feat: add Windows UDP broadcast relay (#2222)

This may helps games to find rooms in virtual network.

- add opt-in Windows UDP broadcast relay config flag and CLI/env plumbing
- capture local UDP broadcasts with Windows raw sockets, normalize packets, and inject them via PeerManager

easytier-web/frontend-lib/src/components/Config.vue

@@ -99,6 +99,7 @@ const bool_flags: BoolFlag[] = [
   { field: 'disable_encryption', help: 'disable_encryption_help' },
   { field: 'disable_tcp_hole_punching', help: 'disable_tcp_hole_punching_help' },
   { field: 'disable_udp_hole_punching', help: 'disable_udp_hole_punching_help' },
+  { field: 'enable_udp_broadcast_relay', help: 'enable_udp_broadcast_relay_help' },
   { field: 'disable_upnp', help: 'disable_upnp_help' },
   { field: 'disable_sym_hole_punching', help: 'disable_sym_hole_punching_help' },
   { field: 'enable_magic_dns', help: 'enable_magic_dns_help' },

easytier-web/frontend-lib/src/locales/cn.yaml

@@ -160,6 +160,9 @@ disable_tcp_hole_punching_help: 禁用TCP打洞功能
 disable_udp_hole_punching: 禁用UDP打洞
 disable_udp_hole_punching_help: 禁用UDP打洞功能
 
+enable_udp_broadcast_relay: UDP 广播中继
+enable_udp_broadcast_relay_help: "仅 Windows：捕获物理网卡上的本机 UDP 广播包并转发给 EasyTier 对等节点，帮助局域网游戏发现房间。需要管理员权限。"
+
 disable_upnp: 禁用 UPnP
 disable_upnp_help: 禁用符合条件监听器的运行时 UPnP/NAT-PMP 端口映射；自动端口映射默认开启。
 
@@ -260,6 +263,7 @@ event:
   DhcpIpv4Conflicted: DHCP IPv4地址冲突
   PortForwardAdded: 端口转发添加
   ProxyCidrsUpdated: 子网代理CIDR更新
+  UdpBroadcastRelayStartResult: UDP广播中继启动结果
 
 web:
   login:

easytier-web/frontend-lib/src/locales/en.yaml

@@ -159,6 +159,9 @@ disable_tcp_hole_punching_help: Disable tcp hole punching
 disable_udp_hole_punching: Disable UDP Hole Punching
 disable_udp_hole_punching_help: Disable udp hole punching
 
+enable_udp_broadcast_relay: UDP Broadcast Relay
+enable_udp_broadcast_relay_help: "Windows only: capture local UDP broadcast packets from physical interfaces and forward them to EasyTier peers. Helps games to find rooms in local network. Requires administrator privileges."
+
 disable_upnp: Disable UPnP
 disable_upnp_help: Disable runtime UPnP/NAT-PMP port mapping for eligible listeners; automatic port mapping is enabled by default.
 
@@ -260,6 +263,7 @@ event:
   DhcpIpv4Conflicted: DhcpIpv4Conflicted
   PortForwardAdded: PortForwardAdded
   ProxyCidrsUpdated: ProxyCidrsUpdated
+  UdpBroadcastRelayStartResult: UDP Broadcast Relay Start Result
 
 web:
   login:

easytier-web/frontend-lib/src/types/network.ts

@@ -134,6 +134,7 @@ export interface NetworkConfig {
   disable_tcp_hole_punching?: boolean
   disable_udp_hole_punching?: boolean
   disable_upnp?: boolean
+  enable_udp_broadcast_relay?: boolean
   disable_sym_hole_punching?: boolean
 
   enable_relay_network_whitelist?: boolean
@@ -211,6 +212,7 @@ export function DEFAULT_NETWORK_CONFIG(): NetworkConfig {
     disable_tcp_hole_punching: false,
     disable_udp_hole_punching: false,
     disable_upnp: false,
+    enable_udp_broadcast_relay: false,
     disable_sym_hole_punching: false,
     enable_relay_network_whitelist: false,
     relay_network_whitelist: [],
@@ -447,4 +449,6 @@ export enum EventType {
   PortForwardAdded = 'PortForwardAdded', // PortForwardConfigPb
 
