[ntp:hackers] Further confirmation multicast broken

David L. Mills mills at udel.edu
Sun Feb 27 08:21:54 PST 2005


Multicast doesn't work at all. Confirmation follows.

In principle, multicast with symmetric key should work. However, because 
of the bug reported previously, the volley to calibrate the propagation 
delay fails because the multicast address, rather than the unicast 
address, is in dstadr in the association. See the behavior on howland, 
which is receiving multicast from two servers. The first time the 
multicast is received, the association is mobilized correctly. It sends 
a client message to the server as expected. Somewhere between there and 
the server response the dstadr is changed to the multicast address and 
the volley fails.

I repeat. The dstadr is set correctly in newpeer(). It is not changed 
anywhere else in ntp_peer.c or ntp_proto.c. Something, either in a macro 
or in ntp_io.c is changing it. It should never be changed by anything 
after newpeer().

In principle, it would be possible to mobilize and continue the 
assocation by including a novolley keyword on the multicast command in 
the configuration file. Unfortunately, the syntax of that command can't 
currently do that. The items following the multicast keyword must be 
only group addresses.


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