[Fix] Syncronized Webserver & Host behaviour, Fixed the 10 sec default wait on auth

example/.gitignore

@@ -14,3 +14,4 @@ web-client/dist/
 client.id
 *.mk
 *.mpkb
+metrics/

example/Cargo.lock

@@ -237,6 +237,8 @@ version = "0.2.0"
 dependencies = [
  "mtp",
  "rand 0.10.2",
+ "serde",
+ "serde_json",
  "tokio",
  "tracing-subscriber",
 ]
@@ -1988,6 +1990,8 @@ dependencies = [
  "hex",
  "http",
  "mtp",
+ "rand 0.10.2",
+ "serde",
  "serde_json",
  "tokio",
  "tracing-subscriber",

example/client/Cargo.toml

@@ -12,3 +12,5 @@ mtp = { version = "0.2.0", path = "../../", features = ["client", "crypto", "fil
 tokio = { version = "1", features = ["full"] }
 rand = "0.10.1"
 tracing-subscriber = "0.3.23"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"

example/client/src/auth.rs

@@ -1,4 +1,4 @@
-use std::time::Instant;
+use std::time::{Duration, Instant};
 
 use tokio::fs;
 
@@ -12,7 +12,7 @@ pub async fn connect_or_register(
     mut config: ClientConfig,
     host_public_key: PublicKeyBundle,
     key_prefix: &str,
-) -> Result<(MTPConnection, Keyring), Box<dyn std::error::Error>> {
+) -> Result<(MTPConnection, Keyring, String, Duration), Box<dyn std::error::Error>> {
     let keyring_path = format!("{key_prefix}.mk");
     let id_path = format!("{key_prefix}.id");
 
@@ -30,12 +30,12 @@ pub async fn connect_or_register(
         config.client_id = client_id;
         let auth_started = Instant::now();
         let conn = MTPClient::auth_connect(config, &keyring, &host_public_key).await?;
+        let auth_duration = auth_started.elapsed();
         println!(
             "Authenticated (version {}) in {:?}",
-            conn.version,
+            conn.version, auth_duration
-            auth_started.elapsed()
         );
-        return Ok((conn, keyring));
+        return Ok((conn, keyring, "connect".into(), auth_duration));
     }
 
     println!("No existing keys found: registering new client");
@@ -52,12 +52,14 @@ pub async fn connect_or_register(
         sig_sk,
     );
 
+    let reg_started = Instant::now();
     let conn = MTPClient::auth_register(config, &keyring, &host_public_key).await?;
-    println!("Registered with ID: {}", conn.client_id);
+    let reg_duration = reg_started.elapsed();
+    println!("Registered with ID: {} in {:?}", conn.client_id, reg_duration);
 
     save_keyring_raw(&keyring, &keyring_path)?;
     fs::write(&id_path, conn.client_id.to_string()).await?;
     println!("Saved client keys -> {keyring_path}");
 
-    Ok((conn, keyring))
+    Ok((conn, keyring, "register".into(), reg_duration))
 }

example/client/src/main.rs

@@ -1,9 +1,11 @@
 mod auth;
+mod metrics;
 mod messages;
 mod pipes;
 
 use std::fs;
 use std::path::Path;
+use std::time::Duration;
 
 use mtp::client::ClientConfig;
 use mtp::files::load_public_key_bundle;
@@ -36,6 +38,8 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         }
     };
 
+    let mut client_metrics = metrics::ClientMetrics::load("metrics/client_sessions.json");
+
     println!("Connecting to 127.0.0.1:8080 ...");
 
     let config = ClientConfig::new("https://127.0.0.1:8080")
@@ -43,11 +47,43 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         .with_description("MTP example client");
 
     let server_bundle = host_public_key.clone();
-    let (conn, keyring) = auth::connect_or_register(config, host_public_key, "client").await?;
+    let (conn, keyring, auth_method, auth_duration) =
-    messages::send_and_receive(&conn, &keyring, &server_bundle).await?;
+        match auth::connect_or_register(config, host_public_key, "client").await {
+            Ok(result) => result,
+            Err(e) => {
+                let mut builder = metrics::SessionBuilder::new("failed", Duration::from_secs(0));
+                builder.set_error(e.to_string());
+                client_metrics.record_session(builder.build());
+                client_metrics.save("metrics/client_sessions.json");
+                client_metrics.build_overview("metrics/client_overview.json");
+                return Err(e);
+            }
+        };
+
+    let mut builder = metrics::SessionBuilder::new(&auth_method, auth_duration);
+
+    let roundtrip = messages::send_and_receive(&conn, &keyring, &server_bundle).await?;
+    builder.set_message_roundtrip(roundtrip);
 
     println!("\n--- Pipe demo ---");
-    pipes::run_pipe_demo(&conn, 1).await?;
+    let pipe_results = pipes::run_pipe_demo(&conn, 1).await?;
+    for result in &pipe_results {
+        builder.add_pipe_result(result.clone());
+    }
+
+    let session_record = builder.build();
+    println!(
+        "\nSession {} complete: auth={}ms, msg_roundtrip={}ms, pipes={} results, pipe_bytes={}",
+        session_record.session_id,
+        session_record.auth_duration_ms,
+        session_record.message_roundtrip_ms,
+        session_record.pipe_results.len(),
+        session_record.total_pipe_bytes,
+    );
+
+    client_metrics.record_session(session_record);
+    client_metrics.save("metrics/client_sessions.json");
+    client_metrics.build_overview("metrics/client_overview.json");
 
     conn.sender.close().await;
     println!("\nDone");

example/client/src/messages.rs

@@ -1,3 +1,5 @@
+use std::time::{Duration, Instant};
+
 use mtp::client::MTPConnection;
 use mtp::codec::{CommunicationType, CommunicationValue, DataType, DataValue};
 use mtp::crypto::{Ed25519Signer, EncryptionType, Keyring, PublicKeyBundle, SigAlgorithm};
@@ -89,17 +91,22 @@ pub async fn send_and_receive(
     conn: &MTPConnection,
     keyring: &Keyring,
     server_bundle: &PublicKeyBundle,
-) -> Result<(), Box<dyn std::error::Error>> {
+) -> Result<Duration, Box<dyn std::error::Error>> {
     let msg = build_demo_message(conn.client_id, keyring, server_bundle)?;
     println!("Sending: {msg}");
+    let start = Instant::now();
     conn.sender.send(&msg).await?;
 
     match conn.receive().await {
         Ok(resp) => {
+            let roundtrip = start.elapsed();
             println!("Received: {resp}");
+            println!("Message round-trip: {:.3}ms", roundtrip.as_secs_f64() * 1000.0);
+            Ok(roundtrip)
+        }
+        Err(e) => {
+            eprintln!("Receive error: {e}");
+            Err(e.into())
         }
-        Err(e) => eprintln!("Receive error: {e}"),
     }
-
-    Ok(())
 }

example/client/src/metrics.rs

@@ -0,0 +1,554 @@
+use serde::{Deserialize, Serialize};
+use std::path::Path;
+use std::time::{Duration, SystemTime, UNIX_EPOCH};
+
+fn now_epoch_secs() -> u64 {
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs()
+}
+
+fn generate_session_id() -> String {
+    let ts = now_epoch_secs();
+    let rand_part: u32 = rand::random();
+    format!("{ts}-{rand_part:08x}")
+}
+
+// ---------------------------------------------------------------------------
+// Persisted data types
+// ---------------------------------------------------------------------------
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+pub struct PipeResult {
+    pub size: usize,
+    pub iteration: usize,
+    pub total_ms: f64,
+    pub data_only_ms: f64,
+    pub bytes_matched: bool,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+pub struct ClientSessionRecord {
+    pub session_id: String,
+    pub timestamp: u64,
+    pub auth_method: String,
+    pub auth_duration_ms: f64,
+    pub error: Option<String>,
+    pub message_roundtrip_ms: f64,
+    pub pipe_results: Vec<PipeResult>,
+    pub total_pipe_bytes: u64,
+    pub overall_pipe_avg_total_ms: f64,
+    pub overall_pipe_avg_data_ms: f64,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, Default)]
+pub struct ClientAggregateStats {
+    pub total_sessions: u64,
+    pub auth_failures: u64,
+    pub avg_auth_duration_ms: f64,
+    pub avg_message_roundtrip_ms: f64,
+    pub avg_pipe_total_ms: f64,
+    pub avg_pipe_data_ms: f64,
+    pub total_pipe_bytes: u64,
+    pub avg_pipe_throughput_mbps: f64,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ClientOverview {
+    pub total_sessions: u64,
+    pub aggregate: ClientAggregateStats,
+    pub sessions: Vec<ClientSessionRecord>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, Default)]
+pub struct ClientMetricsFile {
+    pub sessions: Vec<ClientSessionRecord>,
+}
+
+// ---------------------------------------------------------------------------
+// Live metrics state
+// ---------------------------------------------------------------------------
+
+pub struct ClientMetrics {
+    sessions: Vec<ClientSessionRecord>,
+}
+
+impl ClientMetrics {
+    pub fn new() -> Self {
+        Self {
+            sessions: Vec::new(),
+        }
+    }
+
+    pub fn load(path: &str) -> Self {
+        let file = std::fs::read_to_string(path)
+            .ok()
+            .and_then(|s| serde_json::from_str::<ClientMetricsFile>(&s).ok());
+
+        Self {
+            sessions: file.map(|f| f.sessions).unwrap_or_default(),
+        }
+    }
+
+    pub fn save(&self, path: &str) {
+        let data = ClientMetricsFile {
+            sessions: self.sessions.clone(),
+        };
+        if let Some(parent) = Path::new(path).parent() {
+            let _ = std::fs::create_dir_all(parent);
+        }
+        let json = serde_json::to_string_pretty(&data).unwrap_or_default();
+        let _ = std::fs::write(path, json);
+    }
+
+    pub fn record_session(&mut self, record: ClientSessionRecord) {
+        self.sessions.push(record);
+    }
+
+    pub fn build_overview(&self, overview_path: &str) {
+        let total = self.sessions.len() as u64;
+
+        if total == 0 {
+            let overview = ClientOverview {
+                total_sessions: 0,
+                aggregate: ClientAggregateStats::default(),
+                sessions: Vec::new(),
+            };
+            if let Some(parent) = Path::new(overview_path).parent() {
+                let _ = std::fs::create_dir_all(parent);
+            }
+            let json = serde_json::to_string_pretty(&overview).unwrap_or_default();
+            let _ = std::fs::write(overview_path, json);
+            return;
+        }
+
+        let mut auth_sum: f64 = 0.0;
+        let mut msg_sum: f64 = 0.0;
+        let mut pipe_total_sum: f64 = 0.0;
+        let mut pipe_data_sum: f64 = 0.0;
+        let mut total_pipe_bytes: u64 = 0;
+        let mut total_pipe_duration_secs: f64 = 0.0;
+        let mut auth_failures: u64 = 0;
+        let mut success_count: u64 = 0;
+
+        for s in &self.sessions {
+            if s.error.is_some() {
+                auth_failures += 1;
+            } else {
+                success_count += 1;
+                auth_sum += s.auth_duration_ms;
+                msg_sum += s.message_roundtrip_ms;
+                pipe_total_sum += s.overall_pipe_avg_total_ms;
+                pipe_data_sum += s.overall_pipe_avg_data_ms;
+                total_pipe_bytes += s.total_pipe_bytes;
+                for pr in &s.pipe_results {
+                    total_pipe_duration_secs += pr.total_ms / 1000.0;
+                }
+            }
+        }
+
+        let divisor = if success_count > 0 { success_count } else { 1 };
+
+        let aggregate = ClientAggregateStats {
+            total_sessions: total,
+            auth_failures,
+            avg_auth_duration_ms: auth_sum / divisor as f64,
+            avg_message_roundtrip_ms: msg_sum / divisor as f64,
+            avg_pipe_total_ms: pipe_total_sum / divisor as f64,
+            avg_pipe_data_ms: pipe_data_sum / divisor as f64,
+            total_pipe_bytes,
+            avg_pipe_throughput_mbps: if total_pipe_duration_secs > 0.0 {
+                (total_pipe_bytes as f64 / 1_048_576.0) / total_pipe_duration_secs
+            } else {
+                0.0
+            },
+        };
+
+        let overview = ClientOverview {
+            total_sessions: total,
+            aggregate,
+            sessions: self.sessions.clone(),
+        };
+
+        if let Some(parent) = Path::new(overview_path).parent() {
+            let _ = std::fs::create_dir_all(parent);
+        }
+        let json = serde_json::to_string_pretty(&overview).unwrap_or_default();
+        let _ = std::fs::write(overview_path, json);
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Builder for constructing a session record piece by piece
+// ---------------------------------------------------------------------------
+
+pub struct SessionBuilder {
+    session_id: String,
+    timestamp: u64,
+    auth_method: String,
+    auth_duration_ms: f64,
+    error: Option<String>,
+    message_roundtrip_ms: f64,
+    pipe_results: Vec<PipeResult>,
+}
+
+impl SessionBuilder {
+    pub fn new(auth_method: &str, auth_duration: Duration) -> Self {
+        Self {
+            session_id: generate_session_id(),
+            timestamp: now_epoch_secs(),
+            auth_method: auth_method.to_string(),
+            auth_duration_ms: auth_duration.as_secs_f64() * 1000.0,
+            error: None,
+            message_roundtrip_ms: 0.0,
+            pipe_results: Vec::new(),
+        }
+    }
+
+    pub fn set_error(&mut self, error: String) {
+        self.error = Some(error);
+    }
+
+    pub fn set_message_roundtrip(&mut self, duration: Duration) {
+        self.message_roundtrip_ms = duration.as_secs_f64() * 1000.0;
+    }
+
+    pub fn add_pipe_result(&mut self, result: PipeResult) {
+        self.pipe_results.push(result);
+    }
+
+    pub fn build(self) -> ClientSessionRecord {
+        let total_pipe_bytes: u64 = self
+            .pipe_results
+            .iter()
+            .map(|r| r.size as u64)
+            .sum();
+
+        let overall_pipe_avg_total_ms = if self.pipe_results.is_empty() {
+            0.0
+        } else {
+            self.pipe_results.iter().map(|r| r.total_ms).sum::<f64>()
+                / self.pipe_results.len() as f64
+        };
+
+        let overall_pipe_avg_data_ms = if self.pipe_results.is_empty() {
+            0.0
+        } else {
+            self.pipe_results.iter().map(|r| r.data_only_ms).sum::<f64>()
+                / self.pipe_results.len() as f64
+        };
+
+        ClientSessionRecord {
+            session_id: self.session_id,
+            timestamp: self.timestamp,
+            auth_method: self.auth_method,
+            auth_duration_ms: self.auth_duration_ms,
+            error: self.error,
+            message_roundtrip_ms: self.message_roundtrip_ms,
+            pipe_results: self.pipe_results,
+            total_pipe_bytes,
+            overall_pipe_avg_total_ms,
+            overall_pipe_avg_data_ms,
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::time::Duration;
+
+    fn tmp_path(name: &str) -> String {
+        let dir = std::env::temp_dir().join("mtp_client_metrics_test");
+        let _ = std::fs::create_dir_all(&dir);
+        dir.join(name).to_str().unwrap().to_string()
+    }
+
+    #[test]
+    fn test_pipe_result_roundtrip() {
+        let pr = PipeResult {
+            size: 1024,
+            iteration: 0,
+            total_ms: 5.5,
+            data_only_ms: 3.2,
+            bytes_matched: true,
+        };
+        let json = serde_json::to_string(&pr).unwrap();
+        let decoded: PipeResult = serde_json::from_str(&json).unwrap();
+        assert_eq!(pr, decoded);
+    }
+
+    #[test]
+    fn test_client_session_roundtrip() {
+        let record = ClientSessionRecord {
+            session_id: "test-session".into(),
+            timestamp: 12345,
+            auth_method: "connect".into(),
+            auth_duration_ms: 42.5,
+            error: None,
+            message_roundtrip_ms: 10.3,
+            pipe_results: vec![
+                PipeResult {
+                    size: 64,
+                    iteration: 0,
+                    total_ms: 1.0,
+                    data_only_ms: 0.5,
+                    bytes_matched: true,
+                },
+                PipeResult {
+                    size: 256,
+                    iteration: 0,
+                    total_ms: 2.0,
+                    data_only_ms: 1.0,
+                    bytes_matched: true,
+                },
+            ],
+            total_pipe_bytes: 320,
+            overall_pipe_avg_total_ms: 1.5,
+            overall_pipe_avg_data_ms: 0.75,
+        };
+
+        let json = serde_json::to_string(&record).unwrap();
+        let decoded: ClientSessionRecord = serde_json::from_str(&json).unwrap();
+        assert_eq!(record, decoded);
+    }
+
+    #[test]
+    fn test_client_metrics_load_missing() {
+        let metrics = ClientMetrics::load("/nonexistent/path.json");
+        assert!(metrics.sessions.is_empty());
+    }
+
+    #[test]
+    fn test_multiple_client_sessions() {
+        let path = tmp_path("multi_session.json");
+        let mut metrics = ClientMetrics::load(&path);
+
+        for i in 0..3 {
+            let mut builder = SessionBuilder::new("connect", Duration::from_millis(10 + i));
+            builder.set_message_roundtrip(Duration::from_millis(5 + i));
+            builder.add_pipe_result(PipeResult {
+                size: 64,
+                iteration: 0,
+                total_ms: 1.0 + i as f64,
+                data_only_ms: 0.5 + i as f64 * 0.5,
+                bytes_matched: true,
+            });
+            metrics.record_session(builder.build());
+        }
+
+        metrics.save(&path);
+
+        let metrics2 = ClientMetrics::load(&path);
+        assert_eq!(metrics2.sessions.len(), 3);
+        assert_eq!(metrics2.sessions[0].auth_method, "connect");
+        assert_eq!(metrics2.sessions[1].pipe_results[0].size, 64);
+
+        let _ = std::fs::remove_file(&path);
+    }
+
+    #[test]
+    fn test_client_overview_stats() {
+        let mut metrics = ClientMetrics::new();
+
+        for i in 0..4 {
+            let mut builder = SessionBuilder::new("connect", Duration::from_millis(20));
+            builder.set_message_roundtrip(Duration::from_millis(10 + i as u64));
+            builder.add_pipe_result(PipeResult {
+                size: 256,
+                iteration: 0,
+                total_ms: 2.0,
+                data_only_ms: 1.0,
+                bytes_matched: true,
+            });
+            metrics.record_session(builder.build());
+        }
+
+        let overview_path = tmp_path("client_overview.json");
+        metrics.build_overview(&overview_path);
+
+        let json = std::fs::read_to_string(&overview_path).unwrap();
+        let overview: ClientOverview = serde_json::from_str(&json).unwrap();
+
+        assert_eq!(overview.total_sessions, 4);
+        assert_eq!(overview.aggregate.avg_auth_duration_ms, 20.0);
+        assert_eq!(overview.aggregate.avg_message_roundtrip_ms, 11.5);
+        assert_eq!(overview.aggregate.avg_pipe_total_ms, 2.0);
+        assert_eq!(overview.aggregate.avg_pipe_data_ms, 1.0);
+        assert_eq!(overview.aggregate.total_pipe_bytes, 1024);
+        assert!(overview.aggregate.avg_pipe_throughput_mbps > 0.0);
+        assert_eq!(overview.sessions.len(), 4);
+
+        let _ = std::fs::remove_file(&overview_path);
+    }
+
+    #[test]
+    fn test_client_overview_empty() {
+        let metrics = ClientMetrics::new();
+        let overview_path = tmp_path("client_empty_overview.json");
+        metrics.build_overview(&overview_path);
+
+        let json = std::fs::read_to_string(&overview_path).unwrap();
+        let overview: ClientOverview = serde_json::from_str(&json).unwrap();
+        assert_eq!(overview.total_sessions, 0);
+        assert!(overview.sessions.is_empty());
+
+        let _ = std::fs::remove_file(&overview_path);
+    }
+
+    #[test]
+    fn test_auth_failure_recording() {
+        let path = tmp_path("auth_failure.json");
+        let overview_path = tmp_path("auth_failure_overview.json");
+
+        let mut metrics = ClientMetrics::load(&path);
+
+        // Successful session
+        let mut b1 = SessionBuilder::new("connect", Duration::from_millis(42));
+        b1.set_message_roundtrip(Duration::from_millis(10));
+        metrics.record_session(b1.build());
+
+        // Failed auth session
+        let mut b2 = SessionBuilder::new("connect", Duration::from_millis(5000));
+        b2.set_error("authentication timed out".into());
+        metrics.record_session(b2.build());
+
+        // Another successful session
+        let mut b3 = SessionBuilder::new("register", Duration::from_millis(100));
+        b3.set_message_roundtrip(Duration::from_millis(8));
+        metrics.record_session(b3.build());
+
+        metrics.save(&path);
+        let metrics2 = ClientMetrics::load(&path);
+        assert_eq!(metrics2.sessions.len(), 3);
+        assert!(metrics2.sessions[0].error.is_none());
+        assert_eq!(
+            metrics2.sessions[1].error.as_deref(),
+            Some("authentication timed out")
+        );
+        assert!(metrics2.sessions[2].error.is_none());
+
+        metrics2.build_overview(&overview_path);
+        let overview_json = std::fs::read_to_string(&overview_path).unwrap();
+        let overview: ClientOverview = serde_json::from_str(&overview_json).unwrap();
+
+        assert_eq!(overview.total_sessions, 3);
+        assert_eq!(overview.aggregate.auth_failures, 1);
+        // Averages should only count successful sessions
+        assert!((overview.aggregate.avg_auth_duration_ms - 71.0).abs() < 0.01); // (42+100)/2
+        assert!((overview.aggregate.avg_message_roundtrip_ms - 9.0).abs() < 0.01); // (10+8)/2
+
+        let _ = std::fs::remove_file(&path);
+        let _ = std::fs::remove_file(&overview_path);
+    }
+
+    // -----------------------------------------------------------------------
+    // Integration-style tests
+    // -----------------------------------------------------------------------
+
+    fn make_pr(size: usize, iteration: usize, total_ms: f64, data_only_ms: f64) -> PipeResult {
+        PipeResult {
+            size,
+            iteration,
+            total_ms,
+            data_only_ms,
+            bytes_matched: true,
+        }
+    }
+
+    #[test]
+    fn test_full_client_lifecycle() {
+        let path = tmp_path("client_lifecycle.json");
+        let overview_path = tmp_path("client_lifecycle_overview.json");
+
+        let mut metrics = ClientMetrics::load(&path);
+
+        let mut b1 = SessionBuilder::new("connect", Duration::from_millis(42));
+        b1.set_message_roundtrip(Duration::from_millis(10));
+        b1.add_pipe_result(make_pr(64, 0, 1.5, 0.8));
+        b1.add_pipe_result(make_pr(256, 0, 2.5, 1.2));
+        metrics.record_session(b1.build());
+
+        let mut b2 = SessionBuilder::new("register", Duration::from_millis(150));
+        b2.set_message_roundtrip(Duration::from_millis(15));
+        b2.add_pipe_result(make_pr(64, 0, 2.0, 1.0));
+        b2.add_pipe_result(make_pr(1024, 0, 5.0, 3.0));
+        metrics.record_session(b2.build());
+
+        metrics.save(&path);
+        let metrics2 = ClientMetrics::load(&path);
+        assert_eq!(metrics2.sessions.len(), 2);
+
+        let s1 = &metrics2.sessions[0];
+        assert_eq!(s1.auth_method, "connect");
+        assert!((s1.auth_duration_ms - 42.0).abs() < 0.01);
+        assert!((s1.message_roundtrip_ms - 10.0).abs() < 0.01);
+        assert_eq!(s1.pipe_results.len(), 2);
+        assert_eq!(s1.total_pipe_bytes, 320);
+        assert!((s1.overall_pipe_avg_total_ms - 2.0).abs() < 0.01);
+        assert!((s1.overall_pipe_avg_data_ms - 1.0).abs() < 0.01);
+
+        let s2 = &metrics2.sessions[1];
+        assert_eq!(s2.auth_method, "register");
+        assert_eq!(s2.pipe_results.len(), 2);
+        assert_eq!(s2.total_pipe_bytes, 1088);
+
+        metrics2.build_overview(&overview_path);
+        let overview_json = std::fs::read_to_string(&overview_path).unwrap();
+        let overview: ClientOverview = serde_json::from_str(&overview_json).unwrap();
+        assert_eq!(overview.total_sessions, 2);
+        assert!((overview.aggregate.avg_auth_duration_ms - 96.0).abs() < 0.01);
+        assert!((overview.aggregate.avg_message_roundtrip_ms - 12.5).abs() < 0.01);
+        assert_eq!(overview.aggregate.total_pipe_bytes, 1408);
+        assert!(overview.aggregate.avg_pipe_throughput_mbps > 0.0);
+
+        let _ = std::fs::remove_file(&path);
+        let _ = std::fs::remove_file(&overview_path);
+    }
+
+    #[test]
+    fn test_cross_session_accumulation() {
+        let path = tmp_path("client_accumulate.json");
+        let overview_path = tmp_path("client_accumulate_overview.json");
+
+        {
+            let mut metrics = ClientMetrics::load(&path);
+            let mut b = SessionBuilder::new("connect", Duration::from_millis(30));
+            b.set_message_roundtrip(Duration::from_millis(8));
+            b.add_pipe_result(make_pr(64, 0, 1.0, 0.5));
+            metrics.record_session(b.build());
+            metrics.save(&path);
+        }
+
+        {
+            let mut metrics = ClientMetrics::load(&path);
+            assert_eq!(metrics.sessions.len(), 1);
+            let mut b = SessionBuilder::new("register", Duration::from_millis(200));
+            b.set_message_roundtrip(Duration::from_millis(12));
+            b.add_pipe_result(make_pr(1024, 0, 4.0, 2.5));
+            metrics.record_session(b.build());
+            metrics.save(&path);
+        }
+
+        let metrics = ClientMetrics::load(&path);
+        assert_eq!(metrics.sessions.len(), 2);
+        assert_eq!(metrics.sessions[0].auth_method, "connect");
+        assert_eq!(metrics.sessions[1].auth_method, "register");
+
+        metrics.build_overview(&overview_path);
+        let overview_json = std::fs::read_to_string(&overview_path).unwrap();
+        let overview: ClientOverview = serde_json::from_str(&overview_json).unwrap();
+        assert_eq!(overview.total_sessions, 2);
+        assert!((overview.aggregate.avg_auth_duration_ms - 115.0).abs() < 0.01);
+        assert!((overview.aggregate.avg_message_roundtrip_ms - 10.0).abs() < 0.01);
+        assert_eq!(overview.aggregate.total_pipe_bytes, 1088);
+
+        let _ = std::fs::remove_file(&path);
+        let _ = std::fs::remove_file(&overview_path);
+    }
+}

