//   The IANA has assigned the FC00::/7 prefix to "Unique Local Unicast".
	return len(ip) == IPv6len && ip[0]&0xfe == 0xfc
}

// IsMulticast reports whether ip is a multicast address.
func (ip IP) IsMulticast() bool {
	if ip4 := ip.To4(); ip4 != nil {
		return ip4[0]&0xf0 == 0xe0
	}
	return len(ip) == IPv6len && ip[0] == 0xff
}

// IsInterfaceLocalMulticast reports whether ip is

	testHookUninstaller.Do(uninstallTestHooks)

	b.Run("IPv4", func(b *testing.B) {
		benchmarkIPString(b, IPv4len)
	})

	b.Run("IPv6", func(b *testing.B) {
		benchmarkIPString(b, IPv6len)
	})
}

func benchmarkIPString(b *testing.B, size int) {
	b.ReportAllocs()
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		for _, tt := range ipStringTests {
			if tt.in != nil && len(tt.in) == size {

						}, c.PermittedURIDomains, c.ExcludedURIDomains); err != nil {
						return err
					}

				case nameTypeIP:
					ip := net.IP(data)
					if l := len(ip); l != net.IPv4len && l != net.IPv6len {
						return fmt.Errorf("x509: internal error: IP SAN %x failed to parse", data)
					}

					if err := c.checkNameConstraints(&comparisonCount, maxConstraintComparisons, "IP address", ip.String(), ip,

					return fmt.Errorf("x509: cannot parse URI %q: invalid domain", uriStr)
				}
			}
			uris = append(uris, uri)
		case nameTypeIP:
			switch len(data) {
			case net.IPv4len, net.IPv6len:
				ipAddresses = append(ipAddresses, data)
			default:
				return errors.New("x509: cannot parse IP address of length " + strconv.Itoa(len(data)))
			}
		}

		return nil
	})

	return
}

	if err != nil {
		return nil, []error{errors.Wrapf(err, "unable to get first IP address from the given CIDR (%s)", cidr.String())}
	}

	testIPstring := testIP.String()
	if len(testIP) == net.IPv6len {
		testIPstring = fmt.Sprintf("[%s]:1234", testIP)
	}
	url := fmt.Sprintf("%s://%s/", subnet.Proto, testIPstring)

	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return nil, []error{err}