Package io.ebeaninternal.server.type

Class ConvertInetAddresses

  • public final class ConvertInetAddresses
extends Object
    Rob Bygrave: This is a copy of the google guava InetAddresses class with some features removed.

    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.

    This class hooks into the sun.net.util.IPAddressUtil class to make use of the textToNumericFormatV4 and textToNumericFormatV6 methods directly as a means to avoid accidentally traversing all nameservices (it can be vitally important to avoid, say, blocking on DNS at times).

    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
    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).

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

      • fromHost

        public static InetAddress fromHost​(String hostAddr)
        Parse the IPv4 or IPv6 address without quare brackets around IPv6 addresses.

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

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

        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