9090` | Prometheus metrics for a collector on the container network |
 
+To host the built-in STUN server, set `SYNCTV_WEBRTC_ENABLE_BUILTIN_STUN=true`, configure a client-reachable `SYNCTV_WEBRTC_STUN_EXTERNAL_ADDR`, and add `3478:3478/udp` to the SyncTV service's `ports` list.
+
 When a host port is already in use, change the host mapping in the Compose file and run `docker compose config` again.
 
 ## Backups

docs/src/content/docs/en/reference/configuration-index.mdx

@@ -344,7 +344,7 @@ file_storage:
 | `media_providers.emby.request_timeout_seconds` | seconds | `30` | Local Emby/Jellyfin provider request timeout |
 | `media_providers.emby.connect_timeout_seconds` | seconds | `10` | Local Emby/Jellyfin provider connection timeout |
 | `webrtc.mode` | `signaling_only` or `peer_to_peer` | `peer_to_peer` | WebRTC operating mode |
-| `webrtc.enable_builtin_stun` | boolean | `true` | Enable built-in STUN |
+| `webrtc.enable_builtin_stun` | boolean | `false` | Enable built-in STUN |
 | `webrtc.stun_port` | port | `3478` | STUN port |
 | `webrtc.stun_host` | IP/listen address | `0.0.0.0` | STUN listen address |
 | `webrtc.stun_external_addr` | string | `""` | STUN external address announced to clients |

docs/src/content/docs/en/reference/runtime-settings.mdx

@@ -189,10 +189,10 @@ Optional configuration is updated through its FieldMask path, for example `{"set
 
 | Key | Type | Default | Validation | Meaning |
 | --- | --- | --- | --- | --- |
-| `webrtc.externalIceServers` | JSON/string structure | `[]` | Valid ICE server array | External ICE servers returned to native clients |
+| `webrtc.externalIceServers` | JSON/string structure | Cloudflare and Google public STUN | Valid ICE server array | External ICE servers returned to native clients |
 | `webrtc.maxVoiceParticipantsPerRoom` | u32 | `8` | `2..=32` | Maximum simultaneous voice Mesh participants per room |
 
-The external list is empty by default. When built-in STUN is enabled and has a client-reachable advertised address, the server adds it to the ICE servers returned to clients. Built-in STUN listener configuration is startup configuration. See [WebRTC Configuration](../../configuration/webrtc/).
+The default value is `[{"urls":["stun:stun.cloudflare.com:3478"]},{"urls":["stun:stun.l.google.com:19302"]}]`. Updating the setting replaces this list; use `[]` to disable all external ICE servers. When built-in STUN is enabled and has a client-reachable advertised address, the server also adds it to the ICE servers returned to clients. Built-in STUN listener configuration is startup configuration. See [WebRTC Configuration](../../configuration/webrtc/).
 
 The voice limit is read dynamically for every join. Lowering it blocks subsequent joins while preserving existing calls; leaving or disconnecting releases a slot immediately. Multi-replica deployments coordinate room slots atomically through Redis.
 

docs/src/content/docs/install/docker-compose.mdx

@@ -79,7 +79,7 @@ HTTP API 使用 `http://localhost:8080`。首次启动数据库为空时，root
 
 Docker Compose 通过 `env_file` 分别加载必需的 `.env.postgres`、`.env.redis` 和 `.env.synctv`：PostgreSQL 读取数据库变量，Redis 读取 `REDIS_PASSWORD`，SyncTV 读取 `SYNCTV_*` 应用配置。Compose 文件另外固定将 `SYNCTV_DATA_DIR` 设置为 `/data`，让运行数据写入命名卷。重启、换 shell、服务器重启或升级时都应复用同一组环境文件。缺少任一文件时，`docker compose config` 会直接失败。
 
-生产 Compose 文件固定使用 `latest` 镜像以及 HTTP 8080、RTMP 1935、STUN 3478/udp 宿主机端口。容器内的健康端口 `8081`、metrics 端口 `9090` 不会被默认 Compose 文件映射到宿主机。
+生产 Compose 文件固定使用 `latest` 镜像以及 HTTP 8080、RTMP 1935 宿主机端口。内置 STUN 默认关闭。容器内的健康端口 `8081`、metrics 端口 `9090` 不会被默认 Compose 文件映射到宿主机。
 
