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->frags, &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.net, 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);
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 		/* fall-through */
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 		.data		= &init_net.ieee802154_lowpan.frags.high_thresh,
325 		.maxlen		= sizeof(unsigned long),
326 		.mode		= 0644,
327 		.proc_handler	= proc_doulongvec_minmax,
328 		.extra1		= &init_net.ieee802154_lowpan.frags.low_thresh
329 	},
330 	{
331 		.procname	= "6lowpanfrag_low_thresh",
332 		.data		= &init_net.ieee802154_lowpan.frags.low_thresh,
333 		.maxlen		= sizeof(unsigned long),
334 		.mode		= 0644,
335 		.proc_handler	= proc_doulongvec_minmax,
336 		.extra2		= &init_net.ieee802154_lowpan.frags.high_thresh
337 	},
338 	{
339 		.procname	= "6lowpanfrag_time",
340 		.data		= &init_net.ieee802154_lowpan.frags.timeout,
341 		.maxlen		= sizeof(int),
342 		.mode		= 0644,
343 		.proc_handler	= proc_dointvec_jiffies,
344 	},
345 	{ }
346 };
347 
348 /* secret interval has been deprecated */
349 static int lowpan_frags_secret_interval_unused;
350 static struct ctl_table lowpan_frags_ctl_table[] = {
351 	{
352 		.procname	= "6lowpanfrag_secret_interval",
353 		.data		= &lowpan_frags_secret_interval_unused,
354 		.maxlen		= sizeof(int),
355 		.mode		= 0644,
356 		.proc_handler	= proc_dointvec_jiffies,
357 	},
358 	{ }
359 };
360 
361 static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
362 {
363 	struct ctl_table *table;
364 	struct ctl_table_header *hdr;
365 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
366 		net_ieee802154_lowpan(net);
367 
368 	table = lowpan_frags_ns_ctl_table;
369 	if (!net_eq(net, &init_net)) {
370 		table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
371 				GFP_KERNEL);
372 		if (table == NULL)
373 			goto err_alloc;
374 
375 		table[0].data = &ieee802154_lowpan->frags.high_thresh;
376 		table[0].extra1 = &ieee802154_lowpan->frags.low_thresh;
377 		table[1].data = &ieee802154_lowpan->frags.low_thresh;
378 		table[1].extra2 = &ieee802154_lowpan->frags.high_thresh;
379 		table[2].data = &ieee802154_lowpan->frags.timeout;
380 
381 		/* Don't export sysctls to unprivileged users */
382 		if (net->user_ns != &init_user_ns)
383 			table[0].procname = NULL;
384 	}
385 
386 	hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table);
387 	if (hdr == NULL)
388 		goto err_reg;
389 
390 	ieee802154_lowpan->sysctl.frags_hdr = hdr;
391 	return 0;
392 
393 err_reg:
394 	if (!net_eq(net, &init_net))
395 		kfree(table);
396 err_alloc:
397 	return -ENOMEM;
398 }
399 
400 static void __net_exit lowpan_frags_ns_sysctl_unregister(struct net *net)
401 {
402 	struct ctl_table *table;
403 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
404 		net_ieee802154_lowpan(net);
405 
406 	table = ieee802154_lowpan->sysctl.frags_hdr->ctl_table_arg;
407 	unregister_net_sysctl_table(ieee802154_lowpan->sysctl.frags_hdr);
408 	if (!net_eq(net, &init_net))
409 		kfree(table);
410 }
411 
412 static struct ctl_table_header *lowpan_ctl_header;
413 
414 static int __init lowpan_frags_sysctl_register(void)
415 {
416 	lowpan_ctl_header = register_net_sysctl(&init_net,
417 						"net/ieee802154/6lowpan",
418 						lowpan_frags_ctl_table);
419 	return lowpan_ctl_header == NULL ? -ENOMEM : 0;
420 }
421 
422 static void lowpan_frags_sysctl_unregister(void)
423 {
