v25.17.4

changelog.md

@@ -1,5 +1,65 @@
 # Changelog
 
+## 2026-03-20 - 25.17.4 - fix(rustproxy-http)
+prevent HTTP/3 response body streaming from hanging on backend completion
+
+- extract and track Content-Length before consuming the response body
+- stop the HTTP/3 body loop when the stream reports end-of-stream or the expected byte count has been sent
+- add a per-frame idle timeout to avoid indefinite waits on stalled or close-delimited backend bodies
+
+## 2026-03-20 - 25.17.3 - fix(repository)
+no changes detected
+
+
+## 2026-03-20 - 25.17.2 - fix(rustproxy-http)
+enable TLS connections for HTTP/3 upstream requests when backend re-encryption or TLS is configured
+
+- Pass backend TLS client configuration into the HTTP/3 request handler.
+- Detect TLS-required upstream targets using route and target TLS settings before connecting.
+- Build backend request URIs with the correct http or https scheme to match the upstream connection.
+
+## 2026-03-20 - 25.17.1 - fix(rustproxy-routing)
+allow QUIC UDP TLS connections without SNI to match domain-restricted routes
+
+- Exempts UDP transport from the no-SNI rejection logic because QUIC encrypts the TLS ClientHello and SNI is unavailable at accept time
+- Adds regression tests to confirm QUIC route matching succeeds without SNI while TCP TLS without SNI remains rejected
+
+## 2026-03-19 - 25.17.0 - feat(rustproxy-passthrough)
+add PROXY protocol v2 client IP handling for UDP and QUIC listeners
+
+- propagate trusted proxy IP configuration into UDP and QUIC listener managers
+- extract and preserve real client addresses from PROXY protocol v2 headers for HTTP/3 and QUIC stream handling
+- apply rate limiting, session limits, routing, and metrics using the resolved client IP while preserving correct proxy return-path routing
+
+## 2026-03-19 - 25.16.3 - fix(rustproxy)
+upgrade fallback UDP listeners to QUIC when TLS certificates become available
+
+- Rebuild and apply QUIC TLS configuration during route and certificate updates instead of only when adding new UDP ports.
+- Add logic to drain UDP sessions, stop raw fallback listeners, and start QUIC endpoints on existing ports once TLS is available.
+- Retry QUIC endpoint creation during upgrade and fall back to rebinding raw UDP if the upgrade cannot complete.
+
+## 2026-03-19 - 25.16.2 - fix(rustproxy-http)
+cache backend Alt-Svc only from original upstream responses during protocol auto-detection
+
+- Moves Alt-Svc discovery into streaming response construction so it reads backend headers before response filters inject client-facing Alt-Svc values
+- Stores the protocol cache key in connection activity during auto-detect mode and clears it after HTTP/3 connection failure to avoid re-caching failed H3 routes
+- Prevents fallback requests from reintroducing stale or self-injected Alt-Svc entries that could cause repeated H3 retry loops
+
+## 2026-03-19 - 25.16.1 - fix(http-proxy)
+avoid repeated HTTP/3 recaching after QUIC fallback and document backend protocol selection
+
+- Suppress Alt-Svc HTTP/3 recaching after a failed QUIC backend connection to prevent repeated H3 timeout fallback loops
+- Force an ALPN probe on TCP fallback so auto detection correctly reselects HTTP/2 or HTTP/1.1 after H3 connection failure
+- Add README documentation for best-effort backendProtocol selection and supported protocol modes
+
+## 2026-03-19 - 25.16.0 - feat(quic,http3)
+add HTTP/3 proxy handling and hot-reload QUIC TLS configuration
+
+- initialize and wire H3ProxyService into QUIC listeners so HTTP/3 requests are handled instead of being kept as placeholder connections
+- add backend HTTP/3 support with protocol caching that stores Alt-Svc advertised H3 ports for auto-detection
+- hot-swap TLS certificates across active QUIC endpoints and require terminating TLS for QUIC route validation
+- document QUIC route setup with required TLS and ACME configuration
+
 ## 2026-03-19 - 25.15.0 - feat(readme)
 document UDP, QUIC, and HTTP/3 support in the README
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@push.rocks/smartproxy",
-  "version": "25.15.0",
+  "version": "25.17.4",
   "private": false,
   "description": "A powerful proxy package with unified route-based configuration for high traffic management. Features include SSL/TLS support, flexible routing patterns, WebSocket handling, advanced security options, and automatic ACME certificate management.",
   "main": "dist_ts/index.js",

readme.md

@@ -306,6 +306,10 @@ const quicRoute: IRouteConfig = {
       port: 8443,
       backendTransport: 'tcp'  // 👈 Translate QUIC → TCP for backend
     }],
+    tls: {
+      mode: 'terminate',
+      certificate: 'auto'     // 👈 QUIC requires TLS 1.3
+    },
     udp: {
       quic: {
         enableHttp3: true,
@@ -318,9 +322,47 @@ const quicRoute: IRouteConfig = {
   }
 };
 
-const proxy = new SmartProxy({ routes: [quicRoute] });
+const proxy = new SmartProxy({
+  acme: { email: 'ssl@example.com' },
+  routes: [quicRoute]
+});
 ```
 
+### 🚄 Best-Effort Backend Protocol (H3 > H2 > H1)
+
+SmartProxy automatically uses the **highest protocol your backend supports** for HTTP requests. The backend protocol is independent of the client protocol — a client using HTTP/1.1 can be forwarded over HTTP/3 to the backend, and vice versa.
+
+```typescript
+const route: IRouteConfig = {
+  name: 'auto-protocol',
+  match: { ports: 443, domains: 'app.example.com' },
+  action: {
+    type: 'forward',
+    targets: [{ host: 'backend', port: 8443 }],
+    tls: { mode: 'terminate', certificate: 'auto' },
+    options: {
+      backendProtocol: 'auto'  // 👈 Default — best-effort selection
+    }
+  }
+};
+```
+
+**How protocol discovery works (browser model):**
+
+1. First request → TLS ALPN probe detects H2 or H1
+2. Backend response inspected for `Alt-Svc: h3=":port"` header
+3. If H3 advertised → cached and used for subsequent requests via QUIC
+4. Graceful fallback: H3 failure → H2 → H1 with automatic cache invalidation
+
+| `backendProtocol` | Behavior |
+|---|---|
+| `'auto'` (default) | Best-effort: H3 > H2 > H1 with Alt-Svc discovery |
+| `'http1'` | Always HTTP/1.1 |
+| `'http2'` | Always HTTP/2 (hard-fail if unsupported) |
+| `'http3'` | Always HTTP/3 via QUIC (hard-fail if unsupported) |
+
+> **Note:** WebSocket upgrades always use HTTP/1.1 to the backend regardless of `backendProtocol`, since there's no performance benefit from H2/H3 Extended CONNECT for tunneled connections, and backend support is rare.
+
 ### 🔁 Dual-Stack TCP + UDP Route
 
 Listen on both TCP and UDP with a single route — handle each transport with its own handler:
@@ -769,6 +811,28 @@ interface IRouteLoadBalancing {
 }
 ```
 
+### Backend Protocol Options
+
+```typescript
+// Set on action.options
+{
+  action: {
+    type: 'forward',
+    targets: [...],
+    options: {
+      backendProtocol: 'auto' | 'http1' | 'http2' | 'http3'
+    }
+  }
+}
+```
+
+| Value | Backend Behavior |
+|-------|-----------------|
+| `'auto'` | Best-effort: discovers H3 via Alt-Svc, probes H2 via ALPN, falls back to H1 |
+| `'http1'` | Always HTTP/1.1 (no ALPN probe) |
+| `'http2'` | Always HTTP/2 (hard-fail if handshake fails) |
+| `'http3'` | Always HTTP/3 over QUIC (3s connect timeout, hard-fail if unreachable) |
+
 ### UDP & QUIC Options
 
 ```typescript

rust/crates/rustproxy-http/src/h3_service.rs

@@ -4,6 +4,7 @@
 //! and forwards them to backends using the same routing and pool infrastructure
 //! as the HTTP/1+2 proxy.
 
+use std::net::SocketAddr;
 use std::pin::Pin;
 use std::sync::Arc;
 use std::task::{Context, Poll};
@@ -35,7 +36,6 @@ pub struct H3ProxyService {
     protocol_cache: Arc<ProtocolCache>,
     #[allow(dead_code)]
     upstream_selector: UpstreamSelector,
-    #[allow(dead_code)]
     backend_tls_config: Arc<rustls::ClientConfig>,
     connect_timeout: Duration,
 }
@@ -61,13 +61,17 @@ impl H3ProxyService {
     }
 
     /// Handle an accepted QUIC connection as HTTP/3.
+    ///
+    /// If `real_client_addr` is provided (from PROXY protocol), it overrides
+    /// `connection.remote_address()` for client IP attribution.
     pub async fn handle_connection(
         &self,
         connection: quinn::Connection,
         _fallback_route: &RouteConfig,
         port: u16,
+        real_client_addr: Option<SocketAddr>,
     ) -> anyhow::Result<()> {
-        let remote_addr = connection.remote_address();
+        let remote_addr = real_client_addr.unwrap_or_else(|| connection.remote_address());
         debug!("HTTP/3 connection from {} on port {}", remote_addr, port);
 
         let mut h3_conn: h3::server::Connection<h3_quinn::Connection, Bytes> =
@@ -93,12 +97,14 @@ impl H3ProxyService {
                     let rm = self.route_manager.load();
                     let pool = Arc::clone(&self.connection_pool);
                     let metrics = Arc::clone(&self.metrics);
+                    let backend_tls = Arc::clone(&self.backend_tls_config);
                     let connect_timeout = self.connect_timeout;
                     let client_ip = client_ip.clone();
 
                     tokio::spawn(async move {
                         if let Err(e) = handle_h3_request(
-                            request, stream, port, &client_ip, &rm, &pool, &metrics, connect_timeout,
+                            request, stream, port, &client_ip, &rm, &pool, &metrics,
+                            &backend_tls, connect_timeout,
                         ).await {
                             debug!("HTTP/3 request error from {}: {}", client_ip, e);
                         }
@@ -128,6 +134,7 @@ async fn handle_h3_request(
     route_manager: &RouteManager,
     _connection_pool: &ConnectionPool,
     metrics: &MetricsCollector,
+    backend_tls_config: &Arc<rustls::ClientConfig>,
     connect_timeout: Duration,
 ) -> anyhow::Result<()> {
     let method = request.method().clone();
@@ -168,7 +175,15 @@ async fn handle_h3_request(
     let backend_port = target.port.resolve(port);
     let backend_addr = format!("{}:{}", backend_host, backend_port);
 
-    // Connect to backend via TCP HTTP/1.1 with timeout
+    // Determine if backend requires TLS (same logic as proxy_service.rs)
+    let mut use_tls = target.tls.is_some();
+    if let Some(ref tls) = route.action.tls {
+        if tls.mode == rustproxy_config::TlsMode::TerminateAndReencrypt {
+            use_tls = true;
+        }
+    }
+
+    // Connect to backend via TCP with timeout
     let tcp_stream = tokio::time::timeout(
         connect_timeout,
         tokio::net::TcpStream::connect(&backend_addr),
@@ -178,15 +193,27 @@ async fn handle_h3_request(
 
     let _ = tcp_stream.set_nodelay(true);
 
-    let io = hyper_util::rt::TokioIo::new(tcp_stream);
+    // Branch: wrap in TLS if backend requires it, then HTTP/1.1 handshake.
-    let (mut sender, conn) = hyper::client::conn::http1::handshake(io).await
+    // hyper's SendRequest<B> is NOT generic over the IO type, so both branches
-        .map_err(|e| anyhow::anyhow!("Backend handshake failed: {}", e))?;
+    // produce the same type and can be unified.
