drivers/net/veth.c - kernel/msm-4.19 - Gitiles

 /*
  *  drivers/net/veth.c
  *
  *  Copyright (C) 2007 OpenVZ http://openvz.org, SWsoft Inc
  *
  * Author: Pavel Emelianov <xemul@openvz.org>
  * Ethtool interface from: Eric W. Biederman <ebiederm@xmission.com>
  *
  */

 #include <linux/netdevice.h>
 #include <linux/slab.h>
 #include <linux/ethtool.h>
 #include <linux/etherdevice.h>
 #include <linux/u64_stats_sync.h>

 #include <net/rtnetlink.h>
 #include <net/dst.h>
 #include <net/xfrm.h>
 #include <linux/veth.h>
 #include <linux/module.h>

 #define DRV_NAME	"veth"
 #define DRV_VERSION	"1.0"

 struct pcpu_vstats {
 	u64			packets;
 	u64			bytes;
 	struct u64_stats_sync	syncp;
 };

 struct veth_priv {
 	struct net_device __rcu	*peer;
 	atomic64_t		dropped;
 	unsigned		requested_headroom;
 };

 /*
  * ethtool interface
  */

 static struct {
 	const char string[ETH_GSTRING_LEN];
 } ethtool_stats_keys[] = {
 	{ "peer_ifindex" },
 };

 static int veth_get_link_ksettings(struct net_device *dev,
 				   struct ethtool_link_ksettings *cmd)
 {
 	cmd->base.speed		= SPEED_10000;
 	cmd->base.duplex	= DUPLEX_FULL;
 	cmd->base.port		= PORT_TP;
 	cmd->base.autoneg	= AUTONEG_DISABLE;
 	return 0;
 }

 static void veth_get_drvinfo(struct net_device *dev, struct ethtool_drvinfo *info)
 {
 	strlcpy(info->driver, DRV_NAME, sizeof(info->driver));
 	strlcpy(info->version, DRV_VERSION, sizeof(info->version));
 }

 static void veth_get_strings(struct net_device *dev, u32 stringset, u8 *buf)
 {
 	switch(stringset) {
 	case ETH_SS_STATS:
 		memcpy(buf, &ethtool_stats_keys, sizeof(ethtool_stats_keys));
 		break;
 	}
 }

 static int veth_get_sset_count(struct net_device *dev, int sset)
 {
 	switch (sset) {
 	case ETH_SS_STATS:
 		return ARRAY_SIZE(ethtool_stats_keys);
 	default:
 		return -EOPNOTSUPP;
 	}
 }

 static void veth_get_ethtool_stats(struct net_device *dev,
 		struct ethtool_stats *stats, u64 *data)
 {
 	struct veth_priv *priv = netdev_priv(dev);
 	struct net_device *peer = rtnl_dereference(priv->peer);

 	data[0] = peer ? peer->ifindex : 0;
 }

 static const struct ethtool_ops veth_ethtool_ops = {
 	.get_drvinfo		= veth_get_drvinfo,
 	.get_link		= ethtool_op_get_link,
 	.get_strings		= veth_get_strings,
 	.get_sset_count		= veth_get_sset_count,
 	.get_ethtool_stats	= veth_get_ethtool_stats,
 	.get_link_ksettings	= veth_get_link_ksettings,
 };

 static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct veth_priv *priv = netdev_priv(dev);
 	struct net_device *rcv;
 	int length = skb->len;

 	rcu_read_lock();
 	rcv = rcu_dereference(priv->peer);
 	if (unlikely(!rcv)) {
 		kfree_skb(skb);
 		goto drop;
 	}

 	if (likely(dev_forward_skb(rcv, skb) == NET_RX_SUCCESS)) {
 		struct pcpu_vstats *stats = this_cpu_ptr(dev->vstats);

 		u64_stats_update_begin(&stats->syncp);
 		stats->bytes += length;
 		stats->packets++;
 		u64_stats_update_end(&stats->syncp);
 	} else {
 drop:
 		atomic64_inc(&priv->dropped);
 	}
 	rcu_read_unlock();
 	return NETDEV_TX_OK;
 }

