1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Copyright (c) 2017 Covalent IO, Inc. http://covalent.io
5 /* Devmaps primary use is as a backend map for XDP BPF helper call
6 * bpf_redirect_map(). Because XDP is mostly concerned with performance we
7 * spent some effort to ensure the datapath with redirect maps does not use
8 * any locking. This is a quick note on the details.
10 * We have three possible paths to get into the devmap control plane bpf
11 * syscalls, bpf programs, and driver side xmit/flush operations. A bpf syscall
12 * will invoke an update, delete, or lookup operation. To ensure updates and
13 * deletes appear atomic from the datapath side xchg() is used to modify the
14 * netdev_map array. Then because the datapath does a lookup into the netdev_map
15 * array (read-only) from an RCU critical section we use call_rcu() to wait for
16 * an rcu grace period before free'ing the old data structures. This ensures the
17 * datapath always has a valid copy. However, the datapath does a "flush"
18 * operation that pushes any pending packets in the driver outside the RCU
19 * critical section. Each bpf_dtab_netdev tracks these pending operations using
20 * a per-cpu flush list. The bpf_dtab_netdev object will not be destroyed until
21 * this list is empty, indicating outstanding flush operations have completed.
23 * BPF syscalls may race with BPF program calls on any of the update, delete
24 * or lookup operations. As noted above the xchg() operation also keep the
25 * netdev_map consistent in this case. From the devmap side BPF programs
26 * calling into these operations are the same as multiple user space threads
27 * making system calls.
29 * Finally, any of the above may race with a netdev_unregister notifier. The
30 * unregister notifier must search for net devices in the map structure that
31 * contain a reference to the net device and remove them. This is a two step
32 * process (a) dereference the bpf_dtab_netdev object in netdev_map and (b)
33 * check to see if the ifindex is the same as the net_device being removed.
34 * When removing the dev a cmpxchg() is used to ensure the correct dev is
35 * removed, in the case of a concurrent update or delete operation it is
36 * possible that the initially referenced dev is no longer in the map. As the
37 * notifier hook walks the map we know that new dev references can not be
38 * added by the user because core infrastructure ensures dev_get_by_index()
39 * calls will fail at this point.
41 * The devmap_hash type is a map type which interprets keys as ifindexes and
42 * indexes these using a hashmap. This allows maps that use ifindex as key to be
43 * densely packed instead of having holes in the lookup array for unused
44 * ifindexes. The setup and packet enqueue/send code is shared between the two
45 * types of devmap; only the lookup and insertion is different.
47 #include <linux/bpf.h>
49 #include <linux/filter.h>
50 #include <trace/events/xdp.h>
52 #define DEV_CREATE_FLAG_MASK \
53 (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
55 struct xdp_dev_bulk_queue {
56 struct xdp_frame *q[DEV_MAP_BULK_SIZE];
57 struct list_head flush_node;
58 struct net_device *dev;
59 struct net_device *dev_rx;
63 struct bpf_dtab_netdev {
64 struct net_device *dev; /* must be first member, due to tracepoint */
65 struct hlist_node index_hlist;
