riscv: Use IPIs for remote cache/TLB flushes by default

[linux.git] / kernel / bpf / devmap.c

// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2017 Covalent IO, Inc. http://covalent.io
 */

/* Devmaps primary use is as a backend map for XDP BPF helper call
 * bpf_redirect_map(). Because XDP is mostly concerned with performance we
 * spent some effort to ensure the datapath with redirect maps does not use
 * any locking. This is a quick note on the details.
 *
 * We have three possible paths to get into the devmap control plane bpf
 * syscalls, bpf programs, and driver side xmit/flush operations. A bpf syscall
 * will invoke an update, delete, or lookup operation. To ensure updates and
 * deletes appear atomic from the datapath side xchg() is used to modify the
 * netdev_map array. Then because the datapath does a lookup into the netdev_map
 * array (read-only) from an RCU critical section we use call_rcu() to wait for
 * an rcu grace period before free'ing the old data structures. This ensures the
 * datapath always has a valid copy. However, the datapath does a "flush"
 * operation that pushes any pending packets in the driver outside the RCU
 * critical section. Each bpf_dtab_netdev tracks these pending operations using
 * a per-cpu flush list. The bpf_dtab_netdev object will not be destroyed  until
 * this list is empty, indicating outstanding flush operations have completed.
 *
 * BPF syscalls may race with BPF program calls on any of the update, delete
 * or lookup operations. As noted above the xchg() operation also keep the
 * netdev_map consistent in this case. From the devmap side BPF programs
 * calling into these operations are the same as multiple user space threads
 * making system calls.
 *
 * Finally, any of the above may race with a netdev_unregister notifier. The
 * unregister notifier must search for net devices in the map structure that
 * contain a reference to the net device and remove them. This is a two step
 * process (a) dereference the bpf_dtab_netdev object in netdev_map and (b)
 * check to see if the ifindex is the same as the net_device being removed.
 * When removing the dev a cmpxchg() is used to ensure the correct dev is
 * removed, in the case of a concurrent update or delete operation it is
 * possible that the initially referenced dev is no longer in the map. As the
 * notifier hook walks the map we know that new dev references can not be
 * added by the user because core infrastructure ensures dev_get_by_index()
 * calls will fail at this point.
 *
 * The devmap_hash type is a map type which interprets keys as ifindexes and
 * indexes these using a hashmap. This allows maps that use ifindex as key to be
 * densely packed instead of having holes in the lookup array for unused
 * ifindexes. The setup and packet enqueue/send code is shared between the two
 * types of devmap; only the lookup and insertion is different.
 */
#include <linux/bpf.h>
#include <net/xdp.h>
#include <linux/filter.h>
#include <trace/events/xdp.h>
#include <linux/btf_ids.h>

#define DEV_CREATE_FLAG_MASK \
        (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)

struct xdp_dev_bulk_queue {
        struct xdp_frame *q[DEV_MAP_BULK_SIZE];
        struct list_head flush_node;
        struct net_device *dev;
        struct net_device *dev_rx;
        struct bpf_prog *xdp_prog;
        unsigned int count;
};

struct bpf_dtab_netdev {
        struct net_device *dev; /* must be first member, due to tracepoint */
        struct hlist_node index_hlist;
        struct bpf_prog *xdp_prog;
        struct rcu_head rcu;
        unsigned int idx;
        struct bpf_devmap_val val;
};

struct bpf_dtab {
        struct bpf_map map;
        struct bpf_dtab_netdev __rcu **netdev_map; /* DEVMAP type only */
        struct list_head list;

        /* these are only used for DEVMAP_HASH type maps */
        struct hlist_head *dev_index_head;
        spinlock_t index_lock;
        unsigned int items;
        u32 n_buckets;
};

static DEFINE_PER_CPU(struct list_head, dev_flush_list);
static DEFINE_SPINLOCK(dev_map_lock);
static LIST_HEAD(dev_map_list);

static struct hlist_head *dev_map_create_hash(unsigned int entries,
                                              int numa_node)
{
        int i;
        struct hlist_head *hash;

        hash = bpf_map_area_alloc((u64) entries * sizeof(*hash), numa_node);
        if (hash != NULL)
                for (i = 0; i < entries; i++)
                        INIT_HLIST_HEAD(&hash[i]);

        return hash;
}

static inline struct hlist_head *dev_map_index_hash(struct bpf_dtab *dtab,
                                                    int idx)
{
        return &dtab->dev_index_head[idx & (dtab->n_buckets - 1)];
}

static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
{
        u32 valsize = attr->value_size;

        /* check sanity of attributes. 2 value sizes supported:
         * 4 bytes: ifindex
         * 8 bytes: ifindex + prog fd
         */
        if (attr->max_entries == 0 || attr->key_size != 4 ||
            (valsize != offsetofend(struct bpf_devmap_val, ifindex) &&
             valsize != offsetofend(struct bpf_devmap_val, bpf_prog.fd)) ||
            attr->map_flags & ~DEV_CREATE_FLAG_MASK)
                return -EINVAL;

