code: func (v *vserver) expandDests(svc *service) map[destinationKey]*destination {
  	dsts := make(map[destinationKey]*destination, len(v.config.Backends))
  	for _, backend := range v.config.Backends {
  		var ip net.IP
  		switch svc.af {
  		case seesaw.IPv4:
  			ip = backend.Host.IPv4Addr
  		case seesaw.IPv6:
  			ip = backend.Host.IPv6Addr
  		}
  		if ip == nil {
  			continue
  		}
  		dst := &destination{
  			destinationKey: newDestinationKey(ip),
  			service:        svc,
  			backend:        backend,
  			weight:         backend.Weight,
  		}
  		dst.ipvsDst = dst.ipvsDestination()
  		dst.stats = &seesaw.DestinationStats{}
  		dsts[dst.destinationKey] = dst
  	}
  	return dsts
  }
docs: // expandDests returns a list of destinations that have been expanded from the
  // vserver configuration and a given service.