summaryrefslogtreecommitdiff
path: root/kernel/bpf/reuseport_array.c
blob: 4838922f723ddab66879e17aa4c341dc6fe2d406 (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
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2018 Facebook
 */
#include <linux/bpf.h>
#include <linux/err.h>
#include <linux/sock_diag.h>
#include <net/sock_reuseport.h>

struct reuseport_array {
	struct bpf_map map;
	struct sock __rcu *ptrs[];
};

static struct reuseport_array *reuseport_array(struct bpf_map *map)
{
	return (struct reuseport_array *)map;
}

/* The caller must hold the reuseport_lock */
void bpf_sk_reuseport_detach(struct sock *sk)
{
	uintptr_t sk_user_data;

	write_lock_bh(&sk->sk_callback_lock);
	sk_user_data = (uintptr_t)sk->sk_user_data;
	if (sk_user_data & SK_USER_DATA_BPF) {
		struct sock __rcu **socks;

		socks = (void *)(sk_user_data & SK_USER_DATA_PTRMASK);
		WRITE_ONCE(sk->sk_user_data, NULL);
		/*
		 * Do not move this NULL assignment outside of
		 * sk->sk_callback_lock because there is
		 * a race with reuseport_array_free()
		 * which does not hold the reuseport_lock.
		 */
		RCU_INIT_POINTER(*socks, NULL);
	}
	write_unlock_bh(&sk->sk_callback_lock);
}

static int reuseport_array_alloc_check(union bpf_attr *attr)
{
	if (attr->value_size != sizeof(u32) &&
	    attr->value_size != sizeof(u64))
		return -EINVAL;

	return array_map_alloc_check(attr);
}

static void *reuseport_array_lookup_elem(struct bpf_map *map, void *key)
{
	struct reuseport_array *array = reuseport_array(map);
	u32 index = *(u32 *)key;

	if (unlikely(index >= array->map.max_entries))
		return NULL;

	return rcu_dereference(array->ptrs[index]);
}

/* Called from syscall only */
static int reuseport_array_delete_elem(struct bpf_map *map, void *key)
{
	struct reuseport_array *array = reuseport_array(map);
	u32 index = *(u32 *)key;
	struct sock *sk;
	int err;

	if (index >= map->max_entries)
		return -E2BIG;

	if (!rcu_access_pointer(array->ptrs[index]))
		return -ENOENT;

	spin_lock_bh(&reuseport_lock);

	sk = rcu_dereference_protected(array->ptrs[index],
				       lockdep_is_held(&reuseport_lock));
	if (sk) {
		write_lock_bh(&sk->sk_callback_lock);
		WRITE_ONCE(sk->sk_user_data, NULL);
		RCU_INIT_POINTER(array->ptrs[index], NULL);
		write_unlock_bh(&sk->sk_callback_lock);
		err = 0;
	} else {
		err = -ENOENT;
	}

	spin_unlock_bh(&reuseport_lock);

	return err;
}

static void reuseport_array_free(struct bpf_map *map)
{
	struct reuseport_array *array = reuseport_array(map);
	struct sock *sk;
	u32 i;

	/*
	 * ops->map_*_elem() will not be able to access this
	 * array now. Hence, this function only races with
	 * bpf_sk_reuseport_detach() which was triggerred by
	 * close() or disconnect().
	 *
	 * This function and bpf_sk_reuseport_detach() are
	 * both removing sk from "array".  Who removes it
	 * first does not matter.
	 *
	 * The only concern here is bpf_sk_reuseport_detach()
	 * may access "array" which is being freed here.
	 * bpf_sk_reuseport_detach() access this "array"
	 * through sk->sk_user_data _and_ with sk->sk_callback_lock
	 * held which is enough because this "array" is not freed
	 * until all sk->sk_user_data has stopped referencing this "array".
	 *
	 * Hence, due to the above, taking "reuseport_lock" is not
	 * needed here.
	 */

	/*
	 * Since reuseport_lock is not taken, sk is accessed under
	 * rcu_read_lock()
	 */
	rcu_read_lock();
	for (i = 0; i < map->max_entries; i++) {
		sk = rcu_dereference(array->ptrs[i]);
		if (sk) {
			write_lock_bh(&sk->sk_callback_lock);
			/*
			 * No need for WRITE_ONCE(). At this point,
			 * no one is reading it without taking the
			 * sk->sk_callback_lock.
			 */
			sk->sk_user_data = NULL;
			write_unlock_bh(&sk->sk_callback_lock);
			RCU_INIT_POINTER(array->ptrs[i], NULL);
		}
	}
	rcu_read_unlock();

	/*
	 * Once reaching here, all sk->sk_user_data is not
	 * referenceing this "array".  "array" can be freed now.
	 */
	bpf_map_area_free(array);
}

static struct bpf_map *reuseport_array_alloc(union bpf_attr *attr)
{
	int numa_node = bpf_map_attr_numa_node(attr);
	struct reuseport_array *array;
	u64 array_size;

	if (!bpf_capable())
		return ERR_PTR(-EPERM);

	array_size = sizeof(*array);
	array_size += (u64)attr->max_entries * sizeof(struct sock *);

	/* allocate all map elements and zero-initialize them */
	array = bpf_map_area_alloc(array_size, numa_node);
	if (!array)
		return ERR_PTR(-ENOMEM);

