// SPDX-License-Identifier: GPL-2.0-only
/*
 *  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/netdev_lock.h>
#include <net/xfrm.h>
#include <net/xdp.h>
#include <linux/veth.h>
#include <linux/module.h>
#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/ptr_ring.h>
#include <linux/bpf_trace.h>
#include <linux/net_tstamp.h>
#include <linux/skbuff_ref.h>
#include <net/page_pool/helpers.h>

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

#define VETH_XDP_FLAG           BIT(0)
#define VETH_RING_SIZE          256
#define VETH_XDP_HEADROOM       (XDP_PACKET_HEADROOM + NET_IP_ALIGN)

#define VETH_XDP_TX_BULK_SIZE   16
#define VETH_XDP_BATCH          16

struct veth_stats {
        u64     rx_drops;
        /* xdp */
        u64     xdp_packets;
        u64     xdp_bytes;
        u64     xdp_redirect;
        u64     xdp_drops;
        u64     xdp_tx;
        u64     xdp_tx_err;
        u64     peer_tq_xdp_xmit;
        u64     peer_tq_xdp_xmit_err;
};

struct veth_rq_stats {
        struct veth_stats       vs;
        struct u64_stats_sync   syncp;
};

struct veth_rq {
        struct napi_struct      xdp_napi;
        struct napi_struct __rcu *napi; /* points to xdp_napi when the latter is initialized */
        struct net_device       *dev;
        struct bpf_prog __rcu   *xdp_prog;
        struct xdp_mem_info     xdp_mem;
        struct veth_rq_stats    stats;
        bool                    rx_notify_masked;
        struct ptr_ring         xdp_ring;
        struct xdp_rxq_info     xdp_rxq;
        struct page_pool        *page_pool;
};

struct veth_priv {
        struct net_device __rcu *peer;
        atomic64_t              dropped;
        struct bpf_prog         *_xdp_prog;
        struct veth_rq          *rq;
        unsigned int            requested_headroom;
};

struct veth_xdp_tx_bq {
        struct xdp_frame *q[VETH_XDP_TX_BULK_SIZE];
        unsigned int count;
};

/*
 * ethtool interface
 */

struct veth_q_stat_desc {
        char    desc[ETH_GSTRING_LEN];
        size_t  offset;
};

#define VETH_RQ_STAT(m) offsetof(struct veth_stats, m)

static const struct veth_q_stat_desc veth_rq_stats_desc[] = {
        { "xdp_packets",        VETH_RQ_STAT(xdp_packets) },
        { "xdp_bytes",          VETH_RQ_STAT(xdp_bytes) },
        { "drops",              VETH_RQ_STAT(rx_drops) },
        { "xdp_redirect",       VETH_RQ_STAT(xdp_redirect) },
        { "xdp_drops",          VETH_RQ_STAT(xdp_drops) },
        { "xdp_tx",             VETH_RQ_STAT(xdp_tx) },
        { "xdp_tx_errors",      VETH_RQ_STAT(xdp_tx_err) },
};

#define VETH_RQ_STATS_LEN       ARRAY_SIZE(veth_rq_stats_desc)

static const struct veth_q_stat_desc veth_tq_stats_desc[] = {
        { "xdp_xmit",           VETH_RQ_STAT(peer_tq_xdp_xmit) },
        { "xdp_xmit_errors",    VETH_RQ_STAT(peer_tq_xdp_xmit_err) },
};

#define VETH_TQ_STATS_LEN       ARRAY_SIZE(veth_tq_stats_desc)

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

struct veth_xdp_buff {
        struct xdp_buff xdp;
        struct sk_buff *skb;
};

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)
{
        strscpy(info->driver, DRV_NAME, sizeof(info->driver));
        strscpy(info->version, DRV_VERSION, sizeof(info->version));
}

static void veth_get_strings(struct net_device *dev, u32 stringset, u8 *buf)
{
        u8 *p = buf;
        int i, j;

        switch(stringset) {
        case ETH_SS_STATS:
                memcpy(p, &ethtool_stats_keys, sizeof(ethtool_stats_keys));
                p += sizeof(ethtool_stats_keys);
                for (i = 0; i < dev->real_num_rx_queues; i++)
                        for (j = 0; j < VETH_RQ_STATS_LEN; j++)
                                ethtool_sprintf(&p, "rx_queue_%u_%.18s",
                                                i, veth_rq_stats_desc[j].desc);

                for (i = 0; i < dev->real_num_tx_queues; i++)
                        for (j = 0; j < VETH_TQ_STATS_LEN; j++)
                                ethtool_sprintf(&p, "tx_queue_%u_%.18s",
                                                i, veth_tq_stats_desc[j].desc);

                page_pool_ethtool_stats_get_strings(p);
                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) +
                       VETH_RQ_STATS_LEN * dev->real_num_rx_queues +
                       VETH_TQ_STATS_LEN * dev->real_num_tx_queues +
                       page_pool_ethtool_stats_get_count();
        default:
                return -EOPNOTSUPP;
        }
}

static void veth_get_page_pool_stats(struct net_device *dev, u64 *data)
{
#ifdef CONFIG_PAGE_POOL_STATS
        struct veth_priv *priv = netdev_priv(dev);
        struct page_pool_stats pp_stats = {};
        int i;

        for (i = 0; i < dev->real_num_rx_queues; i++) {
                if (!priv->rq[i].page_pool)
                        continue;
                page_pool_get_stats(priv->rq[i].page_pool, &pp_stats);
        }
        page_pool_ethtool_stats_get(data, &pp_stats);
#endif /* CONFIG_PAGE_POOL_STATS */
}

