test: protect durable behavior identified in review

crates/irtt-server/tests/session_behavior.rs

@@ -1,4 +1,7 @@
-use std::{net::SocketAddr, time::Duration};
+use std::{
+    net::{SocketAddr, SocketAddrV6},
+    time::Duration,
+};
 
 use irtt_proto::{decode_echo_reply, decode_open_reply, encode_request, Params, RequestToEncode};
 use irtt_server::{ServerConfig, ServerCore};
@@ -116,3 +119,143 @@ fn zero_burst_and_zero_idle_timeout_silently_refuse_echoes() {
         assert!(server.handle_datagram(peer, &echo).unwrap().is_none());
     }
 }
+
+#[test]
+fn ipv6_flow_labels_share_a_session_but_zones_do_not() {
+    let endpoint = |flow, scope| {
+        SocketAddr::V6(SocketAddrV6::new(
+            "fe80::1234".parse().unwrap(),
+            40000,
+            flow,
+            scope,
+        ))
+    };
+    let mut server =
+        ServerCore::new(ServerConfig::default().with_min_send_interval(Duration::ZERO));
+    let params = Params {
+        received_stats: irtt_proto::ReceivedStats::Both,
+        ..Params::with_protocol_defaults()
+    };
+    let packet = encode_request(
+        RequestToEncode::Open {
+            params: &params,
+            no_test: false,
+        },
+        None,
+    )
+    .unwrap();
+    let reply = server
+        .handle_datagram(endpoint(1, 2), &packet)
+        .unwrap()
+        .unwrap();
+    let opened = decode_open_reply(reply.bytes(), None).unwrap();
+    let echo = encode_request(
+        RequestToEncode::Echo {
+            token: opened.token,
+            sequence: 0,
+            params: &opened.params,
+            payload: &[],
+        },
+        None,
+    )
+    .unwrap();
+    let close = encode_request(
+        RequestToEncode::Close {
+            token: opened.token,
+        },
+        None,
+    )
+    .unwrap();
+    assert!(server
+        .handle_datagram(endpoint(1, 3), &echo)
+        .unwrap()
+        .is_none());
+    assert!(server
+        .handle_datagram(endpoint(1, 3), &close)
+        .unwrap()
+        .is_none());
+    assert_eq!(server.session_count(), 1);
+    let reply = server
+        .handle_datagram(endpoint(99, 2), &echo)
+        .unwrap()
+        .unwrap();
+    assert_eq!(
+        decode_echo_reply(reply.bytes(), &opened.params, None)
+            .unwrap()
+            .recv_count,
+        Some(1)
+    );
+    assert!(server
+        .handle_datagram(endpoint(99, 2), &close)
+        .unwrap()
+        .is_none());
+    assert_eq!(server.session_count(), 0);
+}
+
+#[test]
+fn oversized_authenticated_echo_does_not_advance_session_state() {
+    let key = b"oversized-echo-test";
+    let peer = "127.0.0.1:40000".parse().unwrap();
+    let mut server = ServerCore::new(
+        ServerConfig::default()
+            .with_hmac_key(key)
+            .with_max_packet_length(96)
+            .with_burst_allowance(1)
+            .with_min_send_interval(Duration::from_secs(60))
+            .with_max_test_duration(Duration::from_millis(1))
+            .with_idle_timeout(Duration::MAX),
+    );
+    let params = Params {
+        length: 96,
+        received_stats: irtt_proto::ReceivedStats::Both,
+        ..Params::with_protocol_defaults()
+    };
+    let open = encode_request(
+        RequestToEncode::Open {
+            params: &params,
+            no_test: false,
+        },
+        Some(key),
+    )
+    .unwrap();
+    let reply = server.handle_datagram(peer, &open).unwrap().unwrap();
+    let opened = decode_open_reply(reply.bytes(), Some(key)).unwrap();
+    let oversized_params = Params {
+        length: 128,
+        ..opened.params.clone()
+    };
+    let oversized = encode_request(
+        RequestToEncode::Echo {
+            token: opened.token,
+            sequence: 63,
+            params: &oversized_params,
+            payload: &[],
+        },
+        Some(key),
+    )
+    .unwrap();
+    assert!(oversized.len() > 96);
+    assert!(server.handle_datagram(peer, &oversized).unwrap().is_none());
+    // If the oversized request started maximum duration, the first valid
+    // echo would now close. Oversleep preserves this distinction.
+    std::thread::sleep(Duration::from_millis(2001));
+    let valid = encode_request(
+        RequestToEncode::Echo {
+            token: opened.token,
+            sequence: 0,
+            params: &opened.params,
+            payload: &[],
+        },
+        Some(key),
+    )
+    .unwrap();
+    let reply = server
+        .handle_datagram(peer, &valid)
+        .unwrap()
+        .expect("oversized request must not consume allowance");
+    let reply = decode_echo_reply(reply.bytes(), &opened.params, Some(key)).unwrap();
+    assert_eq!(reply.flags & irtt_proto::FLAG_CLOSE, 0);
+    assert_eq!(reply.recv_count, Some(1));
+    assert_eq!(reply.recv_window, Some(1));
+    assert_eq!(server.session_count(), 1);
+}