[ntp:questions] Re: Multicast TTL and FreeBSD trouble
David L. Mills
mills at udel.edu
Sun Aug 21 21:26:34 UTC 2005
I was referring to the ttl vector and increments, which hasn't changed.
The peer->ttl structure member is not used for its original purpose; it
is used as a flag value for some reference clocks. The naming is
The sendpkt() semantics for ttl did change. There was no room in the
configuration structure for a per-peer ttl mechanism, so it had to be a
system variable. Another victim of the configuration mess.
Per Hedeland wrote:
> In article <4308D64E.6030007 at gis.net> mayer at gis.net (Danny Mayer) writes:
>>David L. Mills wrote:
>>>Wash your mouth with soap. The scheme does not conform to the anycast
>>>model; it does conform to the manycast model, where the intent is to
>>>capture a plurality of servers, not just a single one. I have not
>>>changed the ttl code in a decade. If it behaves differently in Linux and
>>>FreeBSD, somebody else has changed the code or the operating system has
>>>a mind of its own.
>>Nothing to wash, Dave. I know it hasn't changed. I agree that getting
>>different results on different O/S's indicates an O/S problem rather
>>than an ntp problem. I have yet to look at the manycast model, too many
>>other things to work on...
> Uh, I know that there are issues with the source code management for the
> reference implementation, but this is getting silly. Here are excerpts
> from a diff between 4.1.2 and 4.2.0, both downloaded from ftp.udel.edu:
> --- ntp-4.1.2/ntpd/ntp_proto.c Thu Jan 17 22:27:47 2002
> +++ ntp-4.2.0/ntpd/ntp_proto.c Tue Oct 7 12:21:39 2003
> HTONL_FP(&peer->xmt, &xpkt.xmt);
> - sendpkt(&peer->srcadr, peer->dstadr, peer->ttl, &xpkt,
> - sendlen);
> + sendpkt(&peer->srcadr, peer->dstadr, sys_ttl[peer->ttl],
> + &xpkt, sendlen);
> - sendpkt(&peer->srcadr, peer->dstadr, peer->ttl, &xpkt, sendlen);
> + sendpkt(&peer->srcadr, peer->dstadr, sys_ttl[peer->ttl], &xpkt,
> + sendlen);
> Sure looks like a significant change to me... - maybe not to the
> manycast model, but then no-one has been suggesting that there are
> problems with that. The issue at hand is the semantics of the 'ttl'
> option for the 'broadcast' command.
> --Per Hedeland
> per at hedeland.org
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