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

        data[0] = peer ? peer->ifindex : 0;
        idx = 1;
        for (i = 0; i < dev->real_num_rx_queues; i++) {
                const struct veth_rq_stats *rq_stats = &priv->rq[i].stats;
                const void *stats_base = (void *)&rq_stats->vs;
                unsigned int start;
                size_t offset;

                do {
                        start = u64_stats_fetch_begin(&rq_stats->syncp);
                        for (j = 0; j < VETH_RQ_STATS_LEN; j++) {
                                offset = veth_rq_stats_desc[j].offset;
                                data[idx + j] = *(u64 *)(stats_base + offset);
                        }
                } while (u64_stats_fetch_retry(&rq_stats->syncp, start));
                idx += VETH_RQ_STATS_LEN;
        }
        pp_idx = idx;

        if (!peer)
                goto page_pool_stats;

        rcv_priv = netdev_priv(peer);
        for (i = 0; i < peer->real_num_rx_queues; i++) {
                const struct veth_rq_stats *rq_stats = &rcv_priv->rq[i].stats;
                const void *base = (void *)&rq_stats->vs;
                unsigned int start, tx_idx = idx;
                u64 buf[VETH_TQ_STATS_LEN];
                size_t offset;

                do {
                        start = u64_stats_fetch_begin(&rq_stats->syncp);
                        for (j = 0; j < VETH_TQ_STATS_LEN; j++) {
                                offset = veth_tq_stats_desc[j].offset;
                                buf[j] = *(u64 *)(base + offset);
                        }
                } while (u64_stats_fetch_retry(&rq_stats->syncp, start));

                tx_idx += (i % dev->real_num_tx_queues) * VETH_TQ_STATS_LEN;
                for (j = 0; j < VETH_TQ_STATS_LEN; j++)
                        data[tx_idx + j] += buf[j];
        }
        pp_idx = idx + dev->real_num_tx_queues * VETH_TQ_STATS_LEN;

page_pool_stats:
        veth_get_page_pool_stats(dev, &data[pp_idx]);
}

static void veth_get_channels(struct net_device *dev,
                              struct ethtool_channels *channels)
{
        channels->tx_count = dev->real_num_tx_queues;
        channels->rx_count = dev->real_num_rx_queues;
        channels->max_tx = dev->num_tx_queues;
        channels->max_rx = dev->num_rx_queues;
}

static int veth_set_channels(struct net_device *dev,
                             struct ethtool_channels *ch);

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,
        .get_ts_info            = ethtool_op_get_ts_info,
        .get_channels           = veth_get_channels,
        .set_channels           = veth_set_channels,
};

/* general routines */

static bool veth_is_xdp_frame(void *ptr)
{
        return (unsigned long)ptr & VETH_XDP_FLAG;
}

static struct xdp_frame *veth_ptr_to_xdp(void *ptr)
{
        return (void *)((unsigned long)ptr & ~VETH_XDP_FLAG);
}

static void *veth_xdp_to_ptr(struct xdp_frame *xdp)
{
        return (void *)((unsigned long)xdp | VETH_XDP_FLAG);
}

static void veth_ptr_free(void *ptr)
{
        if (veth_is_xdp_frame(ptr))
                xdp_return_frame(veth_ptr_to_xdp(ptr));
        else
                kfree_skb(ptr);
}

static void __veth_xdp_flush(struct veth_rq *rq)
{
        /* Write ptr_ring before reading rx_notify_masked */
        smp_mb();
        if (!READ_ONCE(rq->rx_notify_masked) &&
            napi_schedule_prep(&rq->xdp_napi)) {
                WRITE_ONCE(rq->rx_notify_masked, true);
                __napi_schedule(&rq->xdp_napi);
        }
}

static int veth_xdp_rx(struct veth_rq *rq, struct sk_buff *skb)
{
        if (unlikely(ptr_ring_produce(&rq->xdp_ring, skb)))
                return NETDEV_TX_BUSY; /* signal qdisc layer */

        return NET_RX_SUCCESS; /* same as NETDEV_TX_OK */
}

static int veth_forward_skb(struct net_device *dev, struct sk_buff *skb,
                            struct veth_rq *rq, bool xdp)
{
        return __dev_forward_skb(dev, skb) ?: xdp ?
                veth_xdp_rx(rq, skb) :
                __netif_rx(skb);
}

/* return true if the specified skb has chances of GRO aggregation
 * Don't strive for accuracy, but try to avoid GRO overhead in the most
 * common scenarios.
 * When XDP is enabled, all traffic is considered eligible, as the xmit
 * device has TSO off.
 * When TSO is enabled on the xmit device, we are likely interested only
 * in UDP aggregation, explicitly check for that if the skb is suspected
 * - the sock_wfree destructor is used by UDP, ICMP and XDP sockets -
 * to belong to locally generated UDP traffic.
 */
static bool veth_skb_is_eligible_for_gro(const struct net_device *dev,
                                         const struct net_device *rcv,
                                         const struct sk_buff *skb)
{
        return !(dev->features & NETIF_F_ALL_TSO) ||
                (skb->destructor == sock_wfree &&
                 rcv->features & (NETIF_F_GRO_FRAGLIST | NETIF_F_GRO_UDP_FWD));
}

static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct veth_priv *rcv_priv, *priv = netdev_priv(dev);
        struct veth_rq *rq = NULL;
        struct netdev_queue *txq;
        struct net_device *rcv;
        int length = skb->len;
        bool use_napi = false;
        int ret, rxq;

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

        rcv_priv = netdev_priv(rcv);
        rxq = skb_get_queue_mapping(skb);
        if (rxq < rcv->real_num_rx_queues) {
                rq = &rcv_priv->rq[rxq];

                /* The napi pointer is available when an XDP program is
                 * attached or when GRO is enabled
                 * Don't bother with napi/GRO if the skb can't be aggregated
                 */
                use_napi = rcu_access_pointer(rq->napi) &&
                           veth_skb_is_eligible_for_gro(dev, rcv, skb);
        }

        skb_tx_timestamp(skb);

        ret = veth_forward_skb(rcv, skb, rq, use_napi);
        switch (ret) {
        case NET_RX_SUCCESS: /* same as NETDEV_TX_OK */
                if (!use_napi)
                        dev_sw_netstats_tx_add(dev, 1, length);
                else
                        __veth_xdp_flush(rq);
                break;
        case NETDEV_TX_BUSY:
                /* If a qdisc is attached to our virtual device, returning
                 * NETDEV_TX_BUSY is allowed.
                 */
                txq = netdev_get_tx_queue(dev, rxq);

                if (qdisc_txq_has_no_queue(txq)) {
                        dev_kfree_skb_any(skb);
                        goto drop;
                }
                /* Restore Eth hdr pulled by dev_forward_skb/eth_type_trans */
                __skb_push(skb, ETH_HLEN);
                netif_tx_stop_queue(txq);
                /* Makes sure NAPI peer consumer runs. Consumer is responsible
                 * for starting txq again, until then ndo_start_xmit (this
                 * function) will not be invoked by the netstack again.
                 */
                __veth_xdp_flush(rq);
                break;
        case NET_RX_DROP: /* same as NET_XMIT_DROP */
drop:
                atomic64_inc(&priv->dropped);
                ret = NET_XMIT_DROP;
                break;
        default:
                net_crit_ratelimited("%s(%s): Invalid return code(%d)",
                                     __func__, dev->name, ret);
        }
        rcu_read_unlock();