66 struct bpf_dtab *dtab;
67 struct bpf_prog *xdp_prog;
70 struct bpf_devmap_val val;
75 struct bpf_dtab_netdev **netdev_map; /* DEVMAP type only */
76 struct list_head list;
78 /* these are only used for DEVMAP_HASH type maps */
79 struct hlist_head *dev_index_head;
80 spinlock_t index_lock;
85 static DEFINE_PER_CPU(struct list_head, dev_flush_list);
86 static DEFINE_SPINLOCK(dev_map_lock);
87 static LIST_HEAD(dev_map_list);
89 static struct hlist_head *dev_map_create_hash(unsigned int entries,
93 struct hlist_head *hash;
95 hash = bpf_map_area_alloc(entries * sizeof(*hash), numa_node);
97 for (i = 0; i < entries; i++)
98 INIT_HLIST_HEAD(&hash[i]);
103 static inline struct hlist_head *dev_map_index_hash(struct bpf_dtab *dtab,
106 return &dtab->dev_index_head[idx & (dtab->n_buckets - 1)];
109 static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
111 u32 valsize = attr->value_size;
115 /* check sanity of attributes. 2 value sizes supported:
117 * 8 bytes: ifindex + prog fd
119 if (attr->max_entries == 0 || attr->key_size != 4 ||
120 (valsize != offsetofend(struct bpf_devmap_val, ifindex) &&
121 valsize != offsetofend(struct bpf_devmap_val, bpf_prog.fd)) ||
122 attr->map_flags & ~DEV_CREATE_FLAG_MASK)
125 /* Lookup returns a pointer straight to dev->ifindex, so make sure the
126 * verifier prevents writes from the BPF side
128 attr->map_flags |= BPF_F_RDONLY_PROG;
131 bpf_map_init_from_attr(&dtab->map, attr);
133 if (attr->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
134 dtab->n_buckets = roundup_pow_of_two(dtab->map.max_entries);
136 if (!dtab->n_buckets) /* Overflow check */
138 cost += (u64) sizeof(struct hlist_head) * dtab->n_buckets;
140 cost += (u64) dtab->map.max_entries * sizeof(struct bpf_dtab_netdev *);
143 /* if map size is larger than memlock limit, reject it */
144 err = bpf_map_charge_init(&dtab->map.memory, cost);
148 if (attr->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
149 dtab->dev_index_head = dev_map_create_hash(dtab->n_buckets,
150 dtab->map.numa_node);
151 if (!dtab->dev_index_head)
154 spin_lock_init(&dtab->index_lock);
156 dtab->netdev_map = bpf_map_area_alloc(dtab->map.max_entries *
157 sizeof(struct bpf_dtab_netdev *),
158 dtab->map.numa_node);
159 if (!dtab->netdev_map)
166 bpf_map_charge_finish(&dtab->map.memory);
170 static struct bpf_map *dev_map_alloc(union bpf_attr *attr)
172 struct bpf_dtab *dtab;
175 if (!capable(CAP_NET_ADMIN))
176 return ERR_PTR(-EPERM);
178 dtab = kzalloc(sizeof(*dtab), GFP_USER);
180 return ERR_PTR(-ENOMEM);
182 err = dev_map_init_map(dtab, attr);
188 spin_lock(&dev_map_lock);
189 list_add_tail_rcu(&dtab->list, &dev_map_list);
190 spin_unlock(&dev_map_lock);
195 static void dev_map_free(struct bpf_map *map)
197 struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
200 /* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
201 * so the programs (can be more than one that used this map) were
202 * disconnected from events. The following synchronize_rcu() guarantees
203 * both rcu read critical sections complete and waits for
204 * preempt-disable regions (NAPI being the relevant context here) so we
205 * are certain there will be no further reads against the netdev_map and
206 * all flush operations are complete. Flush operations can only be done
207 * from NAPI context for this reason.
