xref: /linux/net/ieee802154/6lowpan/reassembly.c (revision 9dbbc3b9d09d6deba9f3b9e1d5b355032ed46a75) 
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 
36 static void lowpan_frag_init(struct inet_frag_queue *q, const void *a)
37 {
38 	const struct frag_lowpan_compare_key *key = a;
39 
40 	BUILD_BUG_ON(sizeof(*key) > sizeof(q->key));
41 	memcpy(&q->key, key, sizeof(*key));
42 }
43 
44 static void lowpan_frag_expire(struct timer_list *t)
45 {
46 	struct inet_frag_queue *frag = from_timer(frag, t, timer);
47 	struct frag_queue *fq;
48 
49 	fq = container_of(frag, struct frag_queue, q);
50 
51 	spin_lock(&fq->q.lock);
52 
53 	if (fq->q.flags & INET_FRAG_COMPLETE)
54 		goto out;
55 
56 	inet_frag_kill(&fq->q);
57 out:
58 	spin_unlock(&fq->q.lock);
59 	inet_frag_put(&fq->q);
60 }
61 
62 static inline struct lowpan_frag_queue *
63 fq_find(struct net *net, const struct lowpan_802154_cb *cb,
64 	const struct ieee802154_addr *src,
65 	const struct ieee802154_addr *dst)
66 {
67 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
68 		net_ieee802154_lowpan(net);
69 	struct frag_lowpan_compare_key key = {};
70 	struct inet_frag_queue *q;
71 
72 	key.tag = cb->d_tag;
73 	key.d_size = cb->d_size;
74 	key.src = *src;
75 	key.dst = *dst;
76 
77 	q = inet_frag_find(ieee802154_lowpan->fqdir, &key);
78 	if (!q)
79 		return NULL;
80 
81 	return container_of(q, struct lowpan_frag_queue, q);
82 }
83 
84 static int lowpan_frag_queue(struct lowpan_frag_queue *fq,
85 			     struct sk_buff *skb, u8 frag_type)
86 {
87 	struct sk_buff *prev_tail;
88 	struct net_device *ldev;
89 	int end, offset, err;
90 
91 	/* inet_frag_queue_* functions use skb->cb; see struct ipfrag_skb_cb
92 	 * in inet_fragment.c
93 	 */
94 	BUILD_BUG_ON(sizeof(struct lowpan_802154_cb) > sizeof(struct inet_skb_parm));
95 	BUILD_BUG_ON(sizeof(struct lowpan_802154_cb) > sizeof(struct inet6_skb_parm));
96 
97 	if (fq->q.flags & INET_FRAG_COMPLETE)
98 		goto err;
99 
100 	offset = lowpan_802154_cb(skb)->d_offset << 3;
101 	end = lowpan_802154_cb(skb)->d_size;
102 
103 	/* Is this the final fragment? */
104 	if (offset + skb->len == end) {
105 		/* If we already have some bits beyond end
106 		 * or have different end, the segment is corrupted.
107 		 */
108 		if (end < fq->q.len ||
109 		    ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len))
110 			goto err;
111 		fq->q.flags |= INET_FRAG_LAST_IN;
112 		fq->q.len = end;
113 	} else {
114 		if (end > fq->q.len) {
115 			/* Some bits beyond end -> corruption. */
116 			if (fq->q.flags & INET_FRAG_LAST_IN)
117 				goto err;
118 			fq->q.len = end;
119 		}
120 	}
121 
122 	ldev = skb->dev;
123 	if (ldev)
124 		skb->dev = NULL;
125 	barrier();
126 
127 	prev_tail = fq->q.fragments_tail;
128 	err = inet_frag_queue_insert(&fq->q, skb, offset, end);
129 	if (err)
130 		goto err;
131 
132 	fq->q.stamp = skb->tstamp;
133 	if (frag_type == LOWPAN_DISPATCH_FRAG1)
134 		fq->q.flags |= INET_FRAG_FIRST_IN;
135 
136 	fq->q.meat += skb->len;
137 	add_frag_mem_limit(fq->q.fqdir, skb->truesize);
138 
139 	if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
140 	    fq->q.meat == fq->q.len) {
141 		int res;
142 		unsigned long orefdst = skb->_skb_refdst;
143 
144 		skb->_skb_refdst = 0UL;
145 		res = lowpan_frag_reasm(fq, skb, prev_tail, ldev);
146 		skb->_skb_refdst = orefdst;
147 		return res;
148 	}
149 	skb_dst_drop(skb);
150 
151 	return -1;
152 err:
153 	kfree_skb(skb);
154 	return -1;
155 }
156 
157 /*	Check if this packet is complete.
