Date:   Tue, 10 Apr 2018 11:59:48 -0700
From:   Sridhar Samudrala <sridhar.samudrala@...el.com>
To:     mst@...hat.com, stephen@...workplumber.org, davem@...emloft.net,
        netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org, jesse.brandeburg@...el.com,
        alexander.h.duyck@...el.com, kubakici@...pl,
        sridhar.samudrala@...el.com, jasowang@...hat.com,
        loseweigh@...il.com, jiri@...nulli.us
Subject: [RFC PATCH net-next v6 2/4] net: Introduce generic bypass module

This provides a generic interface for paravirtual drivers to listen
for netdev register/unregister/link change events from pci ethernet
devices with the same MAC and takeover their datapath. The notifier and
event handling code is based on the existing netvsc implementation.

It exposes 2 sets of interfaces to the paravirtual drivers.
1. existing netvsc driver that uses 2 netdev model. In this model, no
master netdev is created. The paravirtual driver registers each bypass
instance along with a set of ops to manage the slave events.
     bypass_master_register()
     bypass_master_unregister()
2. new virtio_net based solution that uses 3 netdev model. In this model,
the bypass module provides interfaces to create/destroy additional master
netdev and all the slave events are managed internally.
      bypass_master_create()
      bypass_master_destroy()

Signed-off-by: Sridhar Samudrala <sridhar.samudrala@...el.com>
---
 include/linux/netdevice.h |  14 +
 include/net/bypass.h      |  96 ++++++
 net/Kconfig               |  18 +
 net/core/Makefile         |   1 +
 net/core/bypass.c         | 844 ++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 973 insertions(+)
 create mode 100644 include/net/bypass.h
 create mode 100644 net/core/bypass.c

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index cf44503ea81a..587293728f70 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1430,6 +1430,8 @@ enum netdev_priv_flags {
 	IFF_PHONY_HEADROOM		= 1<<24,
 	IFF_MACSEC			= 1<<25,
 	IFF_NO_RX_HANDLER		= 1<<26,
+	IFF_BYPASS			= 1 << 27,
+	IFF_BYPASS_SLAVE		= 1 << 28,
 };
 
 #define IFF_802_1Q_VLAN			IFF_802_1Q_VLAN
@@ -1458,6 +1460,8 @@ enum netdev_priv_flags {
 #define IFF_RXFH_CONFIGURED		IFF_RXFH_CONFIGURED
 #define IFF_MACSEC			IFF_MACSEC
 #define IFF_NO_RX_HANDLER		IFF_NO_RX_HANDLER
+#define IFF_BYPASS			IFF_BYPASS
+#define IFF_BYPASS_SLAVE		IFF_BYPASS_SLAVE
 
 /**
  *	struct net_device - The DEVICE structure.
@@ -4308,6 +4312,16 @@ static inline bool netif_is_rxfh_configured(const struct net_device *dev)
 	return dev->priv_flags & IFF_RXFH_CONFIGURED;
 }
 
+static inline bool netif_is_bypass_master(const struct net_device *dev)
+{
+	return dev->priv_flags & IFF_BYPASS;
+}
+
+static inline bool netif_is_bypass_slave(const struct net_device *dev)
+{
+	return dev->priv_flags & IFF_BYPASS_SLAVE;
+}
+
 /* This device needs to keep skb dst for qdisc enqueue or ndo_start_xmit() */
 static inline void netif_keep_dst(struct net_device *dev)
 {
diff --git a/include/net/bypass.h b/include/net/bypass.h
new file mode 100644
index 000000000000..86b02cb894cf
--- /dev/null
+++ b/include/net/bypass.h
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2018, Intel Corporation. */
+
+#ifndef _NET_BYPASS_H
+#define _NET_BYPASS_H
+
+#include <linux/netdevice.h>
+
+struct bypass_ops {
+	int (*slave_pre_register)(struct net_device *slave_netdev,
+				  struct net_device *bypass_netdev);
+	int (*slave_join)(struct net_device *slave_netdev,
+			  struct net_device *bypass_netdev);
+	int (*slave_pre_unregister)(struct net_device *slave_netdev,
+				    struct net_device *bypass_netdev);
+	int (*slave_release)(struct net_device *slave_netdev,
+			     struct net_device *bypass_netdev);
+	int (*slave_link_change)(struct net_device *slave_netdev,