210 spin_lock(&dev_map_lock);
211 list_del_rcu(&dtab->list);
212 spin_unlock(&dev_map_lock);
214 bpf_clear_redirect_map(map);
217 /* Make sure prior __dev_map_entry_free() have completed. */
220 if (dtab->map.map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
221 for (i = 0; i < dtab->n_buckets; i++) {
222 struct bpf_dtab_netdev *dev;
223 struct hlist_head *head;
224 struct hlist_node *next;
226 head = dev_map_index_hash(dtab, i);
228 hlist_for_each_entry_safe(dev, next, head, index_hlist) {
229 hlist_del_rcu(&dev->index_hlist);
231 bpf_prog_put(dev->xdp_prog);
237 bpf_map_area_free(dtab->dev_index_head);
239 for (i = 0; i < dtab->map.max_entries; i++) {
240 struct bpf_dtab_netdev *dev;
242 dev = dtab->netdev_map[i];
247 bpf_prog_put(dev->xdp_prog);
252 bpf_map_area_free(dtab->netdev_map);
258 static int dev_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
260 struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
261 u32 index = key ? *(u32 *)key : U32_MAX;
262 u32 *next = next_key;
264 if (index >= dtab->map.max_entries) {
269 if (index == dtab->map.max_entries - 1)
275 struct bpf_dtab_netdev *__dev_map_hash_lookup_elem(struct bpf_map *map, u32 key)
277 struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
278 struct hlist_head *head = dev_map_index_hash(dtab, key);
279 struct bpf_dtab_netdev *dev;
281 hlist_for_each_entry_rcu(dev, head, index_hlist,
282 lockdep_is_held(&dtab->index_lock))
289 static int dev_map_hash_get_next_key(struct bpf_map *map, void *key,
292 struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
293 u32 idx, *next = next_key;
294 struct bpf_dtab_netdev *dev, *next_dev;
295 struct hlist_head *head;
303 dev = __dev_map_hash_lookup_elem(map, idx);
307 next_dev = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(&dev->index_hlist)),
308 struct bpf_dtab_netdev, index_hlist);
311 *next = next_dev->idx;
315 i = idx & (dtab->n_buckets - 1);
319 for (; i < dtab->n_buckets; i++) {
320 head = dev_map_index_hash(dtab, i);
322 next_dev = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),
323 struct bpf_dtab_netdev,
326 *next = next_dev->idx;
334 bool dev_map_can_have_prog(struct bpf_map *map)
336 if ((map->map_type == BPF_MAP_TYPE_DEVMAP ||
337 map->map_type == BPF_MAP_TYPE_DEVMAP_HASH) &&
338 map->value_size != offsetofend(struct bpf_devmap_val, ifindex))
344 static int bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags)
346 struct net_device *dev = bq->dev;
347 int sent = 0, drops = 0, err = 0;
350 if (unlikely(!bq->count))
353 for (i = 0; i < bq->count; i++) {
354 struct xdp_frame *xdpf = bq->q[i];
359 sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q, flags);
365 drops = bq->count - sent;
369 trace_xdp_devmap_xmit(bq->dev_rx, dev, sent, drops, err);
371 __list_del_clearprev(&bq->flush_node);
374 /* If ndo_xdp_xmit fails with an errno, no frames have been
375 * xmit'ed and it's our responsibility to them free all.
377 for (i = 0; i < bq->count; i++) {
378 struct xdp_frame *xdpf = bq->q[i];
380 xdp_return_frame_rx_napi(xdpf);
386 /* __dev_flush is called from xdp_do_flush() which _must_ be signaled
387 * from the driver before returning from its napi->poll() routine. The poll()
388 * routine is called either from busy_poll context or net_rx_action signaled
389 * from NET_RX_SOFTIRQ. Either way the poll routine must complete before the
390 * net device can be torn down. On devmap tear down we ensure the flush list
391 * is empty before completing to ensure all flush operations have completed.
392 * When drivers update the bpf program they may need to ensure any flush ops
393 * are also complete. Using synchronize_rcu or call_rcu will suffice for this
394 * because both wait for napi context to exit.
396 void __dev_flush(void)
398 struct list_head *flush_list = this_cpu_ptr(&dev_flush_list);
399 struct xdp_dev_bulk_queue *bq, *tmp;
401 list_for_each_entry_safe(bq, tmp, flush_list, flush_node)
402 bq_xmit_all(bq, XDP_XMIT_FLUSH);
405 /* rcu_read_lock (from syscall and BPF contexts) ensures that if a delete and/or
406 * update happens in parallel here a dev_put wont happen until after reading the
409 struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key)
411 struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
412 struct bpf_dtab_netdev *obj;
414 if (key >= map->max_entries)
417 obj = READ_ONCE(dtab->netdev_map[key]);
421 /* Runs under RCU-read-side, plus in softirq under NAPI protection.
422 * Thus, safe percpu variable access.
