xref: /linux/net/ieee802154/6lowpan/reassembly.c (revision 6315d93541f8a5f77c5ef5c4f25233e66d189603) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*	6LoWPAN fragment reassembly
3  *
4  *	Authors:
5  *	Alexander Aring		<aar@pengutronix.de>
6  *
7  *	Based on: net/ipv6/reassembly.c
8  */
9 
10 #define pr_fmt(fmt) "6LoWPAN: " fmt
11 
12 #include <linux/net.h>
13 #include <linux/list.h>
14 #include <linux/netdevice.h>
15 #include <linux/random.h>
16 #include <linux/jhash.h>
17 #include <linux/skbuff.h>
18 #include <linux/slab.h>
19 #include <linux/export.h>
20 
21 #include <net/ieee802154_netdev.h>
22 #include <net/6lowpan.h>
23 #include <net/ipv6_frag.h>
24 #include <net/inet_frag.h>
25 #include <net/ip.h>
26 
27 #include "6lowpan_i.h"
28 
29 static const char lowpan_frags_cache_name[] = "lowpan-frags";
30 
31 static struct inet_frags lowpan_frags;
32 
33 static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *skb,
34 			     struct sk_buff *prev, struct net_device *ldev,
35 			     int *refs);
36 
37 static void lowpan_frag_init(struct inet_frag_queue *q, const void *a)
38 {
39 	const struct frag_lowpan_compare_key *key = a;
40 
41 	BUILD_BUG_ON(sizeof(*key) > sizeof(q->key));
42 	memcpy(&q->key, key, sizeof(*key));
43 }
44 
45 static void lowpan_frag_expire(struct timer_list *t)
46 {
47 	struct inet_frag_queue *frag = from_timer(frag, t, timer);
48 	struct frag_queue *fq;
49 	int refs = 1;
50 
51 	fq = container_of(frag, struct frag_queue, q);
52 
53 	spin_lock(&fq->q.lock);
54 
55 	if (fq->q.flags & INET_FRAG_COMPLETE)
56 		goto out;
57 
58 	inet_frag_kill(&fq->q, &refs);
59 out:
60 	spin_unlock(&fq->q.lock);
61 	inet_frag_putn(&fq->q, refs);
62 }
63 
64 static inline struct lowpan_frag_queue *
65 fq_find(struct net *net, const struct lowpan_802154_cb *cb,
66 	const struct ieee802154_addr *src,
67 	const struct ieee802154_addr *dst)
68 {
69 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
70 		net_ieee802154_lowpan(net);
71 	struct frag_lowpan_compare_key key = {};
72 	struct inet_frag_queue *q;
73 
74 	key.tag = cb->d_tag;
75 	key.d_size = cb->d_size;
76 	key.src = *src;
77 	key.dst = *dst;
78 
79 	q = inet_frag_find(ieee802154_lowpan->fqdir, &key);
80 	if (!q)
81 		return NULL;
82 
83 	return container_of(q, struct lowpan_frag_queue, q);
84 }
85 
86 static int lowpan_frag_queue(struct lowpan_frag_queue *fq,
87 			     struct sk_buff *skb, u8 frag_type,
88 			     int *refs)
89 {
90 	struct sk_buff *prev_tail;
91 	struct net_device *ldev;
92 	int end, offset, err;
93 
94 	/* inet_frag_queue_* functions use skb->cb; see struct ipfrag_skb_cb
95 	 * in inet_fragment.c
96 	 */
97 	BUILD_BUG_ON(sizeof(struct lowpan_802154_cb) > sizeof(struct inet_skb_parm));
98 	BUILD_BUG_ON(sizeof(struct lowpan_802154_cb) > sizeof(struct inet6_skb_parm));
99 
100 	if (fq->q.flags & INET_FRAG_COMPLETE)
101 		goto err;
102 
103 	offset = lowpan_802154_cb(skb)->d_offset << 3;
104 	end = lowpan_802154_cb(skb)->d_size;
105 
106 	/* Is this the final fragment? */
107 	if (offset + skb->len == end) {
108 		/* If we already have some bits beyond end
109 		 * or have different end, the segment is corrupted.