 ## 数据卷
 
@@ -106,10 +106,11 @@ environment:
 | --- | --- | --- |
 | `8080` | `8080` | HTTP REST + public gRPC |
 | `1935` | `1935` | RTMP |
-| `3478/udp` | `3478/udp` | STUN |
 | 无宿主机映射 | `8081` | liveness/readiness，供容器 healthcheck 使用 |
 | 无宿主机映射 | `9090` | Prometheus metrics，供容器网络内的 Prometheus 抓取 |
 
+需要自行提供内置 STUN 时，在 `.env.synctv` 中设置 `SYNCTV_WEBRTC_ENABLE_BUILTIN_STUN=true` 和客户端可达的 `SYNCTV_WEBRTC_STUN_EXTERNAL_ADDR`，并在 SyncTV 服务的 `ports` 列表中添加 `3478:3478/udp`。
+
 宿主机端口冲突时，修改 Compose 文件中的宿主机端口映射并重新执行 `docker compose config`。
 
 ## 备份

docs/src/content/docs/reference/configuration-index.mdx

@@ -344,7 +344,7 @@ file_storage:
 | `media_providers.emby.request_timeout_seconds` | 秒数 | `30` | 本地 Emby/Jellyfin provider 请求总超时 |
 | `media_providers.emby.connect_timeout_seconds` | 秒数 | `10` | 本地 Emby/Jellyfin provider 建连超时 |
 | `webrtc.mode` | `signaling_only` 或 `peer_to_peer` | `peer_to_peer` | WebRTC 工作模式 |
-| `webrtc.enable_builtin_stun` | 布尔值 | `true` | 是否启用内置 STUN |
+| `webrtc.enable_builtin_stun` | 布尔值 | `false` | 是否启用内置 STUN |
 | `webrtc.stun_port` | 端口 | `3478` | STUN 端口 |
 | `webrtc.stun_host` | IP/监听地址 | `0.0.0.0` | STUN 监听地址 |
 | `webrtc.stun_external_addr` | 字符串 | `""` | 对客户端公布的 STUN 外部地址 |

docs/src/content/docs/reference/runtime-settings.mdx

@@ -189,10 +189,10 @@ SOCKS5 代理 URL 只包含 scheme、host 和 port。代理认证信息位于 `s
 
 | Key | 类型 | 默认值 | 校验 | 说明 |
 | --- | --- | --- | --- | --- |
-| `webrtc.externalIceServers` | JSON/字符串结构 | `[]` | 有效 ICE server 数组 | 返回给原生客户端的外部 ICE servers |
+| `webrtc.externalIceServers` | JSON/字符串结构 | Cloudflare 和 Google 公开 STUN | 有效 ICE server 数组 | 返回给原生客户端的外部 ICE servers |
 | `webrtc.maxVoiceParticipantsPerRoom` | u32 | `8` | `2..=32` | 每个房间同时加入语音通话的 Mesh 参与者上限 |
 
-外部列表默认值为空。内置 STUN 启用且具有客户端可达的公布地址时，服务端会将它加入返回给客户端的 ICE servers。内置 STUN 监听端口、host、candidate 过滤等启动配置见 [WebRTC 配置](../../configuration/webrtc/)。
+默认值为 `[{"urls":["stun:stun.cloudflare.com:3478"]},{"urls":["stun:stun.l.google.com:19302"]}]`。更新此设置会替换该列表；设置为 `[]` 可禁用全部外部 ICE server。内置 STUN 启用且具有客户端可达的公布地址时，服务端也会将它加入返回给客户端的 ICE servers。内置 STUN 监听端口、host、candidate 过滤等启动配置见 [WebRTC 配置](../../configuration/webrtc/)。
 
