Re: [PATCH] arp_filter patch for 2.4.4 kernel.

[Ben Greear]

Matthew Kirkwood wrote:
> 
> On Sat, 5 May 2001, David S. Miller wrote:
> 
> >  > It adds the ability to run multiple interfaces on the same subnet,
> >  > on the same machine, and have the ARPs for each interface be answered
> >  > based on whether or not the kernel would route a packet from the ARP'd
> >  > IP out that interface.  When used with source-based routing, this
> >  > makes things work in an intuitive manner.
> >
> > How difficult is it to compose netfilter rules that do this?
> 
> I want this feature precisely /because/ it interferes with
> packet filtering.

It looks like several people, including me, like this patch,
or at least a similar patch.  This patch would also add a feature
to the 2.4 series that is missing, with regard to the 2.2.19
kernel.  If it was good enough for 2.2.19, shouldn't it be good
enough for 2.4?

If anyone has any particular gripes about the patch, lets
see if we can work them out instead of just letting the topic
drown silently in the flood of LK.

I'm re-attaching the patch in case that helps.....

 diff -u -r -N -X /home/greear/exclude.list linux/include/linux/inetdevice.h linux.dev/include/linux/inetdevice.h
--- linux/include/linux/inetdevice.h	Mon Aug 23 10:01:02 1999
+++ linux.dev/include/linux/inetdevice.h	Wed May  2 23:04:58 2001
@@ -17,6 +17,7 @@
 	int	forwarding;
 	int	mc_forwarding;
 	int	tag;
+        int     arp_filter;
 	void	*sysctl;
 };
 
@@ -53,6 +54,9 @@
 	  (ipv4_devconf.accept_redirects && (in_dev)->cnf.accept_redirects)) \
 	 || (!IN_DEV_FORWARD(in_dev) && \
 	  (ipv4_devconf.accept_redirects || (in_dev)->cnf.accept_redirects)))
+
+#define IN_DEV_ARPFILTER(in_dev)       (ipv4_devconf.arp_filter || (in_dev)->cnf.arp_filter)
+
 
 struct in_ifaddr
 {
diff -u -r -N -X /home/greear/exclude.list linux/include/linux/sysctl.h linux.dev/include/linux/sysctl.h
--- linux/include/linux/sysctl.h	Fri Apr 27 15:48:20 2001
+++ linux.dev/include/linux/sysctl.h	Wed May  2 23:52:46 2001
@@ -324,7 +324,8 @@
 	NET_IPV4_CONF_ACCEPT_SOURCE_ROUTE=9,
 	NET_IPV4_CONF_BOOTP_RELAY=10,
 	NET_IPV4_CONF_LOG_MARTIANS=11,
-	NET_IPV4_CONF_TAG=12
+	NET_IPV4_CONF_TAG=12,
+        NET_IPV4_CONF_ARPFILTER=13
 };
 
 /* /proc/sys/net/ipv6 */
diff -u -r -N -X /home/greear/exclude.list linux/include/net/snmp.h linux.dev/include/net/snmp.h
--- linux/include/net/snmp.h	Fri Apr 27 15:48:20 2001
+++ linux.dev/include/net/snmp.h	Wed May  2 23:54:14 2001
@@ -198,7 +198,8 @@
 	unsigned long	RcvPruned;
 	unsigned long	OfoPruned;
 	unsigned long	OutOfWindowIcmps; 
-	unsigned long	LockDroppedIcmps; 
+	unsigned long	LockDroppedIcmps;
+        unsigned long   ArpFilter;
 	unsigned long	TimeWaited; 
 	unsigned long	TimeWaitRecycled; 
 	unsigned long	TimeWaitKilled; 
diff -u -r -N -X /home/greear/exclude.list linux/net/ipv4/arp.c linux.dev/net/ipv4/arp.c
--- linux/net/ipv4/arp.c	Thu Apr 12 12:11:39 2001
+++ linux.dev/net/ipv4/arp.c	Thu May  3 00:13:37 2001
@@ -343,6 +343,26 @@
 		read_unlock_bh(&neigh->lock);
 }
 
