Class InetAddresses


  • @GwtIncompatible
    public final class InetAddresses
    extends Object
    Static utility methods pertaining to InetAddress instances.

    Important note: Unlike InetAddress.getByName(), the methods of this class never cause DNS services to be accessed. For this reason, you should prefer these methods as much as possible over their JDK equivalents whenever you are expecting to handle only IP address string literals -- there is no blocking DNS penalty for a malformed string.

    When dealing with Inet4Address and Inet6Address objects as byte arrays (vis. InetAddress.getAddress()) they are 4 and 16 bytes in length, respectively, and represent the address in network byte order.

    Examples of IP addresses and their byte representations:

    The IPv4 loopback address, "127.0.0.1".
    7f 00 00 01
    The IPv6 loopback address, "::1".
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01
    From the IPv6 reserved documentation prefix (2001:db8::/32), "2001:db8::1".
    20 01 0d b8 00 00 00 00 00 00 00 00 00 00 00 01
    An IPv6 "IPv4 compatible" (or "compat") address, "::192.168.0.1".
    00 00 00 00 00 00 00 00 00 00 00 00 c0 a8 00 01
    An IPv6 "IPv4 mapped" address, "::ffff:192.168.0.1".
    00 00 00 00 00 00 00 00 00 00 ff ff c0 a8 00 01

    A few notes about IPv6 "IPv4 mapped" addresses and their observed use in Java.

    "IPv4 mapped" addresses were originally a representation of IPv4 addresses for use on an IPv6 socket that could receive both IPv4 and IPv6 connections (by disabling the IPV6_V6ONLY socket option on an IPv6 socket). Yes, it's confusing. Nevertheless, these "mapped" addresses were never supposed to be seen on the wire. That assumption was dropped, some say mistakenly, in later RFCs with the apparent aim of making IPv4-to-IPv6 transition simpler.

    Technically one can create a 128bit IPv6 address with the wire format of a "mapped" address, as shown above, and transmit it in an IPv6 packet header. However, Java's InetAddress creation methods appear to adhere doggedly to the original intent of the "mapped" address: all "mapped" addresses return Inet4Address objects.

    For added safety, it is common for IPv6 network operators to filter all packets where either the source or destination address appears to be a "compat" or "mapped" address. Filtering suggestions usually recommend discarding any packets with source or destination addresses in the invalid range ::/3, which includes both of these bizarre address formats. For more information on "bogons", including lists of IPv6 bogon space, see:

    Since:
    5.0
    Author:
    Erik Kline
    • Method Detail

      • forString

        public static InetAddress forString​(String ipString)
        Returns the InetAddress having the given string representation.

        This deliberately avoids all nameservice lookups (e.g. no DNS).

        Anything after a % in an IPv6 address is ignored (assumed to be a Scope ID).

        This method accepts non-ASCII digits, for example "192.168.0.1" (those are fullwidth characters). That is consistent with InetAddress, but not with various RFCs. If you want to accept ASCII digits only, you can use something like CharMatcher.ascii().matchesAllOf(ipString).

        Parameters:
        ipString - String containing an IPv4 or IPv6 string literal, e.g. "192.168.0.1" or "2001:db8::1"
        Returns:
        InetAddress representing the argument
        Throws:
        IllegalArgumentException - if the argument is not a valid IP string literal
      • isInetAddress

        public static boolean isInetAddress​(String ipString)
        Returns true if the supplied string is a valid IP string literal, false otherwise.

        This method accepts non-ASCII digits, for example "192.168.0.1" (those are fullwidth characters). That is consistent with InetAddress, but not with various RFCs. If you want to accept ASCII digits only, you can use something like CharMatcher.ascii().matchesAllOf(ipString).

        Parameters:
        ipString - String to evaluated as an IP string literal
        Returns:
        true if the argument is a valid IP string literal
      • toAddrString

        public static String toAddrString​(InetAddress ip)
        Returns the string representation of an InetAddress.

        For IPv4 addresses, this is identical to InetAddress.getHostAddress(), but for IPv6 addresses, the output follows RFC 5952 section 4. The main difference is that this method uses "::" for zero compression, while Java's version uses the uncompressed form.

        This method uses hexadecimal for all IPv6 addresses, including IPv4-mapped IPv6 addresses such as "::c000:201". The output does not include a Scope ID.

        Parameters:
        ip - InetAddress to be converted to an address string
        Returns:
        String containing the text-formatted IP address
        Since:
        10.0
      • forUriString

        public static InetAddress forUriString​(String hostAddr)
        Returns an InetAddress representing the literal IPv4 or IPv6 host portion of a URL, encoded in the format specified by RFC 3986 section 3.2.2.

        This method is similar to forString(String), however, it requires that IPv6 addresses are surrounded by square brackets.

        This method is the inverse of toUriString(java.net.InetAddress).

        This method accepts non-ASCII digits, for example "192.168.0.1" (those are fullwidth characters). That is consistent with InetAddress, but not with various RFCs. If you want to accept ASCII digits only, you can use something like CharMatcher.ascii().matchesAllOf(ipString).

