net/ip.go
func (n Network) Contains(nn NetworkNumber) bool {
	if len(n.Mask) != len(nn) {
		return false
	}
	if nn[0]&n.Mask[0] != n.Number[0] {
		return false
	}
	if len(nn) == IPv6Uint32Count {
		return nn[1]&n.Mask[1] == n.Number[1] && nn[2]&n.Mask[2] == n.Number[2] && nn[3]&n.Mask[3] == n.Number[3]
	}
	return true
}
func (n Network) Contains(nn NetworkNumber) bool {
	if len(n.Mask) != len(nn) {
		return false
	}
	if nn[0]&n.Mask[0] != n.Number[0] {
		return false
	}
	if len(nn) == IPv6Uint32Count {
		return nn[1]&n.Mask[1] == n.Number[1] && nn[2]&n.Mask[2] == n.Number[2] && nn[3]&n.Mask[3] == n.Number[3]
	}
	return true
}
// Contains returns true if NetworkNumber is in range of Network, false
// otherwise.