netdev - [PATCH 2/3] arp_notify: allow drivers to explicitly request a notification event.

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Message-Id: <1274868583-26291-2-git-send-email-ian.campbell@citrix.com>
Date:	Wed, 26 May 2010 11:09:42 +0100
From:	Ian Campbell <ian.campbell@...rix.com>
To:	netdev@...r.kernel.org
Cc:	Ian Campbell <ian.campbell@...rix.com>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	"David S. Miller" <davem@...emloft.net>, stable@...nel.org
Subject: [PATCH 2/3] arp_notify: allow drivers to explicitly request a notification event.

Currently such notifications are only generated when the device comes up or the
address changes. However one use case for these notifications is to enable
faster network recovery after a virtual machine migration (by causing switches
to relearn their MAC tables). A migration appears to the network stack as a
temporary loss of carrier and therefore does not trigger either of the current
conditions. Rather than adding carrier up as a trigger (which can cause issues
when interfaces a flapping) simply add an interface which the driver can use
to explicitly trigger the notification.

Signed-off-by: Ian Campbell <ian.campbell@...rix.com>
Cc: Stephen Hemminger <shemminger@...ux-foundation.org>
Cc: Jeremy Fitzhardinge <jeremy@...p.org>
Cc: David S. Miller <davem@...emloft.net>
Cc: netdev@...r.kernel.org
Cc: stable@...nel.org
---
 include/linux/netdevice.h |    2 ++
 include/linux/notifier.h  |    1 +
 net/ipv4/devinet.c        |    1 +
 net/sched/sch_generic.c   |   18 ++++++++++++++++++
 4 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index fa8b476..4737996 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1661,6 +1661,8 @@ extern void netif_carrier_on(struct net_device *dev);
 
 extern void netif_carrier_off(struct net_device *dev);
 
+extern void netif_notify_peers(struct net_device *dev);
+
 /**
  *	netif_dormant_on - mark device as dormant.
  *	@dev: network device
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index fee6c2f..45477f2 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -203,6 +203,7 @@ static inline int notifier_to_errno(int ret)
 #define NETDEV_BONDING_NEWTYPE  0x000F
 #define NETDEV_POST_INIT	0x0010
 #define NETDEV_UNREGISTER_BATCH 0x0011
+#define NETDEV_NOTIFY_PEERS	0x0012
 
 #define SYS_DOWN	0x0001	/* Notify of system down */
 #define SYS_RESTART	SYS_DOWN
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 90e3d63..c12777f 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1081,6 +1081,7 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
 		}
 		ip_mc_up(in_dev);
 		/* fall through */
+	case NETDEV_NOTIFY_PEERS:
 	case NETDEV_CHANGEADDR:
 		/* Send gratuitous ARP to notify of link change */
 		if (IN_DEV_ARP_NOTIFY(in_dev)) {
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index ff4dd53..2d7ca9e 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -325,6 +325,24 @@ void netif_carrier_off(struct net_device *dev)
 }
 EXPORT_SYMBOL(netif_carrier_off);
 
+/**
+ * 	netif_notify_peers - notify network peers about existence of @dev
+ * 	@dev: network device
+ *
+ * Generate traffic such that interested network peers are aware of
+ * @dev, such as by generating a gratuitous ARP. This may be used when
+ * a device wants to inform the rest of the network about some sort of
+ * reconfiguration such as a failover event or virtual machine
+ * migration.
+ */
+void netif_notify_peers(struct net_device *dev)
+{
+	rtnl_lock();
+	call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, dev);
+	rtnl_unlock();
+}
+EXPORT_SYMBOL(netif_notify_peers);
+
 /* "NOOP" scheduler: the best scheduler, recommended for all interfaces
    under all circumstances. It is difficult to invent anything faster or
    cheaper.
-- 
1.5.6.5

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