        return ret;
}

static void veth_stats_rx(struct veth_stats *result, struct net_device *dev)
{
        struct veth_priv *priv = netdev_priv(dev);
        int i;

        result->peer_tq_xdp_xmit_err = 0;
        result->xdp_packets = 0;
        result->xdp_tx_err = 0;
        result->xdp_bytes = 0;
        result->rx_drops = 0;
        for (i = 0; i < dev->num_rx_queues; i++) {
                u64 packets, bytes, drops, xdp_tx_err, peer_tq_xdp_xmit_err;
                struct veth_rq_stats *stats = &priv->rq[i].stats;
                unsigned int start;

                do {
                        start = u64_stats_fetch_begin(&stats->syncp);
                        peer_tq_xdp_xmit_err = stats->vs.peer_tq_xdp_xmit_err;
                        xdp_tx_err = stats->vs.xdp_tx_err;
                        packets = stats->vs.xdp_packets;
                        bytes = stats->vs.xdp_bytes;
                        drops = stats->vs.rx_drops;
                } while (u64_stats_fetch_retry(&stats->syncp, start));
                result->peer_tq_xdp_xmit_err += peer_tq_xdp_xmit_err;
                result->xdp_tx_err += xdp_tx_err;
                result->xdp_packets += packets;
                result->xdp_bytes += bytes;
                result->rx_drops += drops;
        }
}

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 veth_stats rx;

        tot->tx_dropped = atomic64_read(&priv->dropped);
        dev_fetch_sw_netstats(tot, dev->tstats);

        veth_stats_rx(&rx, dev);
        tot->tx_dropped += rx.xdp_tx_err;
        tot->rx_dropped = rx.rx_drops + rx.peer_tq_xdp_xmit_err;
        tot->rx_bytes += rx.xdp_bytes;
        tot->rx_packets += rx.xdp_packets;

        rcu_read_lock();
        peer = rcu_dereference(priv->peer);
        if (peer) {
                struct rtnl_link_stats64 tot_peer = {};

                dev_fetch_sw_netstats(&tot_peer, peer->tstats);
                tot->rx_bytes += tot_peer.tx_bytes;
                tot->rx_packets += tot_peer.tx_packets;

                veth_stats_rx(&rx, peer);
                tot->tx_dropped += rx.peer_tq_xdp_xmit_err;
                tot->rx_dropped += rx.xdp_tx_err;
                tot->tx_bytes += rx.xdp_bytes;
                tot->tx_packets += rx.xdp_packets;
        }
        rcu_read_unlock();
}

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

static int veth_select_rxq(struct net_device *dev)
{
        return smp_processor_id() % dev->real_num_rx_queues;
}

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

        /* Callers must be under RCU read side. */
        return rcu_dereference(priv->peer);
}

static int veth_xdp_xmit(struct net_device *dev, int n,
                         struct xdp_frame **frames,
                         u32 flags, bool ndo_xmit)
{
        struct veth_priv *rcv_priv, *priv = netdev_priv(dev);
        int i, ret = -ENXIO, nxmit = 0;
        struct net_device *rcv;
        unsigned int max_len;
        struct veth_rq *rq;

        if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
                return -EINVAL;

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

        rcv_priv = netdev_priv(rcv);
        rq = &rcv_priv->rq[veth_select_rxq(rcv)];
        /* The napi pointer is set if NAPI is enabled, which ensures that
         * xdp_ring is initialized on receive side and the peer device is up.
         */
        if (!rcu_access_pointer(rq->napi))
                goto out;

        max_len = rcv->mtu + rcv->hard_header_len + VLAN_HLEN;

        spin_lock(&rq->xdp_ring.producer_lock);
        for (i = 0; i < n; i++) {
                struct xdp_frame *frame = frames[i];
                void *ptr = veth_xdp_to_ptr(frame);

                if (unlikely(xdp_get_frame_len(frame) > max_len ||
                             __ptr_ring_produce(&rq->xdp_ring, ptr)))
                        break;
                nxmit++;
        }
        spin_unlock(&rq->xdp_ring.producer_lock);

        if (flags & XDP_XMIT_FLUSH)
                __veth_xdp_flush(rq);

        ret = nxmit;
        if (ndo_xmit) {
                u64_stats_update_begin(&rq->stats.syncp);
                rq->stats.vs.peer_tq_xdp_xmit += nxmit;
                rq->stats.vs.peer_tq_xdp_xmit_err += n - nxmit;
                u64_stats_update_end(&rq->stats.syncp);
        }

out:
        rcu_read_unlock();

        return ret;
}

static int veth_ndo_xdp_xmit(struct net_device *dev, int n,
                             struct xdp_frame **frames, u32 flags)
{
        int err;

        err = veth_xdp_xmit(dev, n, frames, flags, true);
        if (err < 0) {
                struct veth_priv *priv = netdev_priv(dev);

                atomic64_add(n, &priv->dropped);
        }

        return err;
}

static void veth_xdp_flush_bq(struct veth_rq *rq, struct veth_xdp_tx_bq *bq)
{
        int sent, i, err = 0, drops;

        sent = veth_xdp_xmit(rq->dev, bq->count, bq->q, 0, false);
        if (sent < 0) {
                err = sent;
                sent = 0;
        }

        for (i = sent; unlikely(i < bq->count); i++)
                xdp_return_frame(bq->q[i]);

        drops = bq->count - sent;
        trace_xdp_bulk_tx(rq->dev, sent, drops, err);

        u64_stats_update_begin(&rq->stats.syncp);
        rq->stats.vs.xdp_tx += sent;
        rq->stats.vs.xdp_tx_err += drops;
        u64_stats_update_end(&rq->stats.syncp);

        bq->count = 0;
}

static void veth_xdp_flush(struct veth_rq *rq, struct veth_xdp_tx_bq *bq)
{
        struct veth_priv *rcv_priv, *priv = netdev_priv(rq->dev);
        struct net_device *rcv;
        struct veth_rq *rcv_rq;

        rcu_read_lock();
        veth_xdp_flush_bq(rq, bq);
        rcv = rcu_dereference(priv->peer);
        if (unlikely(!rcv))
                goto out;

        rcv_priv = netdev_priv(rcv);
        rcv_rq = &rcv_priv->rq[veth_select_rxq(rcv)];
        /* xdp_ring is initialized on receive side? */
        if (unlikely(!rcu_access_pointer(rcv_rq->xdp_prog)))
                goto out;