 /*
  * general routines
  */

 static u64 veth_stats_one(struct pcpu_vstats *result, struct net_device *dev)
 {
 	struct veth_priv *priv = netdev_priv(dev);
 	int cpu;

 	result->packets = 0;
 	result->bytes = 0;
 	for_each_possible_cpu(cpu) {
 		struct pcpu_vstats *stats = per_cpu_ptr(dev->vstats, cpu);
 		u64 packets, bytes;
 		unsigned int start;

 		do {
 			start = u64_stats_fetch_begin_irq(&stats->syncp);
 			packets = stats->packets;
 			bytes = stats->bytes;
 		} while (u64_stats_fetch_retry_irq(&stats->syncp, start));
 		result->packets += packets;
 		result->bytes += bytes;
 	}
 	return atomic64_read(&priv->dropped);
 }

 static void veth_get_stats64(struct net_device *dev,
 			     struct rtnl_link_stats64 *tot)
 {
 	struct veth_priv *priv = netdev_priv(dev);
 	struct net_device *peer;
 	struct pcpu_vstats one;

 	tot->tx_dropped = veth_stats_one(&one, dev);
 	tot->tx_bytes = one.bytes;
 	tot->tx_packets = one.packets;

 	rcu_read_lock();
 	peer = rcu_dereference(priv->peer);
 	if (peer) {
 		tot->rx_dropped = veth_stats_one(&one, peer);
 		tot->rx_bytes = one.bytes;
 		tot->rx_packets = one.packets;
 	}
 	rcu_read_unlock();
 }

 /* fake multicast ability */
 static void veth_set_multicast_list(struct net_device *dev)
 {
 }

 static int veth_open(struct net_device *dev)
 {
 	struct veth_priv *priv = netdev_priv(dev);
 	struct net_device *peer = rtnl_dereference(priv->peer);

 	if (!peer)
 		return -ENOTCONN;

 	if (peer->flags & IFF_UP) {
 		netif_carrier_on(dev);
 		netif_carrier_on(peer);
 	}
 	return 0;
 }

 static int veth_close(struct net_device *dev)
 {
 	struct veth_priv *priv = netdev_priv(dev);
 	struct net_device *peer = rtnl_dereference(priv->peer);

 	netif_carrier_off(dev);
 	if (peer)
 		netif_carrier_off(peer);

 	return 0;
 }

 static int is_valid_veth_mtu(int mtu)
 {
 	return mtu >= ETH_MIN_MTU && mtu <= ETH_MAX_MTU;
 }

 static int veth_dev_init(struct net_device *dev)
 {
 	dev->vstats = netdev_alloc_pcpu_stats(struct pcpu_vstats);
 	if (!dev->vstats)
 		return -ENOMEM;
 	return 0;
 }

 static void veth_dev_free(struct net_device *dev)
 {
 	free_percpu(dev->vstats);
 }

 #ifdef CONFIG_NET_POLL_CONTROLLER
 static void veth_poll_controller(struct net_device *dev)
 {
 	/* veth only receives frames when its peer sends one
 	 * Since it's a synchronous operation, we are guaranteed
 	 * never to have pending data when we poll for it so
 	 * there is nothing to do here.
 	 *
 	 * We need this though so netpoll recognizes us as an interface that
 	 * supports polling, which enables bridge devices in virt setups to
 	 * still use netconsole
 	 */
 }
 #endif	/* CONFIG_NET_POLL_CONTROLLER */

 static int veth_get_iflink(const struct net_device *dev)
 {
 	struct veth_priv *priv = netdev_priv(dev);
 	struct net_device *peer;
 	int iflink;

 	rcu_read_lock();
 	peer = rcu_dereference(priv->peer);
 	iflink = peer ? peer->ifindex : 0;
 	rcu_read_unlock();

 	return iflink;
 }

 static void veth_set_rx_headroom(struct net_device *dev, int new_hr)
 {
 	struct veth_priv *peer_priv, *priv = netdev_priv(dev);
 	struct net_device *peer;

 	if (new_hr < 0)
 		new_hr = 0;

 	rcu_read_lock();
 	peer = rcu_dereference(priv->peer);
 	if (unlikely(!peer))
 		goto out;

 	peer_priv = netdev_priv(peer);
 	priv->requested_headroom = new_hr;
 	new_hr = max(priv->requested_headroom, peer_priv->requested_headroom);
 	dev->needed_headroom = new_hr;
 	peer->needed_headroom = new_hr;

