Java tutorial
/* * Copyright (c) 1995, 2019, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.net; import java.util.NavigableSet; import java.util.ArrayList; import java.util.Objects; import java.util.Scanner; import java.security.AccessController; import java.io.File; import java.io.FileNotFoundException; import java.io.ObjectStreamException; import java.io.ObjectStreamField; import java.io.IOException; import java.io.InvalidObjectException; import java.io.ObjectInputStream; import java.io.ObjectInputStream.GetField; import java.io.ObjectOutputStream; import java.io.ObjectOutputStream.PutField; import java.lang.annotation.Native; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentMap; import java.util.concurrent.ConcurrentSkipListSet; import java.util.concurrent.atomic.AtomicLong; import java.util.Arrays; import jdk.internal.access.JavaNetInetAddressAccess; import jdk.internal.access.SharedSecrets; import sun.security.action.*; import sun.net.InetAddressCachePolicy; import sun.net.util.IPAddressUtil; /** * This class represents an Internet Protocol (IP) address. * * <p> An IP address is either a 32-bit or 128-bit unsigned number * used by IP, a lower-level protocol on which protocols like UDP and * TCP are built. The IP address architecture is defined by <a * href="http://www.ietf.org/rfc/rfc790.txt"><i>RFC 790: * Assigned Numbers</i></a>, <a * href="http://www.ietf.org/rfc/rfc1918.txt"> <i>RFC 1918: * Address Allocation for Private Internets</i></a>, <a * href="http://www.ietf.org/rfc/rfc2365.txt"><i>RFC 2365: * Administratively Scoped IP Multicast</i></a>, and <a * href="http://www.ietf.org/rfc/rfc2373.txt"><i>RFC 2373: IP * Version 6 Addressing Architecture</i></a>. An instance of an * InetAddress consists of an IP address and possibly its * corresponding host name (depending on whether it is constructed * with a host name or whether it has already done reverse host name * resolution). * * <h2> Address types </h2> * * <table class="striped" style="margin-left:2em"> * <caption style="display:none">Description of unicast and multicast address types</caption> * <thead> * <tr><th scope="col">Address Type</th><th scope="col">Description</th></tr> * </thead> * <tbody> * <tr><th scope="row" style="vertical-align:top">unicast</th> * <td>An identifier for a single interface. A packet sent to * a unicast address is delivered to the interface identified by * that address. * * <p> The Unspecified Address -- Also called anylocal or wildcard * address. It must never be assigned to any node. It indicates the * absence of an address. One example of its use is as the target of * bind, which allows a server to accept a client connection on any * interface, in case the server host has multiple interfaces. * * <p> The <i>unspecified</i> address must not be used as * the destination address of an IP packet. * * <p> The <i>Loopback</i> Addresses -- This is the address * assigned to the loopback interface. Anything sent to this * IP address loops around and becomes IP input on the local * host. This address is often used when testing a * client.</td></tr> * <tr><th scope="row" style="vertical-align:top">multicast</th> * <td>An identifier for a set of interfaces (typically belonging * to different nodes). A packet sent to a multicast address is * delivered to all interfaces identified by that address.</td></tr> * </tbody> * </table> * * <h3> IP address scope </h3> * * <p> <i>Link-local</i> addresses are designed to be used for addressing * on a single link for purposes such as auto-address configuration, * neighbor discovery, or when no routers are present. * * <p> <i>Site-local</i> addresses are designed to be used for addressing * inside of a site without the need for a global prefix. * * <p> <i>Global</i> addresses are unique across the internet. * * <h3> Textual representation of IP addresses </h3> * * The textual representation of an IP address is address family specific. * * <p> * * For IPv4 address format, please refer to <A * HREF="Inet4Address.html#format">Inet4Address#format</A>; For IPv6 * address format, please refer to <A * HREF="Inet6Address.html#format">Inet6Address#format</A>. * * <P>There is a <a href="doc-files/net-properties.html#Ipv4IPv6">couple of * System Properties</a> affecting how IPv4 and IPv6 addresses are used.</P> * * <h3> Host Name Resolution </h3> * * Host name-to-IP address <i>resolution</i> is accomplished through * the use of a combination of local machine configuration information * and network naming services such as the Domain Name System (DNS) * and Network Information Service(NIS). The particular naming * services(s) being used is by default the local machine configured * one. For any host name, its corresponding IP address is returned. * * <p> <i>Reverse name resolution</i> means that for any IP address, * the host associated with the IP address is returned. * * <p> The InetAddress class provides methods to resolve host names to * their IP addresses and vice versa. * * <h3> InetAddress Caching </h3> * * The InetAddress class has a cache to store successful as well as * unsuccessful host name resolutions. * * <p> By default, when a security manager is installed, in order to * protect against DNS spoofing attacks, * the result of positive host name resolutions are * cached forever. When a security manager is not installed, the default * behavior is to cache entries for a finite (implementation dependent) * period of time. The result of unsuccessful host * name resolution is cached for a very short period of time (10 * seconds) to improve performance. * * <p> If the default behavior is not desired, then a Java security property * can be set to a different Time-to-live (TTL) value for positive * caching. Likewise, a system admin can configure a different * negative caching TTL value when needed. * * <p> Two Java security properties control the TTL values used for * positive and negative host name resolution caching: * * <dl style="margin-left:2em"> * <dt><b>networkaddress.cache.ttl</b></dt> * <dd>Indicates the caching policy for successful name lookups from * the name service. The value is specified as an integer to indicate * the number of seconds to cache the successful lookup. The default * setting is to cache for an implementation specific period of time. * <p> * A value of -1 indicates "cache forever". * </dd> * <dt><b>networkaddress.cache.negative.ttl</b> (default: 10)</dt> * <dd>Indicates the caching policy for un-successful name lookups * from the