110 		 */
111 		if (end < fq->q.len ||
112 		    ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len))
113 			goto err;
114 		fq->q.flags |= INET_FRAG_LAST_IN;
115 		fq->q.len = end;
116 	} else {
117 		if (end > fq->q.len) {
118 			/* Some bits beyond end -> corruption. */
119 			if (fq->q.flags & INET_FRAG_LAST_IN)
120 				goto err;
121 			fq->q.len = end;
122 		}
123 	}
124 
125 	ldev = skb->dev;
126 	if (ldev)
127 		skb->dev = NULL;
128 	barrier();
129 
130 	prev_tail = fq->q.fragments_tail;
131 	err = inet_frag_queue_insert(&fq->q, skb, offset, end);
132 	if (err)
133 		goto err;
134 
135 	fq->q.stamp = skb->tstamp;
136 	fq->q.tstamp_type = skb->tstamp_type;
137 	if (frag_type == LOWPAN_DISPATCH_FRAG1)
138 		fq->q.flags |= INET_FRAG_FIRST_IN;
139 
140 	fq->q.meat += skb->len;
141 	add_frag_mem_limit(fq->q.fqdir, skb->truesize);
142 
143 	if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
144 	    fq->q.meat == fq->q.len) {
145 		int res;
146 		unsigned long orefdst = skb->_skb_refdst;
147 
148 		skb->_skb_refdst = 0UL;
149 		res = lowpan_frag_reasm(fq, skb, prev_tail, ldev, refs);
150 		skb->_skb_refdst = orefdst;
151 		return res;
152 	}
153 	skb_dst_drop(skb);
154 
155 	return -1;
156 err:
157 	kfree_skb(skb);
158 	return -1;
159 }
160 
161 /*	Check if this packet is complete.
162  *
163  *	It is called with locked fq, and caller must check that
164  *	queue is eligible for reassembly i.e. it is not COMPLETE,
165  *	the last and the first frames arrived and all the bits are here.
166  */
167 static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *skb,
168 			     struct sk_buff *prev_tail, struct net_device *ldev,
169 			     int *refs)
170 {
171 	void *reasm_data;
172 
173 	inet_frag_kill(&fq->q, refs);
174 
175 	reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
176 	if (!reasm_data)
177 		goto out_oom;
178 	inet_frag_reasm_finish(&fq->q, skb, reasm_data, false);
179 
180 	skb->dev = ldev;
181 	skb->tstamp = fq->q.stamp;
182 	fq->q.rb_fragments = RB_ROOT;
183 	fq->q.fragments_tail = NULL;
184 	fq->q.last_run_head = NULL;
185 
186 	return 1;
187 out_oom:
188 	net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
189 	return -1;
190 }
191 
192 static int lowpan_frag_rx_handlers_result(struct sk_buff *skb,
193 					  lowpan_rx_result res)
194 {
195 	switch (res) {
196 	case RX_QUEUED:
197 		return NET_RX_SUCCESS;
198 	case RX_CONTINUE:
199 		/* nobody cared about this packet */
200 		net_warn_ratelimited("%s: received unknown dispatch\n",
201 				     __func__);
202 
203 		fallthrough;
204 	default:
205 		/* all others failure */
206 		return NET_RX_DROP;
207 	}
208 }
209 
210 static lowpan_rx_result lowpan_frag_rx_h_iphc(struct sk_buff *skb)
211 {
212 	int ret;
213 
214 	if (!lowpan_is_iphc(*skb_network_header(skb)))
215 		return RX_CONTINUE;
216 
217 	ret = lowpan_iphc_decompress(skb);
218 	if (ret < 0)
219 		return RX_DROP;
220 
221 	return RX_QUEUED;
222 }
223 
224 static int lowpan_invoke_frag_rx_handlers(struct sk_buff *skb)
225 {
226 	lowpan_rx_result res;
227 
228 #define CALL_RXH(rxh)			\
229 	do {				\
230 		res = rxh(skb);	\