        /* Lookup returns a pointer straight to dev->ifindex, so make sure the
         * verifier prevents writes from the BPF side
         */
        attr->map_flags |= BPF_F_RDONLY_PROG;


        bpf_map_init_from_attr(&dtab->map, attr);

        if (attr->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
                /* hash table size must be power of 2; roundup_pow_of_two() can
                 * overflow into UB on 32-bit arches, so check that first
                 */
                if (dtab->map.max_entries > 1UL << 31)
                        return -EINVAL;

                dtab->n_buckets = roundup_pow_of_two(dtab->map.max_entries);

                dtab->dev_index_head = dev_map_create_hash(dtab->n_buckets,
                                                           dtab->map.numa_node);
                if (!dtab->dev_index_head)
                        return -ENOMEM;

                spin_lock_init(&dtab->index_lock);
        } else {
                dtab->netdev_map = bpf_map_area_alloc((u64) dtab->map.max_entries *
                                                      sizeof(struct bpf_dtab_netdev *),
                                                      dtab->map.numa_node);
                if (!dtab->netdev_map)
                        return -ENOMEM;
        }

        return 0;
}

static struct bpf_map *dev_map_alloc(union bpf_attr *attr)
{
        struct bpf_dtab *dtab;
        int err;

        dtab = bpf_map_area_alloc(sizeof(*dtab), NUMA_NO_NODE);
        if (!dtab)
                return ERR_PTR(-ENOMEM);

        err = dev_map_init_map(dtab, attr);
        if (err) {
                bpf_map_area_free(dtab);
                return ERR_PTR(err);
        }

        spin_lock(&dev_map_lock);
        list_add_tail_rcu(&dtab->list, &dev_map_list);
        spin_unlock(&dev_map_lock);

        return &dtab->map;
}

static void dev_map_free(struct bpf_map *map)
{
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        int i;

        /* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
         * so the programs (can be more than one that used this map) were
         * disconnected from events. The following synchronize_rcu() guarantees
         * both rcu read critical sections complete and waits for
         * preempt-disable regions (NAPI being the relevant context here) so we
         * are certain there will be no further reads against the netdev_map and
         * all flush operations are complete. Flush operations can only be done
         * from NAPI context for this reason.
         */

        spin_lock(&dev_map_lock);
        list_del_rcu(&dtab->list);
        spin_unlock(&dev_map_lock);

        bpf_clear_redirect_map(map);
        synchronize_rcu();

        /* Make sure prior __dev_map_entry_free() have completed. */
        rcu_barrier();

        if (dtab->map.map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
                for (i = 0; i < dtab->n_buckets; i++) {
                        struct bpf_dtab_netdev *dev;
                        struct hlist_head *head;
                        struct hlist_node *next;

                        head = dev_map_index_hash(dtab, i);

                        hlist_for_each_entry_safe(dev, next, head, index_hlist) {
                                hlist_del_rcu(&dev->index_hlist);
                                if (dev->xdp_prog)
                                        bpf_prog_put(dev->xdp_prog);
                                dev_put(dev->dev);
                                kfree(dev);
                        }
                }

                bpf_map_area_free(dtab->dev_index_head);
        } else {
                for (i = 0; i < dtab->map.max_entries; i++) {
                        struct bpf_dtab_netdev *dev;

                        dev = rcu_dereference_raw(dtab->netdev_map[i]);
                        if (!dev)
                                continue;

                        if (dev->xdp_prog)
                                bpf_prog_put(dev->xdp_prog);
                        dev_put(dev->dev);
                        kfree(dev);
                }

                bpf_map_area_free(dtab->netdev_map);
        }

        bpf_map_area_free(dtab);
}

static int dev_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
{
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        u32 index = key ? *(u32 *)key : U32_MAX;
        u32 *next = next_key;

        if (index >= dtab->map.max_entries) {
                *next = 0;
                return 0;
        }

        if (index == dtab->map.max_entries - 1)
                return -ENOENT;
        *next = index + 1;
        return 0;
}