example/client/src/pipes.rs

@@ -3,13 +3,16 @@ use tokio::io::{AsyncReadExt, AsyncWriteExt};
 use tokio::sync::oneshot;
 use tokio::time::{Duration, Instant};
 
+use crate::metrics::PipeResult;
+
 pub async fn run_pipe_demo(
     conn: &MTPConnection,
     iterations: usize,
-) -> Result<(), Box<dyn std::error::Error>> {
+) -> Result<Vec<PipeResult>, Box<dyn std::error::Error>> {
     let sizes = [64, 256, 1024, 4096];
     let mut all_elapsed = Vec::with_capacity(sizes.len() * iterations);
     let mut all_data_only = Vec::with_capacity(sizes.len() * iterations);
+    let mut pipe_results = Vec::with_capacity(sizes.len() * iterations);
 
     for (i, &size) in sizes.iter().enumerate() {
         let mut size_elapsed = Vec::with_capacity(iterations);
@@ -97,6 +100,14 @@ pub async fn run_pipe_demo(
                 data_only_elapsed.as_secs_f64() * 1000.0,
             );
 
+            pipe_results.push(PipeResult {
+                size,
+                iteration: run,
+                total_ms: overall_elapsed.as_secs_f64() * 1000.0,
+                data_only_ms: data_only_elapsed.as_secs_f64() * 1000.0,
+                bytes_matched: matches,
+            });
+
             size_elapsed.push(overall_elapsed);
             size_data_only.push(data_only_elapsed);
             all_elapsed.push(overall_elapsed);
@@ -123,7 +134,7 @@ pub async fn run_pipe_demo(
         all_elapsed.len()
     );
 
-    Ok(())
+    Ok(pipe_results)
 }
 
 /// Helper: average a slice of Durations without overflowing.

example/server/Cargo.toml

@@ -15,3 +15,5 @@ serde_json = { version = "1" }
 hex = "0.4"
 base64 = "0.22"
 tracing-subscriber = "0.3.23"
+serde = { version = "1", features = ["derive"] }
+rand = "0.10.1"

example/server/src/main.rs

@@ -1,6 +1,7 @@
 mod clients;
 mod handlers;
 mod keys;
+mod metrics;
 mod tls;
 #[path = "web-server.rs"]
 mod web_server;
@@ -39,7 +40,7 @@ async fn handle_pipe_loopback(
         mtp::webserver::WebMtpSender,
         mtp::webserver::H3TransportReceiver,
     >,
-) -> Result<(), Box<dyn std::error::Error>> {
+) -> Result<u64, Box<dyn std::error::Error>> {
     let pipe_id = request.id();
     println!("  [loopback] Accepting pipe {pipe_id} ...");
     let mut reader = request.accept().await?;
@@ -56,7 +57,7 @@ async fn handle_pipe_loopback(
     let copied = tokio::io::copy(&mut reader, &mut writer).await?;
     writer.finish_async().await?;
     println!("  [loopback] Pipe {pipe_id} complete ({copied} bytes)");
-    Ok(())
+    Ok(copied)
 }
 
 #[tokio::main]
@@ -119,6 +120,10 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         },
     );
 
+    let metrics = std::sync::Arc::new(metrics::ServerMetrics::load(
+        "metrics/server_sessions.json",
+    ));
+
     println!("Starting integrated MTP web server on port 8080 ...");
 
     let config = HostConfig::new(
@@ -138,8 +143,22 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     println!("TCP: HTTP/1.1 and HTTP/2");
     println!("UDP: HTTP/3 and WebTransport");
 
-    while let Some(conn) = host.accept().await? {
+    loop {
+        let conn = match host.accept().await {
+            Ok(Some(conn)) => conn,
+            Ok(None) => break,
+            Err(e) => {
+                let msg = e.to_string();
+                eprintln!("Accept error: {msg}");
+                metrics.record_accept_error();
+                metrics.save("metrics/server_sessions.json");
+                metrics.build_overview("metrics/server_overview.json");
+                continue;
+            }
+        };
         let decrypt_keyring = Arc::clone(&decrypt_keyring);
+        let metrics = Arc::clone(&metrics);
+        metrics.record_connection_version(&conn.version.to_string());
         tokio::spawn(async move {
             let desc = conn.description.as_deref().unwrap_or("(no description)");
             println!(
@@ -151,12 +170,14 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
             );
             println!("Client ID: {}", conn.client_id);
 
+            let mut session = metrics.start_session(conn.client_id, desc.to_string());
+
             let tm: &TypeMap = conn.codec.registry().get(&conn.version).unwrap();
 
             println!("Waiting for messages / pipe requests ...");
             let mut pipe_open = true;
             let mut message_open = true;
-            let mut messages_received = 0_u64;
+            let mut exit_reason = "normal".to_string();
 
             while pipe_open || message_open {
                 let activity = tokio::time::timeout(CONNECTION_IDLE_TIMEOUT, async {
@@ -165,8 +186,17 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
                         pipe_request = conn.receive_pipe(), if pipe_open => {
                             match pipe_request {
                                 Ok(request) => {
-                                    if let Err(error) = handle_pipe_loopback(&conn, request).await {
+                                    match handle_pipe_loopback(&conn, request).await {
-                                        eprintln!("  [loopback] Pipe error: {error}");
+                                        Ok(bytes) => {
+                                            session.record_pipe(bytes);
+                                        }
+                                        Err(error) => {
+                                            let msg = error.to_string();
+                                            if msg.contains("denied") {
+                                                session.record_pipe_denial();
+                                            }
+                                            eprintln!("  [loopback] Pipe error: {msg}");
+                                        }
                                     }
                                 }
                                 Err(mtp::common::CommunicationError::StreamClosed)
@@ -183,18 +213,24 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
                         message = conn.receive(), if message_open => {
                             match message {
                                 Ok(message) => {
-                                    messages_received += 1;
                                     println!("Received: {message}");
-                                    match handlers::process_and_respond(
+                                    let msg_start = std::time::Instant::now();
+                                    let result = handlers::process_and_respond(
                                         &message,
                                         tm,
                                         conn.client_public_key.as_ref(),
                                         &decrypt_keyring,
-                                    ) {
+                                    );
+                                    let latency = msg_start.elapsed();
+                                    let ok = result.is_ok();
+                                    session.record_message(latency, ok);
+
+                                    match result {
                                         Ok(response) => {
                                             println!("Sending: {response}");
                                             if let Err(error) = conn.sender.send(&response).await {
                                                 eprintln!("Send error: {error}");
+                                                session.record_send_error();
                                                 pipe_open = false;
                                                 message_open = false;
                                             }
@@ -220,16 +256,27 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
                 .await;
 
                 if activity.is_err() {
+                    exit_reason = "idle timeout".to_string();
                     println!("Connection idle timeout reached");
                     break;
                 }
-                if messages_received >= MAX_MESSAGES_PER_CONNECTION {
+                if session.messages_received() >= MAX_MESSAGES_PER_CONNECTION {
+                    exit_reason = "message limit".to_string();
                     println!("Connection message limit reached");
                     break;
                 }
             }
 
-            println!("Connection closed\n");
+            let record = session.finish(exit_reason);
+            println!(
+                "Connection closed (messages: {}, pipes: {}, duration: {:.1}s)\n",
+                record.messages_received,
+                record.pipes_handled,
+                record.duration_secs
+            );
+
+            metrics.save("metrics/server_sessions.json");
+            metrics.build_overview("metrics/server_overview.json");
         });
     }
 

