net: Introduce net_failover driver

The net_failover driver provides an automated failover mechanism via APIs
to create and destroy a failover master netdev and manages a primary and
standby slave netdevs that get registered via the generic failover
infrastructure.

The failover netdev acts a master device and controls 2 slave devices. The
original paravirtual interface gets registered as 'standby' slave netdev and
a passthru/vf device with the same MAC gets registered as 'primary' slave
netdev. Both 'standby' and 'failover' netdevs are associated with the same
'pci' device. The user accesses the network interface via 'failover' netdev.
The 'failover' netdev chooses 'primary' netdev as default for transmits when
it is available with link up and running.

This can be used by paravirtual drivers to enable an alternate low latency
datapath. It also enables hypervisor controlled live migration of a VM with
direct attached VF by failing over to the paravirtual datapath when the VF
is unplugged.
Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/net_failover.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+============
+NET_FAILOVER
+============
+
+Overview
+========
+
+The net_failover driver provides an automated failover mechanism via APIs
+to create and destroy a failover master netdev and mananges a primary and
+standby slave netdevs that get registered via the generic failover
+infrastructrure.
+
+The failover netdev acts a master device and controls 2 slave devices. The
+original paravirtual interface is registered as 'standby' slave netdev and
+a passthru/vf device with the same MAC gets registered as 'primary' slave
+netdev. Both 'standby' and 'failover' netdevs are associated with the same
+'pci' device. The user accesses the network interface via 'failover' netdev.
+The 'failover' netdev chooses 'primary' netdev as default for transmits when
+it is available with link up and running.
+
+This can be used by paravirtual drivers to enable an alternate low latency
+datapath. It also enables hypervisor controlled live migration of a VM with
+direct attached VF by failing over to the paravirtual datapath when the VF
+is unplugged.

MAINTAINERS

@@ -9654,6 +9654,14 @@ S:	Maintained
 F:	Documentation/hwmon/nct6775
 F:	drivers/hwmon/nct6775.c
 
+NET_FAILOVER MODULE
+M:	Sridhar Samudrala <sridhar.samudrala@intel.com>
+L:	netdev@vger.kernel.org
+S:	Supported
+F:	driver/net/net_failover.c
+F:	include/net/net_failover.h
+F:	Documentation/networking/net_failover.rst
+
 NETEFFECT IWARP RNIC DRIVER (IW_NES)
 M:	Faisal Latif <faisal.latif@intel.com>
 L:	linux-rdma@vger.kernel.org

drivers/net/Kconfig

@@ -510,4 +510,16 @@ config NETDEVSIM
 	  To compile this driver as a module, choose M here: the module
 	  will be called netdevsim.
 
+config NET_FAILOVER
+	tristate "Failover driver"
+	select FAILOVER
+	help
+	  This provides an automated failover mechanism via APIs to create
+	  and destroy a failover master netdev and manages a primary and
+	  standby slave netdevs that get registered via the generic failover
+	  infrastructure. This can be used by paravirtual drivers to enable
+	  an alternate low latency datapath. It alsoenables live migration of
+	  a VM with direct attached VF by failing over to the paravirtual
+	  datapath when the VF is unplugged.
+
 endif # NETDEVICES

drivers/net/Makefile

@@ -78,3 +78,4 @@ obj-$(CONFIG_FUJITSU_ES) += fjes/
 thunderbolt-net-y += thunderbolt.o
 obj-$(CONFIG_THUNDERBOLT_NET) += thunderbolt-net.o
 obj-$(CONFIG_NETDEVSIM) += netdevsim/
+obj-$(CONFIG_NET_FAILOVER) += net_failover.o

include/net/net_failover.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (c) 2018, Intel Corporation. */
+
+#ifndef _NET_FAILOVER_H
+#define _NET_FAILOVER_H
+
+#include <net/failover.h>
+
+/* failover state */
+struct net_failover_info {
+	/* primary netdev with same MAC */
+	struct net_device __rcu *primary_dev;
+
+	/* standby netdev */
+	struct net_device __rcu *standby_dev;
+
+	/* primary netdev stats */
+	struct rtnl_link_stats64 primary_stats;
+
+	/* standby netdev stats */
+	struct rtnl_link_stats64 standby_stats;
+
+	/* aggregated stats */
+	struct rtnl_link_stats64 failover_stats;
+
+	/* spinlock while updating stats */
+	spinlock_t stats_lock;
+};
+
+struct failover *net_failover_create(struct net_device *standby_dev);
+void net_failover_destroy(struct failover *failover);
+
+#define FAILOVER_VLAN_FEATURES	(NETIF_F_HW_CSUM | NETIF_F_SG | \
+				 NETIF_F_FRAGLIST | NETIF_F_ALL_TSO | \
+				 NETIF_F_HIGHDMA | NETIF_F_LRO)
+
+#define FAILOVER_ENC_FEATURES	(NETIF_F_HW_CSUM | NETIF_F_SG | \
+				 NETIF_F_RXCSUM | NETIF_F_ALL_TSO)
+
+#endif /* _NET_FAILOVER_H */