 out:
 	rcu_read_unlock();
 }

 static const struct net_device_ops veth_netdev_ops = {
 	.ndo_init            = veth_dev_init,
 	.ndo_open            = veth_open,
 	.ndo_stop            = veth_close,
 	.ndo_start_xmit      = veth_xmit,
 	.ndo_get_stats64     = veth_get_stats64,
 	.ndo_set_rx_mode     = veth_set_multicast_list,
 	.ndo_set_mac_address = eth_mac_addr,
 #ifdef CONFIG_NET_POLL_CONTROLLER
 	.ndo_poll_controller	= veth_poll_controller,
 #endif
 	.ndo_get_iflink		= veth_get_iflink,
 	.ndo_features_check	= passthru_features_check,
 	.ndo_set_rx_headroom	= veth_set_rx_headroom,
 };

 #define VETH_FEATURES (NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HW_CSUM | \
 		       NETIF_F_RXCSUM | NETIF_F_SCTP_CRC | NETIF_F_HIGHDMA | \
 		       NETIF_F_GSO_SOFTWARE | NETIF_F_GSO_ENCAP_ALL | \
 		       NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_HW_VLAN_CTAG_RX | \
 		       NETIF_F_HW_VLAN_STAG_TX | NETIF_F_HW_VLAN_STAG_RX )

 static void veth_setup(struct net_device *dev)
 {
 	ether_setup(dev);

 	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
 	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
 	dev->priv_flags |= IFF_NO_QUEUE;
 	dev->priv_flags |= IFF_PHONY_HEADROOM;

 	dev->netdev_ops = &veth_netdev_ops;
 	dev->ethtool_ops = &veth_ethtool_ops;
 	dev->features |= NETIF_F_LLTX;
 	dev->features |= VETH_FEATURES;
 	dev->vlan_features = dev->features &
 			     ~(NETIF_F_HW_VLAN_CTAG_TX |
 			       NETIF_F_HW_VLAN_STAG_TX |
 			       NETIF_F_HW_VLAN_CTAG_RX |
 			       NETIF_F_HW_VLAN_STAG_RX);
 	dev->needs_free_netdev = true;
 	dev->priv_destructor = veth_dev_free;
 	dev->max_mtu = ETH_MAX_MTU;

 	dev->hw_features = VETH_FEATURES;
 	dev->hw_enc_features = VETH_FEATURES;
 	dev->mpls_features = NETIF_F_HW_CSUM | NETIF_F_GSO_SOFTWARE;
 }

 /*
  * netlink interface
  */

 static int veth_validate(struct nlattr *tb[], struct nlattr *data[],
 			 struct netlink_ext_ack *extack)
 {
 	if (tb[IFLA_ADDRESS]) {
 		if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
 			return -EINVAL;
 		if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
 			return -EADDRNOTAVAIL;
 	}
 	if (tb[IFLA_MTU]) {
 		if (!is_valid_veth_mtu(nla_get_u32(tb[IFLA_MTU])))
 			return -EINVAL;
 	}
 	return 0;
 }

 static struct rtnl_link_ops veth_link_ops;

 static int veth_newlink(struct net *src_net, struct net_device *dev,
 			struct nlattr *tb[], struct nlattr *data[],
 			struct netlink_ext_ack *extack)
 {
 	int err;
 	struct net_device *peer;
 	struct veth_priv *priv;
 	char ifname[IFNAMSIZ];
 	struct nlattr *peer_tb[IFLA_MAX + 1], **tbp;
 	unsigned char name_assign_type;
 	struct ifinfomsg *ifmp;
 	struct net *net;

 	/*
 	 * create and register peer first
 	 */
 	if (data != NULL && data[VETH_INFO_PEER] != NULL) {
 		struct nlattr *nla_peer;

 		nla_peer = data[VETH_INFO_PEER];
 		ifmp = nla_data(nla_peer);
 		err = rtnl_nla_parse_ifla(peer_tb,
 					  nla_data(nla_peer) + sizeof(struct ifinfomsg),
 					  nla_len(nla_peer) - sizeof(struct ifinfomsg),
 					  NULL);
 		if (err < 0)
 			return err;

 		err = veth_validate(peer_tb, NULL, extack);
 		if (err < 0)
 			return err;

