fix(quinn-proto): prevent O(N^2) behaviour when sending a lot of small values in SendBuffer

quinn-proto/Cargo.toml

@@ -35,6 +35,7 @@ tracing-log = ["tracing/log"]
 rustls-log = ["rustls?/logging"]
 # Enable qlog support
 qlog = ["dep:qlog"]
+bench = ["dep:bencher"]
 
 # Internal (PRIVATE!) features used to aid testing.
 # Don't rely on these whatsoever. They may disappear at any time.
@@ -44,6 +45,7 @@ __rustls-post-quantum-test =  []
 [dependencies]
 arbitrary = { workspace = true, optional = true }
 aws-lc-rs = { workspace = true, optional = true }
+bencher = { workspace = true, optional = true }
 bytes = { workspace = true }
 fastbloom = { workspace = true, optional = true }
 identity-hash = { workspace = true }
@@ -82,6 +84,11 @@ wasm-bindgen-test = { workspace = true }
 proptest = { workspace = true }
 test-strategy = { workspace = true }
 
+[[bench]]
+name = "send_buffer"
+harness = false
+required-features = ["bench"]
+
 [lints.rust]
 # https://rust-fuzz.github.io/book/cargo-fuzz/guide.html#cfgfuzzing
 unexpected_cfgs = { level = "warn", check-cfg = ['cfg(fuzzing)'] }

quinn-proto/benches/send_buffer.rs

@@ -0,0 +1,8 @@
+use bencher::{benchmark_group, benchmark_main};
+use iroh_quinn_proto::bench_exports::send_buffer_benches::*;
+
+// Since we can't easily access test utilities, this is a minimal benchmark
+// that measures the actual problematic operations directly
+
+benchmark_group!(benches, get_into_many_segments, get_loop_many_segments,);
+benchmark_main!(benches);

quinn-proto/src/connection/mod.rs

@@ -73,8 +73,7 @@ pub use paths::{ClosedPath, PathEvent, PathId, PathStatus, RttEstimator, SetPath
 use paths::{PathData, PathState};
 
 pub(crate) mod qlog;
-
-mod send_buffer;
+pub(crate) mod send_buffer;
 
 mod spaces;
 #[cfg(fuzzing)]