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Linux/kernel/bpf/devmap.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /* Copyright (c) 2017 Covalent IO, Inc. http://covalent.io
  3  */
  4 
  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.
  9  *
 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.
 22  *
 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.
 28  *
 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.
 40  *
 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.
 46  */
 47 #include <linux/bpf.h>
 48 #include <net/xdp.h>
 49 #include <linux/filter.h>
 50 #include <trace/events/xdp.h>
 51 
 52 #define DEV_CREATE_FLAG_MASK \
 53         (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
 54 
 55 #define DEV_MAP_BULK_SIZE 16
 56 struct bpf_dtab_netdev;
 57 
 58 struct xdp_bulk_queue {
 59         struct xdp_frame *q[DEV_MAP_BULK_SIZE];
 60         struct list_head flush_node;
 61         struct net_device *dev_rx;
 62         struct bpf_dtab_netdev *obj;
 63         unsigned int count;
 64 };
 65 
 66 struct bpf_dtab_netdev {
 67         struct net_device *dev; /* must be first member, due to tracepoint */
 68         struct hlist_node index_hlist;
 69         struct bpf_dtab *dtab;
 70         struct xdp_bulk_queue __percpu *bulkq;
 71         struct rcu_head rcu;
 72         unsigned int idx; /* keep track of map index for tracepoint */
 73 };
 74 
 75 struct bpf_dtab {
 76         struct bpf_map map;
 77         struct bpf_dtab_netdev **netdev_map; /* DEVMAP type only */
 78         struct list_head __percpu *flush_list;
 79         struct list_head list;
 80 
 81         /* these are only used for DEVMAP_HASH type maps */
 82         struct hlist_head *dev_index_head;
 83         spinlock_t index_lock;
 84         unsigned int items;
 85         u32 n_buckets;
 86 };
 87 
 88 static DEFINE_SPINLOCK(dev_map_lock);
 89 static LIST_HEAD(dev_map_list);
 90 
 91 static struct hlist_head *dev_map_create_hash(unsigned int entries)
 92 {
 93         int i;
 94         struct hlist_head *hash;
 95 
 96         hash = kmalloc_array(entries, sizeof(*hash), GFP_KERNEL);
 97         if (hash != NULL)
 98                 for (i = 0; i < entries; i++)
 99                         INIT_HLIST_HEAD(&hash[i]);
100 
101         return hash;
102 }
103 
104 static inline struct hlist_head *dev_map_index_hash(struct bpf_dtab *dtab,
105                                                     int idx)
106 {
107         return &dtab->dev_index_head[idx & (dtab->n_buckets - 1)];
108 }
109 
110 static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
111 {
112         int err, cpu;
113         u64 cost;
114 
115         /* check sanity of attributes */
116         if (attr->max_entries == 0 || attr->key_size != 4 ||
117             attr->value_size != 4 || attr->map_flags & ~DEV_CREATE_FLAG_MASK)
118                 return -EINVAL;
119 
120         /* Lookup returns a pointer straight to dev->ifindex, so make sure the
121          * verifier prevents writes from the BPF side
122          */
123         attr->map_flags |= BPF_F_RDONLY_PROG;
124 
125 
126         bpf_map_init_from_attr(&dtab->map, attr);
127 
128         /* make sure page count doesn't overflow */
129         cost = (u64) sizeof(struct list_head) * num_possible_cpus();
130 
131         if (attr->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
132                 dtab->n_buckets = roundup_pow_of_two(dtab->map.max_entries);
133 
134                 if (!dtab->n_buckets) /* Overflow check */
