linux/drivers/net/veth.c

/*
 *  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>
#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/ptr_ring.h>
#include <linux/skb_array.h>
#include <linux/bpf_trace.h>

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

#define VETH_RING_SIZE		256
#define VETH_XDP_HEADROOM	(XDP_PACKET_HEADROOM + NET_IP_ALIGN)

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

struct veth_priv {
	struct napi_struct	xdp_napi;
	struct net_device	*dev;
	struct bpf_prog __rcu	*xdp_prog;
	struct bpf_prog		*_xdp_prog;
	struct net_device __rcu	*peer;
	atomic64_t		dropped;
	unsigned		requested_headroom;
	bool			rx_notify_masked;
	struct ptr_ring		xdp_ring;
	struct xdp_rxq_info	xdp_rxq;
};

/*
 * 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,
};

/* general routines */

static void __veth_xdp_flush(struct veth_priv *priv)
{
	/* Write ptr_ring before reading rx_notify_masked */
	smp_mb();
	if (!priv->rx_notify_masked) {
		priv->rx_notify_masked = true;
		napi_schedule(&priv->xdp_napi);
	}
}

static int veth_xdp_rx(struct veth_priv *priv, struct sk_buff *skb)
{
	if (unlikely(ptr_ring_produce(&priv->xdp_ring, skb))) {
		dev_kfree_skb_any(skb);
		return NET_RX_DROP;
	}

	return NET_RX_SUCCESS;
}

static int veth_forward_skb(struct net_device *dev, struct sk_buff *skb, bool xdp)
{
	struct veth_priv *priv = netdev_priv(dev);

	return __dev_forward_skb(dev, skb) ?: xdp ?
		veth_xdp_rx(priv, skb) :
		netif_rx(skb);
}

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

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

	rcv_priv = netdev_priv(rcv);
	rcv_xdp = rcu_access_pointer(rcv_priv->xdp_prog);

	if (likely(veth_forward_skb(rcv, skb, rcv_xdp) == 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);
	}

	if (rcv_xdp)
		__veth_xdp_flush(rcv_priv);

	rcu_read_unlock();

	return NETDEV_TX_OK;
}

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 struct sk_buff *veth_build_skb(void *head, int headroom, int len,
				      int buflen)
{
	struct sk_buff *skb;

	if (!buflen) {
		buflen = SKB_DATA_ALIGN(headroom + len) +
			 SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
	}
	skb = build_skb(head, buflen);
	if (!skb)
		return NULL;

	skb_reserve(skb, headroom);
	skb_put(skb, len);

	return skb;
}

static struct sk_buff *veth_xdp_rcv_skb(struct veth_priv *priv,
					struct sk_buff *skb)
{
	u32 pktlen, headroom, act, metalen;
	void *orig_data, *orig_data_end;
	struct bpf_prog *xdp_prog;
	int mac_len, delta, off;
	struct xdp_buff xdp;

	rcu_read_lock();
	xdp_prog = rcu_dereference(priv->xdp_prog);
	if (unlikely(!xdp_prog)) {
		rcu_read_unlock();
		goto out;
	}

	mac_len = skb->data - skb_mac_header(skb);
	pktlen = skb->len + mac_len;
	headroom = skb_headroom(skb) - mac_len;

	if (skb_shared(skb) || skb_head_is_locked(skb) ||
	    skb_is_nonlinear(skb) || headroom < XDP_PACKET_HEADROOM) {
		struct sk_buff *nskb;
		int size, head_off;
		void *head, *start;
		struct page *page;

		size = SKB_DATA_ALIGN(VETH_XDP_HEADROOM + pktlen) +
		       SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
		if (size > PAGE_SIZE)
			goto drop;

		page = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
		if (!page)
			goto drop;

		head = page_address(page);
		start = head + VETH_XDP_HEADROOM;
		if (skb_copy_bits(skb, -mac_len, start, pktlen)) {
			page_frag_free(head);
			goto drop;
		}

		nskb = veth_build_skb(head,
				      VETH_XDP_HEADROOM + mac_len, skb->len,
				      PAGE_SIZE);
		if (!nskb) {
			page_frag_free(head);
			goto drop;
		}

		skb_copy_header(nskb, skb);
		head_off = skb_headroom(nskb) - skb_headroom(skb);
		skb_headers_offset_update(nskb, head_off);
		if (skb->sk)
			skb_set_owner_w(nskb, skb->sk);
		consume_skb(skb);
		skb = nskb;
	}

	xdp.data_hard_start = skb->head;
	xdp.data = skb_mac_header(skb);
	xdp.data_end = xdp.data + pktlen;
	xdp.data_meta = xdp.data;
	xdp.rxq = &priv->xdp_rxq;
	orig_data = xdp.data;
	orig_data_end = xdp.data_end;

	act = bpf_prog_run_xdp(xdp_prog, &xdp);

	switch (act) {
	case XDP_PASS:
		break;
	default:
		bpf_warn_invalid_xdp_action(act);
	case XDP_ABORTED:
		trace_xdp_exception(priv->dev, xdp_prog, act);
	case XDP_DROP:
		goto drop;
	}
	rcu_read_unlock();

	delta = orig_data - xdp.data;
	off = mac_len + delta;
	if (off > 0)
		__skb_push(skb, off);
	else if (off < 0)
		__skb_pull(skb, -off);
	skb->mac_header -= delta;
	off = xdp.data_end - orig_data_end;
	if (off != 0)
		__skb_put(skb, off);
	skb->protocol = eth_type_trans(skb, priv->dev);

