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src/java.base/share/classes/java/net/InetAddress.java

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   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.net;
  27 





  28 import java.util.List;
  29 import java.util.NavigableSet;
  30 import java.util.ArrayList;
  31 import java.util.Objects;
  32 import java.util.Scanner;
  33 import java.io.File;
  34 import java.io.ObjectStreamException;
  35 import java.io.ObjectStreamField;
  36 import java.io.IOException;
  37 import java.io.InvalidObjectException;
  38 import java.io.ObjectInputStream;
  39 import java.io.ObjectInputStream.GetField;
  40 import java.io.ObjectOutputStream;
  41 import java.io.ObjectOutputStream.PutField;
  42 import java.lang.annotation.Native;

  43 import java.util.concurrent.ConcurrentHashMap;
  44 import java.util.concurrent.ConcurrentMap;
  45 import java.util.concurrent.ConcurrentSkipListSet;
  46 import java.util.concurrent.atomic.AtomicLong;
  47 import java.util.Arrays;




  48 
  49 import jdk.internal.access.JavaNetInetAddressAccess;
  50 import jdk.internal.access.SharedSecrets;


  51 import sun.security.action.*;
  52 import sun.net.InetAddressCachePolicy;
  53 import sun.net.util.IPAddressUtil;
  54 import sun.nio.cs.UTF_8;
  55 





  56 /**
  57  * This class represents an Internet Protocol (IP) address.
  58  *
  59  * <p> An IP address is either a 32-bit or 128-bit unsigned number
  60  * used by IP, a lower-level protocol on which protocols like UDP and
  61  * TCP are built. The IP address architecture is defined by <a
  62  * href="http://www.ietf.org/rfc/rfc790.txt"><i>RFC&nbsp;790:
  63  * Assigned Numbers</i></a>, <a
  64  * href="http://www.ietf.org/rfc/rfc1918.txt"> <i>RFC&nbsp;1918:
  65  * Address Allocation for Private Internets</i></a>, <a
  66  * href="http://www.ietf.org/rfc/rfc2365.txt"><i>RFC&nbsp;2365:
  67  * Administratively Scoped IP Multicast</i></a>, and <a
  68  * href="http://www.ietf.org/rfc/rfc2373.txt"><i>RFC&nbsp;2373: IP
  69  * Version 6 Addressing Architecture</i></a>. An instance of an
  70  * InetAddress consists of an IP address and possibly its
  71  * corresponding host name (depending on whether it is constructed
  72  * with a host name or whether it has already done reverse host name
  73  * resolution).
  74  *
  75  * <h2> Address types </h2>

 111  * <p> <i>Link-local</i> addresses are designed to be used for addressing
 112  * on a single link for purposes such as auto-address configuration,
 113  * neighbor discovery, or when no routers are present.
 114  *
 115  * <p> <i>Site-local</i> addresses are designed to be used for addressing
 116  * inside of a site without the need for a global prefix.
 117  *
 118  * <p> <i>Global</i> addresses are unique across the internet.
 119  *
 120  * <h3> Textual representation of IP addresses </h3>
 121  *
 122  * The textual representation of an IP address is address family specific.
 123  *
 124  * <p>
 125  *
 126  * For IPv4 address format, please refer to <A
 127  * HREF="Inet4Address.html#format">Inet4Address#format</A>; For IPv6
 128  * address format, please refer to <A
 129  * HREF="Inet6Address.html#format">Inet6Address#format</A>.
 130  *
 131  * <P>There is a <a href="doc-files/net-properties.html#Ipv4IPv6">couple of
 132  * System Properties</a> affecting how IPv4 and IPv6 addresses are used.</P>
 133  *
 134  * <h3> Host Name Resolution </h3>




 135  *
 136  * Host name-to-IP address <i>resolution</i> is accomplished through
 137  * the use of a combination of local machine configuration information
 138  * and network naming services such as the Domain Name System (DNS)
 139  * and Network Information Service(NIS). The particular naming
 140  * services(s) being used is by default the local machine configured
 141  * one. For any host name, its corresponding IP address is returned.
 142  *
 143  * <p> <i>Reverse name resolution</i> means that for any IP address,
 144  * the host associated with the IP address is returned.
 145  *
 146  * <p> The InetAddress class provides methods to resolve host names to
 147  * their IP addresses and vice versa.










 148  *
 149  * <h3> InetAddress Caching </h3>
 150  *
 151  * The InetAddress class has a cache to store successful as well as
 152  * unsuccessful host name resolutions.
 153  *
 154  * <p> By default, when a security manager is installed, in order to
 155  * protect against DNS spoofing attacks,
 156  * the result of positive host name resolutions are
 157  * cached forever. When a security manager is not installed, the default
 158  * behavior is to cache entries for a finite (implementation dependent)
 159  * period of time. The result of unsuccessful host
 160  * name resolution is cached for a very short period of time (10
 161  * seconds) to improve performance.
 162  *
 163  * <p> If the default behavior is not desired, then a Java security property
 164  * can be set to a different Time-to-live (TTL) value for positive
 165  * caching. Likewise, a system admin can configure a different
 166  * negative caching TTL value when needed.
 167  *
 168  * <p> Two Java security properties control the TTL values used for
 169  *  positive and negative host name resolution caching:

 181  * <dd>Indicates the caching policy for un-successful name lookups
 182  * from the name service. The value is specified as an integer to
 183  * indicate the number of seconds to cache the failure for
 184  * un-successful lookups.
 185  * <p>
 186  * A value of 0 indicates "never cache".
 187  * A value of -1 indicates "cache forever".
 188  * </dd>
 189  * </dl>
 190  *
 191  * @author  Chris Warth
 192  * @see     java.net.InetAddress#getByAddress(byte[])
 193  * @see     java.net.InetAddress#getByAddress(java.lang.String, byte[])
 194  * @see     java.net.InetAddress#getAllByName(java.lang.String)
 195  * @see     java.net.InetAddress#getByName(java.lang.String)
 196  * @see     java.net.InetAddress#getLocalHost()
 197  * @since 1.0
 198  */
 199 public class InetAddress implements java.io.Serializable {
 200 
 201     @Native static final int PREFER_IPV4_VALUE = 0;
 202     @Native static final int PREFER_IPV6_VALUE = 1;
 203     @Native static final int PREFER_SYSTEM_VALUE = 2;
 204 
 205     /**
 206      * Specify the address family: Internet Protocol, Version 4
 207      * @since 1.4
 208      */
 209     @Native static final int IPv4 = 1;
 210 
 211     /**
 212      * Specify the address family: Internet Protocol, Version 6
 213      * @since 1.4
 214      */
 215     @Native static final int IPv6 = 2;
 216 
 217     /* Specify address family preference */
 218     static transient final int preferIPv6Address;
 219 
 220     static class InetAddressHolder {
 221         /**
 222          * Reserve the original application specified hostname.
 223          *
 224          * The original hostname is useful for domain-based endpoint
 225          * identification (see RFC 2818 and RFC 6125).  If an address
 226          * was created with a raw IP address, a reverse name lookup
 227          * may introduce endpoint identification security issue via
 228          * DNS forging.
 229          *
 230          * Oracle JSSE provider is using this original hostname, via
 231          * jdk.internal.misc.JavaNetAccess, for SSL/TLS endpoint identification.
 232          *
 233          * Note: May define a new public method in the future if necessary.
 234          */
 235         String originalHostName;
 236 
 237         InetAddressHolder() {}
 238 
 239         InetAddressHolder(String hostName, int address, int family) {

 271         }
 272 
 273         /**
 274          * Specifies the address family type, for instance, '1' for IPv4
 275          * addresses, and '2' for IPv6 addresses.
 276          */
 277         int family;
 278 
 279         int getFamily() {
 280             return family;
 281         }
 282     }
 283 
 284     /* Used to store the serializable fields of InetAddress */
 285     final transient InetAddressHolder holder;
 286 
 287     InetAddressHolder holder() {
 288         return holder;
 289     }
 290 
 291     /* Used to store the name service provider */
 292     private static transient NameService nameService;



 293 
 294     /**
 295      * Used to store the best available hostname.
 296      * Lazily initialized via a data race; safe because Strings are immutable.
 297      */
 298     private transient String canonicalHostName = null;
 299 
 300     /** use serialVersionUID from JDK 1.0.2 for interoperability */
 301     @java.io.Serial
 302     private static final long serialVersionUID = 3286316764910316507L;
 303 









 304     /*
 305      * Load net library into runtime, and perform initializations.
 306      */
 307     static {
 308         String str = GetPropertyAction.privilegedGetProperty("java.net.preferIPv6Addresses");
 309         if (str == null) {
 310             preferIPv6Address = PREFER_IPV4_VALUE;
 311         } else if (str.equalsIgnoreCase("true")) {
 312             preferIPv6Address = PREFER_IPV6_VALUE;
 313         } else if (str.equalsIgnoreCase("false")) {
 314             preferIPv6Address = PREFER_IPV4_VALUE;
 315         } else if (str.equalsIgnoreCase("system")) {
 316             preferIPv6Address = PREFER_SYSTEM_VALUE;
 317         } else {
 318             preferIPv6Address = PREFER_IPV4_VALUE;
 319         }
 320         jdk.internal.loader.BootLoader.loadLibrary("net");
 321         SharedSecrets.setJavaNetInetAddressAccess(
 322                 new JavaNetInetAddressAccess() {
 323                     public String getOriginalHostName(InetAddress ia) {
 324                         return ia.holder.getOriginalHostName();
 325                     }
 326 
 327                     public InetAddress getByName(String hostName,
 328                                                  InetAddress hostAddress)
 329                         throws UnknownHostException
 330                     {
 331                         return InetAddress.getByName(hostName, hostAddress);
 332                     }
 333 
 334                     public int addressValue(Inet4Address inet4Address) {
 335                         return inet4Address.addressValue();
 336                     }
 337 
 338                     public byte[] addressBytes(Inet6Address inet6Address) {
 339                         return inet6Address.addressBytes();
 340                     }
 341                 }
 342         );
 343         init();
 344     }
 345 





























































































































 346     /**
 347      * Constructor for the Socket.accept() method.
 348      * This creates an empty InetAddress, which is filled in by
 349      * the accept() method.  This InetAddress, however, is not
 350      * put in the address cache, since it is not created by name.
 351      */
 352     InetAddress() {
 353         holder = new InetAddressHolder();
 354     }
 355 
 356     /**
 357      * Replaces the de-serialized object with an Inet4Address object.
 358      *
 359      * @return the alternate object to the de-serialized object.
 360      *
 361      * @throws ObjectStreamException if a new object replacing this
 362      * object could not be created
 363      */
 364     @java.io.Serial
 365     private Object readResolve() throws ObjectStreamException {

 538      * @throws IOException if a network error occurs
 539      * @since 1.5
 540      */
 541     public boolean isReachable(NetworkInterface netif, int ttl,
 542                                int timeout) throws IOException {
 543         if (ttl < 0)
 544             throw new IllegalArgumentException("ttl can't be negative");
 545         if (timeout < 0)
 546             throw new IllegalArgumentException("timeout can't be negative");
 547 
 548         return impl.isReachable(this, timeout, netif, ttl);
 549     }
 550 
 551     /**
 552      * Gets the host name for this IP address.
 553      *
 554      * <p>If this InetAddress was created with a host name,
 555      * this host name will be remembered and returned;
 556      * otherwise, a reverse name lookup will be performed
 557      * and the result will be returned based on the system
 558      * configured name lookup service. If a lookup of the name service
 559      * is required, call
 560      * {@link #getCanonicalHostName() getCanonicalHostName}.
 561      *
 562      * <p>If there is a security manager, its
 563      * {@code checkConnect} method is first called
 564      * with the hostname and {@code -1}
 565      * as its arguments to see if the operation is allowed.
 566      * If the operation is not allowed, it will return
 567      * the textual representation of the IP address.
 568      *
 569      * @return  the host name for this IP address, or if the operation
 570      *    is not allowed by the security check, the textual
 571      *    representation of the IP address.
 572      *
 573      * @see InetAddress#getCanonicalHostName
 574      * @see SecurityManager#checkConnect
 575      */
 576     public String getHostName() {
 577         return getHostName(true);
 578     }