name service. The value is specified as an integer to * indicate the number of seconds to cache the failure for * un-successful lookups. * <p> * A value of 0 indicates "never cache". * A value of -1 indicates "cache forever". * </dd> * </dl> * * @author Chris Warth * @see java.net.InetAddress#getByAddress(byte[]) * @see java.net.InetAddress#getByAddress(java.lang.String, byte[]) * @see java.net.InetAddress#getAllByName(java.lang.String) * @see java.net.InetAddress#getByName(java.lang.String) * @see java.net.InetAddress#getLocalHost() * @since 1.0 */ public class InetAddress implements java.io.Serializable { @Native static final int PREFER_IPV4_VALUE = 0; @Native static final int PREFER_IPV6_VALUE = 1; @Native static final int PREFER_SYSTEM_VALUE = 2; /** * Specify the address family: Internet Protocol, Version 4 * @since 1.4 */ @Native static final int IPv4 = 1; /** * Specify the address family: Internet Protocol, Version 6 * @since 1.4 */ @Native static final int IPv6 = 2; /* Specify address family preference */ static transient final int preferIPv6Address; static class InetAddressHolder { /** * Reserve the original application specified hostname. * * The original hostname is useful for domain-based endpoint * identification (see RFC 2818 and RFC 6125). If an address * was created with a raw IP address, a reverse name lookup * may introduce endpoint identification security issue via * DNS forging. * * Oracle JSSE provider is using this original hostname, via * jdk.internal.misc.JavaNetAccess, for SSL/TLS endpoint identification. * * Note: May define a new public method in the future if necessary. */ String originalHostName; InetAddressHolder() { } InetAddressHolder(String hostName, int address, int family) { this.originalHostName = hostName; this.hostName = hostName; this.address = address; this.family = family; } void init(String hostName, int family) { this.originalHostName = hostName; this.hostName = hostName; if (family != -1) { this.family = family; } } String hostName; String getHostName() { return hostName; } String getOriginalHostName() { return originalHostName; } /** * Holds a 32-bit IPv4 address. */ int address; int getAddress() { return address; } /** * Specifies the address family type, for instance, '1' for IPv4 * addresses, and '2' for IPv6 addresses. */ int family; int getFamily() { return family; } } /* Used to store the serializable fields of InetAddress */ final transient InetAddressHolder holder; InetAddressHolder holder() { return holder; } /* Used to store the name service provider */ private static transient NameService nameService = null; /** * Used to store the best available hostname. * Lazily initialized via a data race; safe because Strings are immutable. */ private transient String canonicalHostName = null; /** use serialVersionUID from JDK 1.0.2 for interoperability */ private static final long serialVersionUID = 3286316764910316507L; /* * Load net library into runtime, and perform initializations. */ static { String str = java.security.AccessController .doPrivileged(new GetPropertyAction("java.net.preferIPv6Addresses")); if (str == null) { preferIPv6Address = PREFER_IPV4_VALUE; } else if (str.equalsIgnoreCase("true")) { preferIPv6Address = PREFER_IPV6_VALUE; } else if (str.equalsIgnoreCase("false")) { preferIPv6Address = PREFER_IPV4_VALUE; } else if (str.equalsIgnoreCase("system")) { preferIPv6Address = PREFER_SYSTEM_VALUE; } else { preferIPv6Address = PREFER_IPV4_VALUE; } AccessController.doPrivileged(new java.security.PrivilegedAction<>() { public Void run() { System.loadLibrary("net"); return null; } }); SharedSecrets.setJavaNetInetAddressAccess(new JavaNetInetAddressAccess() { public String getOriginalHostName(InetAddress ia) { return ia.holder.getOriginalHostName(); } public InetAddress getByName(String hostName, InetAddress hostAddress) throws UnknownHostException { return InetAddress.getByName(hostName, hostAddress); } }); init(); } /** * Constructor for the Socket.accept() method. * This creates an empty InetAddress, which is filled in by * the accept() method. This InetAddress, however, is not * put in the address cache, since it is not created by name. */ InetAddress() { holder = new InetAddressHolder(); } /** * Replaces the de-serialized object with an Inet4Address object. * * @return the alternate object to the de-serialized object. * * @throws ObjectStreamException if a new object replacing this * object could not be created */ private Object readResolve() throws ObjectStreamException { // will replace the deserialized 'this' object return new Inet4Address(holder().getHostName(), holder().getAddress()); } /** * Utility routine to check if the InetAddress is an * IP multicast address. * @return a {@code boolean} indicating if the InetAddress is * an IP multicast address * @since 1.1 */ public boolean isMulticastAddress() { return false; } /** * Utility routine to check if the InetAddress is a wildcard address. * @return a {@code boolean} indicating if the InetAddress is * a wildcard address. * @since 1.4 */ public boolean isAnyLocalAddress() { return false; } /** * Utility routine to check if the InetAddress is a loopback address. * * @return a {@code boolean} indicating if the InetAddress is * a loopback address; or false otherwise. * @since 1.4 */ public boolean isLoopbackAddress() { return false; } /** * Utility routine to check if the InetAddress is an link local address. * * @return a {@code boolean} indicating if the InetAddress is * a link local address; or false if address is not a link local unicast address. * @since 1.4 */ public boolean isLinkLocalAddress() { return false; } /** * Utility routine to check if the InetAddress is a site local address. * * @return a {@code boolean} indicating if the InetAddress is * a site local address; or false if address is not a site local unicast address. * @since 1.4 */ public boolean isSiteLocalAddress() { return false; } /** * Utility routine to check if the multicast address has global scope. * * @return a {@code boolean} indicating if the address has * is a multicast address of global scope, false if it is not * of global scope or it is not a multicast address * @since 1.4 */ public boolean isMCGlobal() { return false; } /** * Utility routine to check if the multicast address has node scope. * * @return a {@code boolean} indicating if the address has * is a multicast address of node-local scope, false if it is not * of node-local scope or it is not a multicast address * @since 1.4 */ public boolean isMCNodeLocal() { return false; } /** * Utility routine to check if the multicast address has link scope. * * @return a {@code boolean} indicating if the address has * is a multicast address of link-local scope, false if it is not * of link-local scope or it is not a multicast address * @since 1.4 */ public boolean isMCLinkLocal() { return false; } /** * Utility routine to check if the multicast address has site scope. * * @return a {@code boolean} indicating if the address has * is a multicast address of site-local scope, false if it is not * of site-local scope or it is not a multicast address * @since 1.4 */ public boolean isMCSiteLocal() { return false; } /** * Utility routine to check if the multicast address has organization scope. * * @return a {@code boolean} indicating if the address has * is a multicast address of organization-local scope, * false if it is not of organization-local scope * or it is not a multicast address * @since 1.4 */ public boolean isMCOrgLocal() { return false; } /** * Test whether that address is reachable. Best effort is made by the * implementation to try to reach the host, but firewalls and server * configuration may block requests resulting in a unreachable status * while some specific ports may be accessible. * A typical implementation will use ICMP ECHO REQUESTs if the * privilege can be obtained, otherwise it will try to establish * a TCP connection on port 7 (Echo) of the destination host. * <p> * The timeout value, in milliseconds, indicates the maximum amount of time * the try should take. If the operation times out before getting an * answer, the host is deemed unreachable. A negative value will result * in an IllegalArgumentException being thrown. * * @param timeout the time, in milliseconds, before the call aborts * @return a {@code boolean} indicating if the address is reachable. * @throws IOException if a network error occurs * @throws IllegalArgumentException if {@code timeout} is negative. * @since 1.5 */ public boolean isReachable(int timeout) throws IOException { return isReachable(null, 0, timeout); } /** * Test whether that address is reachable. Best effort is made by the * implementation to try to reach the host, but firewalls and server * configuration may block requests resulting in a unreachable status * while some specific ports may be accessible. * A typical implementation will use ICMP ECHO REQUESTs if the * privilege can be obtained, otherwise it will try to establish * a TCP connection on port 7 (Echo) of the destination host. * <p> * The {@code network interface} and {@code ttl} parameters * let the caller specify which network interface the test will go through * and the maximum number of hops the packets should go through. * A negative value for the {@code ttl} will result in an * IllegalArgumentException being thrown. * <p> * The timeout value, in milliseconds, indicates the maximum amount of time * the try should take. If the operation times out before getting an * answer, the host is deemed unreachable. A negative value will result * in an IllegalArgumentException being thrown. * * @param netif the NetworkInterface through which the * test will be done, or null for any interface * @param ttl the maximum numbers of hops to try or 0 for the * default * @param timeout the time, in milliseconds, before the call aborts * @throws IllegalArgumentException if either {@code timeout} * or {@code ttl} are negative. * @return a {@code boolean} indicating if the address is reachable. * @throws IOException if a network error occurs * @since 1.5 */ public boolean isReachable(NetworkInterface netif, int ttl, int timeout) throws IOException { if (ttl < 0) throw new IllegalArgumentException("ttl can't be negative"); if (timeout < 0) throw new IllegalArgumentException("timeout can't be negative"); return impl.isReachable(this, timeout, netif, ttl); } /** * Gets the host name for this IP address. * * <p>If this InetAddress was created with a host name, * this host name will be remembered and returned; * otherwise, a reverse name lookup will be performed * and the result will be returned based on the system * configured name lookup service. If a lookup of the name service * is required, call * {@link #getCanonicalHostName() getCanonicalHostName}. * * <p>If there is a security manager, its * {@code checkConnect} method is first called * with the hostname and {@code -1} * as its arguments to see if the operation is allowed. * If the operation is not allowed, it will return * the textual representation of the IP address. * * @return the host name for this IP address, or if the operation * is not allowed by the security check, the textual * representation of the IP address. * * @see InetAddress#getCanonicalHostName * @see SecurityManager#checkConnect */ public String getHostName() { return getHostName(true); } /** * Returns the hostname for this address. * If the host is equal to null, then this address refers to any * of the local machine's available network addresses. * this is package private so SocketPermission can make calls into * here without a security check. * * <p>If there is a security manager, this method first * calls its {@code checkConnect} method * with the hostname and {@code -1} * as its arguments to see if the calling code is allowed to know * the hostname for this IP address, i.e., to connect to the host. * If the operation is not allowed, it will return * the textual representation of the IP address. * * @return the host name for this IP address, or if the operation * is not allowed by the security check, the textual * representation of the IP address. * * @param check make security check if true * * @see SecurityManager#checkConnect */ String getHostName(boolean check) { if (holder().getHostName() == null) { holder().hostName = InetAddress.getHostFromNameService(this, check); } return holder().getHostName(); } /** * Gets the fully qualified domain name for this IP address. * Best effort method, meaning we may not be able to return * the FQDN depending on the underlying system configuration. * * <p>If there is a security manager, this method first * calls its {@code checkConnect} method * with the hostname and {@code -1} * as its arguments to see if the calling code is allowed to know * the hostname for this IP address, i.e., to connect to the host. * If the operation is not allowed, it will return * the textual representation of the IP address. * * @return the fully qualified domain name for this IP