code: func (ep *endpoint) saveRcvBufSizeMax() int {
  	max := ep.rcvBufSizeMax
  	// Make sure no new packets will be handled regardless of the lock.
  	ep.rcvBufSizeMax = 0
  	// Release the lock acquired in beforeSave() so regular endpoint closing
  	// logic can proceed after save.
  	ep.rcvMu.Unlock()
  	return max
  }
docs: // saveRcvBufSizeMax is invoked by stateify.