Make quinn-proto::{Connection, Endpoint} deterministic (#1691)

`quinn-proto::{Connection, Endpoint}` structs call
`StdRng::from_entropy()` in their implementation. It makes it hard to
reproduce errors in an otherwise deterministic test case.

This PR addresses the issue by adding a `StdRng` argument to the
respective `new` functions. For other functions that may create an
endpoint/connection, an argument of type `impl FnOnce() -> StdRng` is
added. This avoids eager calls to generate fresh entropy. e.g. the
`Endpoint::handle` function is frequently called but we'd only need the
rng when handling a new incoming connection.

quinn-proto/src/connection/mod.rs

@@ -252,6 +252,7 @@ impl Connection {
         now: Instant,
         version: u32,
         allow_mtud: bool,
+        rng_seed: [u8; 32],
     ) -> Self {
         let side = if server_config.is_some() {
             Side::Server
@@ -267,7 +268,7 @@ impl Connection {
             expected_token: Bytes::new(),
             client_hello: None,
         });
-        let mut rng = StdRng::from_entropy();
+        let mut rng = StdRng::from_seed(rng_seed);
         let path_validated = server_config.as_ref().map_or(true, |c| c.use_retry);
         let mut this = Self {
             endpoint_config,

quinn-proto/src/endpoint.rs

@@ -57,9 +57,10 @@ impl Endpoint {
         config: Arc<EndpointConfig>,
         server_config: Option<Arc<ServerConfig>>,
         allow_mtud: bool,
+        rng_seed: Option<[u8; 32]>,
     ) -> Self {
         Self {
-            rng: StdRng::from_entropy(),
+            rng: rng_seed.map_or(StdRng::from_entropy(), StdRng::from_seed),
             index: ConnectionIndex::default(),
             connections: Slab::new(),
             local_cid_generator: (config.connection_id_generator_factory.as_ref())(),
@@ -589,6 +590,8 @@ impl Endpoint {
         server_config: Option<Arc<ServerConfig>>,
         transport_config: Arc<TransportConfig>,
     ) -> Connection {
+        let mut rng_seed = [0; 32];
+        self.rng.fill_bytes(&mut rng_seed);
         let conn = Connection::new(
             self.config.clone(),
             server_config,
@@ -603,6 +606,7 @@ impl Endpoint {
             now,
             version,
             self.allow_mtud,
+            rng_seed,
         );
 
         let id = self.connections.insert(ConnectionMeta {

quinn-proto/src/tests/mod.rs

@@ -27,7 +27,12 @@ use util::*;
 fn version_negotiate_server() {
     let _guard = subscribe();
     let client_addr = "[::2]:7890".parse().unwrap();
-    let mut server = Endpoint::new(Default::default(), Some(Arc::new(server_config())), true);
+    let mut server = Endpoint::new(
+        Default::default(),
+        Some(Arc::new(server_config())),
+        true,
+        None,
+    );
     let now = Instant::now();
     let event = server.handle(
         now,
@@ -63,6 +68,7 @@ fn version_negotiate_client() {
         }),
         None,
         true,
+        None,
     );
     let (_, mut client_ch) = client
         .connect(Instant::now(), client_config(), server_addr, "localhost")
@@ -178,7 +184,8 @@ fn server_stateless_reset() {
     let mut pair = Pair::new(endpoint_config.clone(), server_config());
     let (client_ch, _) = pair.connect();
     pair.drive(); // Flush any post-handshake frames
-    pair.server.endpoint = Endpoint::new(endpoint_config, Some(Arc::new(server_config())), true);
+    pair.server.endpoint =
+        Endpoint::new(endpoint_config, Some(Arc::new(server_config())), true, None);
     // Force the server to generate the smallest possible stateless reset
     pair.client.connections.get_mut(&client_ch).unwrap().ping();
     info!("resetting");
@@ -203,7 +210,8 @@ fn client_stateless_reset() {
 
     let mut pair = Pair::new(endpoint_config.clone(), server_config());
     let (_, server_ch) = pair.connect();
-    pair.client.endpoint = Endpoint::new(endpoint_config, Some(Arc::new(server_config())), true);
+    pair.client.endpoint =
+        Endpoint::new(endpoint_config, Some(Arc::new(server_config())), true, None);
     // Send something big enough to allow room for a smaller stateless reset.
     pair.server.connections.get_mut(&server_ch).unwrap().close(
         pair.time,
@@ -1343,8 +1351,9 @@ fn cid_rotation() {
         }),
         Some(Arc::new(server_config())),
         true,
+        None,
     );
-    let client = Endpoint::new(Arc::new(EndpointConfig::default()), None, true);
+    let client = Endpoint::new(Arc::new(EndpointConfig::default()), None, true, None);
 
     let mut pair = Pair::new_from_endpoint(client, server);
     let (_, server_ch) = pair.connect();
@@ -1922,7 +1931,12 @@ fn big_cert_and_key() -> (rustls::Certificate, rustls::PrivateKey) {
 fn malformed_token_len() {
     let _guard = subscribe();
     let client_addr = "[::2]:7890".parse().unwrap();
-    let mut server = Endpoint::new(Default::default(), Some(Arc::new(server_config())), true);
+    let mut server = Endpoint::new(
+        Default::default(),
+        Some(Arc::new(server_config())),
+        true,
+        None,
+    );
     server.handle(
         Instant::now(),
         client_addr,
@@ -2024,12 +2038,13 @@ fn migrate_detects_new_mtu_and_respects_original_peer_max_udp_payload_size() {
         Arc::new(server_endpoint_config),
         Some(Arc::new(server_config())),
         true,
+        None,
     );
     let client_endpoint_config = EndpointConfig {
         max_udp_payload_size: VarInt::from(client_max_udp_payload_size),
         ..EndpointConfig::default()
     };
-    let client = Endpoint::new(Arc::new(client_endpoint_config), None, true);
+    let client = Endpoint::new(Arc::new(client_endpoint_config), None, true, None);
     let mut pair = Pair::new_from_endpoint(client, server);
     pair.mtu = 1300;
 

quinn-proto/src/tests/util.rs

@@ -49,8 +49,13 @@ impl Pair {
     }
 
     pub(super) fn new(endpoint_config: Arc<EndpointConfig>, server_config: ServerConfig) -> Self {
-        let server = Endpoint::new(endpoint_config.clone(), Some(Arc::new(server_config)), true);
-        let client = Endpoint::new(endpoint_config, None, true);
+        let server = Endpoint::new(
+            endpoint_config.clone(),
+            Some(Arc::new(server_config)),
+            true,
+            None,
+        );
+        let client = Endpoint::new(endpoint_config, None, true, None);
 
         Self::new_from_endpoint(client, server)
     }

quinn/src/endpoint.rs

@@ -110,7 +110,12 @@ impl Endpoint {
         let allow_mtud = !socket.may_fragment();
         let rc = EndpointRef::new(
             socket,
-            proto::Endpoint::new(Arc::new(config), server_config.map(Arc::new), allow_mtud),
+            proto::Endpoint::new(
+                Arc::new(config),
+                server_config.map(Arc::new),
+                allow_mtud,
+                None,
+            ),
             addr.is_ipv6(),
             runtime.clone(),
         );