example/server/src/metrics.rs

@@ -0,0 +1,883 @@
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+use std::path::Path;
+use std::sync::Mutex;
+use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
+
+fn now_epoch_secs() -> u64 {
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs()
+}
+
+fn generate_session_id() -> String {
+    let ts = now_epoch_secs();
+    let rand_part: u32 = rand::random();
+    format!("{ts}-{rand_part:08x}")
+}
+
+// ---------------------------------------------------------------------------
+// Persisted data types
+// ---------------------------------------------------------------------------
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+pub struct SessionRecord {
+    pub session_id: String,
+    pub client_id: u64,
+    pub description: String,
+    pub start_time: u64,
+    pub end_time: u64,
+    pub duration_secs: f64,
+    pub messages_received: u64,
+    pub messages_ok: u64,
+    pub messages_failed: u64,
+    pub pipes_handled: u64,
+    pub pipe_bytes_copied: u64,
+    pub pipe_denials: u64,
+    pub send_errors: u64,
+    pub avg_message_latency_ms: f64,
+    pub max_message_latency_ms: f64,
+    pub exit_reason: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, Default)]
+pub struct AggregateStats {
+    pub total_connections: u64,
+    pub total_messages: u64,
+    pub total_messages_ok: u64,
+    pub total_messages_failed: u64,
+    pub total_pipes: u64,
+    pub total_pipe_bytes: u64,
+    pub total_pipe_denials: u64,
+    pub total_send_errors: u64,
+    pub total_accept_errors: u64,
+    pub avg_session_duration_secs: f64,
+    pub avg_messages_per_session: f64,
+    pub avg_pipes_per_session: f64,
+    pub avg_message_latency_ms: f64,
+    pub max_message_latency_ms: f64,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Overview {
+    pub total_sessions: u64,
+    pub first_session_timestamp: u64,
+    pub last_session_timestamp: u64,
+    pub aggregate: AggregateStats,
+    pub connection_versions: HashMap<String, u64>,
+    pub sessions: Vec<SessionRecord>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, Default)]
+pub struct ServerMetricsFile {
+    pub total_connections: u64,
+    pub total_messages: u64,
+    pub total_messages_ok: u64,
+    pub total_messages_failed: u64,
+    pub total_pipes: u64,
+    pub total_pipe_bytes: u64,
+    pub total_pipe_denials: u64,
+    pub total_send_errors: u64,
+    pub total_accept_errors: u64,
+    pub connection_versions: HashMap<String, u64>,
+    pub sessions: Vec<SessionRecord>,
+}
+
+// ---------------------------------------------------------------------------
+// Live metrics state
+// ---------------------------------------------------------------------------
+
+struct Inner {
+    total_connections: u64,
+    total_messages: u64,
+    total_messages_ok: u64,
+    total_messages_failed: u64,
+    total_pipes: u64,
+    total_pipe_bytes: u64,
+    total_pipe_denials: u64,
+    total_send_errors: u64,
+    total_accept_errors: u64,
+    connection_versions: HashMap<String, u64>,
+    active_connections: u64,
+    completed_sessions: Vec<SessionRecord>,
+}
+
+pub struct ServerMetrics {
+    inner: Mutex<Inner>,
+}
+
+impl ServerMetrics {
+    pub fn new() -> Self {
+        Self {
+            inner: Mutex::new(Inner {
+                total_connections: 0,
+                total_messages: 0,
+                total_messages_ok: 0,
+                total_messages_failed: 0,
+                total_pipes: 0,
+                total_pipe_bytes: 0,
+                total_pipe_denials: 0,
+                total_send_errors: 0,
+                total_accept_errors: 0,
+                connection_versions: HashMap::new(),
+                active_connections: 0,
+                completed_sessions: Vec::new(),
+            }),
+        }
+    }
+
+    pub fn load(path: &str) -> Self {
+        let file = std::fs::read_to_string(path)
+            .ok()
+            .and_then(|s| serde_json::from_str::<ServerMetricsFile>(&s).ok());
+
+        let mut inner = Inner {
+            total_connections: 0,
+            total_messages: 0,
+            total_messages_ok: 0,
+            total_messages_failed: 0,
+            total_pipes: 0,
+            total_pipe_bytes: 0,
+            total_pipe_denials: 0,
+            total_send_errors: 0,
+            total_accept_errors: 0,
+            connection_versions: HashMap::new(),
+            active_connections: 0,
+            completed_sessions: Vec::new(),
+        };
+
+        if let Some(data) = file {
+            inner.total_connections = data.total_connections;
+            inner.total_messages = data.total_messages;
+            inner.total_messages_ok = data.total_messages_ok;
+            inner.total_messages_failed = data.total_messages_failed;
+            inner.total_pipes = data.total_pipes;
+            inner.total_pipe_bytes = data.total_pipe_bytes;
+            inner.total_pipe_denials = data.total_pipe_denials;
+            inner.total_send_errors = data.total_send_errors;
+            inner.total_accept_errors = data.total_accept_errors;
+            inner.connection_versions = data.connection_versions;
+            inner.completed_sessions = data.sessions;
+        }
+
+        Self {
+            inner: Mutex::new(inner),
+        }
+    }
+
+    pub fn save(&self, path: &str) {
+        let inner = self.inner.lock().unwrap();
+        let data = self.to_file(&inner);
+        if let Some(parent) = Path::new(path).parent() {
+            let _ = std::fs::create_dir_all(parent);
+        }
+        let json = serde_json::to_string_pretty(&data).unwrap_or_default();
+        let _ = std::fs::write(path, json);
+    }
+
+    fn to_file(&self, inner: &Inner) -> ServerMetricsFile {
+        ServerMetricsFile {
+            total_connections: inner.total_connections,
+            total_messages: inner.total_messages,
+            total_messages_ok: inner.total_messages_ok,
+            total_messages_failed: inner.total_messages_failed,
+            total_pipes: inner.total_pipes,
+            total_pipe_bytes: inner.total_pipe_bytes,
+            total_pipe_denials: inner.total_pipe_denials,
+            total_send_errors: inner.total_send_errors,
+            total_accept_errors: inner.total_accept_errors,
+            connection_versions: inner.connection_versions.clone(),
+            sessions: inner.completed_sessions.clone(),
+        }
+    }
+
+    pub fn start_session(&self, client_id: u64, description: String) -> SessionHandle<'_> {
+        let session_id = generate_session_id();
+        let start = Instant::now();
+        let start_time = now_epoch_secs();
+
+        self.inner.lock().unwrap().total_connections += 1;
+        self.inner.lock().unwrap().active_connections += 1;
+
+        SessionHandle {
+            metrics: self,
+            session_id,
+            client_id,
+            description,
+            start,
+            start_time,
+            messages_received: 0,
+            messages_ok: 0,
+            messages_failed: 0,
+            pipes_handled: 0,
+            pipe_bytes: 0,
+            pipe_denials: 0,
+            send_errors: 0,
+            latencies: Vec::new(),
+        }
+    }
+
+    pub fn snapshot(&self) -> ServerMetricsFile {
+        let inner = self.inner.lock().unwrap();
+        self.to_file(&inner)
+    }
+
+    pub fn record_accept_error(&self) {
+        self.inner.lock().unwrap().total_accept_errors += 1;
+    }
+
+    pub fn record_connection_version(&self, version: &str) {
+        *self
+            .inner
+            .lock()
+            .unwrap()
+            .connection_versions
+            .entry(version.to_string())
+            .or_insert(0) += 1;
+    }
+
+    pub fn build_overview(&self, overview_path: &str) {
+        let inner = self.inner.lock().unwrap();
+        let sessions = &inner.completed_sessions;
+        let total = sessions.len() as u64;
+
+        if total == 0 {
+            let overview = Overview {
+                total_sessions: 0,
+                first_session_timestamp: 0,
+                last_session_timestamp: 0,
+                aggregate: AggregateStats::default(),
+                connection_versions: HashMap::new(),
+                sessions: Vec::new(),
+            };
+            if let Some(parent) = Path::new(overview_path).parent() {
+                let _ = std::fs::create_dir_all(parent);
+            }
+            let json = serde_json::to_string_pretty(&overview).unwrap_or_default();
+            let _ = std::fs::write(overview_path, json);
+            return;
+        }
+
+        let first_ts = sessions.first().map(|s| s.start_time).unwrap_or(0);
+        let last_ts = sessions.last().map(|s| s.end_time).unwrap_or(0);
+
+        let total_duration: f64 = sessions.iter().map(|s| s.duration_secs).sum();
+        let total_msgs: u64 = sessions.iter().map(|s| s.messages_received).sum();
+        let total_pipes: u64 = sessions.iter().map(|s| s.pipes_handled).sum();
+
+        let mut max_latency: f64 = 0.0;
+        let mut latency_sum: f64 = 0.0;
+        let mut latency_count: u64 = 0;
+        for s in sessions {
+            if s.avg_message_latency_ms > 0.0 {
+                latency_sum += s.avg_message_latency_ms * s.messages_ok as f64;
+                latency_count += s.messages_ok;
+            }
+            if s.max_message_latency_ms > max_latency {
+                max_latency = s.max_message_latency_ms;
+            }
+        }
+
+        let aggregate = AggregateStats {
+            total_connections: inner.total_connections,
+            total_messages: inner.total_messages,
+            total_messages_ok: inner.total_messages_ok,
+            total_messages_failed: inner.total_messages_failed,
+            total_pipes: inner.total_pipes,
+            total_pipe_bytes: inner.total_pipe_bytes,
+            total_pipe_denials: inner.total_pipe_denials,
+            total_send_errors: inner.total_send_errors,
+            total_accept_errors: inner.total_accept_errors,
+            avg_session_duration_secs: total_duration / total as f64,
+            avg_messages_per_session: total_msgs as f64 / total as f64,
+            avg_pipes_per_session: total_pipes as f64 / total as f64,
+            avg_message_latency_ms: if latency_count > 0 {
+                latency_sum / latency_count as f64
+            } else {
+                0.0
+            },
+            max_message_latency_ms: max_latency,
+        };
+
+        let overview = Overview {
+            total_sessions: total,
+            first_session_timestamp: first_ts,
+            last_session_timestamp: last_ts,
+            aggregate,
+            connection_versions: inner.connection_versions.clone(),
+            sessions: sessions.clone(),
+        };
+
+        if let Some(parent) = Path::new(overview_path).parent() {
+            let _ = std::fs::create_dir_all(parent);
+        }
+        let json = serde_json::to_string_pretty(&overview).unwrap_or_default();
+        let _ = std::fs::write(overview_path, json);
+    }
+
+    fn finish_session(&self, record: SessionRecord) {
+        let mut inner = self.inner.lock().unwrap();
+        inner.active_connections -= 1;
+        inner.total_messages += record.messages_received;
+        inner.total_messages_ok += record.messages_ok;
+        inner.total_messages_failed += record.messages_failed;
+        inner.total_pipes += record.pipes_handled;
+        inner.total_pipe_bytes += record.pipe_bytes_copied;
+        inner.total_pipe_denials += record.pipe_denials;
+        inner.total_send_errors += record.send_errors;
+        inner.completed_sessions.push(record);
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Session handle — local accumulators, no mutex contention during connection
+// ---------------------------------------------------------------------------
+
+pub struct SessionHandle<'a> {
+    metrics: &'a ServerMetrics,
+    session_id: String,
+    client_id: u64,
+    description: String,
+    start: Instant,
+    start_time: u64,
+    messages_received: u64,
+    messages_ok: u64,
+    messages_failed: u64,
+    pipes_handled: u64,
+    pipe_bytes: u64,
+    pipe_denials: u64,
+    send_errors: u64,
+    latencies: Vec<f64>,
+}
+
+impl<'a> SessionHandle<'a> {
+    pub fn messages_received(&self) -> u64 {
+        self.messages_received
+    }
+
+    pub fn record_message(&mut self, latency: Duration, ok: bool) {
+        self.messages_received += 1;
+        if ok {
+            self.messages_ok += 1;
+        } else {
+            self.messages_failed += 1;
+        }
+        self.latencies.push(latency.as_secs_f64() * 1000.0);
+    }
+
+    pub fn record_pipe(&mut self, bytes: u64) {
+        self.pipes_handled += 1;
+        self.pipe_bytes += bytes;
+    }
+
+    pub fn record_pipe_denial(&mut self) {
+        self.pipe_denials += 1;
+    }
+
+    pub fn record_send_error(&mut self) {
+        self.send_errors += 1;
+    }
+
+    pub fn finish(self, exit_reason: String) -> SessionRecord {
+        let elapsed = self.start.elapsed();
+        let end_time = self.start_time + elapsed.as_secs();
+
+        let avg_latency = if self.latencies.is_empty() {
+            0.0
+        } else {
+            self.latencies.iter().sum::<f64>() / self.latencies.len() as f64
+        };
+        let max_latency = self.latencies.iter().copied().fold(0.0_f64, f64::max);
+
+        let record = SessionRecord {
+            session_id: self.session_id,
+            client_id: self.client_id,
+            description: self.description,
+            start_time: self.start_time,
+            end_time,
+            duration_secs: elapsed.as_secs_f64(),
+            messages_received: self.messages_received,
+            messages_ok: self.messages_ok,
+            messages_failed: self.messages_failed,
+            pipes_handled: self.pipes_handled,
+            pipe_bytes_copied: self.pipe_bytes,
+            pipe_denials: self.pipe_denials,
+            send_errors: self.send_errors,
+            avg_message_latency_ms: avg_latency,
+            max_message_latency_ms: max_latency,
+            exit_reason,
+        };
+
+        self.metrics.finish_session(record.clone());
+        record
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::time::Duration;
+
+    fn tmp_path(name: &str) -> String {
+        let dir = std::env::temp_dir().join("mtp_server_metrics_test");
+        let _ = std::fs::create_dir_all(&dir);
+        dir.join(name).to_str().unwrap().to_string()
+    }
+
+    #[test]
+    fn test_session_record_roundtrip() {
+        let record = SessionRecord {
+            session_id: "test-123".into(),
+            client_id: 1000,
+            description: "test session".into(),
+            start_time: 1000,
+            end_time: 1010,
+            duration_secs: 10.0,
+            messages_received: 5,
+            messages_ok: 4,
+            messages_failed: 1,
+            pipes_handled: 2,
+            pipe_bytes_copied: 4096,
+            pipe_denials: 0,
+            send_errors: 0,
+            avg_message_latency_ms: 1.5,
+            max_message_latency_ms: 3.0,
+            exit_reason: "normal".into(),
+        };
+
+        let json = serde_json::to_string(&record).unwrap();
+        let decoded: SessionRecord = serde_json::from_str(&json).unwrap();
+        assert_eq!(record, decoded);
+    }
+
+    #[test]
+    fn test_metrics_file_roundtrip() {
+        let file = ServerMetricsFile {
+            total_connections: 10,
+            total_messages: 50,
+            total_messages_ok: 48,
+            total_messages_failed: 2,
+            total_pipes: 5,
+            total_pipe_bytes: 20480,
+            total_pipe_denials: 1,
+            total_send_errors: 0,
+            total_accept_errors: 3,
+            connection_versions: HashMap::from([("2.0".into(), 8), ("1.0".into(), 2)]),
+            sessions: vec![
+                SessionRecord {
+                    session_id: "s1".into(),
+                    client_id: 1000,
+                    description: "first".into(),
+                    start_time: 100,
+                    end_time: 110,
+                    duration_secs: 10.0,
+                    messages_received: 3,
+                    messages_ok: 3,
+                    messages_failed: 0,
+                    pipes_handled: 1,
+                    pipe_bytes_copied: 1024,
+                    pipe_denials: 0,
+                    send_errors: 0,
+                    avg_message_latency_ms: 0.5,
+                    max_message_latency_ms: 1.0,
+                    exit_reason: "normal".into(),
+                },
+                SessionRecord {
+                    session_id: "s2".into(),
+                    client_id: 1001,
+                    description: "second".into(),
+                    start_time: 200,
+                    end_time: 230,
+                    duration_secs: 30.0,
+                    messages_received: 7,
+                    messages_ok: 6,
+                    messages_failed: 1,
+                    pipes_handled: 4,
+                    pipe_bytes_copied: 19456,
+                    pipe_denials: 1,
+                    send_errors: 0,
+                    avg_message_latency_ms: 2.0,
+                    max_message_latency_ms: 5.0,
+                    exit_reason: "idle timeout".into(),
+                },
+            ],
+        };
+
+        let json = serde_json::to_string_pretty(&file).unwrap();
+        let decoded: ServerMetricsFile = serde_json::from_str(&json).unwrap();
+        assert_eq!(file.total_connections, decoded.total_connections);
+        assert_eq!(file.sessions.len(), decoded.sessions.len());
+        assert_eq!(file.sessions[0], decoded.sessions[0]);
+        assert_eq!(file.sessions[1], decoded.sessions[1]);
+    }
+
+    #[test]
+    fn test_session_handle_lifecycle() {
+        let metrics = ServerMetrics::new();
+        let mut session = metrics.start_session(1000, "test".into());
+
+        session.record_message(Duration::from_millis(1), true);
+        session.record_message(Duration::from_millis(3), true);
+        session.record_message(Duration::from_millis(2), false);
+        session.record_pipe(512);
+
+        let record = session.finish("test exit".into());
+
+        assert_eq!(record.client_id, 1000);
+        assert_eq!(record.messages_received, 3);
+        assert_eq!(record.messages_ok, 2);
+        assert_eq!(record.messages_failed, 1);
+        assert_eq!(record.pipes_handled, 1);
+        assert_eq!(record.pipe_bytes_copied, 512);
+        assert!(record.avg_message_latency_ms > 0.0);
+        assert_eq!(record.max_message_latency_ms, 3.0);
+        assert_eq!(record.exit_reason, "test exit");
+
+        let snap = metrics.snapshot();
+        assert_eq!(snap.total_connections, 1);
+        assert_eq!(snap.total_messages, 3);
+        assert_eq!(snap.total_messages_ok, 2);
+        assert_eq!(snap.total_messages_failed, 1);
+        assert_eq!(snap.total_pipes, 1);
+        assert_eq!(snap.total_pipe_bytes, 512);
+        assert_eq!(snap.sessions.len(), 1);
+    }
+
+    #[test]
+    fn test_overview_generation() {
+        let metrics = ServerMetrics::new();
+
+        for i in 0..3 {
+            let mut session = metrics.start_session(1000 + i as u64, format!("session {i}"));
+            for _ in 0..(i + 1) * 2 {
+                session.record_message(Duration::from_millis(1 + i), true);
+            }
+            session.record_pipe((i as u64 + 1) * 1000);
+            session.finish(format!("exit {i}"));
+        }
+
+        let overview_path = tmp_path("overview_test.json");
+        metrics.build_overview(&overview_path);
+
+        let json = std::fs::read_to_string(&overview_path).unwrap();
+        let overview: Overview = serde_json::from_str(&json).unwrap();
+
+        assert_eq!(overview.total_sessions, 3);
+        assert!(overview.first_session_timestamp > 0);
+        assert!(overview.last_session_timestamp >= overview.first_session_timestamp);
+        assert_eq!(overview.aggregate.total_connections, 3);
+        assert_eq!(overview.aggregate.total_messages, 12); // 2+4+6
+        assert_eq!(overview.aggregate.total_pipes, 3);
+        assert_eq!(overview.aggregate.total_pipe_bytes, 6000); // 1000+2000+3000
+        assert!(overview.aggregate.avg_session_duration_secs >= 0.0);
+        assert_eq!(overview.sessions.len(), 3);
+
+        let _ = std::fs::remove_file(&overview_path);
+    }
+
+    #[test]
+    fn test_load_missing_file() {
+        let metrics = ServerMetrics::load("/nonexistent/path/metrics.json");
+        let snap = metrics.snapshot();
+        assert_eq!(snap.total_connections, 0);
+        assert!(snap.sessions.is_empty());
+    }
+
+    #[test]
+    fn test_multiple_sessions_accumulate() {
+        let path = tmp_path("accumulate_test.json");
+        let metrics = ServerMetrics::load(&path);
+
+        for i in 0..5 {
+            let mut session = metrics.start_session(1000, format!("s{i}"));
+            session.record_message(Duration::from_millis(1), true);
+            session.record_pipe(100);
+            session.finish(format!("done {i}"));
+        }
+
+        metrics.save(&path);
+
+        let metrics2 = ServerMetrics::load(&path);
+        let snap = metrics2.snapshot();
+        assert_eq!(snap.total_connections, 5);
+        assert_eq!(snap.total_messages, 5);
+        assert_eq!(snap.total_messages_ok, 5);
+        assert_eq!(snap.total_pipes, 5);
+        assert_eq!(snap.total_pipe_bytes, 500);
+        assert_eq!(snap.sessions.len(), 5);
+
+        let _ = std::fs::remove_file(&path);
+    }
+
+    #[test]
+    fn test_overview_latencies() {
+        let metrics = ServerMetrics::new();
+
+        let mut s1 = metrics.start_session(1000, "s1".into());
+        s1.record_message(Duration::from_millis(2), true);
+        s1.record_message(Duration::from_millis(4), true);
+        s1.finish("done".into());
+
+        let mut s2 = metrics.start_session(1001, "s2".into());
+        s2.record_message(Duration::from_millis(1), true);
+        s2.finish("done".into());
+
+        let overview_path = tmp_path("latency_overview.json");
+        metrics.build_overview(&overview_path);
+        let json = std::fs::read_to_string(&overview_path).unwrap();
+        let overview: Overview = serde_json::from_str(&json).unwrap();
+
+        // s1 avg = 3.0, s2 avg = 1.0
+        // weighted avg = (3*2 + 1*1) / 3 = 7/3 ≈ 2.333
+        assert!(
+            (overview.aggregate.avg_message_latency_ms - 7.0 / 3.0).abs() < 0.01,
+            "avg latency: {}",
+            overview.aggregate.avg_message_latency_ms
+        );
+        assert_eq!(overview.aggregate.max_message_latency_ms, 4.0);
+
+        let _ = std::fs::remove_file(&overview_path);
+    }
+
+    #[test]
+    fn test_overview_empty() {
+        let metrics = ServerMetrics::new();
+        let overview_path = tmp_path("empty_overview.json");
+        metrics.build_overview(&overview_path);
+
+        let json = std::fs::read_to_string(&overview_path).unwrap();
+        let overview: Overview = serde_json::from_str(&json).unwrap();
+        assert_eq!(overview.total_sessions, 0);
+        assert!(overview.sessions.is_empty());
+
+        let _ = std::fs::remove_file(&overview_path);
+    }
+
+    // -----------------------------------------------------------------------
+    // Integration-style tests
+    // -----------------------------------------------------------------------
+
+    #[test]
+    fn test_full_session_lifecycle() {
+        let path = tmp_path("lifecycle.json");
+        let overview_path = tmp_path("lifecycle_overview.json");
+
+        let metrics = ServerMetrics::load(&path);
+
+        let mut s1 = metrics.start_session(1000, "first".into());
+        s1.record_message(Duration::from_millis(1), true);
+        s1.record_message(Duration::from_millis(2), true);
+        let r1 = s1.finish("normal".into());
+
+        let mut s2 = metrics.start_session(1001, "second".into());
+        s2.record_message(Duration::from_millis(5), true);
+        s2.record_message(Duration::from_millis(3), false);
+        s2.record_pipe(2048);
+        s2.record_pipe(4096);
+        let r2 = s2.finish("idle timeout".into());
+
+        let mut s3 = metrics.start_session(1002, "third".into());
+        s3.record_pipe(1024);
+        let r3 = s3.finish("normal".into());
+
+        assert_eq!(r1.client_id, 1000);
+        assert_eq!(r1.messages_received, 2);
+        assert_eq!(r1.messages_ok, 2);
+        assert_eq!(r1.pipes_handled, 0);
+
+        assert_eq!(r2.client_id, 1001);
+        assert_eq!(r2.messages_received, 2);
+        assert_eq!(r2.messages_ok, 1);
+        assert_eq!(r2.messages_failed, 1);
+        assert_eq!(r2.pipes_handled, 2);
+        assert_eq!(r2.pipe_bytes_copied, 6144);
+        assert_eq!(r2.exit_reason, "idle timeout");
+
+        assert_eq!(r3.client_id, 1002);
+        assert_eq!(r3.messages_received, 0);
+        assert_eq!(r3.pipes_handled, 1);
+        assert_eq!(r3.pipe_bytes_copied, 1024);
+
+        let snap = metrics.snapshot();
+        assert_eq!(snap.total_connections, 3);
+        assert_eq!(snap.total_messages, 4);
+        assert_eq!(snap.total_messages_ok, 3);
+        assert_eq!(snap.total_messages_failed, 1);
+        assert_eq!(snap.total_pipes, 3);
+        assert_eq!(snap.total_pipe_bytes, 7168);
+        assert_eq!(snap.sessions.len(), 3);
+
+        metrics.save(&path);
+        let metrics2 = ServerMetrics::load(&path);
+        let snap2 = metrics2.snapshot();
+        assert_eq!(snap2.total_connections, 3);
+        assert_eq!(snap2.total_messages, 4);
+        assert_eq!(snap2.sessions.len(), 3);
+        assert_eq!(snap2.sessions[1].exit_reason, "idle timeout");
+
+        metrics2.build_overview(&overview_path);
+        let overview_json = std::fs::read_to_string(&overview_path).unwrap();
+        let overview: Overview = serde_json::from_str(&overview_json).unwrap();
+        assert_eq!(overview.total_sessions, 3);
+        assert_eq!(overview.aggregate.total_connections, 3);
+        assert_eq!(overview.aggregate.total_messages, 4);
+        assert_eq!(overview.aggregate.total_messages_ok, 3);
+        assert_eq!(overview.aggregate.total_messages_failed, 1);
+        assert_eq!(overview.aggregate.total_pipes, 3);
+        assert_eq!(overview.aggregate.total_pipe_bytes, 7168);
+        assert!(overview.aggregate.avg_session_duration_secs >= 0.0);
+        assert!(overview.aggregate.avg_messages_per_session > 0.0);
+        assert_eq!(overview.sessions.len(), 3);
+
+        let _ = std::fs::remove_file(&path);
+        let _ = std::fs::remove_file(&overview_path);
+    }
+
+    #[test]
+    fn test_overview_rebuild_accuracy() {
+        let path = tmp_path("accuracy.json");
+        let overview_path = tmp_path("accuracy_overview.json");
+
+        let metrics = ServerMetrics::load(&path);
+
+        for i in 0..10u32 {
+            let mut session = metrics.start_session(1000 + i as u64, format!("session {i}"));
+            let msg_count = (i + 1) * 2;
+            for j in 0..msg_count {
+                session.record_message(Duration::from_millis((j + 1) as u64), j % 3 != 0);
+            }
+            session.record_pipe((i as u64 + 1) * 512);
+            session.finish(format!("exit {i}"));
+        }
+
+        metrics.save(&path);
+        let metrics2 = ServerMetrics::load(&path);
+        metrics2.build_overview(&overview_path);
+
+        let overview_json = std::fs::read_to_string(&overview_path).unwrap();
+        let overview: Overview = serde_json::from_str(&overview_json).unwrap();
+
+        assert_eq!(overview.total_sessions, 10);
+        assert_eq!(overview.aggregate.total_connections, 10);
+        assert_eq!(overview.aggregate.total_messages, 110);
+        assert_eq!(overview.aggregate.total_pipes, 10);
+        assert_eq!(overview.aggregate.total_pipe_bytes, 28160);
+        assert!(overview.aggregate.avg_session_duration_secs >= 0.0);
+        assert!((overview.aggregate.avg_messages_per_session - 11.0).abs() < 0.01);
+        assert!((overview.aggregate.avg_pipes_per_session - 1.0).abs() < 0.01);
+
+        let _ = std::fs::remove_file(&path);
+        let _ = std::fs::remove_file(&overview_path);
+    }
+
+    #[test]
+    fn test_persistence_across_instances() {
+        let path = tmp_path("persistence.json");
+        let overview_path = tmp_path("persistence_overview.json");
+
+        {
+            let metrics = ServerMetrics::load(&path);
+            let mut s1 = metrics.start_session(1000, "inst1-s1".into());
+            s1.record_message(Duration::from_millis(10), true);
+            s1.record_pipe(100);
+            s1.finish("done".into());
+
+            let mut s2 = metrics.start_session(1001, "inst1-s2".into());
+            s2.record_message(Duration::from_millis(20), true);
+            s2.finish("done".into());
+
+            metrics.save(&path);
+            metrics.build_overview(&overview_path);
+        }
+
+        {
+            let metrics = ServerMetrics::load(&path);
+            let snap = metrics.snapshot();
+            assert_eq!(snap.sessions.len(), 2);
+            assert_eq!(snap.total_connections, 2);
+
+            let mut s3 = metrics.start_session(1002, "inst2-s1".into());
+            s3.record_message(Duration::from_millis(5), true);
+            s3.record_pipe(200);
+            s3.record_pipe(300);
+            s3.finish("done".into());
+
+            metrics.save(&path);
+            metrics.build_overview(&overview_path);
+        }
+
+        let metrics = ServerMetrics::load(&path);
+        let snap = metrics.snapshot();
+        assert_eq!(snap.sessions.len(), 3);
+        assert_eq!(snap.total_connections, 3);
+        assert_eq!(snap.total_messages, 3);
+        assert_eq!(snap.total_messages_ok, 3);
+        assert_eq!(snap.total_pipes, 3);
+        assert_eq!(snap.total_pipe_bytes, 600);
+
+        let overview_json = std::fs::read_to_string(&overview_path).unwrap();
+        let overview: Overview = serde_json::from_str(&overview_json).unwrap();
+        assert_eq!(overview.total_sessions, 3);
+        assert_eq!(overview.sessions[0].description, "inst1-s1");
+        assert_eq!(overview.sessions[1].description, "inst1-s2");
+        assert_eq!(overview.sessions[2].description, "inst2-s1");
+
+        let _ = std::fs::remove_file(&path);
+        let _ = std::fs::remove_file(&overview_path);
+    }
+
+    #[test]
+    fn test_accept_errors_and_versions() {
+        let path = tmp_path("accept_errors.json");
+        let overview_path = tmp_path("accept_errors_overview.json");
+
+        let metrics = ServerMetrics::load(&path);
+
+        // Simulate 5 accept errors
+        for _ in 0..5 {
+            metrics.record_accept_error();
+        }
+
+        // Simulate connection versions
+        metrics.record_connection_version("2.0");
+        metrics.record_connection_version("2.0");
+        metrics.record_connection_version("1.0");
+
+        // A normal session with pipe denials and send errors
+        let mut s1 = metrics.start_session(1000, "normal".into());
+        s1.record_message(Duration::from_millis(1), true);
+        s1.record_pipe_denial();
+        s1.record_send_error();
+        s1.record_send_error();
+        s1.finish("done".into());
+
+        metrics.save(&path);
+        let metrics2 = ServerMetrics::load(&path);
+        let snap = metrics2.snapshot();
+        assert_eq!(snap.total_accept_errors, 5);
+        assert_eq!(snap.connection_versions["2.0"], 2);
+        assert_eq!(snap.connection_versions["1.0"], 1);
+        assert_eq!(snap.total_pipe_denials, 1);
+        assert_eq!(snap.total_send_errors, 2);
+        assert_eq!(snap.sessions.len(), 1);
+        assert_eq!(snap.sessions[0].pipe_denials, 1);
+        assert_eq!(snap.sessions[0].send_errors, 2);
+
+        metrics2.build_overview(&overview_path);
+        let overview_json = std::fs::read_to_string(&overview_path).unwrap();
+        let overview: Overview = serde_json::from_str(&overview_json).unwrap();
+        assert_eq!(overview.aggregate.total_accept_errors, 5);
+        assert_eq!(overview.aggregate.total_pipe_denials, 1);
+        assert_eq!(overview.aggregate.total_send_errors, 2);
+        assert_eq!(overview.connection_versions["2.0"], 2);
+        assert_eq!(overview.connection_versions["1.0"], 1);
+
+        let _ = std::fs::remove_file(&path);
+        let _ = std::fs::remove_file(&overview_path);
+    }
+}