231 		if (res != RX_CONTINUE)	\
232 			goto rxh_next;	\
233 	} while (0)
234 
235 	/* likely at first */
236 	CALL_RXH(lowpan_frag_rx_h_iphc);
237 	CALL_RXH(lowpan_rx_h_ipv6);
238 
239 rxh_next:
240 	return lowpan_frag_rx_handlers_result(skb, res);
241 #undef CALL_RXH
242 }
243 
244 #define LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK	0x07
245 #define LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT	8
246 
247 static int lowpan_get_cb(struct sk_buff *skb, u8 frag_type,
248 			 struct lowpan_802154_cb *cb)
249 {
250 	bool fail;
251 	u8 high = 0, low = 0;
252 	__be16 d_tag = 0;
253 
254 	fail = lowpan_fetch_skb(skb, &high, 1);
255 	fail |= lowpan_fetch_skb(skb, &low, 1);
256 	/* remove the dispatch value and use first three bits as high value
257 	 * for the datagram size
258 	 */
259 	cb->d_size = (high & LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK) <<
260 		LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT | low;
261 	fail |= lowpan_fetch_skb(skb, &d_tag, 2);
262 	cb->d_tag = ntohs(d_tag);
263 
264 	if (frag_type == LOWPAN_DISPATCH_FRAGN) {
265 		fail |= lowpan_fetch_skb(skb, &cb->d_offset, 1);
266 	} else {
267 		skb_reset_network_header(skb);
268 		cb->d_offset = 0;
269 		/* check if datagram_size has ipv6hdr on FRAG1 */
270 		fail |= cb->d_size < sizeof(struct ipv6hdr);
271 		/* check if we can dereference the dispatch value */
272 		fail |= !skb->len;
273 	}
274 
275 	if (unlikely(fail))
276 		return -EIO;
277 
278 	return 0;
279 }
280 
281 int lowpan_frag_rcv(struct sk_buff *skb, u8 frag_type)
282 {
283 	struct lowpan_frag_queue *fq;
284 	struct net *net = dev_net(skb->dev);
285 	struct lowpan_802154_cb *cb = lowpan_802154_cb(skb);
286 	struct ieee802154_hdr hdr = {};
287 	int err;
288 
289 	if (ieee802154_hdr_peek_addrs(skb, &hdr) < 0)
290 		goto err;
291 
292 	err = lowpan_get_cb(skb, frag_type, cb);
293 	if (err < 0)
294 		goto err;
295 
296 	if (frag_type == LOWPAN_DISPATCH_FRAG1) {
297 		err = lowpan_invoke_frag_rx_handlers(skb);
298 		if (err == NET_RX_DROP)
299 			goto err;
300 	}
301 
302 	if (cb->d_size > IPV6_MIN_MTU) {
303 		net_warn_ratelimited("lowpan_frag_rcv: datagram size exceeds MTU\n");
304 		goto err;
305 	}
306 
307 	rcu_read_lock();
308 	fq = fq_find(net, cb, &hdr.source, &hdr.dest);
309 	if (fq != NULL) {
310 		int ret, refs = 0;
311 
312 		spin_lock(&fq->q.lock);
313 		ret = lowpan_frag_queue(fq, skb, frag_type, &refs);
314 		spin_unlock(&fq->q.lock);
315 
316 		rcu_read_unlock();
317 		inet_frag_putn(&fq->q, refs);
318 		return ret;
319 	}
320 	rcu_read_unlock();
321 
322 err:
323 	kfree_skb(skb);
324 	return -1;
325 }
326 
327 #ifdef CONFIG_SYSCTL
328 
329 static struct ctl_table lowpan_frags_ns_ctl_table[] = {
330 	{
331 		.procname	= "6lowpanfrag_high_thresh",
332 		.maxlen		= sizeof(unsigned long),
333 		.mode		= 0644,
334 		.proc_handler	= proc_doulongvec_minmax,
335 	},
336 	{
337 		.procname	= "6lowpanfrag_low_thresh",
338 		.maxlen		= sizeof(unsigned long),
339 		.mode		= 0644,
340 		.proc_handler	= proc_doulongvec_minmax,
341 	},
342 	{
343 		.procname	= "6lowpanfrag_time",
344 		.maxlen		= sizeof(int),