424 static int bq_enqueue(struct net_device *dev, struct xdp_frame *xdpf,
425 struct net_device *dev_rx)
427 struct list_head *flush_list = this_cpu_ptr(&dev_flush_list);
428 struct xdp_dev_bulk_queue *bq = this_cpu_ptr(dev->xdp_bulkq);
430 if (unlikely(bq->count == DEV_MAP_BULK_SIZE))
433 /* Ingress dev_rx will be the same for all xdp_frame's in
434 * bulk_queue, because bq stored per-CPU and must be flushed
435 * from net_device drivers NAPI func end.
440 bq->q[bq->count++] = xdpf;
442 if (!bq->flush_node.prev)
443 list_add(&bq->flush_node, flush_list);
448 static inline int __xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
449 struct net_device *dev_rx)
451 struct xdp_frame *xdpf;
454 if (!dev->netdev_ops->ndo_xdp_xmit)
457 err = xdp_ok_fwd_dev(dev, xdp->data_end - xdp->data);
461 xdpf = xdp_convert_buff_to_frame(xdp);
465 return bq_enqueue(dev, xdpf, dev_rx);
468 static struct xdp_buff *dev_map_run_prog(struct net_device *dev,
469 struct xdp_buff *xdp,
470 struct bpf_prog *xdp_prog)
472 struct xdp_txq_info txq = { .dev = dev };
475 xdp_set_data_meta_invalid(xdp);
478 act = bpf_prog_run_xdp(xdp_prog, xdp);
485 bpf_warn_invalid_xdp_action(act);
488 trace_xdp_exception(dev, xdp_prog, act);
492 xdp_return_buff(xdp);
496 int dev_xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
497 struct net_device *dev_rx)
499 return __xdp_enqueue(dev, xdp, dev_rx);
502 int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
503 struct net_device *dev_rx)
505 struct net_device *dev = dst->dev;
508 xdp = dev_map_run_prog(dev, xdp, dst->xdp_prog);
512 return __xdp_enqueue(dev, xdp, dev_rx);
515 int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
516 struct bpf_prog *xdp_prog)
520 err = xdp_ok_fwd_dev(dst->dev, skb->len);
524 generic_xdp_tx(skb, xdp_prog);
529 static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
531 struct bpf_dtab_netdev *obj = __dev_map_lookup_elem(map, *(u32 *)key);
533 return obj ? &obj->val : NULL;
536 static void *dev_map_hash_lookup_elem(struct bpf_map *map, void *key)
538 struct bpf_dtab_netdev *obj = __dev_map_hash_lookup_elem(map,
540 return obj ? &obj->val : NULL;
543 static void __dev_map_entry_free(struct rcu_head *rcu)
545 struct bpf_dtab_netdev *dev;
547 dev = container_of(rcu, struct bpf_dtab_netdev, rcu);
549 bpf_prog_put(dev->xdp_prog);
554 static int dev_map_delete_elem(struct bpf_map *map, void *key)
556 struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
557 struct bpf_dtab_netdev *old_dev;
560 if (k >= map->max_entries)
563 /* Use call_rcu() here to ensure any rcu critical sections have
564 * completed as well as any flush operations because call_rcu
565 * will wait for preempt-disable region to complete, NAPI in this
566 * context. And additionally, the driver tear down ensures all
567 * soft irqs are complete before removing the net device in the
568 * case of dev_put equals zero.
