[ntp:hackers] Findinterface

mayer mayer at gis.net
Mon Jun 13 05:32:02 PDT 2005


----- Original Message Follows -----
> Hi Brad,
> 
> Brad Knowles schrieb:
> 
> > At 8:10 AM +0200 2005-06-10, Heiko Gerstung wrote:
> >
> >>  Sorry that I miss the point, but if auth is related to the IP 
> >> address, why
> >>  do we need to find the physical interface for an association? The
> IP >>  address of the sender and the receiver should be available in
> every  >> packet
> >>  we receive, no matter over which interface we receive it, right?
> >
> >
> >     My understanding is that this is not true by the time the IP
> > stack  has done it's job of unwrapping the package.  You'll have the
> > source  IP but not the target IP, so you won't know the interface,
> > which means  that you can't guarantee that the response will go out
> > the same  interface and from the same target (now source) IP.
> 
> To me it feels like we are dealing with something we shouldn't need to
> take care of. Why do we need to bother which interface is used to send
> a  package to someone? Isn't that something the "routing functions" in
> our  "kernel" are responsible for?
> 

In this case no. We need to send the packet on a specific interface and
in the case of *cast we need to figure out which interface we need to
have join the group.

> >     You have to back-track to figure how to fill in the missing
> bits.
> 
> If you really need them, but I doubt that. I'd like to learn why I'm 
> wrong and I kindly ask all of you to educate me :-)
> 

Autokey requires it. It has to use a specific IP address in order to
work.

Danny
> Thanks for your patience,
> kind regards,
> Heiko
> 
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