net: add ARP notify option for devices

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.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 18 insertions, 0 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index c7712787933c..ff3f219ee4d7 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -782,6 +782,12 @@ arp_ignore - INTEGER
         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
diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
index 06fcdb45106b..acef2a770b6b 100644
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h
@@ -108,6 +108,7 @@ static inline void ipv4_devconf_setall(struct in_device *in_dev)
 #define IN_DEV_ARPFILTER(in_dev)        IN_DEV_ORCONF((in_dev), ARPFILTER)
 #define IN_DEV_ARP_ANNOUNCE(in_dev)     IN_DEV_MAXCONF((in_dev), ARP_ANNOUNCE)
 #define IN_DEV_ARP_IGNORE(in_dev)       IN_DEV_MAXCONF((in_dev), ARP_IGNORE)
+#define IN_DEV_ARP_NOTIFY(in_dev)       IN_DEV_MAXCONF((in_dev), ARP_NOTIFY)
 
 struct in_ifaddr
 {
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 39d471d1163b..e76d3b22a466 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -490,6 +490,7 @@ enum
         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
 };
 
diff --git a/kernel/sysctl_check.c b/kernel/sysctl_check.c
index fafeb48f27c0..b38423ca711a 100644
--- a/kernel/sysctl_check.c
+++ b/kernel/sysctl_check.c
@@ -219,6 +219,7 @@ static const struct trans_ctl_table trans_net_ipv4_conf_vars_table[] = {
         { NET_IPV4_CONF_ARP_IGNORE,             "arp_ignore" },
         { NET_IPV4_CONF_PROMOTE_SECONDARIES,    "promote_secondaries" },
         { NET_IPV4_CONF_ARP_ACCEPT,             "arp_accept" },
+        { NET_IPV4_CONF_ARP_NOTIFY,             "arp_notify" },
         {}
 };
 
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 309997edc8a5..d519a6a66726 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1075,6 +1075,14 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
                         }
                 }
                 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);
@@ -1439,6 +1447,7 @@ static struct devinet_sysctl_table {
                 DEVINET_SYSCTL_RW_ENTRY(ARP_ANNOUNCE, "arp_announce"),
                 DEVINET_SYSCTL_RW_ENTRY(ARP_IGNORE, "arp_ignore"),
                 DEVINET_SYSCTL_RW_ENTRY(ARP_ACCEPT, "arp_accept"),
+                DEVINET_SYSCTL_RW_ENTRY(ARP_NOTIFY, "arp_notify"),
 
                 DEVINET_SYSCTL_FLUSHING_ENTRY(NOXFRM, "disable_xfrm"),
                 DEVINET_SYSCTL_FLUSHING_ENTRY(NOPOLICY, "disable_policy"),