/* Elements are kept alive by RCU; either by rcu_read_lock() (from syscall) or
 * by local_bh_disable() (from XDP calls inside NAPI). The
 * rcu_read_lock_bh_held() below makes lockdep accept both.
 */
static void *__dev_map_hash_lookup_elem(struct bpf_map *map, u32 key)
{
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        struct hlist_head *head = dev_map_index_hash(dtab, key);
        struct bpf_dtab_netdev *dev;

        hlist_for_each_entry_rcu(dev, head, index_hlist,
                                 lockdep_is_held(&dtab->index_lock))
                if (dev->idx == key)
                        return dev;

        return NULL;
}

static int dev_map_hash_get_next_key(struct bpf_map *map, void *key,
                                    void *next_key)
{
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        u32 idx, *next = next_key;
        struct bpf_dtab_netdev *dev, *next_dev;
        struct hlist_head *head;
        int i = 0;

        if (!key)
                goto find_first;

        idx = *(u32 *)key;

        dev = __dev_map_hash_lookup_elem(map, idx);
        if (!dev)
                goto find_first;

        next_dev = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(&dev->index_hlist)),
                                    struct bpf_dtab_netdev, index_hlist);

        if (next_dev) {
                *next = next_dev->idx;
                return 0;
        }

        i = idx & (dtab->n_buckets - 1);
        i++;

 find_first:
        for (; i < dtab->n_buckets; i++) {
                head = dev_map_index_hash(dtab, i);

                next_dev = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),
                                            struct bpf_dtab_netdev,
                                            index_hlist);
                if (next_dev) {
                        *next = next_dev->idx;
                        return 0;
                }
        }

        return -ENOENT;
}

static int dev_map_bpf_prog_run(struct bpf_prog *xdp_prog,
                                struct xdp_frame **frames, int n,
                                struct net_device *dev)
{
        struct xdp_txq_info txq = { .dev = dev };
        struct xdp_buff xdp;
        int i, nframes = 0;

        for (i = 0; i < n; i++) {
                struct xdp_frame *xdpf = frames[i];
                u32 act;
                int err;

                xdp_convert_frame_to_buff(xdpf, &xdp);
                xdp.txq = &txq;

                act = bpf_prog_run_xdp(xdp_prog, &xdp);
                switch (act) {
                case XDP_PASS:
                        err = xdp_update_frame_from_buff(&xdp, xdpf);
                        if (unlikely(err < 0))
                                xdp_return_frame_rx_napi(xdpf);
                        else
                                frames[nframes++] = xdpf;
                        break;
                default:
                        bpf_warn_invalid_xdp_action(NULL, xdp_prog, act);
                        fallthrough;
                case XDP_ABORTED:
                        trace_xdp_exception(dev, xdp_prog, act);
                        fallthrough;
                case XDP_DROP:
                        xdp_return_frame_rx_napi(xdpf);
                        break;
                }
        }
        return nframes; /* sent frames count */
}

static void bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags)
{
        struct net_device *dev = bq->dev;
        unsigned int cnt = bq->count;
        int sent = 0, err = 0;
        int to_send = cnt;
        int i;

        if (unlikely(!cnt))
                return;

        for (i = 0; i < cnt; i++) {
                struct xdp_frame *xdpf = bq->q[i];

                prefetch(xdpf);
        }

        if (bq->xdp_prog) {
                to_send = dev_map_bpf_prog_run(bq->xdp_prog, bq->q, cnt, dev);
                if (!to_send)
                        goto out;
        }

        sent = dev->netdev_ops->ndo_xdp_xmit(dev, to_send, bq->q, flags);
        if (sent < 0) {
                /* If ndo_xdp_xmit fails with an errno, no frames have
                 * been xmit'ed.
                 */
                err = sent;
                sent = 0;
        }

        /* If not all frames have been transmitted, it is our
         * responsibility to free them
         */
        for (i = sent; unlikely(i < to_send); i++)
                xdp_return_frame_rx_napi(bq->q[i]);

out:
        bq->count = 0;
        trace_xdp_devmap_xmit(bq->dev_rx, dev, sent, cnt - sent, err);
}

/* __dev_flush is called from xdp_do_flush() which _must_ be signalled from the
 * driver before returning from its napi->poll() routine. See the comment above
 * xdp_do_flush() in filter.c.
 */
void __dev_flush(void)
{
        struct list_head *flush_list = this_cpu_ptr(&dev_flush_list);
        struct xdp_dev_bulk_queue *bq, *tmp;

        list_for_each_entry_safe(bq, tmp, flush_list, flush_node) {
                bq_xmit_all(bq, XDP_XMIT_FLUSH);
                bq->dev_rx = NULL;
                bq->xdp_prog = NULL;
                __list_del_clearprev(&bq->flush_node);
        }
}

#ifdef CONFIG_DEBUG_NET
bool dev_check_flush(void)
{
        if (list_empty(this_cpu_ptr(&dev_flush_list)))
                return false;
        __dev_flush();
        return true;
}
#endif

/* Elements are kept alive by RCU; either by rcu_read_lock() (from syscall) or
 * by local_bh_disable() (from XDP calls inside NAPI). The
 * rcu_read_lock_bh_held() below makes lockdep accept both.
 */
static void *__dev_map_lookup_elem(struct bpf_map *map, u32 key)
{
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        struct bpf_dtab_netdev *obj;

        if (key >= map->max_entries)
                return NULL;

        obj = rcu_dereference_check(dtab->netdev_map[key],
                                    rcu_read_lock_bh_held());
        return obj;
}

