1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * count the number of connections matching an arbitrary key.
4 *
5 * (C) 2017 Red Hat GmbH
6 * Author: Florian Westphal <fw@strlen.de>
7 *
8 * split from xt_connlimit.c:
9 * (c) 2000 Gerd Knorr <kraxel@bytesex.org>
10 * Nov 2002: Martin Bene <martin.bene@icomedias.com>:
11 * only ignore TIME_WAIT or gone connections
12 * (C) CC Computer Consultants GmbH, 2007
13 */
14#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15#include <linux/in.h>
16#include <linux/in6.h>
17#include <linux/ip.h>
18#include <linux/ipv6.h>
19#include <linux/jhash.h>
20#include <linux/slab.h>
21#include <linux/list.h>
22#include <linux/rbtree.h>
23#include <linux/module.h>
24#include <linux/random.h>
25#include <linux/skbuff.h>
26#include <linux/spinlock.h>
27#include <linux/netfilter/nf_conntrack_tcp.h>
28#include <linux/netfilter/x_tables.h>
29#include <net/netfilter/nf_conntrack.h>
30#include <net/netfilter/nf_conntrack_count.h>
31#include <net/netfilter/nf_conntrack_core.h>
32#include <net/netfilter/nf_conntrack_tuple.h>
33#include <net/netfilter/nf_conntrack_zones.h>
34
35#define CONNCOUNT_SLOTS 256U
36
37#define CONNCOUNT_GC_MAX_NODES 8
38#define MAX_KEYLEN 5
39
40/* we will save the tuples of all connections we care about */
41struct nf_conncount_tuple {
42 struct list_head node;
43 struct nf_conntrack_tuple tuple;
44 struct nf_conntrack_zone zone;
45 int cpu;
46 u32 jiffies32;
47};
48
49struct nf_conncount_rb {
50 struct rb_node node;
51 struct nf_conncount_list list;
52 u32 key[MAX_KEYLEN];
53 struct rcu_head rcu_head;
54};
55
56static spinlock_t nf_conncount_locks[CONNCOUNT_SLOTS] __cacheline_aligned_in_smp;
57
58struct nf_conncount_data {
59 unsigned int keylen;
60 struct rb_root root[CONNCOUNT_SLOTS];
61 struct net *net;
62 struct work_struct gc_work;
63 unsigned long pending_trees[BITS_TO_LONGS(CONNCOUNT_SLOTS)];
64 unsigned int gc_tree;
65};
66
67static u_int32_t conncount_rnd __read_mostly;
68static struct kmem_cache *conncount_rb_cachep __read_mostly;
69static struct kmem_cache *conncount_conn_cachep __read_mostly;
70
71static inline bool already_closed(const struct nf_conn *conn)
72{
73 if (nf_ct_protonum(ct: conn) == IPPROTO_TCP)
74 return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT ||
75 conn->proto.tcp.state == TCP_CONNTRACK_CLOSE;
76 else
77 return false;
78}
79
80static int key_diff(const u32 *a, const u32 *b, unsigned int klen)
81{
82 return memcmp(p: a, q: b, size: klen * sizeof(u32));
83}
84
85static void conn_free(struct nf_conncount_list *list,
86 struct nf_conncount_tuple *conn)
87{
88 lockdep_assert_held(&list->list_lock);
89
90 list->count--;
91 list_del(entry: &conn->node);
92
93 kmem_cache_free(s: conncount_conn_cachep, objp: conn);
94}
95
96static const struct nf_conntrack_tuple_hash *
97find_or_evict(struct net *net, struct nf_conncount_list *list,
98 struct nf_conncount_tuple *conn)
99{
100 const struct nf_conntrack_tuple_hash *found;
101 unsigned long a, b;
102 int cpu = raw_smp_processor_id();
103 u32 age;
104
105 found = nf_conntrack_find_get(net, zone: &conn->zone, tuple: &conn->tuple);
106 if (found)
107 return found;
108 b = conn->jiffies32;
109 a = (u32)jiffies;
110
111 /* conn might have been added just before by another cpu and
112 * might still be unconfirmed. In this case, nf_conntrack_find()
113 * returns no result. Thus only evict if this cpu added the
114 * stale entry or if the entry is older than two jiffies.
