net: add ARP notify option for devices

From: Stephen Hemminger <[email protected]>

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.

---

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(+)

===================================================================

@@ -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
===================================================================

@@ -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
{
===================================================================

@@ -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
};

===================================================================

@@ -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" },
	{}
};

===================================================================

@@ -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"),

From: Jeremy Fitzhardinge <[email protected]>
Date: Thu, 29 Jan 2009 10:49:26 -0800

I'm fine with this, applied, thanks.