 语音人数上限在每次加入时动态读取。降低上限会阻止后续参与者加入，当前通话连接保持；离开或断开连接会立即释放席位。多副本部署通过 Redis 原子协调房间席位。
 

helm/synctv/README.md

@@ -568,7 +568,7 @@ alerting:
               |  HTTP API:  8080     |
               |  gRPC:      8080     |
               |  RTMP:      1935     |
-              |  STUN:      3478/udp |
+              |  STUN:      3478/udp | (optional)
               +----+----------+------+
                    ^          ^
                    |          |

helm/synctv/values.yaml

@@ -565,7 +565,7 @@ config:
   webrtc:
     ## Allowed values: signaling_only, peer_to_peer
     mode: "peer_to_peer"
-    enableBuiltinStun: true
+    enableBuiltinStun: false
     stunPort: 3478
     stunHost: "0.0.0.0"
     ## Public client-reachable STUN address, e.g. "stun.example.com:3478"

scripts/validate-helm.sh

@@ -570,6 +570,7 @@ assert_pdb_field_absent "$tmp_dir/pdb-legacy-min-available.yaml" maxUnavailable
 
 if helm template synctv "$chart_dir" \
   --namespace "$namespace" \
+  --set config.webrtc.enableBuiltinStun=true \
   --set stunService.enabled=true \
   --set config.webrtc.stunExternalAddr=203.0.113.10:3478 \
   >"$tmp_dir/clusterip-stun.yaml" 2>"$tmp_dir/clusterip-stun.err"; then
@@ -578,6 +579,7 @@ fi
 
 helm template synctv "$chart_dir" \
   --namespace "$namespace" \
+  --set config.webrtc.enableBuiltinStun=true \
   --set stunService.enabled=true \
   --set stunService.type=LoadBalancer \
   --set config.webrtc.stunExternalAddr=203.0.113.10:3478 \

synctv-api/tests/webrtc_integration_test.rs

@@ -50,7 +50,7 @@ impl Default for Config {
             server: ServerConfig::default(),
             webrtc: WebRTCConfig {
                 mode: WebRTCMode::PeerToPeer,
-                enable_builtin_stun: true,
+                enable_builtin_stun: false,
                 stun_port: 3478,
                 stun_host: "0.0.0.0".to_string(),
                 stun_external_addr: String::new(),

synctv-core/src/service/global_settings.rs

@@ -321,7 +321,7 @@ setting!(
     ExternalIceServersSetting,
     IceServerList,
     "webrtc.external_ice_servers",
-    IceServerList::new()
+    IceServerList::public_stun_defaults()
 );
 setting!(
     MaxVoiceParticipantsPerRoomSetting,
@@ -1468,6 +1468,27 @@ mod tests {
         setting
     }
 
+    #[test]
+    fn test_runtime_settings_default_to_public_stun_servers() {
+        let store = RuntimeSettingsStore::new_for_tests();
+        let settings = ok(store.runtime_settings(), "runtime settings should load");
+
+        assert_eq!(
+            settings.webrtc.external_ice_servers,
+            IceServerList::public_stun_defaults()
+        );
+
+        ok(
+            store
+                .webrtc
+                .external_ice_servers
+                .set_for_test(&IceServerList::new()),
+            "external ICE servers should update",
+        );
+        let settings = ok(store.runtime_settings(), "runtime settings should reload");
+        assert!(settings.webrtc.external_ice_servers.0.is_empty());
+    }
+
     #[test]
     fn test_runtime_settings_reads_complete_storage_generations() {
         let store = Arc::new(RuntimeSettingsStore::new_for_tests());

synctv-core/src/service/global_settings/types.rs

@@ -320,6 +320,14 @@ impl IceServerList {
     pub fn new() -> Self {
         Self(Vec::new())
     }
+
+    #[must_use]
+    pub fn public_stun_defaults() -> Self {
+        Self(vec![
+            ConfiguredIceServer::new(vec!["stun:stun.cloudflare.com:3478".to_string()]),
+            ConfiguredIceServer::new(vec!["stun:stun.l.google.com:19302".to_string()]),
+        ])
+    }
 }
 
 impl Default for IceServerList {

synctv-core/tests/global_settings_registry_tests.rs

@@ -35,10 +35,15 @@ fn test_room_password_policy_parse_and_display() {
 }
 
 #[test]
-fn test_external_ice_server_list_defaults_empty_and_accepts_custom_servers() {
+fn test_external_ice_server_list_supports_public_defaults_and_custom_servers() {
     let list = IceServerList::new();
     assert!(list.0.is_empty());
 
