test/jdk/java/net/InetAddress/ptr/Lookup.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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/*
 * Lookup/reverse lookup class for regression test 4773521
 * @test
 * @bug 4773521
 * @summary Test that reverse lookups of IPv4 addresses work when IPv6
 *          is enabled
 * @library /test/lib
 * @build jdk.test.lib.Utils
 *        jdk.test.lib.Asserts
 *        jdk.test.lib.JDKToolFinder
 *        jdk.test.lib.JDKToolLauncher
 *        jdk.test.lib.Platform
 *        jdk.test.lib.process.*
 *        Lookup
 * @run main Lookup root
 *
 */
import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.List;

import jdk.test.lib.JDKToolFinder;
import jdk.test.lib.process.OutputAnalyzer;

public class Lookup {
    private static final String HOST = "icann.org";
    private static final String SKIP = "SKIP";
    private static final String CLASS_PATH = System.getProperty(
            "test.class.path");

    public static void main(String args[]) throws IOException {
        String addr = null;
        String ipv4Name = null;
        if (args.length == 0) {
            // First check that host resolves to IPv4 address
            try {
                InetAddress ia = InetAddress.getByName(HOST);
                addr = ia.getHostAddress();
            } catch (UnknownHostException e) {
                System.out.print(SKIP);
                return;
            }
        } else {
            String tmp = lookupWithIPv4Prefer();
            System.out.println("IPv4 lookup results: [" + tmp + "]");
            if (SKIP.equals(tmp)) {
                System.out.println(HOST + " can't be resolved - test skipped.");
                return;
            }

            String[] strs = tmp.split(":");
            addr = strs[0];
            ipv4Name = strs[1];
        }

        // reverse lookup
        InetAddress ia = InetAddress.getByName(addr);
        String name = ia.getHostName();
        if (args.length == 0) {
            System.out.print(addr + ":" + name);
            return;
        } else {
            System.out.println("(default) " + addr + "--> " + name);
            if (!ipv4Name.equals(name)) {
                throw new RuntimeException("Mismatch between default"
                        + " and java.net.preferIPv4Stack=true results");
            }
        }
    }

    static String lookupWithIPv4Prefer() throws IOException {
        String java = JDKToolFinder.getTestJDKTool("java");
        String testClz = Lookup.class.getName();
        List<String> cmd = List.of(java, "-Djava.net.preferIPv4Stack=true",
                "-cp", CLASS_PATH, testClz);
        System.out.println("Executing: " + cmd);
        return new OutputAnalyzer(new ProcessBuilder(cmd).start()).getOutput();
    }
}