        __veth_xdp_flush(rcv_rq);
out:
        rcu_read_unlock();
}

static int veth_xdp_tx(struct veth_rq *rq, struct xdp_buff *xdp,
                       struct veth_xdp_tx_bq *bq)
{
        struct xdp_frame *frame = xdp_convert_buff_to_frame(xdp);

        if (unlikely(!frame))
                return -EOVERFLOW;

        if (unlikely(bq->count == VETH_XDP_TX_BULK_SIZE))
                veth_xdp_flush_bq(rq, bq);

        bq->q[bq->count++] = frame;

        return 0;
}

static struct xdp_frame *veth_xdp_rcv_one(struct veth_rq *rq,
                                          struct xdp_frame *frame,
                                          struct veth_xdp_tx_bq *bq,
                                          struct veth_stats *stats)
{
        struct xdp_frame orig_frame;
        struct bpf_prog *xdp_prog;

        rcu_read_lock();
        xdp_prog = rcu_dereference(rq->xdp_prog);
        if (likely(xdp_prog)) {
                struct veth_xdp_buff vxbuf;
                struct xdp_buff *xdp = &vxbuf.xdp;
                u32 act;

                xdp_convert_frame_to_buff(frame, xdp);
                xdp->rxq = &rq->xdp_rxq;
                vxbuf.skb = NULL;

                act = bpf_prog_run_xdp(xdp_prog, xdp);

                switch (act) {
                case XDP_PASS:
                        if (xdp_update_frame_from_buff(xdp, frame))
                                goto err_xdp;
                        break;
                case XDP_TX:
                        orig_frame = *frame;
                        xdp->rxq->mem.type = frame->mem_type;
                        if (unlikely(veth_xdp_tx(rq, xdp, bq) < 0)) {
                                trace_xdp_exception(rq->dev, xdp_prog, act);
                                frame = &orig_frame;
                                stats->rx_drops++;
                                goto err_xdp;
                        }
                        stats->xdp_tx++;
                        rcu_read_unlock();
                        goto xdp_xmit;
                case XDP_REDIRECT:
                        orig_frame = *frame;
                        xdp->rxq->mem.type = frame->mem_type;
                        if (xdp_do_redirect(rq->dev, xdp, xdp_prog)) {
                                frame = &orig_frame;
                                stats->rx_drops++;
                                goto err_xdp;
                        }
                        stats->xdp_redirect++;
                        rcu_read_unlock();
                        goto xdp_xmit;
                default:
                        bpf_warn_invalid_xdp_action(rq->dev, xdp_prog, act);
                        fallthrough;
                case XDP_ABORTED:
                        trace_xdp_exception(rq->dev, xdp_prog, act);
                        fallthrough;
                case XDP_DROP:
                        stats->xdp_drops++;
                        goto err_xdp;
                }
        }
        rcu_read_unlock();

        return frame;
err_xdp:
        rcu_read_unlock();
        xdp_return_frame(frame);
xdp_xmit:
        return NULL;
}

/* frames array contains VETH_XDP_BATCH at most */
static void veth_xdp_rcv_bulk_skb(struct veth_rq *rq, void **frames,
                                  int n_xdpf, struct veth_xdp_tx_bq *bq,
                                  struct veth_stats *stats)
{
        void *skbs[VETH_XDP_BATCH];
        int i;

        if (unlikely(!napi_skb_cache_get_bulk(skbs, n_xdpf))) {
                for (i = 0; i < n_xdpf; i++)
                        xdp_return_frame(frames[i]);
                stats->rx_drops += n_xdpf;

                return;
        }

        for (i = 0; i < n_xdpf; i++) {
                struct sk_buff *skb = skbs[i];

                skb = __xdp_build_skb_from_frame(frames[i], skb,
                                                 rq->dev);
                if (!skb) {
                        xdp_return_frame(frames[i]);
                        stats->rx_drops++;
                        continue;
                }
                napi_gro_receive(&rq->xdp_napi, skb);
        }
}

static void veth_xdp_get(struct xdp_buff *xdp)
{
        struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
        int i;

        get_page(virt_to_page(xdp->data));
        if (likely(!xdp_buff_has_frags(xdp)))
                return;

        for (i = 0; i < sinfo->nr_frags; i++)
                __skb_frag_ref(&sinfo->frags[i]);
}

static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq,
                                        struct xdp_buff *xdp,
                                        struct sk_buff **pskb)
{
        struct sk_buff *skb = *pskb;
        u32 frame_sz;

        if (skb_shared(skb) || skb_head_is_locked(skb) ||
            skb_shinfo(skb)->nr_frags ||
            skb_headroom(skb) < XDP_PACKET_HEADROOM) {
                if (skb_pp_cow_data(rq->page_pool, pskb, XDP_PACKET_HEADROOM))
                        goto drop;

                skb = *pskb;
        }

        /* SKB "head" area always have tailroom for skb_shared_info */
        frame_sz = skb_end_pointer(skb) - skb->head;
        frame_sz += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
        xdp_init_buff(xdp, frame_sz, &rq->xdp_rxq);
        xdp_prepare_buff(xdp, skb->head, skb_headroom(skb),
                         skb_headlen(skb), true);

        if (skb_is_nonlinear(skb)) {
                skb_shinfo(skb)->xdp_frags_size = skb->data_len;
                xdp_buff_set_frags_flag(xdp);
        } else {
                xdp_buff_clear_frags_flag(xdp);
        }
        *pskb = skb;

        return 0;
drop:
        consume_skb(skb);
        *pskb = NULL;

        return -ENOMEM;
}

static struct sk_buff *veth_xdp_rcv_skb(struct veth_rq *rq,
                                        struct sk_buff *skb,
                                        struct veth_xdp_tx_bq *bq,
                                        struct veth_stats *stats)
{
        void *orig_data, *orig_data_end;
        struct bpf_prog *xdp_prog;
        struct veth_xdp_buff vxbuf;
        struct xdp_buff *xdp = &vxbuf.xdp;
        u32 act, metalen;
        int off;

        skb_prepare_for_gro(skb);