/* Runs in NAPI, i.e., softirq under local_bh_disable(). Thus, safe percpu
 * variable access, and map elements stick around. See comment above
 * xdp_do_flush() in filter.c.
 */
static void bq_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
                       struct net_device *dev_rx, struct bpf_prog *xdp_prog)
{
        struct list_head *flush_list = this_cpu_ptr(&dev_flush_list);
        struct xdp_dev_bulk_queue *bq = this_cpu_ptr(dev->xdp_bulkq);

        if (unlikely(bq->count == DEV_MAP_BULK_SIZE))
                bq_xmit_all(bq, 0);

        /* Ingress dev_rx will be the same for all xdp_frame's in
         * bulk_queue, because bq stored per-CPU and must be flushed
         * from net_device drivers NAPI func end.
         *
         * Do the same with xdp_prog and flush_list since these fields
         * are only ever modified together.
         */
        if (!bq->dev_rx) {
                bq->dev_rx = dev_rx;
                bq->xdp_prog = xdp_prog;
                list_add(&bq->flush_node, flush_list);
        }

        bq->q[bq->count++] = xdpf;
}

static inline int __xdp_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
                                struct net_device *dev_rx,
                                struct bpf_prog *xdp_prog)
{
        int err;

        if (!(dev->xdp_features & NETDEV_XDP_ACT_NDO_XMIT))
                return -EOPNOTSUPP;

        if (unlikely(!(dev->xdp_features & NETDEV_XDP_ACT_NDO_XMIT_SG) &&
                     xdp_frame_has_frags(xdpf)))
                return -EOPNOTSUPP;

        err = xdp_ok_fwd_dev(dev, xdp_get_frame_len(xdpf));
        if (unlikely(err))
                return err;

        bq_enqueue(dev, xdpf, dev_rx, xdp_prog);
        return 0;
}

static u32 dev_map_bpf_prog_run_skb(struct sk_buff *skb, struct bpf_dtab_netdev *dst)
{
        struct xdp_txq_info txq = { .dev = dst->dev };
        struct xdp_buff xdp;
        u32 act;

        if (!dst->xdp_prog)
                return XDP_PASS;

        __skb_pull(skb, skb->mac_len);
        xdp.txq = &txq;

        act = bpf_prog_run_generic_xdp(skb, &xdp, dst->xdp_prog);
        switch (act) {
        case XDP_PASS:
                __skb_push(skb, skb->mac_len);
                break;
        default:
                bpf_warn_invalid_xdp_action(NULL, dst->xdp_prog, act);
                fallthrough;
        case XDP_ABORTED:
                trace_xdp_exception(dst->dev, dst->xdp_prog, act);
                fallthrough;
        case XDP_DROP:
                kfree_skb(skb);
                break;
        }

        return act;
}

int dev_xdp_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
                    struct net_device *dev_rx)
{
        return __xdp_enqueue(dev, xdpf, dev_rx, NULL);
}

int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_frame *xdpf,
                    struct net_device *dev_rx)
{
        struct net_device *dev = dst->dev;

        return __xdp_enqueue(dev, xdpf, dev_rx, dst->xdp_prog);
}

static bool is_valid_dst(struct bpf_dtab_netdev *obj, struct xdp_frame *xdpf)
{
        if (!obj)
                return false;

        if (!(obj->dev->xdp_features & NETDEV_XDP_ACT_NDO_XMIT))
                return false;

        if (unlikely(!(obj->dev->xdp_features & NETDEV_XDP_ACT_NDO_XMIT_SG) &&
                     xdp_frame_has_frags(xdpf)))
                return false;

        if (xdp_ok_fwd_dev(obj->dev, xdp_get_frame_len(xdpf)))
                return false;

        return true;
}

static int dev_map_enqueue_clone(struct bpf_dtab_netdev *obj,
                                 struct net_device *dev_rx,
                                 struct xdp_frame *xdpf)
{
        struct xdp_frame *nxdpf;

        nxdpf = xdpf_clone(xdpf);
        if (!nxdpf)
                return -ENOMEM;

        bq_enqueue(obj->dev, nxdpf, dev_rx, obj->xdp_prog);

        return 0;
}

static inline bool is_ifindex_excluded(int *excluded, int num_excluded, int ifindex)
{
        while (num_excluded--) {
                if (ifindex == excluded[num_excluded])
                        return true;
        }
        return false;
}