+				 struct net_device *bypass_netdev);
+	rx_handler_result_t (*handle_frame)(struct sk_buff **pskb);
+};
+
+struct bypass_master {
+	struct list_head list;
+	struct net_device __rcu *bypass_netdev;
+	struct bypass_ops __rcu *ops;
+};
+
+/* bypass state */
+struct bypass_info {
+	/* passthru netdev with same MAC */
+	struct net_device __rcu *active_netdev;
+
+	/* virtio_net netdev */
+	struct net_device __rcu *backup_netdev;
+
+	/* active netdev stats */
+	struct rtnl_link_stats64 active_stats;
+
+	/* backup netdev stats */
+	struct rtnl_link_stats64 backup_stats;
+
+	/* aggregated stats */
+	struct rtnl_link_stats64 bypass_stats;
+
+	/* spinlock while updating stats */
+	spinlock_t stats_lock;
+};
+
+#if IS_ENABLED(CONFIG_NET_BYPASS)
+
+int bypass_master_create(struct net_device *backup_netdev,
+			 struct bypass_master **pbypass_master);
+void bypass_master_destroy(struct bypass_master *bypass_master);
+
+int bypass_master_register(struct net_device *dev, struct bypass_ops *ops,
+			   struct bypass_master **pbypass_master);
+void bypass_master_unregister(struct bypass_master *bypass_master);
+
+int bypass_slave_unregister(struct net_device *slave_netdev);
+
+#else
+
+static inline
+int bypass_master_create(struct net_device *backup_netdev,
+			 struct bypass_master **pbypass_master);
+{
+	return 0;
+}
+
+static inline
+void bypass_master_destroy(struct bypass_master *bypass_master)
+{
+}
+
+static inline
+int bypass_master_register(struct net_device *dev, struct bypass_ops *ops,
+			   struct pbypass_master **pbypass_master);
+{
+	return 0;
+}
+
+static inline
+void bypass_master_unregister(struct bypass_master *bypass_master)
+{
+}
+
+static inline
+int bypass_slave_unregister(struct net_device *slave_netdev)
+{
+	return 0;
+}
+
+#endif
+
+#endif /* _NET_BYPASS_H */
diff --git a/net/Kconfig b/net/Kconfig
index 0428f12c25c2..994445f4a96a 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -423,6 +423,24 @@ config MAY_USE_DEVLINK
 	  on MAY_USE_DEVLINK to ensure they do not cause link errors when
 	  devlink is a loadable module and the driver using it is built-in.
 
+config NET_BYPASS
+	tristate "Bypass interface"
+	---help---
+	  This provides a generic interface for paravirtual drivers to listen
+	  for netdev register/unregister/link change events from pci ethernet
+	  devices with the same MAC and takeover their datapath. This also
+	  enables live migration of a VM with direct attached VF by failing
+	  over to the paravirtual datapath when the VF is unplugged.
+
+config MAY_USE_BYPASS
+	tristate
+	default m if NET_BYPASS=m
+	default y if NET_BYPASS=y || NET_BYPASS=n
+	help
+	  Drivers using the bypass infrastructure should have a dependency
+	  on MAY_USE_BYPASS to ensure they do not cause link errors when
+	  bypass is a loadable module and the driver using it is built-in.
+
 endif   # if NET
 
 # Used by archs to tell that they support BPF JIT compiler plus which flavour.
diff --git a/net/core/Makefile b/net/core/Makefile
index 6dbbba8c57ae..a9727ed1c8fc 100644
--- a/net/core/Makefile
+++ b/net/core/Makefile
@@ -30,3 +30,4 @@ obj-$(CONFIG_DST_CACHE) += dst_cache.o
 obj-$(CONFIG_HWBM) += hwbm.o
 obj-$(CONFIG_NET_DEVLINK) += devlink.o
 obj-$(CONFIG_GRO_CELLS) += gro_cells.o
+obj-$(CONFIG_NET_BYPASS) += bypass.o
diff --git a/net/core/bypass.c b/net/core/bypass.c
new file mode 100644
index 000000000000..b5b9cb554c3f
--- /dev/null
+++ b/net/core/bypass.c
@@ -0,0 +1,844 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2018, Intel Corporation. */
+
+/* A common module to handle registrations and notifications for paravirtual
+ * drivers to enable accelerated datapath and support VF live migration.
+ *
+ * The notifier and event handling code is based on netvsc driver.
