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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
4 */
5
6#include "allowedips.h"
7#include "peer.h"
8
9static struct kmem_cache *node_cache;
10
11static void swap_endian(u8 *dst, const u8 *src, u8 bits)
12{
13 if (bits == 32) {
14 *(u32 *)dst = be32_to_cpu(*(const __be32 *)src);
15 } else if (bits == 128) {
16 ((u64 *)dst)[0] = be64_to_cpu(((const __be64 *)src)[0]);
17 ((u64 *)dst)[1] = be64_to_cpu(((const __be64 *)src)[1]);
18 }
19}
20
21static void copy_and_assign_cidr(struct allowedips_node *node, const u8 *src,
22 u8 cidr, u8 bits)
23{
24 node->cidr = cidr;
25 node->bit_at_a = cidr / 8U;
26#ifdef __LITTLE_ENDIAN
27 node->bit_at_a ^= (bits / 8U - 1U) % 8U;
28#endif
29 node->bit_at_b = 7U - (cidr % 8U);
30 node->bitlen = bits;
31 memcpy(node->bits, src, bits / 8U);
32}
33
34static inline u8 choose(struct allowedips_node *node, const u8 *key)
35{
36 return (key[node->bit_at_a] >> node->bit_at_b) & 1;
37}
38
39static void push_rcu(struct allowedips_node **stack,
40 struct allowedips_node __rcu *p, unsigned int *len)
41{
42 if (rcu_access_pointer(p)) {
43 WARN_ON(IS_ENABLED(DEBUG) && *len >= 128);
44 stack[(*len)++] = rcu_dereference_raw(p);
45 }
46}
47
48static void node_free_rcu(struct rcu_head *rcu)
49{
50 kmem_cache_free(node_cache, container_of(rcu, struct allowedips_node, rcu));
51}
52
53static void root_free_rcu(struct rcu_head *rcu)
54{
55 struct allowedips_node *node, *stack[128] = {
56 container_of(rcu, struct allowedips_node, rcu) };
57 unsigned int len = 1;
58
59 while (len > 0 && (node = stack[--len])) {
60 push_rcu(stack, node->bit[0], &len);
61 push_rcu(stack, node->bit[1], &len);
62 kmem_cache_free(node_cache, node);
63 }
64}
65
66static void root_remove_peer_lists(struct allowedips_node *root)
67{
68 struct allowedips_node *node, *stack[128] = { root };
69 unsigned int len = 1;
70
71 while (len > 0 && (node = stack[--len])) {
72 push_rcu(stack, node->bit[0], &len);
73 push_rcu(stack, node->bit[1], &len);
74 if (rcu_access_pointer(node->peer))
75 list_del(&node->peer_list);
76 }
77}
78
79static unsigned int fls128(u64 a, u64 b)
80{
81 return a ? fls64(a) + 64U : fls64(b);
82}
83
84static u8 common_bits(const struct allowedips_node *node, const u8 *key,
85 u8 bits)
86{
87 if (bits == 32)
88 return 32U - fls(*(const u32 *)node->bits ^ *(const u32 *)key);
89 else if (bits == 128)
90 return 128U - fls128(
91 *(const u64 *)&node->bits[0] ^ *(const u64 *)&key[0],
92 *(const u64 *)&node->bits[8] ^ *(const u64 *)&key[8]);
93 return 0;
94}
95
96static bool prefix_matches(const struct allowedips_node *node, const u8 *key,
97 u8 bits)
98{
99 /* This could be much faster if it actually just compared the common
100 * bits properly, by precomputing a mask bswap(~0 << (32 - cidr)), and
101 * the rest, but it turns out that common_bits is already super fast on
102 * modern processors, even taking into account the unfortunate bswap.
103 * So, we just inline it like this instead.