   ProxyCidrsUpdated = 'ProxyCidrsUpdated', // string[], string[]
+
+  UdpBroadcastRelayStartResult = 'UdpBroadcastRelayStartResult', // { capture_backend?: string, error?: string }
 }

easytier/locales/app.yml

@@ -184,6 +184,9 @@ core_clap:
   disable_upnp:
     en: "disable runtime UPnP/NAT-PMP port mapping for eligible listeners; automatic port mapping is enabled by default"
     zh-CN: "禁用符合条件监听器的运行时 UPnP/NAT-PMP 端口映射；自动端口映射默认开启"
+  enable_udp_broadcast_relay:
+    en: "Windows only: capture local UDP broadcast packets from physical interfaces and forward them to EasyTier peers. Helps games to find rooms in local network. Requires administrator privileges."
+    zh-CN: "仅 Windows：捕获物理网卡上的本机 UDP 广播包并转发给 EasyTier 对等节点，帮助局域网游戏发现房间。需要管理员权限。"
   relay_all_peer_rpc:
     en: "relay all peer rpc packets, even if the peer is not in the relay network whitelist. this can help peers not in relay network whitelist to establish p2p connection."
     zh-CN: "转发所有对等节点的RPC数据包，即使对等节点不在转发网络白名单中。这可以帮助白名单外网络中的对等节点建立P2P连接。"

easytier/src/arch/windows.rs

@@ -11,9 +11,8 @@ use windows::{
             NET_FW_RULE_DIR_OUT,
         },
         Networking::WinSock::{
-            IP_UNICAST_IF, IPPROTO_IP, IPPROTO_IPV6, IPV6_UNICAST_IF, SIO_UDP_CONNRESET,
-            SO_EXCLUSIVEADDRUSE, SOCKET, SOCKET_ERROR, SOL_SOCKET, WSAGetLastError, WSAIoctl,
-            htonl, setsockopt,
+            IP_UNICAST_IF, IPPROTO_IP, IPPROTO_IPV6, IPV6_UNICAST_IF, SIO_UDP_CONNRESET, SOCKET,
+            SOCKET_ERROR, WSAGetLastError, WSAIoctl, htonl, setsockopt,
         },
         System::Com::{
             CLSCTX_ALL, COINIT_MULTITHREADED, CoCreateInstance, CoInitializeEx, CoUninitialize,

easytier/src/common/config.rs

@@ -72,6 +72,7 @@ pub fn gen_default_flags() -> Flags {
         instance_recv_bps_limit: u64::MAX,
         disable_upnp: false,
         disable_relay_data: false,
+        enable_udp_broadcast_relay: false,
     }
 }
 

easytier/src/common/global_ctx.rs

@@ -77,6 +77,11 @@ pub enum GlobalCtxEvent {
 
     ProxyCidrsUpdated(Vec<cidr::Ipv4Cidr>, Vec<cidr::Ipv4Cidr>), // (added, removed)
 
+    UdpBroadcastRelayStartResult {
+        capture_backend: Option<String>,
+        error: Option<String>,
+    },
+
     CredentialChanged,
 }
 

easytier/src/common/stats_manager.rs

@@ -85,6 +85,15 @@ pub enum MetricName {
     /// Traffic packets forwarded for foreign network, forward
     TrafficPacketsForeignForwardForwarded,
 
+    /// UDP broadcast relay packets captured from the raw socket
+    UdpBroadcastRelayPacketsCaptured,
+    /// UDP broadcast relay packets ignored before forwarding
+    UdpBroadcastRelayPacketsIgnored,
+    /// UDP broadcast relay packets forwarded
+    UdpBroadcastRelayPacketsForwarded,
+    /// UDP broadcast relay packets that failed to forward
+    UdpBroadcastRelayPacketsForwardFailed,
+
     /// Compression bytes before compression
     CompressionBytesRxBefore,
     /// Compression bytes after compression
@@ -167,6 +176,19 @@ impl fmt::Display for MetricName {
                 write!(f, "traffic_packets_foreign_forward_forwarded")
             }
 