570 old_dev = xchg(&dtab->netdev_map[k], NULL);
572 call_rcu(&old_dev->rcu, __dev_map_entry_free);
576 static int dev_map_hash_delete_elem(struct bpf_map *map, void *key)
578 struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
579 struct bpf_dtab_netdev *old_dev;
584 spin_lock_irqsave(&dtab->index_lock, flags);
586 old_dev = __dev_map_hash_lookup_elem(map, k);
589 hlist_del_init_rcu(&old_dev->index_hlist);
590 call_rcu(&old_dev->rcu, __dev_map_entry_free);
593 spin_unlock_irqrestore(&dtab->index_lock, flags);
598 static struct bpf_dtab_netdev *__dev_map_alloc_node(struct net *net,
599 struct bpf_dtab *dtab,
600 struct bpf_devmap_val *val,
603 struct bpf_prog *prog = NULL;
604 struct bpf_dtab_netdev *dev;
606 dev = kmalloc_node(sizeof(*dev), GFP_ATOMIC | __GFP_NOWARN,
607 dtab->map.numa_node);
609 return ERR_PTR(-ENOMEM);
611 dev->dev = dev_get_by_index(net, val->ifindex);
615 if (val->bpf_prog.fd > 0) {
616 prog = bpf_prog_get_type_dev(val->bpf_prog.fd,
617 BPF_PROG_TYPE_XDP, false);
620 if (prog->expected_attach_type != BPF_XDP_DEVMAP)
627 dev->xdp_prog = prog;
628 dev->val.bpf_prog.id = prog->aux->id;
630 dev->xdp_prog = NULL;
631 dev->val.bpf_prog.id = 0;
633 dev->val.ifindex = val->ifindex;
642 return ERR_PTR(-EINVAL);
645 static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
646 void *key, void *value, u64 map_flags)
648 struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
649 struct bpf_dtab_netdev *dev, *old_dev;
650 struct bpf_devmap_val val = {};
653 if (unlikely(map_flags > BPF_EXIST))
655 if (unlikely(i >= dtab->map.max_entries))
657 if (unlikely(map_flags == BPF_NOEXIST))
660 /* already verified value_size <= sizeof val */
661 memcpy(&val, value, map->value_size);
665 /* can not specify fd if ifindex is 0 */
666 if (val.bpf_prog.fd > 0)
669 dev = __dev_map_alloc_node(net, dtab, &val, i);
674 /* Use call_rcu() here to ensure rcu critical sections have completed
675 * Remembering the driver side flush operation will happen before the
676 * net device is removed.
678 old_dev = xchg(&dtab->netdev_map[i], dev);
680 call_rcu(&old_dev->rcu, __dev_map_entry_free);
685 static int dev_map_update_elem(struct bpf_map *map, void *key, void *value,
688 return __dev_map_update_elem(current->nsproxy->net_ns,
689 map, key, value, map_flags);
692 static int __dev_map_hash_update_elem(struct net *net, struct bpf_map *map,
693 void *key, void *value, u64 map_flags)
695 struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
696 struct bpf_dtab_netdev *dev, *old_dev;
697 struct bpf_devmap_val val = {};
698 u32 idx = *(u32 *)key;
702 /* already verified value_size <= sizeof val */
703 memcpy(&val, value, map->value_size);
705 if (unlikely(map_flags > BPF_EXIST || !val.ifindex))
708 spin_lock_irqsave(&dtab->index_lock, flags);
710 old_dev = __dev_map_hash_lookup_elem(map, idx);
711 if (old_dev && (map_flags & BPF_NOEXIST))
714 dev = __dev_map_alloc_node(net, dtab, &val, idx);
721 hlist_del_rcu(&old_dev->index_hlist);
723 if (dtab->items >= dtab->map.max_entries) {
724 spin_unlock_irqrestore(&dtab->index_lock, flags);
725 call_rcu(&dev->rcu, __dev_map_entry_free);
731 hlist_add_head_rcu(&dev->index_hlist,
732 dev_map_index_hash(dtab, idx));
733 spin_unlock_irqrestore(&dtab->index_lock, flags);
736 call_rcu(&old_dev->rcu, __dev_map_entry_free);