host/src/connection.rs

@@ -3,7 +3,6 @@ use mtp_codec::{CommunicationType, DataType, DataValue};
 use mtp_codec::{CommunicationValue, Version, registry::VersionedCodec};
 use mtp_common::CommunicationError;
 use std::net::SocketAddr;
-#[cfg(feature = "pipes")]
 use std::sync::Arc;
 #[cfg(feature = "pipes")]
 use tokio::sync::{Mutex, mpsc};
@@ -12,7 +11,6 @@ use tokio::sync::{Mutex, mpsc};
 use crate::error::random_client_id;
 #[cfg(feature = "pipes")]
 use crate::pipe::{PipeDispatcher, PipeReceiver, PipeRequest, PipeSender, run_dispatcher};
-#[cfg(feature = "pipes")]
 use mtp_transport::Policy;
 
 mod connection_capability {
@@ -161,6 +159,52 @@ where
             client_public_key: None,
         }
     }
+
+    /// Construct an MTP connection with an explicit policy for pipe dispatch.
+    pub fn from_transport_parts_with_policy(
+        version: Version,
+        codec: VersionedCodec,
+        sender: S,
+        receiver: R,
+        path: String,
+        description: Option<String>,
+        remote_addr: Option<SocketAddr>,
+        policy: Arc<Policy>,
+    ) -> Self {
+        let (app_tx, app_rx) = mpsc::channel(policy.receiver_queue_capacity);
+        let (pipe_req_tx, pipe_req_rx) = mpsc::channel(policy.receiver_queue_capacity);
+        let dispatcher = Arc::new(PipeDispatcher {
+            pending_creations: Mutex::new(std::collections::HashMap::new()),
+            pending_pipes: Mutex::new(std::collections::HashMap::new()),
+            policy,
+        });
+        let task = tokio::spawn(run_dispatcher(
+            receiver.clone(),
+            sender.clone(),
+            app_tx,
+            pipe_req_tx,
+            dispatcher.clone(),
+        ));
+        Self {
+            version,
+            codec,
+            sender,
+            receiver,
+            path,
+            remote_addr,
+            app_rx: Mutex::new(app_rx),
+            pipe_req_rx: Mutex::new(pipe_req_rx),
+            pipe_dispatcher: dispatcher,
+            description,
+            _dispatcher_task: task,
+            #[cfg(feature = "crypto")]
+            auth_state: crate::error::AuthState::Unauthenticated,
+            #[cfg(feature = "crypto")]
+            client_id: random_client_id(),
+            #[cfg(feature = "crypto")]
+            client_public_key: None,
+        }
+    }
 }
 
 #[cfg(not(feature = "pipes"))]
@@ -211,6 +255,35 @@ impl<S, R, P> MTPConnection<S, R, P> {
             client_public_key: None,
         }
     }
+
+    pub fn from_transport_parts_with_policy(
+        version: Version,
+        codec: VersionedCodec,
+        sender: S,
+        receiver: R,
+        path: String,
+        description: Option<String>,
+        remote_addr: Option<SocketAddr>,
+        _policy: Arc<Policy>,
+    ) -> Self {
+        Self {
+            version,
+            codec,
+            sender,
+            receiver,
+            path,
+            remote_addr,
+            description,
+            _pipe_stream: std::marker::PhantomData,
+            _dispatcher_task: tokio::spawn(async {}),
+            #[cfg(feature = "crypto")]
+            auth_state: crate::error::AuthState::Unauthenticated,
+            #[cfg(feature = "crypto")]
+            client_id: random_client_id(),
+            #[cfg(feature = "crypto")]
+            client_public_key: None,
+        }
+    }
 }
 
 #[cfg(not(feature = "pipes"))]

