// 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)
{
struct sock __rcu **socks;
write_lock_bh(&sk->sk_callback_lock);
socks = sk->sk_user_data;
if (socks) {
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;
synchronize_rcu();
/*
* 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 err, numa_node = bpf_map_attr_numa_node(attr);
struct reuseport_array *array;
struct bpf_map_memory mem;
u64 array_size;
if (!capable(CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);
array_size = sizeof(*array);
array_size += (u64)attr->max_entries * sizeof(struct sock *);
err = bpf_map_charge_init(&mem, array_size);
if (err)
return ERR_PTR(err);
/* allocate all map elements and zero-initialize them */
array = bpf_map_area_alloc(array_size, numa_node);
if (!array) {
bpf_map_charge_finish(&mem);
return ERR_PTR(-ENOMEM);
}
/* copy mandatory map attributes */
bpf_map_init_from_attr(&array->map, attr);
bpf_map_charge_move(&array->map.memory, &mem);
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;
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;
/* Ensure reuse->reuseport_id is set */
err = reuseport_get_id(reuse);
if (err < 0)
goto put_file_unlock;
WRITE_ONCE(nsk->sk_user_data, &array->ptrs[index]);
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;
}
const struct bpf_map_ops reuseport_array_ops = {
.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,
};