+ */
+
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/ethtool.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/netdevice.h>
+#include <linux/netpoll.h>
+#include <linux/rtnetlink.h>
+#include <linux/if_vlan.h>
+#include <linux/pci.h>
+#include <net/sch_generic.h>
+#include <uapi/linux/if_arp.h>
+#include <net/bypass.h>
+
+static LIST_HEAD(bypass_master_list);
+static DEFINE_SPINLOCK(bypass_lock);
+
+static int bypass_slave_pre_register(struct net_device *slave_netdev,
+				     struct net_device *bypass_netdev,
+				     struct bypass_ops *bypass_ops)
+{
+	struct bypass_info *bi;
+	bool backup;
+
+	if (bypass_ops) {
+		if (!bypass_ops->slave_pre_register)
+			return -EINVAL;
+
+		return bypass_ops->slave_pre_register(slave_netdev,
+						      bypass_netdev);
+	}
+
+	bi = netdev_priv(bypass_netdev);
+	backup = (slave_netdev->dev.parent == bypass_netdev->dev.parent);
+	if (backup ? rtnl_dereference(bi->backup_netdev) :
+			rtnl_dereference(bi->active_netdev)) {
+		netdev_err(bypass_netdev, "%s attempting to register as slave dev when %s already present\n",
+			   slave_netdev->name, backup ? "backup" : "active");
+		return -EEXIST;
+	}
+
+	/* Avoid non pci devices as active netdev */
+	if (!backup && (!slave_netdev->dev.parent ||
+			!dev_is_pci(slave_netdev->dev.parent)))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int bypass_slave_join(struct net_device *slave_netdev,
+			     struct net_device *bypass_netdev,
+			     struct bypass_ops *bypass_ops)
+{
+	struct bypass_info *bi;
+	bool backup;
+
+	if (bypass_ops) {
+		if (!bypass_ops->slave_join)
+			return -EINVAL;
+
+		return bypass_ops->slave_join(slave_netdev, bypass_netdev);
+	}
+
+	bi = netdev_priv(bypass_netdev);
+	backup = (slave_netdev->dev.parent == bypass_netdev->dev.parent);
+
+	dev_hold(slave_netdev);
+
+	if (backup) {
+		rcu_assign_pointer(bi->backup_netdev, slave_netdev);
+		dev_get_stats(bi->backup_netdev, &bi->backup_stats);
+	} else {
+		rcu_assign_pointer(bi->active_netdev, slave_netdev);
+		dev_get_stats(bi->active_netdev, &bi->active_stats);
+		bypass_netdev->min_mtu = slave_netdev->min_mtu;
+		bypass_netdev->max_mtu = slave_netdev->max_mtu;
+	}
+
+	netdev_info(bypass_netdev, "bypass slave:%s joined\n",
+		    slave_netdev->name);
+
+	return 0;
+}
+
+/* Called when slave dev is injecting data into network stack.
+ * Change the associated network device from lower dev to virtio.
+ * note: already called with rcu_read_lock
+ */
+static rx_handler_result_t bypass_handle_frame(struct sk_buff **pskb)
+{
+	struct sk_buff *skb = *pskb;
+	struct net_device *ndev = rcu_dereference(skb->dev->rx_handler_data);
+
+	skb->dev = ndev;
+
+	return RX_HANDLER_ANOTHER;
+}
+
+static struct net_device *bypass_master_get_bymac(u8 *mac,
+						  struct bypass_ops **ops)
+{
+	struct bypass_master *bypass_master;
+	struct net_device *bypass_netdev;
+
+	spin_lock(&bypass_lock);
+	list_for_each_entry(bypass_master, &bypass_master_list, list) {
+		bypass_netdev = rcu_dereference(bypass_master->bypass_netdev);
+		if (ether_addr_equal(bypass_netdev->perm_addr, mac)) {
+			*ops = rcu_dereference(bypass_master->ops);
+			spin_unlock(&bypass_lock);
+			return bypass_netdev;
+		}
+	}
+	spin_unlock(&bypass_lock);
+	return NULL;
+}
+
+static int bypass_slave_register(struct net_device *slave_netdev)
+{
+	struct net_device *bypass_netdev;
+	struct bypass_ops *bypass_ops;
+	int ret, orig_mtu;
+
+	ASSERT_RTNL();
+
+	bypass_netdev = bypass_master_get_bymac(slave_netdev->perm_addr,
+						&bypass_ops);
+	if (!bypass_netdev)
+		goto done;
+
+	ret = bypass_slave_pre_register(slave_netdev, bypass_netdev,
+					bypass_ops);
+	if (ret != 0)
+		goto done;
+
+	ret = netdev_rx_handler_register(slave_netdev,
+					 bypass_ops ? bypass_ops->handle_frame :
+					 bypass_handle_frame, bypass_netdev);
+	if (ret != 0) {
+		netdev_err(slave_netdev, "can not register bypass rx handler (err = %d)\n",
+			   ret);
+		goto done;
+	}
+
+	ret = netdev_upper_dev_link(slave_netdev, bypass_netdev, NULL);
+	if (ret != 0) {
+		netdev_err(slave_netdev, "can not set master device %s (err = %d)\n",
+			   bypass_netdev->name, ret);
+		goto upper_link_failed;
+	}
+