/* Get ifindex of each upper device. 'indexes' must be able to hold at
 * least MAX_NEST_DEV elements.
 * Returns the number of ifindexes added.
 */
static int get_upper_ifindexes(struct net_device *dev, int *indexes)
{
        struct net_device *upper;
        struct list_head *iter;
        int n = 0;

        netdev_for_each_upper_dev_rcu(dev, upper, iter) {
                indexes[n++] = upper->ifindex;
        }
        return n;
}

int dev_map_enqueue_multi(struct xdp_frame *xdpf, struct net_device *dev_rx,
                          struct bpf_map *map, bool exclude_ingress)
{
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        struct bpf_dtab_netdev *dst, *last_dst = NULL;
        int excluded_devices[1+MAX_NEST_DEV];
        struct hlist_head *head;
        int num_excluded = 0;
        unsigned int i;
        int err;

        if (exclude_ingress) {
                num_excluded = get_upper_ifindexes(dev_rx, excluded_devices);
                excluded_devices[num_excluded++] = dev_rx->ifindex;
        }

        if (map->map_type == BPF_MAP_TYPE_DEVMAP) {
                for (i = 0; i < map->max_entries; i++) {
                        dst = rcu_dereference_check(dtab->netdev_map[i],
                                                    rcu_read_lock_bh_held());
                        if (!is_valid_dst(dst, xdpf))
                                continue;

                        if (is_ifindex_excluded(excluded_devices, num_excluded, dst->dev->ifindex))
                                continue;

                        /* we only need n-1 clones; last_dst enqueued below */
                        if (!last_dst) {
                                last_dst = dst;
                                continue;
                        }

                        err = dev_map_enqueue_clone(last_dst, dev_rx, xdpf);
                        if (err)
                                return err;

                        last_dst = dst;
                }
        } else { /* BPF_MAP_TYPE_DEVMAP_HASH */
                for (i = 0; i < dtab->n_buckets; i++) {
                        head = dev_map_index_hash(dtab, i);
                        hlist_for_each_entry_rcu(dst, head, index_hlist,
                                                 lockdep_is_held(&dtab->index_lock)) {
                                if (!is_valid_dst(dst, xdpf))
                                        continue;

                                if (is_ifindex_excluded(excluded_devices, num_excluded,
                                                        dst->dev->ifindex))
                                        continue;

                                /* we only need n-1 clones; last_dst enqueued below */
                                if (!last_dst) {
                                        last_dst = dst;
                                        continue;
                                }

                                err = dev_map_enqueue_clone(last_dst, dev_rx, xdpf);
                                if (err)
                                        return err;

                                last_dst = dst;
                        }
                }
        }

        /* consume the last copy of the frame */
        if (last_dst)
                bq_enqueue(last_dst->dev, xdpf, dev_rx, last_dst->xdp_prog);
        else
                xdp_return_frame_rx_napi(xdpf); /* dtab is empty */

        return 0;
}

int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
                             struct bpf_prog *xdp_prog)
{
        int err;

        err = xdp_ok_fwd_dev(dst->dev, skb->len);
        if (unlikely(err))
                return err;

        /* Redirect has already succeeded semantically at this point, so we just
         * return 0 even if packet is dropped. Helper below takes care of
         * freeing skb.
         */
        if (dev_map_bpf_prog_run_skb(skb, dst) != XDP_PASS)
                return 0;

        skb->dev = dst->dev;
        generic_xdp_tx(skb, xdp_prog);

        return 0;
}

static int dev_map_redirect_clone(struct bpf_dtab_netdev *dst,
                                  struct sk_buff *skb,
                                  struct bpf_prog *xdp_prog)
{
        struct sk_buff *nskb;
        int err;

        nskb = skb_clone(skb, GFP_ATOMIC);
        if (!nskb)
                return -ENOMEM;

        err = dev_map_generic_redirect(dst, nskb, xdp_prog);
        if (unlikely(err)) {
                consume_skb(nskb);
                return err;
        }

        return 0;
}

int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb,
                           struct bpf_prog *xdp_prog, struct bpf_map *map,
                           bool exclude_ingress)
{
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        struct bpf_dtab_netdev *dst, *last_dst = NULL;
        int excluded_devices[1+MAX_NEST_DEV];
        struct hlist_head *head;
        struct hlist_node *next;
        int num_excluded = 0;
        unsigned int i;
        int err;

        if (exclude_ingress) {
                num_excluded = get_upper_ifindexes(dev, excluded_devices);
                excluded_devices[num_excluded++] = dev->ifindex;
        }

        if (map->map_type == BPF_MAP_TYPE_DEVMAP) {
                for (i = 0; i < map->max_entries; i++) {
                        dst = rcu_dereference_check(dtab->netdev_map[i],
                                                    rcu_read_lock_bh_held());
                        if (!dst)
                                continue;

                        if (is_ifindex_excluded(excluded_devices, num_excluded, dst->dev->ifindex))
                                continue;

