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
9 enum { MAX_ALLOWEDIPS_DEPTH = 129 };
10
11 static struct kmem_cache *node_cache;
12
swap_endian(u8 * dst,const u8 * src,u8 bits)13 static void swap_endian(u8 *dst, const u8 *src, u8 bits)
14 {
15 if (bits == 32) {
16 *(u32 *)dst = be32_to_cpu(*(const __be32 *)src);
17 } else if (bits == 128) {
18 ((u64 *)dst)[0] = be64_to_cpu(((const __be64 *)src)[0]);
19 ((u64 *)dst)[1] = be64_to_cpu(((const __be64 *)src)[1]);
20 }
21 }
22
copy_and_assign_cidr(struct allowedips_node * node,const u8 * src,u8 cidr,u8 bits)23 static void copy_and_assign_cidr(struct allowedips_node *node, const u8 *src,
24 u8 cidr, u8 bits)
25 {
26 node->cidr = cidr;
27 node->bit_at_a = cidr / 8U;
28 #ifdef __LITTLE_ENDIAN
29 node->bit_at_a ^= (bits / 8U - 1U) % 8U;
30 #endif
31 node->bit_at_b = 7U - (cidr % 8U);
32 node->bitlen = bits;
33 memcpy(node->bits, src, bits / 8U);
34 }
35
choose(struct allowedips_node * node,const u8 * key)36 static inline u8 choose(struct allowedips_node *node, const u8 *key)
37 {
38 return (key[node->bit_at_a] >> node->bit_at_b) & 1;
39 }
40
push_rcu(struct allowedips_node ** stack,struct allowedips_node __rcu * p,unsigned int * len)41 static void push_rcu(struct allowedips_node **stack,
42 struct allowedips_node __rcu *p, unsigned int *len)
43 {
44 if (rcu_access_pointer(p)) {
45 if (WARN_ON(IS_ENABLED(DEBUG) && *len >= MAX_ALLOWEDIPS_DEPTH))
46 return;
47 stack[(*len)++] = rcu_dereference_raw(p);
48 }
49 }
50
node_free_rcu(struct rcu_head * rcu)51 static void node_free_rcu(struct rcu_head *rcu)
52 {
53 kmem_cache_free(node_cache, container_of(rcu, struct allowedips_node, rcu));
54 }
55
root_free_rcu(struct rcu_head * rcu)56 static void root_free_rcu(struct rcu_head *rcu)
57 {
58 struct allowedips_node *node, *stack[MAX_ALLOWEDIPS_DEPTH] = {
59 container_of(rcu, struct allowedips_node, rcu) };
60 unsigned int len = 1;
61
62 while (len > 0 && (node = stack[--len])) {
63 push_rcu(stack, node->bit[0], &len);
64 push_rcu(stack, node->bit[1], &len);
65 kmem_cache_free(node_cache, node);
66 }
67 }
68
root_remove_peer_lists(struct allowedips_node * root)69 static void root_remove_peer_lists(struct allowedips_node *root)
70 {
71 struct allowedips_node *node, *stack[MAX_ALLOWEDIPS_DEPTH] = { root };
72 unsigned int len = 1;
73
74 while (len > 0 && (node = stack[--len])) {
75 push_rcu(stack, node->bit[0], &len);
76 push_rcu(stack, node->bit[1], &len);
77 if (rcu_access_pointer(node->peer))
78 list_del(&node->peer_list);
79 }
80 }
81
fls128(u64 a,u64 b)82 static unsigned int fls128(u64 a, u64 b)
83 {
84 return a ? fls64(a) + 64U : fls64(b);
85 }
86
common_bits(const struct allowedips_node * node,const u8 * key,u8 bits)87 static u8 common_bits(const struct allowedips_node *node, const u8 *key,
88 u8 bits)
89 {
90 if (bits == 32)
91 return 32U - fls(*(const u32 *)node->bits ^ *(const u32 *)key);
92 else if (bits == 128)
93 return 128U - fls128(
94 *(const u64 *)&node->bits[0] ^ *(const u64 *)&key[0],
95 *(const u64 *)&node->bits[8] ^ *(const u64 *)&key[8]);
96 return 0;
97 }
98
prefix_matches(const struct allowedips_node * node,const u8 * key,u8 bits)99 static bool prefix_matches(const struct allowedips_node *node, const u8 *key,
100 u8 bits)
101 {
102 /* This could be much faster if it actually just compared the common
103 * bits properly, by precomputing a mask bswap(~0 << (32 - cidr)), and
104 * the rest, but it turns out that common_bits is already super fast on
105 * modern processors, even taking into account the unfortunate bswap.