 		tbp = peer_tb;
 	} else {
 		ifmp = NULL;
 		tbp = tb;
 	}

 	if (tbp[IFLA_IFNAME]) {
 		nla_strlcpy(ifname, tbp[IFLA_IFNAME], IFNAMSIZ);
 		name_assign_type = NET_NAME_USER;
 	} else {
 		snprintf(ifname, IFNAMSIZ, DRV_NAME "%%d");
 		name_assign_type = NET_NAME_ENUM;
 	}

 	net = rtnl_link_get_net(src_net, tbp);
 	if (IS_ERR(net))
 		return PTR_ERR(net);

 	peer = rtnl_create_link(net, ifname, name_assign_type,
 				&veth_link_ops, tbp);
 	if (IS_ERR(peer)) {
 		put_net(net);
 		return PTR_ERR(peer);
 	}

 	if (tbp[IFLA_ADDRESS] == NULL)
 		eth_hw_addr_random(peer);

 	if (ifmp && (dev->ifindex != 0))
 		peer->ifindex = ifmp->ifi_index;

 	err = register_netdevice(peer);
 	put_net(net);
 	net = NULL;
 	if (err < 0)
 		goto err_register_peer;

 	netif_carrier_off(peer);

 	err = rtnl_configure_link(peer, ifmp);
 	if (err < 0)
 		goto err_configure_peer;

 	/*
 	 * register dev last
 	 *
 	 * note, that since we've registered new device the dev's name
 	 * should be re-allocated
 	 */

 	if (tb[IFLA_ADDRESS] == NULL)
 		eth_hw_addr_random(dev);

 	if (tb[IFLA_IFNAME])
 		nla_strlcpy(dev->name, tb[IFLA_IFNAME], IFNAMSIZ);
 	else
 		snprintf(dev->name, IFNAMSIZ, DRV_NAME "%%d");

 	err = register_netdevice(dev);
 	if (err < 0)
 		goto err_register_dev;

 	netif_carrier_off(dev);

 	/*
 	 * tie the deviced together
 	 */

 	priv = netdev_priv(dev);
 	rcu_assign_pointer(priv->peer, peer);

 	priv = netdev_priv(peer);
 	rcu_assign_pointer(priv->peer, dev);
 	return 0;

 err_register_dev:
 	/* nothing to do */
 err_configure_peer:
 	unregister_netdevice(peer);
 	return err;

 err_register_peer:
 	free_netdev(peer);
 	return err;
 }

 static void veth_dellink(struct net_device *dev, struct list_head *head)
 {
 	struct veth_priv *priv;
 	struct net_device *peer;

 	priv = netdev_priv(dev);
 	peer = rtnl_dereference(priv->peer);

 	/* Note : dellink() is called from default_device_exit_batch(),
 	 * before a rcu_synchronize() point. The devices are guaranteed
 	 * not being freed before one RCU grace period.
 	 */
 	RCU_INIT_POINTER(priv->peer, NULL);
 	unregister_netdevice_queue(dev, head);

 	if (peer) {
 		priv = netdev_priv(peer);
 		RCU_INIT_POINTER(priv->peer, NULL);
 		unregister_netdevice_queue(peer, head);
 	}
 }

 static const struct nla_policy veth_policy[VETH_INFO_MAX + 1] = {
 	[VETH_INFO_PEER]	= { .len = sizeof(struct ifinfomsg) },
 };

 static struct net *veth_get_link_net(const struct net_device *dev)
 {
 	struct veth_priv *priv = netdev_priv(dev);
 	struct net_device *peer = rtnl_dereference(priv->peer);

 	return peer ? dev_net(peer) : dev_net(dev);
 }

 static struct rtnl_link_ops veth_link_ops = {
 	.kind		= DRV_NAME,
 	.priv_size	= sizeof(struct veth_priv),
 	.setup		= veth_setup,
 	.validate	= veth_validate,
 	.newlink	= veth_newlink,
 	.dellink	= veth_dellink,
 	.policy		= veth_policy,
 	.maxtype	= VETH_INFO_MAX,
 	.get_link_net	= veth_get_link_net,
 };

 /*
  * init/fini
  */

 static __init int veth_init(void)
 {
 	return rtnl_link_register(&veth_link_ops);
 }

 static __exit void veth_exit(void)
 {
 	rtnl_link_unregister(&veth_link_ops);
 }

 module_init(veth_init);
 module_exit(veth_exit);

