xref: /linux/net/ieee802154/6lowpan/reassembly.c (revision f14aa5ea415b8add245e976bfab96a12986c6843) 
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 	fq->q.mono_delivery_time = skb->mono_delivery_time;
134 	if (frag_type == LOWPAN_DISPATCH_FRAG1)
135 		fq->q.flags |= INET_FRAG_FIRST_IN;
136 
137 	fq->q.meat += skb->len;
138 	add_frag_mem_limit(fq->q.fqdir, skb->truesize);
139 
140 	if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
141 	    fq->q.meat == fq->q.len) {
142 		int res;
143 		unsigned long orefdst = skb->_skb_refdst;
144 
145 		skb->_skb_refdst = 0UL;
146 		res = lowpan_frag_reasm(fq, skb, prev_tail, ldev);
147 		skb->_skb_refdst = orefdst;
148 		return res;
149 	}
150 	skb_dst_drop(skb);
151 
152 	return -1;
153 err:
154 	kfree_skb(skb);
155 	return -1;
156 }
157 
158 /*	Check if this packet is complete.
159  *
160  *	It is called with locked fq, and caller must check that
161  *	queue is eligible for reassembly i.e. it is not COMPLETE,
162  *	the last and the first frames arrived and all the bits are here.
163  */
164 static int lowpan_frag_reasm(struct lowpan_frag_queue *fq, struct sk_buff *skb,
165 			     struct sk_buff *prev_tail, struct net_device *ldev)
166 {
167 	void *reasm_data;
168 
169 	inet_frag_kill(&fq->q);
170 
171 	reasm_data = inet_frag_reasm_prepare(&fq->q, skb, prev_tail);
172 	if (!reasm_data)
173 		goto out_oom;
174 	inet_frag_reasm_finish(&fq->q, skb, reasm_data, false);
175 
176 	skb->dev = ldev;
177 	skb->tstamp = fq->q.stamp;
178 	fq->q.rb_fragments = RB_ROOT;
179 	fq->q.fragments_tail = NULL;
180 	fq->q.last_run_head = NULL;
181 
182 	return 1;
183 out_oom:
184 	net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
185 	return -1;
186 }
187 
188 static int lowpan_frag_rx_handlers_result(struct sk_buff *skb,
189 					  lowpan_rx_result res)
190 {
191 	switch (res) {
192 	case RX_QUEUED:
193 		return NET_RX_SUCCESS;
194 	case RX_CONTINUE:
195 		/* nobody cared about this packet */
196 		net_warn_ratelimited("%s: received unknown dispatch\n",
197 				     __func__);
198 
199 		fallthrough;
200 	default:
201 		/* all others failure */
202 		return NET_RX_DROP;
203 	}
204 }
205 
206 static lowpan_rx_result lowpan_frag_rx_h_iphc(struct sk_buff *skb)
207 {
208 	int ret;
209 
210 	if (!lowpan_is_iphc(*skb_network_header(skb)))
211 		return RX_CONTINUE;
212 
213 	ret = lowpan_iphc_decompress(skb);
214 	if (ret < 0)
215 		return RX_DROP;
216 
217 	return RX_QUEUED;
218 }
219 
220 static int lowpan_invoke_frag_rx_handlers(struct sk_buff *skb)
221 {
222 	lowpan_rx_result res;
223 
224 #define CALL_RXH(rxh)			\
225 	do {				\
226 		res = rxh(skb);	\
227 		if (res != RX_CONTINUE)	\
228 			goto rxh_next;	\
229 	} while (0)
230 
231 	/* likely at first */
232 	CALL_RXH(lowpan_frag_rx_h_iphc);
233 	CALL_RXH(lowpan_rx_h_ipv6);
234 
235 rxh_next:
236 	return lowpan_frag_rx_handlers_result(skb, res);
237 #undef CALL_RXH
238 }
239 
240 #define LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK	0x07
241 #define LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT	8
242 
243 static int lowpan_get_cb(struct sk_buff *skb, u8 frag_type,
244 			 struct lowpan_802154_cb *cb)
245 {
246 	bool fail;
247 	u8 high = 0, low = 0;
248 	__be16 d_tag = 0;
249 
250 	fail = lowpan_fetch_skb(skb, &high, 1);
251 	fail |= lowpan_fetch_skb(skb, &low, 1);
252 	/* remove the dispatch value and use first three bits as high value
253 	 * for the datagram size
254 	 */
255 	cb->d_size = (high & LOWPAN_FRAG_DGRAM_SIZE_HIGH_MASK) <<
256 		LOWPAN_FRAG_DGRAM_SIZE_HIGH_SHIFT | low;
257 	fail |= lowpan_fetch_skb(skb, &d_tag, 2);
258 	cb->d_tag = ntohs(d_tag);
259 
