summaryrefslogtreecommitdiff
path: root/drivers/net/wireguard/allowedips.c
blob: 9a4c8ff32d9dd9407ec50591a44008570f4e7411 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
 */

#include "allowedips.h"
#include "peer.h"

static struct kmem_cache *node_cache;

static void swap_endian(u8 *dst, const u8 *src, u8 bits)
{
	if (bits == 32) {
		*(u32 *)dst = be32_to_cpu(*(const __be32 *)src);
	} else if (bits == 128) {
		((u64 *)dst)[0] = be64_to_cpu(((const __be64 *)src)[0]);
		((u64 *)dst)[1] = be64_to_cpu(((const __be64 *)src)[1]);
	}
}

static void copy_and_assign_cidr(struct allowedips_node *node, const u8 *src,
				 u8 cidr, u8 bits)
{
	node->cidr = cidr;
	node->bit_at_a = cidr / 8U;
#ifdef __LITTLE_ENDIAN
	node->bit_at_a ^= (bits / 8U - 1U) % 8U;
#endif
	node->bit_at_b = 7U - (cidr % 8U);
	node->bitlen = bits;
	memcpy(node->bits, src, bits / 8U);
}

static inline u8 choose(struct allowedips_node *node, const u8 *key)
{
	return (key[node->bit_at_a] >> node->bit_at_b) & 1;
}

static void push_rcu(struct allowedips_node **stack,
		     struct allowedips_node __rcu *p, unsigned int *len)
{
	if (rcu_access_pointer(p)) {
		WARN_ON(IS_ENABLED(DEBUG) && *len >= 128);
		stack[(*len)++] = rcu_dereference_raw(p);
	}
}

static void node_free_rcu(struct rcu_head *rcu)
{
	kmem_cache_free(node_cache, container_of(rcu, struct allowedips_node, rcu));
}

static void root_free_rcu(struct rcu_head *rcu)
{
	struct allowedips_node *node, *stack[128] = {
		container_of(rcu, struct allowedips_node, rcu) };
	unsigned int len = 1;

	while (len > 0 && (node = stack[--len])) {
		push_rcu(stack, node->bit[0], &len);
		push_rcu(stack, node->bit[1], &len);
		kmem_cache_free(node_cache, node);
	}
}

static void root_remove_peer_lists(struct allowedips_node *root)
{
	struct allowedips_node *node, *stack[128] = { root };
	unsigned int len = 1;

	while (len > 0 && (node = stack[--len])) {
		push_rcu(stack, node->bit[0], &len);
		push_rcu(stack, node->bit[1], &len);
		if (rcu_access_pointer(node->peer))
			list_del(&node->peer_list);
	}
}

static unsigned int fls128(u64 a, u64 b)
{
	return a ? fls64(a) + 64U : fls64(b);
}

static u8 common_bits(const struct allowedips_node *node, const u8 *key,
		      u8 bits)
{
	if (bits == 32)
		return 32U - fls(*(const u32 *)node->bits ^ *(const u32 *)key);
	else if (bits == 128)
		return 128U - fls128(
			*(const u64 *)&node->bits[0] ^ *(const u64 *)&key[0],
			*(const u64 *)&node->bits[8] ^ *(const u64 *)&key[8]);
	return 0;
}

static bool prefix_matches(const struct allowedips_node *node, const u8 *key,
			   u8 bits)
{
	/* This could be much faster if it actually just compared the common
	 * bits properly, by precomputing a mask bswap(~0 << (32 - cidr)), and
	 * the rest, but it turns out that common_bits is already super fast on
	 * modern processors, even taking into account the unfortunate bswap.
	 * So, we just inline it like this instead.
	 */
	return common_bits(node, key, bits) >= node->cidr;
}

static struct allowedips_node *find_node(struct allowedips_node *trie, u8 bits,
					 const u8 *key)
{
	struct allowedips_node *node = trie, *found = NULL;

	while (node && prefix_matches(node, key, bits)) {
		if (rcu_access_pointer(node->peer))
			found = node;
		if (node->cidr == bits)
			break;
		node = rcu_dereference_bh(node->bit[choose(node, key)]);
	}
	return found;
}