115 */
116 age = a - b;
117 if (conn->cpu == cpu || age >= 2) {
118 conn_free(list, conn);
119 return ERR_PTR(error: -ENOENT);
120 }
121
122 return ERR_PTR(error: -EAGAIN);
123}
124
125static int __nf_conncount_add(struct net *net,
126 struct nf_conncount_list *list,
127 const struct nf_conntrack_tuple *tuple,
128 const struct nf_conntrack_zone *zone)
129{
130 const struct nf_conntrack_tuple_hash *found;
131 struct nf_conncount_tuple *conn, *conn_n;
132 struct nf_conn *found_ct;
133 unsigned int collect = 0;
134
135 if (time_is_after_eq_jiffies((unsigned long)list->last_gc))
136 goto add_new_node;
137
138 /* check the saved connections */
139 list_for_each_entry_safe(conn, conn_n, &list->head, node) {
140 if (collect > CONNCOUNT_GC_MAX_NODES)
141 break;
142
143 found = find_or_evict(net, list, conn);
144 if (IS_ERR(ptr: found)) {
145 /* Not found, but might be about to be confirmed */
146 if (PTR_ERR(ptr: found) == -EAGAIN) {
147 if (nf_ct_tuple_equal(t1: &conn->tuple, t2: tuple) &&
148 nf_ct_zone_id(zone: &conn->zone, dir: conn->zone.dir) ==
149 nf_ct_zone_id(zone, dir: zone->dir))
150 return 0; /* already exists */
151 } else {
152 collect++;
153 }
154 continue;
155 }
156
157 found_ct = nf_ct_tuplehash_to_ctrack(hash: found);
158
159 if (nf_ct_tuple_equal(t1: &conn->tuple, t2: tuple) &&
160 nf_ct_zone_equal(a: found_ct, b: zone, dir: zone->dir)) {
161 /*
162 * We should not see tuples twice unless someone hooks
163 * this into a table without "-p tcp --syn".
164 *
165 * Attempt to avoid a re-add in this case.
166 */
167 nf_ct_put(ct: found_ct);
168 return 0;
169 } else if (already_closed(conn: found_ct)) {
170 /*
171 * we do not care about connections which are
172 * closed already -> ditch it
173 */
174 nf_ct_put(ct: found_ct);
175 conn_free(list, conn);
176 collect++;
177 continue;
178 }
179
180 nf_ct_put(ct: found_ct);
181 }
182
183add_new_node:
184 if (WARN_ON_ONCE(list->count > INT_MAX))
185 return -EOVERFLOW;
186
187 conn = kmem_cache_alloc(cachep: conncount_conn_cachep, GFP_ATOMIC);
188 if (conn == NULL)
189 return -ENOMEM;
190
191 conn->tuple = *tuple;
192 conn->zone = *zone;
193 conn->cpu = raw_smp_processor_id();
194 conn->jiffies32 = (u32)jiffies;
195 list_add_tail(new: &conn->node, head: &list->head);
196 list->count++;
197 list->last_gc = (u32)jiffies;
198 return 0;
199}
200
201int nf_conncount_add(struct net *net,
202 struct nf_conncount_list *list,
203 const struct nf_conntrack_tuple *tuple,
204 const struct nf_conntrack_zone *zone)
205{
206 int ret;
207
208 /* check the saved connections */
209 spin_lock_bh(lock: &list->list_lock);
210 ret = __nf_conncount_add(net, list, tuple, zone);
211 spin_unlock_bh(lock: &list->list_lock);
212
213 return ret;
214}
215EXPORT_SYMBOL_GPL(nf_conncount_add);
216
217void nf_conncount_list_init(struct nf_conncount_list *list)
218{
219 spin_lock_init(&list->list_lock);
220 INIT_LIST_HEAD(list: &list->head);
221 list->count = 0;
222 list->last_gc = (u32)jiffies;
223}
224EXPORT_SYMBOL_GPL(nf_conncount_list_init);
225
226/* Return true if the list is empty. Must be called with BH disabled. */
227bool nf_conncount_gc_list(struct net *net,
228 struct nf_conncount_list *list)
229{
230 const struct nf_conntrack_tuple_hash *found;
231 struct nf_conncount_tuple *conn, *conn_n;
232 struct nf_conn *found_ct;
233 unsigned int collected = 0;
234 bool ret = false;
235
236 /* don't bother if we just did GC */
237 if (time_is_after_eq_jiffies((unsigned long)READ_ONCE(list->last_gc)))
238 return false;
239
240 /* don't bother if other cpu is already doing GC */
241 if (!spin_trylock(lock: &list->list_lock))
242 return false;
243
244 list_for_each_entry_safe(conn, conn_n, &list->head, node) {
