code: func (h *sentPacketHistory) readjustFirstOutstanding() {
  	el := h.firstOutstanding.Next()
  	for el != nil && !el.Value.canBeRetransmitted {
  		el = el.Next()
  	}
  	h.firstOutstanding = el
  }
docs: // readjustFirstOutstanding readjusts the pointer to the first outstanding packet.
  // This is necessary every time the first outstanding packet is deleted or retransmitted.