Name: mf23781 Date: 12/18/97


Another IBM division found this bug.

They have a Java app which starts up automatically at boot time and connects to
a server. The app is always active and runs in the background, with the intention
that it can bring up a message box when important news breaks. However, given that the client
could be on a modem (possibly via cell link) they have to account for the possibility of
the network going down and up again.
They try to resolve the server name by using getByName and if this fails due to a name unrecognised
by the DNS an 'unknown host exception' is thrown. However, if they are not connected to the network
they get the same error. Since the app 'knows' the name is a valid name they take this to mean the
network is down and they try again after an elapsed period of time. However an 'unknown
address' value has already been cached and is always returned from
that point on. Since any type of address resolution eventually comes
through this same piece of code, it seems any other API call will
hit the same problem.

  Since we cannot distinguish between a 'network down'
error and a real 'address not recognised', we must NOT cache the
'unknown address' value or retry the lookup if it failed before.

Suggested fix is in the getAllByName0 method in InetAddress.java;


        /* If no entry in cache, then do the host lookup */

// if (obj == null) { /* CHANGE THIS LINE TO THE ONE BELOW!
*/
            if ((obj == null) || (obj == unknown_array) {
                try {
                    /*
                     * Do not put the call to lookup() inside the
                     * constructor. if you do you will still be



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This is a duplicate of 4065037