From 548363ad055e3f2ba92d8d16e2198428a5532854 Mon Sep 17 00:00:00 2001
From: Nils Andreas Svee <me@lochnair.net>
Date: Tue, 28 Apr 2026 21:52:04 +0700
Subject: [PATCH] fix(client): improve probe tracking and reply handling

---
 crates/irtt-client/src/client.rs | 18 +++++++++++++-----
 crates/irtt-client/src/probe.rs  |  7 ++++++-
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/crates/irtt-client/src/client.rs b/crates/irtt-client/src/client.rs
index db49dc7..f0b030e 100644
--- a/crates/irtt-client/src/client.rs
+++ b/crates/irtt-client/src/client.rs
@@ -173,6 +173,8 @@ impl Client {
             }
         }
 
+        session.pending.check_capacity()?;
+
         let negotiated = self
             .negotiated
             .as_ref()
@@ -230,7 +232,7 @@ impl Client {
         Ok(vec![])
     }
 
-    pub fn recv_once(&mut self, now: ClientTimestamp) -> Result<Vec<ClientEvent>, ClientError> {
+    pub fn recv_once(&mut self) -> Result<Vec<ClientEvent>, ClientError> {
         match self.phase {
             ClientPhase::Open { .. } => {}
             ClientPhase::Closed => return Err(ClientError::AlreadyClosed),
@@ -394,13 +396,13 @@ impl Client {
                 remote: self.remote,
                 received_at: now,
             }])
-        } else {
-            let highest_seen = session.highest_received_seq.unwrap_or(wire_seq);
-            update_highest_received(session, wire_seq);
+        } else if session.highest_received_seq.is_some_and(|h| wire_seq < h) {
+            // TODO: u32 ordering is acceptable for finite tests but continuous
+            // probing will eventually require wrap-aware comparison.
             Ok(vec![ClientEvent::LateReply {
                 seq: wire_seq,
                 logical_seq: None,
-                highest_seen,
+                highest_seen: session.highest_received_seq.unwrap(),
                 remote: self.remote,
                 sent_at: None,
                 received_at: now,
@@ -410,6 +412,12 @@ impl Client {
                 received_stats: build_received_stats(&reply),
                 packet_meta: PacketMeta::default(),
             }])
+        } else {
+            Ok(vec![ClientEvent::Warning {
+                message: format!(
+                    "dropped reply with untracked seq {wire_seq} (no pending or completed entry)"
+                ),
+            }])
         }
     }
 
diff --git a/crates/irtt-client/src/probe.rs b/crates/irtt-client/src/probe.rs
index 5a520ce..c0fd246 100644
--- a/crates/irtt-client/src/probe.rs
+++ b/crates/irtt-client/src/probe.rs
@@ -24,12 +24,17 @@ impl PendingMap {
         }
     }
 
-    pub fn insert(&mut self, probe: PendingProbe) -> Result<(), ClientError> {
+    pub fn check_capacity(&self) -> Result<(), ClientError> {
         if self.map.len() >= self.max_capacity {
             return Err(ClientError::PendingLimitExceeded {
                 limit: self.max_capacity,
             });
         }
+        Ok(())
+    }
+
+    pub fn insert(&mut self, probe: PendingProbe) -> Result<(), ClientError> {
+        self.check_capacity()?;
         self.map.insert(probe.wire_seq, probe);
         Ok(())
     }