	/* copy mandatory map attributes */
	bpf_map_init_from_attr(&array->map, attr);

	return &array->map;
}

int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key,
				       void *value)
{
	struct sock *sk;
	int err;

	if (map->value_size != sizeof(u64))
		return -ENOSPC;

	rcu_read_lock();
	sk = reuseport_array_lookup_elem(map, key);
	if (sk) {
		*(u64 *)value = __sock_gen_cookie(sk);
		err = 0;
	} else {
		err = -ENOENT;
	}
	rcu_read_unlock();

	return err;
}

static int
reuseport_array_update_check(const struct reuseport_array *array,
			     const struct sock *nsk,
			     const struct sock *osk,
			     const struct sock_reuseport *nsk_reuse,
			     u32 map_flags)
{
	if (osk && map_flags == BPF_NOEXIST)
		return -EEXIST;

	if (!osk && map_flags == BPF_EXIST)
		return -ENOENT;

	if (nsk->sk_protocol != IPPROTO_UDP && nsk->sk_protocol != IPPROTO_TCP)
		return -ENOTSUPP;

	if (nsk->sk_family != AF_INET && nsk->sk_family != AF_INET6)
		return -ENOTSUPP;

	if (nsk->sk_type != SOCK_STREAM && nsk->sk_type != SOCK_DGRAM)
		return -ENOTSUPP;

	/*
	 * sk must be hashed (i.e. listening in the TCP case or binded
	 * in the UDP case) and
	 * it must also be a SO_REUSEPORT sk (i.e. reuse cannot be NULL).
	 *
	 * Also, sk will be used in bpf helper that is protected by
	 * rcu_read_lock().
	 */
	if (!sock_flag(nsk, SOCK_RCU_FREE) || !sk_hashed(nsk) || !nsk_reuse)
		return -EINVAL;

	/* READ_ONCE because the sk->sk_callback_lock may not be held here */
	if (READ_ONCE(nsk->sk_user_data))
		return -EBUSY;

	return 0;
}

/*
 * Called from syscall only.
 * The "nsk" in the fd refcnt.
 * The "osk" and "reuse" are protected by reuseport_lock.
 */
int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
				       void *value, u64 map_flags)
{
	struct reuseport_array *array = reuseport_array(map);
	struct sock *free_osk = NULL, *osk, *nsk;
	struct sock_reuseport *reuse;
	u32 index = *(u32 *)key;
	uintptr_t sk_user_data;
	struct socket *socket;
	int err, fd;

	if (map_flags > BPF_EXIST)
		return -EINVAL;

	if (index >= map->max_entries)
		return -E2BIG;

	if (map->value_size == sizeof(u64)) {
		u64 fd64 = *(u64 *)value;

		if (fd64 > S32_MAX)
			return -EINVAL;
		fd = fd64;
	} else {
		fd = *(int *)value;
	}

	socket = sockfd_lookup(fd, &err);
	if (!socket)
		return err;

	nsk = socket->sk;
	if (!nsk) {
		err = -EINVAL;
		goto put_file;
	}

	/* Quick checks before taking reuseport_lock */
	err = reuseport_array_update_check(array, nsk,
					   rcu_access_pointer(array->ptrs[index]),
					   rcu_access_pointer(nsk->sk_reuseport_cb),
					   map_flags);
	if (err)
		goto put_file;

	spin_lock_bh(&reuseport_lock);
	/*
	 * Some of the checks only need reuseport_lock
	 * but it is done under sk_callback_lock also
	 * for simplicity reason.
	 */
	write_lock_bh(&nsk->sk_callback_lock);

	osk = rcu_dereference_protected(array->ptrs[index],
					lockdep_is_held(&reuseport_lock));
	reuse = rcu_dereference_protected(nsk->sk_reuseport_cb,
					  lockdep_is_held(&reuseport_lock));
	err = reuseport_array_update_check(array, nsk, osk, reuse, map_flags);
	if (err)
		goto put_file_unlock;

	sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY |
		SK_USER_DATA_BPF;
	WRITE_ONCE(nsk->sk_user_data, (void *)sk_user_data);
	rcu_assign_pointer(array->ptrs[index], nsk);
	free_osk = osk;
	err = 0;

put_file_unlock:
	write_unlock_bh(&nsk->sk_callback_lock);

	if (free_osk) {
		write_lock_bh(&free_osk->sk_callback_lock);
		WRITE_ONCE(free_osk->sk_user_data, NULL);
		write_unlock_bh(&free_osk->sk_callback_lock);
	}

	spin_unlock_bh(&reuseport_lock);
put_file:
	fput(socket->file);
	return err;
}

/* Called from syscall */
static int reuseport_array_get_next_key(struct bpf_map *map, void *key,
					void *next_key)
{
	struct reuseport_array *array = reuseport_array(map);
	u32 index = key ? *(u32 *)key : U32_MAX;
	u32 *next = (u32 *)next_key;

	if (index >= array->map.max_entries) {
		*next = 0;
		return 0;
	}

	if (index == array->map.max_entries - 1)
		return -ENOENT;

	*next = index + 1;
	return 0;
}

static int reuseport_array_map_btf_id;
const struct bpf_map_ops reuseport_array_ops = {
	.map_meta_equal = bpf_map_meta_equal,
	.map_alloc_check = reuseport_array_alloc_check,
	.map_alloc = reuseport_array_alloc,
	.map_free = reuseport_array_free,
	.map_lookup_elem = reuseport_array_lookup_elem,
	.map_get_next_key = reuseport_array_get_next_key,
	.map_delete_elem = reuseport_array_delete_elem,
	.map_btf_name = "reuseport_array",
	.map_btf_id = &reuseport_array_map_btf_id,
};