260 	if (frag_type == LOWPAN_DISPATCH_FRAGN) {
261 		fail |= lowpan_fetch_skb(skb, &cb->d_offset, 1);
262 	} else {
263 		skb_reset_network_header(skb);
264 		cb->d_offset = 0;
265 		/* check if datagram_size has ipv6hdr on FRAG1 */
266 		fail |= cb->d_size < sizeof(struct ipv6hdr);
267 		/* check if we can dereference the dispatch value */
268 		fail |= !skb->len;
269 	}
270 
271 	if (unlikely(fail))
272 		return -EIO;
273 
274 	return 0;
275 }
276 
277 int lowpan_frag_rcv(struct sk_buff *skb, u8 frag_type)
278 {
279 	struct lowpan_frag_queue *fq;
280 	struct net *net = dev_net(skb->dev);
281 	struct lowpan_802154_cb *cb = lowpan_802154_cb(skb);
282 	struct ieee802154_hdr hdr = {};
283 	int err;
284 
285 	if (ieee802154_hdr_peek_addrs(skb, &hdr) < 0)
286 		goto err;
287 
288 	err = lowpan_get_cb(skb, frag_type, cb);
289 	if (err < 0)
290 		goto err;
291 
292 	if (frag_type == LOWPAN_DISPATCH_FRAG1) {
293 		err = lowpan_invoke_frag_rx_handlers(skb);
294 		if (err == NET_RX_DROP)
295 			goto err;
296 	}
297 
298 	if (cb->d_size > IPV6_MIN_MTU) {
299 		net_warn_ratelimited("lowpan_frag_rcv: datagram size exceeds MTU\n");
300 		goto err;
301 	}
302 
303 	fq = fq_find(net, cb, &hdr.source, &hdr.dest);
304 	if (fq != NULL) {
305 		int ret;
306 
307 		spin_lock(&fq->q.lock);
308 		ret = lowpan_frag_queue(fq, skb, frag_type);
309 		spin_unlock(&fq->q.lock);
310 
311 		inet_frag_put(&fq->q);
312 		return ret;
313 	}
314 
315 err:
316 	kfree_skb(skb);
317 	return -1;
318 }
319 
320 #ifdef CONFIG_SYSCTL
321 
322 static struct ctl_table lowpan_frags_ns_ctl_table[] = {
323 	{
324 		.procname	= "6lowpanfrag_high_thresh",
325 		.maxlen		= sizeof(unsigned long),
326 		.mode		= 0644,
327 		.proc_handler	= proc_doulongvec_minmax,
328 	},
329 	{
330 		.procname	= "6lowpanfrag_low_thresh",
331 		.maxlen		= sizeof(unsigned long),
332 		.mode		= 0644,
333 		.proc_handler	= proc_doulongvec_minmax,
334 	},
335 	{
336 		.procname	= "6lowpanfrag_time",
337 		.maxlen		= sizeof(int),
338 		.mode		= 0644,
339 		.proc_handler	= proc_dointvec_jiffies,
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 static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
356 {
357 	struct ctl_table *table;
358 	struct ctl_table_header *hdr;
359 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
360 		net_ieee802154_lowpan(net);
361 	size_t table_size = ARRAY_SIZE(lowpan_frags_ns_ctl_table);
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_size = 0;
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_sz(net, "net/ieee802154/6lowpan", table,
382 				     table_size);
383 	if (hdr == NULL)
384 		goto err_reg;
385 
386 	ieee802154_lowpan->sysctl.frags_hdr = hdr;
387 	return 0;
388 
389 err_reg:
390 	if (!net_eq(net, &init_net))
391 		kfree(table);
392 err_alloc:
393 	return -ENOMEM;
394 }
395 
396 static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
397 {
398 	const struct ctl_table *table;
399 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
400 		net_ieee802154_lowpan(net);
401 
402 	table = ieee802154_lowpan->sysctl.frags_hdr->ctl_table_arg;
403 	unregister_net_sysctl_table(ieee802154_lowpan->sysctl.frags_hdr);
404 	if (!net_eq(net, &init_net))
405 		kfree(table);
406 }
407 
408 static struct ctl_table_header *lowpan_ctl_header;
409 
410 static int __init lowpan_frags_sysctl_register(void)
411 {
412 	lowpan_ctl_header = register_net_sysctl(&init_net,
413 						"net/ieee802154/6lowpan",
414 						lowpan_frags_ctl_table);
415 	return lowpan_ctl_header == NULL ? -ENOMEM : 0;
416 }
417 
418 static void lowpan_frags_sysctl_unregister(void)
419 {
420 	unregister_net_sysctl_table(lowpan_ctl_header);
421 }
422 #else
