Bug 32816

Summary: ntpd/ntpdc incompatibility across the last two versions
Product: Base System Reporter: Yar Tikhiy <yar>
Component: binAssignee: freebsd-bugs (Nobody) <bugs>
Status: Closed FIXED    
Severity: Affects Only Me    
Priority: Normal    
Version: 4.4-STABLE   
Hardware: Any   
OS: Any   

Description Yar Tikhiy 2001-12-13 23:30:00 UTC 
If the older ntpdc is used to talk to the newer ntpd or vice versa,
a packet format error occurs.  That's while no such incompatibility
has been announced.

Fix: 

At least, document the incompatibility.
How-To-Repeat: 
yar@A$ ntpdc B
ntpdc> peers
***Server reports a format error in the received packet (shouldn't happen)
Comment 1 Garrett A. Wollman 2001-12-13 23:47:00 UTC 
<<On Fri, 14 Dec 2001 02:23:32 +0300 (MSK), Yar Tikhiy <yar@comp.chem.msu.su> said:

> If the older ntpdc is used to talk to the newer ntpd or vice versa,
> a packet format error occurs.  That's while no such incompatibility
> has been announced.

ntpdc is never compatible across versions of ntpd, except by
fortuitous coincidence.  Dave Mills has made it clear that ntpdc's
mode 7 control messages are specific to the version of ntpd.

-GAWollman
Comment 2 Yar Tikhiy freebsd_committer freebsd_triage 2001-12-14 00:42:23 UTC 
On Thu, Dec 13, 2001 at 06:47:00PM -0500, Garrett Wollman wrote:
> <<On Fri, 14 Dec 2001 02:23:32 +0300 (MSK), Yar Tikhiy <yar@comp.chem.msu.su> said:
> 
> > If the older ntpdc is used to talk to the newer ntpd or vice versa,
> > a packet format error occurs.  That's while no such incompatibility
> > has been announced.
> 
> ntpdc is never compatible across versions of ntpd, except by
> fortuitous coincidence.  Dave Mills has made it clear that ntpdc's
> mode 7 control messages are specific to the version of ntpd.

Has he in a man page or private mail?

ntpdc(8) reads:

     ntpdc uses NTP mode 7 packets to communicate with the NTP
     server, and hence can be used to query any compatible server
     on the network which permits it.

The same page reads somewhat later:

     The operation of ntpdc is specific to the particular
implementation
     of the ntpd(8) daemon and can be expected to work only with
     this and maybe some previous versions of the daemon.

Looks rather ambiguous.  To my mind, the FreeBSD ntpd maintainer
could do something about that, e.g., contact Dave Mills so he
clarifies the issue in the man page.  The sentence "ntpdc version
must match that of ntpd exactly" would do much better IMHO than
the current explanation.

-- 
Yar
Comment 3 Crist J. Clark freebsd_committer freebsd_triage 2001-12-17 11:27:29 UTC 
State Changed
From-To: open->closed

The documentation on ntpdc(8) seems pretty clear, 

The operation of ntpdc are specific to the particular implementation of 
the ntpd(8) daemon and can be expected to work only with this and maybe 
some previous versions of the daemon. 

The two versions in the PR are ones that do not play well together.