                        /* we only need n-1 clones; last_dst enqueued below */
                        if (!last_dst) {
                                last_dst = dst;
                                continue;
                        }

                        err = dev_map_redirect_clone(last_dst, skb, xdp_prog);
                        if (err)
                                return err;

                        last_dst = dst;

                }
        } else { /* BPF_MAP_TYPE_DEVMAP_HASH */
                for (i = 0; i < dtab->n_buckets; i++) {
                        head = dev_map_index_hash(dtab, i);
                        hlist_for_each_entry_safe(dst, next, head, index_hlist) {
                                if (!dst)
                                        continue;

                                if (is_ifindex_excluded(excluded_devices, num_excluded,
                                                        dst->dev->ifindex))
                                        continue;

                                /* we only need n-1 clones; last_dst enqueued below */
                                if (!last_dst) {
                                        last_dst = dst;
                                        continue;
                                }

                                err = dev_map_redirect_clone(last_dst, skb, xdp_prog);
                                if (err)
                                        return err;

                                last_dst = dst;
                        }
                }
        }

        /* consume the first skb and return */
        if (last_dst)
                return dev_map_generic_redirect(last_dst, skb, xdp_prog);

        /* dtab is empty */
        consume_skb(skb);
        return 0;
}

static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
{
        struct bpf_dtab_netdev *obj = __dev_map_lookup_elem(map, *(u32 *)key);

        return obj ? &obj->val : NULL;
}

static void *dev_map_hash_lookup_elem(struct bpf_map *map, void *key)
{
        struct bpf_dtab_netdev *obj = __dev_map_hash_lookup_elem(map,
                                                                *(u32 *)key);
        return obj ? &obj->val : NULL;
}

static void __dev_map_entry_free(struct rcu_head *rcu)
{
        struct bpf_dtab_netdev *dev;

        dev = container_of(rcu, struct bpf_dtab_netdev, rcu);
        if (dev->xdp_prog)
                bpf_prog_put(dev->xdp_prog);
        dev_put(dev->dev);
        kfree(dev);
}

static long dev_map_delete_elem(struct bpf_map *map, void *key)
{
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        struct bpf_dtab_netdev *old_dev;
        int k = *(u32 *)key;

        if (k >= map->max_entries)
                return -EINVAL;

        old_dev = unrcu_pointer(xchg(&dtab->netdev_map[k], NULL));
        if (old_dev) {
                call_rcu(&old_dev->rcu, __dev_map_entry_free);
                atomic_dec((atomic_t *)&dtab->items);
        }
        return 0;
}

static long dev_map_hash_delete_elem(struct bpf_map *map, void *key)
{
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        struct bpf_dtab_netdev *old_dev;
        int k = *(u32 *)key;
        unsigned long flags;
        int ret = -ENOENT;

        spin_lock_irqsave(&dtab->index_lock, flags);

        old_dev = __dev_map_hash_lookup_elem(map, k);
        if (old_dev) {
                dtab->items--;
                hlist_del_init_rcu(&old_dev->index_hlist);
                call_rcu(&old_dev->rcu, __dev_map_entry_free);
                ret = 0;
        }
        spin_unlock_irqrestore(&dtab->index_lock, flags);

        return ret;
}

static struct bpf_dtab_netdev *__dev_map_alloc_node(struct net *net,
                                                    struct bpf_dtab *dtab,
                                                    struct bpf_devmap_val *val,
                                                    unsigned int idx)
{
        struct bpf_prog *prog = NULL;
        struct bpf_dtab_netdev *dev;

        dev = bpf_map_kmalloc_node(&dtab->map, sizeof(*dev),
                                   GFP_NOWAIT | __GFP_NOWARN,
                                   dtab->map.numa_node);
        if (!dev)
                return ERR_PTR(-ENOMEM);

        dev->dev = dev_get_by_index(net, val->ifindex);
        if (!dev->dev)
                goto err_out;

        if (val->bpf_prog.fd > 0) {
                prog = bpf_prog_get_type_dev(val->bpf_prog.fd,
                                             BPF_PROG_TYPE_XDP, false);
                if (IS_ERR(prog))
                        goto err_put_dev;
                if (prog->expected_attach_type != BPF_XDP_DEVMAP ||
                    !bpf_prog_map_compatible(&dtab->map, prog))
                        goto err_put_prog;
        }

        dev->idx = idx;
        if (prog) {
                dev->xdp_prog = prog;
                dev->val.bpf_prog.id = prog->aux->id;
        } else {
                dev->xdp_prog = NULL;
                dev->val.bpf_prog.id = 0;
        }
        dev->val.ifindex = val->ifindex;

        return dev;
err_put_prog:
        bpf_prog_put(prog);
err_put_dev:
        dev_put(dev->dev);
err_out:
        kfree(dev);
        return ERR_PTR(-EINVAL);
}

static long __dev_map_update_elem(struct net *net, struct bpf_map *map,
                                  void *key, void *value, u64 map_flags)
{
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        struct bpf_dtab_netdev *dev, *old_dev;
        struct bpf_devmap_val val = {};
        u32 i = *(u32 *)key;

        if (unlikely(map_flags > BPF_EXIST))
                return -EINVAL;
        if (unlikely(i >= dtab->map.max_entries))
                return -E2BIG;
        if (unlikely(map_flags == BPF_NOEXIST))
                return -EEXIST;