	metalen = xdp.data - xdp.data_meta;
	if (metalen)
		skb_metadata_set(skb, metalen);
out:
	return skb;
drop:
	rcu_read_unlock();
	kfree_skb(skb);
	return NULL;
}

static int veth_xdp_rcv(struct veth_priv *priv, int budget)
{
	int i, done = 0;

	for (i = 0; i < budget; i++) {
		struct sk_buff *skb = __ptr_ring_consume(&priv->xdp_ring);

		if (!skb)
			break;

		skb = veth_xdp_rcv_skb(priv, skb);

		if (skb)
			napi_gro_receive(&priv->xdp_napi, skb);

		done++;
	}

	return done;
}

static int veth_poll(struct napi_struct *napi, int budget)
{
	struct veth_priv *priv =
		container_of(napi, struct veth_priv, xdp_napi);
	int done;

	done = veth_xdp_rcv(priv, budget);

	if (done < budget && napi_complete_done(napi, done)) {
		/* Write rx_notify_masked before reading ptr_ring */
		smp_store_mb(priv->rx_notify_masked, false);
		if (unlikely(!__ptr_ring_empty(&priv->xdp_ring))) {
			priv->rx_notify_masked = true;
			napi_schedule(&priv->xdp_napi);
		}
	}

	return done;
}

static int veth_napi_add(struct net_device *dev)
{
	struct veth_priv *priv = netdev_priv(dev);
	int err;

	err = ptr_ring_init(&priv->xdp_ring, VETH_RING_SIZE, GFP_KERNEL);
	if (err)
		return err;

	netif_napi_add(dev, &priv->xdp_napi, veth_poll, NAPI_POLL_WEIGHT);
	napi_enable(&priv->xdp_napi);

	return 0;
}

static void veth_napi_del(struct net_device *dev)
{
	struct veth_priv *priv = netdev_priv(dev);

	napi_disable(&priv->xdp_napi);
	netif_napi_del(&priv->xdp_napi);
	priv->rx_notify_masked = false;
	ptr_ring_cleanup(&priv->xdp_ring, __skb_array_destroy_skb);
}

static int veth_enable_xdp(struct net_device *dev)
{
	struct veth_priv *priv = netdev_priv(dev);
	int err;

	if (!xdp_rxq_info_is_reg(&priv->xdp_rxq)) {
		err = xdp_rxq_info_reg(&priv->xdp_rxq, dev, 0);
		if (err < 0)
			return err;

		err = xdp_rxq_info_reg_mem_model(&priv->xdp_rxq,
						 MEM_TYPE_PAGE_SHARED, NULL);
		if (err < 0)
			goto err;

		err = veth_napi_add(dev);
		if (err)
			goto err;
	}

	rcu_assign_pointer(priv->xdp_prog, priv->_xdp_prog);

	return 0;
err:
	xdp_rxq_info_unreg(&priv->xdp_rxq);

	return err;
}

static void veth_disable_xdp(struct net_device *dev)
{
	struct veth_priv *priv = netdev_priv(dev);

	rcu_assign_pointer(priv->xdp_prog, NULL);
	veth_napi_del(dev);
	xdp_rxq_info_unreg(&priv->xdp_rxq);
}

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

	if (!peer)
		return -ENOTCONN;

	if (priv->_xdp_prog) {
		err = veth_enable_xdp(dev);
		if (err)
			return err;
	}

	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);

	if (priv->_xdp_prog)
		veth_disable_xdp(dev);

	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 has nothing to do with disabling irqs, 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 int veth_xdp_set(struct net_device *dev, struct bpf_prog *prog,
			struct netlink_ext_ack *extack)
{
	struct veth_priv *priv = netdev_priv(dev);
	struct bpf_prog *old_prog;
	struct net_device *peer;
	int err;

	old_prog = priv->_xdp_prog;
	priv->_xdp_prog = prog;
	peer = rtnl_dereference(priv->peer);

	if (prog) {
		if (!peer) {
			NL_SET_ERR_MSG_MOD(extack, "Cannot set XDP when peer is detached");
			err = -ENOTCONN;
			goto err;
		}

		if (dev->flags & IFF_UP) {
			err = veth_enable_xdp(dev);
			if (err) {
				NL_SET_ERR_MSG_MOD(extack, "Setup for XDP failed");
				goto err;
			}
		}
	}

	if (old_prog) {
		if (!prog && dev->flags & IFF_UP)
			veth_disable_xdp(dev);
		bpf_prog_put(old_prog);
	}

	return 0;
err:
	priv->_xdp_prog = old_prog;

	return err;
}

static u32 veth_xdp_query(struct net_device *dev)
{
	struct veth_priv *priv = netdev_priv(dev);
	const struct bpf_prog *xdp_prog;

	xdp_prog = priv->_xdp_prog;
	if (xdp_prog)
		return xdp_prog->aux->id;

	return 0;
}

static int veth_xdp(struct net_device *dev, struct netdev_bpf *xdp)
{
	switch (xdp->command) {
	case XDP_SETUP_PROG:
		return veth_xdp_set(dev, xdp->prog, xdp->extack);
	case XDP_QUERY_PROG:
		xdp->prog_id = veth_xdp_query(dev);
		return 0;
	default:
		return -EINVAL;
	}
}

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,
	.ndo_bpf		= veth_xdp,
};

#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 (ifmp && 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 (!ifmp || !tbp[IFLA_ADDRESS])
		eth_hw_addr_random(peer);

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

	peer->gso_max_size = dev->gso_max_size;
	peer->gso_max_segs = dev->gso_max_segs;

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

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