-
+    let mut sender = if use_tls {
-    tokio::spawn(async move {
+        let connector = tokio_rustls::TlsConnector::from(Arc::clone(backend_tls_config));
-        if let Err(e) = conn.await {
+        let server_name = rustls::pki_types::ServerName::try_from(backend_host.to_string())
-            debug!("Backend connection closed: {}", e);
+            .map_err(|e| anyhow::anyhow!("Invalid backend SNI '{}': {}", backend_host, e))?;
-        }
+        let tls_stream = connector.connect(server_name, tcp_stream).await
-    });
+            .map_err(|e| anyhow::anyhow!("Backend TLS handshake to {} failed: {}", backend_addr, e))?;
+        let io = hyper_util::rt::TokioIo::new(tls_stream);
+        let (sender, conn) = hyper::client::conn::http1::handshake(io).await
+            .map_err(|e| anyhow::anyhow!("Backend handshake failed: {}", e))?;
+        tokio::spawn(async move { let _ = conn.await; });
+        sender
+    } else {
+        let io = hyper_util::rt::TokioIo::new(tcp_stream);
+        let (sender, conn) = hyper::client::conn::http1::handshake(io).await
+            .map_err(|e| anyhow::anyhow!("Backend handshake failed: {}", e))?;
+        tokio::spawn(async move { let _ = conn.await; });
+        sender
+    };
 
     // Stream request body from H3 client to backend via an mpsc channel.
     // This avoids buffering the entire request body in memory.
@@ -209,7 +236,7 @@ async fn handle_h3_request(
 
     // Create a body that polls from the mpsc receiver
     let body = H3RequestBody { receiver: body_rx };
-    let backend_req = build_backend_request(&method, &backend_addr, &path, &host, &request, body)?;
+    let backend_req = build_backend_request(&method, &backend_addr, &path, &host, &request, body, use_tls)?;
 
     let response = sender.send_request(backend_req).await
         .map_err(|e| anyhow::anyhow!("Backend request failed: {}", e))?;
@@ -232,6 +259,12 @@ async fn handle_h3_request(
         h3_response = h3_response.header(name, value);
     }
 
+    // Extract content-length for body loop termination (must be before into_body())
+    let content_length: Option<u64> = response.headers()
+        .get(hyper::header::CONTENT_LENGTH)
+        .and_then(|v| v.to_str().ok())
+        .and_then(|s| s.parse().ok());
+
     // Add Alt-Svc for HTTP/3 advertisement
     let alt_svc = route.action.udp.as_ref()
         .and_then(|u| u.quic.as_ref())
@@ -252,21 +285,52 @@ async fn handle_h3_request(
 
     // Stream response body back
     use http_body_util::BodyExt;
+    use http_body::Body as _;
     let mut body = response.into_body();
     let mut total_bytes_out: u64 = 0;
-    while let Some(frame) = body.frame().await {
+
-        match frame {
+    // Per-frame idle timeout: if no frame arrives within this duration, assume
-            Ok(frame) => {
+    // the body is complete (or the backend has stalled). This prevents indefinite
+    // hangs on close-delimited bodies or when hyper's internal trailers oneshot
+    // never resolves after all data has been received.
+    const FRAME_IDLE_TIMEOUT: Duration = Duration::from_secs(30);
+
+    loop {
+        // Layer 1: If the body already knows it is finished (Content-Length
+        // bodies track remaining bytes internally), break immediately to
+        // avoid blocking on hyper's internal trailers oneshot.
+        if body.is_end_stream() {
+            break;
+        }
+
+        // Layer 3: Per-frame idle timeout safety net
+        match tokio::time::timeout(FRAME_IDLE_TIMEOUT, body.frame()).await {
+            Ok(Some(Ok(frame))) => {
                 if let Some(data) = frame.data_ref() {
                     total_bytes_out += data.len() as u64;
                     stream.send_data(Bytes::copy_from_slice(data)).await
                         .map_err(|e| anyhow::anyhow!("Failed to send H3 data: {}", e))?;
+
+                    // Layer 2: Content-Length byte count check
+                    if let Some(cl) = content_length {
+                        if total_bytes_out >= cl {
+                            break;
+                        }
+                    }
                 }
             }
-            Err(e) => {
+            Ok(Some(Err(e))) => {
                 warn!("Backend body read error: {}", e);
                 break;
             }
+            Ok(None) => break, // Body ended naturally
+            Err(_) => {
+                debug!(
+                    "H3 body frame idle timeout ({:?}) after {} bytes; finishing stream",
+                    FRAME_IDLE_TIMEOUT, total_bytes_out
+                );
+                break;
+            }
         }
     }
 
@@ -289,10 +353,12 @@ fn build_backend_request<B>(
     host: &str,
     original_request: &hyper::Request<()>,
     body: B,
+    use_tls: bool,
 ) -> anyhow::Result<hyper::Request<B>> {
+    let scheme = if use_tls { "https" } else { "http" };
     let mut req = hyper::Request::builder()
         .method(method)
-        .uri(format!("http://{}{}", backend_addr, path))
+        .uri(format!("{}://{}{}", scheme, backend_addr, path))
         .header("host", host);
 
     // Forward non-pseudo headers

rust/crates/rustproxy-http/src/protocol_cache.rs

@@ -1,8 +1,11 @@
-//! Bounded, TTL-based protocol detection cache for HTTP/2 auto-detection.
+//! Bounded, TTL-based protocol detection cache for backend protocol auto-detection.
 //!
-//! Caches the ALPN-negotiated protocol (H1 or H2) per backend endpoint and requested
+//! Caches the detected protocol (H1, H2, or H3) per backend endpoint and requested
 //! domain (host:port + requested_host). This prevents cache oscillation when multiple
-//! frontend domains share the same backend but differ in HTTP/2 support.
+//! frontend domains share the same backend but differ in protocol support.
+//!
+//! H3 detection uses the browser model: Alt-Svc headers from H1/H2 responses are
+//! parsed and cached, including the advertised H3 port (which may differ from TCP).
 
 use std::sync::Arc;
 use std::time::{Duration, Instant};
@@ -29,6 +32,14 @@ pub enum DetectedProtocol {
     H3,
 }
 
+/// Result of a protocol cache lookup.
+#[derive(Debug, Clone, Copy)]
+pub struct CachedProtocol {
+    pub protocol: DetectedProtocol,
+    /// For H3: the port advertised by Alt-Svc (may differ from TCP port).
+    pub h3_port: Option<u16>,
+}
+
 /// Key for the protocol cache: (host, port, requested_host).
 #[derive(Clone, Debug, Hash, Eq, PartialEq)]
 pub struct ProtocolCacheKey {
@@ -43,6 +54,8 @@ pub struct ProtocolCacheKey {
 struct CachedEntry {
     protocol: DetectedProtocol,
     detected_at: Instant,
+    /// For H3: the port advertised by Alt-Svc (may differ from TCP port).
+    h3_port: Option<u16>,
 }
 
 /// Bounded, TTL-based protocol detection cache.
@@ -75,11 +88,14 @@ impl ProtocolCache {
 
     /// Look up the cached protocol for a backend endpoint.
     /// Returns `None` if not cached or expired (caller should probe via ALPN).
-    pub fn get(&self, key: &ProtocolCacheKey) -> Option<DetectedProtocol> {
+    pub fn get(&self, key: &ProtocolCacheKey) -> Option<CachedProtocol> {
         let entry = self.cache.get(key)?;
         if entry.detected_at.elapsed() < PROTOCOL_CACHE_TTL {
             debug!("Protocol cache hit: {:?} for {}:{} (requested: {:?})", entry.protocol, key.host, key.port, key.requested_host);
-            Some(entry.protocol)
+            Some(CachedProtocol {
+                protocol: entry.protocol,
+                h3_port: entry.h3_port,
+            })
         } else {
             // Expired — remove and return None to trigger re-probe
             drop(entry); // release DashMap ref before remove
@@ -91,6 +107,16 @@ impl ProtocolCache {
     /// Insert a detected protocol into the cache.
     /// If the cache is at capacity, evict the oldest entry first.
     pub fn insert(&self, key: ProtocolCacheKey, protocol: DetectedProtocol) {
+        self.insert_with_h3_port(key, protocol, None);
+    }
+
+    /// Insert an H3 detection result with the Alt-Svc advertised port.
+    pub fn insert_h3(&self, key: ProtocolCacheKey, h3_port: u16) {
+        self.insert_with_h3_port(key, DetectedProtocol::H3, Some(h3_port));
+    }
+
+    /// Insert a protocol detection result with an optional H3 port.
+    fn insert_with_h3_port(&self, key: ProtocolCacheKey, protocol: DetectedProtocol, h3_port: Option<u16>) {
         if self.cache.len() >= PROTOCOL_CACHE_MAX_ENTRIES && !self.cache.contains_key(&key) {
             // Evict the oldest entry to stay within bounds
             let oldest = self.cache.iter()
@@ -103,6 +129,7 @@ impl ProtocolCache {
         self.cache.insert(key, CachedEntry {
             protocol,
             detected_at: Instant::now(),
+            h3_port,
         });
     }
 

rust/crates/rustproxy-http/src/proxy_service.rs

@@ -43,6 +43,10 @@ struct ConnActivity {
     /// increments on creation and decrements on Drop, keeping the watchdog aware that
     /// a response body is still streaming after the request handler has returned.
     active_requests: Option<Arc<AtomicU64>>,
+    /// Protocol cache key for Alt-Svc discovery. When set, `build_streaming_response`
+    /// checks the backend's original response headers for Alt-Svc before our
+    /// ResponseFilter injects its own. None when not in auto-detect mode or after H3 failure.
+    alt_svc_cache_key: Option<crate::protocol_cache::ProtocolCacheKey>,
 }
 
 /// Default upstream connect timeout (30 seconds).
@@ -58,6 +62,18 @@ const DEFAULT_WS_INACTIVITY_TIMEOUT: std::time::Duration = std::time::Duration::
 /// Default WebSocket max lifetime (24 hours).
 const DEFAULT_WS_MAX_LIFETIME: std::time::Duration = std::time::Duration::from_secs(86400);
 
+/// Timeout for QUIC (H3) backend connections. Short because UDP is often firewalled.
+const QUIC_CONNECT_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(3);
+
+/// Protocol decision for backend connection.
+#[derive(Debug)]
+enum ProtocolDecision {
+    H1,
+    H2,
+    H3 { port: u16 },
+    AlpnProbe,
+}
+
 /// RAII guard that decrements the active request counter on drop.
 /// Ensures the counter is correct even if the request handler panics.
 struct ActiveRequestGuard {
@@ -190,6 +206,9 @@ pub struct HttpProxyService {
     ws_inactivity_timeout: std::time::Duration,
     /// WebSocket maximum connection lifetime.
     ws_max_lifetime: std::time::Duration,
+    /// Shared QUIC client endpoint for outbound H3 backend connections.
+    /// Lazily initialized on first H3 backend attempt.
