code: func (m *InjectableEndpoint) WritePacket(r *stack.Route, _ *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
  	if endpoint, ok := m.routes[r.RemoteAddress]; ok {
  		return endpoint.WritePacket(r, nil /* gso */, hdr, payload, protocol)
  	}
  	return tcpip.ErrNoRoute
  }
docs: // WritePacket writes outbound packets to the appropriate LinkInjectableEndpoint
  // based on the RemoteAddress. HandleLocal only works if r.RemoteAddress has a
  // route registered in this endpoint.