[PATCH] net: add ARP notify option for devices

[Jeremy Fitzhardinge]

From: Stephen Hemminger <shemminger@xxxxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
Documentation/networking/ip-sysctl.txt |    6 ++++++
include/linux/inetdevice.h             |    1 +
include/linux/sysctl.h                 |    1 +
kernel/sysctl_check.c                  |    1 +
net/ipv4/devinet.c                     |    9 +++++++++
5 files changed, 18 insertions(+)

===================================================================
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -782,6 +782,12 @@
	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
===================================================================
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h
@@ -108,6 +108,7 @@
#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
{
===================================================================
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -490,6 +490,7 @@
	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
};

===================================================================
--- a/kernel/sysctl_check.c
+++ b/kernel/sysctl_check.c
@@ -219,6 +219,7 @@
	{ 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" },
	{}
};

===================================================================
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1075,6 +1075,14 @@
			}
		}
		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);
@@ -1439,6 +1447,7 @@
		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"),


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