code: func (s *PortManager) reserveSpecificPort(networks []tcpip.NetworkProtocolNumber, transport tcpip.TransportProtocolNumber, addr tcpip.Address, port uint16, reuse bool) bool {
  	if !s.isPortAvailableLocked(networks, transport, addr, port, reuse) {
  		return false
  	}
  
  	// Reserve port on all network protocols.
  	for _, network := range networks {
  		desc := portDescriptor{network, transport, port}
  		m, ok := s.allocatedPorts[desc]
  		if !ok {
  			m = make(bindAddresses)
  			s.allocatedPorts[desc] = m
  		}
  		if n, ok := m[addr]; ok {
  			n.refs++
  			m[addr] = n
  		} else {
  			m[addr] = portNode{reuse: reuse, refs: 1}
  		}
  	}
  
  	return true
  }
docs: // reserveSpecificPort tries to reserve the given port on all given protocols.