135                         return -EINVAL;
136                 cost += (u64) sizeof(struct hlist_head) * dtab->n_buckets;
137         } else {
138                 cost += (u64) dtab->map.max_entries * sizeof(struct bpf_dtab_netdev *);
139         }
140 
141         /* if map size is larger than memlock limit, reject it */
142         err = bpf_map_charge_init(&dtab->map.memory, cost);
143         if (err)
144                 return -EINVAL;
145 
146         dtab->flush_list = alloc_percpu(struct list_head);
147         if (!dtab->flush_list)
148                 goto free_charge;
149 
150         for_each_possible_cpu(cpu)
151                 INIT_LIST_HEAD(per_cpu_ptr(dtab->flush_list, cpu));
152 
153         if (attr->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
154                 dtab->dev_index_head = dev_map_create_hash(dtab->n_buckets);
155                 if (!dtab->dev_index_head)
156                         goto free_percpu;
157 
158                 spin_lock_init(&dtab->index_lock);
159         } else {
160                 dtab->netdev_map = bpf_map_area_alloc(dtab->map.max_entries *
161                                                       sizeof(struct bpf_dtab_netdev *),
162                                                       dtab->map.numa_node);
163                 if (!dtab->netdev_map)
164                         goto free_percpu;
165         }
166 
167         return 0;
168 
169 free_percpu:
170         free_percpu(dtab->flush_list);
171 free_charge:
172         bpf_map_charge_finish(&dtab->map.memory);
173         return -ENOMEM;
174 }
175 
176 static struct bpf_map *dev_map_alloc(union bpf_attr *attr)
177 {
178         struct bpf_dtab *dtab;
179         int err;
180 
181         if (!capable(CAP_NET_ADMIN))
182                 return ERR_PTR(-EPERM);
183 
184         dtab = kzalloc(sizeof(*dtab), GFP_USER);
185         if (!dtab)
186                 return ERR_PTR(-ENOMEM);
187 
188         err = dev_map_init_map(dtab, attr);
189         if (err) {
190                 kfree(dtab);
191                 return ERR_PTR(err);
192         }
193 
194         spin_lock(&dev_map_lock);
195         list_add_tail_rcu(&dtab->list, &dev_map_list);
196         spin_unlock(&dev_map_lock);
197 
198         return &dtab->map;
199 }
200 
201 static void dev_map_free(struct bpf_map *map)
202 {
203         struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
204         int i, cpu;
205 
206         /* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
207          * so the programs (can be more than one that used this map) were
208          * disconnected from events. Wait for outstanding critical sections in
209          * these programs to complete. The rcu critical section only guarantees
210          * no further reads against netdev_map. It does __not__ ensure pending
211          * flush operations (if any) are complete.
212          */
213 
214         spin_lock(&dev_map_lock);
215         list_del_rcu(&dtab->list);
216         spin_unlock(&dev_map_lock);
217 
218         bpf_clear_redirect_map(map);
219         synchronize_rcu();
220 
221         /* Make sure prior __dev_map_entry_free() have completed. */
222         rcu_barrier();
223 
224         /* To ensure all pending flush operations have completed wait for flush
225          * list to empty on _all_ cpus.
226          * Because the above synchronize_rcu() ensures the map is disconnected
227          * from the program we can assume no new items will be added.