741 spin_unlock_irqrestore(&dtab->index_lock, flags);
745 static int dev_map_hash_update_elem(struct bpf_map *map, void *key, void *value,
748 return __dev_map_hash_update_elem(current->nsproxy->net_ns,
749 map, key, value, map_flags);
752 static int dev_map_btf_id;
753 const struct bpf_map_ops dev_map_ops = {
754 .map_alloc = dev_map_alloc,
755 .map_free = dev_map_free,
756 .map_get_next_key = dev_map_get_next_key,
757 .map_lookup_elem = dev_map_lookup_elem,
758 .map_update_elem = dev_map_update_elem,
759 .map_delete_elem = dev_map_delete_elem,
760 .map_check_btf = map_check_no_btf,
761 .map_btf_name = "bpf_dtab",
762 .map_btf_id = &dev_map_btf_id,
765 static int dev_map_hash_map_btf_id;
766 const struct bpf_map_ops dev_map_hash_ops = {
767 .map_alloc = dev_map_alloc,
768 .map_free = dev_map_free,
769 .map_get_next_key = dev_map_hash_get_next_key,
770 .map_lookup_elem = dev_map_hash_lookup_elem,
771 .map_update_elem = dev_map_hash_update_elem,
772 .map_delete_elem = dev_map_hash_delete_elem,
773 .map_check_btf = map_check_no_btf,
774 .map_btf_name = "bpf_dtab",
775 .map_btf_id = &dev_map_hash_map_btf_id,
778 static void dev_map_hash_remove_netdev(struct bpf_dtab *dtab,
779 struct net_device *netdev)
784 spin_lock_irqsave(&dtab->index_lock, flags);
785 for (i = 0; i < dtab->n_buckets; i++) {
786 struct bpf_dtab_netdev *dev;
787 struct hlist_head *head;
788 struct hlist_node *next;
790 head = dev_map_index_hash(dtab, i);
792 hlist_for_each_entry_safe(dev, next, head, index_hlist) {
793 if (netdev != dev->dev)
797 hlist_del_rcu(&dev->index_hlist);
798 call_rcu(&dev->rcu, __dev_map_entry_free);
801 spin_unlock_irqrestore(&dtab->index_lock, flags);
804 static int dev_map_notification(struct notifier_block *notifier,
805 ulong event, void *ptr)
807 struct net_device *netdev = netdev_notifier_info_to_dev(ptr);
808 struct bpf_dtab *dtab;
812 case NETDEV_REGISTER:
813 if (!netdev->netdev_ops->ndo_xdp_xmit || netdev->xdp_bulkq)
816 /* will be freed in free_netdev() */
818 __alloc_percpu_gfp(sizeof(struct xdp_dev_bulk_queue),
819 sizeof(void *), GFP_ATOMIC);
820 if (!netdev->xdp_bulkq)
823 for_each_possible_cpu(cpu)
824 per_cpu_ptr(netdev->xdp_bulkq, cpu)->dev = netdev;
826 case NETDEV_UNREGISTER:
827 /* This rcu_read_lock/unlock pair is needed because
828 * dev_map_list is an RCU list AND to ensure a delete
829 * operation does not free a netdev_map entry while we
830 * are comparing it against the netdev being unregistered.
833 list_for_each_entry_rcu(dtab, &dev_map_list, list) {
834 if (dtab->map.map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
835 dev_map_hash_remove_netdev(dtab, netdev);
839 for (i = 0; i < dtab->map.max_entries; i++) {
840 struct bpf_dtab_netdev *dev, *odev;
842 dev = READ_ONCE(dtab->netdev_map[i]);
843 if (!dev || netdev != dev->dev)
845 odev = cmpxchg(&dtab->netdev_map[i], dev, NULL);
848 __dev_map_entry_free);
859 static struct notifier_block dev_map_notifier = {
860 .notifier_call = dev_map_notification,
863 static int __init dev_map_init(void)
867 /* Assure tracepoint shadow struct _bpf_dtab_netdev is in sync */
868 BUILD_BUG_ON(offsetof(struct bpf_dtab_netdev, dev) !=
869 offsetof(struct _bpf_dtab_netdev, dev));
870 register_netdevice_notifier(&dev_map_notifier);
872 for_each_possible_cpu(cpu)
873 INIT_LIST_HEAD(&per_cpu(dev_flush_list, cpu));
877 subsys_initcall(dev_map_init);