reassembly.c

  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
 29static const char lowpan_frags_cache_name[] = "lowpan-frags";
 30
 31static struct inet_frags lowpan_frags;
 32
 33static 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
 37static 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
 45static void lowpan_frag_expire(struct timer_list *t)
 46{
 47	struct inet_frag_queue *frag = timer_container_of(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);
 59out:
 60	spin_unlock(&fq->q.lock);
 61	inet_frag_putn(&fq->q, refs);
 62}
 63
 64static inline struct lowpan_frag_queue *
 65fq_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
 86static 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;
156err:
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 */
167static 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;
187out_oom:
188	net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
189	return -1;
190}
191
192static 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
210static 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
224static 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
239rxh_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
247static 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
281int 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
322err:
323	kfree_skb(skb);
324	return -1;
325}
326
327#ifdef CONFIG_SYSCTL
328
329static 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 */
351static int lowpan_frags_secret_interval_unused;
352static 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
362static 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
396err_reg:
397	if (!net_eq(net, &init_net))
398		kfree(table);
399err_alloc:
400	return -ENOMEM;
401}
402
403static 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
415static struct ctl_table_header *lowpan_ctl_header;
416
417static 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
425static void lowpan_frags_sysctl_unregister(void)
426{
427	unregister_net_sysctl_table(lowpan_ctl_header);
428}
429#else
430static inline int lowpan_frags_ns_sysctl_register(struct net *net)
431{
432	return 0;
433}
434
435static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
436{
437}
438
439static inline int __init lowpan_frags_sysctl_register(void)
440{
441	return 0;
442}
443
444static inline void lowpan_frags_sysctl_unregister(void)
445{
446}
447#endif
448
449static 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
470static 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
478static 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
487static 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
493static 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
499static 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
507static 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
515static 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
523int __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;
544out:
545	return ret;
546err_pernet:
547	lowpan_frags_sysctl_unregister();
548err_sysctl:
549	inet_frags_fini(&lowpan_frags);
550	return ret;
551}
552
553void 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}