        Parameters:
        hostAddr - A RFC 3986 section 3.2.2 encoded IPv4 or IPv6 address
        Returns:
        an InetAddress representing the address in hostAddr
        Throws:
        IllegalArgumentException - if hostAddr is not a valid IPv4 address, or IPv6 address surrounded by square brackets
      • isUriInetAddress

        public static boolean isUriInetAddress​(String ipString)
        Returns true if the supplied string is a valid URI IP string literal, false otherwise.

        This method accepts non-ASCII digits, for example "192.168.0.1" (those are fullwidth characters). That is consistent with InetAddress, but not with various RFCs. If you want to accept ASCII digits only, you can use something like CharMatcher.ascii().matchesAllOf(ipString).

        Parameters:
        ipString - String to evaluated as an IP URI host string literal
        Returns:
        true if the argument is a valid IP URI host
      • isCompatIPv4Address

        public static boolean isCompatIPv4Address​(Inet6Address ip)
        Evaluates whether the argument is an IPv6 "compat" address.

        An "IPv4 compatible", or "compat", address is one with 96 leading bits of zero, with the remaining 32 bits interpreted as an IPv4 address. These are conventionally represented in string literals as "::192.168.0.1", though "::c0a8:1" is also considered an IPv4 compatible address (and equivalent to "::192.168.0.1").

        For more on IPv4 compatible addresses see section 2.5.5.1 of RFC 4291.

        NOTE: This method is different from Inet6Address.isIPv4CompatibleAddress() in that it more correctly classifies "::" and "::1" as proper IPv6 addresses (which they are), NOT IPv4 compatible addresses (which they are generally NOT considered to be).

        Parameters:
        ip - Inet6Address to be examined for embedded IPv4 compatible address format
        Returns:
        true if the argument is a valid "compat" address
      • is6to4Address

        public static boolean is6to4Address​(Inet6Address ip)
        Evaluates whether the argument is a 6to4 address.

        6to4 addresses begin with the "2002::/16" prefix. The next 32 bits are the IPv4 address of the host to which IPv6-in-IPv4 tunneled packets should be routed.

        For more on 6to4 addresses see section 2 of RFC 3056.

        Parameters:
        ip - Inet6Address to be examined for 6to4 address format
        Returns:
        true if the argument is a 6to4 address
      • isTeredoAddress

        public static boolean isTeredoAddress​(Inet6Address ip)
        Evaluates whether the argument is a Teredo address.

        Teredo addresses begin with the "2001::/32" prefix.

        Parameters:
        ip - Inet6Address to be examined for Teredo address format
        Returns:
        true if the argument is a Teredo address
      • isIsatapAddress

        public static boolean isIsatapAddress​(Inet6Address ip)
        Evaluates whether the argument is an ISATAP address.

        From RFC 5214: "ISATAP interface identifiers are constructed in Modified EUI-64 format [...] by concatenating the 24-bit IANA OUI (00-00-5E), the 8-bit hexadecimal value 0xFE, and a 32-bit IPv4 address in network byte order [...]"

        For more on ISATAP addresses see section 6.1 of RFC 5214.

        Parameters:
        ip - Inet6Address to be examined for ISATAP address format
        Returns:
        true if the argument is an ISATAP address
      • hasEmbeddedIPv4ClientAddress

        public static boolean hasEmbeddedIPv4ClientAddress​(Inet6Address ip)
        Examines the Inet6Address to determine if it is an IPv6 address of one of the specified address types that contain an embedded IPv4 address.

        NOTE: ISATAP addresses are explicitly excluded from this method due to their trivial spoofability. With other transition addresses spoofing involves (at least) infection of one's BGP routing table.

        Parameters:
        ip - Inet6Address to be examined for embedded IPv4 client address
        Returns:
        true if there is an embedded IPv4 client address
        Since:
        7.0
      • getEmbeddedIPv4ClientAddress

        public static Inet4Address getEmbeddedIPv4ClientAddress​(Inet6Address ip)
        Examines the Inet6Address to extract the embedded IPv4 client address if the InetAddress is an IPv6 address of one of the specified address types that contain an embedded IPv4 address.

        NOTE: ISATAP addresses are explicitly excluded from this method due to their trivial spoofability. With other transition addresses spoofing involves (at least) infection of one's BGP routing table.

        Parameters:
        ip - Inet6Address to be examined for embedded IPv4 client address
        Returns:
        Inet4Address of embedded IPv4 client address
        Throws:
        IllegalArgumentException - if the argument does not have a valid embedded IPv4 address
      • isMappedIPv4Address

        public static boolean isMappedIPv4Address​(String ipString)
        Evaluates whether the argument is an "IPv4 mapped" IPv6 address.

        An "IPv4 mapped" address is anything in the range ::ffff:0:0/96 (sometimes written as ::ffff:0.0.0.0/96), with the last 32 bits interpreted as an IPv4 address.

