Merge pull request #3392 from sysown/v2.1.1-3342

Closes #3342: ProxySQL reset connection if it starts with COM_QUIT

lib/MySQL_Thread.cpp

@@ -5245,6 +5245,12 @@ void MySQL_Thread::listener_handle_new_connection(MySQL_Data_Stream *myds, unsig
  ioctl_FIONBIO(sess->client_myds->fd, 1);
  mypolls.add(POLLIN|POLLOUT, sess->client_myds->fd, sess->client_myds, curtime);
  proxy_debug(PROXY_DEBUG_NET,1,"Session=%p -- Adding client FD %d\n", sess, sess->client_myds->fd);
+
+ // we now enforce sending the 'initial handshake packet' as soon as it's generated. This
+ // is done to prevent situations in which a client sends a packet *before* receiving
+ // this 'initial handshake', leading to invalid state in dataflow, since it will be
+ // data in both ends of the datastream. For more details see #3342.
+ sess->writeout();
  } else {
  free(addr);
  // if we arrive here, accept() failed