+	slave_netdev->priv_flags |= IFF_BYPASS_SLAVE;
+
+	if (netif_running(bypass_netdev)) {
+		ret = dev_open(slave_netdev);
+		if (ret && (ret != -EBUSY)) {
+			netdev_err(bypass_netdev, "Opening slave %s failed ret:%d\n",
+				   slave_netdev->name, ret);
+			goto err_interface_up;
+		}
+	}
+
+	/* Align MTU of slave with master */
+	orig_mtu = slave_netdev->mtu;
+	ret = dev_set_mtu(slave_netdev, bypass_netdev->mtu);
+	if (ret != 0) {
+		netdev_err(bypass_netdev, "unable to change mtu of %s to %u register failed\n",
+			   slave_netdev->name, bypass_netdev->mtu);
+		goto err_set_mtu;
+	}
+
+	ret = bypass_slave_join(slave_netdev, bypass_netdev, bypass_ops);
+	if (ret != 0)
+		goto err_join;
+
+	call_netdevice_notifiers(NETDEV_JOIN, slave_netdev);
+
+	netdev_info(bypass_netdev, "bypass slave:%s registered\n",
+		    slave_netdev->name);
+
+	goto done;
+
+err_join:
+	dev_set_mtu(slave_netdev, orig_mtu);
+err_set_mtu:
+	dev_close(slave_netdev);
+err_interface_up:
+	netdev_upper_dev_unlink(slave_netdev, bypass_netdev);
+	slave_netdev->priv_flags &= ~IFF_BYPASS_SLAVE;
+upper_link_failed:
+	netdev_rx_handler_unregister(slave_netdev);
+done:
+	return NOTIFY_DONE;
+}
+
+static int bypass_slave_pre_unregister(struct net_device *slave_netdev,
+				       struct net_device *bypass_netdev,
+				       struct bypass_ops *bypass_ops)
+{
+	struct net_device *backup_netdev, *active_netdev;
+	struct bypass_info *bi;
+
+	if (bypass_ops) {
+		if (!bypass_ops->slave_pre_unregister)
+			return -EINVAL;
+
+		return bypass_ops->slave_pre_unregister(slave_netdev,
+							bypass_netdev);
+	}
+
+	bi = netdev_priv(bypass_netdev);
+	active_netdev = rtnl_dereference(bi->active_netdev);
+	backup_netdev = rtnl_dereference(bi->backup_netdev);
+
+	if (slave_netdev != active_netdev && slave_netdev != backup_netdev)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int bypass_slave_release(struct net_device *slave_netdev,
+				struct net_device *bypass_netdev,
+				struct bypass_ops *bypass_ops)
+{
+	struct net_device *backup_netdev, *active_netdev;
+	struct bypass_info *bi;
+
+	if (bypass_ops) {
+		if (!bypass_ops->slave_release)
+			return -EINVAL;
+
+		return bypass_ops->slave_release(slave_netdev, bypass_netdev);
+	}
+
+	bi = netdev_priv(bypass_netdev);
+	active_netdev = rtnl_dereference(bi->active_netdev);
+	backup_netdev = rtnl_dereference(bi->backup_netdev);
+
+	if (slave_netdev == backup_netdev) {
+		RCU_INIT_POINTER(bi->backup_netdev, NULL);
+	} else {
+		RCU_INIT_POINTER(bi->active_netdev, NULL);
+		if (backup_netdev) {
+			bypass_netdev->min_mtu = backup_netdev->min_mtu;
+			bypass_netdev->max_mtu = backup_netdev->max_mtu;
+		}
+	}
+
+	dev_put(slave_netdev);
+
+	netdev_info(bypass_netdev, "bypass slave:%s released\n",
+		    slave_netdev->name);
+
+	return 0;
+}
+
+int bypass_slave_unregister(struct net_device *slave_netdev)
+{
+	struct net_device *bypass_netdev;
+	struct bypass_ops *bypass_ops;
+	int ret;
+
+	if (!netif_is_bypass_slave(slave_netdev))
+		goto done;
+
+	ASSERT_RTNL();
+
+	bypass_netdev = bypass_master_get_bymac(slave_netdev->perm_addr,
+						&bypass_ops);
+	if (!bypass_netdev)
+		goto done;
+
+	ret = bypass_slave_pre_unregister(slave_netdev, bypass_netdev,
+					  bypass_ops);
+	if (ret != 0)
+		goto done;
+
+	netdev_rx_handler_unregister(slave_netdev);
+	netdev_upper_dev_unlink(slave_netdev, bypass_netdev);
+	slave_netdev->priv_flags &= ~IFF_BYPASS_SLAVE;
+
+	bypass_slave_release(slave_netdev, bypass_netdev, bypass_ops);
+
+	netdev_info(bypass_netdev, "bypass slave:%s unregistered\n",
+		    slave_netdev->name);
+
+done:
+	return NOTIFY_DONE;
+}
+EXPORT_SYMBOL_GPL(bypass_slave_unregister);
+
+static bool bypass_xmit_ready(struct net_device *dev)
+{
+	return netif_running(dev) && netif_carrier_ok(dev);
+}
+
+static int bypass_slave_link_change(struct net_device *slave_netdev)
+{
+	struct net_device *bypass_netdev, *active_netdev, *backup_netdev;
+	struct bypass_ops *bypass_ops;
+	struct bypass_info *bi;
+
+	if (!netif_is_bypass_slave(slave_netdev))
+		goto done;
+
+	ASSERT_RTNL();
+
+	bypass_netdev = bypass_master_get_bymac(slave_netdev->perm_addr,
+						&bypass_ops);
+	if (!bypass_netdev)
+		goto done;
+
+	if (bypass_ops) {