host/src/engine.rs

@@ -0,0 +1,825 @@
+//! Transport-independent MTP handshake engine.
+//!
+//! This module contains the shared state machine used by both native `MTPHost`
+//! and the web server's `MTPWebServer` to perform the MTP opening handshake,
+//! version negotiation, authentication, and guest assignment.
+
+use crate::config::HostConfig;
+use crate::error::AcceptError;
+use mtp_codec::{
+    CommunicationType, CommunicationValue, DataType, DataValue, Version,
+    registry::{Registry, VersionedCodec},
+};
+use mtp_common::{CommunicationError, RejectionReason};
+use std::sync::Arc;
+
+/// Trait for sending handshake messages during the opening exchange.
+///
+/// Implemented by both the concrete `Sender` and `GenericSender<C>`.
+pub trait HandshakeSender: Send + Sync {
+    fn send(
+        &self,
+        msg: &CommunicationValue,
+    ) -> impl std::future::Future<Output = Result<(), CommunicationError>> + Send;
+    fn finish_stream(
+        &self,
+    ) -> impl std::future::Future<Output = Result<(), CommunicationError>> + Send;
+    fn close(&self);
+}
+
+/// Trait for receiving handshake messages during the opening exchange.
+///
+/// Implemented by both the concrete `Receiver` and `GenericReceiver<C>`.
+pub trait HandshakeReceiver: Send + Sync {
+    fn receive(
+        &self,
+    ) -> impl std::future::Future<Output = Result<CommunicationValue, CommunicationError>>
+           + Send;
+}
+
+/// The result of a successful handshake, containing everything needed to
+/// construct the final `MTPConnection`.
+#[derive(Debug)]
+pub struct HandshakeResult {
+    pub negotiated_version: Version,
+    pub codec: VersionedCodec,
+    pub description: Option<String>,
+    #[cfg(feature = "crypto")]
+    pub auth_state: crate::error::AuthState,
+    #[cfg(feature = "crypto")]
+    pub client_id: u64,
+    #[cfg(feature = "crypto")]
+    pub client_public_key: Option<mtp_crypto::PublicKeyBundle>,
+}
+
+/// Transport-independent handshake state machine.
+///
+/// Both `MTPHost` and `MTPWebServer` create a `HandshakeEngine` with the
+/// shared `HostConfig` and delegate the full opening handshake to it.
+pub struct HandshakeEngine {
+    registry: Registry,
+    #[cfg(feature = "crypto")]
+    config: Arc<HostConfig>,
+}
+
+impl HandshakeEngine {
+    #[cfg(feature = "crypto")]
+    pub fn new(registry: Registry, config: Arc<HostConfig>) -> Self {
+        Self { registry, config }
+    }
+
+    #[cfg(not(feature = "crypto"))]
+    pub fn new(registry: Registry, _config: Arc<HostConfig>) -> Self {
+        Self { registry }
+    }
+
+    /// Run the complete opening handshake with the given transport pair.
+    ///
+    /// This handles:
+    /// - Opening-frame timeout (when crypto is enabled)
+    /// - Opening-type classification (Identification, Register, or other)
+    /// - Version negotiation
+    /// - Authentication-policy selection (Unauthenticated, AllowAuthentication, ForceAuthentication)
+    /// - Guest allocation and collision avoidance
+    /// - Full challenge/response authentication when required
+    /// - PQ preflight checks and dual-signature verification
+    /// - Rejection response construction on failure
+    pub async fn accept<S: HandshakeSender, R: HandshakeReceiver>(
+        &self,
+        sender: &S,
+        receiver: &R,
+    ) -> Result<HandshakeResult, AcceptError> {
+        #[cfg(feature = "crypto")]
+        {
+            let timeout = self.config.auth_timeout;
+            tokio::time::timeout(timeout, self.accept_inner(sender, receiver))
+                .await
+                .unwrap_or(Err(AcceptError::AuthenticationTimedOut))
+        }
+        #[cfg(not(feature = "crypto"))]
+        self.accept_inner(sender, receiver).await
+    }
+
+    async fn accept_inner<S: HandshakeSender, R: HandshakeReceiver>(
+        &self,
+        sender: &S,
+        receiver: &R,
+    ) -> Result<HandshakeResult, AcceptError> {
+        let first_msg = receiver.receive().await.map_err(AcceptError::Receive)?;
+
+        let version_str = match first_msg.get_data(DataType::Version) {
+            DataValue::Str(s) => s.clone(),
+            _ => {
+                send_rejection_generic(
+                    sender,
+                    RejectionReason::AuthenticationFailed {
+                        detail: "opening message omitted a valid protocol version".into(),
+                    },
+                )
+                .await;
+                sender.close();
+                return Err(AcceptError::MissingVersion);
+            }
+        };
+        let client_version = match Version::parse(&version_str) {
+            Some(v) => v,
+            _ => {
+                send_rejection_generic(
+                    sender,
+                    RejectionReason::AuthenticationFailed {
+                        detail: "opening message omitted a valid protocol version".into(),
+                    },
+                )
+                .await;
+                sender.close();
+                return Err(AcceptError::MissingVersion);
+            }
+        };
+
+        let negotiated = match self.registry.negotiate(std::slice::from_ref(&client_version)) {
+            Some(v) => v,
+            None => {
+                send_rejection_generic(
+                    sender,
+                    RejectionReason::BadVersion {
+                        supported_versions: self
+                            .registry
+                            .versions()
+                            .map(|v| v.to_string())
+                            .collect(),
+                    },
+                )
+                .await;
+                sender.close();
+                return Err(AcceptError::UnsupportedVersion(client_version));
+            }
+        };
+
+        let codec = VersionedCodec::for_version(self.registry.clone(), negotiated.clone())
+            .ok_or_else(|| AcceptError::UnsupportedVersion(negotiated.clone()))?;
+
+        let description = match first_msg.get_data(DataType::Description) {
+            DataValue::Str(s) => Some(s.clone()),
+            _ => None,
+        };
+
+        #[cfg(feature = "crypto")]
+        {
+            match self.config.authentication_policy {
+                crate::config::AuthenticationPolicy::ForceAuthentication => {
+                    self.force_auth_handshake(
+                        sender,
+                        receiver,
+                        first_msg,
+                        negotiated,
+                        codec,
+                        description,
+                        &version_str,
+                        client_version,
+                    )
+                    .await
+                }
+                crate::config::AuthenticationPolicy::AllowAuthentication => {
+                    self.allow_auth_handshake(
+                        sender,
+                        receiver,
+                        first_msg,
+                        negotiated,
+                        codec,
+                        description,
+                        &version_str,
+                        client_version,
+                    )
+                    .await
+                }
+                crate::config::AuthenticationPolicy::Unauthenticated => {
+                    self.unauthenticated_handshake(
+                        sender,
+                        first_msg,
+                        negotiated,
+                        codec,
+                        description,
+                    )
+                    .await
+                }
+            }
+        }
+
+        #[cfg(not(feature = "crypto"))]
+        {
+            let _ = sender;
+            let _ = receiver;
+            let _ = first_msg;
+            Ok(HandshakeResult {
+                negotiated_version: negotiated,
+                codec,
+                description,
+            })
+        }
+    }
+
+    #[cfg(feature = "crypto")]
+    async fn unauthenticated_handshake<S: HandshakeSender>(
+        &self,
+        sender: &S,
+        first_msg: CommunicationValue,
+        negotiated: Version,
+        codec: VersionedCodec,
+        description: Option<String>,
+    ) -> Result<HandshakeResult, AcceptError> {
+        let tm = mtp_codec::TypeMap::latest();
+
+        // Reject Register frames on unauthenticated hosts
+        if Some(first_msg.get_type()) == CommunicationType::Register.try_to_id(&tm) {
+            send_rejection_generic(
+                sender,
+                RejectionReason::AuthenticationFailed {
+                    detail: "authentication not allowed on this host".into(),
+                },
+            )
+            .await;
+            sender.close();
+            return Err(AcceptError::AuthenticationFailed(
+                "authentication not allowed on this host".into(),
+            ));
+        }
+
+        let guest_id = self.assign_guest_id().await?;
+        send_accepted_generic(sender, &negotiated, Some(guest_id))
+            .await
+            .map_err(AcceptError::Send)?;
+
+        Ok(HandshakeResult {
+            negotiated_version: negotiated,
+            codec,
+            description,
+            auth_state: crate::error::AuthState::Unauthenticated,
+            client_id: guest_id,
+            client_public_key: None,
+        })
+    }
+
+    #[cfg(feature = "crypto")]
+    #[allow(clippy::too_many_arguments)]
+    async fn allow_auth_handshake<S: HandshakeSender, R: HandshakeReceiver>(
+        &self,
+        sender: &S,
+        receiver: &R,
+        first_msg: CommunicationValue,
+        negotiated: Version,
+        codec: VersionedCodec,
+        description: Option<String>,
+        version_str: &str,
+        client_version: Version,
+    ) -> Result<HandshakeResult, AcceptError> {
+        let tm = mtp_codec::TypeMap::latest();
+
+        // Register frames always go through full authentication
+        if Some(first_msg.get_type()) == CommunicationType::Register.try_to_id(&tm) {
+            let bundle = extract_register_bundle(&first_msg)?;
+            let pk_bytes = bundle.as_bytes();
+            return self
+                .complete_auth_handshake(
+                    sender,
+                    receiver,
+                    Flow::Register { bundle, pk_bytes },
+                    CommunicationType::RegisterResponse,
+                    &negotiated,
+                    &codec,
+                    description,
+                    version_str,
+                    client_version,
+                )
+                .await;
+        }
+
+        // Identification: try lookup, fall back to guest
+        if Some(first_msg.get_type()) == CommunicationType::Identification.try_to_id(&tm) {
+            let cid = match first_msg.get_data(DataType::Id) {
+                DataValue::UnsignedNumber(n) => *n as u64,
+                _ => 0,
+            };
+
+            if cid > 0 {
+                if let Some(bundle) =
+                    (self.config.get_existing_client)(cid, description.clone()).await
+                {
+                    return self
+                        .complete_auth_handshake(
+                            sender,
+                            receiver,
+                            Flow::Login { id: cid, bundle },
+                            CommunicationType::IdentificationResponse,
+                            &negotiated,
+                            &codec,
+                            description,
+                            version_str,
+                            client_version,
+                        )
+                        .await;
+                }
+            }
+
+            // Unknown or zero ID: fall back to guest
+            let guest_id = self.assign_guest_id().await?;
+            send_accepted_generic(sender, &negotiated, Some(guest_id))
+                .await
+                .map_err(AcceptError::Send)?;
+            return Ok(HandshakeResult {
+                negotiated_version: negotiated,
+                codec,
+                description,
+                auth_state: crate::error::AuthState::Unauthenticated,
+                client_id: guest_id,
+                client_public_key: None,
+            });
+        }
+
+        sender.close();
+        Err(AcceptError::AuthenticationFailed(
+            "unexpected message type".into(),
+        ))
+    }
+
+    #[cfg(feature = "crypto")]
+    #[allow(clippy::too_many_arguments)]
+    async fn force_auth_handshake<S: HandshakeSender, R: HandshakeReceiver>(
+        &self,
+        sender: &S,
+        receiver: &R,
+        first_msg: CommunicationValue,
+        negotiated: Version,
+        codec: VersionedCodec,
+        description: Option<String>,
+        version_str: &str,
+        client_version: Version,
+    ) -> Result<HandshakeResult, AcceptError> {
+        let tm = mtp_codec::TypeMap::latest();
+
+        let (flow, response_type) = if Some(first_msg.get_type())
+            == CommunicationType::Identification.try_to_id(&tm)
+        {
+            let cid = match first_msg.get_data(DataType::Id) {
+                DataValue::UnsignedNumber(n) => *n as u64,
+                _ => {
+                    sender.close();
+                    return Err(AcceptError::AuthenticationFailed(
+                        "missing client id".into(),
+                    ));
+                }
+            };
+            let bundle = match (self.config.get_existing_client)(cid, description.clone()).await {
+                Some(b) => b,
+                None => {
+                    let rejection =
+                        CommunicationValue::new(CommunicationType::IdentificationResponse)
+                            .add_typed_default(DataType::Connected, DataValue::BoolFalse)
+                            .add_typed_default(
+                                DataType::ErrorMessage,
+                                DataValue::Str("unknown client id".into()),
+                            );
+                    let _ = sender.send(&rejection).await;
+                    sender.close();
+                    return Err(AcceptError::AuthenticationFailed(
+                        "unknown client id".into(),
+                    ));
+                }
+            };
+            (
+                Flow::Login { id: cid, bundle },
+                CommunicationType::IdentificationResponse,
+            )
+        } else if Some(first_msg.get_type()) == CommunicationType::Register.try_to_id(&tm) {
+            let bundle = extract_register_bundle(&first_msg)?;
+            let pk_bytes = bundle.as_bytes();
+            (
+                Flow::Register { bundle, pk_bytes },
+                CommunicationType::RegisterResponse,
+            )
+        } else {
+            sender.close();
+            return Err(AcceptError::AuthenticationFailed(
+                "unexpected authentication message".into(),
+            ));
+        };
+
+        self.complete_auth_handshake(
+            sender,
+            receiver,
+            flow,
+            response_type,
+            &negotiated,
+            &codec,
+            description,
+            version_str,
+            client_version,
+        )
+        .await
+    }
+
+    #[cfg(feature = "crypto")]
+    #[allow(clippy::too_many_arguments)]
+    async fn complete_auth_handshake<S: HandshakeSender, R: HandshakeReceiver>(
+        &self,
+        sender: &S,
+        receiver: &R,
+        flow: Flow,
+        response_type: CommunicationType,
+        negotiated: &Version,
+        codec: &VersionedCodec,
+        description: Option<String>,
+        version_str: &str,
+        _client_version: Version,
+    ) -> Result<HandshakeResult, AcceptError> {
+        use mtp_crypto::{Ed25519Signer, MlDsaSigner, SignatureScheme, auth, verify_ed25519};
+
+        let tm = mtp_codec::TypeMap::latest();
+
+        // PQ preflight: host requiring PQ must have a PQ key
+        let pq_enabled = !self
+            .config
+            .host_keyring
+            .sig_pq_secret_key
+            .as_bytes()
+            .is_empty();
+        if self.config.require_pq
+            && (!pq_enabled
+                || self
+                    .config
+                    .host_keyring
+                    .sig_pq_public_key
+                    .as_bytes()
+                    .is_empty())
+        {
+            send_rejection_generic(
+                sender,
+                RejectionReason::AuthenticationFailed {
+                    detail: "host requires PQ authentication but has no PQ signing key".into(),
+                },
+            )
+            .await;
+            sender.close();
+            return Err(AcceptError::AuthenticationFailed(
+                "PQ authentication is required but the host PQ key is absent".into(),
+            ));
+        }
+
+        // Initialize host signers
+        let host_pq_signer = if pq_enabled {
+            Some(Arc::new(
+                MlDsaSigner::new(
+                    &self.config.host_keyring.sig_pq_secret_key,
+                    &self.config.host_keyring.sig_pq_public_key,
+                )
+                .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))?,
+            ))
+        } else {
+            None
+        };
+
+        let host_sign = |payload: Vec<u8>| async {
+            let signer = Ed25519Signer::new(&self.config.host_keyring.sig_cl_secret_key)
+                .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))?;
+            if let Some(pq_signer) = host_pq_signer.as_ref() {
+                mtp_crypto::sign_parallel::sign_dual_parallel_shared_pq(
+                    signer,
+                    Arc::clone(pq_signer),
+                    payload,
+                )
+                .await
+                .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))
+            } else {
+                let sig = signer
+                    .sign(&payload)
+                    .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))?;
+                Ok((sig, Vec::new()))
+            }
+        };
+
+        // Sign and send challenge
+        let challenge_id = match &flow {
+            Flow::Login { id, .. } => *id,
+            Flow::Register { .. } => 0,
+        };
+
+        let server_challenge: u128 = rand::random();
+        let (chal_sig, chal_pq_sig) =
+            host_sign(auth::challenge_payload(challenge_id, server_challenge)).await?;
+
+        let mut challenge_msg = CommunicationValue::new(CommunicationType::Challenge)
+            .add_typed_default(
+                DataType::ServerNonce,
+                DataValue::UnsignedNumber(server_challenge),
+            )
+            .add_typed_default(DataType::Signature, DataValue::Bytes(chal_sig));
+        challenge_msg = challenge_msg.add_typed_default(
+            DataType::RequirePq,
+            if self.config.require_pq {
+                DataValue::BoolTrue
+            } else {
+                DataValue::BoolFalse
+            },
+        );
+        if pq_enabled {
+            challenge_msg = challenge_msg
+                .add_typed_default(DataType::PqSignature, DataValue::Bytes(chal_pq_sig));
+        }
+        if let Err(e) = sender.send(&challenge_msg).await {
+            sender.close();
+            return Err(AcceptError::Send(e));
+        }
+
+        // Receive and verify client proof
+        let proof = receiver.receive().await.map_err(|e| {
+            sender.close();
+            AcceptError::Receive(e)
+        })?;
+        if Some(proof.get_type()) != CommunicationType::ChallengeResponse.try_to_id(&tm) {
+            sender.close();
+            return Err(AcceptError::AuthenticationFailed(
+                "missing challenge response".into(),
+            ));
+        }
+        let client_nonce = match proof.get_data(DataType::ClientNonce) {
+            DataValue::UnsignedNumber(n) => *n,
+            _ => {
+                sender.close();
+                return Err(AcceptError::AuthenticationFailed(
+                    "missing client nonce".into(),
+                ));
+            }
+        };
+        let sig_bytes = match proof.get_data(DataType::Signature) {
+            DataValue::Bytes(b) => b.clone(),
+            _ => {
+                sender.close();
+                return Err(AcceptError::AuthenticationFailed(
+                    "missing challenge signature".into(),
+                ));
+            }
+        };
+        let pq_sig_bytes: Vec<u8> = match proof.get_data(DataType::PqSignature) {
+            DataValue::Bytes(b) => b.clone(),
+            _ => vec![],
+        };
+
+        let (proof_payload, bundle) = match &flow {
+            Flow::Login { id, bundle } => (
+                auth::login_proof_payload(version_str, *id, server_challenge, client_nonce),
+                bundle,
+            ),
+            Flow::Register {
+                bundle, pk_bytes, ..
+            } => (
+                auth::register_proof_payload(version_str, pk_bytes, server_challenge, client_nonce),
+                bundle,
+            ),
+        };
+
+        let has_client_pq_key = !bundle.sig_pq_public_key.as_bytes().is_empty();
+        let proof_ok = if pq_sig_bytes.is_empty() {
+            !self.config.require_pq
+                && verify_ed25519(&bundle.sig_cl_public_key, &proof_payload, &sig_bytes).is_ok()
+        } else if has_client_pq_key {
+            mtp_crypto::sign_parallel::verify_dual_parallel(
+                bundle.sig_cl_public_key.clone(),
+                bundle.sig_pq_public_key.clone(),
+                proof_payload,
+                sig_bytes,
+                pq_sig_bytes,
+            )
+            .await
+            .is_ok()
+        } else {
+            false
+        };
+
+        if !proof_ok {
+            send_rejection_generic(
+                sender,
+                RejectionReason::AuthenticationFailed {
+                    detail: "client proof signature invalid".into(),
+                },
+            )
+            .await;
+            sender.close();
+            return Err(AcceptError::AuthenticationFailed(
+                "client proof signature invalid".into(),
+            ));
+        }
+
+        // Register or login
+        let (assigned_id, client_bundle) = match flow {
+            Flow::Login { id, bundle } => (id, bundle),
+            Flow::Register { bundle, .. } => {
+                let new_id =
+                    (self.config.complete_register)(bundle.clone(), description.clone()).await;
+                (new_id, bundle)
+            }
+        };
+
+        // Sign and send final response
+        let (host_sig, host_pq_sig) = host_sign(auth::host_final_payload(
+            assigned_id,
+            client_nonce,
+            server_challenge,
+        ))
+        .await?;
+
+        let mut response = CommunicationValue::new(response_type)
+            .add_typed_default(DataType::Connected, DataValue::BoolTrue)
+            .add_typed_default(DataType::Id, DataValue::UnsignedNumber(assigned_id as u128))
+            .add_typed_default(
+                DataType::ClientNonce,
+                DataValue::UnsignedNumber(client_nonce),
+            )
+            .add_typed_default(DataType::Signature, DataValue::Bytes(host_sig));
+        response = response
+            .add_typed_default(DataType::Version, DataValue::Str(negotiated.to_string()));
+        if pq_enabled {
+            response =
+                response.add_typed_default(DataType::PqSignature, DataValue::Bytes(host_pq_sig));
+        }
+
+        if let Err(e) = sender.send(&response).await {
+            sender.close();
+            return Err(AcceptError::Send(e));
+        }
+        if let Err(e) = sender.finish_stream().await {
+            sender.close();
+            return Err(AcceptError::Send(e));
+        }
+
+        Ok(HandshakeResult {
+            negotiated_version: negotiated.clone(),
+            codec: codec.clone(),
+            description,
+            auth_state: crate::error::AuthState::Authenticated,
+            client_id: assigned_id,
+            client_public_key: Some(client_bundle),
+        })
+    }
+}
+
+#[cfg(feature = "crypto")]
+enum Flow {
+    Login {
+        id: u64,
+        bundle: mtp_crypto::PublicKeyBundle,
+    },
+    Register {
+        bundle: mtp_crypto::PublicKeyBundle,
+        pk_bytes: Vec<u8>,
+    },
+}
+
+// ---------------------------------------------------------------------------
+// Guest ID allocation
+// ---------------------------------------------------------------------------
+
+#[cfg(feature = "crypto")]
+impl HandshakeEngine {
+    const GUEST_ID_MAX_RETRIES: u32 = 100;
+
+    async fn assign_guest_id(&self) -> Result<u64, AcceptError> {
+        if let Some(ref generator) = self.config.guest_id_generator {
+            let id = generator().await.ok_or_else(|| {
+                AcceptError::AuthenticationFailed(
+                    "guest id generator rejected the connection".into(),
+                )
+            })?;
+            if id > mtp_codec::MAX_WIRE_ID {
+                return Err(AcceptError::AuthenticationFailed(
+                    "guest id exceeds wire limit".into(),
+                ));
+            }
+            if (self.config.get_existing_client)(id, None).await.is_none() {
+                return Ok(id);
+            }
+        }
+        self.random_guest_id().await
+    }
+
+    async fn random_guest_id(&self) -> Result<u64, AcceptError> {
+        for _ in 0..Self::GUEST_ID_MAX_RETRIES {
+            let id = rand::random::<u64>() & mtp_codec::MAX_WIRE_ID;
+            if (self.config.get_existing_client)(id, None).await.is_none() {
+                return Ok(id);
+            }
+        }
+        Err(AcceptError::AuthenticationFailed(
+            "failed to allocate a unique guest id after retries".into(),
+        ))
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+#[cfg(feature = "crypto")]
+fn extract_register_bundle(
+    msg: &CommunicationValue,
+) -> Result<mtp_crypto::PublicKeyBundle, AcceptError> {
+    match msg.get_data(DataType::PublicKeys) {
+        DataValue::Bytes(b) => mtp_crypto::PublicKeyBundle::from_bytes(b).map_err(|_| {
+            AcceptError::AuthenticationFailed("invalid public key bundle".into())
+        }),
+        _ => Err(AcceptError::AuthenticationFailed(
+            "missing public keys".into(),
+        )),
+    }
+}
+
+async fn send_rejection_generic<S: HandshakeSender>(
+    sender: &S,
+    reason: RejectionReason,
+) {
+    let response = match &reason {
+        RejectionReason::BadVersion { supported_versions } => {
+            CommunicationValue::new(CommunicationType::ErrorBadVersion)
+                .add_typed_default(
+                    DataType::Version,
+                    DataValue::Str(supported_versions.join(",")),
+                )
+                .add_typed_default(DataType::ErrorMessage, DataValue::Str(reason.to_string()))
+        }
+        _ => CommunicationValue::new(CommunicationType::IdentificationResponse)
+            .add_typed_default(DataType::Connected, DataValue::BoolFalse)
+            .add_typed_default(DataType::ErrorMessage, DataValue::Str(reason.to_string())),
+    };
+    let _ = sender.send(&response).await;
+}
+
+#[cfg(feature = "crypto")]
+async fn send_accepted_generic<S: HandshakeSender>(
+    sender: &S,
+    version: &Version,
+    assigned_id: Option<u64>,
+) -> Result<(), CommunicationError> {
+    let mut response = CommunicationValue::new(CommunicationType::IdentificationResponse)
+        .add_typed_default(DataType::Connected, DataValue::BoolTrue)
+        .add_typed_default(DataType::Version, DataValue::Str(version.to_string()));
+    if let Some(id) = assigned_id {
+        response = response.add_typed_default(DataType::Id, DataValue::UnsignedNumber(id as u128));
+    }
+    sender.send(&response).await?;
+    sender.finish_stream().await
+}
+
+// ---------------------------------------------------------------------------
+// Trait implementations for concrete transport types
+// ---------------------------------------------------------------------------
+
+impl HandshakeSender for mtp_transport::Sender {
+    fn send(
+        &self,
+        msg: &CommunicationValue,
+    ) -> impl std::future::Future<Output = Result<(), CommunicationError>> + Send {
+        mtp_transport::Sender::send(self, msg)
+    }
+    fn finish_stream(
+        &self,
+    ) -> impl std::future::Future<Output = Result<(), CommunicationError>> + Send {
+        mtp_transport::Sender::finish_stream(self)
+    }
+    fn close(&self) {
+        let sender = self.clone();
+        tokio::spawn(async move { sender.close().await });
+    }
+}
+
+impl HandshakeReceiver for mtp_transport::Receiver {
+    fn receive(
+        &self,
+    ) -> impl std::future::Future<Output = Result<CommunicationValue, CommunicationError>> + Send
+    {
+        mtp_transport::Receiver::receive(self)
+    }
+}
+
+impl<C: mtp_transport::TransportConnection> HandshakeSender for mtp_transport::GenericSender<C> {
+    fn send(
+        &self,
+        msg: &CommunicationValue,
+    ) -> impl std::future::Future<Output = Result<(), CommunicationError>> + Send {
+        mtp_transport::GenericSender::send(self, msg)
+    }
+    fn finish_stream(
+        &self,
+    ) -> impl std::future::Future<Output = Result<(), CommunicationError>> + Send {
+        mtp_transport::GenericSender::finish_stream(self)
+    }
+    fn close(&self) {
+        mtp_transport::GenericSender::close(self);
+    }
+}
+
+impl<C: mtp_transport::TransportConnection> HandshakeReceiver for mtp_transport::GenericReceiver<C> {
+    fn receive(
+        &self,
+    ) -> impl std::future::Future<Output = Result<CommunicationValue, CommunicationError>> + Send
+    {
+        mtp_transport::GenericReceiver::receive(self)
+    }
+}

host/src/error.rs

@@ -1,45 +1,16 @@
-use mtp_codec::{CommunicationType, CommunicationValue, DataType, DataValue, Version};
+use mtp_codec::Version;
-use mtp_common::{CommunicationError, RejectionReason};
+use mtp_common::CommunicationError;
-use mtp_transport::Sender;
 use std::{error::Error, fmt};
 
+#[cfg(test)]
+use mtp_codec::{CommunicationValue, DataType, DataValue};
+
 #[cfg(feature = "crypto")]
 pub(crate) fn random_client_id() -> u64 {
     rand::random::<u64>() & mtp_codec::MAX_WIRE_ID
 }
 
-pub(crate) async fn send_rejection(sender: &Sender, reason: RejectionReason) {
+#[cfg(test)]
-    let response = match &reason {
-        RejectionReason::BadVersion { supported_versions } => {
-            CommunicationValue::new(CommunicationType::ErrorBadVersion)
-                .add_typed_default(
-                    DataType::Version,
-                    DataValue::Str(supported_versions.join(",")),
-                )
-                .add_typed_default(DataType::ErrorMessage, DataValue::Str(reason.to_string()))
-        }
-        _ => CommunicationValue::new(CommunicationType::IdentificationResponse)
-            .add_typed_default(DataType::Connected, DataValue::BoolFalse)
-            .add_typed_default(DataType::ErrorMessage, DataValue::Str(reason.to_string())),
-    };
-    let _ = sender.send(&response).await;
-}
-
-pub(crate) async fn send_accepted(
-    sender: &Sender,
-    version: &Version,
-    assigned_id: Option<u64>,
-) -> Result<(), CommunicationError> {
-    let mut response = CommunicationValue::new(CommunicationType::IdentificationResponse)
-        .add_typed_default(DataType::Connected, DataValue::BoolTrue)
-        .add_typed_default(DataType::Version, DataValue::Str(version.to_string()));
-    if let Some(id) = assigned_id {
-        response = response.add_typed_default(DataType::Id, DataValue::UnsignedNumber(id as u128));
-    }
-    sender.send(&response).await?;
-    sender.finish_stream().await
-}
-
 pub(crate) fn extract_version(msg: &CommunicationValue) -> Option<Version> {
     let value = msg.get_data(DataType::Version);
     match value {

host/src/handshake.rs

@@ -1,23 +1,17 @@
+#[cfg(not(feature = "crypto"))]
+use mtp_codec::{Version, registry::{Registry, VersionedCodec}};
 #[cfg(feature = "crypto")]
-use mtp_codec::{CommunicationType, CommunicationValue};
+use mtp_codec::registry::Registry;
-use mtp_codec::{
-    DataType, DataValue, Version,
-    registry::{Registry, VersionedCodec},
-};
-use mtp_common::RejectionReason;
 use mtp_transport::{Receiver, Sender};
 use std::sync::Arc;
 use std::time::Instant;
 #[cfg(feature = "pipes")]
 use tokio::sync::mpsc;
 
-#[cfg(feature = "crypto")]
-use crate::config::AuthenticationPolicy;
 use crate::config::HostConfig;
 use crate::connection::MTPConnection;
-#[cfg(feature = "crypto")]
+use crate::engine::HandshakeEngine;
-use crate::error::AuthState;
+use crate::error::AcceptError;
-use crate::error::{AcceptError, extract_version, send_accepted, send_rejection};
 #[cfg(feature = "pipes")]
 use crate::pipe::PipeDispatcher;
 #[cfg(feature = "pipes")]
@@ -137,179 +131,104 @@ impl HandshakeContext {
         sender: Sender,
         receiver: Receiver,
     ) -> Result<Option<MTPConnection>, AcceptError> {
+        let engine = HandshakeEngine::new(self.registry.clone(), self.config.clone());
+        let result = engine.accept(&sender, &receiver).await?;
         #[cfg(feature = "crypto")]
         {
-            return tokio::time::timeout(
+            Ok(Some(self.connection_from_handshake_result(
-                self.config.auth_timeout,
+                sender,
-                self.accept_pair(sender, receiver),
+                receiver,
-            )
+                result,
-            .await
+            )))
-            .unwrap_or(Err(AcceptError::AuthenticationTimedOut));
         }
         #[cfg(not(feature = "crypto"))]
-        self.accept_pair(sender, receiver).await
+        {
+            Ok(Some(self.connection_from_parts(
+                sender,
+                receiver,
+                result.negotiated_version,
+                result.codec,
+                result.description,
+            )))
+        }
     }
 
-    async fn accept_pair(
+    #[cfg(feature = "crypto")]
+    pub(crate) fn connection_from_handshake_result(
         &self,
         sender: Sender,
         receiver: Receiver,
-    ) -> Result<Option<MTPConnection>, AcceptError> {
+        result: crate::engine::HandshakeResult,
-        #[cfg(feature = "crypto")]
+    ) -> MTPConnection {
-        match self.config.authentication_policy {
+        let remote_addr = sender.handle().remote_addr();
-            AuthenticationPolicy::ForceAuthentication => {
+        receiver.set_max_message_size(self.config.policy.max_message_size);
-                let timeout = self.config.auth_timeout;
+        #[cfg(feature = "pipes")]
-                match tokio::time::timeout(timeout, self.accept_authenticated(sender, receiver))
-                    .await
         {
-                    Ok(result) => result,
+            if self.config.send_pongs {
-                    Err(_) => Err(AcceptError::AuthenticationTimedOut),
+                receiver.respond_to_pings(sender.clone());
             }
-            }
+
-            AuthenticationPolicy::AllowAuthentication => {
+            let (app_tx, app_rx) = mpsc::channel(self.config.policy.receiver_queue_capacity);
-                return self.accept_allow_auth(sender, receiver).await;
+            let (pipe_req_tx, pipe_req_rx) =
-            }
+                mpsc::channel(self.config.policy.receiver_queue_capacity);
-            AuthenticationPolicy::Unauthenticated => {
+
-                let first_msg = match receiver.receive().await {
+            let dispatcher = Arc::new(PipeDispatcher {
-                    Ok(m) => m,
+                pending_creations: tokio::sync::Mutex::new(std::collections::HashMap::new()),
-                    Err(e) => return Err(AcceptError::Receive(e)),
+                pending_pipes: tokio::sync::Mutex::new(std::collections::HashMap::new()),
-                };
+                policy: Arc::new(self.config.policy),
-                if Some(first_msg.get_type())
+            });
-                    == CommunicationType::Register.try_to_id(&mtp_codec::TypeMap::latest())
+
-                {
+            let dispatcher_clone = dispatcher.clone();
-                    send_rejection(
+            let receiver_clone = receiver.clone();
-                        &sender,
+            let sender_clone = sender.clone();
-                        RejectionReason::AuthenticationFailed {
+            let task = tokio::spawn(run_dispatcher(
-                            detail: "authentication not allowed on this host".into(),
+                receiver_clone,
-                        },
+                sender_clone,
-                    )
+                app_tx,
-                    .await;
+                pipe_req_tx,
-                    sender.close().await;
+                dispatcher_clone,
-                    return Err(AcceptError::AuthenticationFailed(
-                        "authentication not allowed on this host".into(),
             ));
-                }
+
-                let client_version = match extract_version(&first_msg) {
+            MTPConnection {
-                    Some(v) => v,
+                version: result.negotiated_version,
-                    None => {
+                codec: result.codec,
-                        send_rejection(
-                            &sender,
-                            RejectionReason::AuthenticationFailed {
-                                detail: "opening message omitted a valid protocol version".into(),
-                            },
-                        )
-                        .await;
-                        sender.close().await;
-                        return Err(AcceptError::MissingVersion);
-                    }
-                };
-                let negotiated = match self
-                    .registry
-                    .negotiate(std::slice::from_ref(&client_version))
-                {
-                    Some(v) => v,
-                    None => {
-                        send_rejection(
-                            &sender,
-                            RejectionReason::BadVersion {
-                                supported_versions: self
-                                    .registry
-                                    .versions()
-                                    .map(|v| v.to_string())
-                                    .collect(),
-                            },
-                        )
-                        .await;
-                        sender.close().await;
-                        return Err(AcceptError::UnsupportedVersion(client_version));
-                    }
-                };
-                let codec =
-                    match VersionedCodec::for_version(self.registry.clone(), negotiated.clone()) {
-                        Some(codec) => codec,
-                        None => {
-                            return Err(AcceptError::UnsupportedVersion(negotiated));
-                        }
-                    };
-                let description = match first_msg.get_data(DataType::Description) {
-                    DataValue::Str(s) => Some(s.clone()),
-                    _ => None,
-                };
-                let guest_id = self.assign_guest_id().await;
-                send_accepted(&sender, &negotiated, Some(guest_id))
-                    .await
-                    .map_err(AcceptError::Send)?;
-                Ok(Some(self.connection_from_parts(
                 sender,
                 receiver,
-                    negotiated,
+                path: "/".to_string(),
-                    codec,
+                remote_addr,
-                    description,
+                app_rx: tokio::sync::Mutex::new(app_rx),
-                    AuthState::Unauthenticated,
+                pipe_req_rx: tokio::sync::Mutex::new(pipe_req_rx),
-                    guest_id,
+                pipe_dispatcher: dispatcher,
-                    None,
+                description: result.description,
-                )))
+                _dispatcher_task: task,
+                auth_state: result.auth_state,
+                client_id: result.client_id,
+                client_public_key: result.client_public_key,
             }
         }
 