104 */
105 return common_bits(node, key, bits) >= node->cidr;
106}
107
108static struct allowedips_node *find_node(struct allowedips_node *trie, u8 bits,
109 const u8 *key)
110{
111 struct allowedips_node *node = trie, *found = NULL;
112
113 while (node && prefix_matches(node, key, bits)) {
114 if (rcu_access_pointer(node->peer))
115 found = node;
116 if (node->cidr == bits)
117 break;
118 node = rcu_dereference_bh(node->bit[choose(node, key)]);
119 }
120 return found;
121}
122
123/* Returns a strong reference to a peer */
124static struct wg_peer *lookup(struct allowedips_node __rcu *root, u8 bits,
125 const void *be_ip)
126{
127 /* Aligned so it can be passed to fls/fls64 */
128 u8 ip[16] __aligned(__alignof(u64));
129 struct allowedips_node *node;
130 struct wg_peer *peer = NULL;
131
132 swap_endian(ip, be_ip, bits);
133
134 rcu_read_lock_bh();
135retry:
136 node = find_node(rcu_dereference_bh(root), bits, ip);
137 if (node) {
138 peer = wg_peer_get_maybe_zero(rcu_dereference_bh(node->peer));
139 if (!peer)
140 goto retry;
141 }
142 rcu_read_unlock_bh();
143 return peer;
144}
145
146static bool node_placement(struct allowedips_node __rcu *trie, const u8 *key,
147 u8 cidr, u8 bits, struct allowedips_node **rnode,
148 struct mutex *lock)
149{
150 struct allowedips_node *node = rcu_dereference_protected(trie, lockdep_is_held(lock));
151 struct allowedips_node *parent = NULL;
152 bool exact = false;
153
154 while (node && node->cidr <= cidr && prefix_matches(node, key, bits)) {
155 parent = node;
156 if (parent->cidr == cidr) {
157 exact = true;
158 break;
159 }
160 node = rcu_dereference_protected(parent->bit[choose(parent, key)], lockdep_is_held(lock));
161 }
162 *rnode = parent;
163 return exact;
164}
165
166static inline void connect_node(struct allowedips_node **parent, u8 bit, struct allowedips_node *node)
167{
168 node->parent_bit_packed = (unsigned long)parent | bit;
169 rcu_assign_pointer(*parent, node);
170}
171
172static inline void choose_and_connect_node(struct allowedips_node *parent, struct allowedips_node *node)
173{
174 u8 bit = choose(parent, node->bits);
175 connect_node(&parent->bit[bit], bit, node);
176}
177
178static int add(struct allowedips_node __rcu **trie, u8 bits, const u8 *key,
179 u8 cidr, struct wg_peer *peer, struct mutex *lock)
180{
181 struct allowedips_node *node, *parent, *down, *newnode;
182
183 if (unlikely(cidr > bits || !peer))
184 return -EINVAL;
185
186 if (!rcu_access_pointer(*trie)) {
187 node = kmem_cache_zalloc(node_cache, GFP_KERNEL);
188 if (unlikely(!node))
189 return -ENOMEM;
190 RCU_INIT_POINTER(node->peer, peer);
191 list_add_tail(&node->peer_list, &peer->allowedips_list);
192 copy_and_assign_cidr(node, key, cidr, bits);
193 connect_node(trie, 2, node);
194 return 0;
195 }
196 if (node_placement(*trie, key, cidr, bits, &node, lock)) {
197 rcu_assign_pointer(node->peer, peer);
198 list_move_tail(&node->peer_list, &peer->allowedips_list);
199 return 0;
200 }
201
202 newnode = kmem_cache_zalloc(node_cache, GFP_KERNEL);
203 if (unlikely(!newnode))
204 return -ENOMEM;
205 RCU_INIT_POINTER(newnode->peer, peer);
206 list_add_tail(&newnode->peer_list, &peer->allowedips_list);
207 copy_and_assign_cidr(newnode, key, cidr, bits);
208
209 if (!node) {
210 down = rcu_dereference_protected(*trie, lockdep_is_held(lock));
211 } else {
212 const u8 bit = choose(node, key);
213 down = rcu_dereference_protected(node->bit[bit], lockdep_is_held(lock));
214 if (!down) {
215 connect_node(&node->bit[bit], bit, newnode);
216 return 0;
217 }
218 }
219 cidr = min(cidr, common_bits(down, key, bits));
220 parent = node;
221
222 if (newnode->cidr == cidr) {
223 choose_and_connect_node(newnode, down);
224 if (!parent)
225 connect_node(trie, 2, newnode);
226 else
227 choose_and_connect_node(parent, newnode);
228 return 0;
229 }
230
231 node = kmem_cache_zalloc(node_cache, GFP_KERNEL);
232 if (unlikely(!node)) {
233 list_del(&newnode->peer_list);
234 kmem_cache_free(node_cache, newnode);
235 return -ENOMEM;
236 }
237 INIT_LIST_HEAD(&node->peer_list);
238 copy_and_assign_cidr(node, newnode->bits, cidr, bits);
239
240 choose_and_connect_node(node, down);
241 choose_and_connect_node(node, newnode);
242 if (!parent)
243 connect_node(trie, 2, node);
244 else
245 choose_and_connect_node(parent, node);
246 return 0;
247}
248
249void wg_allowedips_init(struct allowedips *table)
250{
251 table->root4 = table->root6 = NULL;