106 * So, we just inline it like this instead.
107 */
108 return common_bits(node, key, bits) >= node->cidr;
109 }
110
find_node(struct allowedips_node * trie,u8 bits,const u8 * key)111 static struct allowedips_node *find_node(struct allowedips_node *trie, u8 bits,
112 const u8 *key)
113 {
114 struct allowedips_node *node = trie, *found = NULL;
115
116 while (node && prefix_matches(node, key, bits)) {
117 if (rcu_access_pointer(node->peer))
118 found = node;
119 if (node->cidr == bits)
120 break;
121 node = rcu_dereference_bh(node->bit[choose(node, key)]);
122 }
123 return found;
124 }
125
126 /* Returns a strong reference to a peer */
lookup(struct allowedips_node __rcu * root,u8 bits,const void * be_ip)127 static struct wg_peer *lookup(struct allowedips_node __rcu *root, u8 bits,
128 const void *be_ip)
129 {
130 /* Aligned so it can be passed to fls/fls64 */
131 u8 ip[16] __aligned(__alignof(u64));
132 struct allowedips_node *node;
133 struct wg_peer *peer = NULL;
134
135 swap_endian(ip, be_ip, bits);
136
137 rcu_read_lock_bh();
138 retry:
139 node = find_node(rcu_dereference_bh(root), bits, ip);
140 if (node) {
141 peer = wg_peer_get_maybe_zero(rcu_dereference_bh(node->peer));
142 if (!peer)
143 goto retry;
144 }
145 rcu_read_unlock_bh();
146 return peer;
147 }
148
node_placement(struct allowedips_node __rcu * trie,const u8 * key,u8 cidr,u8 bits,struct allowedips_node ** rnode,struct mutex * lock)149 static bool node_placement(struct allowedips_node __rcu *trie, const u8 *key,
150 u8 cidr, u8 bits, struct allowedips_node **rnode,
151 struct mutex *lock)
152 {
153 struct allowedips_node *node = rcu_dereference_protected(trie, lockdep_is_held(lock));
154 struct allowedips_node *parent = NULL;
155 bool exact = false;
156
157 while (node && node->cidr <= cidr && prefix_matches(node, key, bits)) {
158 parent = node;
159 if (parent->cidr == cidr) {
160 exact = true;
161 break;
162 }
163 node = rcu_dereference_protected(parent->bit[choose(parent, key)], lockdep_is_held(lock));
164 }
165 *rnode = parent;
166 return exact;
167 }
168
connect_node(struct allowedips_node __rcu ** parent,u8 bit,struct allowedips_node * node)169 static inline void connect_node(struct allowedips_node __rcu **parent, u8 bit, struct allowedips_node *node)
170 {
171 node->parent_bit_packed = (unsigned long)parent | bit;
172 rcu_assign_pointer(*parent, node);
173 }
174
choose_and_connect_node(struct allowedips_node * parent,struct allowedips_node * node)175 static inline void choose_and_connect_node(struct allowedips_node *parent, struct allowedips_node *node)
176 {
177 u8 bit = choose(parent, node->bits);
178 connect_node(&parent->bit[bit], bit, node);
179 }
180
add(struct allowedips_node __rcu ** trie,u8 bits,const u8 * key,u8 cidr,struct wg_peer * peer,struct mutex * lock)181 static int add(struct allowedips_node __rcu **trie, u8 bits, const u8 *key,
182 u8 cidr, struct wg_peer *peer, struct mutex *lock)
183 {
184 struct allowedips_node *node, *parent, *down, *newnode;
185
186 if (unlikely(cidr > bits || !peer))
187 return -EINVAL;
188
189 if (!rcu_access_pointer(*trie)) {
190 node = kmem_cache_zalloc(node_cache, GFP_KERNEL);
191 if (unlikely(!node))
192 return -ENOMEM;
193 RCU_INIT_POINTER(node->peer, peer);
194 list_add_tail(&node->peer_list, &peer->allowedips_list);
195 copy_and_assign_cidr(node, key, cidr, bits);
196 connect_node(trie, 2, node);
197 return 0;
198 }