 639     /**
 640      * Returns the hostname for this address.
 641      *
 642      * <p>If there is a security manager, this method first
 643      * calls its {@code checkConnect} method
 644      * with the hostname and {@code -1}
 645      * as its arguments to see if the calling code is allowed to know
 646      * the hostname for this IP address, i.e., to connect to the host.
 647      * If the operation is not allowed, it will return
 648      * the textual representation of the IP address.
 649      *
 650      * @return  the host name for this IP address, or if the operation
 651      *    is not allowed by the security check, the textual
 652      *    representation of the IP address.
 653      *
 654      * @param check make security check if true
 655      *
 656      * @see SecurityManager#checkConnect
 657      */
 658     private static String getHostFromNameService(InetAddress addr, boolean check) {
 659         String host = null;

 660         try {
 661             // first lookup the hostname
 662             host = nameService.getHostByAddr(addr.getAddress());
 663 
 664             /* check to see if calling code is allowed to know
 665              * the hostname for this IP address, ie, connect to the host
 666              */
 667             if (check) {
 668                 @SuppressWarnings("removal")
 669                 SecurityManager sec = System.getSecurityManager();
 670                 if (sec != null) {
 671                     sec.checkConnect(host, -1);
 672                 }
 673             }
 674 
 675             /* now get all the IP addresses for this hostname,
 676              * and make sure one of them matches the original IP
 677              * address. We do this to try and prevent spoofing.
 678              */
 679 
 680             InetAddress[] arr = InetAddress.getAllByName0(host, check);
 681             boolean ok = false;
 682 
 683             if (arr != null) {
 684                 for (int i = 0; !ok && i < arr.length; i++) {
 685                     ok = addr.equals(arr[i]);
 686                 }
 687             }
 688 
 689             //XXX: if it looks like a spoof just return the address?
 690             if (!ok) {
 691                 host = addr.getHostAddress();
 692                 return host;
 693             }
 694         } catch (SecurityException e) {



 695             host = addr.getHostAddress();
 696         } catch (UnknownHostException e) {
 697             host = addr.getHostAddress();
 698             // let next provider resolve the hostname
 699         }
 700         return host;
 701     }
 702 
 703     /**
 704      * Returns the raw IP address of this {@code InetAddress}
 705      * object. The result is in network byte order: the highest order
 706      * byte of the address is in {@code getAddress()[0]}.
 707      *
 708      * @return  the raw IP address of this object.
 709      */
 710     public byte[] getAddress() {
 711         return null;
 712     }
 713 
 714     /**
 715      * Returns the IP address string in textual presentation.
 716      *
 717      * @return  the raw IP address in a string format.
 718      * @since   1.0.2

 738      * <p>
 739      * Two instances of {@code InetAddress} represent the same IP
 740      * address if the length of the byte arrays returned by
 741      * {@code getAddress} is the same for both, and each of the
 742      * array components is the same for the byte arrays.
 743      *
 744      * @param   obj   the object to compare against.
 745      * @return  {@code true} if the objects are the same;
 746      *          {@code false} otherwise.
 747      * @see     java.net.InetAddress#getAddress()
 748      */
 749     public boolean equals(Object obj) {
 750         return false;
 751     }
 752 
 753     /**
 754      * Converts this IP address to a {@code String}. The
 755      * string returned is of the form: hostname / literal IP
 756      * address.
 757      *
 758      * If the host name is unresolved, no reverse name service lookup
 759      * is performed. The hostname part will be represented by an empty string.

 760      *
 761      * @return  a string representation of this IP address.
 762      */
 763     public String toString() {
 764         String hostName = holder().getHostName();
 765         return Objects.toString(hostName, "")
 766             + "/" + getHostAddress();
 767     }
 768 
 769     // mapping from host name to Addresses - either NameServiceAddresses (while
 770     // still being looked-up by NameService(s)) or CachedAddresses when cached
 771     private static final ConcurrentMap<String, Addresses> cache =
 772         new ConcurrentHashMap<>();
 773 
 774     // CachedAddresses that have to expire are kept ordered in this NavigableSet
 775     // which is scanned on each access
 776     private static final NavigableSet<CachedAddresses> expirySet =
 777         new ConcurrentSkipListSet<>();
 778 
 779     // common interface

 804         }
 805 
 806         @Override
 807         public int compareTo(CachedAddresses other) {
 808             // natural order is expiry time -
 809             // compare difference of expiry times rather than
 810             // expiry times directly, to avoid possible overflow.
 811             // (see System.nanoTime() recommendations...)
 812             long diff = this.expiryTime - other.expiryTime;
 813             if (diff < 0L) return -1;
 814             if (diff > 0L) return 1;
 815             // ties are broken using unique id
 816             return Long.compare(this.id, other.id);
 817         }
 818     }
 819 
 820     // a name service lookup based Addresses implementation which replaces itself
 821     // in cache when the result is obtained
 822     private static final class NameServiceAddresses implements Addresses {
 823         private final String host;
 824         private final InetAddress reqAddr;
 825 
 826         NameServiceAddresses(String host, InetAddress reqAddr) {
 827             this.host = host;
 828             this.reqAddr = reqAddr;
 829         }
 830 
 831         @Override
 832         public InetAddress[] get() throws UnknownHostException {
 833             Addresses addresses;
 834             // only one thread is doing lookup to name service
 835             // for particular host at any time.
 836             synchronized (this) {
 837                 // re-check that we are still us + re-install us if slot empty
 838                 addresses = cache.putIfAbsent(host, this);
 839                 if (addresses == null) {
 840                     // this can happen when we were replaced by CachedAddresses in
 841                     // some other thread, then CachedAddresses expired and were
 842                     // removed from cache while we were waiting for lock...
 843                     addresses = this;
 844                 }
 845                 // still us ?
 846                 if (addresses == this) {
 847                     // lookup name services
 848                     InetAddress[] inetAddresses;
 849                     UnknownHostException ex;
 850                     int cachePolicy;
 851                     try {
 852                         inetAddresses = getAddressesFromNameService(host, reqAddr);
 853                         ex = null;
 854                         cachePolicy = InetAddressCachePolicy.get();
 855                     } catch (UnknownHostException uhe) {
 856                         inetAddresses = null;
 857                         ex = uhe;
 858                         cachePolicy = InetAddressCachePolicy.getNegative();
 859                     }
 860                     // remove or replace us with cached addresses according to cachePolicy
 861                     if (cachePolicy == InetAddressCachePolicy.NEVER) {
 862                         cache.remove(host, this);
 863                     } else {
 864                         CachedAddresses cachedAddresses = new CachedAddresses(
 865                             host,
 866                             inetAddresses,
 867                             cachePolicy == InetAddressCachePolicy.FOREVER
 868                             ? 0L
 869                             // cachePolicy is in [s] - we need [ns]
 870                             : System.nanoTime() + 1000_000_000L * cachePolicy
 871                         );
 872                         if (cache.replace(host, this, cachedAddresses) &&
 873                             cachePolicy != InetAddressCachePolicy.FOREVER) {
 874                             // schedule expiry
 875                             expirySet.add(cachedAddresses);
 876                         }
 877                     }
 878                     if (inetAddresses == null) {
 879                         throw ex == null ? new UnknownHostException(host) : ex;
 880                     }
 881                     return inetAddresses;
 882                 }
 883                 // else addresses != this
 884             }
 885             // delegate to different addresses when we are already replaced
 886             // but outside of synchronized block to avoid any chance of dead-locking
 887             return addresses.get();
 888         }
 889     }
 890 
 891     /**
 892      * NameService provides host and address lookup service
 893      *
 894      * @since 9
 895      */
 896     private interface NameService {
 897 
 898         /**
 899          * Lookup a host mapping by name. Retrieve the IP addresses
 900          * associated with a host
 901          *
 902          * @param host the specified hostname
 903          * @return array of IP addresses for the requested host
 904          * @throws UnknownHostException
 905          *             if no IP address for the {@code host} could be found
 906          */
 907         InetAddress[] lookupAllHostAddr(String host)
 908                 throws UnknownHostException;
 909 
 910         /**
 911          * Lookup the host corresponding to the IP address provided
 912          *
 913          * @param addr byte array representing an IP address
 914          * @return {@code String} representing the host name mapping
 915          * @throws UnknownHostException
 916          *             if no host found for the specified IP address
 917          */
 918         String getHostByAddr(byte[] addr) throws UnknownHostException;
 919 
 920     }
 921 
 922     /**
 923      * The default NameService implementation, which delegates to the underlying
 924      * OS network libraries to resolve host address mappings.
 925      *
 926      * @since 9
 927      */
 928     private static final class PlatformNameService implements NameService {
 929 
 930         public InetAddress[] lookupAllHostAddr(String host)
 931             throws UnknownHostException
 932         {
 933             return impl.lookupAllHostAddr(host);

 934         }
 935 
 936         public String getHostByAddr(byte[] addr)
 937             throws UnknownHostException
 938         {



 939             return impl.getHostByAddr(addr);
 940         }
 941     }
 942 
 943     /**
 944      * The HostsFileNameService provides host address mapping
 945      * by reading the entries in a hosts file, which is specified by
 946      * {@code jdk.net.hosts.file} system property
 947      *
 948      * <p>The file format is that which corresponds with the /etc/hosts file
 949      * IP Address host alias list.
 950      *
 951      * <p>When the file lookup is enabled it replaces the default NameService
 952      * implementation
 953      *
 954      * @since 9
 955      */
 956     private static final class HostsFileNameService implements NameService {
 957 
 958         private static final InetAddress[] EMPTY_ARRAY = new InetAddress[0];
 959 
 960         // Specify if only IPv4 addresses should be returned by HostsFileService implementation
 961         private static final boolean preferIPv4Stack = Boolean.parseBoolean(
 962                 GetPropertyAction.privilegedGetProperty("java.net.preferIPv4Stack"));
 963 
 964         private final String hostsFile;
 965 
 966         public HostsFileNameService(String hostsFileName) {
 967             this.hostsFile = hostsFileName;
 968         }
 969 
 970         /**
 971          * Lookup the host name  corresponding to the IP address provided.
 972          * Search the configured host file a host name corresponding to
 973          * the specified IP address.
 974          *
 975          * @param addr byte array representing an IP address
 976          * @return {@code String} representing the host name mapping
 977          * @throws UnknownHostException
 978          *             if no host found for the specified IP address
 979          */
 980         @Override
 981         public String getHostByAddr(byte[] addr) throws UnknownHostException {
 982             String hostEntry;
 983             String host = null;