345 		.mode		= 0644,
346 		.proc_handler	= proc_dointvec_jiffies,
347 	},
348 };
349 
350 /* secret interval has been deprecated */
351 static int lowpan_frags_secret_interval_unused;
352 static struct ctl_table lowpan_frags_ctl_table[] = {
353 	{
354 		.procname	= "6lowpanfrag_secret_interval",
355 		.data		= &lowpan_frags_secret_interval_unused,
356 		.maxlen		= sizeof(int),
357 		.mode		= 0644,
358 		.proc_handler	= proc_dointvec_jiffies,
359 	},
360 };
361 
362 static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
363 {
364 	struct ctl_table *table;
365 	struct ctl_table_header *hdr;
366 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
367 		net_ieee802154_lowpan(net);
368 	size_t table_size = ARRAY_SIZE(lowpan_frags_ns_ctl_table);
369 
370 	table = lowpan_frags_ns_ctl_table;
371 	if (!net_eq(net, &init_net)) {
372 		table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
373 				GFP_KERNEL);
374 		if (table == NULL)
375 			goto err_alloc;
376 
377 		/* Don't export sysctls to unprivileged users */
378 		if (net->user_ns != &init_user_ns)
379 			table_size = 0;
380 	}
381 
382 	table[0].data	= &ieee802154_lowpan->fqdir->high_thresh;
383 	table[0].extra1	= &ieee802154_lowpan->fqdir->low_thresh;
384 	table[1].data	= &ieee802154_lowpan->fqdir->low_thresh;
385 	table[1].extra2	= &ieee802154_lowpan->fqdir->high_thresh;
386 	table[2].data	= &ieee802154_lowpan->fqdir->timeout;
387 
388 	hdr = register_net_sysctl_sz(net, "net/ieee802154/6lowpan", table,
389 				     table_size);
390 	if (hdr == NULL)
391 		goto err_reg;
392 
393 	ieee802154_lowpan->sysctl.frags_hdr = hdr;
394 	return 0;
395 
396 err_reg:
397 	if (!net_eq(net, &init_net))
398 		kfree(table);
399 err_alloc:
400 	return -ENOMEM;
401 }
402 
403 static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
404 {
405 	const struct ctl_table *table;
406 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
407 		net_ieee802154_lowpan(net);
408 
409 	table = ieee802154_lowpan->sysctl.frags_hdr->ctl_table_arg;
410 	unregister_net_sysctl_table(ieee802154_lowpan->sysctl.frags_hdr);
411 	if (!net_eq(net, &init_net))
412 		kfree(table);
413 }
414 
415 static struct ctl_table_header *lowpan_ctl_header;
416 
417 static int __init lowpan_frags_sysctl_register(void)
418 {
419 	lowpan_ctl_header = register_net_sysctl(&init_net,
420 						"net/ieee802154/6lowpan",
421 						lowpan_frags_ctl_table);
422 	return lowpan_ctl_header == NULL ? -ENOMEM : 0;
423 }
424 
425 static void lowpan_frags_sysctl_unregister(void)
426 {
427 	unregister_net_sysctl_table(lowpan_ctl_header);
428 }
429 #else
430 static inline int lowpan_frags_ns_sysctl_register(struct net *net)
431 {
432 	return 0;
433 }
434 
435 static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
436 {
437 }
438 
439 static inline int __init lowpan_frags_sysctl_register(void)
440 {
441 	return 0;
442 }
443 
444 static inline void lowpan_frags_sysctl_unregister(void)
445 {
446 }
447 #endif
448 
449 static int __net_init lowpan_frags_init_net(struct net *net)
450 {
451 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
452 		net_ieee802154_lowpan(net);