 MODULE_DESCRIPTION("Virtual Ethernet Tunnel");
 MODULE_LICENSE("GPL v2");
 MODULE_ALIAS_RTNL_LINK(DRV_NAME);
	/*
	* drivers/net/veth.c
	*
	* Copyright (C) 2007 OpenVZ http://openvz.org, SWsoft Inc
	*
	* Author: Pavel Emelianov <xemul@openvz.org>
	* Ethtool interface from: Eric W. Biederman <ebiederm@xmission.com>
	*
	*/

	#include <linux/netdevice.h>
	#include <linux/slab.h>
	#include <linux/ethtool.h>
	#include <linux/etherdevice.h>
	#include <linux/u64_stats_sync.h>

	#include <net/rtnetlink.h>
	#include <net/dst.h>
	#include <net/xfrm.h>
	#include <linux/veth.h>
	#include <linux/module.h>

	#define DRV_NAME "veth"
	#define DRV_VERSION "1.0"

	struct pcpu_vstats {
	u64 packets;
	u64 bytes;
	struct u64_stats_sync syncp;
	};

	struct veth_priv {
	struct net_device __rcu *peer;
	atomic64_t dropped;
	unsigned requested_headroom;
	};

	/*
	* ethtool interface
	*/

	static struct {
	const char string[ETH_GSTRING_LEN];
	} ethtool_stats_keys[] = {
	{ "peer_ifindex" },
	};

	static int veth_get_link_ksettings(struct net_device *dev,
	struct ethtool_link_ksettings *cmd)
	{
	cmd->base.speed = SPEED_10000;
	cmd->base.duplex = DUPLEX_FULL;
	cmd->base.port = PORT_TP;
	cmd->base.autoneg = AUTONEG_DISABLE;
	return 0;
	}

	static void veth_get_drvinfo(struct net_device dev, struct ethtool_drvinfo info)
	{
	strlcpy(info->driver, DRV_NAME, sizeof(info->driver));
	strlcpy(info->version, DRV_VERSION, sizeof(info->version));
	}

	static void veth_get_strings(struct net_device dev, u32 stringset, u8 buf)
	{
	switch(stringset) {
	case ETH_SS_STATS:
	memcpy(buf, &ethtool_stats_keys, sizeof(ethtool_stats_keys));
	break;
	}
	}

	static int veth_get_sset_count(struct net_device *dev, int sset)
	{
	switch (sset) {
	case ETH_SS_STATS:
	return ARRAY_SIZE(ethtool_stats_keys);
	default:
	return -EOPNOTSUPP;
	}
	}

	static void veth_get_ethtool_stats(struct net_device *dev,
	struct ethtool_stats stats, u64 data)
	{
	struct veth_priv *priv = netdev_priv(dev);
	struct net_device *peer = rtnl_dereference(priv->peer);

	data[0] = peer ? peer->ifindex : 0;
	}

	static const struct ethtool_ops veth_ethtool_ops = {
	.get_drvinfo = veth_get_drvinfo,
	.get_link = ethtool_op_get_link,
	.get_strings = veth_get_strings,
	.get_sset_count = veth_get_sset_count,
	.get_ethtool_stats = veth_get_ethtool_stats,
	.get_link_ksettings = veth_get_link_ksettings,
	};

	static netdev_tx_t veth_xmit(struct sk_buff skb, struct net_device dev)
	{
	struct veth_priv *priv = netdev_priv(dev);
	struct net_device *rcv;
	int length = skb->len;

	rcu_read_lock();
	rcv = rcu_dereference(priv->peer);
	if (unlikely(!rcv)) {
	kfree_skb(skb);
	goto drop;
	}

	if (likely(dev_forward_skb(rcv, skb) == NET_RX_SUCCESS)) {
	struct pcpu_vstats *stats = this_cpu_ptr(dev->vstats);

	u64_stats_update_begin(&stats->syncp);
	stats->bytes += length;
	stats->packets++;
	u64_stats_update_end(&stats->syncp);
	} else {
	drop:
	atomic64_inc(&priv->dropped);
	}
	rcu_read_unlock();
	return NETDEV_TX_OK;
	}