address, * or if the operation is not allowed by the security check, * the textual representation of the IP address. * * @see SecurityManager#checkConnect * * @since 1.4 */ public String getCanonicalHostName() { String value = canonicalHostName; if (value == null) canonicalHostName = value = InetAddress.getHostFromNameService(this, true); return value; } /** * Returns the hostname for this address. * * <p>If there is a security manager, this method first * calls its {@code checkConnect} method * with the hostname and {@code -1} * as its arguments to see if the calling code is allowed to know * the hostname for this IP address, i.e., to connect to the host. * If the operation is not allowed, it will return * the textual representation of the IP address. * * @return the host name for this IP address, or if the operation * is not allowed by the security check, the textual * representation of the IP address. * * @param check make security check if true * * @see SecurityManager#checkConnect */ private static String getHostFromNameService(InetAddress addr, boolean check) { String host = null; try { // first lookup the hostname host = nameService.getHostByAddr(addr.getAddress()); /* check to see if calling code is allowed to know * the hostname for this IP address, ie, connect to the host */ if (check) { SecurityManager sec = System.getSecurityManager(); if (sec != null) { sec.checkConnect(host, -1); } } /* now get all the IP addresses for this hostname, * and make sure one of them matches the original IP * address. We do this to try and prevent spoofing. */ InetAddress[] arr = InetAddress.getAllByName0(host, check); boolean ok = false; if (arr != null) { for (int i = 0; !ok && i < arr.length; i++) { ok = addr.equals(arr[i]); } } //XXX: if it looks a spoof just return the address? if (!ok) { host = addr.getHostAddress(); return host; } } catch (SecurityException e) { host = addr.getHostAddress(); } catch (UnknownHostException e) { host = addr.getHostAddress(); // let next provider resolve the hostname } return host; } /** * Returns the raw IP address of this {@code InetAddress} * object. The result is in network byte order: the highest order * byte of the address is in {@code getAddress()[0]}. * * @return the raw IP address of this object. */ public byte[] getAddress() { return null; } /** * Returns the IP address string in textual presentation. * * @return the raw IP address in a string format. * @since 1.0.2 */ public String getHostAddress() { return null; } /** * Returns a hashcode for this IP address. * * @return a hash code value for this IP address. */ public int hashCode() { return -1; } /** * Compares this object against the specified object. * The result is {@code true} if and only if the argument is * not {@code null} and it represents the same IP address as * this object. * <p> * Two instances of {@code InetAddress} represent the same IP * address if the length of the byte arrays returned by * {@code getAddress} is the same for both, and each of the * array components is the same for the byte arrays. * * @param obj the object to compare against. * @return {@code true} if the objects are the same; * {@code false} otherwise. * @see java.net.InetAddress#getAddress() */ public boolean equals(Object obj) { return false; } /** * Converts this IP address to a {@code String}. The * string returned is of the form: hostname / literal IP * address. * * If the host name is unresolved, no reverse name service lookup * is performed. The hostname part will be represented by an empty string. * * @return a string representation of this IP address. */ public String toString() { String hostName = holder().getHostName(); return Objects.toString(hostName, "") + "/" + getHostAddress(); } // mapping from host name to Addresses - either NameServiceAddresses (while // still being looked-up by NameService(s)) or CachedAddresses when cached private static final ConcurrentMap<String, Addresses> cache = new ConcurrentHashMap<>(); // CachedAddresses that have to expire are kept ordered in this NavigableSet // which is scanned on each access private static final NavigableSet<CachedAddresses> expirySet = new ConcurrentSkipListSet<>(); // common interface private interface Addresses { InetAddress[] get() throws UnknownHostException; } // a holder for cached addresses with required metadata private static final class CachedAddresses implements Addresses, Comparable<CachedAddresses> { private static final AtomicLong seq = new AtomicLong(); final String host; final InetAddress[] inetAddresses; final long expiryTime; // time of expiry (in terms of System.nanoTime()) final long id = seq.incrementAndGet(); // each instance is unique CachedAddresses(String host, InetAddress[] inetAddresses, long expiryTime) { this.host = host; this.inetAddresses = inetAddresses; this.expiryTime = expiryTime; } @Override public InetAddress[] get() throws UnknownHostException { if (inetAddresses == null) { throw new UnknownHostException(host); } return inetAddresses; } @Override public int compareTo(CachedAddresses other) { // natural order is expiry time - // compare difference of expiry times rather than // expiry times directly, to avoid possible overflow. // (see System.nanoTime() recommendations...) long diff = this.expiryTime - other.expiryTime; if (diff < 0L) return -1; if (diff > 0L) return 1; // ties are broken using unique id return Long.compare(this.id, other.id); } } // a name service lookup based Addresses implementation which replaces itself // in cache when the result is obtained private static final class NameServiceAddresses implements Addresses { private final String host; private final InetAddress reqAddr; NameServiceAddresses(String host, InetAddress reqAddr) { this.host = host; this.reqAddr = reqAddr; } @Override public InetAddress[] get() throws UnknownHostException { Addresses addresses; // only one thread is doing lookup to name service // for particular host at any time. synchronized (this) { // re-check that we are still us + re-install us if slot empty addresses = cache.putIfAbsent(host, this); if (addresses == null) { // this can happen when we were replaced by CachedAddresses in // some other thread, then CachedAddresses expired and were // removed from cache while we were waiting for lock... addresses = this; } // still us ? if (addresses == this) { // lookup name services InetAddress[] inetAddresses; UnknownHostException ex; int cachePolicy; try { inetAddresses = getAddressesFromNameService(host, reqAddr); ex = null; cachePolicy = InetAddressCachePolicy.get(); } catch (UnknownHostException uhe) { inetAddresses = null; ex = uhe; cachePolicy = InetAddressCachePolicy.getNegative(); } // remove or replace us with cached addresses according to cachePolicy if (cachePolicy == InetAddressCachePolicy.NEVER) { cache.remove(host, this); } else { CachedAddresses cachedAddresses = new CachedAddresses(host, inetAddresses, cachePolicy == InetAddressCachePolicy.FOREVER ? 