+		if (!bypass_ops->slave_link_change)
+			goto done;
+
+		return bypass_ops->slave_link_change(slave_netdev,
+						     bypass_netdev);
+	}
+
+	if (!netif_running(bypass_netdev))
+		return 0;
+
+	bi = netdev_priv(bypass_netdev);
+
+	active_netdev = rtnl_dereference(bi->active_netdev);
+	backup_netdev = rtnl_dereference(bi->backup_netdev);
+
+	if (slave_netdev != active_netdev && slave_netdev != backup_netdev)
+		goto done;
+
+	if ((active_netdev && bypass_xmit_ready(active_netdev)) ||
+	    (backup_netdev && bypass_xmit_ready(backup_netdev))) {
+		netif_carrier_on(bypass_netdev);
+		netif_tx_wake_all_queues(bypass_netdev);
+	} else {
+		netif_carrier_off(bypass_netdev);
+		netif_tx_stop_all_queues(bypass_netdev);
+	}
+
+done:
+	return NOTIFY_DONE;
+}
+
+static bool bypass_validate_event_dev(struct net_device *dev)
+{
+	/* Skip parent events */
+	if (netif_is_bypass_master(dev))
+		return false;
+
+	/* Avoid non-Ethernet type devices */
+	if (dev->type != ARPHRD_ETHER)
+		return false;
+
+	/* Avoid Vlan dev with same MAC registering as VF */
+	if (is_vlan_dev(dev))
+		return false;
+
+	/* Avoid Bonding master dev with same MAC registering as slave dev */
+	if ((dev->priv_flags & IFF_BONDING) && (dev->flags & IFF_MASTER))
+		return false;
+
+	return true;
+}
+
+static int
+bypass_event(struct notifier_block *this, unsigned long event, void *ptr)
+{
+	struct net_device *event_dev = netdev_notifier_info_to_dev(ptr);
+
+	if (!bypass_validate_event_dev(event_dev))
+		return NOTIFY_DONE;
+
+	switch (event) {
+	case NETDEV_REGISTER:
+		return bypass_slave_register(event_dev);
+	case NETDEV_UNREGISTER:
+		return bypass_slave_unregister(event_dev);
+	case NETDEV_UP:
+	case NETDEV_DOWN:
+	case NETDEV_CHANGE:
+		return bypass_slave_link_change(event_dev);
+	default:
+		return NOTIFY_DONE;
+	}
+}
+
+static struct notifier_block bypass_notifier = {
+	.notifier_call = bypass_event,
+};
+
+int bypass_open(struct net_device *dev)
+{
+	struct bypass_info *bi = netdev_priv(dev);
+	struct net_device *active_netdev, *backup_netdev;
+	int err;
+
+	netif_carrier_off(dev);
+	netif_tx_wake_all_queues(dev);
+
+	active_netdev = rtnl_dereference(bi->active_netdev);
+	if (active_netdev) {
+		err = dev_open(active_netdev);
+		if (err)
+			goto err_active_open;
+	}
+
+	backup_netdev = rtnl_dereference(bi->backup_netdev);
+	if (backup_netdev) {
+		err = dev_open(backup_netdev);
+		if (err)
+			goto err_backup_open;
+	}
+
+	return 0;
+
+err_backup_open:
+	dev_close(active_netdev);
+err_active_open:
+	netif_tx_disable(dev);
+	return err;
+}
+EXPORT_SYMBOL_GPL(bypass_open);
+
+int bypass_close(struct net_device *dev)
+{
+	struct bypass_info *vi = netdev_priv(dev);
+	struct net_device *slave_netdev;
+
+	netif_tx_disable(dev);
+
+	slave_netdev = rtnl_dereference(vi->active_netdev);
+	if (slave_netdev)
+		dev_close(slave_netdev);
+
+	slave_netdev = rtnl_dereference(vi->backup_netdev);
+	if (slave_netdev)
+		dev_close(slave_netdev);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(bypass_close);
+
+static netdev_tx_t bypass_drop_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	atomic_long_inc(&dev->tx_dropped);
+	dev_kfree_skb_any(skb);
+	return NETDEV_TX_OK;
+}
+
+netdev_tx_t bypass_start_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct bypass_info *bi = netdev_priv(dev);
+	struct net_device *xmit_dev;
+
+	/* Try xmit via active netdev followed by backup netdev */
+	xmit_dev = rcu_dereference_bh(bi->active_netdev);
+	if (!xmit_dev || !bypass_xmit_ready(xmit_dev)) {
+		xmit_dev = rcu_dereference_bh(bi->backup_netdev);
+		if (!xmit_dev || !bypass_xmit_ready(xmit_dev))
+			return bypass_drop_xmit(skb, dev);
+	}
+
+	skb->dev = xmit_dev;
+	skb->queue_mapping = qdisc_skb_cb(skb)->slave_dev_queue_mapping;
+
+	return dev_queue_xmit(skb);
+}
+EXPORT_SYMBOL_GPL(bypass_start_xmit);
+
+u16 bypass_select_queue(struct net_device *dev, struct sk_buff *skb,
+			void *accel_priv, select_queue_fallback_t fallback)
+{
+	/* This helper function exists to help dev_pick_tx get the correct
+	 * destination queue.  Using a helper function skips a call to
+	 * skb_tx_hash and will put the skbs in the queue we expect on their
+	 * way down to the bonding driver.
