From 20e628627752cee2511ee9179e0217a1a2a07fd0 Mon Sep 17 00:00:00 2001
From: Nils Andreas Svee <me@lochnair.net>
Date: Fri, 8 May 2026 10:47:14 +0700
Subject: [PATCH] fix(client): report counter overflows clearly

---
 crates/irtt-client/src/client.rs              | 22 +++++---
 .../src/client/tests/probes_replies.rs        | 50 ++++++++++++++++++-
 crates/irtt-client/src/error.rs               |  2 +
 3 files changed, 65 insertions(+), 9 deletions(-)

diff --git a/crates/irtt-client/src/client.rs b/crates/irtt-client/src/client.rs
index f28428a..54bdbc1 100644
--- a/crates/irtt-client/src/client.rs
+++ b/crates/irtt-client/src/client.rs
@@ -241,14 +241,20 @@ impl Client {
         session.pending.insert(pending)?;
 
         session.next_wire_seq = session.next_wire_seq.wrapping_add(1);
-        session.next_logical_seq = session
-            .next_logical_seq
-            .checked_add(1)
-            .ok_or(ClientError::DurationOverflow)?;
-        session.packets_sent = session
-            .packets_sent
-            .checked_add(1)
-            .ok_or(ClientError::DurationOverflow)?;
+        session.next_logical_seq =
+            session
+                .next_logical_seq
+                .checked_add(1)
+                .ok_or(ClientError::CounterOverflow {
+                    counter: "next_logical_seq",
+                })?;
+        session.packets_sent =
+            session
+                .packets_sent
+                .checked_add(1)
+                .ok_or(ClientError::CounterOverflow {
+                    counter: "packets_sent",
+                })?;
 
         let negotiated = self
             .negotiated
diff --git a/crates/irtt-client/src/client/tests/probes_replies.rs b/crates/irtt-client/src/client/tests/probes_replies.rs
index 239a47a..bfa7232 100644
--- a/crates/irtt-client/src/client/tests/probes_replies.rs
+++ b/crates/irtt-client/src/client/tests/probes_replies.rs
@@ -302,7 +302,7 @@ fn send_probe_reports_schedule_overflow() {
     };
     let mut client = Client::connect(config).unwrap();
     assert_open_started(client.open(ClientTimestamp::now()).unwrap());
-    client.session.as_mut().unwrap().packets_sent = u64::MAX;
+    client.session.as_mut().unwrap().packets_sent = u64::MAX - 1;
 
     assert!(matches!(
         client.send_probe(),
@@ -311,6 +311,54 @@ fn send_probe_reports_schedule_overflow() {
     server.join();
 }
 
+#[test]
+fn send_probe_reports_logical_sequence_counter_overflow() {
+    let params = default_params();
+    let server = silent_open_server(params);
+    let config = ClientConfig {
+        socket_config: crate::SocketConfig {
+            recv_timeout: Some(Duration::from_millis(200)),
+            ..Default::default()
+        },
+        ..default_test_config(server.addr)
+    };
+    let mut client = Client::connect(config).unwrap();
+    assert_open_started(client.open(ClientTimestamp::now()).unwrap());
+    client.session.as_mut().unwrap().next_logical_seq = u64::MAX;
+
+    assert!(matches!(
+        client.send_probe(),
+        Err(ClientError::CounterOverflow {
+            counter: "next_logical_seq"
+        })
+    ));
+    server.join();
+}
+
+#[test]
+fn send_probe_reports_packets_sent_counter_overflow() {
+    let params = default_params();
+    let server = silent_open_server(params);
+    let config = ClientConfig {
+        socket_config: crate::SocketConfig {
+            recv_timeout: Some(Duration::from_millis(200)),
+            ..Default::default()
+        },
+        ..default_test_config(server.addr)
+    };
+    let mut client = Client::connect(config).unwrap();
+    assert_open_started(client.open(ClientTimestamp::now()).unwrap());
+    client.session.as_mut().unwrap().packets_sent = u64::MAX;
+
+    assert!(matches!(
+        client.send_probe(),
+        Err(ClientError::CounterOverflow {
+            counter: "packets_sent"
+        })
+    ));
+    server.join();
+}
+
 #[test]
 fn recv_once_returns_empty_on_timeout() {
     let params = default_params();
diff --git a/crates/irtt-client/src/error.rs b/crates/irtt-client/src/error.rs
index 9c5179e..584b153 100644
--- a/crates/irtt-client/src/error.rs
+++ b/crates/irtt-client/src/error.rs
@@ -49,6 +49,8 @@ pub enum ClientError {
     AlreadyClosed,
     #[error("duration is too large to encode as nanoseconds")]
     DurationOverflow,
+    #[error("counter {counter} overflowed")]
+    CounterOverflow { counter: &'static str },
     #[error("pending probe limit exceeded ({limit})")]
     PendingLimitExceeded { limit: usize },
     #[error("invalid configuration: {reason}")]