228          */
229         for_each_online_cpu(cpu) {
230                 struct list_head *flush_list = per_cpu_ptr(dtab->flush_list, cpu);
231 
232                 while (!list_empty(flush_list))
233                         cond_resched();
234         }
235 
236         if (dtab->map.map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
237                 for (i = 0; i < dtab->n_buckets; i++) {
238                         struct bpf_dtab_netdev *dev;
239                         struct hlist_head *head;
240                         struct hlist_node *next;
241 
242                         head = dev_map_index_hash(dtab, i);
243 
244                         hlist_for_each_entry_safe(dev, next, head, index_hlist) {
245                                 hlist_del_rcu(&dev->index_hlist);
246                                 free_percpu(dev->bulkq);
247                                 dev_put(dev->dev);
248                                 kfree(dev);
249                         }
250                 }
251 
252                 kfree(dtab->dev_index_head);
253         } else {
254                 for (i = 0; i < dtab->map.max_entries; i++) {
255                         struct bpf_dtab_netdev *dev;
256 
257                         dev = dtab->netdev_map[i];
258                         if (!dev)
259                                 continue;
260 
261                         free_percpu(dev->bulkq);
262                         dev_put(dev->dev);
263                         kfree(dev);
264                 }
265 
266                 bpf_map_area_free(dtab->netdev_map);
267         }
268 
269         free_percpu(dtab->flush_list);
270         kfree(dtab);
271 }
272 
273 static int dev_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
274 {
275         struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
276         u32 index = key ? *(u32 *)key : U32_MAX;
277         u32 *next = next_key;
278 
279         if (index >= dtab->map.max_entries) {
280                 *next = 0;
281                 return 0;
282         }
283 
284         if (index == dtab->map.max_entries - 1)
285                 return -ENOENT;
286         *next = index + 1;
287         return 0;
288 }
289 
290 struct bpf_dtab_netdev *__dev_map_hash_lookup_elem(struct bpf_map *map, u32 key)
291 {
292         struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
293         struct hlist_head *head = dev_map_index_hash(dtab, key);
294         struct bpf_dtab_netdev *dev;
295 
296         hlist_for_each_entry_rcu(dev, head, index_hlist,
297                                  lockdep_is_held(&dtab->index_lock))
298                 if (dev->idx == key)
299                         return dev;
300 
301         return NULL;
302 }
303 
304 static int dev_map_hash_get_next_key(struct bpf_map *map, void *key,
305                                     void *next_key)
306 {
307         struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
308         u32 idx, *next = next_key;
309         struct bpf_dtab_netdev *dev, *next_dev;
310         struct hlist_head *head;
311         int i = 0;
312 
313         if (!key)
314                 goto find_first;
315 
316         idx = *(u32 *)key;
317 
318         dev = __dev_map_hash_lookup_elem(map, idx);
319         if (!dev)
320                 goto find_first;
321 
322         next_dev = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(&dev->index_hlist)),
323                                     struct bpf_dtab_netdev, index_hlist);
324 
325         if (next_dev) {
326                 *next = next_dev->idx;
327                 return 0;
328         }
329 
330         i = idx & (dtab->n_buckets - 1);
331         i++;
332 
333  find_first:
334         for (; i < dtab->n_buckets; i++) {
335                 head = dev_map_index_hash(dtab, i);
336 
337                 next_dev = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),
338                                             struct bpf_dtab_netdev,
339                                             index_hlist);
340                 if (next_dev) {
341                         *next = next_dev->idx;
342                         return 0;
343                 }
344         }
345 
346         return -ENOENT;
347 }
348 
349 static int bq_xmit_all(struct xdp_bulk_queue *bq, u32 flags,
350                        bool in_napi_ctx)
351 {
352         struct bpf_dtab_netdev *obj = bq->obj;
353         struct net_device *dev = obj->dev;
354         int sent = 0, drops = 0, err = 0;
355         int i;
356 
357         if (unlikely(!bq->count))
358                 return 0;
359 
360         for (i = 0; i < bq->count; i++) {
361                 struct xdp_frame *xdpf = bq->q[i];
362 
363                 prefetch(xdpf);
364         }
365 
366         sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q, flags);
367         if (sent < 0) {
368                 err = sent;
369                 sent = 0;
370                 goto error;
371         }
372         drops = bq->count - sent;
373 out:
374         bq->count = 0;
375 
376         trace_xdp_devmap_xmit(&obj->dtab->map, obj->idx,
377                               sent, drops, bq->dev_rx, dev, err);
378         bq->dev_rx = NULL;
379         __list_del_clearprev(&bq->flush_node);
380         return 0;
381 error:
382         /* If ndo_xdp_xmit fails with an errno, no frames have been
383          * xmit'ed and it's our responsibility to them free all.