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

        __skb_push(skb, skb->data - skb_mac_header(skb));
        if (veth_convert_skb_to_xdp_buff(rq, xdp, &skb))
                goto drop;
        vxbuf.skb = skb;

        orig_data = xdp->data;
        orig_data_end = xdp->data_end;

        act = bpf_prog_run_xdp(xdp_prog, xdp);

        switch (act) {
        case XDP_PASS:
                break;
        case XDP_TX:
                veth_xdp_get(xdp);
                consume_skb(skb);
                xdp->rxq->mem = rq->xdp_mem;
                if (unlikely(veth_xdp_tx(rq, xdp, bq) < 0)) {
                        trace_xdp_exception(rq->dev, xdp_prog, act);
                        stats->rx_drops++;
                        goto err_xdp;
                }
                stats->xdp_tx++;
                rcu_read_unlock();
                goto xdp_xmit;
        case XDP_REDIRECT:
                veth_xdp_get(xdp);
                consume_skb(skb);
                xdp->rxq->mem = rq->xdp_mem;
                if (xdp_do_redirect(rq->dev, xdp, xdp_prog)) {
                        stats->rx_drops++;
                        goto err_xdp;
                }
                stats->xdp_redirect++;
                rcu_read_unlock();
                goto xdp_xmit;
        default:
                bpf_warn_invalid_xdp_action(rq->dev, xdp_prog, act);
                fallthrough;
        case XDP_ABORTED:
                trace_xdp_exception(rq->dev, xdp_prog, act);
                fallthrough;
        case XDP_DROP:
                stats->xdp_drops++;
                goto xdp_drop;
        }
        rcu_read_unlock();

        /* check if bpf_xdp_adjust_head was used */
        off = orig_data - xdp->data;
        if (off > 0)
                __skb_push(skb, off);
        else if (off < 0)
                __skb_pull(skb, -off);

        skb_reset_mac_header(skb);

        /* check if bpf_xdp_adjust_tail was used */
        off = xdp->data_end - orig_data_end;
        if (off != 0)
                __skb_put(skb, off); /* positive on grow, negative on shrink */

        /* XDP frag metadata (e.g. nr_frags) are updated in eBPF helpers
         * (e.g. bpf_xdp_adjust_tail), we need to update data_len here.
         */
        if (xdp_buff_has_frags(xdp))
                skb->data_len = skb_shinfo(skb)->xdp_frags_size;
        else
                skb->data_len = 0;

        skb->protocol = eth_type_trans(skb, rq->dev);

        metalen = xdp->data - xdp->data_meta;
        if (metalen)
                skb_metadata_set(skb, metalen);
out:
        return skb;
drop:
        stats->rx_drops++;
xdp_drop:
        rcu_read_unlock();
        kfree_skb(skb);
        return NULL;
err_xdp:
        rcu_read_unlock();
        xdp_return_buff(xdp);
xdp_xmit:
        return NULL;
}

static int veth_xdp_rcv(struct veth_rq *rq, int budget,
                        struct veth_xdp_tx_bq *bq,
                        struct veth_stats *stats)
{
        int i, done = 0, n_xdpf = 0;
        void *xdpf[VETH_XDP_BATCH];

        for (i = 0; i < budget; i++) {
                void *ptr = __ptr_ring_consume(&rq->xdp_ring);

                if (!ptr)
                        break;

                if (veth_is_xdp_frame(ptr)) {
                        /* ndo_xdp_xmit */
                        struct xdp_frame *frame = veth_ptr_to_xdp(ptr);

                        stats->xdp_bytes += xdp_get_frame_len(frame);
                        frame = veth_xdp_rcv_one(rq, frame, bq, stats);
                        if (frame) {
                                /* XDP_PASS */
                                xdpf[n_xdpf++] = frame;
                                if (n_xdpf == VETH_XDP_BATCH) {
                                        veth_xdp_rcv_bulk_skb(rq, xdpf, n_xdpf,
                                                              bq, stats);
                                        n_xdpf = 0;
                                }
                        }
                } else {
                        /* ndo_start_xmit */
                        struct sk_buff *skb = ptr;

                        stats->xdp_bytes += skb->len;
                        skb = veth_xdp_rcv_skb(rq, skb, bq, stats);
                        if (skb) {
                                if (skb_shared(skb) || skb_unclone(skb, GFP_ATOMIC))
                                        netif_receive_skb(skb);
                                else
                                        napi_gro_receive(&rq->xdp_napi, skb);
                        }
                }
                done++;
        }

        if (n_xdpf)
                veth_xdp_rcv_bulk_skb(rq, xdpf, n_xdpf, bq, stats);

        u64_stats_update_begin(&rq->stats.syncp);
        rq->stats.vs.xdp_redirect += stats->xdp_redirect;
        rq->stats.vs.xdp_bytes += stats->xdp_bytes;
        rq->stats.vs.xdp_drops += stats->xdp_drops;
        rq->stats.vs.rx_drops += stats->rx_drops;
        rq->stats.vs.xdp_packets += done;
        u64_stats_update_end(&rq->stats.syncp);

        return done;
}

static int veth_poll(struct napi_struct *napi, int budget)
{
        struct veth_rq *rq =
                container_of(napi, struct veth_rq, xdp_napi);
        struct veth_priv *priv = netdev_priv(rq->dev);
        int queue_idx = rq->xdp_rxq.queue_index;
        struct netdev_queue *peer_txq;
        struct veth_stats stats = {};
        struct net_device *peer_dev;
        struct veth_xdp_tx_bq bq;
        int done;

        bq.count = 0;

        /* NAPI functions as RCU section */
        peer_dev = rcu_dereference_check(priv->peer, rcu_read_lock_bh_held());
        peer_txq = peer_dev ? netdev_get_tx_queue(peer_dev, queue_idx) : NULL;

        xdp_set_return_frame_no_direct();
        done = veth_xdp_rcv(rq, budget, &bq, &stats);

        if (stats.xdp_redirect > 0)
                xdp_do_flush();
        if (stats.xdp_tx > 0)
                veth_xdp_flush(rq, &bq);
        xdp_clear_return_frame_no_direct();

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

        /* Release backpressure per NAPI poll */
        smp_rmb(); /* Paired with netif_tx_stop_queue set_bit */
        if (peer_txq && netif_tx_queue_stopped(peer_txq)) {
                txq_trans_cond_update(peer_txq);
                netif_tx_wake_queue(peer_txq);
        }

        return done;
}

static int veth_create_page_pool(struct veth_rq *rq)
{
        struct page_pool_params pp_params = {
                .order = 0,
                .pool_size = VETH_RING_SIZE,
                .nid = NUMA_NO_NODE,
                .dev = &rq->dev->dev,
        };

        rq->page_pool = page_pool_create(&pp_params);
        if (IS_ERR(rq->page_pool)) {
                int err = PTR_ERR(rq->page_pool);

                rq->page_pool = NULL;
                return err;
        }

        return 0;
}

static int __veth_napi_enable_range(struct net_device *dev, int start, int end)
{
        struct veth_priv *priv = netdev_priv(dev);
        int err, i;

        for (i = start; i < end; i++) {
                err = veth_create_page_pool(&priv->rq[i]);
                if (err)
                        goto err_page_pool;
        }