252 table->seq = 1;
253}
254
255void wg_allowedips_free(struct allowedips *table, struct mutex *lock)
256{
257 struct allowedips_node __rcu *old4 = table->root4, *old6 = table->root6;
258
259 ++table->seq;
260 RCU_INIT_POINTER(table->root4, NULL);
261 RCU_INIT_POINTER(table->root6, NULL);
262 if (rcu_access_pointer(old4)) {
263 struct allowedips_node *node = rcu_dereference_protected(old4,
264 lockdep_is_held(lock));
265
266 root_remove_peer_lists(node);
267 call_rcu(&node->rcu, root_free_rcu);
268 }
269 if (rcu_access_pointer(old6)) {
270 struct allowedips_node *node = rcu_dereference_protected(old6,
271 lockdep_is_held(lock));
272
273 root_remove_peer_lists(node);
274 call_rcu(&node->rcu, root_free_rcu);
275 }
276}
277
278int wg_allowedips_insert_v4(struct allowedips *table, const struct in_addr *ip,
279 u8 cidr, struct wg_peer *peer, struct mutex *lock)
280{
281 /* Aligned so it can be passed to fls */
282 u8 key[4] __aligned(__alignof(u32));
283
284 ++table->seq;
285 swap_endian(key, (const u8 *)ip, 32);
286 return add(&table->root4, 32, key, cidr, peer, lock);
287}
288
289int wg_allowedips_insert_v6(struct allowedips *table, const struct in6_addr *ip,
290 u8 cidr, struct wg_peer *peer, struct mutex *lock)
291{
292 /* Aligned so it can be passed to fls64 */
293 u8 key[16] __aligned(__alignof(u64));
294
295 ++table->seq;
296 swap_endian(key, (const u8 *)ip, 128);
297 return add(&table->root6, 128, key, cidr, peer, lock);
298}
299
300void wg_allowedips_remove_by_peer(struct allowedips *table,
301 struct wg_peer *peer, struct mutex *lock)
302{
303 struct allowedips_node *node, *child, **parent_bit, *parent, *tmp;
304 bool free_parent;
305
306 if (list_empty(&peer->allowedips_list))
307 return;
308 ++table->seq;
309 list_for_each_entry_safe(node, tmp, &peer->allowedips_list, peer_list) {
310 list_del_init(&node->peer_list);
311 RCU_INIT_POINTER(node->peer, NULL);
312 if (node->bit[0] && node->bit[1])
313 continue;
314 child = rcu_dereference_protected(node->bit[!rcu_access_pointer(node->bit[0])],
315 lockdep_is_held(lock));
316 if (child)
317 child->parent_bit_packed = node->parent_bit_packed;
318 parent_bit = (struct allowedips_node **)(node->parent_bit_packed & ~3UL);
319 *parent_bit = child;
320 parent = (void *)parent_bit -
321 offsetof(struct allowedips_node, bit[node->parent_bit_packed & 1]);
322 free_parent = !rcu_access_pointer(node->bit[0]) &&
323 !rcu_access_pointer(node->bit[1]) &&
324 (node->parent_bit_packed & 3) <= 1 &&
325 !rcu_access_pointer(parent->peer);
326 if (free_parent)
327 child = rcu_dereference_protected(
328 parent->bit[!(node->parent_bit_packed & 1)],
329 lockdep_is_held(lock));
330 call_rcu(&node->rcu, node_free_rcu);
331 if (!free_parent)
332 continue;
333 if (child)
334 child->parent_bit_packed = parent->parent_bit_packed;
335 *(struct allowedips_node **)(parent->parent_bit_packed & ~3UL) = child;
336 call_rcu(&parent->rcu, node_free_rcu);
337 }
338}
339
340int wg_allowedips_read_node(struct allowedips_node *node, u8 ip[16], u8 *cidr)
341{
342 const unsigned int cidr_bytes = DIV_ROUND_UP(node->cidr, 8U);
343 swap_endian(ip, node->bits, node->bitlen);
344 memset(ip + cidr_bytes, 0, node->bitlen / 8U - cidr_bytes);
345 if (node->cidr)
346 ip[cidr_bytes - 1U] &= ~0U << (-node->cidr % 8U);
347
348 *cidr = node->cidr;
349 return node->bitlen == 32 ? AF_INET : AF_INET6;
350}
351
352/* Returns a strong reference to a peer */
353struct wg_peer *wg_allowedips_lookup_dst(struct allowedips *table,
354 struct sk_buff *skb)
355{
356 if (skb->protocol == htons(ETH_P_IP))
357 return lookup(table->root4, 32, &ip_hdr(skb)->daddr);
358 else if (skb->protocol == htons(ETH_P_IPV6))
359 return lookup(table->root6, 128, &ipv6_hdr(skb)->daddr);
360 return NULL;
361}
362
363/* Returns a strong reference to a peer */
364struct wg_peer *wg_allowedips_lookup_src(struct allowedips *table,
365 struct sk_buff *skb)
366{
367 if (skb->protocol == htons(ETH_P_IP))
368 return lookup(table->root4, 32, &ip_hdr(skb)->saddr);
369 else if (skb->protocol == htons(ETH_P_IPV6))
370 return lookup(table->root6, 128, &ipv6_hdr(skb)->saddr);
371 return NULL;
372}
373
374int __init wg_allowedips_slab_init(void)
375{
376 node_cache = KMEM_CACHE(allowedips_node, 0);
377 return node_cache ? 0 : -ENOMEM;
378}
379
380void wg_allowedips_slab_uninit(void)
381{
382 rcu_barrier();
383 kmem_cache_destroy(node_cache);
384}
385
386#include "selftest/allowedips.c"