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	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;
152err:
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 */
163static 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;
182out_oom:
183	net_dbg_ratelimited("lowpan_frag_reasm: no memory for reassembly\n");
184	return -1;
185}
186
187static 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
205static 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
219static 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
234rxh_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
242static 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
276int 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
314err:
315	kfree_skb(skb);
316	return -1;
317}
318
319#ifdef CONFIG_SYSCTL
320
321static 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 */
344static int lowpan_frags_secret_interval_unused;
345static 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
356static 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
388err_reg:
389	if (!net_eq(net, &init_net))
390		kfree(table);
391err_alloc:
392	return -ENOMEM;
393}
394
395static 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
407static struct ctl_table_header *lowpan_ctl_header;
408
409static 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
417static void lowpan_frags_sysctl_unregister(void)
418{
419	unregister_net_sysctl_table(lowpan_ctl_header);
420}
421#else
422static inline int lowpan_frags_ns_sysctl_register(struct net *net)
423{
424	return 0;
425}
426
427static inline void lowpan_frags_ns_sysctl_unregister(struct net *net)
428{
429}
430
431static inline int __init lowpan_frags_sysctl_register(void)
432{
433	return 0;
434}
435
436static inline void lowpan_frags_sysctl_unregister(void)
437{
438}
439#endif
440
441static 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
462static 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
470static 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
479static 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
485static 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
491static 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
499static 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
507static 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
515int __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;
536out:
537	return ret;
538err_pernet:
539	lowpan_frags_sysctl_unregister();
540err_sysctl:
541	inet_frags_fini(&lowpan_frags);
542	return ret;
543}
544
545void 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