message: Remove unnecessary wakeups from UDP
diff: @@ -15,7 +15,6 @@ use tokio::{
  self,
  net::udp::{RecvHalf, SendHalf},
  sync::{mpsc, Mutex},
  - time,
  };
  use crate::{
  @@ -330,16 +329,7 @@ async fn listen(context: SharedContext, flow_stat: SharedServerFlowStatistic, sv
  let mut pkt_buf = vec![0u8; MAXIMUM_UDP_PAYLOAD_SIZE];
  loop {
  - let (recv_len, src) = match time::timeout(timeout, r.recv_from(&mut pkt_buf)).await {
  - Ok(r) => r?,
  - Err(..) => {
  - // Cleanup expired association
  - // Do not consume this iterator, it will updates expire time of items that traversed
  - let mut assoc_map = assoc_map.lock().await;
  - let _ = assoc_map.iter();
  - continue;
  - }
  - };
  + let (recv_len, src) = r.recv_from(&mut pkt_buf).await?;
  // Packet length is limited by MAXIMUM_UDP_PAYLOAD_SIZE, excess bytes will be discarded.
  let pkt = &pkt_buf[..recv_len];
  