com.google.common.net
Class InetAddresses

java.lang.Object
  com.google.common.net.InetAddresses

@Beta
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.

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:

• http://en.wikipedia.org/wiki/Bogon_filtering
• http://www.cymru.com/Bogons/ipv6.txt
• http://www.cymru.com/Bogons/v6bogon.html
• http://www.space.net/~gert/RIPE/ipv6-filters.html

Since:

5

Author:

Erik Kline

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

toUriString

public static String toUriString(InetAddress ip)

Returns the string representation of an InetAddress suitable for inclusion in a URI.

For IPv4 addresses, this is identical to InetAddress.getHostAddress(), but for IPv6 addresses it surrounds this text with square brackets; for example "[2001:db8::1]".

Per section 3.2.2 of http://tools.ietf.org/html/rfc3986, a URI containing an IPv6 string literal is of the form "http://[2001:db8::1]:8888/index.html".

Use of either InetAddress.getHostAddress() or this method is recommended over InetAddress.toString() when an IP address string literal is desired. This is because InetAddress.toString() prints the hostname and the IP address string joined by a "/".

Parameters:

ip - InetAddress to be converted to URI string literal

Returns:

String containing URI-safe string literal

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

isUriInetAddress

public static boolean isUriInetAddress(String ipString)

Returns true if the supplied string is a valid URI IP string literal, false otherwise.

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 http://tools.ietf.org/html/rfc4291

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

getCompatIPv4Address

public static Inet4Address getCompatIPv4Address(Inet6Address ip)

Returns the IPv4 address embedded in an IPv4 compatible address.

Parameters:

ip - Inet6Address to be examined for an embedded IPv4 address

Returns:

Inet4Address of the embedded IPv4 address

Throws:

IllegalArgumentException - if the argument is not a valid IPv4 compatible 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 http://tools.ietf.org/html/rfc3056

Parameters:

ip - Inet6Address to be examined for 6to4 address format

Returns:

true if the argument is a 6to4 address

get6to4IPv4Address

public static Inet4Address get6to4IPv4Address(Inet6Address ip)

Returns the IPv4 address embedded in a 6to4 address.

Parameters:

ip - Inet6Address to be examined for embedded IPv4 in 6to4 address.

Returns:

Inet4Address of embedded IPv4 in 6to4 address.

Throws:

IllegalArgumentException - if the argument is not a valid IPv6 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

getTeredoInfo

public static InetAddresses.TeredoInfo getTeredoInfo(Inet6Address ip)

Returns the Teredo information embedded in a Teredo address.

Parameters:

ip - Inet6Address to be examined for embedded Teredo information

Returns:

extracted TeredoInfo

Throws:

IllegalArgumentException - if the argument is not a valid IPv6 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 http://tools.ietf.org/html/rfc5214

Parameters:

ip - Inet6Address to be examined for ISATAP address format.

Returns:

true if the argument is an ISATAP address

getIsatapIPv4Address

public static Inet4Address getIsatapIPv4Address(Inet6Address ip)

Returns the IPv4 address embedded in an ISATAP address.

Parameters:

ip - Inet6Address to be examined for embedded IPv4 in ISATAP address

Returns:

Inet4Address of embedded IPv4 in an ISATAP address

Throws:

IllegalArgumentException - if the argument is not a valid IPv6 ISATAP address

getEmbeddedIPv4ClientAddress

public static Inet4Address getEmbeddedIPv4ClientAddress(Inet6Address ip)

Examines the InetAddress 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 Google'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.

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

fromLittleEndianByteArray

public static InetAddress fromLittleEndianByteArray(byte[] addr)
                                             throws UnknownHostException

Returns an address from a little-endian ordered byte array (the opposite of what InetAddress.getByAddress(java.lang.String, byte[]) expects).

IPv4 address byte array must be 4 bytes long and IPv6 byte array must be 16 bytes long.

Parameters:

addr - the raw IP address in little-endian byte order

Returns:

an InetAddress object created from the raw IP address

Throws:

UnknownHostException - if IP address is of illegal length