245 found = find_or_evict(net, list, conn);
246 if (IS_ERR(ptr: found)) {
247 if (PTR_ERR(ptr: found) == -ENOENT)
248 collected++;
249 continue;
250 }
251
252 found_ct = nf_ct_tuplehash_to_ctrack(hash: found);
253 if (already_closed(conn: found_ct)) {
254 /*
255 * we do not care about connections which are
256 * closed already -> ditch it
257 */
258 nf_ct_put(ct: found_ct);
259 conn_free(list, conn);
260 collected++;
261 continue;
262 }
263
264 nf_ct_put(ct: found_ct);
265 if (collected > CONNCOUNT_GC_MAX_NODES)
266 break;
267 }
268
269 if (!list->count)
270 ret = true;
271 list->last_gc = (u32)jiffies;
272 spin_unlock(lock: &list->list_lock);
273
274 return ret;
275}
276EXPORT_SYMBOL_GPL(nf_conncount_gc_list);
277
278static void __tree_nodes_free(struct rcu_head *h)
279{
280 struct nf_conncount_rb *rbconn;
281
282 rbconn = container_of(h, struct nf_conncount_rb, rcu_head);
283 kmem_cache_free(s: conncount_rb_cachep, objp: rbconn);
284}
285
286/* caller must hold tree nf_conncount_locks[] lock */
287static void tree_nodes_free(struct rb_root *root,
288 struct nf_conncount_rb *gc_nodes[],
289 unsigned int gc_count)
290{
291 struct nf_conncount_rb *rbconn;
292
293 while (gc_count) {
294 rbconn = gc_nodes[--gc_count];
295 spin_lock(lock: &rbconn->list.list_lock);
296 if (!rbconn->list.count) {
297 rb_erase(&rbconn->node, root);
298 call_rcu(head: &rbconn->rcu_head, func: __tree_nodes_free);
299 }
300 spin_unlock(lock: &rbconn->list.list_lock);
301 }
302}
303
304static void schedule_gc_worker(struct nf_conncount_data *data, int tree)
305{
306 set_bit(nr: tree, addr: data->pending_trees);
307 schedule_work(work: &data->gc_work);
308}
309
310static unsigned int
311insert_tree(struct net *net,
312 struct nf_conncount_data *data,
313 struct rb_root *root,
314 unsigned int hash,
315 const u32 *key,
316 const struct nf_conntrack_tuple *tuple,
317 const struct nf_conntrack_zone *zone)
318{
319 struct nf_conncount_rb *gc_nodes[CONNCOUNT_GC_MAX_NODES];
320 struct rb_node **rbnode, *parent;
321 struct nf_conncount_rb *rbconn;
322 struct nf_conncount_tuple *conn;
323 unsigned int count = 0, gc_count = 0;
324 u8 keylen = data->keylen;
325 bool do_gc = true;
326
327 spin_lock_bh(lock: &nf_conncount_locks[hash]);
328restart:
329 parent = NULL;
330 rbnode = &(root->rb_node);
331 while (*rbnode) {
332 int diff;
333 rbconn = rb_entry(*rbnode, struct nf_conncount_rb, node);
334
335 parent = *rbnode;
336 diff = key_diff(a: key, b: rbconn->key, klen: keylen);
337 if (diff < 0) {
338 rbnode = &((*rbnode)->rb_left);
339 } else if (diff > 0) {
340 rbnode = &((*rbnode)->rb_right);
341 } else {
342 int ret;
343
344 ret = nf_conncount_add(net, &rbconn->list, tuple, zone);
345 if (ret)
346 count = 0; /* hotdrop */
347 else
348 count = rbconn->list.count;
349 tree_nodes_free(root, gc_nodes, gc_count);
350 goto out_unlock;
351 }
352
353 if (gc_count >= ARRAY_SIZE(gc_nodes))
354 continue;
355
356 if (do_gc && nf_conncount_gc_list(net, &rbconn->list))
357 gc_nodes[gc_count++] = rbconn;
358 }
359
360 if (gc_count) {
361 tree_nodes_free(root, gc_nodes, gc_count);
362 schedule_gc_worker(data, tree: hash);
363 gc_count = 0;
364 do_gc = false;
365 goto restart;
366 }
367
368 /* expected case: match, insert new node */
369 rbconn = kmem_cache_alloc(cachep: conncount_rb_cachep, GFP_ATOMIC);
370 if (rbconn == NULL)
371 goto out_unlock;
372
373 conn = kmem_cache_alloc(cachep: conncount_conn_cachep, GFP_ATOMIC);
374 if (conn == NULL) {
375 kmem_cache_free(s: conncount_rb_cachep, objp: rbconn);
376 goto out_unlock;
377 }
378
379 conn->tuple = *tuple;
380 conn->zone = *zone;
381 memcpy(rbconn->key, key, sizeof(u32) * keylen);
382
