Fix ACK frequency extension corner case

.github/workflows/rust.yml

@@ -58,7 +58,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@1.63.0
+      - uses: dtolnay/rust-toolchain@1.65.0
       - uses: Swatinem/rust-cache@v2
       - run: cargo check --lib --all-features -p quinn-udp -p quinn-proto -p quinn
 

README.md

@@ -20,7 +20,7 @@ Quinn is a pure-rust, async-compatible implementation of the IETF [QUIC][quic] t
   [rustls][rustls] and [*ring*][ring]
 - Application-layer datagrams for small, unreliable messages
 - Future-based async API
-- Minimum supported Rust version of 1.63.0
+- Minimum supported Rust version of 1.65.0
 
 ## Overview
 

bench/Cargo.toml

@@ -2,7 +2,6 @@
 name = "bench"
 version = "0.1.0"
 edition = "2021"
-rust-version = "1.63"
 license = "MIT OR Apache-2.0"
 publish = false
 

perf/Cargo.toml

@@ -2,7 +2,6 @@
 name = "perf"
 version = "0.1.0"
 edition = "2021"
-rust-version = "1.63"
 license = "MIT OR Apache-2.0"
 publish = false
 

quinn-proto/Cargo.toml

@@ -2,7 +2,7 @@
 name = "quinn-proto"
 version = "0.11.0"
 edition = "2021"
-rust-version = "1.63"
+rust-version = "1.65"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/quinn-rs/quinn"
 description = "State machine for the QUIC transport protocol"

quinn-proto/src/connection/spaces.rs

@@ -631,18 +631,25 @@ impl PendingAcks {
                     || dedup.missing_in_interval(prev_largest_ack_eliciting, packet_number)
             }
             _ => {
-                // From acknowledgement frequency draft, section 6.1
-                if let Some((largest_acked, largest_unacked)) =
+                // From acknowledgement frequency draft, section 6.1: send an ACK immediately if
+                // doing so would cause the sender to detect a new packet loss
+                let Some((largest_acked, largest_unacked)) =
                     self.largest_acked.zip(self.largest_ack_eliciting_packet)
-                {
-                    dedup
-                        .smallest_missing_in_interval(largest_acked, largest_unacked)
-                        .map_or(false, |smallest_missing| {
-                            largest_unacked - smallest_missing >= self.reordering_threshold
-                        })
-                } else {
-                    false
+                else {
+                    return false;
+                };
+                if self.reordering_threshold > largest_acked {
+                    return false;
                 }
+                // The largest packet number that could be declared lost without a new ACK being
+                // sent
+                let largest_reported = largest_acked - self.reordering_threshold + 1;
+                let Some(smallest_missing_unreported) =
+                    dedup.smallest_missing_in_interval(largest_reported, largest_unacked)
+                else {
+                    return false;
+                };
+                largest_unacked - smallest_missing_unreported >= self.reordering_threshold
             }
         }
     }

quinn-udp/Cargo.toml

@@ -2,7 +2,7 @@
 name = "quinn-udp"
 version = "0.5.0"
 edition = "2021"
-rust-version = "1.63"
+rust-version = "1.65"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/quinn-rs/quinn"
 description = "UDP sockets with ECN information for the QUIC transport protocol"

quinn/Cargo.toml

@@ -9,7 +9,7 @@ keywords = ["quic"]
 categories = [ "network-programming", "asynchronous" ]
 workspace = ".."
 edition = "2021"
-rust-version = "1.63"
+rust-version = "1.65"
 
 [package.metadata.docs.rs]
 all-features = true