384          */
385         for (i = 0; i < bq->count; i++) {
386                 struct xdp_frame *xdpf = bq->q[i];
387 
388                 /* RX path under NAPI protection, can return frames faster */
389                 if (likely(in_napi_ctx))
390                         xdp_return_frame_rx_napi(xdpf);
391                 else
392                         xdp_return_frame(xdpf);
393                 drops++;
394         }
395         goto out;
396 }
397 
398 /* __dev_map_flush is called from xdp_do_flush_map() which _must_ be signaled
399  * from the driver before returning from its napi->poll() routine. The poll()
400  * routine is called either from busy_poll context or net_rx_action signaled
401  * from NET_RX_SOFTIRQ. Either way the poll routine must complete before the
402  * net device can be torn down. On devmap tear down we ensure the flush list
403  * is empty before completing to ensure all flush operations have completed.
404  */
405 void __dev_map_flush(struct bpf_map *map)
406 {
407         struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
408         struct list_head *flush_list = this_cpu_ptr(dtab->flush_list);
409         struct xdp_bulk_queue *bq, *tmp;
410 
411         rcu_read_lock();
412         list_for_each_entry_safe(bq, tmp, flush_list, flush_node)
413                 bq_xmit_all(bq, XDP_XMIT_FLUSH, true);
414         rcu_read_unlock();
415 }
416 
417 /* rcu_read_lock (from syscall and BPF contexts) ensures that if a delete and/or
418  * update happens in parallel here a dev_put wont happen until after reading the
419  * ifindex.
420  */
421 struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key)
422 {
423         struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
424         struct bpf_dtab_netdev *obj;
425 
426         if (key >= map->max_entries)
427                 return NULL;
428 
429         obj = READ_ONCE(dtab->netdev_map[key]);
430         return obj;
431 }
432 
433 /* Runs under RCU-read-side, plus in softirq under NAPI protection.
434  * Thus, safe percpu variable access.
435  */
436 static int bq_enqueue(struct bpf_dtab_netdev *obj, struct xdp_frame *xdpf,
437                       struct net_device *dev_rx)
438 
439 {
440         struct list_head *flush_list = this_cpu_ptr(obj->dtab->flush_list);
441         struct xdp_bulk_queue *bq = this_cpu_ptr(obj->bulkq);
442 
443         if (unlikely(bq->count == DEV_MAP_BULK_SIZE))
444                 bq_xmit_all(bq, 0, true);
445 
446         /* Ingress dev_rx will be the same for all xdp_frame's in
447          * bulk_queue, because bq stored per-CPU and must be flushed
448          * from net_device drivers NAPI func end.
449          */
450         if (!bq->dev_rx)
451                 bq->dev_rx = dev_rx;
452 
453         bq->q[bq->count++] = xdpf;
454 
455         if (!bq->flush_node.prev)
456                 list_add(&bq->flush_node, flush_list);
457 
458         return 0;
459 }
460 
461 int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
462                     struct net_device *dev_rx)
463 {
464         struct net_device *dev = dst->dev;
465         struct xdp_frame *xdpf;
466         int err;
467 
468         if (!dev->netdev_ops->ndo_xdp_xmit)
469                 return -EOPNOTSUPP;
470 
471         err = xdp_ok_fwd_dev(dev, xdp->data_end - xdp->data);
472         if (unlikely(err))
473                 return err;
474 
475         xdpf = convert_to_xdp_frame(xdp);
476         if (unlikely(!xdpf))
477                 return -EOVERFLOW;
478 
479         return bq_enqueue(dst, xdpf, dev_rx);
480 }
481 
482 int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
483                              struct bpf_prog *xdp_prog)
484 {
485         int err;
486 
487         err = xdp_ok_fwd_dev(dst->dev, skb->len);
488         if (unlikely(err))
489                 return err;
490         skb->dev = dst->dev;
491         generic_xdp_tx(skb, xdp_prog);
492 
493         return 0;
494 }
495 
496 static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
497 {
498         struct bpf_dtab_netdev *obj = __dev_map_lookup_elem(map, *(u32 *)key);