        for (i = start; i < end; i++) {
                struct veth_rq *rq = &priv->rq[i];

                err = ptr_ring_init(&rq->xdp_ring, VETH_RING_SIZE, GFP_KERNEL);
                if (err)
                        goto err_xdp_ring;
        }

        for (i = start; i < end; i++) {
                struct veth_rq *rq = &priv->rq[i];

                napi_enable(&rq->xdp_napi);
                rcu_assign_pointer(priv->rq[i].napi, &priv->rq[i].xdp_napi);
        }

        return 0;

err_xdp_ring:
        for (i--; i >= start; i--)
                ptr_ring_cleanup(&priv->rq[i].xdp_ring, veth_ptr_free);
        i = end;
err_page_pool:
        for (i--; i >= start; i--) {
                page_pool_destroy(priv->rq[i].page_pool);
                priv->rq[i].page_pool = NULL;
        }

        return err;
}

static int __veth_napi_enable(struct net_device *dev)
{
        return __veth_napi_enable_range(dev, 0, dev->real_num_rx_queues);
}

static void veth_napi_del_range(struct net_device *dev, int start, int end)
{
        struct veth_priv *priv = netdev_priv(dev);
        int i;

        for (i = start; i < end; i++) {
                struct veth_rq *rq = &priv->rq[i];

                rcu_assign_pointer(priv->rq[i].napi, NULL);
                napi_disable(&rq->xdp_napi);
                __netif_napi_del(&rq->xdp_napi);
        }
        synchronize_net();

        for (i = start; i < end; i++) {
                struct veth_rq *rq = &priv->rq[i];

                rq->rx_notify_masked = false;
                ptr_ring_cleanup(&rq->xdp_ring, veth_ptr_free);
        }

        for (i = start; i < end; i++) {
                page_pool_destroy(priv->rq[i].page_pool);
                priv->rq[i].page_pool = NULL;
        }
}

static void veth_napi_del(struct net_device *dev)
{
        veth_napi_del_range(dev, 0, dev->real_num_rx_queues);
}

static bool veth_gro_requested(const struct net_device *dev)
{
        return !!(dev->wanted_features & NETIF_F_GRO);
}

static int veth_enable_xdp_range(struct net_device *dev, int start, int end,
                                 bool napi_already_on)
{
        struct veth_priv *priv = netdev_priv(dev);
        int err, i;

        for (i = start; i < end; i++) {
                struct veth_rq *rq = &priv->rq[i];

                if (!napi_already_on)
                        netif_napi_add(dev, &rq->xdp_napi, veth_poll);
                err = xdp_rxq_info_reg(&rq->xdp_rxq, dev, i, rq->xdp_napi.napi_id);
                if (err < 0)
                        goto err_rxq_reg;

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

                /* Save original mem info as it can be overwritten */
                rq->xdp_mem = rq->xdp_rxq.mem;
        }
        return 0;

err_reg_mem:
        xdp_rxq_info_unreg(&priv->rq[i].xdp_rxq);
err_rxq_reg:
        for (i--; i >= start; i--) {
                struct veth_rq *rq = &priv->rq[i];

                xdp_rxq_info_unreg(&rq->xdp_rxq);
                if (!napi_already_on)
                        netif_napi_del(&rq->xdp_napi);
        }

        return err;
}

static void veth_disable_xdp_range(struct net_device *dev, int start, int end,
                                   bool delete_napi)
{
        struct veth_priv *priv = netdev_priv(dev);
        int i;

        for (i = start; i < end; i++) {
                struct veth_rq *rq = &priv->rq[i];

                rq->xdp_rxq.mem = rq->xdp_mem;
                xdp_rxq_info_unreg(&rq->xdp_rxq);

                if (delete_napi)
                        netif_napi_del(&rq->xdp_napi);
        }
}

static int veth_enable_xdp(struct net_device *dev)
{
        bool napi_already_on = veth_gro_requested(dev) && (dev->flags & IFF_UP);
        struct veth_priv *priv = netdev_priv(dev);
        int err, i;

        if (!xdp_rxq_info_is_reg(&priv->rq[0].xdp_rxq)) {
                err = veth_enable_xdp_range(dev, 0, dev->real_num_rx_queues, napi_already_on);
                if (err)
                        return err;

                if (!napi_already_on) {
                        err = __veth_napi_enable(dev);
                        if (err) {
                                veth_disable_xdp_range(dev, 0, dev->real_num_rx_queues, true);
                                return err;
                        }
                }
        }

        for (i = 0; i < dev->real_num_rx_queues; i++) {
                rcu_assign_pointer(priv->rq[i].xdp_prog, priv->_xdp_prog);
                rcu_assign_pointer(priv->rq[i].napi, &priv->rq[i].xdp_napi);
        }

        return 0;
}

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

        for (i = 0; i < dev->real_num_rx_queues; i++)
                rcu_assign_pointer(priv->rq[i].xdp_prog, NULL);

        if (!netif_running(dev) || !veth_gro_requested(dev))
                veth_napi_del(dev);

        veth_disable_xdp_range(dev, 0, dev->real_num_rx_queues, false);
}

static int veth_napi_enable_range(struct net_device *dev, int start, int end)
{
        struct veth_priv *priv = netdev_priv(dev);
        int err, i;

        for (i = start; i < end; i++) {
                struct veth_rq *rq = &priv->rq[i];

                netif_napi_add(dev, &rq->xdp_napi, veth_poll);
        }

        err = __veth_napi_enable_range(dev, start, end);
        if (err) {
                for (i = start; i < end; i++) {
                        struct veth_rq *rq = &priv->rq[i];

                        netif_napi_del(&rq->xdp_napi);
                }
                return err;
        }
        return err;
}

static int veth_napi_enable(struct net_device *dev)
{
        return veth_napi_enable_range(dev, 0, dev->real_num_rx_queues);
}

static void veth_disable_range_safe(struct net_device *dev, int start, int end)
{
        struct veth_priv *priv = netdev_priv(dev);

        if (start >= end)
                return;

        if (priv->_xdp_prog) {
                veth_napi_del_range(dev, start, end);
                veth_disable_xdp_range(dev, start, end, false);
        } else if (veth_gro_requested(dev)) {
                veth_napi_del_range(dev, start, end);
        }
}

static int veth_enable_range_safe(struct net_device *dev, int start, int end)
{
        struct veth_priv *priv = netdev_priv(dev);
        int err;

        if (start >= end)
                return 0;

        if (priv->_xdp_prog) {
                /* these channels are freshly initialized, napi is not on there even
                 * when GRO is requeste
                 */
                err = veth_enable_xdp_range(dev, start, end, false);
                if (err)
                        return err;

                err = __veth_napi_enable_range(dev, start, end);
                if (err) {
                        /* on error always delete the newly added napis */
                        veth_disable_xdp_range(dev, start, end, true);
                        return err;
                }
        } else if (veth_gro_requested(dev)) {
                return veth_napi_enable_range(dev, start, end);
        }
        return 0;
}