199 if (node_placement(*trie, key, cidr, bits, &node, lock)) {
200 rcu_assign_pointer(node->peer, peer);
201 list_move_tail(&node->peer_list, &peer->allowedips_list);
202 return 0;
203 }
204
205 newnode = kmem_cache_zalloc(node_cache, GFP_KERNEL);
206 if (unlikely(!newnode))
207 return -ENOMEM;
208 RCU_INIT_POINTER(newnode->peer, peer);
209 list_add_tail(&newnode->peer_list, &peer->allowedips_list);
210 copy_and_assign_cidr(newnode, key, cidr, bits);
211
212 if (!node) {
213 down = rcu_dereference_protected(*trie, lockdep_is_held(lock));
214 } else {
215 const u8 bit = choose(node, key);
216 down = rcu_dereference_protected(node->bit[bit], lockdep_is_held(lock));
217 if (!down) {
218 connect_node(&node->bit[bit], bit, newnode);
219 return 0;
220 }
221 }
222 cidr = min(cidr, common_bits(down, key, bits));
223 parent = node;
224
225 if (newnode->cidr == cidr) {
226 choose_and_connect_node(newnode, down);
227 if (!parent)
228 connect_node(trie, 2, newnode);
229 else
230 choose_and_connect_node(parent, newnode);
231 return 0;
232 }
233
234 node = kmem_cache_zalloc(node_cache, GFP_KERNEL);
235 if (unlikely(!node)) {
236 list_del(&newnode->peer_list);
237 kmem_cache_free(node_cache, newnode);
238 return -ENOMEM;
239 }
240 INIT_LIST_HEAD(&node->peer_list);
241 copy_and_assign_cidr(node, newnode->bits, cidr, bits);
242
243 choose_and_connect_node(node, down);
244 choose_and_connect_node(node, newnode);
245 if (!parent)
246 connect_node(trie, 2, node);
247 else
248 choose_and_connect_node(parent, node);
249 return 0;
250 }
251
wg_allowedips_init(struct allowedips * table)252 void wg_allowedips_init(struct allowedips *table)
253 {
254 table->root4 = table->root6 = NULL;
255 table->seq = 1;
256 }
257
wg_allowedips_free(struct allowedips * table,struct mutex * lock)258 void wg_allowedips_free(struct allowedips *table, struct mutex *lock)
259 {
260 struct allowedips_node __rcu *old4 = table->root4, *old6 = table->root6;
261
262 ++table->seq;
263 RCU_INIT_POINTER(table->root4, NULL);
264 RCU_INIT_POINTER(table->root6, NULL);
265 if (rcu_access_pointer(old4)) {
266 struct allowedips_node *node = rcu_dereference_protected(old4,
267 lockdep_is_held(lock));
268
269 root_remove_peer_lists(node);
270 call_rcu(&node->rcu, root_free_rcu);
271 }
272 if (rcu_access_pointer(old6)) {
273 struct allowedips_node *node = rcu_dereference_protected(old6,
274 lockdep_is_held(lock));
275
276 root_remove_peer_lists(node);
277 call_rcu(&node->rcu, root_free_rcu);
278 }
279 }
280
wg_allowedips_insert_v4(struct allowedips * table,const struct in_addr * ip,u8 cidr,struct wg_peer * peer,struct mutex * lock)281 int wg_allowedips_insert_v4(struct allowedips *table, const struct in_addr *ip,
282 u8 cidr, struct wg_peer *peer, struct mutex *lock)
283 {
284 /* Aligned so it can be passed to fls */
285 u8 key[4] __aligned(__alignof(u32));
286
287 ++table->seq;
288 swap_endian(key, (const u8 *)ip, 32);
289 return add(&table->root4, 32, key, cidr, peer, lock);
290 }
291
wg_allowedips_insert_v6(struct allowedips * table,const struct in6_addr * ip,u8 cidr,struct wg_peer * peer,struct mutex * lock)292 int wg_allowedips_insert_v6(struct allowedips *table, const struct in6_addr *ip,
293 u8 cidr, struct wg_peer *peer, struct mutex *lock)
294 {
295 /* Aligned so it can be passed to fls64 */
296 u8 key[16] __aligned(__alignof(u64));
297
298 ++table->seq;
299 swap_endian(key, (const u8 *)ip, 128);
