Revert "bring back buffering"

This reverts commit ada3005.

Author: matheus23

quinn/src/connection.rs

@@ -900,7 +900,6 @@ impl ConnectionRef {
                 udp_sender: sender,
                 runtime,
                 send_buffer: Vec::new(),
-                buffered_transmit: None,
                 observed_external_addr: watch::Sender::new(None),
             }),
             shared: Shared::default(),
@@ -1019,8 +1018,6 @@ pub(crate) struct State {
     udp_sender: Pin<Box<dyn UdpSender>>,
     runtime: Arc<dyn Runtime>,
     send_buffer: Vec<u8>,
-    /// We buffer a transmit when the underlying I/O would block
-    buffered_transmit: Option<proto::Transmit>,
     /// Our last external address reported by the peer.
     pub(crate) observed_external_addr: watch::Sender<Option<SocketAddr>>,
 }
@@ -1033,26 +1030,18 @@ impl State {
         let max_datagrams = self.udp_sender.max_transmit_segments();
 
         loop {
-            // Retry the last transmit, or get a new one.
-            let t = match self.buffered_transmit.take() {
-                Some(t) => t,
-                None => {
-                    self.send_buffer.clear();
-                    self.send_buffer.reserve(self.inner.current_mtu() as usize);
-                    match self
-                        .inner
-                        .poll_transmit(now, max_datagrams, &mut self.send_buffer)
-                    {
-                        Some(t) => {
-                            transmits += match t.segment_size {
-                                None => 1,
-                                Some(s) => (t.size + s - 1) / s, // round up
-                            };
-                            t
-                        }
-                        None => break,
-                    }
-                }
+            self.send_buffer.clear();
+            self.send_buffer.reserve(self.inner.current_mtu() as usize);
+            let Some(t) = self
+                .inner
+                .poll_transmit(now, max_datagrams, &mut self.send_buffer)
+            else {
+                break;
+            };
+
+            transmits += match t.segment_size {
+                None => 1,
+                Some(s) => (t.size + s - 1) / s, // round up
             };
 
             let len = t.size;
@@ -1062,10 +1051,7 @@ impl State {
                 .as_mut()
                 .poll_send(&udp_transmit(&t, &self.send_buffer[..len]), cx)
             {
-                Poll::Pending => {
-                    self.buffered_transmit = Some(t);
-                    return Ok(false);
-                }
+                Poll::Pending => return Ok(true),
                 Poll::Ready(result) => result?, // propagate errors
             }