net/ipv4/arp.c, kernel 2.4.6 - PROXY_ARP bug on shaper device

This patch should update proxy arp feature for shaper device: it should correct proxy arp bug when talking with shaper device. Details are in README file attached:
Thank you for your support.
Best Regards
Roberto Arcomano

@@ -111,6 +111,7 @@
 
 #include <asm/system.h>
 #include <asm/uaccess.h>
+#include <linux/if_shaper.h>
 
 
 

@@ -767,8 +768,15 @@
 			}
 			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);
 				if (n)

Subject: PATCH to update proxy arp feature on shaper device

Author: Roberto Arcomano, [email protected],
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)

This is gross, make a device flag and have shaper set that flag during shaper device init, then have ARP test it.

Make the name of the flag reflect what the attribute is that shaper has (and potentially other devices could have) which makes this ARP special case necessary. Ie. don't name the flag NETIF_F_SHAPER :-)

Later,
David S. Miller
[email protected]