Re: PATCH: duplicate IP detection

Marc Merlin (marc_news@merlins.org)
Sun, 17 Oct 1999 11:55:45 -0700


On dim, oct 17, 1999 at 10:35:36 +0400, kuznet@ms2.inr.ac.ru wrote:
> Hello!
>
> > We've decided that "refusing to use the given IP" is not good, and
> > that at most we can print a warning, and continue. Fine.
>
> It is not fine. Failed DAD means that you have no rights to use
> this address.

Alexey, we're not trying to find out if we can use an address, my patch
simply finds out passively if anyone stole ours. It's simple and it's non
intrusive.
You say "Broken switches may send our on ARP queries back to us"
I say "Ok, I'll ignore ARP packets that have our own MAC address"

I fail to see what you don't like in my patch. It will not catch all IP
stealing cases, as I explained earlier, but it will get most of them and for
very little cost.

> > If you're right the patch may need to be extended and check if the
> > hardware address is one of our own.
>
> Please, make "man arpwatch" and read that page.

I use arpwatch already, it doesn't do the same thing. One of the big
differences is that it puts your interface in promiscuous mode. My patch
doesn't.

> We need not add to kernel any dirty tricks to make this and even more
> sophisticated monitoring. Actually, it is even easy to write X applet
> spewing window at X display looking exactly as Windows' one 8)8)

I fail to see why you see my check as a dirty trick. Note also that it's not
just windows that detects duplicate IPs, it's virtually all the other Unices
I've worked with (including Irix and Solaris).
Of course, it's then trivial to write some program that monitors syslog and
displays some X window with a more readable warning (Irix does that already)

Marc

-- 
Microsoft is to software what McDonalds is to gourmet cooking
 
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