From b5902da5a95e863dfad7e1d15afaef07fc6fba0a Mon Sep 17 00:00:00 2001
From: Max Inden <mail@max-inden.de>
Date: Wed, 23 Oct 2024 12:26:36 +0200
Subject: [PATCH] fix(udp/bench): enforce max 64k UDP datagram limit

Linux drops UDP datagrams larger than 64k, even when segmented. In other words,
64k - headers is the maximum GSO payload size.
---
 quinn-udp/benches/throughput.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/quinn-udp/benches/throughput.rs b/quinn-udp/benches/throughput.rs
index 1ba2db1a9..46385d73a 100644
--- a/quinn-udp/benches/throughput.rs
+++ b/quinn-udp/benches/throughput.rs
@@ -1,4 +1,5 @@
 use std::{
+    cmp::min,
     io::{ErrorKind, IoSliceMut},
     net::{Ipv4Addr, Ipv6Addr, UdpSocket},
 };
@@ -51,7 +52,7 @@ pub fn criterion_benchmark(c: &mut Criterion) {
         } else {
             1
         };
-        let msg = vec![0xAB; SEGMENT_SIZE * gso_segments];
+        let msg = vec![0xAB; min(MAX_DATAGRAM_SIZE, SEGMENT_SIZE * gso_segments)];
         let transmit = Transmit {
             destination: dst_addr,
             ecn: None,
@@ -117,3 +118,6 @@ fn new_socket() -> (UdpSocketState, tokio::net::UdpSocket) {
 
 criterion_group!(benches, criterion_benchmark);
 criterion_main!(benches);
+
+const MAX_IP_UDP_HEADER_SIZE: usize = 48;
+const MAX_DATAGRAM_SIZE: usize = u16::MAX as usize - MAX_IP_UDP_HEADER_SIZE;