+	 */
+	u16 txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) : 0;
+
+	/* Save the original txq to restore before passing to the driver */
+	qdisc_skb_cb(skb)->slave_dev_queue_mapping = skb->queue_mapping;
+
+	if (unlikely(txq >= dev->real_num_tx_queues)) {
+		do {
+			txq -= dev->real_num_tx_queues;
+		} while (txq >= dev->real_num_tx_queues);
+	}
+
+	return txq;
+}
+EXPORT_SYMBOL_GPL(bypass_select_queue);
+
+/* fold stats, assuming all rtnl_link_stats64 fields are u64, but
+ * that some drivers can provide 32bit values only.
+ */
+static void bypass_fold_stats(struct rtnl_link_stats64 *_res,
+			      const struct rtnl_link_stats64 *_new,
+			      const struct rtnl_link_stats64 *_old)
+{
+	const u64 *new = (const u64 *)_new;
+	const u64 *old = (const u64 *)_old;
+	u64 *res = (u64 *)_res;
+	int i;
+
+	for (i = 0; i < sizeof(*_res) / sizeof(u64); i++) {
+		u64 nv = new[i];
+		u64 ov = old[i];
+		s64 delta = nv - ov;
+
+		/* detects if this particular field is 32bit only */
+		if (((nv | ov) >> 32) == 0)
+			delta = (s64)(s32)((u32)nv - (u32)ov);
+
+		/* filter anomalies, some drivers reset their stats
+		 * at down/up events.
+		 */
+		if (delta > 0)
+			res[i] += delta;
+	}
+}
+
+void bypass_get_stats(struct net_device *dev, struct rtnl_link_stats64 *stats)
+{
+	struct bypass_info *bi = netdev_priv(dev);
+	const struct rtnl_link_stats64 *new;
+	struct rtnl_link_stats64 temp;
+	struct net_device *slave_netdev;
+
+	spin_lock(&bi->stats_lock);
+	memcpy(stats, &bi->bypass_stats, sizeof(*stats));
+
+	rcu_read_lock();
+
+	slave_netdev = rcu_dereference(bi->active_netdev);
+	if (slave_netdev) {
+		new = dev_get_stats(slave_netdev, &temp);
+		bypass_fold_stats(stats, new, &bi->active_stats);
+		memcpy(&bi->active_stats, new, sizeof(*new));
+	}
+
+	slave_netdev = rcu_dereference(bi->backup_netdev);
+	if (slave_netdev) {
+		new = dev_get_stats(slave_netdev, &temp);
+		bypass_fold_stats(stats, new, &bi->backup_stats);
+		memcpy(&bi->backup_stats, new, sizeof(*new));
+	}
+
+	rcu_read_unlock();
+
+	memcpy(&bi->bypass_stats, stats, sizeof(*stats));
+	spin_unlock(&bi->stats_lock);
+}
+EXPORT_SYMBOL_GPL(bypass_get_stats);
+
+int bypass_change_mtu(struct net_device *dev, int new_mtu)
+{
+	struct bypass_info *bi = netdev_priv(dev);
+	struct net_device *active_netdev, *backup_netdev;
+	int ret = 0;
+
+	active_netdev = rcu_dereference(bi->active_netdev);
+	if (active_netdev) {
+		ret = dev_set_mtu(active_netdev, new_mtu);
+		if (ret)
+			return ret;
+	}
+
+	backup_netdev = rcu_dereference(bi->backup_netdev);
+	if (backup_netdev) {
+		ret = dev_set_mtu(backup_netdev, new_mtu);
+		if (ret) {
+			dev_set_mtu(active_netdev, dev->mtu);
+			return ret;
+		}
+	}
+
+	dev->mtu = new_mtu;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(bypass_change_mtu);
+
+void bypass_set_rx_mode(struct net_device *dev)
+{
+	struct bypass_info *bi = netdev_priv(dev);
+	struct net_device *slave_netdev;
+
+	rcu_read_lock();
+
+	slave_netdev = rcu_dereference(bi->active_netdev);
+	if (slave_netdev) {
+		dev_uc_sync_multiple(slave_netdev, dev);
+		dev_mc_sync_multiple(slave_netdev, dev);
+	}
+
+	slave_netdev = rcu_dereference(bi->backup_netdev);
+	if (slave_netdev) {
+		dev_uc_sync_multiple(slave_netdev, dev);
+		dev_mc_sync_multiple(slave_netdev, dev);
+	}
+
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(bypass_set_rx_mode);
+
+static const struct net_device_ops bypass_netdev_ops = {
+	.ndo_open		= bypass_open,