453 	int res;
454 
455 
456 	res = fqdir_init(&ieee802154_lowpan->fqdir, &lowpan_frags, net);
457 	if (res < 0)
458 		return res;
459 
460 	ieee802154_lowpan->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
461 	ieee802154_lowpan->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
462 	ieee802154_lowpan->fqdir->timeout = IPV6_FRAG_TIMEOUT;
463 
464 	res = lowpan_frags_ns_sysctl_register(net);
465 	if (res < 0)
466 		fqdir_exit(ieee802154_lowpan->fqdir);
467 	return res;
468 }
469 
470 static void __net_exit lowpan_frags_pre_exit_net(struct net *net)
471 {
472 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
473 		net_ieee802154_lowpan(net);
474 
475 	fqdir_pre_exit(ieee802154_lowpan->fqdir);
476 }
477 
478 static void __net_exit lowpan_frags_exit_net(struct net *net)
479 {
480 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
481 		net_ieee802154_lowpan(net);
482 
483 	lowpan_frags_ns_sysctl_unregister(net);
484 	fqdir_exit(ieee802154_lowpan->fqdir);
485 }
486 
487 static struct pernet_operations lowpan_frags_ops = {
488 	.init		= lowpan_frags_init_net,
489 	.pre_exit	= lowpan_frags_pre_exit_net,
490 	.exit		= lowpan_frags_exit_net,
491 };
492 
493 static u32 lowpan_key_hashfn(const void *data, u32 len, u32 seed)
494 {
495 	return jhash2(data,
496 		      sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
497 }
498 
499 static u32 lowpan_obj_hashfn(const void *data, u32 len, u32 seed)
500 {
501 	const struct inet_frag_queue *fq = data;
502 
503 	return jhash2((const u32 *)&fq->key,
504 		      sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
505 }
506 
507 static int lowpan_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr)
508 {
509 	const struct frag_lowpan_compare_key *key = arg->key;
510 	const struct inet_frag_queue *fq = ptr;
511 
512 	return !!memcmp(&fq->key, key, sizeof(*key));
513 }
514 
515 static const struct rhashtable_params lowpan_rhash_params = {
516 	.head_offset		= offsetof(struct inet_frag_queue, node),
517 	.hashfn			= lowpan_key_hashfn,
518 	.obj_hashfn		= lowpan_obj_hashfn,
519 	.obj_cmpfn		= lowpan_obj_cmpfn,
520 	.automatic_shrinking	= true,
521 };
522 
523 int __init lowpan_net_frag_init(void)
524 {
525 	int ret;
526 
527 	lowpan_frags.constructor = lowpan_frag_init;
528 	lowpan_frags.destructor = NULL;
529 	lowpan_frags.qsize = sizeof(struct frag_queue);
530 	lowpan_frags.frag_expire = lowpan_frag_expire;
531 	lowpan_frags.frags_cache_name = lowpan_frags_cache_name;
532 	lowpan_frags.rhash_params = lowpan_rhash_params;
533 	ret = inet_frags_init(&lowpan_frags);
534 	if (ret)
535 		goto out;
536 
537 	ret = lowpan_frags_sysctl_register();
538 	if (ret)
539 		goto err_sysctl;
540 
541 	ret = register_pernet_subsys(&lowpan_frags_ops);
542 	if (ret)
543 		goto err_pernet;
544 out:
545 	return ret;
546 err_pernet:
547 	lowpan_frags_sysctl_unregister();
548 err_sysctl:
549 	inet_frags_fini(&lowpan_frags);
550 	return ret;
551 }
552 
553 void lowpan_net_frag_exit(void)
554 {
555 	lowpan_frags_sysctl_unregister();
556 	unregister_pernet_subsys(&lowpan_frags_ops);
557 	inet_frags_fini(&lowpan_frags);
558 }
559