[ntp:questions] Re: sendto( Invalid argument

Edrusb edrusba at free.fr
Sat Aug 13 10:18:44 UTC 2005

David Woolley wrote:
> In article <hmvidd.pdc.ln at barnabe.home.fr>, Edrusb <edrusba at free.fr> wrote:
>>- What is the use of this wildcard UDP socket (it does not seems used)?
> Handles incoming requests?

Yes probably, it is too bad the same socket has not been used to send 
data too, just leting the system put the appropriate Source IP and 
select the adequate output interface according to system's routing 
decision. This way there would not have any need to scan available 
network interfaces for changes.

 >>- Why does ntpd uses theses UDP specific interfaces sockets, while the
 >>configuration file does not specify any interface to listen on or to not
 >>listen on?
 > I believe this is because the security features require the origin
 > address to be known by the sender (possibly only for servers).

the outgoing IP packets have their IP source field set by the system in 
any way I guess, even when sending from a wildcard socket.

>>Any help is (very) welcome. :-)
> As noted elsewhere, you can do IP address masquerading down stream so that
> ntpd sees a fixed address.

Thanks for the idea, but public servers still have static IP address :-) 
masquerading them would not help :-/

I have a "tap" interfaces that handles the traffic when the link is down 
for dial on demand (see "diald" interesting and powerful program), 
unfortunately, ntpd does not bind a socket to this interface! Too bad.

I guess, the best solution waiting for next ntpd release, as described 
by Steve Kostecke, is to have my local ntpd server for my local network 
be "inside" the network without any dynamic IP address.

Thansk to all,


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