        /* already verified value_size <= sizeof val */
        memcpy(&val, value, map->value_size);

        if (!val.ifindex) {
                dev = NULL;
                /* can not specify fd if ifindex is 0 */
                if (val.bpf_prog.fd > 0)
                        return -EINVAL;
        } else {
                dev = __dev_map_alloc_node(net, dtab, &val, i);
                if (IS_ERR(dev))
                        return PTR_ERR(dev);
        }

        /* Use call_rcu() here to ensure rcu critical sections have completed
         * Remembering the driver side flush operation will happen before the
         * net device is removed.
         */
        old_dev = unrcu_pointer(xchg(&dtab->netdev_map[i], RCU_INITIALIZER(dev)));
        if (old_dev)
                call_rcu(&old_dev->rcu, __dev_map_entry_free);
        else
                atomic_inc((atomic_t *)&dtab->items);

        return 0;
}

static long dev_map_update_elem(struct bpf_map *map, void *key, void *value,
                                u64 map_flags)
{
        return __dev_map_update_elem(current->nsproxy->net_ns,
                                     map, key, value, map_flags);
}

static long __dev_map_hash_update_elem(struct net *net, struct bpf_map *map,
                                       void *key, void *value, u64 map_flags)
{
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        struct bpf_dtab_netdev *dev, *old_dev;
        struct bpf_devmap_val val = {};
        u32 idx = *(u32 *)key;
        unsigned long flags;
        int err = -EEXIST;

        /* already verified value_size <= sizeof val */
        memcpy(&val, value, map->value_size);

        if (unlikely(map_flags > BPF_EXIST || !val.ifindex))
                return -EINVAL;

        spin_lock_irqsave(&dtab->index_lock, flags);

        old_dev = __dev_map_hash_lookup_elem(map, idx);
        if (old_dev && (map_flags & BPF_NOEXIST))
                goto out_err;

        dev = __dev_map_alloc_node(net, dtab, &val, idx);
        if (IS_ERR(dev)) {
                err = PTR_ERR(dev);
                goto out_err;
        }

        if (old_dev) {
                hlist_del_rcu(&old_dev->index_hlist);
        } else {
                if (dtab->items >= dtab->map.max_entries) {
                        spin_unlock_irqrestore(&dtab->index_lock, flags);
                        call_rcu(&dev->rcu, __dev_map_entry_free);
                        return -E2BIG;
                }
                dtab->items++;
        }

        hlist_add_head_rcu(&dev->index_hlist,
                           dev_map_index_hash(dtab, idx));
        spin_unlock_irqrestore(&dtab->index_lock, flags);

        if (old_dev)
                call_rcu(&old_dev->rcu, __dev_map_entry_free);

        return 0;

out_err:
        spin_unlock_irqrestore(&dtab->index_lock, flags);
        return err;
}

static long dev_map_hash_update_elem(struct bpf_map *map, void *key, void *value,
                                     u64 map_flags)
{
        return __dev_map_hash_update_elem(current->nsproxy->net_ns,
                                         map, key, value, map_flags);
}

static long dev_map_redirect(struct bpf_map *map, u64 ifindex, u64 flags)
{
        return __bpf_xdp_redirect_map(map, ifindex, flags,
                                      BPF_F_BROADCAST | BPF_F_EXCLUDE_INGRESS,
                                      __dev_map_lookup_elem);
}

static long dev_hash_map_redirect(struct bpf_map *map, u64 ifindex, u64 flags)
{
        return __bpf_xdp_redirect_map(map, ifindex, flags,
                                      BPF_F_BROADCAST | BPF_F_EXCLUDE_INGRESS,
                                      __dev_map_hash_lookup_elem);
}

static u64 dev_map_mem_usage(const struct bpf_map *map)
{
        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
        u64 usage = sizeof(struct bpf_dtab);

        if (map->map_type == BPF_MAP_TYPE_DEVMAP_HASH)
                usage += (u64)dtab->n_buckets * sizeof(struct hlist_head);
        else
                usage += (u64)map->max_entries * sizeof(struct bpf_dtab_netdev *);
        usage += atomic_read((atomic_t *)&dtab->items) *
                         (u64)sizeof(struct bpf_dtab_netdev);
        return usage;
}