158  *
159  *	It is called with locked fq, and caller must check that
160  *	queue is eligible for reassembly i.e. it is not COMPLETE,
161  *	the last and the first frames arrived and all the bits are here.
162  */
163 static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *skb,
164 			     struct sk_buff *prev_tail, struct net_device *ldev)
165 {
166 	void *reasm_data;
167 
168 	inet_frag_kill(&fq->q);
169 
170 	reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
171 	if (!reasm_data)
172 		goto out_oom;
173 	inet_frag_reasm_finish(&fq->q, skb, reasm_data, false);
174 
175 	skb->dev = ldev;
176 	skb->tstamp = fq->q.stamp;
177 	fq->q.rb_fragments = RB_ROOT;
178 	fq->q.fragments_tail = NULL;
179 	fq->q.last_run_head = NULL;
180 
181 	return 1;
182 out_oom:
183 	net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
184 	return -1;
185 }
186 
187 static int lowpan_frag_rx_handlers_result(struct sk_buff *skb,
188 					  lowpan_rx_result res)
189 {
190 	switch (res) {
191 	case RX_QUEUED:
192 		return NET_RX_SUCCESS;
193 	case RX_CONTINUE:
194 		/* nobody cared about this packet */
195 		net_warn_ratelimited("%s: received unknown dispatch\n",
196 				     __func__);
197 
198 		fallthrough;
199 	default:
200 		/* all others failure */
201 		return NET_RX_DROP;
202 	}
203 }
204 
205 static lowpan_rx_result lowpan_frag_rx_h_iphc(struct sk_buff *skb)
206 {
207 	int ret;
208 
209 	if (!lowpan_is_iphc(*skb_network_header(skb)))
210 		return RX_CONTINUE;
211 
212 	ret = lowpan_iphc_decompress(skb);
213 	if (ret < 0)
214 		return RX_DROP;
215 
216 	return RX_QUEUED;
217 }
218 
219 static int lowpan_invoke_frag_rx_handlers(struct sk_buff *skb)
220 {
221 	lowpan_rx_result res;
222 
223 #define CALL_RXH(rxh)			\
224 	do {				\
225 		res = rxh(skb);	\
226 		if (res != RX_CONTINUE)	\
227 			goto rxh_next;	\
228 	} while (0)
229 
230 	/* likely at first */
231 	CALL_RXH(lowpan_frag_rx_h_iphc);
232 	CALL_RXH(lowpan_rx_h_ipv6);
233 
234 rxh_next:
235 	return lowpan_frag_rx_handlers_result(skb, res);
236 #undef CALL_RXH
237 }
238 
239 #define LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK	0x07
240 #define LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT	8
241 
242 static int lowpan_get_cb(struct sk_buff *skb, u8 frag_type,
243 			 struct lowpan_802154_cb *cb)
244 {
245 	bool fail;
246 	u8 high = 0, low = 0;
247 	__be16 d_tag = 0;
248 
249 	fail = lowpan_fetch_skb(skb, &high, 1);
250 	fail |= lowpan_fetch_skb(skb, &low, 1);
251 	/* remove the dispatch value and use first three bits as high value
252 	 * for the datagram size
253 	 */
254 	cb->d_size = (high & LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK) <<
255 		LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT | low;
256 	fail |= lowpan_fetch_skb(skb, &d_tag, 2);
257 	cb->d_tag = ntohs(d_tag);
258 
259 	if (frag_type == LOWPAN_DISPATCH_FRAGN) {
260 		fail |= lowpan_fetch_skb(skb, &cb->d_offset, 1);
261 	} else {
262 		skb_reset_network_header(skb);
263 		cb->d_offset = 0;
264 		/* check if datagram_size has ipv6hdr on FRAG1 */
265 		fail |= cb->d_size < sizeof(struct ipv6hdr);
266 		/* check if we can dereference the dispatch value */
267 		fail |= !skb->len;
268 	}
269 
270 	if (unlikely(fail))
271 		return -EIO;
272 
273 	return 0;
274 }
275 
276 int lowpan_frag_rcv(struct sk_buff *skb, u8 frag_type)
277 {
278 	struct lowpan_frag_queue *fq;
279 	struct net *net = dev_net(skb->dev);
280 	struct lowpan_802154_cb *cb = lowpan_802154_cb(skb);
281 	struct ieee802154_hdr hdr = {};
282 	int err;
283 
284 	if (ieee802154_hdr_peek_addrs(skb, &hdr) < 0)
285 		goto err;
286 
287 	err = lowpan_get_cb(skb, frag_type, cb);