        For more on IPv4 mapped addresses see section 2.5.5.2 of RFC 4291.

        Note: This method takes a String argument because InetAddress automatically collapses mapped addresses to IPv4. (It is actually possible to avoid this using one of the obscure Inet6Address methods, but it would be unwise to depend on such a poorly-documented feature.)

        This method accepts non-ASCII digits. That is consistent with InetAddress, but not with various RFCs. If you want to accept ASCII digits only, you can use something like CharMatcher.ascii().matchesAllOf(ipString).

        Parameters:
        ipString - String to be examined for embedded IPv4-mapped IPv6 address format
        Returns:
        true if the argument is a valid "mapped" address
        Since:
        10.0
      • getCoercedIPv4Address

        public static Inet4Address getCoercedIPv4Address​(InetAddress ip)
        Coerces an IPv6 address into an IPv4 address.

        HACK: As long as applications continue to use IPv4 addresses for indexing into tables, accounting, et cetera, it may be necessary to coerce IPv6 addresses into IPv4 addresses. This method does so by hashing 64 bits of the IPv6 address into 224.0.0.0/3 (64 bits into 29 bits):

        • If the IPv6 address contains an embedded IPv4 address, the function hashes that.
        • Otherwise, it hashes the upper 64 bits of the IPv6 address.

        A "coerced" IPv4 address is equivalent to itself.

        NOTE: This method is failsafe for security purposes: ALL IPv6 addresses (except localhost (::1)) are hashed to avoid the security risk associated with extracting an embedded IPv4 address that might permit elevated privileges.

        Parameters:
        ip - InetAddress to "coerce"
        Returns:
        Inet4Address represented "coerced" address
        Since:
        7.0
      • coerceToInteger

        public static int coerceToInteger​(InetAddress ip)
        Returns an integer representing an IPv4 address regardless of whether the supplied argument is an IPv4 address or not.

        IPv6 addresses are coerced to IPv4 addresses before being converted to integers.

        As long as there are applications that assume that all IP addresses are IPv4 addresses and can therefore be converted safely to integers (for whatever purpose) this function can be used to handle IPv6 addresses as well until the application is suitably fixed.

        NOTE: an IPv6 address coerced to an IPv4 address can only be used for such purposes as rudimentary identification or indexing into a collection of real InetAddresses. They cannot be used as real addresses for the purposes of network communication.

        Parameters:
        ip - InetAddress to convert
        Returns:
        int, "coerced" if ip is not an IPv4 address
        Since:
        7.0
      • toBigInteger

        public static BigInteger toBigInteger​(InetAddress address)
        Returns a BigInteger representing the address.

        Unlike coerceToInteger, IPv6 addresses are not coerced to IPv4 addresses.

        Parameters:
        address - InetAddress to convert
        Returns:
        BigInteger representation of the address
        Since:
        28.2
      • fromInteger

        public static Inet4Address fromInteger​(int address)
        Returns an Inet4Address having the integer value specified by the argument.
        Parameters:
        address - int, the 32bit integer address to be converted
        Returns:
        Inet4Address equivalent of the argument
      • fromIPv4BigInteger

        public static Inet4Address fromIPv4BigInteger​(BigInteger address)
        Returns the Inet4Address corresponding to a given BigInteger.
        Parameters:
        address - BigInteger representing the IPv4 address
        Returns:
        Inet4Address representation of the given BigInteger
        Throws:
        IllegalArgumentException - if the BigInteger is not between 0 and 2^32-1
        Since:
        28.2
      • fromIPv6BigInteger

        public static Inet6Address fromIPv6BigInteger​(BigInteger address)
        Returns the Inet6Address corresponding to a given BigInteger.
        Parameters:
        address - BigInteger representing the IPv6 address
        Returns:
        Inet6Address representation of the given BigInteger
        Throws:
        IllegalArgumentException - if the BigInteger is not between 0 and 2^128-1
        Since:
        28.2
      • decrement

        public static InetAddress decrement​(InetAddress address)
        Returns a new InetAddress that is one less than the passed in address. This method works for both IPv4 and IPv6 addresses.
        Parameters:
        address - the InetAddress to decrement
        Returns:
        a new InetAddress that is one less than the passed in address
        Throws:
        IllegalArgumentException - if InetAddress is at the beginning of its range
        Since:
        18.0
      • increment

        public static InetAddress increment​(InetAddress address)
        Returns a new InetAddress that is one more than the passed in address. This method works for both IPv4 and IPv6 addresses.
        Parameters:
        address - the InetAddress to increment
        Returns:
        a new InetAddress that is one more than the passed in address
        Throws:
        IllegalArgumentException - if InetAddress is at the end of its range
        Since:
        10.0
      • isMaximum

        public static boolean isMaximum​(InetAddress address)
        Returns true if the InetAddress is either 255.255.255.255 for IPv4 or ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff for IPv6.
        Returns:
        true if the InetAddress is either 255.255.255.255 for IPv4 or ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff for IPv6
        Since:
        10.0