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@citrix.com>
Cc: Stephen Hemminger <shemminger@linux-foundation.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Cc: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 40291f3750247dfa12102178a6aed457e7735516..a24916156f4e69f50a912d061f17726d2e2a8af2 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1772,6 +1772,8 @@ 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 540703b555cb2be4bbea2d8e7f0b84d96ca3b474..22c2abb619740b39712ac12ae0030dc6f8cf1a0e 100644 (file)
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -210,6 +210,7 @@ static inline int notifier_to_errno(int ret)
 #define NETDEV_POST_INIT       0x0010
 #define NETDEV_UNREGISTER_BATCH 0x0011
 #define NETDEV_BONDING_DESLAVE  0x0012
+#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 382bc768ed565cc79bc79c8c71fa0588d2a7a78b..da14c49284f41677f17d273badbbbd0560381ddb 100644 (file)
--- 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 a63029ef3eddc9e1bc19cbc552f327e6fdafa8aa..bd1892fe4b213c16cb705ebf7f3aee80242eebe2 100644 (file)
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -327,6 +327,24 @@ 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.