	/*
	* general routines
	*/

	static u64 veth_stats_one(struct pcpu_vstats result, struct net_device dev)
	{
	struct veth_priv *priv = netdev_priv(dev);
	int cpu;

	result->packets = 0;
	result->bytes = 0;
	for_each_possible_cpu(cpu) {
	struct pcpu_vstats *stats = per_cpu_ptr(dev->vstats, cpu);
	u64 packets, bytes;
	unsigned int start;

	do {
	start = u64_stats_fetch_begin_irq(&stats->syncp);
	packets = stats->packets;
	bytes = stats->bytes;
	} while (u64_stats_fetch_retry_irq(&stats->syncp, start));
	result->packets += packets;
	result->bytes += bytes;
	}
	return atomic64_read(&priv->dropped);
	}

	static void veth_get_stats64(struct net_device *dev,
	struct rtnl_link_stats64 *tot)
	{
	struct veth_priv *priv = netdev_priv(dev);
	struct net_device *peer;
	struct pcpu_vstats one;

	tot->tx_dropped = veth_stats_one(&one, dev);
	tot->tx_bytes = one.bytes;
	tot->tx_packets = one.packets;

	rcu_read_lock();
	peer = rcu_dereference(priv->peer);
	if (peer) {
	tot->rx_dropped = veth_stats_one(&one, peer);
	tot->rx_bytes = one.bytes;
	tot->rx_packets = one.packets;
	}
	rcu_read_unlock();
	}

	/* fake multicast ability */
	static void veth_set_multicast_list(struct net_device *dev)
	{
	}

	static int veth_open(struct net_device *dev)
	{
	struct veth_priv *priv = netdev_priv(dev);
	struct net_device *peer = rtnl_dereference(priv->peer);

	if (!peer)
	return -ENOTCONN;

	if (peer->flags & IFF_UP) {
	netif_carrier_on(dev);
	netif_carrier_on(peer);
	}
	return 0;
	}

	static int veth_close(struct net_device *dev)
	{
	struct veth_priv *priv = netdev_priv(dev);
	struct net_device *peer = rtnl_dereference(priv->peer);

	netif_carrier_off(dev);
	if (peer)
	netif_carrier_off(peer);

	return 0;
	}

	static int is_valid_veth_mtu(int mtu)
	{
	return mtu >= ETH_MIN_MTU && mtu <= ETH_MAX_MTU;
	}

	static int veth_dev_init(struct net_device *dev)
	{
	dev->vstats = netdev_alloc_pcpu_stats(struct pcpu_vstats);
	if (!dev->vstats)
	return -ENOMEM;
	return 0;
	}

	static void veth_dev_free(struct net_device *dev)
	{
	free_percpu(dev->vstats);
	}

	#ifdef CONFIG_NET_POLL_CONTROLLER
	static void veth_poll_controller(struct net_device *dev)
	{
	/* veth only receives frames when its peer sends one
	* Since it's a synchronous operation, we are guaranteed
	* never to have pending data when we poll for it so
	* there is nothing to do here.
	*
	* We need this though so netpoll recognizes us as an interface that
	* supports polling, which enables bridge devices in virt setups to
	* still use netconsole
	*/
	}
	#endif /* CONFIG_NET_POLL_CONTROLLER */

	static int veth_get_iflink(const struct net_device *dev)
	{
	struct veth_priv *priv = netdev_priv(dev);
	struct net_device *peer;
	int iflink;

	rcu_read_lock();
	peer = rcu_dereference(priv->peer);
	iflink = peer ? peer->ifindex : 0;
	rcu_read_unlock();

	return iflink;
	}

	static void veth_set_rx_headroom(struct net_device *dev, int new_hr)
	{
	struct veth_priv peer_priv, priv = netdev_priv(dev);
	struct net_device *peer;

	if (new_hr < 0)
	new_hr = 0;

	rcu_read_lock();
	peer = rcu_dereference(priv->peer);
	if (unlikely(!peer))
	goto out;

	peer_priv = netdev_priv(peer);
	priv->requested_headroom = new_hr;
	new_hr = max(priv->requested_headroom, peer_priv->requested_headroom);
	dev->needed_headroom = new_hr;
	peer->needed_headroom = new_hr;