-        #[cfg(not(feature = "crypto"))]
+        #[cfg(not(feature = "pipes"))]
         {
-            let first_msg = match receiver.receive().await {
+            if self.config.send_pongs {
-                Ok(m) => m,
+                receiver.respond_to_pings(sender.clone());
-                Err(e) => return Err(AcceptError::Receive(e)),
-            };
-            let client_version = match extract_version(&first_msg) {
-                Some(v) => v,
-                None => {
-                    send_rejection(
-                        &sender,
-                        RejectionReason::AuthenticationFailed {
-                            detail: "opening message omitted a valid protocol version".into(),
-                        },
-                    )
-                    .await;
-                    sender.close().await;
-                    return Err(AcceptError::MissingVersion);
             }
-            };
+
-            let negotiated = match self
+            let task = tokio::spawn(async {});
-                .registry
+
-                .negotiate(std::slice::from_ref(&client_version))
+            MTPConnection {
-            {
+                version: result.negotiated_version,
-                Some(v) => v,
+                codec: result.codec,
-                None => {
-                    send_rejection(
-                        &sender,
-                        RejectionReason::BadVersion {
-                            supported_versions: vec![mtp_codec::PROTOCOL_VERSION.to_string()],
-                        },
-                    )
-                    .await;
-                    sender.close().await;
-                    return Err(AcceptError::UnsupportedVersion(client_version));
-                }
-            };
-            let codec = match VersionedCodec::for_version(self.registry.clone(), negotiated.clone())
-            {
-                Some(codec) => codec,
-                None => {
-                    return Err(AcceptError::UnsupportedVersion(negotiated));
-                }
-            };
-            let description = match first_msg.get_data(DataType::Description) {
-                DataValue::Str(s) => Some(s.clone()),
-                _ => None,
-            };
-            send_accepted(&sender, &negotiated, None)
-                .await
-                .map_err(AcceptError::Send)?;
-            Ok(Some(self.connection_from_parts(
                 sender,
                 receiver,
-                negotiated,
+                path: "/".to_string(),
-                codec,
+                remote_addr,
-                description,
+                _pipe_stream: std::marker::PhantomData,
-            )))
+                description: result.description,
+                _dispatcher_task: task,
+                auth_state: result.auth_state,
+                client_id: result.client_id,
+                client_public_key: result.client_public_key,
+            }
         }
     }
 
@@ -388,645 +307,4 @@ impl HandshakeContext {
             }
         }
     }
-
-    #[cfg(feature = "crypto")]
-    #[allow(clippy::too_many_arguments)]
-    pub(crate) fn connection_from_parts(
-        &self,
-        sender: Sender,
-        receiver: Receiver,
-        version: Version,
-        codec: VersionedCodec,
-        description: Option<String>,
-        auth_state: AuthState,
-        client_id: u64,
-        client_public_key: Option<mtp_crypto::PublicKeyBundle>,
-    ) -> MTPConnection {
-        let remote_addr = sender.handle().remote_addr();
-        receiver.set_max_message_size(self.config.policy.max_message_size);
-        #[cfg(feature = "pipes")]
-        {
-            if self.config.send_pongs {
-                receiver.respond_to_pings(sender.clone());
-            }
-
-            let (app_tx, app_rx) = mpsc::channel(self.config.policy.receiver_queue_capacity);
-            let (pipe_req_tx, pipe_req_rx) =
-                mpsc::channel(self.config.policy.receiver_queue_capacity);
-
-            let dispatcher = Arc::new(PipeDispatcher {
-                pending_creations: tokio::sync::Mutex::new(std::collections::HashMap::new()),
-                pending_pipes: tokio::sync::Mutex::new(std::collections::HashMap::new()),
-                policy: Arc::new(self.config.policy),
-            });
-
-            let dispatcher_clone = dispatcher.clone();
-            let receiver_clone = receiver.clone();
-            let sender_clone = sender.clone();
-            let task = tokio::spawn(run_dispatcher(
-                receiver_clone,
-                sender_clone,
-                app_tx,
-                pipe_req_tx,
-                dispatcher_clone,
-            ));
-
-            MTPConnection {
-                version,
-                codec,
-                sender,
-                receiver,
-                path: "/".to_string(),
-                remote_addr,
-                app_rx: tokio::sync::Mutex::new(app_rx),
-                pipe_req_rx: tokio::sync::Mutex::new(pipe_req_rx),
-                pipe_dispatcher: dispatcher,
-                description,
-                _dispatcher_task: task,
-                auth_state,
-                client_id,
-                client_public_key,
-            }
-        }
-
-        #[cfg(not(feature = "pipes"))]
-        {
-            if self.config.send_pongs {
-                receiver.respond_to_pings(sender.clone());
-            }
-
-            let task = tokio::spawn(async {});
-
-            MTPConnection {
-                version,
-                codec,
-                sender,
-                receiver,
-                path: "/".to_string(),
-                remote_addr,
-                _pipe_stream: std::marker::PhantomData,
-                description,
-                _dispatcher_task: task,
-                auth_state,
-                client_id,
-                client_public_key,
-            }
-        }
-    }
-}
-
-#[cfg(feature = "crypto")]
-enum Flow {
-    Login {
-        id: u64,
-        bundle: mtp_crypto::PublicKeyBundle,
-    },
-    Register {
-        bundle: mtp_crypto::PublicKeyBundle,
-        pk_bytes: Vec<u8>,
-    },
-}
-
-#[cfg(feature = "crypto")]
-impl HandshakeContext {
-    const GUEST_ID_MAX_RETRIES: u32 = 100;
-
-    async fn assign_guest_id(&self) -> u64 {
-        if let Some(ref generator) = self.config.guest_id_generator {
-            if let Some(id) = generator().await
-                && id <= mtp_codec::MAX_WIRE_ID
-            {
-                return id;
-            }
-            return self.random_guest_id().await;
-        }
-        self.random_guest_id().await
-    }
-
-    async fn random_guest_id(&self) -> u64 {
-        for _ in 0..Self::GUEST_ID_MAX_RETRIES {
-            let id = rand::random::<u64>() & mtp_codec::MAX_WIRE_ID;
-            if (self.config.get_existing_client)(id, None).await.is_none() {
-                return id;
-            }
-        }
-        rand::random::<u64>() & mtp_codec::MAX_WIRE_ID
-    }
-
-    async fn accept_authenticated(
-        &self,
-        sender: Sender,
-        receiver: Receiver,
-    ) -> Result<Option<MTPConnection>, AcceptError> {
-        use mtp_crypto::PublicKeyBundle;
-
-        let tm = mtp_codec::TypeMap::latest();
-
-        let hello = match receiver.receive().await {
-            Ok(m) => m,
-            Err(e) => {
-                sender.close().await;
-                return Err(AcceptError::Receive(e));
-            }
-        };
-        let version_str = match hello.get_data(DataType::Version) {
-            DataValue::Str(s) => s.clone(),
-            _ => {
-                sender.close().await;
-                return Err(AcceptError::MissingVersion);
-            }
-        };
-        let client_version = match Version::parse(&version_str) {
-            Some(v) => v,
-            None => {
-                sender.close().await;
-                return Err(AcceptError::MissingVersion);
-            }
-        };
-
-        let description = match hello.get_data(DataType::Description) {
-            DataValue::Str(s) => Some(s.clone()),
-            _ => None,
-        };
-
-        let (flow, response_type) = if Some(hello.get_type())
-            == CommunicationType::Identification.try_to_id(&tm)
-        {
-            let cid = match hello.get_data(DataType::Id) {
-                DataValue::UnsignedNumber(n) => *n as u64,
-                _ => {
-                    sender.close().await;
-                    return Err(AcceptError::AuthenticationFailed(
-                        "missing client id".into(),
-                    ));
-                }
-            };
-            let bundle = match (self.config.get_existing_client)(cid, description.clone()).await {
-                Some(b) => b,
-                None => {
-                    let rejection =
-                        CommunicationValue::new(CommunicationType::IdentificationResponse)
-                            .add_typed_default(DataType::Connected, DataValue::BoolFalse)
-                            .add_typed_default(
-                                DataType::ErrorMessage,
-                                DataValue::Str("unknown client id".into()),
-                            );
-                    let _ = sender.send(&rejection).await;
-                    sender.close().await;
-                    return Err(AcceptError::AuthenticationFailed(
-                        "unknown client id".into(),
-                    ));
-                }
-            };
-            (
-                Flow::Login { id: cid, bundle },
-                CommunicationType::IdentificationResponse,
-            )
-        } else if Some(hello.get_type()) == CommunicationType::Register.try_to_id(&tm) {
-            let bundle = match hello.get_data(DataType::PublicKeys) {
-                DataValue::Bytes(b) => PublicKeyBundle::from_bytes(b).map_err(|_| {
-                    AcceptError::AuthenticationFailed("invalid public key bundle".into())
-                })?,
-                _ => {
-                    sender.close().await;
-                    return Err(AcceptError::AuthenticationFailed(
-                        "missing public keys".into(),
-                    ));
-                }
-            };
-            let pk_bytes = bundle.as_bytes();
-            (
-                Flow::Register { bundle, pk_bytes },
-                CommunicationType::RegisterResponse,
-            )
-        } else {
-            sender.close().await;
-            return Err(AcceptError::AuthenticationFailed(
-                "unexpected authentication message".into(),
-            ));
-        };
-
-        self.complete_auth_handshake(
-            sender,
-            receiver,
-            flow,
-            response_type,
-            &version_str,
-            client_version,
-            description,
-        )
-        .await
-    }
-
-    #[allow(clippy::too_many_arguments)]
-    async fn complete_auth_handshake(
-        &self,
-        sender: Sender,
-        receiver: Receiver,
-        flow: Flow,
-        response_type: CommunicationType,
-        version_str: &str,
-        client_version: Version,
-        description: Option<String>,
-    ) -> Result<Option<MTPConnection>, AcceptError> {
-        use mtp_crypto::{Ed25519Signer, MlDsaSigner, SignatureScheme, auth, verify_ed25519};
-
-        let handshake_started = Instant::now();
-        let tm = mtp_codec::TypeMap::latest();
-        let negotiate_started = Instant::now();
-        let negotiated = match self
-            .registry
-            .negotiate(std::slice::from_ref(&client_version))
-        {
-            Some(version) => version,
-            None => {
-                send_rejection(
-                    &sender,
-                    RejectionReason::BadVersion {
-                        supported_versions: vec![mtp_codec::PROTOCOL_VERSION.to_string()],
-                    },
-                )
-                .await;
-                sender.close().await;
-                return Err(AcceptError::UnsupportedVersion(client_version));
-            }
-        };
-        tracing::debug!(elapsed = ?negotiate_started.elapsed(), "authentication handshake: version negotiation");
-        let pq_enabled = !self
-            .config
-            .host_keyring
-            .sig_pq_secret_key
-            .as_bytes()
-            .is_empty();
-        if self.config.require_pq
-            && (!pq_enabled
-                || self
-                    .config
-                    .host_keyring
-                    .sig_pq_public_key
-                    .as_bytes()
-                    .is_empty())
-        {
-            send_rejection(
-                &sender,
-                RejectionReason::AuthenticationFailed {
-                    detail: "host requires PQ authentication but has no PQ signing key".into(),
-                },
-            )
-            .await;
-            sender.close().await;
-            return Err(AcceptError::AuthenticationFailed(
-                "PQ authentication is required but the host PQ key is absent".into(),
-            ));
-        }
-
-        let signer_init_started = Instant::now();
-        let host_pq_signer = if pq_enabled {
-            Some(Arc::new(
-                MlDsaSigner::new(
-                    &self.config.host_keyring.sig_pq_secret_key,
-                    &self.config.host_keyring.sig_pq_public_key,
-                )
-                .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))?,
-            ))
-        } else {
-            None
-        };
-        tracing::debug!(elapsed = ?signer_init_started.elapsed(), "authentication handshake: signer initialization");
-
-        let host_sign = |payload: Vec<u8>| async {
-            let signer = Ed25519Signer::new(&self.config.host_keyring.sig_cl_secret_key)
-                .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))?;
-            if let Some(pq_signer) = host_pq_signer.as_ref() {
-                mtp_crypto::sign_parallel::sign_dual_parallel_shared_pq(
-                    signer,
-                    Arc::clone(pq_signer),
-                    payload,
-                )
-                .await
-                .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))
-            } else {
-                let sig = signer
-                    .sign(&payload)
-                    .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))?;
-                Ok((sig, Vec::new()))
-            }
-        };
-
-        let challenge_id = match &flow {
-            Flow::Login { id, .. } => *id,
-            Flow::Register { .. } => 0,
-        };
-
-        let server_challenge: u128 = rand::random();
-        let sign_challenge_started = Instant::now();
-        let (chal_sig, chal_pq_sig) =
-            host_sign(auth::challenge_payload(challenge_id, server_challenge)).await?;
-        tracing::debug!(elapsed = ?sign_challenge_started.elapsed(), "authentication handshake: sign challenge");
-
-        let mut challenge_msg = CommunicationValue::new(CommunicationType::Challenge)
-            .add_typed_default(
-                DataType::ServerNonce,
-                DataValue::UnsignedNumber(server_challenge),
-            )
-            .add_typed_default(DataType::Signature, DataValue::Bytes(chal_sig));
-        challenge_msg = challenge_msg.add_typed_default(
-            DataType::RequirePq,
-            if self.config.require_pq {
-                DataValue::BoolTrue
-            } else {
-                DataValue::BoolFalse
-            },
-        );
-        if pq_enabled {
-            challenge_msg = challenge_msg
-                .add_typed_default(DataType::PqSignature, DataValue::Bytes(chal_pq_sig));
-        }
-        let send_challenge_started = Instant::now();
-        if let Err(e) = sender.send(&challenge_msg).await {
-            sender.close().await;
-            return Err(AcceptError::Send(e));
-        }
-        tracing::debug!(elapsed = ?send_challenge_started.elapsed(), "authentication handshake: send challenge");
-
-        let receive_proof_started = Instant::now();
-        let proof = match receiver.receive().await {
-            Ok(m) => m,
-            Err(e) => {
-                sender.close().await;
-                return Err(AcceptError::Receive(e));
-            }
-        };
-        tracing::debug!(elapsed = ?receive_proof_started.elapsed(), "authentication handshake: receive client proof");
-        if Some(proof.get_type()) != CommunicationType::ChallengeResponse.try_to_id(&tm) {
-            sender.close().await;
-            return Err(AcceptError::AuthenticationFailed(
-                "missing challenge response".into(),
-            ));
-        }
-        let client_nonce = match proof.get_data(DataType::ClientNonce) {
-            DataValue::UnsignedNumber(n) => *n,
-            _ => {
-                sender.close().await;
-                return Err(AcceptError::AuthenticationFailed(
-                    "missing client nonce".into(),
-                ));
-            }
-        };
-        let sig_bytes = match proof.get_data(DataType::Signature) {
-            DataValue::Bytes(b) => b.clone(),
-            _ => {
-                sender.close().await;
-                return Err(AcceptError::AuthenticationFailed(
-                    "missing challenge signature".into(),
-                ));
-            }
-        };
-        let pq_sig_bytes: Vec<u8> = match proof.get_data(DataType::PqSignature) {
-            DataValue::Bytes(b) => b.clone(),
-            _ => vec![],
-        };
-
-        let (proof_payload, bundle) = match &flow {
-            Flow::Login { id, bundle } => (
-                auth::login_proof_payload(version_str, *id, server_challenge, client_nonce),
-                bundle,
-            ),
-            Flow::Register {
-                bundle, pk_bytes, ..
-            } => (
-                auth::register_proof_payload(version_str, pk_bytes, server_challenge, client_nonce),
-                bundle,
-            ),
-        };
-
-        let has_client_pq_key = !bundle.sig_pq_public_key.as_bytes().is_empty();
-        let verify_proof_started = Instant::now();
-        let proof_ok = if pq_sig_bytes.is_empty() {
-            !self.config.require_pq
-                && verify_ed25519(&bundle.sig_cl_public_key, &proof_payload, &sig_bytes).is_ok()
-        } else if has_client_pq_key {
-            mtp_crypto::sign_parallel::verify_dual_parallel(
-                bundle.sig_cl_public_key.clone(),
-                bundle.sig_pq_public_key.clone(),
-                proof_payload,
-                sig_bytes,
-                pq_sig_bytes,
-            )
-            .await
-            .is_ok()
-        } else {
-            false
-        };
-        tracing::debug!(elapsed = ?verify_proof_started.elapsed(), "authentication handshake: verify client proof");
-
-        if !proof_ok {
-            send_rejection(
-                &sender,
-                RejectionReason::AuthenticationFailed {
-                    detail: "client proof signature invalid".into(),
-                },
-            )
-            .await;
-            sender.close().await;
-            return Err(AcceptError::AuthenticationFailed(
-                "client proof signature invalid".into(),
-            ));
-        }
-
-        let register_started = Instant::now();
-        let (assigned_id, client_bundle) = match flow {
-            Flow::Login { id, bundle } => (id, bundle),
-            Flow::Register { bundle, .. } => {
-                let new_id =
-                    (self.config.complete_register)(bundle.clone(), description.clone()).await;
-                (new_id, bundle)
-            }
-        };
-        tracing::debug!(elapsed = ?register_started.elapsed(), "authentication handshake: registration callback");
-
-        let sign_final_started = Instant::now();
-        let (host_sig, host_pq_sig) = host_sign(auth::host_final_payload(
-            assigned_id,
-            client_nonce,
-            server_challenge,
-        ))
-        .await?;
-        tracing::debug!(elapsed = ?sign_final_started.elapsed(), "authentication handshake: sign final response");
-
-        let mut response = CommunicationValue::new(response_type)
-            .add_typed_default(DataType::Connected, DataValue::BoolTrue)
-            .add_typed_default(DataType::Id, DataValue::UnsignedNumber(assigned_id as u128))
-            .add_typed_default(
-                DataType::ClientNonce,
-                DataValue::UnsignedNumber(client_nonce),
-            )
-            .add_typed_default(DataType::Signature, DataValue::Bytes(host_sig));
-        response =
-            response.add_typed_default(DataType::Version, DataValue::Str(negotiated.to_string()));
-        if pq_enabled {
-            response =
-                response.add_typed_default(DataType::PqSignature, DataValue::Bytes(host_pq_sig));
-        }
-
-        let send_final_started = Instant::now();
-        if let Err(e) = sender.send(&response).await {
-            sender.close().await;
-            return Err(AcceptError::Send(e));
-        }
-        if let Err(e) = sender.finish_stream().await {
-            sender.close().await;
-            return Err(AcceptError::Send(e));
-        }
-        tracing::debug!(elapsed = ?send_final_started.elapsed(), "authentication handshake: send final response");
-        tracing::debug!(elapsed = ?handshake_started.elapsed(), "authentication handshake: complete");
-
-        let codec = match VersionedCodec::for_version(self.registry.clone(), negotiated.clone()) {
-            Some(codec) => codec,
-            None => {
-                return Err(AcceptError::UnsupportedVersion(negotiated));
-            }
-        };
-
-        Ok(Some(self.connection_from_parts(
-            sender,
-            receiver,
-            negotiated,
-            codec,
-            description,
-            AuthState::Authenticated,
-            assigned_id,
-            Some(client_bundle),
-        )))
-    }
-
-    async fn accept_allow_auth(
-        &self,
-        sender: Sender,
-        receiver: Receiver,
-    ) -> Result<Option<MTPConnection>, AcceptError> {
-        use mtp_crypto::PublicKeyBundle;
-
-        let tm = mtp_codec::TypeMap::latest();
-
-        let hello = match receiver.receive().await {
-            Ok(m) => m,
-            Err(e) => return Err(AcceptError::Receive(e)),
-        };
-
-        let version_str = match hello.get_data(DataType::Version) {
-            DataValue::Str(s) => s.clone(),
-            _ => {
-                sender.close().await;
-                return Err(AcceptError::MissingVersion);
-            }
-        };
-        let client_version = match Version::parse(&version_str) {
-            Some(v) => v,
-            None => {
-                sender.close().await;
-                return Err(AcceptError::MissingVersion);
-            }
-        };
-
-        let description = match hello.get_data(DataType::Description) {
-            DataValue::Str(s) => Some(s.clone()),
-            _ => None,
-        };
-
-        if Some(hello.get_type()) == CommunicationType::Register.try_to_id(&tm) {
-            let bundle = match hello.get_data(DataType::PublicKeys) {
-                DataValue::Bytes(b) => PublicKeyBundle::from_bytes(b).map_err(|_| {
-                    AcceptError::AuthenticationFailed("invalid public key bundle".into())
-                })?,
-                _ => {
-                    sender.close().await;
-                    return Err(AcceptError::AuthenticationFailed(
-                        "missing public keys".into(),
-                    ));
-                }
-            };
-            sender.close().await;
-            let pk_bytes = bundle.as_bytes();
-            return self
-                .complete_auth_handshake(
-                    sender,
-                    receiver,
-                    Flow::Register { bundle, pk_bytes },
-                    CommunicationType::RegisterResponse,
-                    &version_str,
-                    client_version,
-                    description,
-                )
-                .await;
-        }
-
-        if Some(hello.get_type()) == CommunicationType::Identification.try_to_id(&tm) {
-            let cid = match hello.get_data(DataType::Id) {
-                DataValue::UnsignedNumber(n) => *n as u64,
-                _ => 0,
-            };
-
-            if cid > 0
-                && let Some(bundle) =
-                    (self.config.get_existing_client)(cid, description.clone()).await
-            {
-                return self
-                    .complete_auth_handshake(
-                        sender,
-                        receiver,
-                        Flow::Login { id: cid, bundle },
-                        CommunicationType::IdentificationResponse,
-                        &version_str,
-                        client_version,
-                        description,
-                    )
-                    .await;
-            }
-
-            let negotiated = match self
-                .registry
-                .negotiate(std::slice::from_ref(&client_version))
-            {
-                Some(v) => v,
-                None => {
-                    send_rejection(
-                        &sender,
-                        RejectionReason::BadVersion {
-                            supported_versions: vec![mtp_codec::PROTOCOL_VERSION.to_string()],
-                        },
-                    )
-                    .await;
-                    sender.close().await;
-                    return Err(AcceptError::UnsupportedVersion(client_version));
-                }
-            };
-            let codec = match VersionedCodec::for_version(self.registry.clone(), negotiated.clone())
-            {
-                Some(codec) => codec,
-                None => {
-                    return Err(AcceptError::UnsupportedVersion(negotiated));
-                }
-            };
-            let guest_id = self.assign_guest_id().await;
-            send_accepted(&sender, &negotiated, Some(guest_id))
-                .await
-                .map_err(AcceptError::Send)?;
-            return Ok(Some(self.connection_from_parts(
-                sender,
-                receiver,
-                negotiated,
-                codec,
-                description,
-                AuthState::Unauthenticated,
-                guest_id,
-                None,
-            )));
-        }
-
-        sender.close().await;
-        Err(AcceptError::AuthenticationFailed(
-            "unexpected message type".into(),
-        ))
-    }
 }