+    let defaults = IceServerList::public_stun_defaults();
+    assert_eq!(defaults.0.len(), 2);
+    assert_eq!(defaults.0[0].urls, ["stun:stun.cloudflare.com:3478"]);
+    assert_eq!(defaults.0[1].urls, ["stun:stun.l.google.com:19302"]);
+
     let custom = IceServerList(vec![
         ConfiguredIceServer::new(vec!["stun:custom1.example.com:19302".to_string()]),
         ConfiguredIceServer::new(vec![

synctv.example.yaml

@@ -775,13 +775,14 @@ webauthn:
 #
 # WebRTC supports 2 operation modes:
 #   - signaling_only: Pure signaling relay without ICE bootstrap
-#   - peer_to_peer:   P2P with built-in STUN plus optional external ICE servers
+#   - peer_to_peer:   P2P with public ICE servers and optional built-in STUN
 
 webrtc:
   mode: "peer_to_peer"
 
   # --- Built-in STUN Server ---
-  enable_builtin_stun: true
+  # Disabled by default. Enable only when this deployment should host STUN.
+  enable_builtin_stun: false
   stun_port: 3478
   stun_host: "0.0.0.0"
   # External address for STUN reflexive candidates. In K8s/NAT, set this to
@@ -801,7 +802,7 @@ webrtc:
   # --- External ICE Servers ---
   # Configured dynamically via the settings API (no restart required):
   #   "webrtc.external_ice_servers" - JSON array of ICE server objects, e.g.:
-  #       [{"urls":["stun:stun.example.com:3478"]},{"urls":["turn:turn.example.com:3478"],"username":"user","credential":"pass"}]
+  #       [{"urls":["stun:stun.cloudflare.com:3478"]},{"urls":["stun:stun.l.google.com:19302"]}]
 
   # ============================================================================
   # Dynamic ICE Servers Configuration
@@ -811,7 +812,8 @@ webrtc:
   #
   # Setting key: "webrtc.external_ice_servers"
   # Value: JSON array of ICE server objects
-  #   Default: [] (the built-in STUN server is used)
+  # Default: Cloudflare and Google public STUN servers shown above.
+  # Set [] to disable all external ICE servers.
   #
   # Changes take effect immediately without restarting the server.
 

synctv/src/app.rs

@@ -2101,10 +2101,7 @@ mod tests {
             chat: crate::app_config::ChatConfig::default(),
             webauthn: WebAuthnConfig::default(),
             media_providers: MediaProvidersConfig::default(),
-            webrtc: WebRTCConfig {
-                stun_external_addr: "203.0.113.1:3478".to_string(),
-                ..WebRTCConfig::default()
-            },
+            webrtc: WebRTCConfig::default(),
             connection_limits: ConnectionLimitsConfig::default(),
             bootstrap: BootstrapConfig {
                 create_root_user: false,

synctv/src/app_config/mod.rs

@@ -1316,7 +1316,7 @@ impl Default for WebRTCConfig {
     fn default() -> Self {
         Self {
             mode: WebRTCMode::PeerToPeer,
-            enable_builtin_stun: true,
+            enable_builtin_stun: false,
             stun_port: 3478,
             stun_host: "0.0.0.0".to_string(),
             stun_external_addr: String::new(),
@@ -1791,3 +1791,13 @@ impl Default for AppConfig {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::WebRTCConfig;
+
+    #[test]
+    fn default_webrtc_config_disables_builtin_stun() {
+        assert!(!WebRTCConfig::default().enable_builtin_stun);
+    }
+}

synctv/tests/cluster_startup_failure_tests.rs

@@ -155,10 +155,7 @@ fn cluster_test_config() -> Config {
         chat: ChatConfig::default(),
         webauthn: WebAuthnConfig::default(),
         media_providers: MediaProvidersConfig::default(),
-        webrtc: WebRTCConfig {
-            stun_external_addr: "203.0.113.1:3478".to_string(),
-            ..WebRTCConfig::default()
-        },
+        webrtc: WebRTCConfig::default(),
         connection_limits: ConnectionLimitsConfig::default(),
         bootstrap: BootstrapConfig {
             create_root_user: true,