	out:
	rcu_read_unlock();
	}

	static const struct net_device_ops veth_netdev_ops = {
	.ndo_init = veth_dev_init,
	.ndo_open = veth_open,
	.ndo_stop = veth_close,
	.ndo_start_xmit = veth_xmit,
	.ndo_get_stats64 = veth_get_stats64,
	.ndo_set_rx_mode = veth_set_multicast_list,
	.ndo_set_mac_address = eth_mac_addr,
	#ifdef CONFIG_NET_POLL_CONTROLLER
	.ndo_poll_controller = veth_poll_controller,
	#endif
	.ndo_get_iflink = veth_get_iflink,
	.ndo_features_check = passthru_features_check,
	.ndo_set_rx_headroom = veth_set_rx_headroom,
	};

	#define VETH_FEATURES (NETIF_F_SG \| NETIF_F_FRAGLIST \| NETIF_F_HW_CSUM \| \
	NETIF_F_RXCSUM \| NETIF_F_SCTP_CRC \| NETIF_F_HIGHDMA \| \
	NETIF_F_GSO_SOFTWARE \| NETIF_F_GSO_ENCAP_ALL \| \
	NETIF_F_HW_VLAN_CTAG_TX \| NETIF_F_HW_VLAN_CTAG_RX \| \
	NETIF_F_HW_VLAN_STAG_TX \| NETIF_F_HW_VLAN_STAG_RX )

	static void veth_setup(struct net_device *dev)
	{
	ether_setup(dev);

	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
	dev->priv_flags \|= IFF_LIVE_ADDR_CHANGE;
	dev->priv_flags \|= IFF_NO_QUEUE;
	dev->priv_flags \|= IFF_PHONY_HEADROOM;

	dev->netdev_ops = &veth_netdev_ops;
	dev->ethtool_ops = &veth_ethtool_ops;
	dev->features \|= NETIF_F_LLTX;
	dev->features \|= VETH_FEATURES;
	dev->vlan_features = dev->features &
	~(NETIF_F_HW_VLAN_CTAG_TX \|
	NETIF_F_HW_VLAN_STAG_TX \|
	NETIF_F_HW_VLAN_CTAG_RX \|
	NETIF_F_HW_VLAN_STAG_RX);
	dev->needs_free_netdev = true;
	dev->priv_destructor = veth_dev_free;
	dev->max_mtu = ETH_MAX_MTU;

	dev->hw_features = VETH_FEATURES;
	dev->hw_enc_features = VETH_FEATURES;
	dev->mpls_features = NETIF_F_HW_CSUM \| NETIF_F_GSO_SOFTWARE;
	}

	/*
	* netlink interface
	*/

	static int veth_validate(struct nlattr tb[], struct nlattr data[],
	struct netlink_ext_ack *extack)
	{
	if (tb[IFLA_ADDRESS]) {
	if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN)
	return -EINVAL;
	if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS])))
	return -EADDRNOTAVAIL;
	}
	if (tb[IFLA_MTU]) {
	if (!is_valid_veth_mtu(nla_get_u32(tb[IFLA_MTU])))
	return -EINVAL;
	}
	return 0;
	}

	static struct rtnl_link_ops veth_link_ops;

	static int veth_newlink(struct net src_net, struct net_device dev,
	struct nlattr tb[], struct nlattr data[],
	struct netlink_ext_ack *extack)
	{
	int err;
	struct net_device *peer;
	struct veth_priv *priv;
	char ifname[IFNAMSIZ];
	struct nlattr peer_tb[IFLA_MAX + 1], *tbp;
	unsigned char name_assign_type;
	struct ifinfomsg *ifmp;
	struct net *net;

	/*
	* create and register peer first
	*/
	if (data != NULL && data[VETH_INFO_PEER] != NULL) {
	struct nlattr *nla_peer;

	nla_peer = data[VETH_INFO_PEER];
	ifmp = nla_data(nla_peer);
	err = rtnl_nla_parse_ifla(peer_tb,
	nla_data(nla_peer) + sizeof(struct ifinfomsg),
	nla_len(nla_peer) - sizeof(struct ifinfomsg),
	NULL);
	if (err < 0)
	return err;

	err = veth_validate(peer_tb, NULL, extack);
	if (err < 0)
	return err;

