Subject: PATCH to update proxy arp feature on shaper device

Author: Roberto Arcomano, berto@fatamorgana.com,
        http://www.fatamorgana.com/bertolinux

Date: 07/22/2001

Description: Shaper device is seen by the kernel like a 
             different device than the physical one to which
	     is attached to. So kernel always issues an 
	     "ARP REPLY" (if proxy arp is active): this
	     prevent us to enable proxy arp (on a shaper device)
	     and turn on machine cause we would receive
	     an "IP conflit".
	     
Solution: The patch investigates about the shaper device 
          (it compares string with "shaper"): if yes, we 
	  search the real interface attached to shaper
	  (we read value of priv->dev) and we use that to
	   make the classic proxy arp devices compare.

Problems: The patch uses routine "strncmp" which is not the
          best thing (I guess).
	
Tests: I tested new feature using 3 PC like that:

           CLIENT1  ----------- LINUX -----  CLIENT2
     	                  shaper0   ppp0
	                   [eth0]
	   
       LINUX host has proxy arp and shaper enabled, with
       a routing (using shaper0 interface) to CLIENT1
       If I use old feature, when I turn on CLIENT1 I receive
       an "IP conflit" by its OS, while using patched version
       I have no problem and proxy arp feature for CLIENT2
       works well (as right, I cannot assign CLIENT2 IP to
       CLIENT1 host).
       
       Kernel version tested is 2.4.6       
       
Final notes: It should be very simple to port patch to older
             kernel version (2.0.xx, 2.1.xx, 2.2.xx, 2.3.xx)