 984 
 985             try (Scanner hostsFileScanner = new Scanner(new File(hostsFile),
 986                                                         UTF_8.INSTANCE))
 987             {
 988                 while (hostsFileScanner.hasNextLine()) {
 989                     hostEntry = hostsFileScanner.nextLine();
 990                     if (!hostEntry.startsWith("#")) {
 991                         hostEntry = removeComments(hostEntry);
 992                         String[] mapping = hostEntry.split("\\s+");
 993                         if (mapping.length >= 2 &&
 994                             Arrays.equals(addr, createAddressByteArray(mapping[0]))) {
 995                             host = mapping[1];
 996                             break;
 997                         }
 998                     }
 999                 }
1000             } catch (IOException e) {
1001                 throw new UnknownHostException("Unable to resolve address "
1002                         + Arrays.toString(addr) + " as hosts file " + hostsFile
1003                         + " not found ");
1004             }
1005 
1006             if ((host == null) || (host.isEmpty()) || (host.equals(" "))) {
1007                 throw new UnknownHostException("Requested address "
1008                         + Arrays.toString(addr)
1009                         + " resolves to an invalid entry in hosts file "
1010                         + hostsFile);
1011             }
1012             return host;
1013         }
1014 
1015         /**
1016          * <p>Lookup a host mapping by name. Retrieve the IP addresses
1017          * associated with a host.
1018          *
1019          * <p>Search the configured hosts file for the addresses associated
1020          * with the specified host name.
1021          *
1022          * @param host the specified hostname
1023          * @return array of IP addresses for the requested host


1024          * @throws UnknownHostException
1025          *             if no IP address for the {@code host} could be found
1026          */
1027         public InetAddress[] lookupAllHostAddr(String host)
1028                 throws UnknownHostException {
1029             String hostEntry;
1030             String addrStr;
1031             byte addr[];



1032             List<InetAddress> inetAddresses = new ArrayList<>();
1033             List<InetAddress> inet4Addresses = new ArrayList<>();
1034             List<InetAddress> inet6Addresses = new ArrayList<>();



1035 
1036             // lookup the file and create a list InetAddress for the specified host
1037             try (Scanner hostsFileScanner = new Scanner(new File(hostsFile),
1038                                                         UTF_8.INSTANCE)) {
1039                 while (hostsFileScanner.hasNextLine()) {
1040                     hostEntry = hostsFileScanner.nextLine();
1041                     if (!hostEntry.startsWith("#")) {
1042                         hostEntry = removeComments(hostEntry);
1043                         if (hostEntry.contains(host)) {
1044                             addrStr = extractHostAddr(hostEntry, host);
1045                             if ((addrStr != null) && (!addrStr.isEmpty())) {
1046                                 addr = createAddressByteArray(addrStr);
1047                                 if (addr != null) {
1048                                     InetAddress address = InetAddress.getByAddress(host, addr);
1049                                     inetAddresses.add(address);
1050                                     if (address instanceof Inet4Address) {
1051                                         inet4Addresses.add(address);
1052                                     }
1053                                     if (address instanceof Inet6Address) {
1054                                         inet6Addresses.add(address);
1055                                     }
1056                                 }
1057                             }
1058                         }
1059                     }
1060                 }
1061             } catch (IOException e) {
1062                 throw new UnknownHostException("Unable to resolve host " + host
1063                         + " as hosts file " + hostsFile + " not found ");
1064             }
1065 
1066             List<InetAddress> res;
1067             // If "preferIPv4Stack" system property is set to "true" then return
1068             // only IPv4 addresses
1069             if (preferIPv4Stack) {
1070                 res = inet4Addresses;
1071             } else {
1072                 // Otherwise, analyse "preferIPv6Addresses" value
1073                 res = switch (preferIPv6Address) {
1074                     case PREFER_IPV4_VALUE -> concatAddresses(inet4Addresses, inet6Addresses);
1075                     case PREFER_IPV6_VALUE -> concatAddresses(inet6Addresses, inet4Addresses);
1076                     default -> inetAddresses;
1077                 };
1078             }
1079 
1080             if (res.isEmpty()) {
1081                 throw new UnknownHostException("Unable to resolve host " + host
1082                         + " in hosts file " + hostsFile);
1083             }
1084             return res.toArray(EMPTY_ARRAY);











1085         }
1086 
1087         private static List<InetAddress> concatAddresses(List<InetAddress> firstPart,
1088                                                          List<InetAddress> secondPart) {
1089             List<InetAddress> result = new ArrayList<>(firstPart);
1090             result.addAll(secondPart);
1091             return result;



1092         }
1093 
1094         private String removeComments(String hostsEntry) {
1095             String filteredEntry = hostsEntry;
1096             int hashIndex;
1097 
1098             if ((hashIndex = hostsEntry.indexOf("#")) != -1) {
1099                 filteredEntry = hostsEntry.substring(0, hashIndex);
1100             }
1101             return filteredEntry;
1102         }
1103 
1104         private byte [] createAddressByteArray(String addrStr) {
1105             byte[] addrArray;
1106             // check if IPV4 address - most likely
1107             addrArray = IPAddressUtil.textToNumericFormatV4(addrStr);
1108             if (addrArray == null) {
1109                 addrArray = IPAddressUtil.textToNumericFormatV6(addrStr);
1110             }
1111             return addrArray;

1113 
1114         /** host to ip address mapping */
1115         private String extractHostAddr(String hostEntry, String host) {
1116             String[] mapping = hostEntry.split("\\s+");
1117             String hostAddr = null;
1118 
1119             if (mapping.length >= 2) {
1120                 // look at the host aliases
1121                 for (int i = 1; i < mapping.length; i++) {
1122                     if (mapping[i].equalsIgnoreCase(host)) {
1123                         hostAddr = mapping[0];
1124                     }
1125                 }
1126             }
1127             return hostAddr;
1128         }
1129     }
1130 
1131     static final InetAddressImpl  impl;
1132 






1133     static {
1134         // create the impl
1135         impl = InetAddressImplFactory.create();
1136 
1137         // create name service
1138         nameService = createNameService();



1139     }
1140 
1141     /**
1142      * Create an instance of the NameService interface based on
1143      * the setting of the {@code jdk.net.hosts.file} system property.
1144      *
1145      * <p>The default NameService is the PlatformNameService, which typically
1146      * delegates name and address resolution calls to the underlying
1147      * OS network libraries.
1148      *
1149      * <p> A HostsFileNameService is created if the {@code jdk.net.hosts.file}
1150      * system property is set. If the specified file doesn't exist, the name or
1151      * address lookup will result in an UnknownHostException. Thus, non existent
1152      * hosts file is handled as if the file is empty.
1153      *
1154      * @return a NameService
1155      */
1156     private static NameService createNameService() {
1157 
1158         String hostsFileName =
1159                 GetPropertyAction.privilegedGetProperty("jdk.net.hosts.file");
1160         NameService theNameService;
1161         if (hostsFileName != null) {
1162             theNameService = new HostsFileNameService(hostsFileName);
1163         } else {
1164             theNameService = new PlatformNameService();
1165         }
1166         return theNameService;
1167     }
1168 
1169     /**
1170      * Creates an InetAddress based on the provided host name and IP address.
1171      * No name service is checked for the validity of the address.

1172      *
1173      * <p> The host name can either be a machine name, such as
1174      * "{@code www.example.com}", or a textual representation of its IP
1175      * address.
1176      * <p> No validity checking is done on the host name either.
1177      *
1178      * <p> If addr specifies an IPv4 address an instance of Inet4Address
1179      * will be returned; otherwise, an instance of Inet6Address
1180      * will be returned.
1181      *
1182      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
1183      * must be 16 bytes long
1184      *
1185      * @param host the specified host
1186      * @param addr the raw IP address in network byte order
1187      * @return  an InetAddress object created from the raw IP address.
1188      * @throws     UnknownHostException  if IP address is of illegal length
1189      * @since 1.4
1190      */
1191     public static InetAddress getByAddress(String host, byte[] addr)

1234      * section&nbsp;2.5.3.
1235      *
1236      * <p> If there is a security manager, and {@code host} is not {@code null}
1237      * or {@code host.length() } is not equal to zero, the security manager's
1238      * {@code checkConnect} method is called with the hostname and {@code -1}
1239      * as its arguments to determine if the operation is allowed.
1240      *
1241      * @param      host   the specified host, or {@code null}.
1242      * @return     an IP address for the given host name.
1243      * @throws     UnknownHostException  if no IP address for the
1244      *               {@code host} could be found, or if a scope_id was specified
1245      *               for a global IPv6 address.
1246      * @throws     SecurityException if a security manager exists
1247      *             and its checkConnect method doesn't allow the operation
1248      */
1249     public static InetAddress getByName(String host)
1250         throws UnknownHostException {
1251         return InetAddress.getAllByName(host)[0];
1252     }
1253 
1254     // called from deployment cache manager
1255     private static InetAddress getByName(String host, InetAddress reqAddr)
1256         throws UnknownHostException {
1257         return InetAddress.getAllByName(host, reqAddr)[0];
1258     }
1259 
1260     /**
1261      * Given the name of a host, returns an array of its IP addresses,
1262      * based on the configured name service on the system.
1263      *
1264      * <p> The host name can either be a machine name, such as
1265      * "{@code www.example.com}", or a textual representation of its IP
1266      * address. If a literal IP address is supplied, only the
1267      * validity of the address format is checked.
1268      *
1269      * <p> For {@code host} specified in <i>literal IPv6 address</i>,
1270      * either the form defined in RFC 2732 or the literal IPv6 address
1271      * format defined in RFC 2373 is accepted. A literal IPv6 address may
1272      * also be qualified by appending a scoped zone identifier or scope_id.
1273      * The syntax and usage of scope_ids is described
1274      * <a href="Inet6Address.html#scoped">here</a>.
1275      *
1276      * <p> If the host is {@code null} or {@code host.length()} is equal
1277      * to zero, then an {@code InetAddress} representing an address of the
1278      * loopback interface is returned.
1279      * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
1280      * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
1281      * section&nbsp;2.5.3. </p>
1282      *
1283      * <p> If there is a security manager, and {@code host} is not {@code null}
1284      * or {@code host.length() } is not equal to zero, the security manager's
1285      * {@code checkConnect} method is called with the hostname and {@code -1}
1286      * as its arguments to determine if the operation is allowed.
1287      *
1288      * @param      host   the name of the host, or {@code null}.
1289      * @return     an array of all the IP addresses for a given host name.
1290      *
1291      * @throws     UnknownHostException  if no IP address for the
1292      *               {@code host} could be found, or if a scope_id was specified
1293      *               for a global IPv6 address.
1294      * @throws     SecurityException  if a security manager exists and its
1295      *               {@code checkConnect} method doesn't allow the operation.
1296      *
1297      * @see SecurityManager#checkConnect
1298      */
1299     public static InetAddress[] getAllByName(String host)
1300         throws UnknownHostException {
1301         return getAllByName(host, null);
1302     }
1303 
1304     private static InetAddress[] getAllByName(String host, InetAddress reqAddr)
1305         throws UnknownHostException {
1306 
1307         if (host == null || host.isEmpty()) {
1308             InetAddress[] ret = new InetAddress[1];
1309             ret[0] = impl.loopbackAddress();
1310             return ret;
1311         }
1312 
1313         boolean ipv6Expected = false;
1314         if (host.charAt(0) == '[') {
1315             // This is supposed to be an IPv6 literal
1316             if (host.length() > 2 && host.charAt(host.length()-1) == ']') {
1317                 host = host.substring(1, host.length() -1);
1318                 ipv6Expected = true;
1319             } else {
1320                 // This was supposed to be a IPv6 address, but it's not!
1321                 throw new UnknownHostException(host + ": invalid IPv6 address");
1322             }
1323         }
1324 
1325         // if host is an IP address, we won't do further lookup

