tests: rework the actually useful tests to live in the integration crate

crates/irtt-client/tests/linux_transport.rs

@@ -0,0 +1,259 @@
+//! Real Linux socket observations through the public client adapters.
+#![cfg(all(target_os = "linux", feature = "ancillary"))]
+
+use std::{
+    io::IoSliceMut,
+    net::{SocketAddr, UdpSocket},
+    sync::mpsc,
+    thread,
+    time::{Duration, SystemTime, UNIX_EPOCH},
+};
+
+use irtt_client::{Client, ClientConfig, ClientEvent, NegotiationPolicy, SocketConfig};
+use irtt_proto::{decode_request, Clock, DecodedRequestKind, ReceivedStats, StampAt};
+use irtt_server::{ServerConfig, ServerCore};
+use nix::sys::socket::{recvmsg, ControlMessageOwned, MsgFlags};
+
+const TEST_TTL: u32 = 37;
+
+// A compliant packet peer uses the real server core. Its receive-side IP_TOS
+// observation is independent of the client/server parameter agreement.
+fn peer(dscp_allowed: bool, probes: usize) -> (SocketAddr, thread::JoinHandle<Vec<u8>>) {
+    let socket = UdpSocket::bind("127.0.0.1:0").unwrap();
+    socket
+        .set_read_timeout(Some(Duration::from_secs(3)))
+        .unwrap();
+    socket2::SockRef::from(&socket)
+        .set_recv_tos_v4(true)
+        .unwrap();
+    nix::sys::socket::setsockopt(&socket, nix::sys::socket::sockopt::Ipv4RecvTtl, &true).unwrap();
+    let addr = socket.local_addr().unwrap();
+    let task = thread::spawn(move || {
+        let mut core = ServerCore::new(
+            ServerConfig::default()
+                .with_min_send_interval(Duration::ZERO)
+                .with_dscp_allowed(dscp_allowed),
+        );
+        let mut markings = Vec::new();
+        // OPEN, every ECHO, then CLOSE.
+        for _ in 0..probes + 2 {
+            let mut bytes = [0; 2048];
+            let mut control = nix::cmsg_space!(u8, i32);
+            let mut iov = [IoSliceMut::new(&mut bytes)];
+            let msg = recvmsg::<nix::sys::socket::SockaddrIn>(
+                std::os::fd::AsRawFd::as_raw_fd(&socket),
+                &mut iov,
+                Some(&mut control),
+                MsgFlags::empty(),
+            )
+            .unwrap();
+            let size = msg.bytes;
+            let source = msg.address.unwrap();
+            let marking = msg
+                .cmsgs()
+                .unwrap()
+                .find_map(|message| match message {
+                    ControlMessageOwned::Ipv4Tos(tos) => Some(tos),
+                    _ => None,
+                })
+                .expect("Linux must report IP_TOS");
+            let ttl = msg
+                .cmsgs()
+                .unwrap()
+                .find_map(|message| match message {
+                    ControlMessageOwned::Ipv4Ttl(ttl) => Some(ttl),
+                    _ => None,
+                })
+                .expect("Linux must report IP_TTL");
+            assert_eq!(
+                ttl, TEST_TTL as i32,
+                "configured TTL must survive OPEN, ECHO and CLOSE"
+            );
+            markings.push(marking);
+            let source = SocketAddr::from((source.ip(), source.port()));
+            if let Some(reply) = core.handle_datagram(source, &bytes[..size]).unwrap() {
+                socket.send_to(reply.bytes(), source).unwrap();
+            }
+        }
+        assert_eq!(core.session_count(), 0);
+        markings
+    });
+    (addr, task)
+}
+
+fn config(addr: SocketAddr) -> ClientConfig {
+    ClientConfig {
+        server_addr: addr.to_string(),
+        dscp: 46,
+        negotiation_policy: NegotiationPolicy::Loose,
+        duration: None,
+        interval: Duration::from_millis(10),
+        clock: Clock::Both,
+        stamp_at: StampAt::Both,
+        received_stats: ReceivedStats::Both,
+        length: 128,
+        open_timeouts: vec![Duration::from_secs(1)],
+        socket_config: SocketConfig {
+            ttl: Some(TEST_TTL),
+            recv_timeout: Some(Duration::from_secs(1)),
+            ..SocketConfig::default()
+        },
+        ..ClientConfig::default()
+    }
+}
+
+// TX timestamps have no separate public field: the upstream OWD exposes the
+// selected send endpoint. Reconstruct it and require a real kernel endpoint
+// rather than accepting the userspace fallback. RTT must still use sent_at.
+fn assert_kernel_send_endpoint(event: &ClientEvent, before_send: SystemTime) {
+    let ClientEvent::EchoReply {
+        sent_at,
+        received_at,
+        rtt,
+        server_timing: Some(timing),
+        one_way: Some(one_way),
+        packet_meta,
+        ..
+    } = event
+    else {
+        panic!("expected measured reply: {event:?}")
+    };
+    let ns = |wall: SystemTime| {
+        i128::try_from(wall.duration_since(UNIX_EPOCH).unwrap().as_nanos()).unwrap()
+    };
+    let selected =
+        i128::from(timing.receive_wall_ns.unwrap()) - one_way.client_to_server.unwrap().as_nanos();
+    assert!(selected >= ns(before_send));
+    // TX_SOFTWARE may arrive before or after send returns; only equality
+    // identifies the userspace fallback. Receipt remains the upper bound.