424 	unregister_net_sysctl_table(lowpan_ctl_header);
425 }
426 #else
427 static inline int lowpan_frags_ns_sysctl_register(struct net *net)
428 {
429 	return 0;
430 }
431 
432 static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
433 {
434 }
435 
436 static inline int __init lowpan_frags_sysctl_register(void)
437 {
438 	return 0;
439 }
440 
441 static inline void lowpan_frags_sysctl_unregister(void)
442 {
443 }
444 #endif
445 
446 static int __net_init lowpan_frags_init_net(struct net *net)
447 {
448 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
449 		net_ieee802154_lowpan(net);
450 	int res;
451 
452 	ieee802154_lowpan->frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
453 	ieee802154_lowpan->frags.low_thresh = IPV6_FRAG_LOW_THRESH;
454 	ieee802154_lowpan->frags.timeout = IPV6_FRAG_TIMEOUT;
455 	ieee802154_lowpan->frags.f = &lowpan_frags;
456 
457 	res = inet_frags_init_net(&ieee802154_lowpan->frags);
458 	if (res < 0)
459 		return res;
460 	res = lowpan_frags_ns_sysctl_register(net);
461 	if (res < 0)
462 		inet_frags_exit_net(&ieee802154_lowpan->frags);
463 	return res;
464 }
465 
466 static void __net_exit lowpan_frags_exit_net(struct net *net)
467 {
468 	struct netns_ieee802154_lowpan *ieee802154_lowpan =
469 		net_ieee802154_lowpan(net);
470 
471 	lowpan_frags_ns_sysctl_unregister(net);
472 	inet_frags_exit_net(&ieee802154_lowpan->frags);
473 }
474 
475 static struct pernet_operations lowpan_frags_ops = {
476 	.init = lowpan_frags_init_net,
477 	.exit = lowpan_frags_exit_net,
478 };
479 
480 static u32 lowpan_key_hashfn(const void *data, u32 len, u32 seed)
481 {
482 	return jhash2(data,
483 		      sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
484 }
485 
486 static u32 lowpan_obj_hashfn(const void *data, u32 len, u32 seed)
487 {
488 	const struct inet_frag_queue *fq = data;
489 
490 	return jhash2((const u32 *)&fq->key,
491 		      sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
492 }
493 
494 static int lowpan_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr)
495 {
496 	const struct frag_lowpan_compare_key *key = arg->key;
497 	const struct inet_frag_queue *fq = ptr;
498 
499 	return !!memcmp(&fq->key, key, sizeof(*key));
500 }
501 
502 static const struct rhashtable_params lowpan_rhash_params = {
503 	.head_offset		= offsetof(struct inet_frag_queue, node),
504 	.hashfn			= lowpan_key_hashfn,
505 	.obj_hashfn		= lowpan_obj_hashfn,
506 	.obj_cmpfn		= lowpan_obj_cmpfn,
507 	.automatic_shrinking	= true,
508 };
509 
510 int __init lowpan_net_frag_init(void)
511 {
512 	int ret;
513 
514 	lowpan_frags.constructor = lowpan_frag_init;
515 	lowpan_frags.destructor = NULL;
516 	lowpan_frags.qsize = sizeof(struct frag_queue);
517 	lowpan_frags.frag_expire = lowpan_frag_expire;
518 	lowpan_frags.frags_cache_name = lowpan_frags_cache_name;
519 	lowpan_frags.rhash_params = lowpan_rhash_params;
520 	ret = inet_frags_init(&lowpan_frags);
521 	if (ret)
522 		goto out;
523 
524 	ret = lowpan_frags_sysctl_register();
525 	if (ret)
526 		goto err_sysctl;
527 
528 	ret = register_pernet_subsys(&lowpan_frags_ops);
529 	if (ret)
530 		goto err_pernet;
531 out:
532 	return ret;
533 err_pernet:
534 	lowpan_frags_sysctl_unregister();
535 err_sysctl:
536 	inet_frags_fini(&lowpan_frags);
537 	return ret;
538 }
539 
540 void lowpan_net_frag_exit(void)
541 {
542 	inet_frags_fini(&lowpan_frags);
543 	lowpan_frags_sysctl_unregister();
544 	unregister_pernet_subsys(&lowpan_frags_ops);
545 }
546