The InetAddress.isReachable(nif, ttl, to) API returns true when testing the reachability of a host through the loopback interface of the machine. A loopback interface cannot be used to communicate with other hosts and therefore the API should return false. This problem is seen on a solaris 8 machine as well as a windows XP (ipv6 enabled) machine. The problem does not occur on a windows 2000 machine.

Steps to reproduce the problem:
1. Compile the attached code.
2. Execute the code on a solaris machine while using an ipv4 or an ipv6 address as a command line parameter to the program.
3. The code returns reachable through the loopback interface.

---------------------------BEGIN CODE-------------------------
import java.net.*;
import java.util.*;
import java.io.*;

public class Ipv6ReachableBugXP{
        public static void main(String args[]){
                String inputAdd = null;
                Enumeration nifEnum = null;
                NetworkInterface nif = null;
                InetAddress inetAdd = null;

                if (args.length > 0){
                        inputAdd = args[0];
                } else {
                        inputAdd = "fe80::a00:20ff:fef7:c4e7";
                }

                try{
                        inetAdd = InetAddress.getByName(inputAdd);
                } catch (UnknownHostException uhe){
                        uhe.printStackTrace();
                        System.exit(1);
                }

                try{
                        nifEnum = NetworkInterface.getNetworkInterfaces();
                } catch (SocketException se){
                        se.printStackTrace();
                        System.exit(1);
                }

                while (nifEnum.hasMoreElements()){
                        nif = (NetworkInterface) nifEnum.nextElement();
                        try {
                                System.out.println("Trying reachability of " +
                                               inetAdd + " through nif " + nif);
                                if (inetAdd.isReachable(nif, 20, 20000)){
                                        System.out.println("Reachable through NIF : " + nif);
                                } else {
                                        System.out.println("FAILURE !!! Unreachable through" +
                                                " NIF : " + nif);
                                }
                        } catch (IOException ioe){
                                ioe.printStackTrace();
                        }
                }
        }
}

----------------------------END CODE-------------------------

The output from a solaris 8 machine is given below
---------------------------BEGIN OUTPUT-------------------------
$java -showversion Ipv6ReachableBugXP fe80::a00:20ff:fef7:c4e7
java version "1.5.0-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-beta-b18)
Java HotSpot(TM) Client VM (build 1.5.0-beta-b18, mixed mode)

Trying reachability of /fe80:0:0:0:a00:20ff:fef7:c4e7 through nif name:hme0 (hme0) index: 2 addresses:
/fe80:0:0:0:a00:20ff:fefe:3440;
/129.158.229.142;

Reachable through NIF : name:hme0 (hme0) index: 2 addresses:
/fe80:0:0:0:a00:20ff:fefe:3440;
/129.158.229.142;

Trying reachability of /fe80:0:0:0:a00:20ff:fef7:c4e7 through nif name:lo0 (lo0) index: 1 addresses:
/0:0:0:0:0:0:0:1;
/127.0.0.1;

Reachable through NIF : name:lo0 (lo0) index: 1 addresses:
/0:0:0:0:0:0:0:1;
/127.0.0.1;

$
-----------------------------END OUTPUT-------------------------