+static int arp_filter(__u32 sip, __u32 tip, struct net_device *dev)
+{
+       struct rtable *rt;
+       int flag = 0; 
+       /*unsigned long now; */
+
+       if (ip_route_output(&rt, sip, tip, 0, 0) < 0) 
+               return 1;
+       if (rt->u.dst.dev != dev) { 
+               /* TODO:  Figure out what this is supposed to do and re-insert it:
+                *
+                * net_statistics.ArpFilter++;
+                *
+                */
+               flag = 1; 
+       } 
+       ip_rt_put(rt); 
+       return flag; 
+} 
+
 /* OBSOLETE FUNCTIONS */
 
 /*
@@ -739,7 +759,13 @@
 		if (addr_type == RTN_LOCAL) {
 			n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
 			if (n) {
-				arp_send(ARPOP_REPLY,ETH_P_ARP,sip,dev,tip,sha,dev->dev_addr,sha);
+                                int dont_send = 0;
+                                if (IN_DEV_ARPFILTER(in_dev)) {
+                                      dont_send |= arp_filter(sip,tip,dev); 
+                                }
+                                if (!dont_send) {
+                                      arp_send(ARPOP_REPLY,ETH_P_ARP,sip,dev,tip,sha,dev->dev_addr,sha);
+                                }
 				neigh_release(n);
 			}
 			goto out;
diff -u -r -N -X /home/greear/exclude.list linux/net/ipv4/devinet.c linux.dev/net/ipv4/devinet.c
--- linux/net/ipv4/devinet.c	Sun Mar 25 19:14:25 2001
+++ linux.dev/net/ipv4/devinet.c	Wed May  2 23:27:47 2001
@@ -1016,7 +1016,7 @@
 static struct devinet_sysctl_table
 {
 	struct ctl_table_header *sysctl_header;
-	ctl_table devinet_vars[13];
+	ctl_table devinet_vars[14];
 	ctl_table devinet_dev[2];
 	ctl_table devinet_conf_dir[2];
 	ctl_table devinet_proto_dir[2];
@@ -1059,7 +1059,10 @@
 	{NET_IPV4_CONF_TAG, "tag",
 	 &ipv4_devconf.tag, sizeof(int), 0644, NULL,
 	 &proc_dointvec},
-	 {0}},
+        {NET_IPV4_CONF_ARPFILTER, "arp_filter",
+         &ipv4_devconf.arp_filter, sizeof(int), 0644, NULL,
+         &proc_dointvec},
+        {0}},
 
 	{{NET_PROTO_CONF_ALL, "all", NULL, 0, 0555, devinet_sysctl.devinet_vars},{0}},
 	{{NET_IPV4_CONF, "conf", NULL, 0, 0555, devinet_sysctl.devinet_dev},{0}},
diff -u -r -N -X /home/greear/exclude.list linux/net/ipv4/proc.c linux.dev/net/ipv4/proc.c
--- linux/net/ipv4/proc.c	Thu Aug 10 13:01:26 2000
+++ linux.dev/net/ipv4/proc.c	Wed May  2 23:12:57 2001
@@ -170,7 +170,7 @@
 	len = sprintf(buffer,
 		      "TcpExt: SyncookiesSent SyncookiesRecv SyncookiesFailed"
 		      " EmbryonicRsts PruneCalled RcvPruned OfoPruned"
-		      " OutOfWindowIcmps LockDroppedIcmps"
+		      " OutOfWindowIcmps LockDroppedIcmps ArpFilter"
 		      " TW TWRecycled TWKilled"
 		      " PAWSPassive PAWSActive PAWSEstab"
 		      " DelayedACKs DelayedACKLocked DelayedACKLost"

Thanks,
Ben

-- 
Ben Greear <[e-mail]>          <[e-mail]>
President of Candela Technologies Inc      http://www.candelatech.com
ScryMUD:  http://scry.wanfear.com     http://scry.wanfear.com/~greear