1347                 // Means an IPv4 literal between brackets!
1348                 throw new UnknownHostException("["+host+"]");
1349             }
1350             InetAddress[] ret = new InetAddress[1];
1351             if(addr != null) {
1352                 if (addr.length == Inet4Address.INADDRSZ) {
1353                     ret[0] = new Inet4Address(null, addr);
1354                 } else {
1355                     if (ifname != null) {
1356                         ret[0] = new Inet6Address(null, addr, ifname);
1357                     } else {
1358                         ret[0] = new Inet6Address(null, addr, numericZone);
1359                     }
1360                 }
1361                 return ret;
1362             }
1363         } else if (ipv6Expected) {
1364             // We were expecting an IPv6 Literal, but got something else
1365             throw new UnknownHostException("["+host+"]");
1366         }
1367         return getAllByName0(host, reqAddr, true, true);
1368     }
1369 
1370     /**
1371      * Returns the loopback address.
1372      * <p>
1373      * The InetAddress returned will represent the IPv4
1374      * loopback address, 127.0.0.1, or the IPv6 loopback
1375      * address, ::1. The IPv4 loopback address returned
1376      * is only one of many in the form 127.*.*.*
1377      *
1378      * @return  the InetAddress loopback instance.
1379      * @since 1.7
1380      */
1381     public static InetAddress getLoopbackAddress() {
1382         return impl.loopbackAddress();
1383     }
1384 
1385 
1386     /**
1387      * check if the literal address string has %nn appended

1397         if (percent == -1) {
1398             return -1;
1399         }
1400         for (int i=percent+1; i<slen; i++) {
1401             char c = s.charAt(i);
1402             if (c == ']') {
1403                 if (i == percent+1) {
1404                     /* empty per-cent field */
1405                     return -1;
1406                 }
1407                 break;
1408             }
1409             if ((digit = Character.digit (c, 10)) < 0) {
1410                 return -1;
1411             }
1412             zone = (zone * 10) + digit;
1413         }
1414         return zone;
1415     }
1416 
1417     private static InetAddress[] getAllByName0 (String host)
1418         throws UnknownHostException
1419     {
1420         return getAllByName0(host, true);
1421     }
1422 
1423     /**
1424      * package private so SocketPermission can call it
1425      */
1426     static InetAddress[] getAllByName0 (String host, boolean check)
1427         throws UnknownHostException  {
1428         return getAllByName0 (host, null, check, true);
1429     }
1430 
1431     /**
1432      * Designated lookup method.
1433      *
1434      * @param host host name to look up
1435      * @param reqAddr requested address to be the 1st in returned array
1436      * @param check perform security check
1437      * @param useCache use cached value if not expired else always
1438      *                 perform name service lookup (and cache the result)
1439      * @return array of InetAddress(es)
1440      * @throws UnknownHostException if host name is not found
1441      */
1442     private static InetAddress[] getAllByName0(String host,
1443                                                InetAddress reqAddr,
1444                                                boolean check,
1445                                                boolean useCache)
1446         throws UnknownHostException  {
1447 
1448         /* If it gets here it is presumed to be a hostname */
1449 
1450         /* make sure the connection to the host is allowed, before we
1451          * give out a hostname
1452          */
1453         if (check) {
1454             @SuppressWarnings("removal")
1455             SecurityManager security = System.getSecurityManager();
1456             if (security != null) {
1457                 security.checkConnect(host, -1);
1458             }
1459         }
1460 
1461         // remove expired addresses from cache - expirySet keeps them ordered
1462         // by expiry time so we only need to iterate the prefix of the NavigableSet...
1463         long now = System.nanoTime();

1481         // look-up or remove from cache
1482         Addresses addrs;
1483         if (useCache) {
1484             addrs = cache.get(host);
1485         } else {
1486             addrs = cache.remove(host);
1487             if (addrs != null) {
1488                 if (addrs instanceof CachedAddresses) {
1489                     // try removing from expirySet too if CachedAddresses
1490                     expirySet.remove(addrs);
1491                 }
1492                 addrs = null;
1493             }
1494         }
1495 
1496         if (addrs == null) {
1497             // create a NameServiceAddresses instance which will look up
1498             // the name service and install it within cache...
1499             Addresses oldAddrs = cache.putIfAbsent(
1500                 host,
1501                 addrs = new NameServiceAddresses(host, reqAddr)
1502             );
1503             if (oldAddrs != null) { // lost putIfAbsent race
1504                 addrs = oldAddrs;
1505             }
1506         }
1507 
1508         // ask Addresses to get an array of InetAddress(es) and clone it
1509         return addrs.get().clone();
1510     }
1511 
1512     static InetAddress[] getAddressesFromNameService(String host, InetAddress reqAddr)
1513             throws UnknownHostException {
1514         InetAddress[] addresses = null;
1515         UnknownHostException ex = null;
1516 

1517         try {
1518             addresses = nameService.lookupAllHostAddr(host);
1519         } catch (UnknownHostException uhe) {
1520             if (host.equalsIgnoreCase("localhost")) {
1521                 addresses = new InetAddress[]{impl.loopbackAddress()};
1522             } else {
1523                 ex = uhe;



1524             }
1525         }
1526 
1527         if (addresses == null) {

1528             throw ex == null ? new UnknownHostException(host) : ex;
1529         }
1530 
1531         // More to do?
1532         if (reqAddr != null && addresses.length > 1 && !addresses[0].equals(reqAddr)) {
1533             // Find it?
1534             int i = 1;
1535             for (; i < addresses.length; i++) {
1536                 if (addresses[i].equals(reqAddr)) {
1537                     break;
1538                 }
1539             }
1540             // Rotate
1541             if (i < addresses.length) {
1542                 InetAddress tmp, tmp2 = reqAddr;
1543                 for (int j = 0; j < i; j++) {
1544                     tmp = addresses[j];
1545                     addresses[j] = tmp2;
1546                     tmp2 = tmp;
1547                 }
1548                 addresses[i] = tmp2;
1549             }
1550         }
1551 
1552         return addresses;
1553     }
1554 
1555     /**
1556      * Returns an {@code InetAddress} object given the raw IP address .
1557      * The argument is in network byte order: the highest order
1558      * byte of the address is in {@code getAddress()[0]}.
1559      *
1560      * <p> This method doesn't block, i.e. no reverse name service lookup
1561      * is performed.
1562      *
1563      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
1564      * must be 16 bytes long
1565      *
1566      * @param addr the raw IP address in network byte order
1567      * @return  an InetAddress object created from the raw IP address.
1568      * @throws     UnknownHostException  if IP address is of illegal length
1569      * @since 1.4
1570      */
1571     public static InetAddress getByAddress(byte[] addr)
1572         throws UnknownHostException {
1573         return getByAddress(null, addr);
1574     }
1575 
1576     private static final class CachedLocalHost {
1577         final String host;
1578         final InetAddress addr;
1579         final long expiryTime = System.nanoTime() + 5000_000_000L; // now + 5s;
1580 
1581         CachedLocalHost(String host, InetAddress addr) {

1620                 if (security != null) {
1621                     security.checkConnect(clh.host, -1);
1622                 }
1623                 return clh.addr;
1624             }
1625 
1626             String local = impl.getLocalHostName();
1627 
1628             if (security != null) {
1629                 security.checkConnect(local, -1);
1630             }
1631 
1632             InetAddress localAddr;
1633             if (local.equals("localhost")) {
1634                 // shortcut for "localhost" host name
1635                 localAddr = impl.loopbackAddress();
1636             } else {
1637                 // call getAllByName0 without security checks and
1638                 // without using cached data
1639                 try {
1640                     localAddr = getAllByName0(local, null, false, false)[0];
1641                 } catch (UnknownHostException uhe) {
1642                     // Rethrow with a more informative error message.
1643                     UnknownHostException uhe2 =
1644                         new UnknownHostException(local + ": " +
1645                                                  uhe.getMessage());
1646                     uhe2.initCause(uhe);
1647                     throw uhe2;
1648                 }
1649             }
1650             cachedLocalHost = new CachedLocalHost(local, localAddr);
1651             return localAddr;
1652         } catch (java.lang.SecurityException e) {
1653             return impl.loopbackAddress();
1654         }
1655     }
1656 
1657     /**
1658      * Perform class load-time initializations.
1659      */
1660     private static native void init();

   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.net;
  27 
  28 import java.net.spi.InetAddressResolver;
  29 import java.net.spi.InetAddressResolverProvider;
  30 import java.net.spi.InetAddressResolver.LookupPolicy;
  31 import java.security.AccessController;
  32 import java.security.PrivilegedAction;
  33 import java.util.List;
  34 import java.util.NavigableSet;
  35 import java.util.ArrayList;
  36 import java.util.Objects;
  37 import java.util.Scanner;
  38 import java.io.File;
  39 import java.io.ObjectStreamException;
  40 import java.io.ObjectStreamField;
  41 import java.io.IOException;
  42 import java.io.InvalidObjectException;
  43 import java.io.ObjectInputStream;
  44 import java.io.ObjectInputStream.GetField;
  45 import java.io.ObjectOutputStream;
  46 import java.io.ObjectOutputStream.PutField;
  47 import java.lang.annotation.Native;
  48 import java.util.ServiceLoader;
  49 import java.util.concurrent.ConcurrentHashMap;
  50 import java.util.concurrent.ConcurrentMap;
  51 import java.util.concurrent.ConcurrentSkipListSet;
  52 import java.util.concurrent.atomic.AtomicLong;
  53 import java.util.Arrays;
  54 import java.util.concurrent.locks.ReentrantLock;
  55 import java.util.stream.Stream;
  56 
  57 import jdk.internal.misc.VM;
  58 
  59 import jdk.internal.access.JavaNetInetAddressAccess;
  60 import jdk.internal.access.SharedSecrets;
  61 import jdk.internal.vm.annotation.Stable;
  62 import sun.net.ResolverProviderConfiguration;
  63 import sun.security.action.*;
  64 import sun.net.InetAddressCachePolicy;
  65 import sun.net.util.IPAddressUtil;
  66 import sun.nio.cs.UTF_8;
  67 
  68 import static java.net.spi.InetAddressResolver.LookupPolicy.IPV4;
  69 import static java.net.spi.InetAddressResolver.LookupPolicy.IPV4_FIRST;
  70 import static java.net.spi.InetAddressResolver.LookupPolicy.IPV6;
  71 import static java.net.spi.InetAddressResolver.LookupPolicy.IPV6_FIRST;
  72 
  73 /**
  74  * This class represents an Internet Protocol (IP) address.
  75  *
  76  * <p> An IP address is either a 32-bit or 128-bit unsigned number
  77  * used by IP, a lower-level protocol on which protocols like UDP and
  78  * TCP are built. The IP address architecture is defined by <a
  79  * href="http://www.ietf.org/rfc/rfc790.txt"><i>RFC&nbsp;790:
  80  * Assigned Numbers</i></a>, <a
  81  * href="http://www.ietf.org/rfc/rfc1918.txt"> <i>RFC&nbsp;1918:
  82  * Address Allocation for Private Internets</i></a>, <a
  83  * href="http://www.ietf.org/rfc/rfc2365.txt"><i>RFC&nbsp;2365:
  84  * Administratively Scoped IP Multicast</i></a>, and <a
  85  * href="http://www.ietf.org/rfc/rfc2373.txt"><i>RFC&nbsp;2373: IP
  86  * Version 6 Addressing Architecture</i></a>. An instance of an
  87  * InetAddress consists of an IP address and possibly its
  88  * corresponding host name (depending on whether it is constructed
  89  * with a host name or whether it has already done reverse host name
  90  * resolution).
  91  *
  92  * <h2> Address types </h2>

 128  * <p> <i>Link-local</i> addresses are designed to be used for addressing
 129  * on a single link for purposes such as auto-address configuration,
 130  * neighbor discovery, or when no routers are present.
 131  *
 132  * <p> <i>Site-local</i> addresses are designed to be used for addressing
 133  * inside of a site without the need for a global prefix.
 134  *
 135  * <p> <i>Global</i> addresses are unique across the internet.
 136  *
 137  * <h3> Textual representation of IP addresses </h3>
 138  *
 139  * The textual representation of an IP address is address family specific.
 140  *
 141  * <p>
 142  *
 143  * For IPv4 address format, please refer to <A
 144  * HREF="Inet4Address.html#format">Inet4Address#format</A>; For IPv6
 145  * address format, please refer to <A
 146  * HREF="Inet6Address.html#format">Inet6Address#format</A>.
 147  *
 148  * <p> There is a <a href="doc-files/net-properties.html#Ipv4IPv6">couple of
 149  * System Properties</a> affecting how IPv4 and IPv6 addresses are used.
 150  *
 151  * <h2 id="host-name-resolution"> Host Name Resolution </h2>
 152  *
 153  * <p> The InetAddress class provides methods to resolve host names to
 154  * their IP addresses and vice versa. The actual resolution is delegated to an
 155  * {@linkplain InetAddressResolver InetAddress resolver}.
 156  *
 157  * <p> <i>Host name-to-IP address resolution</i> maps a host name to an IP address.
 158  * For any host name, its corresponding IP address is returned.