300 return add(&table->root6, 128, key, cidr, peer, lock);
301 }
302
wg_allowedips_remove_by_peer(struct allowedips * table,struct wg_peer * peer,struct mutex * lock)303 void wg_allowedips_remove_by_peer(struct allowedips *table,
304 struct wg_peer *peer, struct mutex *lock)
305 {
306 struct allowedips_node *node, *child, **parent_bit, *parent, *tmp;
307 bool free_parent;
308
309 if (list_empty(&peer->allowedips_list))
310 return;
311 ++table->seq;
312 list_for_each_entry_safe(node, tmp, &peer->allowedips_list, peer_list) {
313 list_del_init(&node->peer_list);
314 RCU_INIT_POINTER(node->peer, NULL);
315 if (node->bit[0] && node->bit[1])
316 continue;
317 child = rcu_dereference_protected(node->bit[!rcu_access_pointer(node->bit[0])],
318 lockdep_is_held(lock));
319 if (child)
320 child->parent_bit_packed = node->parent_bit_packed;
321 parent_bit = (struct allowedips_node **)(node->parent_bit_packed & ~3UL);
322 *parent_bit = child;
323 parent = (void *)parent_bit -
324 offsetof(struct allowedips_node, bit[node->parent_bit_packed & 1]);
325 free_parent = !rcu_access_pointer(node->bit[0]) &&
326 !rcu_access_pointer(node->bit[1]) &&
327 (node->parent_bit_packed & 3) <= 1 &&
328 !rcu_access_pointer(parent->peer);
329 if (free_parent)
330 child = rcu_dereference_protected(
331 parent->bit[!(node->parent_bit_packed & 1)],
332 lockdep_is_held(lock));
333 call_rcu(&node->rcu, node_free_rcu);
334 if (!free_parent)
335 continue;
336 if (child)
337 child->parent_bit_packed = parent->parent_bit_packed;
338 *(struct allowedips_node **)(parent->parent_bit_packed & ~3UL) = child;
339 call_rcu(&parent->rcu, node_free_rcu);
340 }
341 }
342
wg_allowedips_read_node(struct allowedips_node * node,u8 ip[16],u8 * cidr)343 int wg_allowedips_read_node(struct allowedips_node *node, u8 ip[16], u8 *cidr)
344 {
345 const unsigned int cidr_bytes = DIV_ROUND_UP(node->cidr, 8U);
346 swap_endian(ip, node->bits, node->bitlen);
347 memset(ip + cidr_bytes, 0, node->bitlen / 8U - cidr_bytes);
348 if (node->cidr)
349 ip[cidr_bytes - 1U] &= ~0U << (-node->cidr % 8U);
350
351 *cidr = node->cidr;
352 return node->bitlen == 32 ? AF_INET : AF_INET6;
353 }
354
355 /* Returns a strong reference to a peer */
wg_allowedips_lookup_dst(struct allowedips * table,struct sk_buff * skb)356 struct wg_peer *wg_allowedips_lookup_dst(struct allowedips *table,
357 struct sk_buff *skb)
358 {
359 if (skb->protocol == htons(ETH_P_IP))
360 return lookup(table->root4, 32, &ip_hdr(skb)->daddr);
361 else if (skb->protocol == htons(ETH_P_IPV6))
362 return lookup(table->root6, 128, &ipv6_hdr(skb)->daddr);
363 return NULL;
364 }
365
366 /* Returns a strong reference to a peer */
wg_allowedips_lookup_src(struct allowedips * table,struct sk_buff * skb)367 struct wg_peer *wg_allowedips_lookup_src(struct allowedips *table,
368 struct sk_buff *skb)
369 {
370 if (skb->protocol == htons(ETH_P_IP))
371 return lookup(table->root4, 32, &ip_hdr(skb)->saddr);
372 else if (skb->protocol == htons(ETH_P_IPV6))
373 return lookup(table->root6, 128, &ipv6_hdr(skb)->saddr);
374 return NULL;
375 }
376
wg_allowedips_slab_init(void)377 int __init wg_allowedips_slab_init(void)
378 {
379 node_cache = KMEM_CACHE(allowedips_node, 0);
380 return node_cache ? 0 : -ENOMEM;
381 }
382
wg_allowedips_slab_uninit(void)383 void wg_allowedips_slab_uninit(void)
384 {
385 rcu_barrier();
386 kmem_cache_destroy(node_cache);
387 }
388
389 #include "selftest/allowedips.c"
390