1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (c) 2018 Facebook
7 #include <linux/sock_diag.h>
8 #include <net/sock_reuseport.h>
10 struct reuseport_array {
12 struct sock __rcu *ptrs[];
15 static struct reuseport_array *reuseport_array(struct bpf_map *map)
17 return (struct reuseport_array *)map;
20 /* The caller must hold the reuseport_lock */
21 void bpf_sk_reuseport_detach(struct sock *sk)
23 uintptr_t sk_user_data;
25 write_lock_bh(&sk->sk_callback_lock);
26 sk_user_data = (uintptr_t)sk->sk_user_data;
27 if (sk_user_data & SK_USER_DATA_BPF) {
28 struct sock __rcu **socks;
30 socks = (void *)(sk_user_data & SK_USER_DATA_PTRMASK);
31 WRITE_ONCE(sk->sk_user_data, NULL);
33 * Do not move this NULL assignment outside of
34 * sk->sk_callback_lock because there is
35 * a race with reuseport_array_free()
36 * which does not hold the reuseport_lock.
38 RCU_INIT_POINTER(*socks, NULL);
40 write_unlock_bh(&sk->sk_callback_lock);
43 static int reuseport_array_alloc_check(union bpf_attr *attr)
45 if (attr->value_size != sizeof(u32) &&
46 attr->value_size != sizeof(u64))
49 return array_map_alloc_check(attr);
52 static void *reuseport_array_lookup_elem(struct bpf_map *map, void *key)
54 struct reuseport_array *array = reuseport_array(map);
55 u32 index = *(u32 *)key;
57 if (unlikely(index >= array->map.max_entries))
60 return rcu_dereference(array->ptrs[index]);
63 /* Called from syscall only */
64 static int reuseport_array_delete_elem(struct bpf_map *map, void *key)
66 struct reuseport_array *array = reuseport_array(map);
67 u32 index = *(u32 *)key;
71 if (index >= map->max_entries)
74 if (!rcu_access_pointer(array->ptrs[index]))
77 spin_lock_bh(&reuseport_lock);
79 sk = rcu_dereference_protected(array->ptrs[index],
80 lockdep_is_held(&reuseport_lock));
82 write_lock_bh(&sk->sk_callback_lock);
83 WRITE_ONCE(sk->sk_user_data, NULL);
84 RCU_INIT_POINTER(array->ptrs[index], NULL);
85 write_unlock_bh(&sk->sk_callback_lock);
91 spin_unlock_bh(&reuseport_lock);
96 static void reuseport_array_free(struct bpf_map *map)
98 struct reuseport_array *array = reuseport_array(map);
103 * ops->map_*_elem() will not be able to access this
104 * array now. Hence, this function only races with
105 * bpf_sk_reuseport_detach() which was triggered by
106 * close() or disconnect().
108 * This function and bpf_sk_reuseport_detach() are
109 * both removing sk from "array". Who removes it
110 * first does not matter.
112 * The only concern here is bpf_sk_reuseport_detach()
113 * may access "array" which is being freed here.
114 * bpf_sk_reuseport_detach() access this "array"
115 * through sk->sk_user_data _and_ with sk->sk_callback_lock
116 * held which is enough because this "array" is not freed
117 * until all sk->sk_user_data has stopped referencing this "array".
119 * Hence, due to the above, taking "reuseport_lock" is not
124 * Since reuseport_lock is not taken, sk is accessed under
128 for (i = 0; i < map->max_entries; i++) {
129 sk = rcu_dereference(array->ptrs[i]);
131 write_lock_bh(&sk->sk_callback_lock);
133 * No need for WRITE_ONCE(). At this point,
134 * no one is reading it without taking the
135 * sk->sk_callback_lock.
137 sk->sk_user_data = NULL;
138 write_unlock_bh(&sk->sk_callback_lock);
139 RCU_INIT_POINTER(array->ptrs[i], NULL);
145 * Once reaching here, all sk->sk_user_data is not
146 * referenceing this "array". "array" can be freed now.
