[fix] the unit test gso_truncation

quinn-proto/src/connection/mod.rs

@@ -698,6 +698,7 @@ impl Connection {
                                 "GSO truncated by demand for {} padding bytes",
                                 segment_size - packet_len_unpadded
                             );
+                            builder_storage = Some(builder);
                             break;
                         }
 

quinn-proto/src/tests/mod.rs

@@ -3047,20 +3047,30 @@ fn datagram_gso() {
 fn gso_truncation() {
     let _guard = subscribe();
     let mut pair = Pair::default();
-    let (client_ch, _) = pair.connect();
+    let (client_ch, server_ch) = pair.connect();
 
     let initial_ios = pair.client_conn_mut(client_ch).stats().udp_tx.ios;
 
     // Send three application datagrams such that each is large to be combined with another in a
     // single MTU, and the second datagram would require an unreasonably large amount of padding to
     // produce a QUIC packet of the same length as the first.
     info!("sending");
-    for len in [1024, 768, 768] {
+    const SIZES: [usize; 3] = [1024, 768, 768];
+    for len in SIZES {
         pair.client_datagrams(client_ch)
             .send(vec![0; len].into(), false)
             .unwrap();
     }
     pair.drive();
     let final_ios = pair.client_conn_mut(client_ch).stats().udp_tx.ios;
     assert_eq!(final_ios - initial_ios, 2);
+    for len in SIZES {
+        assert_eq!(
+            pair.server_datagrams(server_ch)
+                .recv()
+                .expect("datagram lost")
+                .len(),
+            len
+        );
+    }
 }