+    quinn_client_endpoint: Arc<quinn::Endpoint>,
 }
 
 impl HttpProxyService {
@@ -209,6 +228,7 @@ impl HttpProxyService {
             http_idle_timeout: DEFAULT_HTTP_IDLE_TIMEOUT,
             ws_inactivity_timeout: DEFAULT_WS_INACTIVITY_TIMEOUT,
             ws_max_lifetime: DEFAULT_WS_MAX_LIFETIME,
+            quinn_client_endpoint: Arc::new(Self::create_quinn_client_endpoint()),
         }
     }
 
@@ -233,6 +253,7 @@ impl HttpProxyService {
             http_idle_timeout: DEFAULT_HTTP_IDLE_TIMEOUT,
             ws_inactivity_timeout: DEFAULT_WS_INACTIVITY_TIMEOUT,
             ws_max_lifetime: DEFAULT_WS_MAX_LIFETIME,
+            quinn_client_endpoint: Arc::new(Self::create_quinn_client_endpoint()),
         }
     }
 
@@ -324,7 +345,7 @@ impl HttpProxyService {
             let cn = cancel_inner.clone();
             let la = Arc::clone(&la_inner);
             let st = start;
-            let ca = ConnActivity { last_activity: Arc::clone(&la_inner), start, active_requests: Some(Arc::clone(&ar_inner)) };
+            let ca = ConnActivity { last_activity: Arc::clone(&la_inner), start, active_requests: Some(Arc::clone(&ar_inner)), alt_svc_cache_key: None };
             async move {
                 let result = svc.handle_request(req, peer, port, cn, ca).await;
                 // Mark request end — update activity timestamp before guard drops
@@ -401,7 +422,7 @@ impl HttpProxyService {
         peer_addr: std::net::SocketAddr,
         port: u16,
         cancel: CancellationToken,
-        conn_activity: ConnActivity,
+        mut conn_activity: ConnActivity,
     ) -> Result<Response<BoxBody<Bytes, hyper::Error>>, hyper::Error> {
         let host = req.headers()
             .get("host")
@@ -645,37 +666,101 @@ impl HttpProxyService {
 
         // --- Resolve protocol decision based on backend protocol mode ---
         let is_auto_detect_mode = matches!(backend_protocol_mode, rustproxy_config::BackendProtocol::Auto);
-        let (use_h2, needs_alpn_probe) = match backend_protocol_mode {
+        let protocol_cache_key = crate::protocol_cache::ProtocolCacheKey {
-            rustproxy_config::BackendProtocol::Http1 => (false, false),
+            host: upstream.host.clone(),
-            rustproxy_config::BackendProtocol::Http2 => (true, false),
+            port: upstream.port,
-            rustproxy_config::BackendProtocol::Http3 => {
+            requested_host: host.clone(),
-                // HTTP/3 (QUIC) backend connections not yet implemented — fall back to H1
+        };
-                warn!("backendProtocol 'http3' not yet implemented, falling back to http1");
+        let protocol_decision = match backend_protocol_mode {
-                (false, false)
+            rustproxy_config::BackendProtocol::Http1 => ProtocolDecision::H1,
-            }
+            rustproxy_config::BackendProtocol::Http2 => ProtocolDecision::H2,
+            rustproxy_config::BackendProtocol::Http3 => ProtocolDecision::H3 { port: upstream.port },
             rustproxy_config::BackendProtocol::Auto => {
                 if !upstream.use_tls {
-                    // No ALPN without TLS — default to H1
+                    // No ALPN without TLS, no QUIC without TLS — default to H1
-                    (false, false)
+                    ProtocolDecision::H1
                 } else {
-                    let cache_key = crate::protocol_cache::ProtocolCacheKey {
+                    match self.protocol_cache.get(&protocol_cache_key) {
-                        host: upstream.host.clone(),
+                        Some(cached) => match cached.protocol {
-                        port: upstream.port,
+                            crate::protocol_cache::DetectedProtocol::H3 => {
-                        requested_host: host.clone(),
+                                if let Some(h3_port) = cached.h3_port {
-                    };
+                                    ProtocolDecision::H3 { port: h3_port }
-                    match self.protocol_cache.get(&cache_key) {
+                                } else {
-                        Some(crate::protocol_cache::DetectedProtocol::H2) => (true, false),
+                                    // H3 cached but no port — fall back to ALPN probe
-                        Some(crate::protocol_cache::DetectedProtocol::H1) => (false, false),
+                                    ProtocolDecision::AlpnProbe
-                        Some(crate::protocol_cache::DetectedProtocol::H3) => {
+                                }
-                            // H3 cached but we're on TCP — fall back to H2 probe
+                            }
-                            (false, true)
+                            crate::protocol_cache::DetectedProtocol::H2 => ProtocolDecision::H2,
-                        }
+                            crate::protocol_cache::DetectedProtocol::H1 => ProtocolDecision::H1,
-                        None => (false, true), // needs ALPN probe
+                        },
+                        None => ProtocolDecision::AlpnProbe,
                     }
                 }
             }
         };
 
+        // Derive legacy flags for the existing H1/H2 connection path
+        let (use_h2, mut needs_alpn_probe) = match &protocol_decision {
+            ProtocolDecision::H1 => (false, false),
+            ProtocolDecision::H2 => (true, false),
+            ProtocolDecision::H3 { .. } => (false, false), // H3 path handled separately below
+            ProtocolDecision::AlpnProbe => (false, true),
+        };
+
+        // Set Alt-Svc cache key on conn_activity so build_streaming_response can check
+        // the backend's original Alt-Svc header before ResponseFilter injects our own.
+        if is_auto_detect_mode {
+            conn_activity.alt_svc_cache_key = Some(protocol_cache_key.clone());
+        }
+
+        // --- H3 path: try QUIC connection before TCP ---
+        if let ProtocolDecision::H3 { port: h3_port } = protocol_decision {
+            let h3_pool_key = crate::connection_pool::PoolKey {
+                host: upstream.host.clone(),
+                port: h3_port,
+                use_tls: true,
+                protocol: crate::connection_pool::PoolProtocol::H3,
+            };
+
+            // Try H3 pool checkout first
+            if let Some((quic_conn, _age)) = self.connection_pool.checkout_h3(&h3_pool_key) {
+                self.metrics.backend_pool_hit(&upstream_key);
+                let result = self.forward_h3(
+                    quic_conn, parts, body, upstream_headers, &upstream_path,
+                    route_match.route, route_id, &ip_str, &h3_pool_key, domain_str, &conn_activity, &upstream_key,
+                ).await;
+                self.upstream_selector.connection_ended(&upstream_key);
+                return result;
+            }
+
+            // Try fresh QUIC connection
+            match self.connect_quic_backend(&upstream.host, h3_port).await {
+                Ok(quic_conn) => {
+                    self.metrics.backend_pool_miss(&upstream_key);
+                    self.metrics.backend_connection_opened(&upstream_key, std::time::Instant::now().elapsed());
+                    let result = self.forward_h3(
+                        quic_conn, parts, body, upstream_headers, &upstream_path,
+                        route_match.route, route_id, &ip_str, &h3_pool_key, domain_str, &conn_activity, &upstream_key,
+                    ).await;
+                    self.upstream_selector.connection_ended(&upstream_key);
+                    return result;
+                }
+                Err(e) => {
+                    warn!(backend = %upstream_key, error = %e,
+                        "H3 backend connect failed, falling back to H2/H1");
+                    // Suppress Alt-Svc caching for the fallback to prevent re-caching H3
+                    // from our own injected Alt-Svc header or a stale backend Alt-Svc
+                    conn_activity.alt_svc_cache_key = None;
+                    // Force ALPN probe on TCP fallback so we correctly detect H2 vs H1
+                    // (don't cache anything yet — let the ALPN probe decide)
+                    if is_auto_detect_mode && upstream.use_tls {
+                        needs_alpn_probe = true;
+                    }
+                    // Fall through to TCP path
+                }
+            }
+        }
+
         // --- Connection pooling: try reusing an existing connection first ---
         // For ALPN probe mode, skip pool checkout (we don't know the protocol yet)
         if !needs_alpn_probe {
@@ -870,6 +955,7 @@ impl HttpProxyService {
         };
         self.upstream_selector.connection_ended(&upstream_key);
         self.metrics.backend_connection_closed(&upstream_key);
+
         result
     }
 
@@ -1668,6 +1754,19 @@ impl HttpProxyService {
     ) -> Result<Response<BoxBody<Bytes, hyper::Error>>, hyper::Error> {
         let (resp_parts, resp_body) = upstream_response.into_parts();
 
+        // Check for Alt-Svc in the backend's ORIGINAL response headers BEFORE
+        // ResponseFilter::apply_headers runs — the filter may inject our own Alt-Svc
+        // for client-facing HTTP/3 advertisement, which must not be confused with
+        // backend-originated Alt-Svc.
+        if let Some(ref cache_key) = conn_activity.alt_svc_cache_key {
+            if let Some(alt_svc) = resp_parts.headers.get("alt-svc").and_then(|v| v.to_str().ok()) {
+                if let Some(h3_port) = parse_alt_svc_h3_port(alt_svc) {
+                    debug!(h3_port, "Backend advertises H3 via Alt-Svc");
+                    self.protocol_cache.insert_h3(cache_key.clone(), h3_port);
+                }
+            }
+        }
+
         let mut response = Response::builder()
             .status(resp_parts.status);
 
@@ -2393,6 +2492,252 @@ impl HttpProxyService {
         config.alpn_protocols = vec![b"h2".to_vec(), b"http/1.1".to_vec()];
         Arc::new(config)
     }
+
+    /// Create a shared QUIC client endpoint for outbound H3 backend connections.
+    fn create_quinn_client_endpoint() -> quinn::Endpoint {
+        let _ = rustls::crypto::ring::default_provider().install_default();
+        let mut tls_config = rustls::ClientConfig::builder()
+            .dangerous()
+            .with_custom_certificate_verifier(Arc::new(InsecureBackendVerifier))
+            .with_no_client_auth();
+        tls_config.alpn_protocols = vec![b"h3".to_vec()];
+
+        let quic_crypto = quinn::crypto::rustls::QuicClientConfig::try_from(tls_config)
+            .expect("Failed to create QUIC client crypto config");
+        let client_config = quinn::ClientConfig::new(Arc::new(quic_crypto));
+
+        let mut endpoint = quinn::Endpoint::client("0.0.0.0:0".parse().unwrap())
+            .expect("Failed to create QUIC client endpoint");
+        endpoint.set_default_client_config(client_config);
+        endpoint
+    }
+
+    /// Connect to a backend via QUIC (H3).
+    async fn connect_quic_backend(
+        &self,
+        host: &str,
+        port: u16,
+    ) -> Result<quinn::Connection, Box<dyn std::error::Error + Send + Sync>> {
+        let addr = tokio::net::lookup_host(format!("{}:{}", host, port))
+            .await?
+            .next()
+            .ok_or("DNS resolution returned no addresses")?;
+
+        let server_name = host.to_string();
+        let connecting = self.quinn_client_endpoint.connect(addr, &server_name)?;
+
+        let connection = tokio::time::timeout(QUIC_CONNECT_TIMEOUT, connecting).await
+            .map_err(|_| "QUIC connect timeout (3s)")??;
+
+        debug!("QUIC backend connection established to {}:{}", host, port);
+        Ok(connection)
+    }
+
+    /// Forward request to backend via HTTP/3 over QUIC.