+	.ndo_stop		= bypass_close,
+	.ndo_start_xmit		= bypass_start_xmit,
+	.ndo_select_queue	= bypass_select_queue,
+	.ndo_get_stats64	= bypass_get_stats,
+	.ndo_change_mtu		= bypass_change_mtu,
+	.ndo_set_rx_mode	= bypass_set_rx_mode,
+	.ndo_validate_addr	= eth_validate_addr,
+	.ndo_features_check	= passthru_features_check,
+};
+
+#define BYPASS_DRV_NAME "bypass"
+#define BYPASS_DRV_VERSION "0.1"
+
+static void bypass_ethtool_get_drvinfo(struct net_device *dev,
+				       struct ethtool_drvinfo *drvinfo)
+{
+	strlcpy(drvinfo->driver, BYPASS_DRV_NAME, sizeof(drvinfo->driver));
+	strlcpy(drvinfo->version, BYPASS_DRV_VERSION, sizeof(drvinfo->version));
+}
+
+int bypass_ethtool_get_link_ksettings(struct net_device *dev,
+				      struct ethtool_link_ksettings *cmd)
+{
+	struct bypass_info *bi = netdev_priv(dev);
+	struct net_device *slave_netdev;
+
+	slave_netdev = rtnl_dereference(bi->active_netdev);
+	if (!slave_netdev || !bypass_xmit_ready(slave_netdev)) {
+		slave_netdev = rtnl_dereference(bi->backup_netdev);
+		if (!slave_netdev || !bypass_xmit_ready(slave_netdev)) {
+			cmd->base.duplex = DUPLEX_UNKNOWN;
+			cmd->base.port = PORT_OTHER;
+			cmd->base.speed = SPEED_UNKNOWN;
+
+			return 0;
+		}
+	}
+
+	return __ethtool_get_link_ksettings(slave_netdev, cmd);
+}
+EXPORT_SYMBOL_GPL(bypass_ethtool_get_link_ksettings);
+
+static const struct ethtool_ops bypass_ethtool_ops = {
+	.get_drvinfo            = bypass_ethtool_get_drvinfo,
+	.get_link               = ethtool_op_get_link,
+	.get_link_ksettings     = bypass_ethtool_get_link_ksettings,
+};
+
+static void bypass_register_existing_slave(struct net_device *bypass_netdev)
+{
+	struct net *net = dev_net(bypass_netdev);
+	struct net_device *dev;
+
+	rtnl_lock();
+	for_each_netdev(net, dev) {
+		if (dev == bypass_netdev)
+			continue;
+		if (!bypass_validate_event_dev(dev))
+			continue;
+		if (ether_addr_equal(bypass_netdev->perm_addr, dev->perm_addr))
+			bypass_slave_register(dev);
+	}
+	rtnl_unlock();
+}
+
+int bypass_master_register(struct net_device *dev, struct bypass_ops *ops,
+			   struct bypass_master **pbypass_master)
+{
+	struct bypass_master *bypass_master;
+
+	bypass_master = kzalloc(sizeof(*bypass_master), GFP_KERNEL);
+	if (!bypass_master)
+		return -ENOMEM;
+
+	rcu_assign_pointer(bypass_master->ops, ops);
+	dev_hold(dev);
+	dev->priv_flags |= IFF_BYPASS;
+	rcu_assign_pointer(bypass_master->bypass_netdev, dev);
+
+	spin_lock(&bypass_lock);
+	list_add_tail(&bypass_master->list, &bypass_master_list);
+	spin_unlock(&bypass_lock);
+
+	bypass_register_existing_slave(dev);
+
+	*pbypass_master = bypass_master;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(bypass_master_register);
+
+void bypass_master_unregister(struct bypass_master *bypass_master)
+{
+	struct net_device *bypass_netdev;
+
+	bypass_netdev = rcu_dereference(bypass_master->bypass_netdev);
+
+	bypass_netdev->priv_flags &= ~IFF_BYPASS;
+	dev_put(bypass_netdev);
+
+	spin_lock(&bypass_lock);
+	list_del(&bypass_master->list);
+	spin_unlock(&bypass_lock);
+
+	kfree(bypass_master);
+}
+EXPORT_SYMBOL_GPL(bypass_master_unregister);
+
+int bypass_master_create(struct net_device *backup_netdev,
+			 struct bypass_master **pbypass_master)
+{
+	struct device *dev = backup_netdev->dev.parent;
+	struct net_device *bypass_netdev;
+	int err;
+
+	/* Alloc at least 2 queues, for now we are going with 16 assuming
+	 * that most devices being bonded won't have too many queues.