383 nf_conncount_list_init(&rbconn->list);
384 list_add(new: &conn->node, head: &rbconn->list.head);
385 count = 1;
386 rbconn->list.count = count;
387
388 rb_link_node_rcu(node: &rbconn->node, parent, rb_link: rbnode);
389 rb_insert_color(&rbconn->node, root);
390out_unlock:
391 spin_unlock_bh(lock: &nf_conncount_locks[hash]);
392 return count;
393}
394
395static unsigned int
396count_tree(struct net *net,
397 struct nf_conncount_data *data,
398 const u32 *key,
399 const struct nf_conntrack_tuple *tuple,
400 const struct nf_conntrack_zone *zone)
401{
402 struct rb_root *root;
403 struct rb_node *parent;
404 struct nf_conncount_rb *rbconn;
405 unsigned int hash;
406 u8 keylen = data->keylen;
407
408 hash = jhash2(k: key, length: data->keylen, initval: conncount_rnd) % CONNCOUNT_SLOTS;
409 root = &data->root[hash];
410
411 parent = rcu_dereference_raw(root->rb_node);
412 while (parent) {
413 int diff;
414
415 rbconn = rb_entry(parent, struct nf_conncount_rb, node);
416
417 diff = key_diff(a: key, b: rbconn->key, klen: keylen);
418 if (diff < 0) {
419 parent = rcu_dereference_raw(parent->rb_left);
420 } else if (diff > 0) {
421 parent = rcu_dereference_raw(parent->rb_right);
422 } else {
423 int ret;
424
425 if (!tuple) {
426 nf_conncount_gc_list(net, &rbconn->list);
427 return rbconn->list.count;
428 }
429
430 spin_lock_bh(lock: &rbconn->list.list_lock);
431 /* Node might be about to be free'd.
432 * We need to defer to insert_tree() in this case.
433 */
434 if (rbconn->list.count == 0) {
435 spin_unlock_bh(lock: &rbconn->list.list_lock);
436 break;
437 }
438
439 /* same source network -> be counted! */
440 ret = __nf_conncount_add(net, list: &rbconn->list, tuple, zone);
441 spin_unlock_bh(lock: &rbconn->list.list_lock);
442 if (ret)
443 return 0; /* hotdrop */
444 else
445 return rbconn->list.count;
446 }
447 }
448
449 if (!tuple)
450 return 0;
451
452 return insert_tree(net, data, root, hash, key, tuple, zone);
453}
454
455static void tree_gc_worker(struct work_struct *work)
456{
457 struct nf_conncount_data *data = container_of(work, struct nf_conncount_data, gc_work);
458 struct nf_conncount_rb *gc_nodes[CONNCOUNT_GC_MAX_NODES], *rbconn;
459 struct rb_root *root;
460 struct rb_node *node;
461 unsigned int tree, next_tree, gc_count = 0;
462
463 tree = data->gc_tree % CONNCOUNT_SLOTS;
464 root = &data->root[tree];
465
466 local_bh_disable();
467 rcu_read_lock();
468 for (node = rb_first(root); node != NULL; node = rb_next(node)) {
469 rbconn = rb_entry(node, struct nf_conncount_rb, node);
470 if (nf_conncount_gc_list(data->net, &rbconn->list))
471 gc_count++;
472 }
473 rcu_read_unlock();
474 local_bh_enable();
475
476 cond_resched();
477
478 spin_lock_bh(lock: &nf_conncount_locks[tree]);
479 if (gc_count < ARRAY_SIZE(gc_nodes))
480 goto next; /* do not bother */
481
482 gc_count = 0;
483 node = rb_first(root);
484 while (node != NULL) {
485 rbconn = rb_entry(node, struct nf_conncount_rb, node);
486 node = rb_next(node);
487
488 if (rbconn->list.count > 0)
489 continue;
490
491 gc_nodes[gc_count++] = rbconn;
492 if (gc_count >= ARRAY_SIZE(gc_nodes)) {
493 tree_nodes_free(root, gc_nodes, gc_count);
494 gc_count = 0;
495 }
496 }
497
498 tree_nodes_free(root, gc_nodes, gc_count);
499next:
500 clear_bit(nr: tree, addr: data->pending_trees);
501
502 next_tree = (tree + 1) % CONNCOUNT_SLOTS;
503 next_tree = find_next_bit(addr: data->pending_trees, CONNCOUNT_SLOTS, offset: next_tree);
504
505 if (next_tree < CONNCOUNT_SLOTS) {
506 data->gc_tree = next_tree;
507 schedule_work(work);
508 }
509
510 spin_unlock_bh(lock: &nf_conncount_locks[tree]);
511}
512
513/* Count and return number of conntrack entries in 'net' with particular 'key'.