148 bpf_map_area_free(array);
151 static struct bpf_map *reuseport_array_alloc(union bpf_attr *attr)
153 int numa_node = bpf_map_attr_numa_node(attr);
154 struct reuseport_array *array;
157 return ERR_PTR(-EPERM);
159 /* allocate all map elements and zero-initialize them */
160 array = bpf_map_area_alloc(struct_size(array, ptrs, attr->max_entries), numa_node);
162 return ERR_PTR(-ENOMEM);
164 /* copy mandatory map attributes */
165 bpf_map_init_from_attr(&array->map, attr);
170 int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key,
176 if (map->value_size != sizeof(u64))
180 sk = reuseport_array_lookup_elem(map, key);
182 *(u64 *)value = __sock_gen_cookie(sk);
193 reuseport_array_update_check(const struct reuseport_array *array,
194 const struct sock *nsk,
195 const struct sock *osk,
196 const struct sock_reuseport *nsk_reuse,
199 if (osk && map_flags == BPF_NOEXIST)
202 if (!osk && map_flags == BPF_EXIST)
205 if (nsk->sk_protocol != IPPROTO_UDP && nsk->sk_protocol != IPPROTO_TCP)
208 if (nsk->sk_family != AF_INET && nsk->sk_family != AF_INET6)
211 if (nsk->sk_type != SOCK_STREAM && nsk->sk_type != SOCK_DGRAM)
215 * sk must be hashed (i.e. listening in the TCP case or binded
216 * in the UDP case) and
217 * it must also be a SO_REUSEPORT sk (i.e. reuse cannot be NULL).
219 * Also, sk will be used in bpf helper that is protected by
222 if (!sock_flag(nsk, SOCK_RCU_FREE) || !sk_hashed(nsk) || !nsk_reuse)
225 /* READ_ONCE because the sk->sk_callback_lock may not be held here */
226 if (READ_ONCE(nsk->sk_user_data))
233 * Called from syscall only.
234 * The "nsk" in the fd refcnt.
235 * The "osk" and "reuse" are protected by reuseport_lock.
237 int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
238 void *value, u64 map_flags)
240 struct reuseport_array *array = reuseport_array(map);
241 struct sock *free_osk = NULL, *osk, *nsk;
242 struct sock_reuseport *reuse;
243 u32 index = *(u32 *)key;
244 uintptr_t sk_user_data;
245 struct socket *socket;
248 if (map_flags > BPF_EXIST)
251 if (index >= map->max_entries)
254 if (map->value_size == sizeof(u64)) {
255 u64 fd64 = *(u64 *)value;
264 socket = sockfd_lookup(fd, &err);
274 /* Quick checks before taking reuseport_lock */
275 err = reuseport_array_update_check(array, nsk,
276 rcu_access_pointer(array->ptrs[index]),
277 rcu_access_pointer(nsk->sk_reuseport_cb),
282 spin_lock_bh(&reuseport_lock);
284 * Some of the checks only need reuseport_lock
285 * but it is done under sk_callback_lock also
286 * for simplicity reason.
288 write_lock_bh(&nsk->sk_callback_lock);
290 osk = rcu_dereference_protected(array->ptrs[index],
291 lockdep_is_held(&reuseport_lock));
292 reuse = rcu_dereference_protected(nsk->sk_reuseport_cb,
293 lockdep_is_held(&reuseport_lock));
294 err = reuseport_array_update_check(array, nsk, osk, reuse, map_flags);
296 goto put_file_unlock;
298 sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY |
300 WRITE_ONCE(nsk->sk_user_data, (void *)sk_user_data);
301 rcu_assign_pointer(array->ptrs[index], nsk);
306 write_unlock_bh(&nsk->sk_callback_lock);
309 write_lock_bh(&free_osk->sk_callback_lock);
310 WRITE_ONCE(free_osk->sk_user_data, NULL);
311 write_unlock_bh(&free_osk->sk_callback_lock);
314 spin_unlock_bh(&reuseport_lock);
320 /* Called from syscall */
321 static int reuseport_array_get_next_key(struct bpf_map *map, void *key,
324 struct reuseport_array *array = reuseport_array(map);
325 u32 index = key ? *(u32 *)key : U32_MAX;
326 u32 *next = (u32 *)next_key;
328 if (index >= array->map.max_entries) {
333 if (index == array->map.max_entries - 1)
340 static int reuseport_array_map_btf_id;
341 const struct bpf_map_ops reuseport_array_ops = {
342 .map_meta_equal = bpf_map_meta_equal,
343 .map_alloc_check = reuseport_array_alloc_check,
344 .map_alloc = reuseport_array_alloc,
345 .map_free = reuseport_array_free,
346 .map_lookup_elem = reuseport_array_lookup_elem,
347 .map_get_next_key = reuseport_array_get_next_key,
348 .map_delete_elem = reuseport_array_delete_elem,
349 .map_btf_name = "reuseport_array",
350 .map_btf_id = &reuseport_array_map_btf_id,