/* Returns a strong reference to a peer */
static struct wg_peer *lookup(struct allowedips_node __rcu *root, u8 bits,
			      const void *be_ip)
{
	/* Aligned so it can be passed to fls/fls64 */
	u8 ip[16] __aligned(__alignof(u64));
	struct allowedips_node *node;
	struct wg_peer *peer = NULL;

	swap_endian(ip, be_ip, bits);

	rcu_read_lock_bh();
retry:
	node = find_node(rcu_dereference_bh(root), bits, ip);
	if (node) {
		peer = wg_peer_get_maybe_zero(rcu_dereference_bh(node->peer));
		if (!peer)
			goto retry;
	}
	rcu_read_unlock_bh();
	return peer;
}

static bool node_placement(struct allowedips_node __rcu *trie, const u8 *key,
			   u8 cidr, u8 bits, struct allowedips_node **rnode,
			   struct mutex *lock)
{
	struct allowedips_node *node = rcu_dereference_protected(trie, lockdep_is_held(lock));
	struct allowedips_node *parent = NULL;
	bool exact = false;

	while (node && node->cidr <= cidr && prefix_matches(node, key, bits)) {
		parent = node;
		if (parent->cidr == cidr) {
			exact = true;
			break;
		}
		node = rcu_dereference_protected(parent->bit[choose(parent, key)], lockdep_is_held(lock));
	}
	*rnode = parent;
	return exact;
}

static inline void connect_node(struct allowedips_node __rcu **parent, u8 bit, struct allowedips_node *node)
{
	node->parent_bit_packed = (unsigned long)parent | bit;
	rcu_assign_pointer(*parent, node);
}

static inline void choose_and_connect_node(struct allowedips_node *parent, struct allowedips_node *node)
{
	u8 bit = choose(parent, node->bits);
	connect_node(&parent->bit[bit], bit, node);
}

static int add(struct allowedips_node __rcu **trie, u8 bits, const u8 *key,
	       u8 cidr, struct wg_peer *peer, struct mutex *lock)
{
	struct allowedips_node *node, *parent, *down, *newnode;

	if (unlikely(cidr > bits || !peer))
		return -EINVAL;

	if (!rcu_access_pointer(*trie)) {
		node = kmem_cache_zalloc(node_cache, GFP_KERNEL);
		if (unlikely(!node))
			return -ENOMEM;
		RCU_INIT_POINTER(node->peer, peer);
		list_add_tail(&node->peer_list, &peer->allowedips_list);
		copy_and_assign_cidr(node, key, cidr, bits);
		connect_node(trie, 2, node);
		return 0;
	}
	if (node_placement(*trie, key, cidr, bits, &node, lock)) {
		rcu_assign_pointer(node->peer, peer);
		list_move_tail(&node->peer_list, &peer->allowedips_list);
		return 0;
	}

	newnode = kmem_cache_zalloc(node_cache, GFP_KERNEL);
	if (unlikely(!newnode))
		return -ENOMEM;
	RCU_INIT_POINTER(newnode->peer, peer);
	list_add_tail(&newnode->peer_list, &peer->allowedips_list);
	copy_and_assign_cidr(newnode, key, cidr, bits);

	if (!node) {
		down = rcu_dereference_protected(*trie, lockdep_is_held(lock));
	} else {
		const u8 bit = choose(node, key);
		down = rcu_dereference_protected(node->bit[bit], lockdep_is_held(lock));
		if (!down) {
			connect_node(&node->bit[bit], bit, newnode);
			return 0;
		}
	}
	cidr = min(cidr, common_bits(down, key, bits));
	parent = node;

	if (newnode->cidr == cidr) {
		choose_and_connect_node(newnode, down);
		if (!parent)
			connect_node(trie, 2, newnode);
		else
			choose_and_connect_node(parent, newnode);
		return 0;
	}

	node = kmem_cache_zalloc(node_cache, GFP_KERNEL);
	if (unlikely(!node)) {
		list_del(&newnode->peer_list);
		kmem_cache_free(node_cache, newnode);
		return -ENOMEM;
	}
	INIT_LIST_HEAD(&node->peer_list);
	copy_and_assign_cidr(node, newnode->bits, cidr, bits);

	choose_and_connect_node(node, down);
	choose_and_connect_node(node, newnode);
	if (!parent)
		connect_node(trie, 2, node);
	else
		choose_and_connect_node(parent, node);
	return 0;
}

void wg_allowedips_init(struct allowedips *table)
{
	table->root4 = table->root6 = NULL;
	table->seq = 1;
}

void wg_allowedips_free(struct allowedips *table, struct mutex *lock)
{
	struct allowedips_node __rcu *old4 = table->root4, *old6 = table->root6;

	++table->seq;
	RCU_INIT_POINTER(table->root4, NULL);
	RCU_INIT_POINTER(table->root6, NULL);
	if (rcu_access_pointer(old4)) {
		struct allowedips_node *node = rcu_dereference_protected(old4,
							lockdep_is_held(lock));

		root_remove_peer_lists(node);
		call_rcu(&node->rcu, root_free_rcu);
	}
	if (rcu_access_pointer(old6)) {
		struct allowedips_node *node = rcu_dereference_protected(old6,
							lockdep_is_held(lock));

		root_remove_peer_lists(node);
		call_rcu(&node->rcu, root_free_rcu);
	}
}

int wg_allowedips_insert_v4(struct allowedips *table, const struct in_addr *ip,
			    u8 cidr, struct wg_peer *peer, struct mutex *lock)
{
	/* Aligned so it can be passed to fls */
	u8 key[4] __aligned(__alignof(u32));

