Messages in this thread | | | Date | Wed, 29 Sep 1999 19:47:12 -0700 (PDT) | From | "B. James Phillippe" <> | Subject | Re: Why no printk for duplicate IPs? |
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On Wed, 29 Sep 1999, Christopher McCrory wrote:
> > The way I've seen this done (on BSDI boxen, I think) is that the system > > does an arp for it's own IP address before/as the interface is brought ... > This IIRC is a gratuitous arp.
Correct.
> In the kernel source I have seen references to it but I have never > actually seen on used in a linux box. I first noticed this when moving a ... > Would this be the responsibiliy of the kernel in kernel space or ifconfig > in user space?
I implemented it in user-space for our Linux-based firewall, so that when proxy-ARP was enabled, the ARP caches of other hosts on the LAN would be advised of the new MAC address. There is a tacky little demo program that you can start from at http://www.terran.org/~bryan/prog/files/garp.c or also at ftp://linux.watchguard.com/pub/watchguard/watchguard/garp.c. It should not be hard to modify the program to then watch for replies and raise a warning/syslog message about duplicate IP's.
-bp -- # bryan at terran dot org # http://www.terran.org/~bryan
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