arp_notify: allow drivers to explicitly request a notification event.

commit 06c4648d46d1b757d6b9591a86810be79818b60c upstream.

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
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index fa8b47637997cd4eef3f0e791ce8bf5b48b34a85..473799698bc8a919407cc51af2f84930fae6ff44 100644 (file)
--- 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 fee6c2f68075c90fe77cea11138d627bd9efa4f5..45477f24f1daef6acb98a6327fb194e9c2f30460 100644 (file)
--- 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 90e3d6379a42ae369ceeba06c783978858e96e71..c12777fc0990ea98929df215a18b883900270c01 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 ff4dd53eeff013f875330d8fbeb24e3a6e299e5a..2d7ca9e8a404019256adcfaeaddf3d49d90c3f11 100644 (file)
--- 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.