1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (c) 2018 Facebook
7 #include <linux/sock_diag.h>
8 #include <net/sock_reuseport.h>
9 #include <linux/btf_ids.h>
11 struct reuseport_array {
13 struct sock __rcu *ptrs[];
16 static struct reuseport_array *reuseport_array(struct bpf_map *map)
18 return (struct reuseport_array *)map;
21 /* The caller must hold the reuseport_lock */
22 void bpf_sk_reuseport_detach(struct sock *sk)
24 uintptr_t sk_user_data;
26 write_lock_bh(&sk->sk_callback_lock);
27 sk_user_data = (uintptr_t)sk->sk_user_data;
28 if (sk_user_data & SK_USER_DATA_BPF) {
29 struct sock __rcu **socks;
31 socks = (void *)(sk_user_data & SK_USER_DATA_PTRMASK);
32 WRITE_ONCE(sk->sk_user_data, NULL);
34 * Do not move this NULL assignment outside of
35 * sk->sk_callback_lock because there is
36 * a race with reuseport_array_free()
37 * which does not hold the reuseport_lock.
39 RCU_INIT_POINTER(*socks, NULL);
41 write_unlock_bh(&sk->sk_callback_lock);
44 static int reuseport_array_alloc_check(union bpf_attr *attr)
46 if (attr->value_size != sizeof(u32) &&
47 attr->value_size != sizeof(u64))
50 return array_map_alloc_check(attr);
53 static void *reuseport_array_lookup_elem(struct bpf_map *map, void *key)
55 struct reuseport_array *array = reuseport_array(map);
56 u32 index = *(u32 *)key;
58 if (unlikely(index >= array->map.max_entries))
61 return rcu_dereference(array->ptrs[index]);
64 /* Called from syscall only */
65 static int reuseport_array_delete_elem(struct bpf_map *map, void *key)
67 struct reuseport_array *array = reuseport_array(map);
68 u32 index = *(u32 *)key;
72 if (index >= map->max_entries)
75 if (!rcu_access_pointer(array->ptrs[index]))
78 spin_lock_bh(&reuseport_lock);
80 sk = rcu_dereference_protected(array->ptrs[index],
81 lockdep_is_held(&reuseport_lock));
83 write_lock_bh(&sk->sk_callback_lock);
84 WRITE_ONCE(sk->sk_user_data, NULL);
85 RCU_INIT_POINTER(array->ptrs[index], NULL);
86 write_unlock_bh(&sk->sk_callback_lock);
92 spin_unlock_bh(&reuseport_lock);
97 static void reuseport_array_free(struct bpf_map *map)
99 struct reuseport_array *array = reuseport_array(map);
104 * ops->map_*_elem() will not be able to access this
105 * array now. Hence, this function only races with
106 * bpf_sk_reuseport_detach() which was triggered by
107 * close() or disconnect().
109 * This function and bpf_sk_reuseport_detach() are
110 * both removing sk from "array". Who removes it
111 * first does not matter.
113 * The only concern here is bpf_sk_reuseport_detach()
114 * may access "array" which is being freed here.
115 * bpf_sk_reuseport_detach() access this "array"
116 * through sk->sk_user_data _and_ with sk->sk_callback_lock
117 * held which is enough because this "array" is not freed
118 * until all sk->sk_user_data has stopped referencing this "array".
120 * Hence, due to the above, taking "reuseport_lock" is not
125 * Since reuseport_lock is not taken, sk is accessed under
129 for (i = 0; i < map->max_entries; i++) {
130 sk = rcu_dereference(array->ptrs[i]);
132 write_lock_bh(&sk->sk_callback_lock);
134 * No need for WRITE_ONCE(). At this point,
135 * no one is reading it without taking the
136 * sk->sk_callback_lock.
138 sk->sk_user_data = NULL;
139 write_unlock_bh(&sk->sk_callback_lock);
140 RCU_INIT_POINTER(array->ptrs[i], NULL);
146 * Once reaching here, all sk->sk_user_data is not
147 * referencing this "array". "array" can be freed now.