+	 */
+	bypass_netdev = alloc_etherdev_mq(sizeof(struct bypass_info), 16);
+	if (!bypass_netdev) {
+		dev_err(dev, "Unable to allocate bypass_netdev!\n");
+		return -ENOMEM;
+	}
+
+	dev_net_set(bypass_netdev, dev_net(backup_netdev));
+	SET_NETDEV_DEV(bypass_netdev, dev);
+
+	bypass_netdev->netdev_ops = &bypass_netdev_ops;
+	bypass_netdev->ethtool_ops = &bypass_ethtool_ops;
+
+	/* Initialize the device options */
+	bypass_netdev->priv_flags |= IFF_UNICAST_FLT | IFF_NO_QUEUE;
+	bypass_netdev->priv_flags &= ~(IFF_XMIT_DST_RELEASE |
+				       IFF_TX_SKB_SHARING);
+
+	/* don't acquire bypass netdev's netif_tx_lock when transmitting */
+	bypass_netdev->features |= NETIF_F_LLTX;
+
+	/* Don't allow bypass devices to change network namespaces. */
+	bypass_netdev->features |= NETIF_F_NETNS_LOCAL;
+
+	bypass_netdev->hw_features = NETIF_F_HW_CSUM | NETIF_F_SG |
+				     NETIF_F_FRAGLIST | NETIF_F_ALL_TSO |
+				     NETIF_F_HIGHDMA | NETIF_F_LRO;
+
+	bypass_netdev->hw_features |= NETIF_F_GSO_ENCAP_ALL;
+	bypass_netdev->features |= bypass_netdev->hw_features;
+
+	memcpy(bypass_netdev->dev_addr, backup_netdev->dev_addr,
+	       bypass_netdev->addr_len);
+
+	bypass_netdev->min_mtu = backup_netdev->min_mtu;
+	bypass_netdev->max_mtu = backup_netdev->max_mtu;
+
+	err = register_netdev(bypass_netdev);
+	if (err < 0) {
+		dev_err(dev, "Unable to register bypass_netdev!\n");
+		goto err_register_netdev;
+	}
+
+	netif_carrier_off(bypass_netdev);
+
+	err = bypass_master_register(bypass_netdev, NULL, pbypass_master);
+	if (err < 0)
+		goto err_bypass;
+
+	return 0;
+
+err_bypass:
+	unregister_netdev(bypass_netdev);
+err_register_netdev:
+	free_netdev(bypass_netdev);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(bypass_master_create);
+
+void bypass_master_destroy(struct bypass_master *bypass_master)
+{
+	struct net_device *bypass_netdev;
+	struct net_device *slave_netdev;
+	struct bypass_info *bi;
+
+	if (!bypass_master)
+		return;
+
+	bypass_netdev = rcu_dereference(bypass_master->bypass_netdev);
+	bi = netdev_priv(bypass_netdev);
+
+	netif_device_detach(bypass_netdev);
+
+	rtnl_lock();
+
+	slave_netdev = rtnl_dereference(bi->active_netdev);
+	if (slave_netdev)
+		bypass_slave_unregister(slave_netdev);
+
+	slave_netdev = rtnl_dereference(bi->backup_netdev);
+	if (slave_netdev)
+		bypass_slave_unregister(slave_netdev);
+
+	bypass_master_unregister(bypass_master);
+
+	unregister_netdevice(bypass_netdev);
+
+	rtnl_unlock();
+
+	free_netdev(bypass_netdev);
+}
+EXPORT_SYMBOL_GPL(bypass_master_destroy);
+
+static __init int
+bypass_init(void)
+{
+	register_netdevice_notifier(&bypass_notifier);
+
+	return 0;
+}
+module_init(bypass_init);
+
+static __exit
+void bypass_exit(void)
+{
+	unregister_netdevice_notifier(&bypass_notifier);
+}
+module_exit(bypass_exit);
+
+MODULE_DESCRIPTION("Bypass infrastructure/interface for Paravirtual drivers");
+MODULE_LICENSE("GPL v2");
-- 
2.14.3

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