netdevsim: Introduce support for L3 offload xstats

Add support for testing of HW stats support that was added recently, namely
the L3 stats support. L3 stats are provided for devices for which the L3
stats have been turned on, and that were enabled for netdevsim through a
debugfs toggle:

    # echo $ifindex > /sys/kernel/debug/netdevsim/$DEV/hwstats/l3/enable_ifindex

For fully enabled netdevices, netdevsim counts 10pps of ingress traffic and
20pps of egress traffic. Similarly, L3 stats can be disabled for a given
device, and netdevsim ceases pretending there is any HW traffic going on:

    # echo $ifindex > /sys/kernel/debug/netdevsim/$DEV/hwstats/l3/disable_ifindex

Besides this, there is a third toggle to mark a device for future failure:

    # echo $ifindex > /sys/kernel/debug/netdevsim/$DEV/hwstats/l3/fail_next_enable

A future request to enable L3 stats on such netdevice will be bounced by
netdevsim:

    # ip -j l sh dev d | jq '.[].ifindex'
    66
    # echo 66 > /sys/kernel/debug/netdevsim/netdevsim10/hwstats/l3/enable_ifindex
    # echo 66 > /sys/kernel/debug/netdevsim/netdevsim10/hwstats/l3/fail_next_enable
    # ip stats set dev d l3_stats on
    Error: netdevsim: Stats enablement set to fail.
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/netdevsim/Makefile

@@ -3,7 +3,7 @@
 obj-$(CONFIG_NETDEVSIM) += netdevsim.o
 
 netdevsim-objs := \
-	netdev.o dev.o ethtool.o fib.o bus.o health.o udp_tunnels.o
+	netdev.o dev.o ethtool.o fib.o bus.o health.o hwstats.o udp_tunnels.o
 
 ifeq ($(CONFIG_BPF_SYSCALL),y)
 netdevsim-objs += \

drivers/net/netdevsim/dev.c

@@ -1498,10 +1498,14 @@ static int nsim_dev_reload_create(struct nsim_dev *nsim_dev,
 	if (err)
 		goto err_health_exit;
 
-	err = nsim_dev_port_add_all(nsim_dev, nsim_bus_dev->port_count);
+	err = nsim_dev_hwstats_init(nsim_dev);
 	if (err)
 		goto err_psample_exit;
 
+	err = nsim_dev_port_add_all(nsim_dev, nsim_bus_dev->port_count);
+	if (err)
+		goto err_hwstats_exit;
+
 	nsim_dev->take_snapshot = debugfs_create_file("take_snapshot",
 						      0200,
 						      nsim_dev->ddir,
@@ -1509,6 +1513,8 @@ static int nsim_dev_reload_create(struct nsim_dev *nsim_dev,
 						&nsim_dev_take_snapshot_fops);
 	return 0;
 
+err_hwstats_exit:
+	nsim_dev_hwstats_exit(nsim_dev);
 err_psample_exit:
 	nsim_dev_psample_exit(nsim_dev);
 err_health_exit:
@@ -1595,15 +1601,21 @@ int nsim_drv_probe(struct nsim_bus_dev *nsim_bus_dev)
 	if (err)
 		goto err_bpf_dev_exit;
 
-	err = nsim_dev_port_add_all(nsim_dev, nsim_bus_dev->port_count);
+	err = nsim_dev_hwstats_init(nsim_dev);
 	if (err)
 		goto err_psample_exit;
 
+	err = nsim_dev_port_add_all(nsim_dev, nsim_bus_dev->port_count);
+	if (err)
+		goto err_hwstats_exit;
+
 	nsim_dev->esw_mode = DEVLINK_ESWITCH_MODE_LEGACY;
 	devlink_set_features(devlink, DEVLINK_F_RELOAD);
 	devlink_register(devlink);
 	return 0;
 
+err_hwstats_exit:
+	nsim_dev_hwstats_exit(nsim_dev);
 err_psample_exit:
 	nsim_dev_psample_exit(nsim_dev);
 err_bpf_dev_exit:
@@ -1648,6 +1660,7 @@ static void nsim_dev_reload_destroy(struct nsim_dev *nsim_dev)
 	mutex_unlock(&nsim_dev->vfs_lock);
 
 	nsim_dev_port_del_all(nsim_dev);
+	nsim_dev_hwstats_exit(nsim_dev);
 	nsim_dev_psample_exit(nsim_dev);
 	nsim_dev_health_exit(nsim_dev);
 	nsim_fib_destroy(devlink, nsim_dev->fib_data);

drivers/net/netdevsim/netdevsim.h

@@ -184,6 +184,28 @@ struct nsim_dev_health {
 int nsim_dev_health_init(struct nsim_dev *nsim_dev, struct devlink *devlink);
 void nsim_dev_health_exit(struct nsim_dev *nsim_dev);
 
+struct nsim_dev_hwstats_netdev {
+	struct list_head list;
+	struct net_device *netdev;
+	struct rtnl_hw_stats64 stats;
+	bool enabled;
+	bool fail_enable;
+};
+
+struct nsim_dev_hwstats {
+	struct dentry *ddir;
+	struct dentry *l3_ddir;
+
+	struct mutex hwsdev_list_lock; /* protects hwsdev list(s) */
+	struct list_head l3_list;
+
+	struct notifier_block netdevice_nb;
+	struct delayed_work traffic_dw;
+};
+
+int nsim_dev_hwstats_init(struct nsim_dev *nsim_dev);
+void nsim_dev_hwstats_exit(struct nsim_dev *nsim_dev);
+
 #if IS_ENABLED(CONFIG_PSAMPLE)
 int nsim_dev_psample_init(struct nsim_dev *nsim_dev);
 void nsim_dev_psample_exit(struct nsim_dev *nsim_dev);
@@ -261,6 +283,7 @@ struct nsim_dev {
 	bool fail_reload;
 	struct devlink_region *dummy_region;
 	struct nsim_dev_health health;
+	struct nsim_dev_hwstats hwstats;
 	struct flow_action_cookie *fa_cookie;
 	spinlock_t fa_cookie_lock; /* protects fa_cookie */
 	bool fail_trap_group_set;