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

        peer = rtnl_dereference(priv->peer);
        if (peer && peer->real_num_tx_queues <= dev->real_num_rx_queues) {
                struct veth_priv *priv_peer = netdev_priv(peer);
                xdp_features_t val = NETDEV_XDP_ACT_BASIC |
                                     NETDEV_XDP_ACT_REDIRECT |
                                     NETDEV_XDP_ACT_RX_SG;

                if (priv_peer->_xdp_prog || veth_gro_requested(peer))
                        val |= NETDEV_XDP_ACT_NDO_XMIT |
                               NETDEV_XDP_ACT_NDO_XMIT_SG;
                xdp_set_features_flag(dev, val);
        } else {
                xdp_clear_features_flag(dev);
        }
}

static int veth_set_channels(struct net_device *dev,
                             struct ethtool_channels *ch)
{
        struct veth_priv *priv = netdev_priv(dev);
        unsigned int old_rx_count, new_rx_count;
        struct veth_priv *peer_priv;
        struct net_device *peer;
        int err;

        /* sanity check. Upper bounds are already enforced by the caller */
        if (!ch->rx_count || !ch->tx_count)
                return -EINVAL;

        /* avoid braking XDP, if that is enabled */
        peer = rtnl_dereference(priv->peer);
        peer_priv = peer ? netdev_priv(peer) : NULL;
        if (priv->_xdp_prog && peer && ch->rx_count < peer->real_num_tx_queues)
                return -EINVAL;

        if (peer && peer_priv && peer_priv->_xdp_prog && ch->tx_count > peer->real_num_rx_queues)
                return -EINVAL;

        old_rx_count = dev->real_num_rx_queues;
        new_rx_count = ch->rx_count;
        if (netif_running(dev)) {
                /* turn device off */
                netif_carrier_off(dev);
                if (peer)
                        netif_carrier_off(peer);

                /* try to allocate new resources, as needed*/
                err = veth_enable_range_safe(dev, old_rx_count, new_rx_count);
                if (err)
                        goto out;
        }

        err = netif_set_real_num_rx_queues(dev, ch->rx_count);
        if (err)
                goto revert;

        err = netif_set_real_num_tx_queues(dev, ch->tx_count);
        if (err) {
                int err2 = netif_set_real_num_rx_queues(dev, old_rx_count);

                /* this error condition could happen only if rx and tx change
                 * in opposite directions (e.g. tx nr raises, rx nr decreases)
                 * and we can't do anything to fully restore the original
                 * status
                 */
                if (err2)
                        pr_warn("Can't restore rx queues config %d -> %d %d",
                                new_rx_count, old_rx_count, err2);
                else
                        goto revert;
        }

out:
        if (netif_running(dev)) {
                /* note that we need to swap the arguments WRT the enable part
                 * to identify the range we have to disable
                 */
                veth_disable_range_safe(dev, new_rx_count, old_rx_count);
                netif_carrier_on(dev);
                if (peer)
                        netif_carrier_on(peer);
        }

        /* update XDP supported features */
        veth_set_xdp_features(dev);
        if (peer)
                veth_set_xdp_features(peer);

        return err;

revert:
        new_rx_count = old_rx_count;
        old_rx_count = ch->rx_count;
        goto out;
}

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;
        } else if (veth_gro_requested(dev)) {
                err = veth_napi_enable(dev);
                if (err)
                        return err;
        }

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

        veth_set_xdp_features(dev);

        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);
        else if (veth_gro_requested(dev))
                veth_napi_del(dev);

        return 0;
}

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

static int veth_alloc_queues(struct net_device *dev)
{
        struct veth_priv *priv = netdev_priv(dev);
        int i;

        priv->rq = kvzalloc_objs(*priv->rq, dev->num_rx_queues,
                                 GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
        if (!priv->rq)
                return -ENOMEM;

        for (i = 0; i < dev->num_rx_queues; i++) {
                priv->rq[i].dev = dev;
                u64_stats_init(&priv->rq[i].stats.syncp);
        }

        return 0;
}

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

        kvfree(priv->rq);
}

static int veth_dev_init(struct net_device *dev)
{
        netdev_lockdep_set_classes(dev);
        return veth_alloc_queues(dev);
}

static void veth_dev_free(struct net_device *dev)
{
        veth_free_queues(dev);
}

#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 ? READ_ONCE(peer->ifindex) : 0;
        rcu_read_unlock();

        return iflink;
}

static netdev_features_t veth_fix_features(struct net_device *dev,
                                           netdev_features_t features)
{
        struct veth_priv *priv = netdev_priv(dev);
        struct net_device *peer;

        peer = rtnl_dereference(priv->peer);
        if (peer) {
                struct veth_priv *peer_priv = netdev_priv(peer);

                if (peer_priv->_xdp_prog)
                        features &= ~NETIF_F_GSO_SOFTWARE;
        }

        return features;
}

static int veth_set_features(struct net_device *dev,
                             netdev_features_t features)
{
        netdev_features_t changed = features ^ dev->features;
        struct veth_priv *priv = netdev_priv(dev);
        struct net_device *peer;
        int err;

        if (!(changed & NETIF_F_GRO) || !(dev->flags & IFF_UP) || priv->_xdp_prog)
                return 0;

        peer = rtnl_dereference(priv->peer);
        if (features & NETIF_F_GRO) {
                err = veth_napi_enable(dev);
                if (err)
                        return err;

                if (peer)
                        xdp_features_set_redirect_target(peer, true);
        } else {
                if (peer)
                        xdp_features_clear_redirect_target(peer);
                veth_napi_del(dev);
        }
        return 0;
}