288 	if (err < 0)
289 		goto err;
290 
291 	if (frag_type == LOWPAN_DISPATCH_FRAG1) {
292 		err = lowpan_invoke_frag_rx_handlers(skb);
293 		if (err == NET_RX_DROP)
294 			goto err;
295 	}
296 
297 	if (cb->d_size > IPV6_MIN_MTU) {
298 		net_warn_ratelimited("lowpan_frag_rcv: datagram size exceeds MTU\n");
299 		goto err;
300 	}
301 
302 	fq = fq_find(net, cb, &hdr.source, &hdr.dest);
303 	if (fq != NULL) {
304 		int ret;
305 
306 		spin_lock(&fq->q.lock);
307 		ret = lowpan_frag_queue(fq, skb, frag_type);
308 		spin_unlock(&fq->q.lock);
309 
310 		inet_frag_put(&fq->q);
311 		return ret;
312 	}
313 
314 err:
315 	kfree_skb(skb);
316 	return -1;
317 }
318 
319 #ifdef CONFIG_SYSCTL
320 
321 static struct ctl_table lowpan_frags_ns_ctl_table[] = {
322 	{
323 		.procname	= "6lowpanfrag_high_thresh",
324 		.maxlen		= sizeof(unsigned long),
325 		.mode		= 0644,
326 		.proc_handler	= proc_doulongvec_minmax,
327 	},
328 	{
329 		.procname	= "6lowpanfrag_low_thresh",
330 		.maxlen		= sizeof(unsigned long),
331 		.mode		= 0644,
332 		.proc_handler	= proc_doulongvec_minmax,
333 	},
334 	{
335 		.procname	= "6lowpanfrag_time",
336 		.maxlen		= sizeof(int),
337 		.mode		= 0644,
338 		.proc_handler	= proc_dointvec_jiffies,
339 	},
340 	{ }
341 };
342 
343 /* secret interval has been deprecated */
344 static int lowpan_frags_secret_interval_unused;
345 static struct ctl_table lowpan_frags_ctl_table[] = {
346 	{
347 		.procname	= "6lowpanfrag_secret_interval",
348 		.data		= &lowpan_frags_secret_interval_unused,
349 		.maxlen		= sizeof(int),
350 		.mode		= 0644,
351 		.proc_handler	= proc_dointvec_jiffies,
352 	},
353 	{ }
354 };
355 
356 static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
357 {
358 	struct ctl_table *table;
359 	struct ctl_table_header *hdr;
360 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
361 		net_ieee802154_lowpan(net);
362 
363 	table = lowpan_frags_ns_ctl_table;
364 	if (!net_eq(net, &init_net)) {
365 		table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
366 				GFP_KERNEL);
367 		if (table == NULL)
368 			goto err_alloc;
369 
370 		/* Don't export sysctls to unprivileged users */
371 		if (net->user_ns != &init_user_ns)
372 			table[0].procname = NULL;
373 	}
374 
375 	table[0].data	= &ieee802154_lowpan->fqdir->high_thresh;
376 	table[0].extra1	= &ieee802154_lowpan->fqdir->low_thresh;
377 	table[1].data	= &ieee802154_lowpan->fqdir->low_thresh;
378 	table[1].extra2	= &ieee802154_lowpan->fqdir->high_thresh;
379 	table[2].data	= &ieee802154_lowpan->fqdir->timeout;
380 
381 	hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table);
382 	if (hdr == NULL)
383 		goto err_reg;
384 
385 	ieee802154_lowpan->sysctl.frags_hdr = hdr;
386 	return 0;
387 
388 err_reg:
389 	if (!net_eq(net, &init_net))
390 		kfree(table);
391 err_alloc:
392 	return -ENOMEM;
393 }
394 
395 static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
396 {
397 	struct ctl_table *table;
398 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
399 		net_ieee802154_lowpan(net);
400 
401 	table = ieee802154_lowpan->sysctl.frags_hdr->ctl_table_arg;
402 	unregister_net_sysctl_table(ieee802154_lowpan->sysctl.frags_hdr);
403 	if (!net_eq(net, &init_net))
404 		kfree(table);
405 }
406 
407 static struct ctl_table_header *lowpan_ctl_header;
408 
409 static int __init lowpan_frags_sysctl_register(void)
410 {
411 	lowpan_ctl_header = register_net_sysctl(&init_net,
412 						"net/ieee802154/6lowpan",
413 						lowpan_frags_ctl_table);
414 	return lowpan_ctl_header == NULL ? -ENOMEM : 0;
415 }
416 
417 static void lowpan_frags_sysctl_unregister(void)
418 {
419 	unregister_net_sysctl_table(lowpan_ctl_header);
420 }