514 * If 'tuple' is not null, insert it into the accounting data structure.
515 * Call with RCU read lock.
516 */
517unsigned int nf_conncount_count(struct net *net,
518 struct nf_conncount_data *data,
519 const u32 *key,
520 const struct nf_conntrack_tuple *tuple,
521 const struct nf_conntrack_zone *zone)
522{
523 return count_tree(net, data, key, tuple, zone);
524}
525EXPORT_SYMBOL_GPL(nf_conncount_count);
526
527struct nf_conncount_data *nf_conncount_init(struct net *net, unsigned int family,
528 unsigned int keylen)
529{
530 struct nf_conncount_data *data;
531 int ret, i;
532
533 if (keylen % sizeof(u32) ||
534 keylen / sizeof(u32) > MAX_KEYLEN ||
535 keylen == 0)
536 return ERR_PTR(error: -EINVAL);
537
538 net_get_random_once(&conncount_rnd, sizeof(conncount_rnd));
539
540 data = kmalloc(size: sizeof(*data), GFP_KERNEL);
541 if (!data)
542 return ERR_PTR(error: -ENOMEM);
543
544 ret = nf_ct_netns_get(net, nfproto: family);
545 if (ret < 0) {
546 kfree(objp: data);
547 return ERR_PTR(error: ret);
548 }
549
550 for (i = 0; i < ARRAY_SIZE(data->root); ++i)
551 data->root[i] = RB_ROOT;
552
553 data->keylen = keylen / sizeof(u32);
554 data->net = net;
555 INIT_WORK(&data->gc_work, tree_gc_worker);
556
557 return data;
558}
559EXPORT_SYMBOL_GPL(nf_conncount_init);
560
561void nf_conncount_cache_free(struct nf_conncount_list *list)
562{
563 struct nf_conncount_tuple *conn, *conn_n;
564
565 list_for_each_entry_safe(conn, conn_n, &list->head, node)
566 kmem_cache_free(s: conncount_conn_cachep, objp: conn);
567}
568EXPORT_SYMBOL_GPL(nf_conncount_cache_free);
569
570static void destroy_tree(struct rb_root *r)
571{
572 struct nf_conncount_rb *rbconn;
573 struct rb_node *node;
574
575 while ((node = rb_first(r)) != NULL) {
576 rbconn = rb_entry(node, struct nf_conncount_rb, node);
577
578 rb_erase(node, r);
579
580 nf_conncount_cache_free(&rbconn->list);
581
582 kmem_cache_free(s: conncount_rb_cachep, objp: rbconn);
583 }
584}
585
586void nf_conncount_destroy(struct net *net, unsigned int family,
587 struct nf_conncount_data *data)
588{
589 unsigned int i;
590
591 cancel_work_sync(work: &data->gc_work);
592 nf_ct_netns_put(net, nfproto: family);
593
594 for (i = 0; i < ARRAY_SIZE(data->root); ++i)
595 destroy_tree(r: &data->root[i]);
596
597 kfree(objp: data);
598}
599EXPORT_SYMBOL_GPL(nf_conncount_destroy);
600
601static int __init nf_conncount_modinit(void)
602{
603 int i;
604
605 for (i = 0; i < CONNCOUNT_SLOTS; ++i)
606 spin_lock_init(&nf_conncount_locks[i]);
607
608 conncount_conn_cachep = kmem_cache_create(name: "nf_conncount_tuple",
609 size: sizeof(struct nf_conncount_tuple),
610 align: 0, flags: 0, NULL);
611 if (!conncount_conn_cachep)
612 return -ENOMEM;
613
614 conncount_rb_cachep = kmem_cache_create(name: "nf_conncount_rb",
615 size: sizeof(struct nf_conncount_rb),
616 align: 0, flags: 0, NULL);
617 if (!conncount_rb_cachep) {
618 kmem_cache_destroy(s: conncount_conn_cachep);
619 return -ENOMEM;
620 }
621
622 return 0;
623}
624
625static void __exit nf_conncount_modexit(void)
626{
627 kmem_cache_destroy(s: conncount_conn_cachep);
628 kmem_cache_destroy(s: conncount_rb_cachep);
629}
630
631module_init(nf_conncount_modinit);
632module_exit(nf_conncount_modexit);
633MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
634MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
635MODULE_DESCRIPTION("netfilter: count number of connections matching a key");
636MODULE_LICENSE("GPL");
637

source code of linux/net/netfilter/nf_conncount.c