BTF_ID_LIST_SINGLE(dev_map_btf_ids, struct, bpf_dtab)
const struct bpf_map_ops dev_map_ops = {
        .map_meta_equal = bpf_map_meta_equal,
        .map_alloc = dev_map_alloc,
        .map_free = dev_map_free,
        .map_get_next_key = dev_map_get_next_key,
        .map_lookup_elem = dev_map_lookup_elem,
        .map_update_elem = dev_map_update_elem,
        .map_delete_elem = dev_map_delete_elem,
        .map_check_btf = map_check_no_btf,
        .map_mem_usage = dev_map_mem_usage,
        .map_btf_id = &dev_map_btf_ids[0],
        .map_redirect = dev_map_redirect,
};

const struct bpf_map_ops dev_map_hash_ops = {
        .map_meta_equal = bpf_map_meta_equal,
        .map_alloc = dev_map_alloc,
        .map_free = dev_map_free,
        .map_get_next_key = dev_map_hash_get_next_key,
        .map_lookup_elem = dev_map_hash_lookup_elem,
        .map_update_elem = dev_map_hash_update_elem,
        .map_delete_elem = dev_map_hash_delete_elem,
        .map_check_btf = map_check_no_btf,
        .map_mem_usage = dev_map_mem_usage,
        .map_btf_id = &dev_map_btf_ids[0],
        .map_redirect = dev_hash_map_redirect,
};

static void dev_map_hash_remove_netdev(struct bpf_dtab *dtab,
                                       struct net_device *netdev)
{
        unsigned long flags;
        u32 i;

        spin_lock_irqsave(&dtab->index_lock, flags);
        for (i = 0; i < dtab->n_buckets; i++) {
                struct bpf_dtab_netdev *dev;
                struct hlist_head *head;
                struct hlist_node *next;

                head = dev_map_index_hash(dtab, i);

                hlist_for_each_entry_safe(dev, next, head, index_hlist) {
                        if (netdev != dev->dev)
                                continue;

                        dtab->items--;
                        hlist_del_rcu(&dev->index_hlist);
                        call_rcu(&dev->rcu, __dev_map_entry_free);
                }
        }
        spin_unlock_irqrestore(&dtab->index_lock, flags);
}

static int dev_map_notification(struct notifier_block *notifier,
                                ulong event, void *ptr)
{
        struct net_device *netdev = netdev_notifier_info_to_dev(ptr);
        struct bpf_dtab *dtab;
        int i, cpu;

        switch (event) {
        case NETDEV_REGISTER:
                if (!netdev->netdev_ops->ndo_xdp_xmit || netdev->xdp_bulkq)
                        break;

                /* will be freed in free_netdev() */
                netdev->xdp_bulkq = alloc_percpu(struct xdp_dev_bulk_queue);
                if (!netdev->xdp_bulkq)
                        return NOTIFY_BAD;

                for_each_possible_cpu(cpu)
                        per_cpu_ptr(netdev->xdp_bulkq, cpu)->dev = netdev;
                break;
        case NETDEV_UNREGISTER:
                /* This rcu_read_lock/unlock pair is needed because
                 * dev_map_list is an RCU list AND to ensure a delete
                 * operation does not free a netdev_map entry while we
                 * are comparing it against the netdev being unregistered.
                 */
                rcu_read_lock();
                list_for_each_entry_rcu(dtab, &dev_map_list, list) {
                        if (dtab->map.map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
                                dev_map_hash_remove_netdev(dtab, netdev);
                                continue;
                        }

                        for (i = 0; i < dtab->map.max_entries; i++) {
                                struct bpf_dtab_netdev *dev, *odev;

                                dev = rcu_dereference(dtab->netdev_map[i]);
                                if (!dev || netdev != dev->dev)
                                        continue;
                                odev = unrcu_pointer(cmpxchg(&dtab->netdev_map[i], RCU_INITIALIZER(dev), NULL));
                                if (dev == odev) {
                                        call_rcu(&dev->rcu,
                                                 __dev_map_entry_free);
                                        atomic_dec((atomic_t *)&dtab->items);
                                }
                        }
                }
                rcu_read_unlock();
                break;
        default:
                break;
        }
        return NOTIFY_OK;
}

static struct notifier_block dev_map_notifier = {
        .notifier_call = dev_map_notification,
};

static int __init dev_map_init(void)
{
        int cpu;

        /* Assure tracepoint shadow struct _bpf_dtab_netdev is in sync */
        BUILD_BUG_ON(offsetof(struct bpf_dtab_netdev, dev) !=
                     offsetof(struct _bpf_dtab_netdev, dev));
        register_netdevice_notifier(&dev_map_notifier);

        for_each_possible_cpu(cpu)
                INIT_LIST_HEAD(&per_cpu(dev_flush_list, cpu));
        return 0;
}

subsys_initcall(dev_map_init);