+    assert_ne!(
+        selected,
+        ns(sent_at.wall),
+        "TX timestamp was not observed; userspace fallback is insufficient"
+    );
+    assert!(selected <= ns(received_at.wall));
+    let selected_receive =
+        i128::from(timing.send_wall_ns.unwrap()) + one_way.server_to_client.unwrap().as_nanos();
+    assert_eq!(
+        selected_receive,
+        ns(packet_meta
+            .kernel_rx_timestamp
+            .expect("Linux RX timestamp required")),
+        "downstream OWD must use the kernel receive endpoint"
+    );
+    assert_eq!(rtt.raw, received_at.mono.duration_since(sent_at.mono));
+}
+
+#[test]
+fn blocking_probes_use_kernel_tx_timing_and_negotiated_packet_marking() {
+    for allowed in [true, false] {
+        const PROBES: usize = 3;
+        let (addr, peer) = peer(allowed, PROBES);
+        let mut client = Client::connect(config(addr)).unwrap();
+        client.open().unwrap();
+        assert_eq!(
+            client.negotiated_params().unwrap().params.dscp,
+            if allowed { 184 } else { 0 }
+        );
+        for _ in 0..PROBES {
+            let before = SystemTime::now();
+            client.send_probe().unwrap();
+            let events = client.recv_once().unwrap();
+            assert_eq!(events.len(), 1);
+            assert_kernel_send_endpoint(&events[0], before);
+        }
+        client.close().unwrap();
+        let markings = peer.join().unwrap();
+        assert_eq!(markings[0], 0, "OPEN is unmarked");
+        assert_eq!(
+            &markings[1..=PROBES],
+            vec![if allowed { 184 } else { 0 }; PROBES]
+        );
+        assert_eq!(
+            markings[PROBES + 1],
+            0,
+            "local CLOSE clears the negotiated marking"
+        );
+    }
+}
+
+#[cfg(feature = "tokio")]
+#[test]
+fn async_probes_use_kernel_tx_timing_and_negotiated_packet_marking() {
+    let runtime = tokio::runtime::Builder::new_current_thread()
+        .enable_all()
+        .build()
+        .unwrap();
+    for allowed in [true, false] {
+        const PROBES: usize = 3;
+        let (addr, peer) = peer(allowed, PROBES);
+        runtime.block_on(async {
+            tokio::time::timeout(Duration::from_secs(5), async {
+                let mut client = irtt_client::AsyncClient::connect(config(addr))
+                    .await
+                    .unwrap();
+                client.open().await.unwrap();
+                assert_eq!(
+                    client.negotiated_params().unwrap().params.dscp,
+                    if allowed { 184 } else { 0 }
+                );
+                for _ in 0..PROBES {
+                    let before = SystemTime::now();
+                    client.send_probe().await.unwrap();
+                    let events = client.recv().await.unwrap();
+                    assert_eq!(events.len(), 1);
+                    assert_kernel_send_endpoint(&events[0], before);
+                }
+                client.close().await.unwrap();
+            })
+            .await
+            .expect("async transport observations timed out");
+        });
+        let markings = peer.join().unwrap();
+        assert_eq!(markings[0], 0);
+        assert_eq!(
+            &markings[1..=PROBES],
+            vec![if allowed { 184 } else { 0 }; PROBES]
+        );
+        assert_eq!(markings[PROBES + 1], 0);
+    }
+}
+
+// Real ICMP refusal remains a socket error, never optional timestamp metadata.
+// The bound peer closes only after the client has accepted a valid OPEN.
+#[test]
+fn a_closed_udp_peer_surfaces_a_socket_error() {
+    let socket = UdpSocket::bind("127.0.0.1:0").unwrap();
+    let addr = socket.local_addr().unwrap();
+    socket
+        .set_read_timeout(Some(Duration::from_secs(3)))
+        .unwrap();
+    let (close_tx, close_rx) = mpsc::channel();
+    let task = thread::spawn(move || {
+        let mut core = ServerCore::new(ServerConfig::default());
+        let mut bytes = [0; 2048];
+        let (size, source) = socket.recv_from(&mut bytes).unwrap();
+        assert!(matches!(
+            decode_request(&bytes[..size]).unwrap().kind,
+            DecodedRequestKind::Open { .. }
+        ));
+        let reply = core
+            .handle_datagram(source, &bytes[..size])
+            .unwrap()
+            .unwrap();
+        socket.send_to(reply.bytes(), source).unwrap();
+        close_rx.recv_timeout(Duration::from_secs(3)).unwrap();
+        drop(socket);
+    });
+    let mut client = Client::connect(config(addr)).unwrap();
+    client.open().unwrap();
+    close_tx.send(()).unwrap();
+    task.join().unwrap();
+    // Refusal can arrive during send's TX drain or the following receive.
+    let result = client.send_probe().and_then(|_| client.recv_once());
+    assert!(
+        matches!(result, Err(irtt_client::ClientError::Socket(ref error))
+        if error.kind() == std::io::ErrorKind::ConnectionRefused),
+        "{result:?}"
+    );
+}