	tbp = peer_tb;
	} else {
	ifmp = NULL;
	tbp = tb;
	}

	if (tbp[IFLA_IFNAME]) {
	nla_strlcpy(ifname, tbp[IFLA_IFNAME], IFNAMSIZ);
	name_assign_type = NET_NAME_USER;
	} else {
	snprintf(ifname, IFNAMSIZ, DRV_NAME "%%d");
	name_assign_type = NET_NAME_ENUM;
	}

	net = rtnl_link_get_net(src_net, tbp);
	if (IS_ERR(net))
	return PTR_ERR(net);

	peer = rtnl_create_link(net, ifname, name_assign_type,
	&veth_link_ops, tbp);
	if (IS_ERR(peer)) {
	put_net(net);
	return PTR_ERR(peer);
	}

	if (tbp[IFLA_ADDRESS] == NULL)
	eth_hw_addr_random(peer);

	if (ifmp && (dev->ifindex != 0))
	peer->ifindex = ifmp->ifi_index;

	err = register_netdevice(peer);
	put_net(net);
	net = NULL;
	if (err < 0)
	goto err_register_peer;

	netif_carrier_off(peer);

	err = rtnl_configure_link(peer, ifmp);
	if (err < 0)
	goto err_configure_peer;

	/*
	* register dev last
	*
	* note, that since we've registered new device the dev's name
	* should be re-allocated
	*/

	if (tb[IFLA_ADDRESS] == NULL)
	eth_hw_addr_random(dev);

	if (tb[IFLA_IFNAME])
	nla_strlcpy(dev->name, tb[IFLA_IFNAME], IFNAMSIZ);
	else
	snprintf(dev->name, IFNAMSIZ, DRV_NAME "%%d");

	err = register_netdevice(dev);
	if (err < 0)
	goto err_register_dev;

	netif_carrier_off(dev);

	/*
	* tie the deviced together
	*/

	priv = netdev_priv(dev);
	rcu_assign_pointer(priv->peer, peer);

	priv = netdev_priv(peer);
	rcu_assign_pointer(priv->peer, dev);
	return 0;

	err_register_dev:
	/* nothing to do */
	err_configure_peer:
	unregister_netdevice(peer);
	return err;

	err_register_peer:
	free_netdev(peer);
	return err;
	}

	static void veth_dellink(struct net_device dev, struct list_head head)
	{
	struct veth_priv *priv;
	struct net_device *peer;

	priv = netdev_priv(dev);
	peer = rtnl_dereference(priv->peer);

	/* Note : dellink() is called from default_device_exit_batch(),
	* before a rcu_synchronize() point. The devices are guaranteed
	* not being freed before one RCU grace period.
	*/
	RCU_INIT_POINTER(priv->peer, NULL);
	unregister_netdevice_queue(dev, head);

	if (peer) {
	priv = netdev_priv(peer);
	RCU_INIT_POINTER(priv->peer, NULL);
	unregister_netdevice_queue(peer, head);
	}
	}

	static const struct nla_policy veth_policy[VETH_INFO_MAX + 1] = {
	[VETH_INFO_PEER] = { .len = sizeof(struct ifinfomsg) },
	};

	static struct net veth_get_link_net(const struct net_device dev)
	{
	struct veth_priv *priv = netdev_priv(dev);
	struct net_device *peer = rtnl_dereference(priv->peer);

	return peer ? dev_net(peer) : dev_net(dev);
	}

	static struct rtnl_link_ops veth_link_ops = {
	.kind = DRV_NAME,
	.priv_size = sizeof(struct veth_priv),
	.setup = veth_setup,
	.validate = veth_validate,
	.newlink = veth_newlink,
	.dellink = veth_dellink,
	.policy = veth_policy,
	.maxtype = VETH_INFO_MAX,
	.get_link_net = veth_get_link_net,
	};

	/*
	* init/fini
	*/

	static __init int veth_init(void)
	{
	return rtnl_link_register(&veth_link_ops);
	}

	static __exit void veth_exit(void)
	{
	rtnl_link_unregister(&veth_link_ops);
	}

	module_init(veth_init);
	module_exit(veth_exit);

	MODULE_DESCRIPTION("Virtual Ethernet Tunnel");
	MODULE_LICENSE("GPL v2");
	MODULE_ALIAS_RTNL_LINK(DRV_NAME);