+    async fn forward_h3(
+        &self,
+        quic_conn: quinn::Connection,
+        parts: hyper::http::request::Parts,
+        body: Incoming,
+        upstream_headers: hyper::HeaderMap,
+        upstream_path: &str,
+        route: &rustproxy_config::RouteConfig,
+        route_id: Option<&str>,
+        source_ip: &str,
+        pool_key: &crate::connection_pool::PoolKey,
+        domain: &str,
+        conn_activity: &ConnActivity,
+        backend_key: &str,
+    ) -> Result<Response<BoxBody<Bytes, hyper::Error>>, hyper::Error> {
+        let h3_quinn_conn = h3_quinn::Connection::new(quic_conn.clone());
+        let (mut driver, mut send_request) = match h3::client::new(h3_quinn_conn).await {
+            Ok(pair) => pair,
+            Err(e) => {
+                error!(backend = %backend_key, domain = %domain, error = %e, "H3 client handshake failed");
+                self.metrics.backend_handshake_error(backend_key);
+                return Ok(error_response(StatusCode::BAD_GATEWAY, "H3 handshake failed"));
+            }
+        };
+
+        // Spawn the h3 connection driver
+        let driver_pool = Arc::clone(&self.connection_pool);
+        let driver_pool_key = pool_key.clone();
+        let gen_holder = Arc::new(std::sync::atomic::AtomicU64::new(u64::MAX));
+        let driver_gen = Arc::clone(&gen_holder);
+        tokio::spawn(async move {
+            let close_err = std::future::poll_fn(|cx| driver.poll_close(cx)).await;
+            debug!("H3 connection driver closed: {:?}", close_err);
+            let g = driver_gen.load(std::sync::atomic::Ordering::Relaxed);
+            if g != u64::MAX {
+                driver_pool.remove_h3_if_generation(&driver_pool_key, g);
+            }
+        });
+
+        // Build the H3 request
+        let uri = hyper::Uri::builder()
+            .scheme("https")
+            .authority(domain)
+            .path_and_query(upstream_path)
+            .build()
+            .unwrap_or_else(|_| upstream_path.parse().unwrap_or_default());
+
+        let mut h3_req = hyper::Request::builder()
+            .method(parts.method.clone())
+            .uri(uri);
+
+        if let Some(headers) = h3_req.headers_mut() {
+            *headers = upstream_headers;
+        }
+
+        let h3_req = h3_req.body(()).unwrap();
+
+        // Send the request
+        let mut stream = match send_request.send_request(h3_req).await {
+            Ok(s) => s,
+            Err(e) => {
+                error!(backend = %backend_key, domain = %domain, error = %e, "H3 send_request failed");
+                self.metrics.backend_request_error(backend_key);
+                return Ok(error_response(StatusCode::BAD_GATEWAY, "H3 request failed"));
+            }
+        };
+
+        // Stream request body
+        let rid: Option<Arc<str>> = route_id.map(Arc::from);
+        let sip: Arc<str> = Arc::from(source_ip);
+
+        {
+            use http_body_util::BodyExt;
+            let mut body = body;
+            while let Some(frame) = body.frame().await {
+                match frame {
+                    Ok(frame) => {
+                        if let Some(data) = frame.data_ref() {
+                            self.metrics.record_bytes(data.len() as u64, 0, rid.as_deref(), Some(&sip));
+                            if let Err(e) = stream.send_data(Bytes::copy_from_slice(data)).await {
+                                error!(backend = %backend_key, error = %e, "H3 send_data failed");
+                                return Ok(error_response(StatusCode::BAD_GATEWAY, "H3 body send failed"));
+                            }
+                        }
+                    }
+                    Err(e) => {
+                        warn!(backend = %backend_key, error = %e, "Client body read error during H3 forward");
+                        break;
+                    }
+                }
+            }
+            // Signal end of body
+            stream.finish().await.ok();
+        }
+
+        // Read response
+        let h3_response = match stream.recv_response().await {
+            Ok(resp) => resp,
+            Err(e) => {
+                error!(backend = %backend_key, domain = %domain, error = %e, "H3 recv_response failed");
+                self.metrics.backend_request_error(backend_key);
+                return Ok(error_response(StatusCode::BAD_GATEWAY, "H3 response failed"));
+            }
+        };
+
+        // Build the response for the client
+        let status = h3_response.status();
+        let mut response = Response::builder().status(status);
+
+        if let Some(headers) = response.headers_mut() {
+            for (name, value) in h3_response.headers() {
+                let n = name.as_str();
+                // Skip hop-by-hop headers
+                if n == "transfer-encoding" || n == "connection" || n == "keep-alive" {
+                    continue;
+                }
+                headers.insert(name.clone(), value.clone());
+            }
+            ResponseFilter::apply_headers(route, headers, None);
+        }
+
+        // Stream response body back via an adapter
+        let h3_body = H3ClientResponseBody { stream };
+        let counting_body = CountingBody::new(
+            h3_body,
+            Arc::clone(&self.metrics),
+            rid,
+            Some(sip),
+            Direction::Out,
+        ).with_connection_activity(Arc::clone(&conn_activity.last_activity), conn_activity.start);
+
+        let counting_body = if let Some(ref ar) = conn_activity.active_requests {
+            counting_body.with_active_requests(Arc::clone(ar))
+        } else {
+            counting_body
+        };
+
+        let body: BoxBody<Bytes, hyper::Error> = BoxBody::new(counting_body);
+
+        // Register connection in pool on success
+        if status != StatusCode::BAD_GATEWAY {
+            let g = self.connection_pool.register_h3(pool_key.clone(), quic_conn);
+            gen_holder.store(g, std::sync::atomic::Ordering::Relaxed);
+        }
+
+        self.metrics.set_backend_protocol(backend_key, "h3");
+        Ok(response.body(body).unwrap())
+    }
+}
+
+/// Parse an Alt-Svc header value to extract the H3 port.
+/// Handles formats like `h3=":443"; ma=86400` and `h3=":8443", h2=":443"`.
+fn parse_alt_svc_h3_port(header_value: &str) -> Option<u16> {
+    for directive in header_value.split(',') {
+        let directive = directive.trim();
+        // Match h3=":<port>" or h3-29=":<port>" etc.
+        if directive.starts_with("h3=") || directive.starts_with("h3-") {
+            // Find the port in ":<port>"
+            if let Some(start) = directive.find("\":") {
+                let rest = &directive[start + 2..];
+                if let Some(end) = rest.find('"') {
+                    if let Ok(port) = rest[..end].parse::<u16>() {
+                        return Some(port);
+                    }
+                }
+            }
+        }
+    }
+    None
+}
+
+/// Response body adapter for H3 client responses.
+/// Reads data from the h3 `RequestStream` recv side and presents it as an `http_body::Body`.
+struct H3ClientResponseBody {
+    stream: h3::client::RequestStream<h3_quinn::BidiStream<Bytes>, Bytes>,
+}
+
+impl http_body::Body for H3ClientResponseBody {
+    type Data = Bytes;
+    type Error = hyper::Error;
+
+    fn poll_frame(
+        mut self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+    ) -> Poll<Option<Result<http_body::Frame<Self::Data>, Self::Error>>> {
+        // h3's recv_data is async, so we need to poll it manually.
+        // Use a small future to poll the recv_data call.
+        use std::future::Future;
+        let mut fut = Box::pin(self.stream.recv_data());
+        match fut.as_mut().poll(_cx) {
+            Poll::Ready(Ok(Some(mut buf))) => {
+                use bytes::Buf;
+                let data = Bytes::copy_from_slice(buf.chunk());
+                buf.advance(buf.remaining());
+                Poll::Ready(Some(Ok(http_body::Frame::data(data))))
+            }
+            Poll::Ready(Ok(None)) => Poll::Ready(None),
+            Poll::Ready(Err(e)) => {
+                warn!("H3 response body recv error: {}", e);
+                Poll::Ready(None)
+            }
+            Poll::Pending => Poll::Pending,
+        }
+    }
 }
 
 /// Insecure certificate verifier for backend TLS connections (fallback only).
@@ -2463,6 +2808,7 @@ impl Default for HttpProxyService {
             http_idle_timeout: DEFAULT_HTTP_IDLE_TIMEOUT,
             ws_inactivity_timeout: DEFAULT_WS_INACTIVITY_TIMEOUT,
             ws_max_lifetime: DEFAULT_WS_MAX_LIFETIME,
+            quinn_client_endpoint: Arc::new(Self::create_quinn_client_endpoint()),
         }
     }
 }

rust/crates/rustproxy-passthrough/src/quic_handler.rs

@@ -3,13 +3,21 @@
 //! Manages QUIC endpoints (via quinn), accepts connections, and either:
 //! - Forwards streams bidirectionally to TCP backends (QUIC termination)
 //! - Dispatches to H3ProxyService for HTTP/3 handling (Phase 5)
+//!
+//! When `proxy_ips` is configured, a UDP relay layer intercepts PROXY protocol v2
+//! headers before they reach quinn, extracting real client IPs for attribution.
 
-use std::net::SocketAddr;
+use std::net::{IpAddr, SocketAddr};
+use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::Arc;
+use std::time::Instant;
 
 use tokio::io::AsyncWriteExt;
+use tokio::net::UdpSocket;
+use tokio::task::JoinHandle;
 
 use arc_swap::ArcSwap;
+use dashmap::DashMap;
 use quinn::{Endpoint, ServerConfig as QuinnServerConfig};
 use rustls::ServerConfig as RustlsServerConfig;
 use tokio_util::sync::CancellationToken;
@@ -19,6 +27,8 @@ use rustproxy_config::{RouteConfig, TransportProtocol};
 use rustproxy_metrics::MetricsCollector;
 use rustproxy_routing::{MatchContext, RouteManager};
 
+use rustproxy_http::h3_service::H3ProxyService;
+
 use crate::connection_tracker::ConnectionTracker;
 
 /// Create a QUIC server endpoint on the given port with the provided TLS config.
@@ -45,9 +55,274 @@ pub fn create_quic_endpoint(
     Ok(endpoint)
 }
 
+// ===== PROXY protocol relay for QUIC =====
+
+/// Result of creating a QUIC endpoint with a PROXY protocol relay layer.
+pub struct QuicProxyRelay {
+    /// The quinn endpoint (bound to 127.0.0.1:ephemeral).
+    pub endpoint: Endpoint,
+    /// The relay recv loop task handle.
+    pub relay_task: JoinHandle<()>,
+    /// Maps relay socket local addr → real client SocketAddr (from PROXY v2).
+    /// Consulted by `quic_accept_loop` to resolve real client IPs.
+    pub real_client_map: Arc<DashMap<SocketAddr, SocketAddr>>,
+}
+
+/// A single relay session for forwarding datagrams between an external source
+/// and the internal quinn endpoint.
+struct RelaySession {
+    socket: Arc<UdpSocket>,
+    last_activity: AtomicU64,
+    return_task: JoinHandle<()>,
+    cancel: CancellationToken,
+}
+
+/// Create a QUIC endpoint with a PROXY protocol v2 relay layer.
+///
+/// Instead of giving the external socket to quinn, we:
+/// 1. Bind a raw UDP socket on 0.0.0.0:port (external)
+/// 2. Bind quinn on 127.0.0.1:0 (internal, ephemeral)
+/// 3. Run a relay loop that filters PROXY v2 headers and forwards datagrams
+///
+/// Only used when `proxy_ips` is non-empty.
+pub fn create_quic_endpoint_with_proxy_relay(
+    port: u16,
+    tls_config: Arc<RustlsServerConfig>,
+    proxy_ips: Arc<Vec<IpAddr>>,
+    cancel: CancellationToken,
+) -> anyhow::Result<QuicProxyRelay> {
+    // Bind external socket on the real port
+    let external_socket = std::net::UdpSocket::bind(SocketAddr::from(([0, 0, 0, 0], port)))?;
+    external_socket.set_nonblocking(true)?;
+    let external_socket = Arc::new(
+        UdpSocket::from_std(external_socket)
+            .map_err(|e| anyhow::anyhow!("Failed to wrap external socket: {}", e))?,
+    );
+
+    // Bind quinn on localhost ephemeral port
+    let internal_socket = std::net::UdpSocket::bind("127.0.0.1:0")?;
+    let quinn_internal_addr = internal_socket.local_addr()?;
+
+    let quic_crypto = quinn::crypto::rustls::QuicServerConfig::try_from(tls_config)
+        .map_err(|e| anyhow::anyhow!("Failed to create QUIC crypto config: {}", e))?;
+    let server_config = QuinnServerConfig::with_crypto(Arc::new(quic_crypto));
+
+    let endpoint = Endpoint::new(
+        quinn::EndpointConfig::default(),
+        Some(server_config),
+        internal_socket,
+        quinn::default_runtime()
+            .ok_or_else(|| anyhow::anyhow!("No async runtime for quinn"))?,
+    )?;
+
+    let real_client_map = Arc::new(DashMap::new());
+
+    let relay_task = tokio::spawn(quic_proxy_relay_loop(
+        external_socket,
+        quinn_internal_addr,
+        proxy_ips,
+        Arc::clone(&real_client_map),
+        cancel,
+    ));
+
+    info!("QUIC endpoint with PROXY relay on port {} (quinn internal: {})", port, quinn_internal_addr);
+    Ok(QuicProxyRelay { endpoint, relay_task, real_client_map })
+}
+
+/// Main relay loop: reads datagrams from the external socket, filters PROXY v2
+/// headers from trusted proxy IPs, and forwards everything else to quinn via
+/// per-session relay sockets.
