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Subject[RFC] ARP notify option
This adds another inet device option to enable gratuitous ARP
when device is brought up or address change. This is handy for
clusters or virtualization.

Tested on a normal device (not Xen).

Signed-off-by: Stephen Hemminger <shemminge@linux-foundation.org>

---
Documentation/networking/ip-sysctl.txt | 6 ++++++
include/linux/inetdevice.h | 2 ++
include/linux/sysctl.h | 1 +
net/ipv4/devinet.c | 16 ++++++++++++++++
4 files changed, 25 insertions(+)
--- net-2.6.22.orig/Documentation/networking/ip-sysctl.txt 2007-03-05 14:35:31.000000000 -0800
+++ net-2.6.22/Documentation/networking/ip-sysctl.txt 2007-03-05 16:46:47.000000000 -0800
@@ -732,6 +732,12 @@
The max value from conf/{all,interface}/arp_ignore is used
when ARP request is received on the {interface}

+arp_notify - BOOLEAN
+ Define mode for notification of address and device changes.
+ 0 - (default): do nothing
+ 1 - Generate gratuitous arp replies when device is brought up
+ or hardware address changes.
+
arp_accept - BOOLEAN
Define behavior when gratuitous arp replies are received:
0 - drop gratuitous arp frames
--- net-2.6.22.orig/include/linux/inetdevice.h 2007-03-05 14:35:34.000000000 -0800
+++ net-2.6.22/include/linux/inetdevice.h 2007-03-05 16:46:47.000000000 -0800
@@ -26,6 +26,7 @@
int arp_announce;
int arp_ignore;
int arp_accept;
+ int arp_notify;
int medium_id;
int no_xfrm;
int no_policy;
@@ -84,6 +85,7 @@
#define IN_DEV_ARPFILTER(in_dev) (ipv4_devconf.arp_filter || (in_dev)->cnf.arp_filter)
#define IN_DEV_ARP_ANNOUNCE(in_dev) (max(ipv4_devconf.arp_announce, (in_dev)->cnf.arp_announce))
#define IN_DEV_ARP_IGNORE(in_dev) (max(ipv4_devconf.arp_ignore, (in_dev)->cnf.arp_ignore))
+#define IN_DEV_ARP_NOTIFY(in_dev) (ipv4_devconf.arp_notify || (in_dev)->cnf.arp_notify)

struct in_ifaddr
{
--- net-2.6.22.orig/include/linux/sysctl.h 2007-03-05 14:35:34.000000000 -0800
+++ net-2.6.22/include/linux/sysctl.h 2007-03-05 16:46:47.000000000 -0800
@@ -495,6 +495,7 @@
NET_IPV4_CONF_ARP_IGNORE=19,
NET_IPV4_CONF_PROMOTE_SECONDARIES=20,
NET_IPV4_CONF_ARP_ACCEPT=21,
+ NET_IPV4_CONF_ARP_NOTIFY=22,
__NET_IPV4_CONF_MAX
};

--- net-2.6.22.orig/net/ipv4/devinet.c 2007-03-05 14:35:34.000000000 -0800
+++ net-2.6.22/net/ipv4/devinet.c 2007-03-05 16:46:47.000000000 -0800
@@ -1089,6 +1089,14 @@
}
}
ip_mc_up(in_dev);
+ /* fall through */
+ case NETDEV_CHANGEADDR:
+ if (IN_DEV_ARP_NOTIFY(in_dev))
+ arp_send(ARPOP_REQUEST, ETH_P_ARP,
+ in_dev->ifa_list->ifa_address,
+ dev,
+ in_dev->ifa_list->ifa_address,
+ NULL, dev->dev_addr, NULL);
break;
case NETDEV_DOWN:
ip_mc_down(in_dev);
@@ -1495,6 +1503,14 @@
.proc_handler = &proc_dointvec,
},
{
+ .ctl_name = NET_IPV4_CONF_ARP_NOTIFY,
+ .procname = "arp_notify",
+ .data = &ipv4_devconf.arp_notify,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
+ {
.ctl_name = NET_IPV4_CONF_NOXFRM,
.procname = "disable_xfrm",
.data = &ipv4_devconf.no_xfrm,
-
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