code: func (p *Position) IsSubnetRouterAnycast() bool {
  	return !p.IP.IsUnspecified() && !p.IP.IsLoopback() && !p.IP.IsMulticast() && p.IP.To16() != nil && p.IP.To4() == nil && p.IP.Equal(p.Prefix.IP)
  }
docs: // IsSubnetRouterAnycast reports whether p is an IPv6 subnet router
  // anycast address.