+async fn quic_proxy_relay_loop(
+    external_socket: Arc<UdpSocket>,
+    quinn_internal_addr: SocketAddr,
+    proxy_ips: Arc<Vec<IpAddr>>,
+    real_client_map: Arc<DashMap<SocketAddr, SocketAddr>>,
+    cancel: CancellationToken,
+) {
+    // Maps external source addr → real client addr (from PROXY v2 headers)
+    let proxy_addr_map: DashMap<SocketAddr, SocketAddr> = DashMap::new();
+    // Maps external source addr → relay session
+    let relay_sessions: DashMap<SocketAddr, Arc<RelaySession>> = DashMap::new();
+    let epoch = Instant::now();
+    let mut buf = vec![0u8; 65535];
+
+    // Inline cleanup: periodically scan relay_sessions for stale entries
+    let mut last_cleanup = Instant::now();
+    let cleanup_interval = std::time::Duration::from_secs(30);
+    let session_timeout_ms: u64 = 120_000;
+
+    loop {
+        let (len, src_addr) = tokio::select! {
+            _ = cancel.cancelled() => {
+                debug!("QUIC proxy relay loop cancelled");
+                break;
+            }
+            result = external_socket.recv_from(&mut buf) => {
+                match result {
+                    Ok(r) => r,
+                    Err(e) => {
+                        warn!("QUIC proxy relay recv error: {}", e);
+                        continue;
+                    }
+                }
+            }
+        };
+
+        let datagram = &buf[..len];
+
+        // PROXY v2 handling: only on first datagram from a trusted proxy IP
+        // (before a relay session exists for this source)
+        if proxy_ips.contains(&src_addr.ip()) && relay_sessions.get(&src_addr).is_none() {
+            if crate::proxy_protocol::is_proxy_protocol_v2(datagram) {
+                match crate::proxy_protocol::parse_v2(datagram) {
+                    Ok((header, _consumed)) => {
+                        debug!("QUIC PROXY v2 from {}: real client {}", src_addr, header.source_addr);
+                        proxy_addr_map.insert(src_addr, header.source_addr);
+                        continue; // consume the PROXY v2 datagram
+                    }
+                    Err(e) => {
+                        debug!("QUIC proxy relay: failed to parse PROXY v2 from {}: {}", src_addr, e);
+                    }
+                }
+            }
+        }
+
+        // Determine real client address
+        let real_client = proxy_addr_map.get(&src_addr)
+            .map(|r| *r)
+            .unwrap_or(src_addr);
+
+        // Get or create relay session for this external source
+        let session = match relay_sessions.get(&src_addr) {
+            Some(s) => {
+                s.last_activity.store(epoch.elapsed().as_millis() as u64, Ordering::Relaxed);
+                Arc::clone(s.value())
+            }
+            None => {
+                // Create new relay socket connected to quinn's internal address
+                let relay_socket = match UdpSocket::bind("127.0.0.1:0").await {
+                    Ok(s) => s,
+                    Err(e) => {
+                        warn!("QUIC relay: failed to bind relay socket: {}", e);
+                        continue;
+                    }
+                };
+                if let Err(e) = relay_socket.connect(quinn_internal_addr).await {
+                    warn!("QUIC relay: failed to connect relay socket to {}: {}", quinn_internal_addr, e);
+                    continue;
+                }
+                let relay_local_addr = match relay_socket.local_addr() {
+                    Ok(a) => a,
+                    Err(e) => {
+                        warn!("QUIC relay: failed to get relay socket local addr: {}", e);
+                        continue;
+                    }
+                };
+                let relay_socket = Arc::new(relay_socket);
+
+                // Store the real client mapping for the QUIC accept loop
+                real_client_map.insert(relay_local_addr, real_client);
+
+                // Spawn return-path relay: quinn -> external socket -> original source
+                let session_cancel = cancel.child_token();
+                let return_task = tokio::spawn(relay_return_path(
+                    Arc::clone(&relay_socket),
+                    Arc::clone(&external_socket),
+                    src_addr,
+                    session_cancel.child_token(),
+                ));
+
+                let session = Arc::new(RelaySession {
+                    socket: relay_socket,
+                    last_activity: AtomicU64::new(epoch.elapsed().as_millis() as u64),
+                    return_task,
+                    cancel: session_cancel,
+                });
+
+                relay_sessions.insert(src_addr, Arc::clone(&session));
+                debug!("QUIC relay: new session for {} (relay {}), real client {}",
+                    src_addr, relay_local_addr, real_client);
+
+                session
+            }
+        };
+
+        // Forward datagram to quinn via the relay socket
+        if let Err(e) = session.socket.send(datagram).await {
+            debug!("QUIC relay: forward error to quinn for {}: {}", src_addr, e);
+        }
+
+        // Periodic cleanup of stale relay sessions
+        if last_cleanup.elapsed() >= cleanup_interval {
+            last_cleanup = Instant::now();
+            let now_ms = epoch.elapsed().as_millis() as u64;
+            let stale_keys: Vec<SocketAddr> = relay_sessions.iter()
+                .filter(|entry| {
+                    let age = now_ms.saturating_sub(entry.value().last_activity.load(Ordering::Relaxed));
+                    age > session_timeout_ms
+                })
+                .map(|entry| *entry.key())
+                .collect();
+
+            for key in stale_keys {
+                if let Some((_, session)) = relay_sessions.remove(&key) {
+                    session.cancel.cancel();
+                    session.return_task.abort();
+                    // Clean up real_client_map entry
+                    if let Ok(addr) = session.socket.local_addr() {
+                        real_client_map.remove(&addr);
+                    }
+                    proxy_addr_map.remove(&key);
+                    debug!("QUIC relay: cleaned up stale session for {}", key);
+                }
+            }
+        }
+    }
+
+    // Shutdown: cancel all relay sessions
+    for entry in relay_sessions.iter() {
+        entry.value().cancel.cancel();
+        entry.value().return_task.abort();
+    }
+}
+
+/// Return-path relay: receives datagrams from quinn (via the relay socket)
+/// and forwards them back to the external client through the external socket.
+async fn relay_return_path(
+    relay_socket: Arc<UdpSocket>,
+    external_socket: Arc<UdpSocket>,
+    external_src_addr: SocketAddr,
+    cancel: CancellationToken,
+) {
+    let mut buf = vec![0u8; 65535];
+    loop {
+        let len = tokio::select! {
+            _ = cancel.cancelled() => break,
+            result = relay_socket.recv(&mut buf) => {
+                match result {
+                    Ok(len) => len,
+                    Err(e) => {
+                        debug!("QUIC relay return recv error for {}: {}", external_src_addr, e);
+                        break;
+                    }
+                }
+            }
+        };
+
+        if let Err(e) = external_socket.send_to(&buf[..len], external_src_addr).await {
+            debug!("QUIC relay return send error to {}: {}", external_src_addr, e);
+            break;
+        }
+    }
+}
+
+// ===== QUIC accept loop =====
+
 /// Run the QUIC accept loop for a single endpoint.
 ///
 /// Accepts incoming QUIC connections and spawns a task per connection.
+/// When `real_client_map` is provided, it is consulted to resolve real client
+/// IPs from PROXY protocol v2 headers (relay socket addr → real client addr).
 pub async fn quic_accept_loop(
     endpoint: Endpoint,
     port: u16,
@@ -55,6 +330,8 @@ pub async fn quic_accept_loop(
     metrics: Arc<MetricsCollector>,
     conn_tracker: Arc<ConnectionTracker>,
     cancel: CancellationToken,
+    h3_service: Option<Arc<H3ProxyService>>,
+    real_client_map: Option<Arc<DashMap<SocketAddr, SocketAddr>>>,
 ) {
     loop {
         let incoming = tokio::select! {
@@ -74,11 +351,16 @@ pub async fn quic_accept_loop(
         };
 
         let remote_addr = incoming.remote_address();
-        let ip = remote_addr.ip();
+
+        // Resolve real client IP from PROXY protocol map if available
+        let real_addr = real_client_map.as_ref()
+            .and_then(|map| map.get(&remote_addr).map(|r| *r))
+            .unwrap_or(remote_addr);
+        let ip = real_addr.ip();
 
         // Per-IP rate limiting
         if !conn_tracker.try_accept(&ip) {
-            debug!("QUIC connection rejected from {} (rate limit)", remote_addr);
+            debug!("QUIC connection rejected from {} (rate limit)", real_addr);
             // Drop `incoming` to refuse the connection
             continue;
         }
@@ -101,7 +383,7 @@ pub async fn quic_accept_loop(
         let route = match rm.find_route(&ctx) {
             Some(m) => m.route.clone(),
             None => {
-                debug!("No QUIC route matched for port {} from {}", port, remote_addr);
+                debug!("No QUIC route matched for port {} from {}", port, real_addr);
                 continue;
             }
         };
@@ -113,11 +395,13 @@ pub async fn quic_accept_loop(
         let metrics = Arc::clone(&metrics);
         let conn_tracker = Arc::clone(&conn_tracker);
         let cancel = cancel.child_token();
+        let h3_svc = h3_service.clone();
+        let real_client_addr = if real_addr != remote_addr { Some(real_addr) } else { None };
 
         tokio::spawn(async move {
-            match handle_quic_connection(incoming, route, port, Arc::clone(&metrics), &cancel).await {
+            match handle_quic_connection(incoming, route, port, Arc::clone(&metrics), &cancel, h3_svc, real_client_addr).await {
-                Ok(()) => debug!("QUIC connection from {} completed", remote_addr),
+                Ok(()) => debug!("QUIC connection from {} completed", real_addr),
-                Err(e) => debug!("QUIC connection from {} error: {}", remote_addr, e),
+                Err(e) => debug!("QUIC connection from {} error: {}", real_addr, e),
             }
 
             // Cleanup
@@ -139,10 +423,12 @@ async fn handle_quic_connection(
     port: u16,
     metrics: Arc<MetricsCollector>,
     cancel: &CancellationToken,
+    h3_service: Option<Arc<H3ProxyService>>,
+    real_client_addr: Option<SocketAddr>,
 ) -> anyhow::Result<()> {
     let connection = incoming.await?;
-    let remote_addr = connection.remote_address();
+    let effective_addr = real_client_addr.unwrap_or_else(|| connection.remote_address());
-    debug!("QUIC connection established from {}", remote_addr);
+    debug!("QUIC connection established from {}", effective_addr);
 
     // Check if this route has HTTP/3 enabled
     let enable_http3 = route.action.udp.as_ref()
@@ -151,13 +437,23 @@ async fn handle_quic_connection(
         .unwrap_or(false);
 
     if enable_http3 {
-        // Phase 5: dispatch to H3ProxyService
+        if let Some(ref h3_svc) = h3_service {
-        // For now, log and accept streams for basic handling
+            debug!("HTTP/3 enabled for route {:?}, dispatching to H3ProxyService", route.name);
-        debug!("HTTP/3 enabled for route {:?}, dispatching to H3 handler", route.name);
+            h3_svc.handle_connection(connection, &route, port, real_client_addr).await
-        handle_h3_connection(connection, route, port, &metrics, cancel).await
+        } else {
+            warn!("HTTP/3 enabled for route {:?} but H3ProxyService not initialized", route.name);
+            // Keep connection alive until cancelled
+            tokio::select! {
+                _ = cancel.cancelled() => {}
+                reason = connection.closed() => {
+                    debug!("HTTP/3 connection closed (no service): {}", reason);
+                }
+            }
+            Ok(())
+        }
     } else {
         // Non-HTTP3 QUIC: bidirectional stream forwarding to TCP backend
-        handle_quic_stream_forwarding(connection, route, port, metrics, cancel).await
+        handle_quic_stream_forwarding(connection, route, port, metrics, cancel, real_client_addr).await
     }
 }
 
@@ -172,8 +468,9 @@ async fn handle_quic_stream_forwarding(
     port: u16,
     metrics: Arc<MetricsCollector>,
     cancel: &CancellationToken,
+    real_client_addr: Option<SocketAddr>,
 ) -> anyhow::Result<()> {
-    let remote_addr = connection.remote_address();
+    let effective_addr = real_client_addr.unwrap_or_else(|| connection.remote_address());
     let route_id = route.name.as_deref().or(route.id.as_deref());
     let metrics_arc = metrics;
 
@@ -194,7 +491,7 @@ async fn handle_quic_stream_forwarding(
                     Err(quinn::ConnectionError::ApplicationClosed(_)) => break,
                     Err(quinn::ConnectionError::LocallyClosed) => break,
                     Err(e) => {
-                        debug!("QUIC stream accept error from {}: {}", remote_addr, e);
+                        debug!("QUIC stream accept error from {}: {}", effective_addr, e);
                         break;
                     }
                 }
@@ -202,7 +499,7 @@ async fn handle_quic_stream_forwarding(
         };
 
         let backend_addr = backend_addr.clone();
-        let ip_str = remote_addr.ip().to_string();
+        let ip_str = effective_addr.ip().to_string();
         let stream_metrics = Arc::clone(&metrics_arc);
         let stream_route_id = route_id.map(|s| s.to_string());
 
@@ -257,29 +554,6 @@ async fn forward_quic_stream_to_tcp(
     Ok((bytes_in, bytes_out))
 }
 
-/// Placeholder for HTTP/3 connection handling (Phase 5).
-///
-/// Once h3_service is implemented, this will delegate to it.
