a customer has ask this question, he has a network setup in which
DNS name to address translation is ok but address to name translation
is not allowed.
in this setup he has used an applet to connect to a server and run into
a huge delay because of this code in SocketPermission.java, method
impliesIgnoreMask:

          // XXX: if all else fails, compare hostnames?
          // Do we really want this?
          if (this.cname == null) {
              this.getCanonName();
          }

          if (that.cname == null) {
->               that.getCanonName();
          }

          return (this.cname.equalsIgnoreCase(that.cname));

this line doing reverse DNS hangs for long time. since the comment says
"do we really want this", it makes me think can this be considered to
removed? we have already compared IP address above this.