+            MetricName::UdpBroadcastRelayPacketsCaptured => {
+                write!(f, "udp_broadcast_relay_packets_captured")
+            }
+            MetricName::UdpBroadcastRelayPacketsIgnored => {
+                write!(f, "udp_broadcast_relay_packets_ignored")
+            }
+            MetricName::UdpBroadcastRelayPacketsForwarded => {
+                write!(f, "udp_broadcast_relay_packets_forwarded")
+            }
+            MetricName::UdpBroadcastRelayPacketsForwardFailed => {
+                write!(f, "udp_broadcast_relay_packets_forward_failed")
+            }
+
             MetricName::CompressionBytesRxBefore => write!(f, "compression_bytes_rx_before"),
             MetricName::CompressionBytesRxAfter => write!(f, "compression_bytes_rx_after"),
             MetricName::CompressionBytesTxBefore => write!(f, "compression_bytes_tx_before"),

easytier/src/core.rs

@@ -484,6 +484,15 @@ struct NetworkOptions {
     )]
     disable_upnp: Option<bool>,
 
+    #[arg(
+        long,
+        env = "ET_ENABLE_UDP_BROADCAST_RELAY",
+        help = t!("core_clap.enable_udp_broadcast_relay").to_string(),
+        num_args = 0..=1,
+        default_missing_value = "true"
+    )]
+    enable_udp_broadcast_relay: Option<bool>,
+
     #[arg(
         long,
         env = "ET_RELAY_ALL_PEER_RPC",
@@ -1142,6 +1151,9 @@ impl NetworkOptions {
             .disable_sym_hole_punching
             .unwrap_or(f.disable_sym_hole_punching);
         f.disable_upnp = self.disable_upnp.unwrap_or(f.disable_upnp);
+        f.enable_udp_broadcast_relay = self
+            .enable_udp_broadcast_relay
+            .unwrap_or(f.enable_udp_broadcast_relay);
         // Configure tld_dns_zone: use provided value if set
         if let Some(tld_dns_zone) = &self.tld_dns_zone {
             f.tld_dns_zone = tld_dns_zone.clone();

easytier/src/instance/mod.rs

@@ -10,3 +10,6 @@ pub mod proxy_cidrs_monitor;
 
 #[cfg(feature = "tun")]
 pub mod virtual_nic;
+
+#[cfg(any(windows, test))]
+pub(crate) mod windows_udp_broadcast;

easytier/src/instance/public_ipv6_provider.rs

@@ -1,5 +1,8 @@
-use std::{path::Path, sync::Arc};
+#[cfg(target_os = "linux")]
+use std::path::Path;
+use std::sync::Arc;
 
+#[cfg(target_os = "linux")]
 use anyhow::Context;
 use cidr::{Ipv6Cidr, Ipv6Inet};
 #[cfg(target_os = "linux")]
@@ -321,7 +324,7 @@ async fn resolve_public_ipv6_provider_runtime_state_linux(
 }
 
 async fn resolve_public_ipv6_provider_runtime_state(
-    global_ctx: &ArcGlobalCtx,
+    _global_ctx: &ArcGlobalCtx,
     config: PublicIpv6ProviderConfigSnapshot,
 ) -> PublicIpv6ProviderRuntimeState {
     if !config.provider_enabled {
@@ -331,7 +334,7 @@ async fn resolve_public_ipv6_provider_runtime_state(
     #[cfg(target_os = "linux")]
     {
         return resolve_public_ipv6_provider_runtime_state_linux(
-            global_ctx,
+            _global_ctx,
             config.configured_prefix,
         )
         .await;

easytier/src/instance/virtual_nic.rs

@@ -35,6 +35,8 @@ use tokio::{
     task::JoinSet,
 };
 use tokio_util::bytes::Bytes;
+#[cfg(target_os = "windows")]
+use tokio_util::task::AbortOnDropHandle;
 use tun::{AbstractDevice, AsyncDevice, Configuration, Layer};
 use zerocopy::{NativeEndian, NetworkEndian};
 