0L // cachePolicy is in [s] - we need [ns] : System.nanoTime() + 1000_000_000L * cachePolicy); if (cache.replace(host, this, cachedAddresses) && cachePolicy != InetAddressCachePolicy.FOREVER) { // schedule expiry expirySet.add(cachedAddresses); } } if (inetAddresses == null) { throw ex == null ? new UnknownHostException(host) : ex; } return inetAddresses; } // else addresses != this } // delegate to different addresses when we are already replaced // but outside of synchronized block to avoid any chance of dead-locking return addresses.get(); } } /** * NameService provides host and address lookup service * * @since 9 */ private interface NameService { /** * Lookup a host mapping by name. Retrieve the IP addresses * associated with a host * * @param host the specified hostname * @return array of IP addresses for the requested host * @throws UnknownHostException * if no IP address for the {@code host} could be found */ InetAddress[] lookupAllHostAddr(String host) throws UnknownHostException; /** * Lookup the host corresponding to the IP address provided * * @param addr byte array representing an IP address * @return {@code String} representing the host name mapping * @throws UnknownHostException * if no host found for the specified IP address */ String getHostByAddr(byte[] addr) throws UnknownHostException; } /** * The default NameService implementation, which delegates to the underlying * OS network libraries to resolve host address mappings. * * @since 9 */ private static final class PlatformNameService implements NameService { public InetAddress[] lookupAllHostAddr(String host) throws UnknownHostException { return impl.lookupAllHostAddr(host); } public String getHostByAddr(byte[] addr) throws UnknownHostException { return impl.getHostByAddr(addr); } } /** * The HostsFileNameService provides host address mapping * by reading the entries in a hosts file, which is specified by * {@code jdk.net.hosts.file} system property * * <p>The file format is that which corresponds with the /etc/hosts file * IP Address host alias list. * * <p>When the file lookup is enabled it replaces the default NameService * implementation * * @since 9 */ private static final class HostsFileNameService implements NameService { private final String hostsFile; public HostsFileNameService(String hostsFileName) { this.hostsFile = hostsFileName; } private String addrToString(byte addr[]) { String stringifiedAddress = null; if (addr.length == Inet4Address.INADDRSZ) { stringifiedAddress = Inet4Address.numericToTextFormat(addr); } else { // treat as an IPV6 jobby byte[] newAddr = IPAddressUtil.convertFromIPv4MappedAddress(addr); if (newAddr != null) { stringifiedAddress = Inet4Address.numericToTextFormat(addr); } else { stringifiedAddress = Inet6Address.numericToTextFormat(addr); } } return stringifiedAddress; } /** * Lookup the host name corresponding to the IP address provided. * Search the configured host file a host name corresponding to * the specified IP address. * * @param addr byte array representing an IP address * @return {@code String} representing the host name mapping * @throws UnknownHostException * if no host found for the specified IP address */ @Override public String getHostByAddr(byte[] addr) throws UnknownHostException { String hostEntry; String host = null; try (Scanner hostsFileScanner = new Scanner(new File(hostsFile), "UTF-8")) { while (hostsFileScanner.hasNextLine()) { hostEntry = hostsFileScanner.nextLine(); if (!hostEntry.startsWith("#")) { hostEntry = removeComments(hostEntry); String[] mapping = hostEntry.split("\\s+"); if (mapping.length >= 2 && Arrays.equals(addr, createAddressByteArray(mapping[0]))) { host = mapping[1]; break; } } } } catch (FileNotFoundException e) { throw new UnknownHostException("Unable to resolve address " + Arrays.toString(addr) + " as hosts file " + hostsFile + " not found "); } if ((host == null) || (host.isEmpty()) || (host.equals(" "))) { throw new UnknownHostException("Requested address " + Arrays.toString(addr) + " resolves to an invalid entry in hosts file " + hostsFile); } return host; } /** * <p>Lookup a host mapping by name. Retrieve the IP addresses * associated with a host. * * <p>Search the configured hosts file for the addresses associated * with the specified host name. * * @param host the specified hostname * @return array of IP addresses for the requested host * @throws UnknownHostException * if no IP address for the {@code host} could be found */ public InetAddress[] lookupAllHostAddr(String host) throws UnknownHostException { String hostEntry; String addrStr = null; InetAddress[] res = null; byte addr[] = new byte[4]; ArrayList<InetAddress> inetAddresses = null; // lookup the file and create a list InetAddress for the specified host try (Scanner hostsFileScanner = new Scanner(new File(hostsFile), "UTF-8")) { while (hostsFileScanner.hasNextLine()) { hostEntry = hostsFileScanner.nextLine(); if (!hostEntry.startsWith("#")) { hostEntry = removeComments(hostEntry); if (hostEntry.contains(host)) { addrStr = extractHostAddr(hostEntry, host); if ((addrStr != null) && (!addrStr.isEmpty())) { addr = createAddressByteArray(addrStr); if (inetAddresses == null) { inetAddresses = new ArrayList<>(1); } if (addr != null) { inetAddresses.add(InetAddress.getByAddress(host, addr)); } } } } } } catch (FileNotFoundException e) { throw new UnknownHostException( "Unable to resolve host " + host + " as hosts file " + hostsFile + " not found "); } if (inetAddresses != null) { res = inetAddresses.toArray(new InetAddress[inetAddresses.size()]); } else { throw new UnknownHostException("Unable to resolve host " + host + " in hosts file " + hostsFile); } return res; } private String removeComments(String hostsEntry) { String filteredEntry = hostsEntry; int hashIndex; if ((hashIndex = hostsEntry.indexOf("#")) != -1) { filteredEntry = hostsEntry.substring(0, hashIndex); } return filteredEntry; } private byte[] createAddressByteArray(String addrStr) { byte[] addrArray; // check if IPV4 address - most likely addrArray = IPAddressUtil.textToNumericFormatV4(addrStr); if (addrArray == null) { addrArray = IPAddressUtil.textToNumericFormatV6(addrStr); } return addrArray; } /** host to ip address mapping */ private String extractHostAddr(String hostEntry, String host) { String[] mapping = hostEntry.split("\\s+"); String hostAddr = null; if (mapping.length >= 2) { // look at the host aliases for (int i = 1; i < mapping.length; i++) { if (mapping[i].equalsIgnoreCase(host)) { hostAddr = mapping[0]; } } } return hostAddr; } } static final InetAddressImpl impl; static { // create the impl impl = InetAddressImplFactory.create(); // create name service nameService = createNameService(); } /** * Create an instance of the NameService interface based on * the setting of the {@code jdk.net.hosts.file} system property. * * <p>The default NameService is the PlatformNameService, which typically * delegates name and address resolution calls to the underlying * OS network libraries. * * <p> A HostsFileNameService is created if the {@code jdk.net.hosts.file} * system property is set. If the specified file doesn't exist, the name or * address lookup will result in an UnknownHostException. Thus, non existent * hosts file is handled as if the file is empty. * * @return a NameService */ private static NameService createNameService() { String hostsFileName = GetPropertyAction.privilegedGetProperty("jdk.net.hosts.file"); NameService theNameService; if (hostsFileName != null) { theNameService = new HostsFileNameService(hostsFileName); } else { theNameService = new PlatformNameService(); } return theNameService; } /** * Creates an InetAddress based on the provided host name and IP address. * No name service is checked for the validity of the address. * * <p> The host name can either be a machine name, such as * "{@code www.example.com}", or a textual representation of its IP * address. * <p> No validity checking is done on the host name either. * * <p> If addr specifies an IPv4 address an instance of Inet4Address * will be returned; otherwise, an instance of Inet6Address * will be returned. * * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array * must be 16 bytes long * * @param host the specified host * @param addr the raw IP address in network byte order * @return an InetAddress object created from the raw IP address. * @exception UnknownHostException if IP address is of illegal length * @since 1.4 */ public static InetAddress getByAddress(String host, byte[] addr) throws UnknownHostException { if (host != null && !host.isEmpty() && host.charAt(0) == '[') { if (host.charAt(host.length() - 1) == ']') { host = host.substring(1, host.length() - 1); } } if (addr != null) { if (addr.length == Inet4Address.INADDRSZ) { return new Inet4Address(host, addr); } else if (addr.length == Inet6Address.INADDRSZ) { byte[] newAddr = IPAddressUtil.convertFromIPv4MappedAddress(addr); if (newAddr != null) { return new Inet4Address(host, newAddr); } else { return new Inet6Address(host, addr); } } } throw new UnknownHostException("addr is of illegal length"); } /** * Determines the IP address of a host, given the host's name. * * <p> The host name can either be a machine name, such as * "{@code www.example.com}", or a textual representation of its * IP address. If a literal IP address is supplied, only the * validity of the address format is checked. * * <p> For {@code host} specified in literal IPv6 address, * either the form defined in RFC 2732 or the literal IPv6 address * format defined in RFC 2373 is accepted. IPv6 scoped addresses are also * supported. See <a href="Inet6Address.html#scoped">here</a> for a description of IPv6 * scoped addresses. * * <p> If the host is {@code null} or {@code host.length()} is equal * to zero, then an {@code InetAddress} representing an address of the * loopback interface is returned. * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC 3330</a> * section 2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC 2373</a> * section 2.5.3. * * <p> If there is a security manager, and {@code host} is not {@code null} * or {@code host.length() } is not equal to zero, the security manager's * {@code checkConnect} method is called with the hostname and {@code -1} * as its arguments to determine if the operation is allowed. * * @param host the specified host, or {@code null}. * @return an IP address for the given host name. * @exception UnknownHostException if no IP address for the * {@code host} could be found, or if a scope_id was specified * for a global IPv6 address. * @exception SecurityException if a security manager exists * and its checkConnect method doesn't allow the operation */ public static InetAddress getByName(String host) throws UnknownHostException { return InetAddress.getAllByName(host)[0]; } // called from deployment cache manager private static InetAddress getByName(String host, InetAddress reqAddr) throws UnknownHostException { return InetAddress.getAllByName(host, reqAddr)[0]; } /** * Given the name of a host, returns an array of its IP addresses, * based on the configured name service on the system. * * <p> The host name can either be a machine name, such as * "{@code www.example.com}", or a textual representation of its IP * address. If a literal IP address is supplied, only the * validity of the address format is checked. * * <p> For {@code host} specified in <i>literal IPv6 address</i>, * either the form defined in RFC 2732 or the literal IPv6 address * format defined in RFC 2373 is accepted. A literal IPv6 address may * also be qualified by appending a scoped zone identifier or scope_id. * The syntax and usage of scope_ids is described * <a href="Inet6Address.html#scoped">here</a>. * * <p> If the host is {@code null} or {@code host.length()} is equal * to zero, then an {@code InetAddress} representing an address of the * loopback interface is returned. * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC 3330</a> * section 2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC 2373</a> * section 2.5.3. </p> * * <p> If there is a security manager, and {@code host} is not {@code null} * or {@code host.length() } is not equal to zero, the security manager's * {@code checkConnect} method is called with the hostname and {@code -1} * as its arguments to determine if the operation is allowed. * * @param host the name of the host, or {@code null}. * @return an array of all the IP addresses for a given host name. * * @exception UnknownHostException if no IP address for the * {@code host} could