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;
        unsigned int max_mtu;
        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;
                }

                max_mtu = SKB_WITH_OVERHEAD(PAGE_SIZE - VETH_XDP_HEADROOM) -
                          peer->hard_header_len;
                /* Allow increasing the max_mtu if the program supports
                 * XDP fragments.
                 */
                if (prog->aux->xdp_has_frags)
                        max_mtu += PAGE_SIZE * MAX_SKB_FRAGS;

                if (peer->mtu > max_mtu) {
                        NL_SET_ERR_MSG_MOD(extack, "Peer MTU is too large to set XDP");
                        err = -ERANGE;
                        goto err;
                }

                if (dev->real_num_rx_queues < peer->real_num_tx_queues) {
                        NL_SET_ERR_MSG_MOD(extack, "XDP expects number of rx queues not less than peer tx queues");
                        err = -ENOSPC;
                        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) {
                        peer->hw_features &= ~NETIF_F_GSO_SOFTWARE;
                        peer->max_mtu = max_mtu;
                }

                xdp_features_set_redirect_target(peer, true);
        }

        if (old_prog) {
                if (!prog) {
                        if (peer && !veth_gro_requested(dev))
                                xdp_features_clear_redirect_target(peer);

                        if (dev->flags & IFF_UP)
                                veth_disable_xdp(dev);

                        if (peer) {
                                peer->hw_features |= NETIF_F_GSO_SOFTWARE;
                                peer->max_mtu = ETH_MAX_MTU;
                        }
                }
                bpf_prog_put(old_prog);
        }

        if ((!!old_prog ^ !!prog) && peer)
                netdev_update_features(peer);

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

        return err;
}

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);
        default:
                return -EINVAL;
        }
}

static int veth_xdp_rx_timestamp(const struct xdp_md *ctx, u64 *timestamp)
{
        struct veth_xdp_buff *_ctx = (void *)ctx;

        if (!_ctx->skb)
                return -ENODATA;

        *timestamp = skb_hwtstamps(_ctx->skb)->hwtstamp;
        return 0;
}

static int veth_xdp_rx_hash(const struct xdp_md *ctx, u32 *hash,
                            enum xdp_rss_hash_type *rss_type)
{
        struct veth_xdp_buff *_ctx = (void *)ctx;
        struct sk_buff *skb = _ctx->skb;

        if (!skb)
                return -ENODATA;

        *hash = skb_get_hash(skb);
        *rss_type = skb->l4_hash ? XDP_RSS_TYPE_L4_ANY : XDP_RSS_TYPE_NONE;

        return 0;
}

static int veth_xdp_rx_vlan_tag(const struct xdp_md *ctx, __be16 *vlan_proto,
                                u16 *vlan_tci)
{
        const struct veth_xdp_buff *_ctx = (void *)ctx;
        const struct sk_buff *skb = _ctx->skb;
        int err;

        if (!skb)
                return -ENODATA;

        err = __vlan_hwaccel_get_tag(skb, vlan_tci);
        if (err)
                return err;

        *vlan_proto = skb->vlan_proto;
        return err;
}

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_fix_features       = veth_fix_features,
        .ndo_set_features       = veth_set_features,
        .ndo_features_check     = passthru_features_check,
        .ndo_set_rx_headroom    = veth_set_rx_headroom,
        .ndo_bpf                = veth_xdp,
        .ndo_xdp_xmit           = veth_ndo_xdp_xmit,
        .ndo_get_peer_dev       = veth_peer_dev,
};

static const struct xdp_metadata_ops veth_xdp_metadata_ops = {
        .xmo_rx_timestamp               = veth_xdp_rx_timestamp,
        .xmo_rx_hash                    = veth_xdp_rx_hash,
        .xmo_rx_vlan_tag                = veth_xdp_rx_vlan_tag,
};

#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->priv_flags |= IFF_DISABLE_NETPOLL;
        dev->lltx = true;

        dev->netdev_ops = &veth_netdev_ops;
        dev->xdp_metadata_ops = &veth_xdp_metadata_ops;
        dev->ethtool_ops = &veth_ethtool_ops;
        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->pcpu_stat_type = NETDEV_PCPU_STAT_TSTATS;
        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;
        netif_set_tso_max_size(dev, GSO_MAX_SIZE);
}

/*
 * 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 void veth_disable_gro(struct net_device *dev)
{
        dev->features &= ~NETIF_F_GRO;
        dev->wanted_features &= ~NETIF_F_GRO;
        netdev_update_features(dev);
}

static int veth_init_queues(struct net_device *dev, struct nlattr *tb[])
{
        int err;

        if (!tb[IFLA_NUM_TX_QUEUES] && dev->num_tx_queues > 1) {
                err = netif_set_real_num_tx_queues(dev, 1);
                if (err)
                        return err;
        }
        if (!tb[IFLA_NUM_RX_QUEUES] && dev->num_rx_queues > 1) {
                err = netif_set_real_num_rx_queues(dev, 1);
                if (err)
                        return err;
        }
        return 0;
}

static int veth_newlink(struct net_device *dev,
                        struct rtnl_newlink_params *params,
                        struct netlink_ext_ack *extack)
{
        struct net *peer_net = rtnl_newlink_peer_net(params);
        struct nlattr **data = params->data;
        struct nlattr **tb = params->tb;
        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;

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

                ifmp = nla_data(nla_peer);
                rtnl_nla_parse_ifinfomsg(peer_tb, nla_peer, extack);
                tbp = peer_tb;
        } else {
                ifmp = NULL;
                tbp = tb;
        }

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

        peer = rtnl_create_link(peer_net, ifname, name_assign_type,
                                &veth_link_ops, tbp, extack);
        if (IS_ERR(peer))
                return PTR_ERR(peer);

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

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

        netif_inherit_tso_max(peer, dev);

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

        /* keep GRO disabled by default to be consistent with the established
         * veth behavior
         */
        veth_disable_gro(peer);
        netif_carrier_off(peer);

        err = rtnl_configure_link(peer, ifmp, 0, NULL);
        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_strscpy(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);
        err = veth_init_queues(dev, tb);
        if (err)
                goto err_queues;

        priv = netdev_priv(peer);
        rcu_assign_pointer(priv->peer, dev);
        err = veth_init_queues(peer, tb);
        if (err)
                goto err_queues;

        veth_disable_gro(dev);
        /* update XDP supported features */
        veth_set_xdp_features(dev);
        veth_set_xdp_features(peer);

        return 0;

err_queues:
        unregister_netdevice(dev);
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 unsigned int veth_get_num_queues(void)
{
        /* enforce the same queue limit as rtnl_create_link */
        int queues = num_possible_cpus();

        if (queues > 4096)
                queues = 4096;
        return queues;
}

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,
        .peer_type      = VETH_INFO_PEER,
        .maxtype        = VETH_INFO_MAX,
        .get_link_net   = veth_get_link_net,
        .get_num_tx_queues      = veth_get_num_queues,
        .get_num_rx_queues      = veth_get_num_queues,
};

/*
 * 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);