499         struct net_device *dev = obj ? obj->dev : NULL;
500 
501         return dev ? &dev->ifindex : NULL;
502 }
503 
504 static void *dev_map_hash_lookup_elem(struct bpf_map *map, void *key)
505 {
506         struct bpf_dtab_netdev *obj = __dev_map_hash_lookup_elem(map,
507                                                                 *(u32 *)key);
508         struct net_device *dev = obj ? obj->dev : NULL;
509 
510         return dev ? &dev->ifindex : NULL;
511 }
512 
513 static void dev_map_flush_old(struct bpf_dtab_netdev *dev)
514 {
515         if (dev->dev->netdev_ops->ndo_xdp_xmit) {
516                 struct xdp_bulk_queue *bq;
517                 int cpu;
518 
519                 rcu_read_lock();
520                 for_each_online_cpu(cpu) {
521                         bq = per_cpu_ptr(dev->bulkq, cpu);
522                         bq_xmit_all(bq, XDP_XMIT_FLUSH, false);
523                 }
524                 rcu_read_unlock();
525         }
526 }
527 
528 static void __dev_map_entry_free(struct rcu_head *rcu)
529 {
530         struct bpf_dtab_netdev *dev;
531 
532         dev = container_of(rcu, struct bpf_dtab_netdev, rcu);
533         dev_map_flush_old(dev);
534         free_percpu(dev->bulkq);
535         dev_put(dev->dev);
536         kfree(dev);
537 }
538 
539 static int dev_map_delete_elem(struct bpf_map *map, void *key)
540 {
541         struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
542         struct bpf_dtab_netdev *old_dev;
543         int k = *(u32 *)key;
544 
545         if (k >= map->max_entries)
546                 return -EINVAL;
547 
548         /* Use call_rcu() here to ensure any rcu critical sections have
549          * completed, but this does not guarantee a flush has happened
550          * yet. Because driver side rcu_read_lock/unlock only protects the
551          * running XDP program. However, for pending flush operations the
552          * dev and ctx are stored in another per cpu map. And additionally,
553          * the driver tear down ensures all soft irqs are complete before
554          * removing the net device in the case of dev_put equals zero.
555          */
556         old_dev = xchg(&dtab->netdev_map[k], NULL);
557         if (old_dev)
558                 call_rcu(&old_dev->rcu, __dev_map_entry_free);
559         return 0;
560 }
561 
562 static int dev_map_hash_delete_elem(struct bpf_map *map, void *key)
563 {
564         struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
565         struct bpf_dtab_netdev *old_dev;
566         int k = *(u32 *)key;
567         unsigned long flags;
568         int ret = -ENOENT;
569 
570         spin_lock_irqsave(&dtab->index_lock, flags);
571 
572         old_dev = __dev_map_hash_lookup_elem(map, k);
573         if (old_dev) {
574                 dtab->items--;
575                 hlist_del_init_rcu(&old_dev->index_hlist);
576                 call_rcu(&old_dev->rcu, __dev_map_entry_free);
577                 ret = 0;
578         }
579         spin_unlock_irqrestore(&dtab->index_lock, flags);
580 
581         return ret;
582 }
583 
584 static struct bpf_dtab_netdev *__dev_map_alloc_node(struct net *net,
585                                                     struct bpf_dtab *dtab,
586                                                     u32 ifindex,
587                                                     unsigned int idx)
588 {
589         gfp_t gfp = GFP_ATOMIC | __GFP_NOWARN;
590         struct bpf_dtab_netdev *dev;
591         struct xdp_bulk_queue *bq;
592         int cpu;
593 
594         dev = kmalloc_node(sizeof(*dev), gfp, dtab->map.numa_node);
595         if (!dev)
596                 return ERR_PTR(-ENOMEM);
597 
598         dev->bulkq = __alloc_percpu_gfp(sizeof(*dev->bulkq),
599                                         sizeof(void *), gfp);
600         if (!dev->bulkq) {
601                 kfree(dev);
602                 return ERR_PTR(-ENOMEM);
603         }
604 
605         for_each_possible_cpu(cpu) {
606                 bq = per_cpu_ptr(dev->bulkq, cpu);
607                 bq->obj = dev;