423 static inline int lowpan_frags_ns_sysctl_register(struct net *net)
424 {
425 	return 0;
426 }
427 
428 static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
429 {
430 }
431 
432 static inline int __init lowpan_frags_sysctl_register(void)
433 {
434 	return 0;
435 }
436 
437 static inline void lowpan_frags_sysctl_unregister(void)
438 {
439 }
440 #endif
441 
442 static int __net_init lowpan_frags_init_net(struct net *net)
443 {
444 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
445 		net_ieee802154_lowpan(net);
446 	int res;
447 
448 
449 	res = fqdir_init(&ieee802154_lowpan->fqdir, &lowpan_frags, net);
450 	if (res < 0)
451 		return res;
452 
453 	ieee802154_lowpan->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
454 	ieee802154_lowpan->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
455 	ieee802154_lowpan->fqdir->timeout = IPV6_FRAG_TIMEOUT;
456 
457 	res = lowpan_frags_ns_sysctl_register(net);
458 	if (res < 0)
459 		fqdir_exit(ieee802154_lowpan->fqdir);
460 	return res;
461 }
462 
463 static void __net_exit lowpan_frags_pre_exit_net(struct net *net)
464 {
465 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
466 		net_ieee802154_lowpan(net);
467 
468 	fqdir_pre_exit(ieee802154_lowpan->fqdir);
469 }
470 
471 static void __net_exit lowpan_frags_exit_net(struct net *net)
472 {
473 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
474 		net_ieee802154_lowpan(net);
475 
476 	lowpan_frags_ns_sysctl_unregister(net);
477 	fqdir_exit(ieee802154_lowpan->fqdir);
478 }
479 
480 static struct pernet_operations lowpan_frags_ops = {
481 	.init		= lowpan_frags_init_net,
482 	.pre_exit	= lowpan_frags_pre_exit_net,
483 	.exit		= lowpan_frags_exit_net,
484 };
485 
486 static u32 lowpan_key_hashfn(const void *data, u32 len, u32 seed)
487 {
488 	return jhash2(data,
489 		      sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
490 }
491 
492 static u32 lowpan_obj_hashfn(const void *data, u32 len, u32 seed)
493 {
494 	const struct inet_frag_queue *fq = data;
495 
496 	return jhash2((const u32 *)&fq->key,
497 		      sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
498 }
499 
500 static int lowpan_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr)
501 {
502 	const struct frag_lowpan_compare_key *key = arg->key;
503 	const struct inet_frag_queue *fq = ptr;
504 
505 	return !!memcmp(&fq->key, key, sizeof(*key));
506 }
507 
508 static const struct rhashtable_params lowpan_rhash_params = {
509 	.head_offset		= offsetof(struct inet_frag_queue, node),
510 	.hashfn			= lowpan_key_hashfn,
511 	.obj_hashfn		= lowpan_obj_hashfn,
512 	.obj_cmpfn		= lowpan_obj_cmpfn,
513 	.automatic_shrinking	= true,
514 };
515 
516 int __init lowpan_net_frag_init(void)
517 {
518 	int ret;
519 
520 	lowpan_frags.constructor = lowpan_frag_init;
521 	lowpan_frags.destructor = NULL;
522 	lowpan_frags.qsize = sizeof(struct frag_queue);
523 	lowpan_frags.frag_expire = lowpan_frag_expire;
524 	lowpan_frags.frags_cache_name = lowpan_frags_cache_name;
525 	lowpan_frags.rhash_params = lowpan_rhash_params;
526 	ret = inet_frags_init(&lowpan_frags);
527 	if (ret)
528 		goto out;
529 
530 	ret = lowpan_frags_sysctl_register();
531 	if (ret)
532 		goto err_sysctl;
533 
534 	ret = register_pernet_subsys(&lowpan_frags_ops);
535 	if (ret)
536 		goto err_pernet;
537 out:
538 	return ret;
539 err_pernet:
540 	lowpan_frags_sysctl_unregister();
541 err_sysctl:
542 	inet_frags_fini(&lowpan_frags);
543 	return ret;
544 }
545 
546 void lowpan_net_frag_exit(void)
547 {
548 	lowpan_frags_sysctl_unregister();
549 	unregister_pernet_subsys(&lowpan_frags_ops);
550 	inet_frags_fini(&lowpan_frags);
551 }
552