problem with maddr Via parameter

I came across an apparent bug in the nist-sip stack dealing with the
maddr Via parameter. I encountered a exception when doing a
ServerTransaction.sendResponse() on a received response. The stack trace
(sorry -- didn't save) showed that the exception was caused by cast
problem in Via.getMaddr().  I verified that that request did indeed
contain a maddr Via parameter; although the maddr appeared to me to be a
valid IP address. 

After looking through gov/nist/javax/sip/header/Via.java I discovered
that that the Via class is somewhat schizophrenic about the type of
object stored within the parameters collection for the maddr. There is
method Via.getMaddr() that assumes the maddr in the parameters
collection is a Host object. It directly casts the object to Host with
no further checking. This was the direct cause of the exception. There
is also another method Via.getmaddr() that assumes that the maddr is
stored as a String within parameters.

With some debugging I verified that the maddr is actually stored by the
parser as a String, which should cause any later call of Via.getMaddr()
to throw a cast exception. (setMaddr() will actually create and store an
maddr as a host -- but the parser does not call this method).

I am able to readily reproduce this problem in the 'simplecallsetup'
example by simply adding:

viaHeader.setMAddr("224.1.1.1");

following the creation of the ViaHeader for the INVITE.  No changes are
needed to the 'shootme' application. The shootist has no problem sending
that INVITE. The shootme has no problem initially processing the INVITE;
but later gets the bad cast exception when doing a sendResponse() on
that INVITE.

Jim Barton