@@ -801,6 +803,9 @@ pub struct NicCtx {
 
     nic: Arc<Mutex<VirtualNic>>,
     tasks: JoinSet<()>,
+
+    #[cfg(target_os = "windows")]
+    windows_udp_broadcast_relay: Option<AbortOnDropHandle<()>>,
 }
 
 impl NicCtx {
@@ -819,6 +824,9 @@ impl NicCtx {
 
             nic: Arc::new(Mutex::new(VirtualNic::new(global_ctx))),
             tasks: JoinSet::new(),
+
+            #[cfg(target_os = "windows")]
+            windows_udp_broadcast_relay: None,
         }
     }
 
@@ -1005,6 +1013,31 @@ impl NicCtx {
         });
     }
 
+    #[cfg(target_os = "windows")]
+    fn start_windows_udp_broadcast_relay(&mut self, virtual_ipv4: Ipv4Inet) {
+        if !self.global_ctx.get_flags().enable_udp_broadcast_relay {
+            return;
+        }
+
+        let Some(peer_manager) = self.peer_mgr.upgrade() else {
+            tracing::warn!("peer manager is dropped, skip Windows UDP broadcast relay");
+            return;
+        };
+
+        match super::windows_udp_broadcast::start(peer_manager, virtual_ipv4) {
+            Ok(handle) => {
+                self.windows_udp_broadcast_relay = Some(handle);
+                tracing::info!("Windows UDP broadcast relay started");
+            }
+            Err(err) => {
+                tracing::warn!(
+                    ?err,
+                    "failed to start Windows UDP broadcast relay; administrator privileges are required"
+                );
+            }
+        }
+    }
+
     async fn apply_route_changes(
         ifcfg: &impl IfConfiguerTrait,
         ifname: &str,
@@ -1347,6 +1380,8 @@ impl NicCtx {
         // Assign IPv4 address if provided
         if let Some(ipv4_addr) = ipv4_addr {
             self.assign_ipv4_to_tun_device(ipv4_addr).await?;
+            #[cfg(target_os = "windows")]
+            self.start_windows_udp_broadcast_relay(ipv4_addr);
         }
 
         // Assign IPv6 address if provided

easytier/src/instance_manager.rs

@@ -474,6 +474,28 @@ fn handle_event(
                         );
                     }
 
+                    GlobalCtxEvent::UdpBroadcastRelayStartResult {
+                        capture_backend,
+                        error,
+                    } => {
+                        if let Some(error) = error {
+                            event!(
+                                warn,
+                                ?capture_backend,
+                                %error,
+                                "[{}] UDP broadcast relay start failed",
+                                instance_id
+                            );
+                        } else {
+                            event!(
+                                info,
+                                ?capture_backend,
+                                "[{}] UDP broadcast relay started",
+                                instance_id
+                            );
+                        }
+                    }
+
                     GlobalCtxEvent::CredentialChanged => {
                         event!(info, "[{}] credential changed", instance_id);
                     }

easytier/src/launcher.rs

@@ -820,6 +820,10 @@ impl NetworkConfig {
             flags.disable_relay_data = disable_relay_data;
         }
 
+        if let Some(enable_udp_broadcast_relay) = self.enable_udp_broadcast_relay {
+            flags.enable_udp_broadcast_relay = enable_udp_broadcast_relay;
+        }
+
         if let Some(disable_sym_hole_punching) = self.disable_sym_hole_punching {
             flags.disable_sym_hole_punching = disable_sym_hole_punching;
         }
@@ -995,6 +999,7 @@ impl NetworkConfig {
         result.disable_udp_hole_punching = Some(flags.disable_udp_hole_punching);
         result.disable_upnp = Some(flags.disable_upnp);
         result.disable_relay_data = Some(flags.disable_relay_data);
+        result.enable_udp_broadcast_relay = Some(flags.enable_udp_broadcast_relay);
         result.disable_sym_hole_punching = Some(flags.disable_sym_hole_punching);
         result.enable_magic_dns = Some(flags.accept_dns);
         result.mtu = Some(flags.mtu as i32);
@@ -1263,6 +1268,7 @@ mod tests {
                 flags.disable_tcp_hole_punching = rng.gen_bool(0.2);
                 flags.disable_udp_hole_punching = rng.gen_bool(0.2);
                 flags.disable_upnp = rng.gen_bool(0.2);
+                flags.enable_udp_broadcast_relay = rng.gen_bool(0.2);
                 flags.accept_dns = rng.gen_bool(0.6);
                 flags.mtu = rng.gen_range(1200..1500);
                 flags.private_mode = rng.gen_bool(0.3);