 159  *
 160  * <p> <i>Reverse name resolution</i> means that for any IP address,
 161  * the host associated with the IP address is returned.
 162  *
 163  * <p id="built-in-resolver"> The built-in InetAddress resolver implementation does
 164  * host name-to-IP address resolution and vice versa through the use of
 165  * a combination of local machine configuration information and network
 166  * naming services such as the Domain Name System (DNS) and the Lightweight Directory
 167  * Access Protocol (LDAP).
 168  * The particular naming services that the built-in resolver uses by default
 169  * depends on the configuration of the local machine.
 170  *
 171  * <p> {@code InetAddress} has a service provider mechanism for InetAddress resolvers
 172  * that allows a custom InetAddress resolver to be used instead of the built-in implementation.
 173  * {@link InetAddressResolverProvider} is the service provider class. Its API docs provide all the
 174  * details on this mechanism.
 175  *
 176  * <h2> InetAddress Caching </h2>
 177  *
 178  * The InetAddress class has a cache to store successful as well as
 179  * unsuccessful host name resolutions.
 180  *
 181  * <p> By default, when a security manager is installed, in order to
 182  * protect against DNS spoofing attacks,
 183  * the result of positive host name resolutions are
 184  * cached forever. When a security manager is not installed, the default
 185  * behavior is to cache entries for a finite (implementation dependent)
 186  * period of time. The result of unsuccessful host
 187  * name resolution is cached for a very short period of time (10
 188  * seconds) to improve performance.
 189  *
 190  * <p> If the default behavior is not desired, then a Java security property
 191  * can be set to a different Time-to-live (TTL) value for positive
 192  * caching. Likewise, a system admin can configure a different
 193  * negative caching TTL value when needed.
 194  *
 195  * <p> Two Java security properties control the TTL values used for
 196  *  positive and negative host name resolution caching:

 208  * <dd>Indicates the caching policy for un-successful name lookups
 209  * from the name service. The value is specified as an integer to
 210  * indicate the number of seconds to cache the failure for
 211  * un-successful lookups.
 212  * <p>
 213  * A value of 0 indicates "never cache".
 214  * A value of -1 indicates "cache forever".
 215  * </dd>
 216  * </dl>
 217  *
 218  * @author  Chris Warth
 219  * @see     java.net.InetAddress#getByAddress(byte[])
 220  * @see     java.net.InetAddress#getByAddress(java.lang.String, byte[])
 221  * @see     java.net.InetAddress#getAllByName(java.lang.String)
 222  * @see     java.net.InetAddress#getByName(java.lang.String)
 223  * @see     java.net.InetAddress#getLocalHost()
 224  * @since 1.0
 225  */
 226 public class InetAddress implements java.io.Serializable {
 227 




 228     /**
 229      * Specify the address family: Internet Protocol, Version 4
 230      * @since 1.4
 231      */
 232     @Native static final int IPv4 = 1;
 233 
 234     /**
 235      * Specify the address family: Internet Protocol, Version 6
 236      * @since 1.4
 237      */
 238     @Native static final int IPv6 = 2;
 239 



 240     static class InetAddressHolder {
 241         /**
 242          * Reserve the original application specified hostname.
 243          *
 244          * The original hostname is useful for domain-based endpoint
 245          * identification (see RFC 2818 and RFC 6125).  If an address
 246          * was created with a raw IP address, a reverse name lookup
 247          * may introduce endpoint identification security issue via
 248          * DNS forging.
 249          *
 250          * Oracle JSSE provider is using this original hostname, via
 251          * jdk.internal.misc.JavaNetAccess, for SSL/TLS endpoint identification.
 252          *
 253          * Note: May define a new public method in the future if necessary.
 254          */
 255         String originalHostName;
 256 
 257         InetAddressHolder() {}
 258 
 259         InetAddressHolder(String hostName, int address, int family) {

 291         }
 292 
 293         /**
 294          * Specifies the address family type, for instance, '1' for IPv4
 295          * addresses, and '2' for IPv6 addresses.
 296          */
 297         int family;
 298 
 299         int getFamily() {
 300             return family;
 301         }
 302     }
 303 
 304     /* Used to store the serializable fields of InetAddress */
 305     final transient InetAddressHolder holder;
 306 
 307     InetAddressHolder holder() {
 308         return holder;
 309     }
 310 
 311     /* Used to store the system-wide resolver */
 312     @Stable
 313     private static volatile InetAddressResolver resolver;
 314 
 315     private static final InetAddressResolver BUILTIN_RESOLVER;
 316 
 317     /**
 318      * Used to store the best available hostname.
 319      * Lazily initialized via a data race; safe because Strings are immutable.
 320      */
 321     private transient String canonicalHostName = null;
 322 
 323     /** use serialVersionUID from JDK 1.0.2 for interoperability */
 324     @java.io.Serial
 325     private static final long serialVersionUID = 3286316764910316507L;
 326 
 327     // "java.net.preferIPv4Stack" system property value
 328     private static final String PREFER_IPV4_STACK_VALUE;
 329 
 330     // "java.net.preferIPv6Addresses" system property value
 331     private static final String PREFER_IPV6_ADDRESSES_VALUE;
 332 
 333     // "jdk.net.hosts.file" system property value
 334     private static final String HOSTS_FILE_NAME;
 335 
 336     /*
 337      * Load net library into runtime, and perform initializations.
 338      */
 339     static {
 340         PREFER_IPV4_STACK_VALUE =
 341                 GetPropertyAction.privilegedGetProperty("java.net.preferIPv4Stack");
 342         PREFER_IPV6_ADDRESSES_VALUE =
 343                 GetPropertyAction.privilegedGetProperty("java.net.preferIPv6Addresses");
 344         HOSTS_FILE_NAME =
 345                 GetPropertyAction.privilegedGetProperty("jdk.net.hosts.file");






 346         jdk.internal.loader.BootLoader.loadLibrary("net");
 347         SharedSecrets.setJavaNetInetAddressAccess(
 348                 new JavaNetInetAddressAccess() {
 349                     public String getOriginalHostName(InetAddress ia) {
 350                         return ia.holder.getOriginalHostName();
 351                     }
 352 







 353                     public int addressValue(Inet4Address inet4Address) {
 354                         return inet4Address.addressValue();
 355                     }
 356 
 357                     public byte[] addressBytes(Inet6Address inet6Address) {
 358                         return inet6Address.addressBytes();
 359                     }
 360                 }
 361         );
 362         init();
 363     }
 364 
 365     /**
 366      * Creates an address lookup policy from {@code "java.net.preferIPv4Stack"},
 367      * {@code "java.net.preferIPv6Addresses"} system property values, and O/S configuration.
 368      */
 369     private static final LookupPolicy initializePlatformLookupPolicy() {
 370         // Calculate AddressFamily value first
 371         boolean ipv4Available = isIPv4Available();
 372         if ("true".equals(PREFER_IPV4_STACK_VALUE) && ipv4Available) {
 373             return LookupPolicy.of(IPV4);
 374         }
 375         // Check if IPv6 is not supported
 376         if (InetAddress.impl instanceof Inet4AddressImpl) {
 377             return LookupPolicy.of(IPV4);
 378         }
 379         // Check if system supports IPv4, if not use IPv6
 380         if (!ipv4Available) {
 381             return LookupPolicy.of(IPV6);
 382         }
 383         // If both address families are needed - check preferIPv6Addresses value
 384         if (PREFER_IPV6_ADDRESSES_VALUE != null) {
 385             if (PREFER_IPV6_ADDRESSES_VALUE.equalsIgnoreCase("true")) {
 386                 return LookupPolicy.of(IPV4 | IPV6 | IPV6_FIRST);
 387             }
 388             if (PREFER_IPV6_ADDRESSES_VALUE.equalsIgnoreCase("false")) {
 389                 return LookupPolicy.of(IPV4 | IPV6 | IPV4_FIRST);
 390             }
 391             if (PREFER_IPV6_ADDRESSES_VALUE.equalsIgnoreCase("system")) {
 392                 return LookupPolicy.of(IPV4 | IPV6);
 393             }
 394         }
 395         // Default value with both address families needed - IPv4 addresses come first
 396         return LookupPolicy.of(IPV4 | IPV6 | IPV4_FIRST);
 397     }
 398 
 399     static boolean systemAddressesOrder(int lookupCharacteristics) {
 400         return (lookupCharacteristics & (IPV4_FIRST | IPV6_FIRST)) == 0;
 401     }
 402 
 403     static boolean ipv4AddressesFirst(int lookupCharacteristics) {
 404         return (lookupCharacteristics & IPV4_FIRST) != 0;
 405     }
 406 
 407     static boolean ipv6AddressesFirst(int lookupCharacteristics) {
 408         return (lookupCharacteristics & IPV6_FIRST) != 0;
 409     }
 410 
 411     // Native method to check if IPv4 is available
 412     private static native boolean isIPv4Available();
 413 
 414     /**
 415      * The {@code RuntimePermission("inetAddressResolverProvider")} is
 416      * necessary to subclass and instantiate the {@code InetAddressResolverProvider}
 417      * class, as well as to obtain resolver from an instance of that class,
 418      * and it is also required to obtain the operating system name resolution configurations.
 419      */
 420     private static final RuntimePermission INET_ADDRESS_RESOLVER_PERMISSION =
 421             new RuntimePermission("inetAddressResolverProvider");
 422 
 423     private static final ReentrantLock RESOLVER_LOCK = new ReentrantLock();
 424     private static volatile InetAddressResolver bootstrapResolver;
 425 
 426     @SuppressWarnings("removal")
 427     private static InetAddressResolver resolver() {
 428         InetAddressResolver cns = resolver;
 429         if (cns != null) {
 430             return cns;
 431         }
 432         if (VM.isBooted()) {
 433             RESOLVER_LOCK.lock();
 434             boolean bootstrapSet = false;
 435             try {
 436                 cns = resolver;
 437                 if (cns != null) {
 438                     return cns;
 439                 }
 440                 // Protection against provider calling InetAddress APIs during initialization
 441                 if (bootstrapResolver != null) {
 442                     return bootstrapResolver;
 443                 }
 444                 bootstrapResolver = BUILTIN_RESOLVER;
 445                 bootstrapSet = true;
 446 
 447                 if (HOSTS_FILE_NAME != null) {
 448                     // The default resolver service is already host file resolver
 449                     cns = BUILTIN_RESOLVER;
 450                 } else if (System.getSecurityManager() != null) {
 451                     PrivilegedAction<InetAddressResolver> pa = InetAddress::loadResolver;
 452                     cns = AccessController.doPrivileged(
 453                             pa, null, INET_ADDRESS_RESOLVER_PERMISSION);
 454                 } else {
 455                     cns = loadResolver();
 456                 }
 457 
 458                 InetAddress.resolver = cns;
 459                 return cns;
 460             } finally {
 461                 // We want to clear bootstrap resolver reference only after an attempt to
 462                 // instantiate a resolver has been completed.
 463                 if (bootstrapSet) {
 464                     bootstrapResolver = null;
 465                 }
 466                 RESOLVER_LOCK.unlock();
 467             }
 468         } else {
 469             return BUILTIN_RESOLVER;
 470         }
 471     }
 472 
 473     private static InetAddressResolver loadResolver() {
 474         return ServiceLoader.load(InetAddressResolverProvider.class)
 475                 .findFirst()
 476                 .map(nsp -> nsp.get(builtinConfiguration()))
 477                 .orElse(BUILTIN_RESOLVER);
 478     }
 479 
 480     private static InetAddressResolverProvider.Configuration builtinConfiguration() {
 481         return new ResolverProviderConfiguration(BUILTIN_RESOLVER, () -> {
 482             try {
 483                 return impl.getLocalHostName();
 484             } catch (UnknownHostException unknownHostException) {
 485                 return "localhost";
 486             }
 487         });
 488     }
 489 
 490     /**
 491      * Constructor for the Socket.accept() method.
 492      * This creates an empty InetAddress, which is filled in by
 493      * the accept() method.  This InetAddress, however, is not
 494      * put in the address cache, since it is not created by name.
 495      */
 496     InetAddress() {
 497         holder = new InetAddressHolder();
 498     }
 499 
 500     /**
 501      * Replaces the de-serialized object with an Inet4Address object.
 502      *
 503      * @return the alternate object to the de-serialized object.
 504      *
 505      * @throws ObjectStreamException if a new object replacing this
 506      * object could not be created
 507      */
 508     @java.io.Serial
 509     private Object readResolve() throws ObjectStreamException {