149 bpf_map_area_free(array);
152 static struct bpf_map *reuseport_array_alloc(union bpf_attr *attr)
154 int numa_node = bpf_map_attr_numa_node(attr);
155 struct reuseport_array *array;
158 return ERR_PTR(-EPERM);
160 /* allocate all map elements and zero-initialize them */
161 array = bpf_map_area_alloc(struct_size(array, ptrs, attr->max_entries), numa_node);
163 return ERR_PTR(-ENOMEM);
165 /* copy mandatory map attributes */
166 bpf_map_init_from_attr(&array->map, attr);
171 int bpf_fd_reuseport_array_lookup_elem(struct bpf_map *map, void *key,
177 if (map->value_size != sizeof(u64))
181 sk = reuseport_array_lookup_elem(map, key);
183 *(u64 *)value = __sock_gen_cookie(sk);
194 reuseport_array_update_check(const struct reuseport_array *array,
195 const struct sock *nsk,
196 const struct sock *osk,
197 const struct sock_reuseport *nsk_reuse,
200 if (osk && map_flags == BPF_NOEXIST)
203 if (!osk && map_flags == BPF_EXIST)
206 if (nsk->sk_protocol != IPPROTO_UDP && nsk->sk_protocol != IPPROTO_TCP)
209 if (nsk->sk_family != AF_INET && nsk->sk_family != AF_INET6)
212 if (nsk->sk_type != SOCK_STREAM && nsk->sk_type != SOCK_DGRAM)
216 * sk must be hashed (i.e. listening in the TCP case or binded
217 * in the UDP case) and
218 * it must also be a SO_REUSEPORT sk (i.e. reuse cannot be NULL).
220 * Also, sk will be used in bpf helper that is protected by
223 if (!sock_flag(nsk, SOCK_RCU_FREE) || !sk_hashed(nsk) || !nsk_reuse)
226 /* READ_ONCE because the sk->sk_callback_lock may not be held here */
227 if (READ_ONCE(nsk->sk_user_data))
234 * Called from syscall only.
235 * The "nsk" in the fd refcnt.
236 * The "osk" and "reuse" are protected by reuseport_lock.
238 int bpf_fd_reuseport_array_update_elem(struct bpf_map *map, void *key,
239 void *value, u64 map_flags)
241 struct reuseport_array *array = reuseport_array(map);
242 struct sock *free_osk = NULL, *osk, *nsk;
243 struct sock_reuseport *reuse;
244 u32 index = *(u32 *)key;
245 uintptr_t sk_user_data;
246 struct socket *socket;
249 if (map_flags > BPF_EXIST)
252 if (index >= map->max_entries)
255 if (map->value_size == sizeof(u64)) {
256 u64 fd64 = *(u64 *)value;
265 socket = sockfd_lookup(fd, &err);
275 /* Quick checks before taking reuseport_lock */
276 err = reuseport_array_update_check(array, nsk,
277 rcu_access_pointer(array->ptrs[index]),
278 rcu_access_pointer(nsk->sk_reuseport_cb),
283 spin_lock_bh(&reuseport_lock);
285 * Some of the checks only need reuseport_lock
286 * but it is done under sk_callback_lock also
287 * for simplicity reason.
289 write_lock_bh(&nsk->sk_callback_lock);
291 osk = rcu_dereference_protected(array->ptrs[index],
292 lockdep_is_held(&reuseport_lock));
293 reuse = rcu_dereference_protected(nsk->sk_reuseport_cb,
294 lockdep_is_held(&reuseport_lock));
295 err = reuseport_array_update_check(array, nsk, osk, reuse, map_flags);
297 goto put_file_unlock;
299 sk_user_data = (uintptr_t)&array->ptrs[index] | SK_USER_DATA_NOCOPY |
301 WRITE_ONCE(nsk->sk_user_data, (void *)sk_user_data);
302 rcu_assign_pointer(array->ptrs[index], nsk);
307 write_unlock_bh(&nsk->sk_callback_lock);
310 write_lock_bh(&free_osk->sk_callback_lock);
311 WRITE_ONCE(free_osk->sk_user_data, NULL);
312 write_unlock_bh(&free_osk->sk_callback_lock);
315 spin_unlock_bh(&reuseport_lock);
321 /* Called from syscall */
322 static int reuseport_array_get_next_key(struct bpf_map *map, void *key,
325 struct reuseport_array *array = reuseport_array(map);
326 u32 index = key ? *(u32 *)key : U32_MAX;
327 u32 *next = (u32 *)next_key;
329 if (index >= array->map.max_entries) {
334 if (index == array->map.max_entries - 1)
341 BTF_ID_LIST_SINGLE(reuseport_array_map_btf_ids, struct, reuseport_array)
342 const struct bpf_map_ops reuseport_array_ops = {
343 .map_meta_equal = bpf_map_meta_equal,
344 .map_alloc_check = reuseport_array_alloc_check,
345 .map_alloc = reuseport_array_alloc,
346 .map_free = reuseport_array_free,
347 .map_lookup_elem = reuseport_array_lookup_elem,
348 .map_get_next_key = reuseport_array_get_next_key,
349 .map_delete_elem = reuseport_array_delete_elem,
350 .map_btf_id = &reuseport_array_map_btf_ids[0],