608         }
609 
610         dev->dev = dev_get_by_index(net, ifindex);
611         if (!dev->dev) {
612                 free_percpu(dev->bulkq);
613                 kfree(dev);
614                 return ERR_PTR(-EINVAL);
615         }
616 
617         dev->idx = idx;
618         dev->dtab = dtab;
619 
620         return dev;
621 }
622 
623 static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
624                                  void *key, void *value, u64 map_flags)
625 {
626         struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
627         struct bpf_dtab_netdev *dev, *old_dev;
628         u32 ifindex = *(u32 *)value;
629         u32 i = *(u32 *)key;
630 
631         if (unlikely(map_flags > BPF_EXIST))
632                 return -EINVAL;
633         if (unlikely(i >= dtab->map.max_entries))
634                 return -E2BIG;
635         if (unlikely(map_flags == BPF_NOEXIST))
636                 return -EEXIST;
637 
638         if (!ifindex) {
639                 dev = NULL;
640         } else {
641                 dev = __dev_map_alloc_node(net, dtab, ifindex, i);
642                 if (IS_ERR(dev))
643                         return PTR_ERR(dev);
644         }
645 
646         /* Use call_rcu() here to ensure rcu critical sections have completed
647          * Remembering the driver side flush operation will happen before the
648          * net device is removed.
649          */
650         old_dev = xchg(&dtab->netdev_map[i], dev);
651         if (old_dev)
652                 call_rcu(&old_dev->rcu, __dev_map_entry_free);
653 
654         return 0;
655 }
656 
657 static int dev_map_update_elem(struct bpf_map *map, void *key, void *value,
658                                u64 map_flags)
659 {
660         return __dev_map_update_elem(current->nsproxy->net_ns,
661                                      map, key, value, map_flags);
662 }
663 
664 static int __dev_map_hash_update_elem(struct net *net, struct bpf_map *map,
665                                      void *key, void *value, u64 map_flags)
666 {
667         struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
668         struct bpf_dtab_netdev *dev, *old_dev;
669         u32 ifindex = *(u32 *)value;
670         u32 idx = *(u32 *)key;
671         unsigned long flags;
672         int err = -EEXIST;
673 
674         if (unlikely(map_flags > BPF_EXIST || !ifindex))
675                 return -EINVAL;
676 
677         spin_lock_irqsave(&dtab->index_lock, flags);
678 
679         old_dev = __dev_map_hash_lookup_elem(map, idx);
680         if (old_dev && (map_flags & BPF_NOEXIST))
681                 goto out_err;
682 
683         dev = __dev_map_alloc_node(net, dtab, ifindex, idx);
684         if (IS_ERR(dev)) {
685                 err = PTR_ERR(dev);
686                 goto out_err;
687         }
688 
689         if (old_dev) {
690                 hlist_del_rcu(&old_dev->index_hlist);
691         } else {
692                 if (dtab->items >= dtab->map.max_entries) {
693                         spin_unlock_irqrestore(&dtab->index_lock, flags);
694                         call_rcu(&dev->rcu, __dev_map_entry_free);
695                         return -E2BIG;
696                 }
697                 dtab->items++;
698         }
699 
700         hlist_add_head_rcu(&dev->index_hlist,
701                            dev_map_index_hash(dtab, idx));
702         spin_unlock_irqrestore(&dtab->index_lock, flags);
703 
704         if (old_dev)
705                 call_rcu(&old_dev->rcu, __dev_map_entry_free);
706 
707         return 0;
708 
709 out_err:
710         spin_unlock_irqrestore(&dtab->index_lock, flags);
711         return err;
712 }
713 
714 static int dev_map_hash_update_elem(struct bpf_map *map, void *key, void *value,
715                                    u64 map_flags)
716 {
717         return __dev_map_hash_update_elem(current->nsproxy->net_ns,
718                                          map, key, value, map_flags);
719 }
720 
721 const struct bpf_map_ops dev_map_ops = {
722         .map_alloc = dev_map_alloc,
723         .map_free = dev_map_free,