be found, or if a scope_id was specified * for a global IPv6 address. * @exception SecurityException if a security manager exists and its * {@code checkConnect} method doesn't allow the operation. * * @see SecurityManager#checkConnect */ public static InetAddress[] getAllByName(String host) throws UnknownHostException { return getAllByName(host, null); } private static InetAddress[] getAllByName(String host, InetAddress reqAddr) throws UnknownHostException { if (host == null || host.isEmpty()) { InetAddress[] ret = new InetAddress[1]; ret[0] = impl.loopbackAddress(); return ret; } boolean ipv6Expected = false; if (host.charAt(0) == '[') { // This is supposed to be an IPv6 literal if (host.length() > 2 && host.charAt(host.length() - 1) == ']') { host = host.substring(1, host.length() - 1); ipv6Expected = true; } else { // This was supposed to be a IPv6 address, but it's not! throw new UnknownHostException(host + ": invalid IPv6 address"); } } // if host is an IP address, we won't do further lookup if (Character.digit(host.charAt(0), 16) != -1 || (host.charAt(0) == ':')) { byte[] addr = null; int numericZone = -1; String ifname = null; // see if it is IPv4 address addr = IPAddressUtil.textToNumericFormatV4(host); if (addr == null) { // This is supposed to be an IPv6 literal // Check if a numeric or string zone id is present int pos; if ((pos = host.indexOf('%')) != -1) { numericZone = checkNumericZone(host); if (numericZone == -1) { /* remainder of string must be an ifname */ ifname = host.substring(pos + 1); } } if ((addr = IPAddressUtil.textToNumericFormatV6(host)) == null && host.contains(":")) { throw new UnknownHostException(host + ": invalid IPv6 address"); } } else if (ipv6Expected) { // Means an IPv4 literal between brackets! throw new UnknownHostException("[" + host + "]"); } InetAddress[] ret = new InetAddress[1]; if (addr != null) { if (addr.length == Inet4Address.INADDRSZ) { ret[0] = new Inet4Address(null, addr); } else { if (ifname != null) { ret[0] = new Inet6Address(null, addr, ifname); } else { ret[0] = new Inet6Address(null, addr, numericZone); } } return ret; } } else if (ipv6Expected) { // We were expecting an IPv6 Literal, but got something else throw new UnknownHostException("[" + host + "]"); } return getAllByName0(host, reqAddr, true, true); } /** * Returns the loopback address. * <p> * The InetAddress returned will represent the IPv4 * loopback address, 127.0.0.1, or the IPv6 loopback * address, ::1. The IPv4 loopback address returned * is only one of many in the form 127.*.*.* * * @return the InetAddress loopback instance. * @since 1.7 */ public static InetAddress getLoopbackAddress() { return impl.loopbackAddress(); } /** * check if the literal address string has %nn appended * returns -1 if not, or the numeric value otherwise. * * %nn may also be a string that represents the displayName of * a currently available NetworkInterface. */ private static int checkNumericZone(String s) throws UnknownHostException { int percent = s.indexOf('%'); int slen = s.length(); int digit, zone = 0; if (percent == -1) { return -1; } for (int i = percent + 1; i < slen; i++) { char c = s.charAt(i); if (c == ']') { if (i == percent + 1) { /* empty per-cent field */ return -1; } break; } if ((digit = Character.digit(c, 10)) < 0) { return -1; } zone = (zone * 10) + digit; } return zone; } private static InetAddress[] getAllByName0(String host) throws UnknownHostException { return getAllByName0(host, true); } /** * package private so SocketPermission can call it */ static InetAddress[] getAllByName0(String host, boolean check) throws UnknownHostException { return getAllByName0(host, null, check, true); } /** * Designated lookup method. * * @param host host name to look up * @param reqAddr requested address to be the 1st in returned array * @param check perform security check * @param useCache use cached value if not expired else always * perform name service lookup (and cache the result) * @return array of InetAddress(es) * @throws UnknownHostException if host name is not found */ private static InetAddress[] getAllByName0(String host, InetAddress reqAddr, boolean check, boolean useCache) throws UnknownHostException { /* If it gets here it is presumed to be a hostname */ /* make sure the connection to the host is allowed, before we * give out a hostname */ if (check) { SecurityManager security = System.getSecurityManager(); if (security != null) { security.checkConnect(host, -1); } } // remove expired addresses from cache - expirySet keeps them ordered // by expiry time so we only need to iterate the prefix of the NavigableSet... long now = System.nanoTime(); for (CachedAddresses caddrs : expirySet) { // compare difference of time instants rather than // time instants directly, to avoid possible overflow. // (see System.nanoTime() recommendations...) if ((caddrs.expiryTime - now) < 0L) { // ConcurrentSkipListSet uses weakly consistent iterator, // so removing while iterating is OK... if (expirySet.remove(caddrs)) { // ... remove from cache cache.remove(caddrs.host, caddrs); } } else { // we encountered 1st element that expires in future break; } } // look-up or remove from cache Addresses addrs; if (useCache) { addrs = cache.get(host); } else { addrs = cache.remove(host); if (addrs != null) { if (addrs instanceof CachedAddresses) { // try removing from expirySet too if CachedAddresses expirySet.remove(addrs); } addrs = null; } } if (addrs == null) { // create a NameServiceAddresses instance which will look up // the name service and install it within cache... Addresses oldAddrs = cache.putIfAbsent(host, addrs = new NameServiceAddresses(host, reqAddr)); if (oldAddrs != null) { // lost putIfAbsent race addrs = oldAddrs; } } // ask Addresses to get an array of InetAddress(es) and clone it return addrs.get().clone(); } static InetAddress[] getAddressesFromNameService(String host, InetAddress reqAddr) throws UnknownHostException { InetAddress[] addresses = null; UnknownHostException ex = null; try { addresses = nameService.lookupAllHostAddr(host); } catch (UnknownHostException uhe) { if (host.equalsIgnoreCase("localhost")) { addresses = new InetAddress[] { impl.loopbackAddress() }; } else { ex = uhe; } } if (addresses == null) { throw ex == null ? new UnknownHostException(host) : ex; } // More to do? if (reqAddr != null && addresses.length > 1 && !addresses[0].equals(reqAddr)) { // Find it? int i = 1; for (; i < addresses.length; i++) { if (addresses[i].equals(reqAddr)) { break; } } // Rotate