421 #else
422 static inline int lowpan_frags_ns_sysctl_register(struct net *net)
423 {
424 	return 0;
425 }
426 
427 static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
428 {
429 }
430 
431 static inline int __init lowpan_frags_sysctl_register(void)
432 {
433 	return 0;
434 }
435 
436 static inline void lowpan_frags_sysctl_unregister(void)
437 {
438 }
439 #endif
440 
441 static int __net_init lowpan_frags_init_net(struct net *net)
442 {
443 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
444 		net_ieee802154_lowpan(net);
445 	int res;
446 
447 
448 	res = fqdir_init(&ieee802154_lowpan->fqdir, &lowpan_frags, net);
449 	if (res < 0)
450 		return res;
451 
452 	ieee802154_lowpan->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
453 	ieee802154_lowpan->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
454 	ieee802154_lowpan->fqdir->timeout = IPV6_FRAG_TIMEOUT;
455 
456 	res = lowpan_frags_ns_sysctl_register(net);
457 	if (res < 0)
458 		fqdir_exit(ieee802154_lowpan->fqdir);
459 	return res;
460 }
461 
462 static void __net_exit lowpan_frags_pre_exit_net(struct net *net)
463 {
464 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
465 		net_ieee802154_lowpan(net);
466 
467 	fqdir_pre_exit(ieee802154_lowpan->fqdir);
468 }
469 
470 static void __net_exit lowpan_frags_exit_net(struct net *net)
471 {
472 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
473 		net_ieee802154_lowpan(net);
474 
475 	lowpan_frags_ns_sysctl_unregister(net);
476 	fqdir_exit(ieee802154_lowpan->fqdir);
477 }
478 
479 static struct pernet_operations lowpan_frags_ops = {
480 	.init		= lowpan_frags_init_net,
481 	.pre_exit	= lowpan_frags_pre_exit_net,
482 	.exit		= lowpan_frags_exit_net,
483 };
484 
485 static u32 lowpan_key_hashfn(const void *data, u32 len, u32 seed)
486 {
487 	return jhash2(data,
488 		      sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
489 }
490 
491 static u32 lowpan_obj_hashfn(const void *data, u32 len, u32 seed)
492 {
493 	const struct inet_frag_queue *fq = data;
494 
495 	return jhash2((const u32 *)&fq->key,
496 		      sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
497 }
498 
499 static int lowpan_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr)
500 {
501 	const struct frag_lowpan_compare_key *key = arg->key;
502 	const struct inet_frag_queue *fq = ptr;
503 
504 	return !!memcmp(&fq->key, key, sizeof(*key));
505 }
506 
507 static const struct rhashtable_params lowpan_rhash_params = {
508 	.head_offset		= offsetof(struct inet_frag_queue, node),
509 	.hashfn			= lowpan_key_hashfn,
510 	.obj_hashfn		= lowpan_obj_hashfn,
511 	.obj_cmpfn		= lowpan_obj_cmpfn,
512 	.automatic_shrinking	= true,
513 };
514 
515 int __init lowpan_net_frag_init(void)
516 {
517 	int ret;
518 
519 	lowpan_frags.constructor = lowpan_frag_init;
520 	lowpan_frags.destructor = NULL;
521 	lowpan_frags.qsize = sizeof(struct frag_queue);
522 	lowpan_frags.frag_expire = lowpan_frag_expire;
523 	lowpan_frags.frags_cache_name = lowpan_frags_cache_name;
524 	lowpan_frags.rhash_params = lowpan_rhash_params;
525 	ret = inet_frags_init(&lowpan_frags);
526 	if (ret)
527 		goto out;
528 
529 	ret = lowpan_frags_sysctl_register();
530 	if (ret)
531 		goto err_sysctl;
532 
533 	ret = register_pernet_subsys(&lowpan_frags_ops);
534 	if (ret)
535 		goto err_pernet;
536 out:
537 	return ret;
538 err_pernet:
539 	lowpan_frags_sysctl_unregister();
540 err_sysctl:
541 	inet_frags_fini(&lowpan_frags);
542 	return ret;
543 }
544 
545 void lowpan_net_frag_exit(void)
546 {
547 	lowpan_frags_sysctl_unregister();
548 	unregister_pernet_subsys(&lowpan_frags_ops);
549 	inet_frags_fini(&lowpan_frags);
550 }
551