Subject: Re: Local IP addresses changing
To: Dennis Ferguson <>
From: Matt Thomas <>
List: tech-net
Date: 08/25/2000 11:04:59
At 11:00 AM 8/25/2000 -0700, Dennis Ferguson wrote:
> > >This makes ntpd very unhappy, as it can't reach the remote servers 
> anymore.
> > >As a workaround I'm killing and restarting ntpd in my ip-up script, 
> but I'm
> > >wondering what the real solution would be.
> >
> > a better solution would be for ntpd use an ephemeral port for talking
> > to servers, just like ntpdate does, and then to close it after it's
> > done with a round of polling.  just my opinion.
>No, that doesn't fix the problem ntpd has.  ntpd's problem is that it
>needs to know the destination address in packets that it receives, and
>specify the source address for packets it sends.  The NTP specification
>demands this because of how it identifies associations.  ntpdate also
>strictly needs this information, but sleazes through without it since it
>doesn't maintain long-lived peer sessions.  The daemon can't do this.

Yes it can.  It could use the IP_RECVDSTADDR sockopt with recvmsg.  Then
for every packet it will get the dest addr in the control buffer.

Just a small matter of programming.
Matt Thomas               Internet:
3am Software Foundry      WWW URL:
Cupertino, CA             Disclaimer: I avow all knowledge of this message