 682      * @throws IOException if a network error occurs
 683      * @since 1.5
 684      */
 685     public boolean isReachable(NetworkInterface netif, int ttl,
 686                                int timeout) throws IOException {
 687         if (ttl < 0)
 688             throw new IllegalArgumentException("ttl can't be negative");
 689         if (timeout < 0)
 690             throw new IllegalArgumentException("timeout can't be negative");
 691 
 692         return impl.isReachable(this, timeout, netif, ttl);
 693     }
 694 
 695     /**
 696      * Gets the host name for this IP address.
 697      *
 698      * <p>If this InetAddress was created with a host name,
 699      * this host name will be remembered and returned;
 700      * otherwise, a reverse name lookup will be performed
 701      * and the result will be returned based on the system
 702      * configured resolver. If a lookup of the name service
 703      * is required, call
 704      * {@link #getCanonicalHostName() getCanonicalHostName}.
 705      *
 706      * <p>If there is a security manager, its
 707      * {@code checkConnect} method is first called
 708      * with the hostname and {@code -1}
 709      * as its arguments to see if the operation is allowed.
 710      * If the operation is not allowed, it will return
 711      * the textual representation of the IP address.
 712      *
 713      * @return  the host name for this IP address, or if the operation
 714      *    is not allowed by the security check, the textual
 715      *    representation of the IP address.
 716      *
 717      * @see InetAddress#getCanonicalHostName
 718      * @see SecurityManager#checkConnect
 719      */
 720     public String getHostName() {
 721         return getHostName(true);
 722     }

 783     /**
 784      * Returns the hostname for this address.
 785      *
 786      * <p>If there is a security manager, this method first
 787      * calls its {@code checkConnect} method
 788      * with the hostname and {@code -1}
 789      * as its arguments to see if the calling code is allowed to know
 790      * the hostname for this IP address, i.e., to connect to the host.
 791      * If the operation is not allowed, it will return
 792      * the textual representation of the IP address.
 793      *
 794      * @return  the host name for this IP address, or if the operation
 795      *    is not allowed by the security check, the textual
 796      *    representation of the IP address.
 797      *
 798      * @param check make security check if true
 799      *
 800      * @see SecurityManager#checkConnect
 801      */
 802     private static String getHostFromNameService(InetAddress addr, boolean check) {
 803         String host;
 804         var resolver = resolver();
 805         try {
 806             // first lookup the hostname
 807             host = resolver.lookupByAddress(addr.getAddress());
 808 
 809             /* check to see if calling code is allowed to know
 810              * the hostname for this IP address, ie, connect to the host
 811              */
 812             if (check) {
 813                 @SuppressWarnings("removal")
 814                 SecurityManager sec = System.getSecurityManager();
 815                 if (sec != null) {
 816                     sec.checkConnect(host, -1);
 817                 }
 818             }
 819 
 820             /* now get all the IP addresses for this hostname,
 821              * and make sure one of them matches the original IP
 822              * address. We do this to try and prevent spoofing.
 823              */
 824 
 825             InetAddress[] arr = InetAddress.getAllByName0(host, check);
 826             boolean ok = false;
 827 
 828             if (arr != null) {
 829                 for (int i = 0; !ok && i < arr.length; i++) {
 830                     ok = addr.equals(arr[i]);
 831                 }
 832             }
 833 
 834             //XXX: if it looks like a spoof just return the address?
 835             if (!ok) {
 836                 host = addr.getHostAddress();
 837                 return host;
 838             }
 839         // 'resolver.lookupByAddress' and 'InetAddress.getAllByName0' delegate to the system-wide resolver,
 840         // which could be a custom one. At that point we treat any unexpected RuntimeException thrown by
 841         // the resolver as we would treat an UnknownHostException or an unmatched host name.
 842         } catch (RuntimeException | UnknownHostException e) {
 843             host = addr.getHostAddress();



 844         }
 845         return host;
 846     }
 847 
 848     /**
 849      * Returns the raw IP address of this {@code InetAddress}
 850      * object. The result is in network byte order: the highest order
 851      * byte of the address is in {@code getAddress()[0]}.
 852      *
 853      * @return  the raw IP address of this object.
 854      */
 855     public byte[] getAddress() {
 856         return null;
 857     }
 858 
 859     /**
 860      * Returns the IP address string in textual presentation.
 861      *
 862      * @return  the raw IP address in a string format.
 863      * @since   1.0.2

 883      * <p>
 884      * Two instances of {@code InetAddress} represent the same IP
 885      * address if the length of the byte arrays returned by
 886      * {@code getAddress} is the same for both, and each of the
 887      * array components is the same for the byte arrays.
 888      *
 889      * @param   obj   the object to compare against.
 890      * @return  {@code true} if the objects are the same;
 891      *          {@code false} otherwise.
 892      * @see     java.net.InetAddress#getAddress()
 893      */
 894     public boolean equals(Object obj) {
 895         return false;
 896     }
 897 
 898     /**
 899      * Converts this IP address to a {@code String}. The
 900      * string returned is of the form: hostname / literal IP
 901      * address.
 902      *
 903      * If the host name is unresolved, no reverse lookup
 904      * is performed. The hostname part will be represented
 905      * by an empty string.
 906      *
 907      * @return  a string representation of this IP address.
 908      */
 909     public String toString() {
 910         String hostName = holder().getHostName();
 911         return Objects.toString(hostName, "")
 912             + "/" + getHostAddress();
 913     }
 914 
 915     // mapping from host name to Addresses - either NameServiceAddresses (while
 916     // still being looked-up by NameService(s)) or CachedAddresses when cached
 917     private static final ConcurrentMap<String, Addresses> cache =
 918         new ConcurrentHashMap<>();
 919 
 920     // CachedAddresses that have to expire are kept ordered in this NavigableSet
 921     // which is scanned on each access
 922     private static final NavigableSet<CachedAddresses> expirySet =
 923         new ConcurrentSkipListSet<>();
 924 
 925     // common interface

 950         }
 951 
 952         @Override
 953         public int compareTo(CachedAddresses other) {
 954             // natural order is expiry time -
 955             // compare difference of expiry times rather than
 956             // expiry times directly, to avoid possible overflow.
 957             // (see System.nanoTime() recommendations...)
 958             long diff = this.expiryTime - other.expiryTime;
 959             if (diff < 0L) return -1;
 960             if (diff > 0L) return 1;
 961             // ties are broken using unique id
 962             return Long.compare(this.id, other.id);
 963         }
 964     }
 965 
 966     // a name service lookup based Addresses implementation which replaces itself
 967     // in cache when the result is obtained
 968     private static final class NameServiceAddresses implements Addresses {
 969         private final String host;

 970 
 971         NameServiceAddresses(String host) {
 972             this.host = host;

 973         }
 974 
 975         @Override
 976         public InetAddress[] get() throws UnknownHostException {
 977             Addresses addresses;
 978             // only one thread is doing lookup to name service
 979             // for particular host at any time.
 980             synchronized (this) {
 981                 // re-check that we are still us + re-install us if slot empty
 982                 addresses = cache.putIfAbsent(host, this);
 983                 if (addresses == null) {
 984                     // this can happen when we were replaced by CachedAddresses in
 985                     // some other thread, then CachedAddresses expired and were
 986                     // removed from cache while we were waiting for lock...
 987                     addresses = this;
 988                 }
 989                 // still us ?
 990                 if (addresses == this) {
 991                     // lookup name services
 992                     InetAddress[] inetAddresses;
 993                     UnknownHostException ex;
 994                     int cachePolicy;
 995                     try {
 996                         inetAddresses = getAddressesFromNameService(host);
 997                         ex = null;
 998                         cachePolicy = InetAddressCachePolicy.get();
 999                     } catch (UnknownHostException uhe) {
1000                         inetAddresses = null;
1001                         ex = uhe;
1002                         cachePolicy = InetAddressCachePolicy.getNegative();
1003                     }
1004                     // remove or replace us with cached addresses according to cachePolicy
1005                     if (cachePolicy == InetAddressCachePolicy.NEVER) {
1006                         cache.remove(host, this);
1007                     } else {
1008                         CachedAddresses cachedAddresses = new CachedAddresses(
1009                             host,
1010                             inetAddresses,
1011                             cachePolicy == InetAddressCachePolicy.FOREVER
1012                             ? 0L
1013                             // cachePolicy is in [s] - we need [ns]
1014                             : System.nanoTime() + 1000_000_000L * cachePolicy
1015                         );
1016                         if (cache.replace(host, this, cachedAddresses) &&
1017                             cachePolicy != InetAddressCachePolicy.FOREVER) {
1018                             // schedule expiry
1019                             expirySet.add(cachedAddresses);
1020                         }
1021                     }
1022                     if (inetAddresses == null || inetAddresses.length == 0) {
1023                         throw ex == null ? new UnknownHostException(host) : ex;
1024                     }
1025                     return inetAddresses;
1026                 }
1027                 // else addresses != this
1028             }
1029             // delegate to different addresses when we are already replaced
1030             // but outside of synchronized block to avoid any chance of dead-locking
1031             return addresses.get();
1032         }
1033     }
1034 
1035     /**
1036      * The default InetAddressResolver implementation, which delegates to the underlying