-async fn handle_h3_connection(
-    connection: quinn::Connection,
-    _route: RouteConfig,
-    _port: u16,
-    _metrics: &MetricsCollector,
-    cancel: &CancellationToken,
-) -> anyhow::Result<()> {
-    warn!("HTTP/3 handling not yet fully implemented — accepting connection but no request processing");
-
-    // Keep the connection alive until cancelled or closed
-    tokio::select! {
-        _ = cancel.cancelled() => {}
-        reason = connection.closed() => {
-            debug!("HTTP/3 connection closed: {}", reason);
-        }
-    }
-
-    Ok(())
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

rust/crates/rustproxy-passthrough/src/udp_listener.rs

@@ -2,12 +2,17 @@
 //!
 //! Binds UDP sockets on configured ports, receives datagrams, matches routes,
 //! tracks sessions (flows), and forwards datagrams to backend UDP sockets.
+//!
+//! Supports PROXY protocol v2 on both raw UDP and QUIC paths when `proxy_ips`
+//! is configured. For QUIC, a relay layer intercepts datagrams before they
+//! reach the quinn endpoint.
 
 use std::collections::HashMap;
-use std::net::SocketAddr;
+use std::net::{IpAddr, SocketAddr};
 use std::sync::atomic::Ordering;
 use std::sync::Arc;
 
+use dashmap::DashMap;
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 
 use arc_swap::ArcSwap;
@@ -21,13 +26,15 @@ use rustproxy_config::{RouteActionType, TransportProtocol};
 use rustproxy_metrics::MetricsCollector;
 use rustproxy_routing::{MatchContext, RouteManager};
 
+use rustproxy_http::h3_service::H3ProxyService;
+
 use crate::connection_tracker::ConnectionTracker;
 use crate::udp_session::{SessionKey, UdpSession, UdpSessionConfig, UdpSessionTable};
 
 /// Manages UDP listeners across all configured ports.
 pub struct UdpListenerManager {
-    /// Port → recv loop task handle
+    /// Port → (recv loop task handle, optional QUIC endpoint for TLS updates)
-    listeners: HashMap<u16, JoinHandle<()>>,
+    listeners: HashMap<u16, (JoinHandle<()>, Option<quinn::Endpoint>)>,
     /// Hot-reloadable route table
     route_manager: Arc<ArcSwap<RouteManager>>,
     /// Shared metrics collector
@@ -44,13 +51,21 @@ pub struct UdpListenerManager {
     relay_writer: Arc<Mutex<Option<tokio::net::unix::OwnedWriteHalf>>>,
     /// Cancel token for the current relay reply reader task
     relay_reader_cancel: Option<CancellationToken>,
+    /// H3 proxy service for HTTP/3 request handling
+    h3_service: Option<Arc<H3ProxyService>>,
+    /// Trusted proxy IPs that may send PROXY protocol v2 headers.
+    /// When non-empty, PROXY v2 detection is enabled on both raw UDP and QUIC paths.
+    proxy_ips: Arc<Vec<IpAddr>>,
 }
 
 impl Drop for UdpListenerManager {
     fn drop(&mut self) {
         self.cancel_token.cancel();
-        for (_, handle) in self.listeners.drain() {
+        for (_, (handle, endpoint)) in self.listeners.drain() {
             handle.abort();
+            if let Some(ep) = endpoint {
+                ep.close(quinn::VarInt::from_u32(0), b"shutdown");
+            }
         }
     }
 }
@@ -72,9 +87,24 @@ impl UdpListenerManager {
             datagram_handler_relay: Arc::new(RwLock::new(None)),
             relay_writer: Arc::new(Mutex::new(None)),
             relay_reader_cancel: None,
+            h3_service: None,
+            proxy_ips: Arc::new(Vec::new()),
         }
     }
 
+    /// Set the trusted proxy IPs for PROXY protocol v2 detection.
+    pub fn set_proxy_ips(&mut self, ips: Vec<IpAddr>) {
+        if !ips.is_empty() {
+            info!("UDP/QUIC PROXY protocol v2 enabled for {} trusted IPs", ips.len());
+        }
+        self.proxy_ips = Arc::new(ips);
+    }
+
+    /// Set the H3 proxy service for HTTP/3 request handling.
+    pub fn set_h3_service(&mut self, svc: Arc<H3ProxyService>) {
+        self.h3_service = Some(svc);
+    }
+
     /// Update the route manager (for hot-reload).
     pub fn update_routes(&self, route_manager: Arc<RouteManager>) {
         self.route_manager.store(route_manager);
@@ -109,18 +139,44 @@ impl UdpListenerManager {
 
         if has_quic {
             if let Some(tls) = tls_config {
-                // Create QUIC endpoint
+                if self.proxy_ips.is_empty() {
-                let endpoint = crate::quic_handler::create_quic_endpoint(port, tls)?;
+                    // Direct path: quinn owns the external socket (zero overhead)
-                let handle = tokio::spawn(crate::quic_handler::quic_accept_loop(
+                    let endpoint = crate::quic_handler::create_quic_endpoint(port, tls)?;
-                    endpoint,
+                    let endpoint_for_updates = endpoint.clone();
-                    port,
+                    let handle = tokio::spawn(crate::quic_handler::quic_accept_loop(
-                    Arc::clone(&self.route_manager),
+                        endpoint,
-                    Arc::clone(&self.metrics),
+                        port,
-                    Arc::clone(&self.conn_tracker),
+                        Arc::clone(&self.route_manager),
-                    self.cancel_token.child_token(),
+                        Arc::clone(&self.metrics),
-                ));
+                        Arc::clone(&self.conn_tracker),
-                self.listeners.insert(port, handle);
+                        self.cancel_token.child_token(),
-                info!("QUIC endpoint started on port {}", port);
+                        self.h3_service.clone(),
+                        None,
+                    ));
+                    self.listeners.insert(port, (handle, Some(endpoint_for_updates)));
+                    info!("QUIC endpoint started on port {}", port);
+                } else {
+                    // Proxy relay path: we own external socket, quinn on localhost
+                    let relay = crate::quic_handler::create_quic_endpoint_with_proxy_relay(
+                        port,
+                        tls,
+                        Arc::clone(&self.proxy_ips),
+                        self.cancel_token.child_token(),
+                    )?;
+                    let endpoint_for_updates = relay.endpoint.clone();
+                    let handle = tokio::spawn(crate::quic_handler::quic_accept_loop(
+                        relay.endpoint,
+                        port,
+                        Arc::clone(&self.route_manager),
+                        Arc::clone(&self.metrics),
+                        Arc::clone(&self.conn_tracker),
+                        self.cancel_token.child_token(),
+                        self.h3_service.clone(),
+                        Some(relay.real_client_map),
+                    ));
+                    self.listeners.insert(port, (handle, Some(endpoint_for_updates)));
+                    info!("QUIC endpoint with PROXY relay started on port {}", port);
+                }
                 return Ok(());
             } else {
                 warn!("QUIC routes on port {} but no TLS config provided, falling back to raw UDP", port);
@@ -143,9 +199,10 @@ impl UdpListenerManager {
             Arc::clone(&self.datagram_handler_relay),
             Arc::clone(&self.relay_writer),
             self.cancel_token.child_token(),
+            Arc::clone(&self.proxy_ips),
         ));
 
-        self.listeners.insert(port, handle);
+        self.listeners.insert(port, (handle, None));
 
         // Start the session cleanup task if this is the first port
         if self.listeners.len() == 1 {
@@ -157,8 +214,11 @@ impl UdpListenerManager {
 
     /// Stop listening on a UDP port.
     pub fn remove_port(&mut self, port: u16) {
-        if let Some(handle) = self.listeners.remove(&port) {
+        if let Some((handle, endpoint)) = self.listeners.remove(&port) {
             handle.abort();
+            if let Some(ep) = endpoint {
+                ep.close(quinn::VarInt::from_u32(0), b"port removed");
+            }
             info!("UDP listener removed from port {}", port);
         }
     }
@@ -173,14 +233,180 @@ impl UdpListenerManager {
     /// Stop all listeners and clean up.
     pub async fn stop(&mut self) {
         self.cancel_token.cancel();
-        for (port, handle) in self.listeners.drain() {
+        for (port, (handle, endpoint)) in self.listeners.drain() {
             handle.abort();
+            if let Some(ep) = endpoint {
+                ep.close(quinn::VarInt::from_u32(0), b"shutdown");
+            }
             debug!("UDP listener stopped on port {}", port);
         }
         info!("All UDP listeners stopped, {} sessions remaining",
             self.session_table.session_count());
     }
 
+    /// Update TLS config on all active QUIC endpoints (cert refresh).
+    /// Only affects new incoming connections — existing connections are undisturbed.
+    /// Uses quinn's Endpoint::set_server_config() for zero-downtime hot-swap.
+    pub fn update_quic_tls(&self, tls_config: Arc<rustls::ServerConfig>) {
+        for (port, (_handle, endpoint)) in &self.listeners {
+            if let Some(ep) = endpoint {
+                match quinn::crypto::rustls::QuicServerConfig::try_from(Arc::clone(&tls_config)) {
+                    Ok(quic_crypto) => {
+                        let server_config = quinn::ServerConfig::with_crypto(Arc::new(quic_crypto));
+                        ep.set_server_config(Some(server_config));
+                        info!("Updated QUIC TLS config on port {}", port);
+                    }
+                    Err(e) => {
+                        warn!("Failed to update QUIC TLS config on port {}: {}", port, e);
+                    }
+                }
+            }
+        }
+    }
+
+    /// Upgrade raw UDP fallback listeners to QUIC endpoints.
+    ///
+    /// At startup, if no TLS certs are available, QUIC routes fall back to raw UDP.
+    /// When certs become available later (via loadCertificate IPC or ACME), this method
+    /// stops the raw UDP listener, drains sessions, and creates a proper QUIC endpoint.
+    ///
+    /// This is idempotent — ports that already have QUIC endpoints are skipped.
+    pub async fn upgrade_raw_to_quic(&mut self, tls_config: Arc<rustls::ServerConfig>) {
+        // Find ports that are raw UDP fallback (endpoint=None) but have QUIC routes
+        let rm = self.route_manager.load();
+        let upgrade_ports: Vec<u16> = self.listeners.iter()
+            .filter(|(_, (_, endpoint))| endpoint.is_none())
+            .filter(|(port, _)| {
+                rm.routes_for_port(**port).iter().any(|r| {
+                    r.action.udp.as_ref()
+                        .and_then(|u| u.quic.as_ref())
+                        .is_some()
+                })
+            })
+            .map(|(port, _)| *port)
+            .collect();
+
+        for port in upgrade_ports {
+            info!("Upgrading raw UDP listener on port {} to QUIC endpoint", port);
+
+            // Stop the raw UDP listener task and drain sessions to release the socket
+            if let Some((handle, _)) = self.listeners.remove(&port) {
+                handle.abort();
+            }
+            let drained = self.session_table.drain_port(
+                port, &self.metrics, &self.conn_tracker,
+            );
+            if drained > 0 {
+                debug!("Drained {} UDP sessions on port {} for QUIC upgrade", drained, port);
+            }
+
+            // Brief yield to let aborted tasks drop their socket references
+            tokio::task::yield_now().await;
+
+            // Create QUIC endpoint on the now-free port
+            let create_result = if self.proxy_ips.is_empty() {
+                self.create_quic_direct(port, Arc::clone(&tls_config))
+            } else {
+                self.create_quic_with_relay(port, Arc::clone(&tls_config))
+            };
+
+            match create_result {
+                Ok(()) => {
+                    info!("QUIC endpoint started on port {} (upgraded from raw UDP)", port);
+                }
+                Err(e) => {
+                    // Port may still be held — retry once after a brief delay
+                    warn!("QUIC endpoint creation failed on port {}, retrying: {}", port, e);
+                    tokio::time::sleep(std::time::Duration::from_millis(50)).await;
+
+                    let retry_result = if self.proxy_ips.is_empty() {
+                        self.create_quic_direct(port, Arc::clone(&tls_config))
+                    } else {
+                        self.create_quic_with_relay(port, Arc::clone(&tls_config))
+                    };
+
+                    match retry_result {
+                        Ok(()) => {
+                            info!("QUIC endpoint started on port {} (upgraded from raw UDP, retry)", port);
+                        }
+                        Err(e2) => {
+                            error!("Failed to upgrade port {} to QUIC after retry: {}. \
+                                   Rebinding as raw UDP.", port, e2);
+                            // Fallback: rebind as raw UDP so the port isn't dead
+                            if let Ok(()) = self.rebind_raw_udp(port).await {
+                                warn!("Port {} rebound as raw UDP (QUIC upgrade failed)", port);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    /// Create a direct QUIC endpoint (quinn owns the socket).