easytier/src/peers/peer_manager.rs

@@ -1569,17 +1569,26 @@ impl PeerManager {
         ipv6_addr.is_multicast() || *ipv6_addr == ipv6_inet.last_address()
     }
 
+    fn select_ipv4_broadcast_peers<'a>(
+        routes: impl IntoIterator<Item = &'a instance::Route>,
+        my_peer_id: PeerId,
+    ) -> Vec<PeerId> {
+        routes
+            .into_iter()
+            .filter_map(|route| {
+                (route.peer_id != my_peer_id && route.ipv4_addr.is_some()).then_some(route.peer_id)
+            })
+            .collect()
+    }
+
     pub async fn get_msg_dst_peer_ipv4(&self, ipv4_addr: &Ipv4Addr) -> (Vec<PeerId>, bool) {
         let mut is_exit_node = false;
         let mut dst_peers = vec![];
         if self.is_all_peers_broadcast_ipv4(ipv4_addr) {
-            dst_peers.extend(self.peers.list_routes().await.iter().filter_map(|x| {
-                if *x.key() != self.my_peer_id {
-                    Some(*x.key())
-                } else {
-                    None
-                }
-            }));
+            dst_peers.extend(Self::select_ipv4_broadcast_peers(
+                &self.peers.list_route_infos().await,
+                self.my_peer_id,
+            ));
         } else if let Some(peer_id) = self.peers.get_peer_id_by_ipv4(ipv4_addr).await {
             dst_peers.push(peer_id);
         } else if !self
@@ -2199,6 +2208,32 @@ mod tests {
         assert!(!PeerManager::should_mark_recent_traffic_for_fanout(2));
     }
 
+    fn route_with_ipv4(
+        peer_id: u32,
+        ipv4_addr: Option<std::net::Ipv4Addr>,
+    ) -> crate::proto::api::instance::Route {
+        crate::proto::api::instance::Route {
+            peer_id,
+            ipv4_addr: ipv4_addr.map(|addr| cidr::Ipv4Inet::new(addr, 24).unwrap().into()),
+            ..Default::default()
+        }
+    }
+
+    #[test]
+    fn ipv4_broadcast_peer_selection_skips_peers_without_ipv4() {
+        let routes = vec![
+            route_with_ipv4(1, Some(std::net::Ipv4Addr::new(10, 126, 126, 1))),
+            route_with_ipv4(2, None),
+            route_with_ipv4(3, Some(std::net::Ipv4Addr::new(10, 126, 126, 3))),
+            route_with_ipv4(4, None),
+        ];
+
+        assert_eq!(
+            PeerManager::select_ipv4_broadcast_peers(&routes, 3),
+            vec![1]
+        );
+    }
+
     #[test]
     fn gc_recent_traffic_removes_expired_and_connected_entries() {
         let stale_peer = 1;

easytier/src/proto/api_manage.proto

@@ -100,6 +100,7 @@ message NetworkConfig {
   optional bool ipv6_public_addr_auto = 63;
   optional string ipv6_public_addr_prefix = 64;
   optional bool disable_relay_data = 65;
+  optional bool enable_udp_broadcast_relay = 66;
 }
 
 message PortForwardConfig {

easytier/src/proto/common.proto

@@ -76,6 +76,7 @@ message FlagsInConfig {
   uint64 instance_recv_bps_limit = 39;
   bool disable_upnp = 40;
   bool disable_relay_data = 41;
+  bool enable_udp_broadcast_relay = 42;
 }
 
 message RpcDescriptor {