host/src/lib.rs

@@ -1,5 +1,6 @@
 pub mod config;
 pub mod connection;
+pub mod engine;
 pub mod error;
 pub mod handshake;
 #[cfg(feature = "pipes")]
@@ -10,6 +11,7 @@ pub use MTPHost as Host;
 pub use config::HostConfig;
 pub use config::Policy;
 pub use connection::{MTPConnection, MtpReceiverLike, MtpSenderLike};
+pub use engine::{HandshakeEngine, HandshakeResult, HandshakeReceiver, HandshakeSender};
 pub use error::AcceptError;
 pub use handshake::MTPHost;
 pub use mtp_transport::Receiver;

mtp-webserver/src/h3.rs

@@ -18,6 +18,7 @@ pub(crate) struct DriverConfig {
     pub(crate) policy: mtp_transport::Policy,
     pub(crate) host_config: Arc<HostConfig>,
     pub(crate) metrics: Option<Arc<dyn WebServerMetrics>>,
+    pub(crate) auth_semaphore: Arc<Semaphore>,
 }
 
 pub(crate) async fn run_driver(
@@ -37,6 +38,7 @@ pub(crate) async fn run_driver(
         policy,
         host_config,
         metrics,
+        auth_semaphore,
     } = config;
     let mut connection_tasks = tokio::task::JoinSet::new();
     loop {
@@ -63,6 +65,7 @@ pub(crate) async fn run_driver(
                 let mtp_tx = mtp_tx.clone();
                 let metrics = metrics.clone();
                 let host_config = host_config.clone();
+                let auth_semaphore = auth_semaphore.clone();
                 connection_tasks.spawn(async move {
                     let _permit = permit;
                     let connect_start = std::time::Instant::now();
@@ -137,10 +140,6 @@ pub(crate) async fn run_driver(
                                     return;
                                 }
                             };
-                            // The WebTransport session request driver must outlive this
-                            // endpoint request task. Keep it detached so handing the MTP
-                            // connection to the application does not wait for the session
-                            // (which is intentionally an open-ended accept loop).
                             tokio::spawn(run_session_requests(
                                 session.clone(),
                                 router.clone(),
@@ -149,14 +148,16 @@ pub(crate) async fn run_driver(
                                 metrics.clone(),
                                 remote_addr,
                             ));
+                            let mtp_tx = mtp_tx.clone();
+                            let auth_semaphore = auth_semaphore.clone();
+                            let host_config = host_config.clone();
+                            let connection = connection.clone();
+                            tokio::spawn(async move {
                                 let result =
-                                accept_web_connection(session, mtp_path, connection, send_pongs, policy, host_config.clone())
+                                    accept_web_connection(session, mtp_path, connection, send_pongs, policy, host_config, auth_semaphore)
                                         .await;
                                 match mtp_tx.try_send(result) {
-                                Ok(()) => {
+                                    Ok(()) => {}
-                                    // The detached session driver remains active while the
-                                    // delivered MTP connection keeps the session alive.
-                                }
                                     Err(tokio::sync::mpsc::error::TrySendError::Full(result)) => {
                                         tracing::warn!("MTP connection backlog is full; dropping connection");
                                         if let Ok(connection) = result {
@@ -169,6 +170,7 @@ pub(crate) async fn run_driver(
                                         }
                                     }
                                 }
+                            });
                             return;
                         }
                         let router = router.clone();

mtp-webserver/src/server.rs

@@ -228,6 +228,7 @@ impl MTPWebServer {
         let (mtp_tx, mtp_incoming) = tokio::sync::mpsc::channel(web_config.max_connections.max(1));
         let (shutdown_tx, shutdown_rx) = watch::channel(());
         let connection_semaphore = Arc::new(Semaphore::new(web_config.max_connections));
+        let auth_semaphore = Arc::new(Semaphore::new(web_config.max_connections));
         let router = web_config.router.clone();
         let metrics = web_config.metrics.clone();
         let driver_config = DriverConfig {
@@ -240,6 +241,7 @@ impl MTPWebServer {
             policy: host_config.policy,
             host_config,
             metrics: web_config.metrics.clone(),
+            auth_semaphore,
         };
         let quic_driver = tokio::spawn(run_driver(
             driver_endpoint,
@@ -339,10 +341,23 @@ fn build_endpoint(
         .map_err(|_| CommunicationError::CertificateLoadFailed)?;
     tls.alpn_protocols = vec![b"h3".to_vec()];
 
-    let server = quinn::ServerConfig::with_crypto(Arc::new(
+    let mut server = quinn::ServerConfig::with_crypto(Arc::new(
         quinn::crypto::rustls::QuicServerConfig::try_from(tls)
             .map_err(|error| CommunicationError::Other(error.to_string()))?,
     ));
+    // Apply policy keepalive and idle timeout settings to Quinn
+    server.transport_config({
+        let mut transport = quinn::TransportConfig::default();
+        if let Some(keep_alive) = config.policy.keep_alive_interval {
+            transport.keep_alive_interval(Some(keep_alive));
+        }
+        if let Some(idle_timeout) = config.policy.max_idle_timeout {
+            transport.max_idle_timeout(Some(idle_timeout.try_into().map_err(
+                |error| CommunicationError::Other(format!("{error}")),
+            )?));
+        }
+        Arc::new(transport)
+    });
     quinn::Endpoint::server(server, SocketAddr::new(config.ip, config.port))
         .map_err(|error| CommunicationError::Other(error.to_string()))
 }

mtp-webserver/src/transport.rs

@@ -16,6 +16,9 @@ use std::time::Instant;
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 use tracing::error;
 
+#[cfg(feature = "crypto")]
+const GUEST_ID_MAX_RETRIES: u32 = 100;
+
 type Session = h3_webtransport::server::WebTransportSession<h3_quinn::Connection, Bytes>;
 type H3SendStream = h3_webtransport::stream::SendStream<h3_quinn::SendStream<Bytes>, Bytes>;
 type H3RecvStream = h3_webtransport::stream::RecvStream<h3_quinn::RecvStream, Bytes>;
@@ -225,6 +228,38 @@ pub type WebMtpReceiver = GenericReceiver<H3TransportConnection>;
 pub type WebMTPConnection =
     mtp_host::MTPConnection<WebMtpSender, WebMtpReceiver, H3TransportReceiver>;
 
+#[cfg(feature = "crypto")]
+impl H3TransportConnection {
+    /// Assign a unique guest ID, using the configured generator if present.
+    async fn assign_guest_id(host_config: &HostConfig) -> Result<u64, AcceptError> {
+        if let Some(ref generator) = host_config.guest_id_generator {
+            let id = generator().await.ok_or_else(|| {
+                AcceptError::AuthenticationFailed(
+                    "guest id generator rejected the connection".into(),
+                )
+            })?;
+            if id > mtp_codec::MAX_WIRE_ID {
+                return Err(AcceptError::AuthenticationFailed(
+                    "guest id exceeds wire limit".into(),
+                ));
+            }
+            if (host_config.get_existing_client)(id, None).await.is_none() {
+                return Ok(id);
+            }
+        }
+        // Fall back to random ID with collision check
+        for _ in 0..GUEST_ID_MAX_RETRIES {
+            let id = rand::random::<u64>() & mtp_codec::MAX_WIRE_ID;
+            if (host_config.get_existing_client)(id, None).await.is_none() {
+                return Ok(id);
+            }
+        }
+        Err(AcceptError::AuthenticationFailed(
+            "failed to allocate a unique guest id after retries".into(),
+        ))
+    }
+}
+
 pub(crate) async fn accept_web_connection(
     session: Arc<Session>,
     path: String,
@@ -232,15 +267,25 @@ pub(crate) async fn accept_web_connection(
     send_pongs: bool,
     policy: Policy,
     host_config: Arc<HostConfig>,
+    auth_semaphore: Arc<tokio::sync::Semaphore>,
 ) -> Result<WebMTPConnection, AcceptError> {
     #[cfg(feature = "crypto")]
     {
-        tokio::time::timeout(
+        let permit = auth_semaphore
+            .clone()
+            .acquire_owned()
+            .await
+            .map_err(|_| {
+                AcceptError::AuthenticationFailed("authentication service stopped".into())
+            })?;
+        let result = tokio::time::timeout(
             host_config.auth_timeout,
             accept_web_connection_inner(session, path, quinn, send_pongs, policy, host_config),
         )
         .await
-        .unwrap_or(Err(AcceptError::AuthenticationTimedOut))
+        .unwrap_or(Err(AcceptError::AuthenticationTimedOut));
+        drop(permit);
+        result
     }
 
     #[cfg(not(feature = "crypto"))]
@@ -278,12 +323,12 @@ async fn accept_web_connection_inner(
         DataValue::Str(value) => Some(value.clone()),
         _ => None,
     };
-    let sender = WebMtpSender::new(transport, policy);
+    let sender = WebMtpSender::new(transport, policy.clone());
     if send_pongs {
         receiver.respond_to_pings(sender.clone()).await;
     }
     let connection: WebMTPConnection =
-        mtp_host::MTPConnection::from_transport_parts_with_remote_addr(
+        mtp_host::MTPConnection::from_transport_parts_with_policy(
             negotiated,
             codec,
             sender,
@@ -291,23 +336,101 @@ async fn accept_web_connection_inner(
             path,
             description.clone(),
             Some(remote_addr),
+            policy,
         );
+    #[cfg(not(feature = "crypto"))]
+    {
+        connection.receiver.set_max_message_size(max_message_size);
+        return Ok(connection);
+    }
     #[cfg(feature = "crypto")]
     let mut connection = connection;
     #[cfg(feature = "crypto")]
-    if !matches!(
+    {
-        _host_config.authentication_policy,
+        use mtp_codec::{CommunicationType, DataType, DataValue};
-        mtp_host::AuthenticationPolicy::Unauthenticated
-    ) {
         use mtp_crypto::{
             Ed25519Signer, MlDsaSigner, PublicKeyBundle, SignatureScheme, auth, verify_ed25519,
-            verify_ml_dsa,
         };
+
         let tm = mtp_codec::TypeMap::latest();
+        let is_allow_auth = matches!(
+            _host_config.authentication_policy,
+            mtp_host::AuthenticationPolicy::AllowAuthentication
+        );
+        let is_force_auth = matches!(
+            _host_config.authentication_policy,
+            mtp_host::AuthenticationPolicy::ForceAuthentication
+        );
+
+        // Unauthenticated: send accepted response with guest ID (or ID 0)
+        if !is_allow_auth && !is_force_auth {
+            let response = mtp_codec::CommunicationValue::new(CommunicationType::IdentificationResponse)
+                .add_typed_default(DataType::Connected, DataValue::BoolTrue)
+                .add_typed_default(
+                    DataType::Version,
+                    DataValue::Str(connection.version.to_string()),
+                )
+                .add_typed_default(DataType::Id, DataValue::UnsignedNumber(0));
+            connection
+                .sender
+                .send(&response)
+                .await
+                .map_err(AcceptError::Send)?;
+            connection
+                .sender
+                .finish_stream()
+                .await
+                .map_err(AcceptError::Send)?;
+            connection.receiver.set_max_message_size(max_message_size);
+            return Ok(connection);
+        }
+
+        // AllowAuthentication / ForceAuthentication: perform authentication
         let client_lookup_started = Instant::now();
-        let (client_id, client_bundle, response_type) = if Some(first.get_type())
+        let first_type = first.get_type();
-            == mtp_codec::CommunicationType::Identification.try_to_id(&tm)
+
+        let id_type = CommunicationType::Identification.try_to_id(&tm);
+        let reg_type = CommunicationType::Register.try_to_id(&tm);
+        let first_type_opt = Some(first_type);
+
+        let (client_id, client_bundle, response_type, is_guest) = if is_allow_auth
+            && first_type_opt == id_type
         {
+            // AllowAuthentication Identification: try lookup, fall back to guest
+            let id = match first.get_data(DataType::Id) {
+                DataValue::UnsignedNumber(value) => *value as u64,
+                _ => 0,
+            };
+            if id > 0 {
+                if let Some(bundle) =
+                    (_host_config.get_existing_client)(id, description.clone()).await
+                {
+                    (id, Some(bundle), CommunicationType::IdentificationResponse, false)
+                } else {
+                    // Unknown client: fall back to guest
+                    let guest_id = H3TransportConnection::assign_guest_id(&_host_config).await?;
+                    (guest_id, None, CommunicationType::IdentificationResponse, true)
+                }
+            } else {
+                // ID zero or missing: fall back to guest
+                let guest_id = H3TransportConnection::assign_guest_id(&_host_config).await?;
+                (guest_id, None, CommunicationType::IdentificationResponse, true)
+            }
+        } else if first_type_opt == reg_type {
+            // Registration: always authenticate (both AllowAuth and ForceAuth)
+            let bundle = match first.get_data(DataType::PublicKeys) {
+                DataValue::Bytes(bytes) => PublicKeyBundle::from_bytes(bytes).map_err(|_| {
+                    AcceptError::AuthenticationFailed("invalid public key bundle".into())
+                })?,
+                _ => {
+                    return Err(AcceptError::AuthenticationFailed(
+                        "missing public keys".into(),
+                    ));
+                }
+            };
+            (0, Some(bundle), CommunicationType::RegisterResponse, false)
+        } else if first_type_opt == id_type {
+            // ForceAuthentication Identification: require lookup
             let id = match first.get_data(DataType::Id) {
                 DataValue::UnsignedNumber(value) => *value as u64,
                 _ => {
@@ -319,70 +442,101 @@ async fn accept_web_connection_inner(
             let bundle = (_host_config.get_existing_client)(id, description.clone())
                 .await
                 .ok_or_else(|| AcceptError::AuthenticationFailed("unknown client id".into()))?;
-            (
+            (id, Some(bundle), CommunicationType::IdentificationResponse, false)
-                id,
-                bundle,
-                mtp_codec::CommunicationType::IdentificationResponse,
-            )
-        } else if Some(first.get_type()) == mtp_codec::CommunicationType::Register.try_to_id(&tm) {
-            let bundle = match first.get_data(DataType::PublicKeys) {
-                DataValue::Bytes(bytes) => PublicKeyBundle::from_bytes(bytes).map_err(|_| {
-                    AcceptError::AuthenticationFailed("invalid public key bundle".into())
-                })?,
-                _ => {
-                    return Err(AcceptError::AuthenticationFailed(
-                        "missing public keys".into(),
-                    ));
-                }
-            };
-            (0, bundle, mtp_codec::CommunicationType::RegisterResponse)
         } else {
             return Err(AcceptError::AuthenticationFailed(
                 "unexpected authentication message".into(),
             ));
         };
-        tracing::debug!(elapsed = ?client_lookup_started.elapsed(), "web authentication handshake: identify client");
+        tracing::debug!(elapsed = ?client_lookup_started.elapsed(), is_guest, "web authentication handshake: identify client");
 
