proxyarp for shaper device, kernel 2.4.9

I report here a tested and working patch to manage proxy arp on shaper device. Details are on readme.txt file attached.
I had problems using only a patch file, if someone could tell me what is the right command to make a diff file for all kernel source tree.... (I tried with "diff -ur tree.orig tree.modified > diff_file" but also other useless data are reported... :-()
Thank you
Best Regards
Roberto Arcomano

Subject: PATCH to update proxy arp feature on shaper device

Author: Roberto Arcomano, [email protected],
http://www.fatamorgana.com/bertolinux

Date: 9/9/2001

Description: Shaper device is seen by the kernel like a
different device (i.e. shaper0) than the physical one (i.e. eth0) to which is attached:
so kernel always issues an "ARP REPLY" (if proxy arp is active on shaper physical interface): this prevent us from use proxy arp on a shaper device cause, during turning on client machine, we would receive an "IP conflit" message.

Solution: Patch consists in 4 files:
a-) "include/linux/netdevice.h", where we add a new
net feature, NETIF_F_SHAPER which will help us to understand if a device is a shaper one.

b-) "drivers/net/shaper.c", in "shaper_probe" function
we set NETIF_F_SHAPER flag for a new shaper device.

c-) "include/linux/if_shaper.h" where we add the macro
IS_SHAPERDEVICE, used to know if the device is a shaper one (it checks NETIF_F_SHAPER flag in features field, under "netdevice" struct).

d-) "net/ipv4/arp.c" where finally we modify proxy arp;
We use shflag to determine if we are managing a shaper device (with IS_SHAPERDEVICE macro): in this case we check "rt->u.dst.dev->priv->dev" (physical device) instead of
"rt->u.dst.dev" (shaper device)
while if the device is a non shaper one, we check rt->u.dst.dev (anded with !shflag)

TODO: I used "features" field in netdevice struct: maybe it could
be choosen another place where to put the shaper flag.

Tests: I tested new feature using 3 PCs like that:

CLIENT1 ------------- LINUX ------------- CLIENT2
shaper0 ppp0
[eth0]

LINUX host has proxy arp and shaper enabled, with CLIENT1 reachable via shaper0.
With classic proxy arp, when I turn on CLIENT machine I receive an "IP conflit" from OS, while using patched version there are no problems.
Proxy arp still does its work cause, if I give CLIENT2 IP address to CLIENT1 machine, I receive (from CLIENT1 OS) a IP busy message.

Also tests on commercial server have been done with good results.

Kernel version tested is 2.4.9

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)

@@ -670,6 +670,7 @@
 	dev->addr_len		= 0;
 	dev->tx_queue_len	= 10;
 	dev->flags		= 0;
+	dev->features		|= NETIF_F_SHAPER;
 		
 	/*
 	 *	Shaper is ok

@@ -345,6 +345,7 @@
 #define NETIF_F_DYNALLOC	16	/* Self-dectructable device. */
 #define NETIF_F_HIGHDMA		32	/* Can DMA to high memory. */
 #define NETIF_F_FRAGLIST	64	/* Scatter/gather IO. */
+#define NETIF_F_SHAPER  	128	/* Shaper device. */
 
 	/* Called after device is detached from network. */
 	void			(*uninit)(struct net_device *dev);

@@ -14,6 +14,8 @@
 #define SHAPER_MAXSLIP	2
 #define SHAPER_BURST	(HZ/50)		/* Good for >128K then */
 
+#define IS_SHAPERDEVICE(dev) ((dev)->features & NETIF_F_SHAPER)
+
 struct shaper
 {
 	struct sk_buff_head sendq;

@@ -111,8 +111,7 @@
 
 #include <asm/system.h>
 #include <asm/uaccess.h>
-
-
+#include <linux/if_shaper.h>
 
 /*
  *	Interface to generic neighbour cache.

@@ -767,8 +766,15 @@
 			}
 			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) &&
+			     (IS_SHAPERDEVICE(rt->u.dst.dev)) )
+			  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)