fix(client): avoid lossy timing casts

crates/irtt-client/src/client.rs

@@ -1,7 +1,7 @@
 use std::{
     io,
     net::{SocketAddr, UdpSocket},
-    time::{Duration, Instant},
+    time::{Duration, Instant, SystemTime, UNIX_EPOCH},
 };
 
 use irtt_proto::{
@@ -260,7 +260,8 @@ impl Client {
             .negotiated
             .as_ref()
             .expect("negotiated must exist when Open");
-        let interval_ns = negotiated.params.interval_ns as u64;
+        let interval_ns = u64::try_from(negotiated.params.interval_ns)
+            .expect("validated positive negotiated interval");
         let session = self
             .session
             .as_mut()
@@ -817,16 +818,8 @@ fn compute_one_way(
     let server_recv_wall = ts.recv_wall.or(ts.midpoint_wall);
     let server_send_wall = ts.send_wall.or(ts.midpoint_wall);
 
-    let client_send_ns = sent_at
-        .wall
-        .duration_since(std::time::UNIX_EPOCH)
-        .ok()
-        .map(|d| d.as_nanos() as i64);
-    let client_recv_ns = received_at
-        .wall
-        .duration_since(std::time::UNIX_EPOCH)
-        .ok()
-        .map(|d| d.as_nanos() as i64);
+    let client_send_ns = unix_epoch_ns_i64(sent_at.wall);
+    let client_recv_ns = unix_epoch_ns_i64(received_at.wall);
 
     let c2s = server_recv_wall
         .zip(client_send_ns)
@@ -847,6 +840,12 @@ fn compute_one_way(
     })
 }
 
+fn unix_epoch_ns_i64(time: SystemTime) -> Option<i64> {
+    time.duration_since(UNIX_EPOCH)
+        .ok()
+        .and_then(|duration| i64::try_from(duration.as_nanos()).ok())
+}
+
 fn build_received_stats(reply: &EchoReply) -> Option<ReceivedStatsSample> {
     if reply.recv_count.is_none() && reply.recv_window.is_none() {
         return None;
@@ -922,8 +921,9 @@ fn config_duration_to_ns(field: &str, duration: Duration) -> Result<i64, ClientE
 
 fn negotiated_end_mono(start: Instant, duration_ns: i64) -> Result<Instant, ClientError> {
     debug_assert!(duration_ns > 0);
+    let duration_ns = u64::try_from(duration_ns).expect("validated positive negotiated duration");
     start
-        .checked_add(Duration::from_nanos(duration_ns as u64))
+        .checked_add(Duration::from_nanos(duration_ns))
         .ok_or_else(|| ClientError::NegotiationRejected {
             reason: "duration is too large to schedule".to_owned(),
         })

crates/irtt-client/src/client/tests/config.rs

@@ -112,8 +112,9 @@ fn params_from_config_rejects_zero_interval() {
 
 #[test]
 fn params_from_config_rejects_nanosecond_encoding_overflow_as_invalid_config() {
+    let i64_max_ns = u64::try_from(i64::MAX).unwrap();
     let config = ClientConfig {
-        duration: Some(Duration::from_nanos(i64::MAX as u64) + Duration::from_nanos(1)),
+        duration: Some(Duration::from_nanos(i64_max_ns) + Duration::from_nanos(1)),
         ..ClientConfig::default()
     };
     assert!(matches!(
@@ -123,7 +124,7 @@ fn params_from_config_rejects_nanosecond_encoding_overflow_as_invalid_config() {
     ));
 
     let config = ClientConfig {
-        interval: Duration::from_nanos(i64::MAX as u64) + Duration::from_nanos(1),
+        interval: Duration::from_nanos(i64_max_ns) + Duration::from_nanos(1),
         ..ClientConfig::default()
     };
     assert!(matches!(

crates/irtt-client/src/client/tests/probes_replies.rs

@@ -1479,6 +1479,38 @@ fn compute_one_way_returns_none_when_both_directions_fail() {
     assert!(result.is_none());
 }
 
+#[test]
+fn unix_epoch_ns_i64_rejects_out_of_range_wall_time() {
+    let i64_max_ns = u64::try_from(i64::MAX).unwrap();
+    let max = SystemTime::UNIX_EPOCH + Duration::from_nanos(i64_max_ns);
+    let overflow = max + Duration::from_nanos(1);
+
+    assert_eq!(unix_epoch_ns_i64(max), Some(i64::MAX));
+    assert_eq!(unix_epoch_ns_i64(overflow), None);
+}
+
+#[test]
+fn compute_one_way_omits_samples_when_client_wall_time_overflows_i64() {
+    let i64_max_ns = u64::try_from(i64::MAX).unwrap();
+    let overflow_wall =
+        SystemTime::UNIX_EPOCH + Duration::from_nanos(i64_max_ns) + Duration::from_nanos(1);
+    let sent_at = ClientTimestamp {
+        mono: Instant::now(),
+        wall: overflow_wall,
+    };
+    let received_at = ClientTimestamp {
+        mono: sent_at.mono + Duration::from_millis(40),
+        wall: overflow_wall + Duration::from_millis(40),
+    };
+    let ts = TimestampFields {
+        recv_wall: Some(i64::MAX),
+        send_wall: Some(i64::MAX),
+        ..Default::default()
+    };
+
+    assert_eq!(compute_one_way(&sent_at, &received_at, &ts), None);
+}
+
 #[test]
 fn matched_reply_with_reversed_monotonic_time_still_emits_event() {
     let params = default_params();

crates/irtt-client/src/managed/runner.rs

@@ -343,8 +343,8 @@ mod tests {
     fn test_params(duration: Option<Duration>, interval: Duration) -> Params {
         Params {
             protocol_version: PROTOCOL_VERSION,
-            duration_ns: duration.map_or(0, |d| d.as_nanos() as i64),
-            interval_ns: interval.as_nanos() as i64,
+            duration_ns: duration.map_or(0, test_duration_ns_i64),
+            interval_ns: test_duration_ns_i64(interval),
             length: 0,
             received_stats: ReceivedStats::Both,
             stamp_at: StampAt::Both,
@@ -354,6 +354,10 @@ mod tests {
         }
     }
 
+    fn test_duration_ns_i64(duration: Duration) -> i64 {
+        i64::try_from(duration.as_nanos()).expect("test duration fits i64 nanoseconds")
+    }
+
     fn config(addr: SocketAddr, duration: Option<Duration>) -> ClientConfig {
         ClientConfig {
             server_addr: addr.to_string(),