[ntp:questions] Re: Are broadcasts by non-responsive servers used by clients?

David L. Mills mills at udel.edu
Fri Oct 1 22:02:37 UTC 2004


Rod,

There was a bug, fixed some time back, that could result in your 
behavior. At the time of bugfix an option "novolley" was added to the 
broadcastclient command. It disables any messages sent to the broadcast 
server. Note that public key authentication doesn't work without the volley.

Dave

Rod wrote:
> I have a question regarding ntp broadcast operation as described on the
> Association Management page.  The description:
> 
> "Once the offset is computed, the server continues as before and the client
> sends no further messages. If for some reason the broadcast server does not
> respond to client messages, the client will time out the volley and continue 
> in listen-only mode with a default propagation delay."
> 
> Does this mean if the broadcast server does not respond that the broadcast
> client will yet use the broadcasts to update its clock?  That'd be the 
> behavior I'd expect, but do not find.
> 
> I've set up an ntp broadcast through a one-way link, and the broadcast 
> client initiates a volley which times out after 8 failed messages, but it
> never uses the broadcast time.  The broadcast client ntpd writes 
> "ntpd[6263]: recvfrom() fd=6: No route to host" to /var/log/messages,
> which is expected.
> 
> Some checks on the system:  ethereal shows the packets arriving at the 
> client at stratum 3, and iptables -Lv shows that the packets make it 
> through the client firewall.  Subsequently, I've disabled the firewall 
> on the client, and the ntp broadcast client still does not use the ntp
> broadcasts.
> 
> Any help is appreciated!
> 
> Rod
> ________________________________________________________________________
> ntp config files:
> # Broadcast server
> restrict default ignore
> 
> restrict 127.0.0.1
> 
> broadcast 158.184.160.255 minpoll 4
> 
> # Time from the stratum 2 servers:
> server 158.184.160.2
> restrict 158.184.160.2 mask 255.255.255.255 nomodify notrap noquery
> 
> server 158.184.160.3
> restrict 158.184.160.3 mask 255.255.255.255 nomodify notrap noquery
> 
> fudge   127.127.1.0 stratum 10
> 
> driftfile /etc/ntp/drift
> broadcastdelay  0.008
> 
> authenticate no
> 
> keys            /etc/ntp/keys
> 
> ________________________________________________________________________
> # The broadcast client.
> server  127.127.1.0     # local clock
> fudge   127.127.1.0 stratum 10
> 
> broadcastdelay  0.008
> broadcastclient
> 
> authenticate no
> ________________________________________________________________________
> /sbin/ifconfig on the client:
> eth0    inet addr:158.184.160.217  Bcast:158.184.160.255  Mask:255.255.255.0




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