	++table->seq;
	swap_endian(key, (const u8 *)ip, 32);
	return add(&table->root4, 32, key, cidr, peer, lock);
}

int wg_allowedips_insert_v6(struct allowedips *table, const struct in6_addr *ip,
			    u8 cidr, struct wg_peer *peer, struct mutex *lock)
{
	/* Aligned so it can be passed to fls64 */
	u8 key[16] __aligned(__alignof(u64));

	++table->seq;
	swap_endian(key, (const u8 *)ip, 128);
	return add(&table->root6, 128, key, cidr, peer, lock);
}

void wg_allowedips_remove_by_peer(struct allowedips *table,
				  struct wg_peer *peer, struct mutex *lock)
{
	struct allowedips_node *node, *child, **parent_bit, *parent, *tmp;
	bool free_parent;

	if (list_empty(&peer->allowedips_list))
		return;
	++table->seq;
	list_for_each_entry_safe(node, tmp, &peer->allowedips_list, peer_list) {
		list_del_init(&node->peer_list);
		RCU_INIT_POINTER(node->peer, NULL);
		if (node->bit[0] && node->bit[1])
			continue;
		child = rcu_dereference_protected(node->bit[!rcu_access_pointer(node->bit[0])],
						  lockdep_is_held(lock));
		if (child)
			child->parent_bit_packed = node->parent_bit_packed;
		parent_bit = (struct allowedips_node **)(node->parent_bit_packed & ~3UL);
		*parent_bit = child;
		parent = (void *)parent_bit -
			 offsetof(struct allowedips_node, bit[node->parent_bit_packed & 1]);
		free_parent = !rcu_access_pointer(node->bit[0]) &&
			      !rcu_access_pointer(node->bit[1]) &&
			      (node->parent_bit_packed & 3) <= 1 &&
			      !rcu_access_pointer(parent->peer);
		if (free_parent)
			child = rcu_dereference_protected(
					parent->bit[!(node->parent_bit_packed & 1)],
					lockdep_is_held(lock));
		call_rcu(&node->rcu, node_free_rcu);
		if (!free_parent)
			continue;
		if (child)
			child->parent_bit_packed = parent->parent_bit_packed;
		*(struct allowedips_node **)(parent->parent_bit_packed & ~3UL) = child;
		call_rcu(&parent->rcu, node_free_rcu);
	}
}

int wg_allowedips_read_node(struct allowedips_node *node, u8 ip[16], u8 *cidr)
{
	const unsigned int cidr_bytes = DIV_ROUND_UP(node->cidr, 8U);
	swap_endian(ip, node->bits, node->bitlen);
	memset(ip + cidr_bytes, 0, node->bitlen / 8U - cidr_bytes);
	if (node->cidr)
		ip[cidr_bytes - 1U] &= ~0U << (-node->cidr % 8U);

	*cidr = node->cidr;
	return node->bitlen == 32 ? AF_INET : AF_INET6;
}

/* Returns a strong reference to a peer */
struct wg_peer *wg_allowedips_lookup_dst(struct allowedips *table,
					 struct sk_buff *skb)
{
	if (skb->protocol == htons(ETH_P_IP))
		return lookup(table->root4, 32, &ip_hdr(skb)->daddr);
	else if (skb->protocol == htons(ETH_P_IPV6))
		return lookup(table->root6, 128, &ipv6_hdr(skb)->daddr);
	return NULL;
}

/* Returns a strong reference to a peer */
struct wg_peer *wg_allowedips_lookup_src(struct allowedips *table,
					 struct sk_buff *skb)
{
	if (skb->protocol == htons(ETH_P_IP))
		return lookup(table->root4, 32, &ip_hdr(skb)->saddr);
	else if (skb->protocol == htons(ETH_P_IPV6))
		return lookup(table->root6, 128, &ipv6_hdr(skb)->saddr);
	return NULL;
}

int __init wg_allowedips_slab_init(void)
{
	node_cache = KMEM_CACHE(allowedips_node, 0);
	return node_cache ? 0 : -ENOMEM;
}

void wg_allowedips_slab_uninit(void)
{
	rcu_barrier();
	kmem_cache_destroy(node_cache);
}

#include "selftest/allowedips.c"