Name: yyC67448 Date: 06/15/98




The java.net.setTTL method does not allow ttl = 0.

In fact zero ttl's are not incorrect, the multicast datagrams with zero ttl will
not be transmitted on any subnet, but may be delivered locally if the sending host
belongs to the destination group and if multicast loopback has not been disabled
on the sending socket.

The TTL thresholds enforce the following convention:

         ---------------------------------+-------------
         Scope | Initial TTL
         ---------------------------------+-------------
         restricted to the same host | 0
         restricted to the same subnet | 1
         restricted to the same site | 32
         restricted to the same region | 64
         restricted to the same continent | 128
         unrestricted | 255
         ---------------------------------+-------------

So, it is incorrect to exclude zero TTL from legal arguments for setTTL.


Here is the test demonstrating the bug:

-------------------------------- Test.java -----------------------------
import java.net.*;


public class test
{
  
  public static void main(String args[])
  {
    MulticastSocket soc = null;
    InetAddress sin = null;

    try {
      soc = new MulticastSocket();
      sin = InetAddress.getByName("224.80.80.80");
    } catch(Exception e)
    {
      System.out.println("Failed. Unexpected Exception : " + e);
      System.exit(-1);
    }
    
    try {
      soc.setTTL(0);
    } catch(IllegalArgumentException e)
    {
      System.out.println("Failed: Unexpected IllegalArgumentException");
    } catch(Exception e)
    {
      System.out.println("Failed. Unexpected exception.. " + e);
      System.exit(0);
    }
    
    System.out.println("Passed. OKAY");
    
  }

}
 

---------------------- Output from the test -----------------
Failed. Unexpected IllegalArgumentException
-----------------------------------------------------------------
======================================================================