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
36static 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
44static 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);
57out:
58	spin_unlock(&fq->q.lock);
59	inet_frag_put(&fq->q);
60}
61
62static inline struct lowpan_frag_queue *
63fq_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
84static 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;
153err:
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 */
164static 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;
183out_oom:
184	net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
185	return -1;
186}
187
188static 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
206static 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
220static 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
235rxh_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
243static 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
277int 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
315err:
316	kfree_skb(skb);
317	return -1;
318}
319
320#ifdef CONFIG_SYSCTL
321
322static 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
344/* secret interval has been deprecated */
345static int lowpan_frags_secret_interval_unused;
346static struct ctl_table lowpan_frags_ctl_table[] = {
347	{
348		.procname	= "6lowpanfrag_secret_interval",
349		.data		= &lowpan_frags_secret_interval_unused,
350		.maxlen		= sizeof(int),
351		.mode		= 0644,
352		.proc_handler	= proc_dointvec_jiffies,
353	},
354	{ }
355};
356
357static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
358{
359	struct ctl_table *table;
360	struct ctl_table_header *hdr;
361	struct netns_ieee802154_lowpan *ieee802154_lowpan =
362		net_ieee802154_lowpan(net);
363	size_t table_size = ARRAY_SIZE(lowpan_frags_ns_ctl_table);
364
365	table = lowpan_frags_ns_ctl_table;
366	if (!net_eq(net, &init_net)) {
367		table = kmemdup(table, sizeof(lowpan_frags_ns_ctl_table),
368				GFP_KERNEL);
369		if (table == NULL)
370			goto err_alloc;
371
372		/* Don't export sysctls to unprivileged users */
373		if (net->user_ns != &init_user_ns) {
374			table[0].procname = NULL;
375			table_size = 0;
376		}
377	}
378
379	table[0].data	= &ieee802154_lowpan->fqdir->high_thresh;
380	table[0].extra1	= &ieee802154_lowpan->fqdir->low_thresh;
381	table[1].data	= &ieee802154_lowpan->fqdir->low_thresh;
382	table[1].extra2	= &ieee802154_lowpan->fqdir->high_thresh;
383	table[2].data	= &ieee802154_lowpan->fqdir->timeout;
384
385	hdr = register_net_sysctl_sz(net, "net/ieee802154/6lowpan", table,
386				     table_size);
387	if (hdr == NULL)
388		goto err_reg;
389
390	ieee802154_lowpan->sysctl.frags_hdr = hdr;
391	return 0;
392
393err_reg:
394	if (!net_eq(net, &init_net))
395		kfree(table);
396err_alloc:
397	return -ENOMEM;
398}
399
400static 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
412static struct ctl_table_header *lowpan_ctl_header;
413
414static 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
422static void lowpan_frags_sysctl_unregister(void)
423{
424	unregister_net_sysctl_table(lowpan_ctl_header);
425}
426#else
427static inline int lowpan_frags_ns_sysctl_register(struct net *net)
428{
429	return 0;
430}
431
432static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
433{
434}
435
436static inline int __init lowpan_frags_sysctl_register(void)
437{
438	return 0;
439}
440
441static inline void lowpan_frags_sysctl_unregister(void)
442{
443}
444#endif
445
446static 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
453	res = fqdir_init(&ieee802154_lowpan->fqdir, &lowpan_frags, net);
454	if (res < 0)
455		return res;
456
457	ieee802154_lowpan->fqdir->high_thresh = IPV6_FRAG_HIGH_THRESH;
458	ieee802154_lowpan->fqdir->low_thresh = IPV6_FRAG_LOW_THRESH;
459	ieee802154_lowpan->fqdir->timeout = IPV6_FRAG_TIMEOUT;
460
461	res = lowpan_frags_ns_sysctl_register(net);
462	if (res < 0)
463		fqdir_exit(ieee802154_lowpan->fqdir);
464	return res;
465}
466
467static void __net_exit lowpan_frags_pre_exit_net(struct net *net)
468{
469	struct netns_ieee802154_lowpan *ieee802154_lowpan =
470		net_ieee802154_lowpan(net);
471
472	fqdir_pre_exit(ieee802154_lowpan->fqdir);
473}
474
475static void __net_exit lowpan_frags_exit_net(struct net *net)
476{
477	struct netns_ieee802154_lowpan *ieee802154_lowpan =
478		net_ieee802154_lowpan(net);
479
480	lowpan_frags_ns_sysctl_unregister(net);
481	fqdir_exit(ieee802154_lowpan->fqdir);
482}
483
484static struct pernet_operations lowpan_frags_ops = {
485	.init		= lowpan_frags_init_net,
486	.pre_exit	= lowpan_frags_pre_exit_net,
487	.exit		= lowpan_frags_exit_net,
488};
489
490static u32 lowpan_key_hashfn(const void *data, u32 len, u32 seed)
491{
492	return jhash2(data,
493		      sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
494}
495
496static u32 lowpan_obj_hashfn(const void *data, u32 len, u32 seed)
497{
498	const struct inet_frag_queue *fq = data;
499
500	return jhash2((const u32 *)&fq->key,
501		      sizeof(struct frag_lowpan_compare_key) / sizeof(u32), seed);
502}
503
504static int lowpan_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr)
505{
506	const struct frag_lowpan_compare_key *key = arg->key;
507	const struct inet_frag_queue *fq = ptr;
508
509	return !!memcmp(&fq->key, key, sizeof(*key));
510}
511
512static const struct rhashtable_params lowpan_rhash_params = {
513	.head_offset		= offsetof(struct inet_frag_queue, node),
514	.hashfn			= lowpan_key_hashfn,
515	.obj_hashfn		= lowpan_obj_hashfn,
516	.obj_cmpfn		= lowpan_obj_cmpfn,
517	.automatic_shrinking	= true,
518};
519
520int __init lowpan_net_frag_init(void)
521{
522	int ret;
523
524	lowpan_frags.constructor = lowpan_frag_init;
525	lowpan_frags.destructor = NULL;
526	lowpan_frags.qsize = sizeof(struct frag_queue);
527	lowpan_frags.frag_expire = lowpan_frag_expire;
528	lowpan_frags.frags_cache_name = lowpan_frags_cache_name;
529	lowpan_frags.rhash_params = lowpan_rhash_params;
530	ret = inet_frags_init(&lowpan_frags);
531	if (ret)
532		goto out;
533
534	ret = lowpan_frags_sysctl_register();
535	if (ret)
536		goto err_sysctl;
537
538	ret = register_pernet_subsys(&lowpan_frags_ops);
539	if (ret)
540		goto err_pernet;
541out:
542	return ret;
543err_pernet:
544	lowpan_frags_sysctl_unregister();
545err_sysctl:
546	inet_frags_fini(&lowpan_frags);
547	return ret;
548}
549
550void lowpan_net_frag_exit(void)
551{
552	lowpan_frags_sysctl_unregister();
553	unregister_pernet_subsys(&lowpan_frags_ops);
554	inet_frags_fini(&lowpan_frags);
555}
556