message: set TFO queue length to 1024 in Linux for matching backlogs
diff: @@ -316,7 +316,15 @@ impl AsyncWrite for TcpStream {
  ///
  /// `TCP_FASTOPEN` was supported since Linux 3.7
  pub fn set_tcp_fastopen<S: AsRawFd>(socket: &S) -> io::Result<()> {
  - let queue: libc::c_int = 5;
  + // https://lwn.net/Articles/508865/
  + //
  + // The option value, qlen, specifies this server's limit on the size of the queue of TFO requests that have
  + // not yet completed the three-way handshake (see the remarks on prevention of resource-exhaustion attacks above).
  + //
  + // It was recommended to be `5` in this document.
  + //
  + // But since mio's TcpListener sets backlogs to 1024, it would be nice to have 1024 slots for handshaking TFO requests.
  + let queue: libc::c_int = 1024;
  unsafe {
  let ret = libc::setsockopt(
  