+    fn create_quic_direct(&mut self, port: u16, tls_config: Arc<rustls::ServerConfig>) -> anyhow::Result<()> {
+        let endpoint = crate::quic_handler::create_quic_endpoint(port, tls_config)?;
+        let endpoint_for_updates = endpoint.clone();
+        let handle = tokio::spawn(crate::quic_handler::quic_accept_loop(
+            endpoint,
+            port,
+            Arc::clone(&self.route_manager),
+            Arc::clone(&self.metrics),
+            Arc::clone(&self.conn_tracker),
+            self.cancel_token.child_token(),
+            self.h3_service.clone(),
+            None,
+        ));
+        self.listeners.insert(port, (handle, Some(endpoint_for_updates)));
+        Ok(())
+    }
+
+    /// Create a QUIC endpoint with PROXY protocol relay.
+    fn create_quic_with_relay(&mut self, port: u16, tls_config: Arc<rustls::ServerConfig>) -> anyhow::Result<()> {
+        let relay = crate::quic_handler::create_quic_endpoint_with_proxy_relay(
+            port,
+            tls_config,
+            Arc::clone(&self.proxy_ips),
+            self.cancel_token.child_token(),
+        )?;
+        let endpoint_for_updates = relay.endpoint.clone();
+        let handle = tokio::spawn(crate::quic_handler::quic_accept_loop(
+            relay.endpoint,
+            port,
+            Arc::clone(&self.route_manager),
+            Arc::clone(&self.metrics),
+            Arc::clone(&self.conn_tracker),
+            self.cancel_token.child_token(),
+            self.h3_service.clone(),
+            Some(relay.real_client_map),
+        ));
+        self.listeners.insert(port, (handle, Some(endpoint_for_updates)));
+        Ok(())
+    }
+
+    /// Rebind a port as a raw UDP listener (fallback when QUIC upgrade fails).
+    async fn rebind_raw_udp(&mut self, port: u16) -> anyhow::Result<()> {
+        let addr: std::net::SocketAddr = ([0, 0, 0, 0], port).into();
+        let socket = UdpSocket::bind(addr).await?;
+        let socket = Arc::new(socket);
+
+        let handle = tokio::spawn(Self::recv_loop(
+            socket,
+            port,
+            Arc::clone(&self.route_manager),
+            Arc::clone(&self.metrics),
+            Arc::clone(&self.conn_tracker),
+            Arc::clone(&self.session_table),
+            Arc::clone(&self.datagram_handler_relay),
+            Arc::clone(&self.relay_writer),
+            self.cancel_token.child_token(),
+            Arc::clone(&self.proxy_ips),
+        ));
+
+        self.listeners.insert(port, (handle, None));
+        Ok(())
+    }
+
     /// Set the datagram handler relay socket path and establish connection.
     pub async fn set_datagram_handler_relay(&mut self, path: String) {
         // Cancel previous relay reader task if any
@@ -255,6 +481,10 @@ impl UdpListenerManager {
     }
 
     /// Main receive loop for a UDP port.
+    ///
+    /// When `proxy_ips` is non-empty, the first datagram from a trusted proxy IP
+    /// is checked for PROXY protocol v2. If found, the real client IP is extracted
+    /// and used for all subsequent session handling for that source address.
     async fn recv_loop(
         socket: Arc<UdpSocket>,
         port: u16,
@@ -265,10 +495,15 @@ impl UdpListenerManager {
         _datagram_handler_relay: Arc<RwLock<Option<String>>>,
         relay_writer: Arc<Mutex<Option<tokio::net::unix::OwnedWriteHalf>>>,
         cancel: CancellationToken,
+        proxy_ips: Arc<Vec<IpAddr>>,
     ) {
         // Use a reasonably large buffer; actual max is per-route but we need a single buffer
         let mut buf = vec![0u8; 65535];
 
+        // Maps proxy source addr → real client addr (from PROXY v2 headers).
+        // Only populated when proxy_ips is non-empty.
+        let proxy_addr_map: DashMap<SocketAddr, SocketAddr> = DashMap::new();
+
         loop {
             let (len, client_addr) = tokio::select! {
                 _ = cancel.cancelled() => {
@@ -288,9 +523,39 @@ impl UdpListenerManager {
 
             let datagram = &buf[..len];
 
-            // Route matching
+            // PROXY protocol v2 detection for datagrams from trusted proxy IPs
+            let effective_client_ip = if !proxy_ips.is_empty() && proxy_ips.contains(&client_addr.ip()) {
+                let session_key: SessionKey = (client_addr, port);
+                if session_table.get(&session_key).is_none() && !proxy_addr_map.contains_key(&client_addr) {
+                    // No session and no prior PROXY header — check for PROXY v2
+                    if crate::proxy_protocol::is_proxy_protocol_v2(datagram) {
+                        match crate::proxy_protocol::parse_v2(datagram) {
+                            Ok((header, _consumed)) => {
+                                debug!("UDP PROXY v2 from {}: real client {}", client_addr, header.source_addr);
+                                proxy_addr_map.insert(client_addr, header.source_addr);
+                                continue; // discard the PROXY v2 datagram
+                            }
+                            Err(e) => {
+                                debug!("UDP PROXY v2 parse error from {}: {}", client_addr, e);
+                                client_addr.ip()
+                            }
+                        }
+                    } else {
+                        client_addr.ip()
+                    }
+                } else {
+                    // Use real client IP if we've previously seen a PROXY v2 header
+                    proxy_addr_map.get(&client_addr)
+                        .map(|r| r.ip())
+                        .unwrap_or_else(|| client_addr.ip())
+                }
+            } else {
+                client_addr.ip()
+            };
+
+            // Route matching — use effective (real) client IP
             let rm = route_manager.load();
-            let ip_str = client_addr.ip().to_string();
+            let ip_str = effective_client_ip.to_string();
             let ctx = MatchContext {
                 port,
                 domain: None,
@@ -339,20 +604,21 @@ impl UdpListenerManager {
             }
 
             // Session lookup or create
+            // Session key uses the proxy's source addr for correct return-path routing
             let session_key: SessionKey = (client_addr, port);
             let session = match session_table.get(&session_key) {
                 Some(s) => s,
                 None => {
-                    // New session — check per-IP limits
+                    // New session — check per-IP limits using the real client IP
-                    if !conn_tracker.try_accept(&client_addr.ip()) {
+                    if !conn_tracker.try_accept(&effective_client_ip) {
-                        debug!("UDP session rejected for {} (rate limit)", client_addr);
+                        debug!("UDP session rejected for {} (rate limit)", effective_client_ip);
                         continue;
                     }
                     if !session_table.can_create_session(
-                        &client_addr.ip(),
+                        &effective_client_ip,
                         udp_config.max_sessions_per_ip,
                     ) {
-                        debug!("UDP session rejected for {} (per-IP session limit)", client_addr);
+                        debug!("UDP session rejected for {} (per-IP session limit)", effective_client_ip);
                         continue;
                     }
 
@@ -385,8 +651,8 @@ impl UdpListenerManager {
                     }
                     let backend_socket = Arc::new(backend_socket);
 
-                    debug!("New UDP session: {} -> {} (via port {})",
+                    debug!("New UDP session: {} -> {} (via port {}, real client {})",
-                        client_addr, backend_addr, port);
+                        client_addr, backend_addr, port, effective_client_ip);
 
                     // Spawn return-path relay task
                     let session_cancel = CancellationToken::new();
@@ -406,7 +672,7 @@ impl UdpListenerManager {
                         last_activity: std::sync::atomic::AtomicU64::new(session_table.elapsed_ms()),
                         created_at: std::time::Instant::now(),
                         route_id: route_id.map(|s| s.to_string()),
-                        source_ip: client_addr.ip(),
+                        source_ip: effective_client_ip,
                         client_addr,
                         return_task,
                         cancel: session_cancel,
@@ -417,8 +683,8 @@ impl UdpListenerManager {
                         continue;
                     }
 
-                    // Track in metrics
+                    // Track in metrics using the real client IP
-                    conn_tracker.connection_opened(&client_addr.ip());
+                    conn_tracker.connection_opened(&effective_client_ip);
                     metrics.connection_opened(route_id, Some(&ip_str));
                     metrics.udp_session_opened();
 

rust/crates/rustproxy-passthrough/src/udp_session.rs

@@ -201,6 +201,36 @@ impl UdpSessionTable {
         removed
     }
 
+    /// Drain all sessions on a given listening port, releasing socket references.
+    /// Used when upgrading a raw UDP listener to QUIC — the raw UDP socket's
+    /// Arc refcount must drop to zero so the port can be rebound.
+    pub fn drain_port(
+        &self,
+        port: u16,
+        metrics: &MetricsCollector,
+        conn_tracker: &ConnectionTracker,
+    ) -> usize {
+        let keys: Vec<SessionKey> = self.sessions.iter()
+            .filter(|entry| entry.key().1 == port)
+            .map(|entry| *entry.key())
+            .collect();
+
+        let mut removed = 0;
+        for key in keys {
+            if let Some(session) = self.remove(&key) {
+                session.cancel.cancel();
+                conn_tracker.connection_closed(&session.source_ip);
+                metrics.connection_closed(
+                    session.route_id.as_deref(),
+                    Some(&session.source_ip.to_string()),
+                );
+                metrics.udp_session_closed();
+                removed += 1;
+            }
+        }
+        removed
+    }
+
     /// Total number of active sessions.
     pub fn session_count(&self) -> usize {
         self.sessions.len()

rust/crates/rustproxy-routing/src/route_manager.rs

@@ -122,10 +122,16 @@ impl RouteManager {
                 // This prevents session-ticket resumption from misrouting when clients
                 // omit SNI (RFC 8446 recommends but doesn't mandate SNI on resumption).
                 // Wildcard-only routes (domains: ["*"]) still match since they accept all.
-                let patterns = domains.to_vec();
+                //
-                let is_wildcard_only = patterns.iter().all(|d| *d == "*");
+                // Exception: QUIC (UDP transport) encrypts the TLS ClientHello, so SNI
-                if !is_wildcard_only {
+                // is unavailable at accept time. Domain verification happens per-request
-                    return false;
+                // in H3ProxyService via the :authority header.
+                if ctx.transport != Some(TransportProtocol::Udp) {
+                    let patterns = domains.to_vec();
+                    let is_wildcard_only = patterns.iter().all(|d| *d == "*");
+                    if !is_wildcard_only {
+                        return false;
+                    }
                 }
             }
         }
@@ -997,4 +1003,52 @@ mod tests {
         let result = manager.find_route(&udp_ctx).unwrap();
         assert_eq!(result.route.name.as_deref(), Some("udp-route"));
     }
+
+    #[test]
+    fn test_quic_tls_no_sni_matches_domain_restricted_route() {
+        // QUIC accept-level matching: is_tls=true, domain=None, transport=Udp.
+        // Should match because QUIC encrypts the ClientHello — SNI is unavailable
+        // at accept time but verified per-request in H3ProxyService.
+        let mut route = make_route(443, Some("example.com"), 0);
+        route.route_match.transport = Some(TransportProtocol::Udp);
+        let routes = vec![route];
+        let manager = RouteManager::new(routes);
+
+        let ctx = MatchContext {
+            port: 443,
+            domain: None,
+            path: None,
+            client_ip: None,
+            tls_version: None,
+            headers: None,
+            is_tls: true,
+            protocol: Some("quic"),
+            transport: Some(TransportProtocol::Udp),
+        };
+
+        assert!(manager.find_route(&ctx).is_some(),
+            "QUIC (UDP) with is_tls=true and domain=None should match domain-restricted routes");
+    }
+
+    #[test]
+    fn test_tcp_tls_no_sni_still_rejects_domain_restricted_route() {
+        // TCP TLS without SNI must still be rejected (no QUIC exemption).
