feat(cli): add multi-target probing support and labels

Enable concurrent probing of multiple targets using positional arguments or the `--target` flag with unique labels. Update output formats to include a `target` column for logical attribution in multi-target runs.

crates/irtt-cli/tests/client_multi_target.rs

@@ -0,0 +1,189 @@
+#![cfg(feature = "client")]
+
+use std::{
+    net::{SocketAddr, UdpSocket},
+    process::Command,
+    thread,
+    thread::JoinHandle,
+    time::Duration,
+};
+
+use irtt_proto::{
+    echo_packet_len,
+    flags::{FLAG_CLOSE, FLAG_OPEN, FLAG_REPLY},
+    layout::PacketLayout,
+    Clock, Params, ReceivedStats, StampAt, TimestampFields, MAGIC, PROTOCOL_VERSION,
+};
+
+const TOKEN: u64 = 0x1234_5678_90ab_cdef;
+
+struct FakeServer {
+    addr: SocketAddr,
+    done: JoinHandle<()>,
+}
+
+impl FakeServer {
+    fn join(self) {
+        self.done.join().unwrap();
+    }
+}
+
+#[test]
+fn multi_target_csv_emits_rows_for_both_labels() {
+    let params = test_params(Some(Duration::from_millis(40)), Duration::from_millis(10));
+    let a = start_echo_server(params.clone());
+    let b = start_echo_server(params);
+
+    let output = Command::new(env!("CARGO_BIN_EXE_irtt-cli"))
+        .args([
+            "--duration",
+            "40ms",
+            "--interval",
+            "10ms",
+            "--format",
+            "csv",
+            "--columns",
+            "target,seq,effective_rtt_us",
+            "--header",
+            "never",
+            "--target",
+            &format!("a={}", a.addr),
+            "--target",
+            &format!("b={}", b.addr),
+        ])
+        .output()
+        .unwrap();
+
+    a.join();
+    b.join();
+
+    assert!(
+        output.status.success(),
+        "status={:?}\nstderr={}",
+        output.status.code(),
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let stdout = String::from_utf8(output.stdout).unwrap();
+    assert!(
+        stdout.lines().any(|line| line.starts_with("a,")),
+        "{stdout}"
+    );
+    assert!(
+        stdout.lines().any(|line| line.starts_with("b,")),
+        "{stdout}"
+    );
+}
+
+fn start_echo_server(params: Params) -> FakeServer {
+    let socket = UdpSocket::bind("127.0.0.1:0").unwrap();
+    socket
+        .set_read_timeout(Some(Duration::from_secs(2)))
+        .unwrap();
+    let addr = socket.local_addr().unwrap();
+    let done = thread::spawn(move || {
+        let (_, peer) = recv_request(&socket);
+        socket
+            .send_to(&open_reply(FLAG_OPEN | FLAG_REPLY, TOKEN, &params), peer)
+            .unwrap();
+
+        loop {
+            let (packet, peer) = recv_request(&socket);
+            let flags = packet[3];
+            if flags & FLAG_CLOSE != 0 {
+                break;
+            }
+            let seq = u32::from_le_bytes(packet[12..16].try_into().unwrap());
+            socket
+                .send_to(
+                    &echo_reply_packet(
+                        TOKEN,
+                        seq,
+                        &params,
+                        &TimestampFields::default(),
+                        FLAG_REPLY,
+                    ),
+                    peer,
+                )
+                .unwrap();
+        }
+    });
+    FakeServer { addr, done }
+}
+
+fn recv_request(socket: &UdpSocket) -> (Vec<u8>, SocketAddr) {
+    let mut buf = [0_u8; 2048];
+    let (size, peer) = socket.recv_from(&mut buf).unwrap();
+    (buf[..size].to_vec(), peer)
+}
+
+fn open_reply(flags: u8, token: u64, params: &Params) -> Vec<u8> {
+    let mut packet = Vec::new();
+    packet.extend_from_slice(&MAGIC);
+    packet.push(flags);
+    packet.extend_from_slice(&token.to_le_bytes());
+    packet.extend_from_slice(&params.encode());
+    packet
+}
+
+fn echo_reply_packet(
+    token: u64,
+    seq: u32,
+    params: &Params,
+    timestamps: &TimestampFields,
+    flags: u8,
+) -> Vec<u8> {
+    let layout = PacketLayout::echo(false, params);
+    let packet_len = echo_packet_len(false, params).unwrap();
+    let mut packet = Vec::with_capacity(packet_len);
+
+    packet.extend_from_slice(&MAGIC);
+    packet.push(flags);
+    packet.extend_from_slice(&token.to_le_bytes());
+    packet.extend_from_slice(&seq.to_le_bytes());
+
+    if layout.recv_count {
+        packet.extend_from_slice(&42_u32.to_le_bytes());
+    }
+    if layout.recv_window {
+        packet.extend_from_slice(&0_u64.to_le_bytes());
+    }
+    if layout.recv_wall {
+        packet.extend_from_slice(&timestamps.recv_wall.unwrap_or(0).to_le_bytes());
+    }
+    if layout.recv_mono {
+        packet.extend_from_slice(&timestamps.recv_mono.unwrap_or(0).to_le_bytes());
+    }
+    if layout.midpoint_wall {
+        packet.extend_from_slice(&timestamps.midpoint_wall.unwrap_or(0).to_le_bytes());
+    }
+    if layout.midpoint_mono {
+        packet.extend_from_slice(&timestamps.midpoint_mono.unwrap_or(0).to_le_bytes());
+    }
+    if layout.send_wall {
+        packet.extend_from_slice(&timestamps.send_wall.unwrap_or(0).to_le_bytes());
+    }
+    if layout.send_mono {
+        packet.extend_from_slice(&timestamps.send_mono.unwrap_or(0).to_le_bytes());
+    }
+
+    packet.resize(packet_len, 0);
+    packet
+}
+
+fn test_params(duration: Option<Duration>, interval: Duration) -> Params {
+    Params {
+        protocol_version: PROTOCOL_VERSION,
+        duration_ns: duration.map_or(0, duration_ns_i64),
+        interval_ns: duration_ns_i64(interval),
+        length: 0,
+        received_stats: ReceivedStats::Both,
+        stamp_at: StampAt::Both,
+        clock: Clock::Both,
+        dscp: 0,
+        server_fill: None,
+    }
+}
+
+fn duration_ns_i64(duration: Duration) -> i64 {
+    i64::try_from(duration.as_nanos()).unwrap()
+}