if (i < addresses.length) { InetAddress tmp, tmp2 = reqAddr; for (int j = 0; j < i; j++) { tmp = addresses[j]; addresses[j] = tmp2; tmp2 = tmp; } addresses[i] = tmp2; } } return addresses; } /** * Returns an {@code InetAddress} object given the raw IP address . * The argument is in network byte order: the highest order * byte of the address is in {@code getAddress()[0]}. * * <p> This method doesn't block, i.e. no reverse name service lookup * is performed. * * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array * must be 16 bytes long * * @param addr the raw IP address in network byte order * @return an InetAddress object created from the raw IP address. * @exception UnknownHostException if IP address is of illegal length * @since 1.4 */ public static InetAddress getByAddress(byte[] addr) throws UnknownHostException { return getByAddress(null, addr); } private static final class CachedLocalHost { final String host; final InetAddress addr; final long expiryTime = System.nanoTime() + 5000_000_000L; // now + 5s; CachedLocalHost(String host, InetAddress addr) { this.host = host; this.addr = addr; } } private static volatile CachedLocalHost cachedLocalHost; /** * Returns the address of the local host. This is achieved by retrieving * the name of the host from the system, then resolving that name into * an {@code InetAddress}. * * <P>Note: The resolved address may be cached for a short period of time. * </P> * * <p>If there is a security manager, its * {@code checkConnect} method is called * with the local host name and {@code -1} * as its arguments to see if the operation is allowed. * If the operation is not allowed, an InetAddress representing * the loopback address is returned. * * @return the address of the local host. * * @exception UnknownHostException if the local host name could not * be resolved into an address. * * @see SecurityManager#checkConnect * @see java.net.InetAddress#getByName(java.lang.String) */ public static InetAddress getLocalHost() throws UnknownHostException { SecurityManager security = System.getSecurityManager(); try { // is cached data still valid? CachedLocalHost clh = cachedLocalHost; if (clh != null && (clh.expiryTime - System.nanoTime()) >= 0L) { if (security != null) { security.checkConnect(clh.host, -1); } return clh.addr; } String local = impl.getLocalHostName(); if (security != null) { security.checkConnect(local, -1); } InetAddress localAddr; if (local.equals("localhost")) { // shortcut for "localhost" host name localAddr = impl.loopbackAddress(); } else { // call getAllByName0 without security checks and // without using cached data try { localAddr = getAllByName0(local, null, false, false)[0]; } catch (UnknownHostException uhe) { // Rethrow with a more informative error message. UnknownHostException uhe2 = new UnknownHostException(local + ": " + uhe.getMessage()); uhe2.initCause(uhe); throw uhe2; } } cachedLocalHost = new CachedLocalHost(local, localAddr); return localAddr; } catch (java.lang.SecurityException e) { return impl.loopbackAddress(); } } /** * Perform class load-time initializations. */ private static native void init(); /* * Returns the InetAddress representing anyLocalAddress * (typically 0.0.0.0 or ::0) */ static InetAddress anyLocalAddress() { return impl.anyLocalAddress(); } /* * Load and instantiate an underlying impl class */ static InetAddressImpl loadImpl(String implName) { Object impl = null; /* * Property "impl.prefix" will be prepended to the classname * of the implementation object we instantiate, to which we * delegate the real work (like native methods). This * property can vary across implementations of the java. * classes. The default is an empty String "". */ String prefix = GetPropertyAction.privilegedGetProperty("impl.prefix", ""); try { @SuppressWarnings("deprecation") Object tmp = Class.forName("java.net." + prefix + implName).newInstance(); impl = tmp; } catch (ClassNotFoundException e) { System.err.println("Class not found: java.net." + prefix + implName + ":\ncheck impl.prefix property " + "in your properties file."); } catch (InstantiationException e) { System.err.println("Could not instantiate: java.net." + prefix + implName + ":\ncheck impl.prefix property " + "in your properties file."); } catch (IllegalAccessException e) { System.err.println("Cannot access class: java.net." + prefix + implName + ":\ncheck impl.prefix property " + "in your properties file."); } if (impl == null) { try { @SuppressWarnings("deprecation") Object tmp = Class.forName(implName).newInstance(); impl = tmp; } catch (Exception e) { throw new Error("System property impl.prefix incorrect"); } } return (InetAddressImpl) impl; } private void readObjectNoData() { if (getClass().getClassLoader() != null) { throw new SecurityException("invalid address type"); } } private static final jdk.internal.misc.Unsafe UNSAFE = jdk.internal.misc.Unsafe.getUnsafe(); private static final long FIELDS_OFFSET = UNSAFE.objectFieldOffset(InetAddress.class, "holder"); private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException { if (getClass().getClassLoader() != null) { throw new SecurityException("invalid address type"); } GetField gf = s.readFields(); String host = (String) gf.get("hostName", null); int address = gf.get("address", 0); int family = gf.get("family", 0); if (family != IPv4 && family != IPv6) { throw new InvalidObjectException("invalid address family type: " + family); } InetAddressHolder h = new InetAddressHolder(host, address, family); UNSAFE.putReference(this, FIELDS_OFFSET, h); } /* needed because the serializable fields no longer exist */ /** * @serialField hostName String * @serialField address int * @serialField family int */ private static final ObjectStreamField[] serialPersistentFields = { new ObjectStreamField("hostName", String.class), new ObjectStreamField("address", int.class), new ObjectStreamField("family", int.class), }; private void writeObject(ObjectOutputStream s) throws IOException { if (getClass().getClassLoader() != null) { throw new SecurityException("invalid address type"); } PutField pf = s.putFields(); pf.put("hostName", holder().getHostName()); pf.put("address", holder().getAddress()); pf.put("family", holder().getFamily()); s.writeFields(); } } /* * Simple factory to create the impl */ class InetAddressImplFactory { static InetAddressImpl create() { return InetAddress.loadImpl(isIPv6Supported() ? "Inet6AddressImpl" : "Inet4AddressImpl"); } static native boolean isIPv6Supported(); }