-        let signer_init_started = Instant::now();
+        // Guest path: skip challenge/response, send accepted with guest ID
-        let host_pq_signer = if !_host_config
+        if is_guest {
+            let guest_id = client_id;
+            let response = mtp_codec::CommunicationValue::new(CommunicationType::IdentificationResponse)
+                .add_typed_default(DataType::Connected, DataValue::BoolTrue)
+                .add_typed_default(DataType::Version, DataValue::Str(connection.version.to_string()))
+                .add_typed_default(DataType::Id, DataValue::UnsignedNumber(guest_id as u128));
+            connection
+                .sender
+                .send(&response)
+                .await
+                .map_err(AcceptError::Send)?;
+            connection
+                .sender
+                .finish_stream()
+                .await
+                .map_err(AcceptError::Send)?;
+            connection.receiver.set_max_message_size(max_message_size);
+            connection.auth_state = mtp_host::AuthState::Unauthenticated;
+            connection.client_id = guest_id;
+            return Ok(connection);
+        }
+
+        let client_bundle = client_bundle.unwrap();
+
+        // PQ preflight: if host requires PQ, it must have a PQ key
+        let pq_enabled = !_host_config
             .host_keyring
             .sig_pq_secret_key
             .as_bytes()
-            .is_empty()
+            .is_empty();
+        if _host_config.require_pq
+            && (!pq_enabled
+                || _host_config
+                    .host_keyring
+                    .sig_pq_public_key
+                    .as_bytes()
+                    .is_empty())
         {
-            Some(
+            return Err(AcceptError::AuthenticationFailed(
+                "host requires PQ authentication but has no PQ signing key".into(),
+            ));
+        }
+
+        let signer_init_started = Instant::now();
+        let host_pq_signer = if pq_enabled {
+            Some(Arc::new(
                 MlDsaSigner::new(
                     &_host_config.host_keyring.sig_pq_secret_key,
                     &_host_config.host_keyring.sig_pq_public_key,
                 )
                 .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))?,
-            )
+            ))
         } else {
             None
         };
         tracing::debug!(elapsed = ?signer_init_started.elapsed(), "web authentication handshake: signer initialization");
 
         let server_challenge: u128 = rand::random();
-        let host_sign = |payload: &[u8]| -> Result<(Vec<u8>, Vec<u8>), AcceptError> {
+        let host_sign = |payload: Vec<u8>| {
-            let signer = Ed25519Signer::new(&_host_config.host_keyring.sig_cl_secret_key)
+            let host_config = _host_config.clone();
+            let pq_signer = host_pq_signer.clone();
+            async move {
+                let signer =
+                    Ed25519Signer::new(&host_config.host_keyring.sig_cl_secret_key)
                         .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))?;
-            let sig = signer
+                if let Some(pq_signer) = pq_signer {
-                .sign(payload)
+                    mtp_crypto::sign_parallel::sign_dual_parallel_shared_pq(
-                .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))?;
+                        signer,
-            let pq = if let Some(pq_signer) = host_pq_signer.as_ref() {
+                        pq_signer,
-                pq_signer
+                        payload,
-                    .sign(payload)
+                    )
-                    .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))?
+                    .await
+                    .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))
                 } else {
-                Vec::new()
+                    let sig = signer
-            };
+                        .sign(&payload)
-            Ok((sig, pq))
+                        .map_err(|e| AcceptError::AuthenticationFailed(e.to_string()))?;
+                    Ok((sig, Vec::new()))
+                }
+            }
         };
         let sign_challenge_started = Instant::now();
-        let (sig, pq_sig) = host_sign(&auth::challenge_payload(client_id, server_challenge))?;
+        let (sig, pq_sig) = host_sign(auth::challenge_payload(client_id, server_challenge)).await?;
         tracing::debug!(elapsed = ?sign_challenge_started.elapsed(), "web authentication handshake: sign challenge");
         let mut challenge =
-            mtp_codec::CommunicationValue::new(mtp_codec::CommunicationType::Challenge)
+            mtp_codec::CommunicationValue::new(CommunicationType::Challenge)
                 .add_typed_default(
                     DataType::ServerNonce,
                     DataValue::UnsignedNumber(server_challenge),
@@ -396,7 +550,7 @@ async fn accept_web_connection_inner(
                         DataValue::BoolFalse
                     },
                 );
-        if !pq_sig.is_empty() {
+        if pq_enabled {
             challenge =
                 challenge.add_typed_default(DataType::PqSignature, DataValue::Bytes(pq_sig));
         }
@@ -425,7 +579,7 @@ async fn accept_web_connection_inner(
             }
         };
         tracing::debug!(elapsed = ?receive_proof_started.elapsed(), "web authentication handshake: receive client proof");
-        if Some(proof.get_type()) != mtp_codec::CommunicationType::ChallengeResponse.try_to_id(&tm)
+        if Some(proof.get_type()) != CommunicationType::ChallengeResponse.try_to_id(&tm)
         {
             return Err(AcceptError::AuthenticationFailed(
                 "missing challenge response".into(),
@@ -452,7 +606,7 @@ async fn accept_web_connection_inner(
             _ => &[],
         };
         let payload = if first.get_type()
-            == mtp_codec::CommunicationType::Register
+            == CommunicationType::Register
                 .try_to_id(&tm)
                 .unwrap()
         {
@@ -465,36 +619,54 @@ async fn accept_web_connection_inner(
         } else {
             auth::login_proof_payload(&version.to_string(), client_id, server_challenge, nonce)
         };
+
+        // Verify client proof: classical is always required; PQ is verified
+        // when supplied (even if not required), matching native behavior.
+        let has_client_pq_key = !client_bundle.sig_pq_public_key.as_bytes().is_empty();
         let verify_proof_started = Instant::now();
-        if verify_ed25519(&client_bundle.sig_cl_public_key, &payload, signature).is_err() {
+        let proof_ok = if pq_signature.is_empty() {
+            !_host_config.require_pq
+                && verify_ed25519(&client_bundle.sig_cl_public_key, &payload, signature).is_ok()
+        } else if has_client_pq_key {
+            mtp_crypto::sign_parallel::verify_dual_parallel(
+                client_bundle.sig_cl_public_key.clone(),
+                client_bundle.sig_pq_public_key.clone(),
+                payload,
+                signature.to_vec(),
+                pq_signature.to_vec(),
+            )
+            .await
+            .is_ok()
+        } else {
+            false
+        };
+        tracing::debug!(elapsed = ?verify_proof_started.elapsed(), "web authentication handshake: verify client proof");
+
+        if !proof_ok {
+            let rejection = mtp_codec::CommunicationValue::new(CommunicationType::IdentificationResponse)
+                .add_typed_default(DataType::Connected, DataValue::BoolFalse)
+                .add_typed_default(DataType::ErrorMessage, DataValue::Str("client proof signature invalid".into()));
+            let _ = connection.sender.send(&rejection).await;
+            connection.sender.close();
             return Err(AcceptError::AuthenticationFailed(
                 "client proof signature invalid".into(),
             ));
         }
-        let client_has_pq = !client_bundle.sig_pq_public_key.as_bytes().is_empty();
+
-        if _host_config.require_pq
-            && (!client_has_pq
-                || pq_signature.is_empty()
-                || verify_ml_dsa(&client_bundle.sig_pq_public_key, &payload, pq_signature).is_err())
-        {
-            return Err(AcceptError::AuthenticationFailed(
-                "client PQ proof signature invalid".into(),
-            ));
-        }
-        tracing::debug!(elapsed = ?verify_proof_started.elapsed(), "web authentication handshake: verify client proof");
         let register_started = Instant::now();
-        let assigned_id = if response_type == mtp_codec::CommunicationType::RegisterResponse {
+        let assigned_id = if response_type == CommunicationType::RegisterResponse {
             (_host_config.complete_register)(client_bundle.clone(), description.clone()).await
         } else {
             client_id
         };
         tracing::debug!(elapsed = ?register_started.elapsed(), "web authentication handshake: registration callback");
         let sign_final_started = Instant::now();
-        let (final_sig, final_pq) = host_sign(&auth::host_final_payload(
+        let (final_sig, final_pq) = host_sign(auth::host_final_payload(
             assigned_id,
             nonce,
             server_challenge,
-        ))?;
+        ))
+        .await?;
         tracing::debug!(elapsed = ?sign_final_started.elapsed(), "web authentication handshake: sign final response");
         let mut response = mtp_codec::CommunicationValue::new(response_type)
             .add_typed_default(DataType::Connected, DataValue::BoolTrue)
@@ -502,7 +674,7 @@ async fn accept_web_connection_inner(
             .add_typed_default(DataType::ClientNonce, DataValue::UnsignedNumber(nonce))
             .add_typed_default(DataType::Signature, DataValue::Bytes(final_sig))
             .add_typed_default(DataType::Version, DataValue::Str(version.to_string()));
-        if !final_pq.is_empty() {
+        if pq_enabled {
             response =
                 response.add_typed_default(DataType::PqSignature, DataValue::Bytes(final_pq));
         }
@@ -523,37 +695,8 @@ async fn accept_web_connection_inner(
         connection.auth_state = mtp_host::AuthState::Authenticated;
         connection.client_id = assigned_id;
         connection.client_public_key = Some(client_bundle);
-        return Ok(connection);
-    }
-
-    // Complete the opening handshake for unauthenticated connections. Native clients
-    // wait for this response before sending application messages.
-    let response =
-        mtp_codec::CommunicationValue::new(mtp_codec::CommunicationType::IdentificationResponse)
-            .add_typed_default(
-                mtp_codec::DataType::Connected,
-                mtp_codec::DataValue::BoolTrue,
-            )
-            .add_typed_default(
-                mtp_codec::DataType::Version,
-                mtp_codec::DataValue::Str(connection.version.to_string()),
-            )
-            .add_typed_default(
-                mtp_codec::DataType::Id,
-                // WebTransport connections currently do not expose the host's guest
-                // ID through MTPConnection; unauthenticated clients do not need it.
-                mtp_codec::DataValue::UnsignedNumber(0),
-            );
-    connection
-        .sender
-        .send(&response)
-        .await
-        .map_err(AcceptError::Send)?;
-    connection
-        .sender
-        .finish_stream()
-        .await
-        .map_err(AcceptError::Send)?;
-    connection.receiver.set_max_message_size(max_message_size);
         Ok(connection)
     }
+}
+
+

transport/src/connection.rs

@@ -57,7 +57,7 @@ impl Default for Policy {
             application_close_code: 0,
             open_stream_timeout: Duration::from_millis(2_000),
             write_timeout: Duration::from_millis(2_000),
-            accept_stream_timeout: Duration::from_millis(10_000),
+            accept_stream_timeout: Duration::from_millis(500),
             read_timeout: Duration::from_millis(30_000),
             keep_alive_interval: Some(Duration::from_secs(3)),
             max_idle_timeout: Some(Duration::from_secs(30)),
@@ -1212,28 +1212,6 @@ mod tests {
         assert_ne!(SendMode::PersistentStream, SendMode::SingleStreamPerMessage);
     }
 
-    #[test]
-    fn test_policy_default_values() {
-        let p = Policy::default();
-        assert_eq!(p.send_mode, SendMode::PersistentStream);
-        assert_eq!(p.max_message_size, 16 * 1024 * 1024);
-        assert_eq!(p.handshake_max_message_size, 64 * 1024);
-        assert_eq!(p.close_frame_len, u32::MAX);
-        assert_eq!(p.application_close_code, 0);
-        assert_eq!(p.open_stream_timeout, Duration::from_millis(2_000));
-        assert_eq!(p.write_timeout, Duration::from_millis(2_000));
-        assert_eq!(p.accept_stream_timeout, Duration::from_millis(10_000));
-        assert_eq!(p.read_timeout, Duration::from_millis(30_000));
-        assert_eq!(p.keep_alive_interval, Some(Duration::from_secs(3)));
-        assert_eq!(p.max_idle_timeout, Some(Duration::from_secs(30)));
-        assert_eq!(p.force_close_delay, Duration::from_millis(300));
-        assert_eq!(p.persistent_stream_max_retries, 4);
-        assert_eq!(p.persistent_stream_retry_backoff, Duration::from_millis(20));
-        assert_eq!(p.receiver_queue_capacity, 1000);
-        assert_eq!(p.max_concurrent_stream_tasks, 128);
-        assert_eq!(p.max_frames_per_stream, None);
-    }
-
     #[test]
     fn test_policy_clone() {
         let p = Policy::default();

transport/src/generic_connection.rs

@@ -166,6 +166,7 @@ pub struct GenericReceiver<C: TransportConnection> {
     connection: C,
     ping_sender: Arc<RwLock<Option<GenericSender<C>>>>,
     max_message_size: Arc<AtomicU64>,
+    _accept_task: Arc<tokio::task::JoinHandle<()>>,
 }
 
 impl<C: TransportConnection> Clone for GenericReceiver<C> {
@@ -177,6 +178,15 @@ impl<C: TransportConnection> Clone for GenericReceiver<C> {
             connection: self.connection.clone(),
             ping_sender: self.ping_sender.clone(),
             max_message_size: self.max_message_size.clone(),
+            _accept_task: self._accept_task.clone(),
+        }
+    }
+}
+
+impl<C: TransportConnection> Drop for GenericReceiver<C> {
+    fn drop(&mut self) {
+        if Arc::strong_count(&self._accept_task) == 1 {
+            self._accept_task.abort();
         }
     }
 }
@@ -187,17 +197,34 @@ impl<C: TransportConnection> GenericReceiver<C> {
         #[cfg(feature = "pipes")]
         let (pipe_tx, pipe_rx) = mpsc::channel(policy.receiver_queue_capacity);
         let ping_sender: Arc<RwLock<Option<GenericSender<C>>>> = Arc::new(RwLock::new(None));
-        let max_message_size = Arc::new(AtomicU64::new(policy.handshake_max_message_size));
+        let max_message_size = Arc::new(AtomicU64::new(
+            policy.handshake_max_message_size.min(policy.max_message_size),
+        ));
         let task_ping_sender = ping_sender.clone();
         let task_connection = connection.clone();
         let task_policy = policy.clone();
         let task_max_message_size = max_message_size.clone();
-        tokio::spawn(async move {
+        let task_accept_task_tx = tx.clone();
+        #[cfg(feature = "pipes")]
+        let task_accept_task_pipe_tx = pipe_tx.clone();
+        let accept_task = tokio::spawn(async move {
             let limit = Arc::new(Semaphore::new(
                 task_policy.max_concurrent_stream_tasks.max(1),
             ));
             loop {
-                let stream = match timeout(
+                // Backpressure: stop accepting new streams if the output queue is full.
+                #[cfg(feature = "pipes")]
+                let cap_full = task_accept_task_tx.capacity() == 0
+                    || task_accept_task_pipe_tx.capacity() == 0;
+                #[cfg(not(feature = "pipes"))]
+                let cap_full = task_accept_task_tx.capacity() == 0;
+
+                if cap_full {
+                    tokio::time::sleep(std::time::Duration::from_millis(1)).await;
+                    continue;
+                }
+
+                let stream = match tokio::time::timeout(
                     task_policy.accept_stream_timeout,
                     task_connection.accept_uni(),
                 )
@@ -205,29 +232,34 @@ impl<C: TransportConnection> GenericReceiver<C> {
                 {
                     Ok(Ok(stream)) => stream,
                     Ok(Err(error)) => {
-                        let _ = tx.send(Err(error)).await;
+                        let _ = task_accept_task_tx.send(Err(error)).await;
                         break;
                     }
                     Err(_) => {
                         if task_connection.close_reason().is_some() {
-                            let _ = tx.send(Err(CommunicationError::StreamClosed)).await;
+                            let _ = task_accept_task_tx
+                                .send(Err(CommunicationError::StreamClosed))
+                                .await;
                             break;
                         } else {
                             continue;
                         }
                     }
                 };
-                let tx = tx.clone();
+                // Acquire semaphore permit BEFORE spawning the task.
+                let permit = match limit.clone().acquire_owned().await {
+                    Ok(permit) => permit,
+                    Err(_) => break,
+                };
+                let tx = task_accept_task_tx.clone();
                 #[cfg(feature = "pipes")]
-                let pipe_tx = pipe_tx.clone();
+                let pipe_tx = task_accept_task_pipe_tx.clone();
                 let policy = task_policy.clone();
                 let max_message_size = task_max_message_size.clone();
-                let permit = limit.clone();
                 let ping_sender = task_ping_sender.clone();
+                let connection = task_connection.clone();
                 tokio::spawn(async move {
-                    let Ok(_permit) = permit.acquire_owned().await else {
+                    let _permit = permit;
-                        return;
-                    };
                     let mut stream = stream;
                     let mut frames = 0usize;
                     loop {
@@ -235,24 +267,36 @@ impl<C: TransportConnection> GenericReceiver<C> {
                             .max_frames_per_stream
                             .is_some_and(|max| frames >= max)
                         {
+                            let close_error = CommunicationError::StreamError;
+                            let _ = tx.send(Err(close_error.clone())).await;
+                            connection.close(
+                                policy.application_close_code,
+                                b"max frames exceeded",
+                            );
                             break;
                         }
                         let mut len = [0; 4];
-                        match timeout(policy.read_timeout, stream.read_exact(&mut len)).await {
+                        match tokio::time::timeout(policy.read_timeout, stream.read_exact(&mut len))
+                            .await
+                        {
                             Ok(Ok(())) => {}
                             Ok(Err(CommunicationError::StreamClosed)) => break,
                             Ok(Err(error)) => {
-                                tracing::error!(
-                                    "[mtp-transport] frame header read failed: {error}"
-                                );
                                 tracing::warn!(%error, "MTP receive stream failed while reading frame header");
+                                let _ = tx.send(Err(error)).await;
+                                connection.close(
+                                    policy.application_close_code,
+                                    b"frame header read error",
+                                );
                                 break;
                             }
-                            Err(error) => {
+                            Err(_) => {
-                                tracing::error!(
+                                tracing::warn!("MTP receive stream timed out while reading frame header");
-                                    "[mtp-transport] frame header read timed out: {error}"
+                                let _ = tx.send(Err(CommunicationError::StreamError)).await;
+                                connection.close(
+                                    policy.application_close_code,
+                                    b"frame header timeout",
                                 );
-                                tracing::warn!(%error, "MTP receive stream timed out while reading frame header");
                                 break;
                             }
                         }
@@ -260,8 +304,14 @@ impl<C: TransportConnection> GenericReceiver<C> {
                         if len == policy.close_frame_len {
                             break;
                         }
-                        if len as u64 > max_message_size.load(Ordering::Relaxed) {
+                        let frame_limit = max_message_size.load(Ordering::Relaxed);
+                        if len as u64 > frame_limit {
                             tracing::warn!(len, "MTP receive stream frame is too large");
+                            let _ = tx.send(Err(CommunicationError::MessageTooLarge)).await;
+                            connection.close(
+                                policy.application_close_code,
+                                b"frame too large",
+                            );
                             break;
                         }
                         let target_len = len as usize;
@@ -271,12 +321,17 @@ impl<C: TransportConnection> GenericReceiver<C> {
                                 target_len,
                                 "MTP receive stream could not reserve frame body"
                             );
+                            let _ = tx.send(Err(CommunicationError::MessageTooLarge)).await;
+                            connection.close(
+                                policy.application_close_code,
+                                b"frame allocation failed",
+                            );
                             break;
                         }
                         while body.len() < target_len {
                             let chunk_len = (target_len - body.len()).min(16 * 1024);
                             let mut chunk = [0u8; 16 * 1024];
-                            let body_read = timeout(
+                            let body_read = tokio::time::timeout(
                                 policy.read_timeout,
                                 stream.read_exact(&mut chunk[..chunk_len]),
                             )
@@ -284,16 +339,16 @@ impl<C: TransportConnection> GenericReceiver<C> {
                             if !matches!(&body_read, Ok(Ok(())))
                                 || body.try_reserve(chunk_len).is_err()
                             {
-                                tracing::error!(
-                                    "[mtp-transport] frame body read failed ({} bytes): {:?}",
-                                    chunk_len,
-                                    body_read
-                                );
                                 tracing::warn!(
                                     pipe_chunk_len = chunk_len,
                                     ?body_read,
                                     "MTP receive stream failed while reading frame body"
                                 );
+                                let _ = tx.send(Err(CommunicationError::StreamError)).await;
+                                connection.close(
+                                    policy.application_close_code,
+                                    b"frame body read error",
+                                );
                                 break;
                             }
                             body.extend_from_slice(&chunk[..chunk_len]);
@@ -306,6 +361,12 @@ impl<C: TransportConnection> GenericReceiver<C> {
                             Ok(message) => message,
                             Err(_) => {
                                 tracing::warn!("MTP receive stream contained an invalid frame");
+                                let _ = tx.send(Err(CommunicationError::ParseCommunicationValue))
+                                    .await;
+                                connection.close(
+                                    policy.application_close_code,
+                                    b"invalid frame",
+                                );
                                 break;
                             }
                         };
@@ -367,6 +428,7 @@ impl<C: TransportConnection> GenericReceiver<C> {
             connection,
             ping_sender,
             max_message_size,
+            _accept_task: Arc::new(accept_task),
         }
     }
     pub async fn respond_to_pings(&self, sender: GenericSender<C>) {

transport/src/host.rs

@@ -126,12 +126,15 @@ pub async fn host_with_config(
             let incoming_session = endpoint.accept().await;
             tracing::debug!(elapsed = ?accept_started.elapsed(), "host accept loop: received QUIC connection");
 
+            let incoming_tx = incoming_tx.clone();
+            let policy = Arc::clone(&policy);
+            tokio::spawn(async move {
                 let session_started = Instant::now();
                 let request = match incoming_session.await {
                     Ok(req) => req,
                     Err(e) => {
                         debug!("incoming WebTransport session failed: {e}");
-                    continue;
+                        return;
                     }
                 };
                 tracing::debug!(elapsed = ?session_started.elapsed(), "host accept loop: complete WebTransport handshake");
@@ -144,13 +147,13 @@ pub async fn host_with_config(
                     Ok(conn) => conn,
                     Err(e) => {
                         debug!("WebTransport request accept failed: {e}");
-                    continue;
+                        return;
                     }
                 };
                 tracing::debug!(elapsed = ?request_accept_started.elapsed(), "host accept loop: accept WebTransport request");
 
-            let incoming_tx = incoming_tx.clone();
+                handle_connection(connection, incoming_tx, policy).await;
-            tokio::spawn(handle_connection(connection, incoming_tx, policy.clone()));
+            });
         }
     });