1037      * OS network libraries to resolve host address mappings.
1038      *
1039      * @since 9
1040      */
1041     private static final class PlatformResolver implements InetAddressResolver {
1042 
1043         public Stream<InetAddress> lookupByName(String host, LookupPolicy policy)
1044                 throws UnknownHostException {
1045             Objects.requireNonNull(host);
1046             Objects.requireNonNull(policy);
1047             return Arrays.stream(impl.lookupAllHostAddr(host, policy));
1048         }
1049 
1050         public String lookupByAddress(byte[] addr)
1051                 throws UnknownHostException {
1052             Objects.requireNonNull(addr);
1053             if (addr.length != Inet4Address.INADDRSZ && addr.length != Inet6Address.INADDRSZ) {
1054                 throw new IllegalArgumentException("Invalid address length");
1055             }
1056             return impl.getHostByAddr(addr);
1057         }
1058     }
1059 
1060     /**
1061      * The HostsFileResolver provides host address mapping
1062      * by reading the entries in a hosts file, which is specified by
1063      * {@code jdk.net.hosts.file} system property
1064      *
1065      * <p>The file format is that which corresponds with the /etc/hosts file
1066      * IP Address host alias list.
1067      *
1068      * <p>When the file lookup is enabled it replaces the default InetAddressResolver
1069      * implementation
1070      *
1071      * @since 9
1072      */
1073     private static final class HostsFileResolver implements InetAddressResolver {






1074 
1075         private final String hostsFile;
1076 
1077         public HostsFileResolver(String hostsFileName) {
1078             this.hostsFile = hostsFileName;
1079         }
1080 
1081         /**
1082          * Lookup the host name  corresponding to the IP address provided.
1083          * Search the configured host file a host name corresponding to
1084          * the specified IP address.
1085          *
1086          * @param addr byte array representing an IP address
1087          * @return {@code String} representing the host name mapping
1088          * @throws UnknownHostException if no host found for the specified IP address
1089          * @throws IllegalArgumentException if IP address is of illegal length
1090          */
1091         @Override
1092         public String lookupByAddress(byte[] addr) throws UnknownHostException {
1093             String hostEntry;
1094             String host = null;
1095             Objects.requireNonNull(addr);
1096             // Check the length of the address array
1097             if (addr.length != Inet4Address.INADDRSZ && addr.length != Inet6Address.INADDRSZ) {
1098                 throw new IllegalArgumentException("Invalid address length");
1099             }
1100 
1101             try (Scanner hostsFileScanner = new Scanner(new File(hostsFile),
1102                                                         UTF_8.INSTANCE)) {

1103                 while (hostsFileScanner.hasNextLine()) {
1104                     hostEntry = hostsFileScanner.nextLine();
1105                     if (!hostEntry.startsWith("#")) {
1106                         hostEntry = removeComments(hostEntry);
1107                         String[] mapping = hostEntry.split("\\s+");
1108                         if (mapping.length >= 2 &&
1109                             Arrays.equals(addr, createAddressByteArray(mapping[0]))) {
1110                             host = mapping[1];
1111                             break;
1112                         }
1113                     }
1114                 }
1115             } catch (IOException e) {
1116                 throw new UnknownHostException("Unable to resolve address "
1117                         + Arrays.toString(addr) + " as hosts file " + hostsFile
1118                         + " not found ");
1119             }
1120 
1121             if ((host == null) || (host.isEmpty()) || (host.equals(" "))) {
1122                 throw new UnknownHostException("Requested address "
1123                         + Arrays.toString(addr)
1124                         + " resolves to an invalid entry in hosts file "
1125                         + hostsFile);
1126             }
1127             return host;
1128         }
1129 
1130         /**
1131          * <p>Lookup a host mapping by name. Retrieve the IP addresses
1132          * associated with a host.
1133          *
1134          * <p>Search the configured hosts file for the addresses associated
1135          * with the specified host name.
1136          *
1137          * @param host the specified hostname
1138          * @param lookupPolicy IP addresses lookup policy which specifies addresses
1139          *                     family and their order
1140          * @return stream of IP addresses for the requested host
1141          * @throws UnknownHostException
1142          *             if no IP address for the {@code host} could be found
1143          */
1144         public Stream<InetAddress> lookupByName(String host, LookupPolicy lookupPolicy)
1145                 throws UnknownHostException {
1146             String hostEntry;
1147             String addrStr;
1148             byte addr[];
1149 
1150             Objects.requireNonNull(host);
1151             Objects.requireNonNull(lookupPolicy);
1152             List<InetAddress> inetAddresses = new ArrayList<>();
1153             List<InetAddress> inet4Addresses = new ArrayList<>();
1154             List<InetAddress> inet6Addresses = new ArrayList<>();
1155             int flags = lookupPolicy.characteristics();
1156             boolean needIPv4 = (flags & IPv4) != 0;
1157             boolean needIPv6 = (flags & IPv6) != 0;
1158 
1159             // lookup the file and create a list InetAddress for the specified host
1160             try (Scanner hostsFileScanner = new Scanner(new File(hostsFile),
1161                     UTF_8.INSTANCE)) {
1162                 while (hostsFileScanner.hasNextLine()) {
1163                     hostEntry = hostsFileScanner.nextLine();
1164                     if (!hostEntry.startsWith("#")) {
1165                         hostEntry = removeComments(hostEntry);
1166                         if (hostEntry.contains(host)) {
1167                             addrStr = extractHostAddr(hostEntry, host);
1168                             if ((addrStr != null) && (!addrStr.isEmpty())) {
1169                                 addr = createAddressByteArray(addrStr);
1170                                 if (addr != null) {
1171                                     InetAddress address = InetAddress.getByAddress(host, addr);
1172                                     inetAddresses.add(address);
1173                                     if (address instanceof Inet4Address && needIPv4) {
1174                                         inet4Addresses.add(address);
1175                                     }
1176                                     if (address instanceof Inet6Address && needIPv6) {
1177                                         inet6Addresses.add(address);
1178                                     }
1179                                 }
1180                             }
1181                         }
1182                     }
1183                 }
1184             } catch (IOException e) {
1185                 throw new UnknownHostException("Unable to resolve host " + host
1186                         + " as hosts file " + hostsFile + " not found ");
1187             }
1188             // Check if only IPv4 addresses are requested
1189             if (needIPv4 && !needIPv6) {
1190                 checkResultsList(inet4Addresses, host);
1191                 return inet4Addresses.stream();









1192             }
1193             // Check if only IPv6 addresses are requested
1194             if (!needIPv4 && needIPv6) {
1195                 checkResultsList(inet6Addresses, host);
1196                 return inet6Addresses.stream();
1197             }
1198             // If both type of addresses are requested:
1199             // First, check if there is any results. Then arrange
1200             // addresses according to LookupPolicy value.
1201             checkResultsList(inetAddresses, host);
1202             if (ipv6AddressesFirst(flags)) {
1203                 return Stream.concat(inet6Addresses.stream(), inet4Addresses.stream());
1204             } else if (ipv4AddressesFirst(flags)) {
1205                 return Stream.concat(inet4Addresses.stream(), inet6Addresses.stream());
1206             }
1207             // Only "system" addresses order is possible at this stage
1208             assert systemAddressesOrder(flags);
1209             return inetAddresses.stream();
1210         }
1211 
1212         // Checks if result list with addresses is not empty.
1213         // If it is empty throw an UnknownHostException.
1214         private void checkResultsList(List<InetAddress> addressesList, String hostName)
1215                 throws UnknownHostException {
1216             if (addressesList.isEmpty()) {
1217                 throw new UnknownHostException("Unable to resolve host " + hostName
1218                         + " in hosts file " + hostsFile);
1219             }
1220         }
1221 
1222         private String removeComments(String hostsEntry) {
1223             String filteredEntry = hostsEntry;
1224             int hashIndex;
1225 
1226             if ((hashIndex = hostsEntry.indexOf("#")) != -1) {
1227                 filteredEntry = hostsEntry.substring(0, hashIndex);
1228             }
1229             return filteredEntry;
1230         }
1231 
1232         private byte [] createAddressByteArray(String addrStr) {
1233             byte[] addrArray;
1234             // check if IPV4 address - most likely
1235             addrArray = IPAddressUtil.textToNumericFormatV4(addrStr);
1236             if (addrArray == null) {
1237                 addrArray = IPAddressUtil.textToNumericFormatV6(addrStr);
1238             }
1239             return addrArray;

1241 
1242         /** host to ip address mapping */
1243         private String extractHostAddr(String hostEntry, String host) {
1244             String[] mapping = hostEntry.split("\\s+");
1245             String hostAddr = null;
1246 
1247             if (mapping.length >= 2) {
1248                 // look at the host aliases
1249                 for (int i = 1; i < mapping.length; i++) {
1250                     if (mapping[i].equalsIgnoreCase(host)) {
1251                         hostAddr = mapping[0];
1252                     }
1253                 }
1254             }
1255             return hostAddr;
1256         }
1257     }
1258 
1259     static final InetAddressImpl  impl;
1260 
1261     /**
1262      * Platform-wide {@code LookupPolicy} initialized from {@code "java.net.preferIPv4Stack"},
1263      * {@code "java.net.preferIPv6Addresses"} system properties.
1264      */
1265     static final LookupPolicy PLATFORM_LOOKUP_POLICY;
1266 
1267     static {
1268         // create the impl
1269         impl = InetAddressImplFactory.create();
1270 
1271         // impl must be initialized before calling this method
1272         PLATFORM_LOOKUP_POLICY = initializePlatformLookupPolicy();
1273 
1274         // create built-in resolver
1275         BUILTIN_RESOLVER = createBuiltinInetAddressResolver();
1276     }
1277 
1278     /**
1279      * Create an instance of the InetAddressResolver interface based on
1280      * the setting of the {@code jdk.net.hosts.file} system property.
1281      *
1282      * <p>The default InetAddressResolver is the PlatformResolver, which typically
1283      * delegates name and address resolution calls to the underlying
1284      * OS network libraries.
1285      *
1286      * <p> A HostsFileResolver is created if the {@code jdk.net.hosts.file}
1287      * system property is set. If the specified file doesn't exist, the name or
1288      * address lookup will result in an UnknownHostException. Thus, non existent
1289      * hosts file is handled as if the file is empty.
1290      *
1291      * @return an InetAddressResolver
1292      */
1293     private static InetAddressResolver createBuiltinInetAddressResolver() {
1294         InetAddressResolver theResolver;
1295         if (HOSTS_FILE_NAME != null) {
1296             theResolver = new HostsFileResolver(HOSTS_FILE_NAME);



1297         } else {
1298             theResolver = new PlatformResolver();
1299         }
1300         return theResolver;
1301     }
1302 
1303     /**
1304      * Creates an InetAddress based on the provided host name and IP address.
1305      * System {@linkplain InetAddressResolver resolver} is not used to check
1306      * the validity of the address.
1307      *
1308      * <p> The host name can either be a machine name, such as
1309      * "{@code www.example.com}", or a textual representation of its IP
1310      * address.
1311      * <p> No validity checking is done on the host name either.
1312      *
1313      * <p> If addr specifies an IPv4 address an instance of Inet4Address
1314      * will be returned; otherwise, an instance of Inet6Address
1315      * will be returned.
1316      *
1317      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
1318      * must be 16 bytes long
1319      *
1320      * @param host the specified host
1321      * @param addr the raw IP address in network byte order
1322      * @return  an InetAddress object created from the raw IP address.
1323      * @throws     UnknownHostException  if IP address is of illegal length
1324      * @since 1.4
1325      */
1326     public static InetAddress getByAddress(String host, byte[] addr)