+        let routes = vec![make_route(443, Some("example.com"), 0)];
+        let manager = RouteManager::new(routes);
+
+        let ctx = MatchContext {
+            port: 443,
+            domain: None,
+            path: None,
+            client_ip: None,
+            tls_version: None,
+            headers: None,
+            is_tls: true,
+            protocol: None,
+            transport: None, // TCP (default)
+        };
+
+        assert!(manager.find_route(&ctx).is_none(),
+            "TCP TLS without SNI should NOT match domain-restricted routes");
+    }
 }

rust/crates/rustproxy/src/lib.rs

@@ -264,6 +264,8 @@ impl RustProxy {
             conn_config.socket_timeout_ms,
             conn_config.max_connection_lifetime_ms,
         );
+        // Clone proxy_ips before conn_config is moved into the TCP listener
+        let udp_proxy_ips = conn_config.proxy_ips.clone();
         listener.set_connection_config(conn_config);
 
         // Share the socket-handler relay path with the listener
@@ -339,6 +341,18 @@ impl RustProxy {
                 conn_tracker,
                 self.cancel_token.clone(),
             );
+            udp_mgr.set_proxy_ips(udp_proxy_ips.clone());
+
+            // Construct H3ProxyService for HTTP/3 request handling
+            let h3_svc = rustproxy_http::h3_service::H3ProxyService::new(
+                Arc::new(ArcSwap::from(Arc::clone(&*self.route_table.load()))),
+                Arc::clone(&self.metrics),
+                Arc::new(rustproxy_http::connection_pool::ConnectionPool::new()),
+                Arc::new(rustproxy_http::protocol_cache::ProtocolCache::new()),
+                rustproxy_passthrough::tls_handler::shared_backend_tls_config(),
+                std::time::Duration::from_secs(30),
+            );
+            udp_mgr.set_h3_service(Arc::new(h3_svc));
 
             for port in &udp_ports {
                 udp_mgr.add_port_with_tls(*port, quic_tls_config.clone()).await?;
@@ -763,22 +777,31 @@ impl RustProxy {
                 if self.udp_listener_manager.is_none() {
                     if let Some(ref listener) = self.listener_manager {
                         let conn_tracker = listener.conn_tracker().clone();
-                        self.udp_listener_manager = Some(UdpListenerManager::new(
+                        let conn_config = Self::build_connection_config(&self.options);
+                        let mut udp_mgr = UdpListenerManager::new(
                             Arc::clone(&new_manager),
                             Arc::clone(&self.metrics),
                             conn_tracker,
                             self.cancel_token.clone(),
-                        ));
+                        );
+                        udp_mgr.set_proxy_ips(conn_config.proxy_ips);
+                        self.udp_listener_manager = Some(udp_mgr);
                     }
                 }
 
+                // Build TLS config for QUIC (needed for new ports and upgrading existing raw UDP)
+                let quic_tls = {
+                    let tls_configs = self.current_tls_configs().await;
+                    Self::build_quic_tls_config(&tls_configs)
+                };
+
                 if let Some(ref mut udp_mgr) = self.udp_listener_manager {
                     udp_mgr.update_routes(Arc::clone(&new_manager));
 
-                    // Add new UDP ports
+                    // Add new UDP ports (with TLS for QUIC)
                     for port in &new_udp_ports {
                         if !old_udp_ports.contains(port) {
-                            udp_mgr.add_port(*port).await?;
+                            udp_mgr.add_port_with_tls(*port, quic_tls.clone()).await?;
                         }
                     }
                     // Remove old UDP ports
@@ -787,6 +810,12 @@ impl RustProxy {
                             udp_mgr.remove_port(*port);
                         }
                     }
+
+                    // Upgrade existing raw UDP fallback listeners to QUIC if TLS is now available
+                    if let Some(ref quic_config) = quic_tls {
+                        udp_mgr.update_quic_tls(Arc::clone(quic_config));
+                        udp_mgr.upgrade_raw_to_quic(Arc::clone(quic_config)).await;
+                    }
                 }
             } else if self.udp_listener_manager.is_some() {
                 // All UDP routes removed — shut down UDP manager
@@ -843,12 +872,12 @@ impl RustProxy {
             .map_err(|e| anyhow::anyhow!("ACME provisioning failed: {}", e))?;
 
         // Hot-swap into TLS configs
-        if let Some(ref mut listener) = self.listener_manager {
+        let mut tls_configs = Self::extract_tls_configs(&self.options.routes);
-            let mut tls_configs = Self::extract_tls_configs(&self.options.routes);
+        tls_configs.insert(domain.clone(), TlsCertConfig {
-            tls_configs.insert(domain.clone(), TlsCertConfig {
+            cert_pem: bundle.cert_pem.clone(),
-                cert_pem: bundle.cert_pem.clone(),
+            key_pem: bundle.key_pem.clone(),
-                key_pem: bundle.key_pem.clone(),
+        });
-            });
+        {
             let cm = cm_arc.lock().await;
             for (d, b) in cm.store().iter() {
                 if !tls_configs.contains_key(d) {
@@ -858,9 +887,22 @@ impl RustProxy {
                     });
                 }
             }
+        }
+
+        let quic_tls = Self::build_quic_tls_config(&tls_configs);
+
+        if let Some(ref listener) = self.listener_manager {
             listener.set_tls_configs(tls_configs);
         }
 
+        // Update existing QUIC endpoints and upgrade raw UDP fallback listeners
+        if let Some(ref mut udp_mgr) = self.udp_listener_manager {
+            if let Some(ref quic_config) = quic_tls {
+                udp_mgr.update_quic_tls(Arc::clone(quic_config));
+                udp_mgr.upgrade_raw_to_quic(Arc::clone(quic_config)).await;
+            }
+        }
+
         info!("Certificate provisioned and loaded for route '{}'", route_name);
         Ok(())
     }
@@ -1005,6 +1047,33 @@ impl RustProxy {
         Some(Arc::new(tls_config))
     }
 
+    /// Build the current full TLS config map from all sources (route configs, loaded certs, cert manager).
+    async fn current_tls_configs(&self) -> HashMap<String, TlsCertConfig> {
+        let mut configs = Self::extract_tls_configs(&self.options.routes);
+
+        // Merge dynamically loaded certs (from loadCertificate IPC)
+        for (d, c) in &self.loaded_certs {
+            if !configs.contains_key(d) {
+                configs.insert(d.clone(), c.clone());
+            }
+        }
+
+        // Merge certs from cert manager store
+        if let Some(ref cm_arc) = self.cert_manager {
+            let cm = cm_arc.lock().await;
+            for (d, b) in cm.store().iter() {
+                if !configs.contains_key(d) {
+                    configs.insert(d.clone(), TlsCertConfig {
+                        cert_pem: b.cert_pem.clone(),
+                        key_pem: b.key_pem.clone(),
+                    });
+                }
+            }
+        }
+
+        configs
+    }
+
     /// Set the Unix domain socket path for relaying UDP datagrams to TypeScript datagramHandler callbacks.
     pub async fn set_datagram_handler_relay_path(&mut self, path: Option<String>) {
         info!("Datagram handler relay path set to: {:?}", path);
@@ -1055,39 +1124,24 @@ impl RustProxy {
             key_pem: key_pem.clone(),
         });
 
-        // Hot-swap TLS config on the listener
+        // Hot-swap TLS config on TCP and QUIC listeners
-        if let Some(ref mut listener) = self.listener_manager {
+        let tls_configs = self.current_tls_configs().await;
-            let mut tls_configs = Self::extract_tls_configs(&self.options.routes);
 
-            // Add the new cert
+        // Build QUIC TLS config before TCP consumes the map
-            tls_configs.insert(domain.to_string(), TlsCertConfig {
+        let quic_tls = Self::build_quic_tls_config(&tls_configs);
-                cert_pem: cert_pem.clone(),
-                key_pem: key_pem.clone(),
-            });
-
-            // Also include all existing certs from cert manager
-            if let Some(ref cm_arc) = self.cert_manager {
-                let cm = cm_arc.lock().await;
-                for (d, b) in cm.store().iter() {
-                    if !tls_configs.contains_key(d) {
-                        tls_configs.insert(d.clone(), TlsCertConfig {
-                            cert_pem: b.cert_pem.clone(),
-                            key_pem: b.key_pem.clone(),
-                        });
-                    }
-                }
-            }
-
-            // Merge dynamically loaded certs from previous loadCertificate calls
-            for (d, c) in &self.loaded_certs {
-                if !tls_configs.contains_key(d) {
-                    tls_configs.insert(d.clone(), c.clone());
-                }
-            }
 
+        if let Some(ref listener) = self.listener_manager {
             listener.set_tls_configs(tls_configs);
         }
 
+        // Update existing QUIC endpoints and upgrade raw UDP fallback listeners
+        if let Some(ref mut udp_mgr) = self.udp_listener_manager {
+            if let Some(ref quic_config) = quic_tls {
+                udp_mgr.update_quic_tls(Arc::clone(quic_config));
+                udp_mgr.upgrade_raw_to_quic(Arc::clone(quic_config)).await;
+            }
+        }
+
         info!("Certificate loaded and TLS config updated for {}", domain);
         Ok(())
     }

ts/00_commitinfo_data.ts

@@ -3,6 +3,6 @@
  */
 export const commitinfo = {
   name: '@push.rocks/smartproxy',
-  version: '25.15.0',
+  version: '25.17.4',
   description: 'A powerful proxy package with unified route-based configuration for high traffic management. Features include SSL/TLS support, flexible routing patterns, WebSocket handling, advanced security options, and automatic ACME certificate management.'
 }

ts/proxies/smart-proxy/utils/route-validator.ts

@@ -7,7 +7,7 @@ import type { IRouteConfig, IRouteMatch, IRouteAction, TPortRange } from '../mod
 export class RouteValidator {
   private static readonly VALID_TLS_MODES = ['terminate', 'passthrough', 'terminate-and-reencrypt'];
   private static readonly VALID_ACTION_TYPES = ['forward', 'socket-handler'];
-  private static readonly VALID_PROTOCOLS = ['tcp', 'http', 'https', 'ws', 'wss'];
+  private static readonly VALID_PROTOCOLS = ['tcp', 'http', 'https', 'ws', 'wss', 'udp', 'quic', 'http3'];
   private static readonly MAX_PORTS = 100;
   private static readonly MAX_DOMAINS = 1000;
   private static readonly MAX_HEADER_SIZE = 8192;
@@ -173,6 +173,22 @@ export class RouteValidator {
           }
         }
       }
+
+      // QUIC routes require TLS with termination (QUIC mandates TLS 1.3)
+      if (route.action.udp?.quic && route.action.type === 'forward') {
+        if (!route.action.tls) {
+          errors.push('QUIC routes require TLS configuration (action.tls) — QUIC mandates TLS 1.3');
+        } else if (route.action.tls.mode === 'passthrough') {
+          errors.push('QUIC routes cannot use TLS mode "passthrough" — use "terminate" or "terminate-and-reencrypt"');
+        }
+      }
+
+      // Protocol quic/http3 requires transport udp or all
+      if (route.match?.protocol && ['quic', 'http3'].includes(route.match.protocol)) {
+        if (route.match.transport && route.match.transport !== 'udp' && route.match.transport !== 'all') {
+          errors.push(`Protocol "${route.match.protocol}" requires transport "udp" or "all"`);
+        }
+      }
     }
 
     // Validate security settings
@@ -619,6 +635,15 @@ export function validateRouteAction(action: IRouteAction): { valid: boolean; err
     }
   }
 
+  // QUIC routes require TLS with termination
+  if (action.udp?.quic && action.type === 'forward') {
+    if (!action.tls) {
+      errors.push('QUIC routes require TLS configuration — QUIC mandates TLS 1.3');
+    } else if (action.tls.mode === 'passthrough') {
+      errors.push('QUIC routes cannot use TLS mode "passthrough"');
+    }
+  }
+
   if (action.type === 'socket-handler') {
     if (!action.socketHandler && !action.datagramHandler) {
       errors.push('Socket handler or datagram handler function is required for socket-handler action');