Patch suggestion for proxy arp on shaper interface

[Roberto Arcomano <berto@fatamorgana.com>]

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Hi all,
Recently I have had a problem with Linux proxy arp feature (using with shaper 
interface): when I machine starts up it was receiving a "IP conflits".
The problem is that Linux proxy_arp routine doesn't make difference between 
real interface (i.e. eth0) and shaper interface (i.e. shaper0 which has been 
attached to eth0).
I attach a first beta solution to the problem, which could be far from 
optimal! (I use a "strncmp", cause I didn't found another method to know if 
the device is a "shaper" device).


--- arp.c.orig  Wed May 16 19:21:45 2001
+++ arp.c       Sun Jul 22 19:31:20 2001
@@ -111,7 +111,7 @@
 
 #include <asm/system.h>
 #include <asm/uaccess.h>
-
+#include <linux/if_shaper.h>
 
 
 /*
@@ -767,10 +767,17 @@
                        }
                        goto out;
                } else if (IN_DEV_FORWARD(in_dev)) {
+                        char shflag=0;
+                        if ( (rt->u.dst.dev) &&
+                            (rt->u.dst.dev->priv) &&
+                            (((struct shaper *) rt->u.dst.dev->priv)->dev) &&
+                            (strncmp(rt->u.dst.dev->name,"shaper",6)==0) )
+                         shflag=1;
                        if ((rt->rt_flags&RTCF_DNAT) ||
-                           (addr_type == RTN_UNICAST  && rt->u.dst.dev != 
dev &&
+                           (addr_type == RTN_UNICAST  &&
+                           ( ((shflag) && ( ((struct shaper *) 
rt->u.dst.dev->priv)->dev != dev)) || ((!shflag) && (rt->u.dst.dev != dev)) ) 
&&
                             (IN_DEV_PROXY_ARP(in_dev) || 
pneigh_lookup(&arp_tbl, &tip, dev, 0)))) {
-                               n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
+                               n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
                                if (n)


The patch declare a variable (flag to know if the interface is shaper-like), 
investigate on private data of shaper device (where we can know what is the 
attached interface) and set the flag. After we consider the "attached" 
interface if flag is set.

I tested it under 2.4.6 on RedHat 7.1 with success (there is no more IP 
conflit).
Hope it'll useful.

Best Regards
Roberto Arcomano

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--- arp.c.orig	Wed May 16 19:21:45 2001
+++ arp.c	Sun Jul 22 19:31:20 2001
@@ -111,7 +111,7 @@
 
 #include <asm/system.h>
 #include <asm/uaccess.h>
-
+#include <linux/if_shaper.h>
 
 
 /*
@@ -767,10 +767,17 @@
 			}
 			goto out;
 		} else if (IN_DEV_FORWARD(in_dev)) {
+                        char shflag=0;
+                        if ( (rt->u.dst.dev) &&
+			     (rt->u.dst.dev->priv) &&
+			     (((struct shaper *) rt->u.dst.dev->priv)->dev) &&
+			     (strncmp(rt->u.dst.dev->name,"shaper",6)==0) )
+			  shflag=1;
 			if ((rt->rt_flags&RTCF_DNAT) ||
-			    (addr_type == RTN_UNICAST  && rt->u.dst.dev != dev &&
+			    (addr_type == RTN_UNICAST  && 
+			    ( ((shflag) && ( ((struct shaper *) rt->u.dst.dev->priv)->dev != dev)) || ((!shflag) && (rt->u.dst.dev != dev)) ) &&
 			     (IN_DEV_PROXY_ARP(in_dev) || pneigh_lookup(&arp_tbl, &tip, dev, 0)))) {
-				n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
+			        n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
 				if (n)
 					neigh_release(n);