1369      * section&nbsp;2.5.3.
1370      *
1371      * <p> If there is a security manager, and {@code host} is not {@code null}
1372      * or {@code host.length() } is not equal to zero, the security manager's
1373      * {@code checkConnect} method is called with the hostname and {@code -1}
1374      * as its arguments to determine if the operation is allowed.
1375      *
1376      * @param      host   the specified host, or {@code null}.
1377      * @return     an IP address for the given host name.
1378      * @throws     UnknownHostException  if no IP address for the
1379      *               {@code host} could be found, or if a scope_id was specified
1380      *               for a global IPv6 address.
1381      * @throws     SecurityException if a security manager exists
1382      *             and its checkConnect method doesn't allow the operation
1383      */
1384     public static InetAddress getByName(String host)
1385         throws UnknownHostException {
1386         return InetAddress.getAllByName(host)[0];
1387     }
1388 






1389     /**
1390      * Given the name of a host, returns an array of its IP addresses,
1391      * based on the configured system {@linkplain InetAddressResolver resolver}.
1392      *
1393      * <p> The host name can either be a machine name, such as
1394      * "{@code www.example.com}", or a textual representation of its IP
1395      * address. If a literal IP address is supplied, only the
1396      * validity of the address format is checked.
1397      *
1398      * <p> For {@code host} specified in <i>literal IPv6 address</i>,
1399      * either the form defined in RFC 2732 or the literal IPv6 address
1400      * format defined in RFC 2373 is accepted. A literal IPv6 address may
1401      * also be qualified by appending a scoped zone identifier or scope_id.
1402      * The syntax and usage of scope_ids is described
1403      * <a href="Inet6Address.html#scoped">here</a>.
1404      *
1405      * <p> If the host is {@code null} or {@code host.length()} is equal
1406      * to zero, then an {@code InetAddress} representing an address of the
1407      * loopback interface is returned.
1408      * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
1409      * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
1410      * section&nbsp;2.5.3. </p>
1411      *
1412      * <p> If there is a security manager, and {@code host} is not {@code null}
1413      * or {@code host.length() } is not equal to zero, the security manager's
1414      * {@code checkConnect} method is called with the hostname and {@code -1}
1415      * as its arguments to determine if the operation is allowed.
1416      *
1417      * @param      host   the name of the host, or {@code null}.
1418      * @return     an array of all the IP addresses for a given host name.
1419      *
1420      * @throws     UnknownHostException  if no IP address for the
1421      *               {@code host} could be found, or if a scope_id was specified
1422      *               for a global IPv6 address.
1423      * @throws     SecurityException  if a security manager exists and its
1424      *               {@code checkConnect} method doesn't allow the operation.
1425      *
1426      * @see SecurityManager#checkConnect
1427      */
1428     public static InetAddress[] getAllByName(String host)
1429         throws UnknownHostException {





1430 
1431         if (host == null || host.isEmpty()) {
1432             InetAddress[] ret = new InetAddress[1];
1433             ret[0] = impl.loopbackAddress();
1434             return ret;
1435         }
1436 
1437         boolean ipv6Expected = false;
1438         if (host.charAt(0) == '[') {
1439             // This is supposed to be an IPv6 literal
1440             if (host.length() > 2 && host.charAt(host.length()-1) == ']') {
1441                 host = host.substring(1, host.length() -1);
1442                 ipv6Expected = true;
1443             } else {
1444                 // This was supposed to be a IPv6 address, but it's not!
1445                 throw new UnknownHostException(host + ": invalid IPv6 address");
1446             }
1447         }
1448 
1449         // if host is an IP address, we won't do further lookup

1471                 // Means an IPv4 literal between brackets!
1472                 throw new UnknownHostException("["+host+"]");
1473             }
1474             InetAddress[] ret = new InetAddress[1];
1475             if(addr != null) {
1476                 if (addr.length == Inet4Address.INADDRSZ) {
1477                     ret[0] = new Inet4Address(null, addr);
1478                 } else {
1479                     if (ifname != null) {
1480                         ret[0] = new Inet6Address(null, addr, ifname);
1481                     } else {
1482                         ret[0] = new Inet6Address(null, addr, numericZone);
1483                     }
1484                 }
1485                 return ret;
1486             }
1487         } else if (ipv6Expected) {
1488             // We were expecting an IPv6 Literal, but got something else
1489             throw new UnknownHostException("["+host+"]");
1490         }
1491         return getAllByName0(host, true, true);
1492     }
1493 
1494     /**
1495      * Returns the loopback address.
1496      * <p>
1497      * The InetAddress returned will represent the IPv4
1498      * loopback address, 127.0.0.1, or the IPv6 loopback
1499      * address, ::1. The IPv4 loopback address returned
1500      * is only one of many in the form 127.*.*.*
1501      *
1502      * @return  the InetAddress loopback instance.
1503      * @since 1.7
1504      */
1505     public static InetAddress getLoopbackAddress() {
1506         return impl.loopbackAddress();
1507     }
1508 
1509 
1510     /**
1511      * check if the literal address string has %nn appended

1521         if (percent == -1) {
1522             return -1;
1523         }
1524         for (int i=percent+1; i<slen; i++) {
1525             char c = s.charAt(i);
1526             if (c == ']') {
1527                 if (i == percent+1) {
1528                     /* empty per-cent field */
1529                     return -1;
1530                 }
1531                 break;
1532             }
1533             if ((digit = Character.digit (c, 10)) < 0) {
1534                 return -1;
1535             }
1536             zone = (zone * 10) + digit;
1537         }
1538         return zone;
1539     }
1540 






1541     /**
1542      * package private so SocketPermission can call it
1543      */
1544     static InetAddress[] getAllByName0 (String host, boolean check)
1545         throws UnknownHostException  {
1546         return getAllByName0(host, check, true);
1547     }
1548 
1549     /**
1550      * Designated lookup method.
1551      *
1552      * @param host host name to look up

1553      * @param check perform security check
1554      * @param useCache use cached value if not expired else always
1555      *                 perform name service lookup (and cache the result)
1556      * @return array of InetAddress(es)
1557      * @throws UnknownHostException if host name is not found
1558      */
1559     private static InetAddress[] getAllByName0(String host,

1560                                                boolean check,
1561                                                boolean useCache)
1562         throws UnknownHostException  {
1563 
1564         /* If it gets here it is presumed to be a hostname */
1565 
1566         /* make sure the connection to the host is allowed, before we
1567          * give out a hostname
1568          */
1569         if (check) {
1570             @SuppressWarnings("removal")
1571             SecurityManager security = System.getSecurityManager();
1572             if (security != null) {
1573                 security.checkConnect(host, -1);
1574             }
1575         }
1576 
1577         // remove expired addresses from cache - expirySet keeps them ordered
1578         // by expiry time so we only need to iterate the prefix of the NavigableSet...
1579         long now = System.nanoTime();

1597         // look-up or remove from cache
1598         Addresses addrs;
1599         if (useCache) {
1600             addrs = cache.get(host);
1601         } else {
1602             addrs = cache.remove(host);
1603             if (addrs != null) {
1604                 if (addrs instanceof CachedAddresses) {
1605                     // try removing from expirySet too if CachedAddresses
1606                     expirySet.remove(addrs);
1607                 }
1608                 addrs = null;
1609             }
1610         }
1611 
1612         if (addrs == null) {
1613             // create a NameServiceAddresses instance which will look up
1614             // the name service and install it within cache...
1615             Addresses oldAddrs = cache.putIfAbsent(
1616                 host,
1617                     addrs = new NameServiceAddresses(host)
1618             );
1619             if (oldAddrs != null) { // lost putIfAbsent race
1620                 addrs = oldAddrs;
1621             }
1622         }
1623 
1624         // ask Addresses to get an array of InetAddress(es) and clone it
1625         return addrs.get().clone();
1626     }
1627 
1628     static InetAddress[] getAddressesFromNameService(String host)
1629             throws UnknownHostException {
1630         Stream<InetAddress> addresses = null;
1631         UnknownHostException ex = null;
1632 
1633         var resolver = resolver();
1634         try {
1635             addresses = resolver.lookupByName(host, PLATFORM_LOOKUP_POLICY);
1636         } catch (RuntimeException | UnknownHostException x) {
1637             if (host.equalsIgnoreCase("localhost")) {
1638                 addresses = Stream.of(impl.loopbackAddress());
1639             } else if (x instanceof UnknownHostException uhe) {
1640                 ex = uhe;
1641             } else {
1642                 ex = new UnknownHostException();
1643                 ex.initCause(x);
1644             }
1645         }
1646         InetAddress[] result = addresses == null ? null
1647                 : addresses.toArray(InetAddress[]::new);
1648         if (result == null || result.length == 0) {
1649             throw ex == null ? new UnknownHostException(host) : ex;
1650         }
1651         return result;






















1652     }
1653 
1654     /**
1655      * Returns an {@code InetAddress} object given the raw IP address .
1656      * The argument is in network byte order: the highest order
1657      * byte of the address is in {@code getAddress()[0]}.
1658      *
1659      * <p> This method doesn't block, i.e. no reverse lookup is performed.

1660      *
1661      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
1662      * must be 16 bytes long
1663      *
1664      * @param addr the raw IP address in network byte order
1665      * @return  an InetAddress object created from the raw IP address.
1666      * @throws     UnknownHostException  if IP address is of illegal length
1667      * @since 1.4
1668      */
1669     public static InetAddress getByAddress(byte[] addr)
1670         throws UnknownHostException {
1671         return getByAddress(null, addr);
1672     }
1673 
1674     private static final class CachedLocalHost {
1675         final String host;
1676         final InetAddress addr;
1677         final long expiryTime = System.nanoTime() + 5000_000_000L; // now + 5s;
1678 
1679         CachedLocalHost(String host, InetAddress addr) {

1718                 if (security != null) {
1719                     security.checkConnect(clh.host, -1);
1720                 }
1721                 return clh.addr;
1722             }
1723 
1724             String local = impl.getLocalHostName();
1725 
1726             if (security != null) {
1727                 security.checkConnect(local, -1);
1728             }
1729 
1730             InetAddress localAddr;
1731             if (local.equals("localhost")) {
1732                 // shortcut for "localhost" host name
1733                 localAddr = impl.loopbackAddress();
1734             } else {
1735                 // call getAllByName0 without security checks and
1736                 // without using cached data
1737                 try {
1738                     localAddr = getAllByName0(local, false, false)[0];
1739                 } catch (UnknownHostException uhe) {
1740                     // Rethrow with a more informative error message.
1741                     UnknownHostException uhe2 =
1742                         new UnknownHostException(local + ": " +
1743                                                  uhe.getMessage());
1744                     uhe2.initCause(uhe);
1745                     throw uhe2;
1746                 }
1747             }
1748             cachedLocalHost = new CachedLocalHost(local, localAddr);
1749             return localAddr;
1750         } catch (java.lang.SecurityException e) {
1751             return impl.loopbackAddress();
1752         }
1753     }
1754 
1755     /**
1756      * Perform class load-time initializations.
1757      */
1758     private static native void init();
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