724         .map_get_next_key = dev_map_get_next_key,
725         .map_lookup_elem = dev_map_lookup_elem,
726         .map_update_elem = dev_map_update_elem,
727         .map_delete_elem = dev_map_delete_elem,
728         .map_check_btf = map_check_no_btf,
729 };
730 
731 const struct bpf_map_ops dev_map_hash_ops = {
732         .map_alloc = dev_map_alloc,
733         .map_free = dev_map_free,
734         .map_get_next_key = dev_map_hash_get_next_key,
735         .map_lookup_elem = dev_map_hash_lookup_elem,
736         .map_update_elem = dev_map_hash_update_elem,
737         .map_delete_elem = dev_map_hash_delete_elem,
738         .map_check_btf = map_check_no_btf,
739 };
740 
741 static void dev_map_hash_remove_netdev(struct bpf_dtab *dtab,
742                                        struct net_device *netdev)
743 {
744         unsigned long flags;
745         u32 i;
746 
747         spin_lock_irqsave(&dtab->index_lock, flags);
748         for (i = 0; i < dtab->n_buckets; i++) {
749                 struct bpf_dtab_netdev *dev;
750                 struct hlist_head *head;
751                 struct hlist_node *next;
752 
753                 head = dev_map_index_hash(dtab, i);
754 
755                 hlist_for_each_entry_safe(dev, next, head, index_hlist) {
756                         if (netdev != dev->dev)
757                                 continue;
758 
759                         dtab->items--;
760                         hlist_del_rcu(&dev->index_hlist);
761                         call_rcu(&dev->rcu, __dev_map_entry_free);
762                 }
763         }
764         spin_unlock_irqrestore(&dtab->index_lock, flags);
765 }
766 
767 static int dev_map_notification(struct notifier_block *notifier,
768                                 ulong event, void *ptr)
769 {
770         struct net_device *netdev = netdev_notifier_info_to_dev(ptr);
771         struct bpf_dtab *dtab;
772         int i;
773 
774         switch (event) {
775         case NETDEV_UNREGISTER:
776                 /* This rcu_read_lock/unlock pair is needed because
777                  * dev_map_list is an RCU list AND to ensure a delete
778                  * operation does not free a netdev_map entry while we
779                  * are comparing it against the netdev being unregistered.
780                  */
781                 rcu_read_lock();
782                 list_for_each_entry_rcu(dtab, &dev_map_list, list) {
783                         if (dtab->map.map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
784                                 dev_map_hash_remove_netdev(dtab, netdev);
785                                 continue;
786                         }
787 
788                         for (i = 0; i < dtab->map.max_entries; i++) {
789                                 struct bpf_dtab_netdev *dev, *odev;
790 
791                                 dev = READ_ONCE(dtab->netdev_map[i]);
792                                 if (!dev || netdev != dev->dev)
793                                         continue;
794                                 odev = cmpxchg(&dtab->netdev_map[i], dev, NULL);
795                                 if (dev == odev)
796                                         call_rcu(&dev->rcu,
797                                                  __dev_map_entry_free);
798                         }
799                 }
800                 rcu_read_unlock();
801                 break;
802         default:
803                 break;
804         }
805         return NOTIFY_OK;
806 }
807 
808 static struct notifier_block dev_map_notifier = {
809         .notifier_call = dev_map_notification,
810 };
811 
812 static int __init dev_map_init(void)
813 {
814         /* Assure tracepoint shadow struct _bpf_dtab_netdev is in sync */
815         BUILD_BUG_ON(offsetof(struct bpf_dtab_netdev, dev) !=
816                      offsetof(struct _bpf_dtab_netdev, dev));
817         register_netdevice_notifier(&dev_map_notifier);
818         return 0;
819 }
820 
821 subsys_initcall(dev_map_init);
822 

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