diff options
| -rw-r--r-- | include/linux/net.h | 25 | ||||
| -rw-r--r-- | net/core/utils.c | 48 |
2 files changed, 73 insertions, 0 deletions
diff --git a/include/linux/net.h b/include/linux/net.h index ca9ec8540905..a489705f6fa3 100644 --- a/include/linux/net.h +++ b/include/linux/net.h @@ -239,6 +239,31 @@ do { \ #define net_random() prandom_u32() #define net_srandom(seed) prandom_seed((__force u32)(seed)) +bool __net_get_random_once(void *buf, int nbytes, bool *done, + struct static_key *done_key); + +#ifdef HAVE_JUMP_LABEL +#define ___NET_RANDOM_STATIC_KEY_INIT ((struct static_key) \ + { .enabled = ATOMIC_INIT(0), .entries = (void *)1 }) +#else /* !HAVE_JUMP_LABEL */ +#define ___NET_RANDOM_STATIC_KEY_INIT STATIC_KEY_INIT_FALSE +#endif /* HAVE_JUMP_LABEL */ + +/* BE CAREFUL: this function is not interrupt safe */ +#define net_get_random_once(buf, nbytes) \ + ({ \ + bool ___ret = false; \ + static bool ___done = false; \ + static struct static_key ___done_key = \ + ___NET_RANDOM_STATIC_KEY_INIT; \ + if (!static_key_true(&___done_key)) \ + ___ret = __net_get_random_once(buf, \ + nbytes, \ + &___done, \ + &___done_key); \ + ___ret; \ + }) + int kernel_sendmsg(struct socket *sock, struct msghdr *msg, struct kvec *vec, size_t num, size_t len); int kernel_recvmsg(struct socket *sock, struct msghdr *msg, struct kvec *vec, diff --git a/net/core/utils.c b/net/core/utils.c index aa88e23fc87a..bf09371e19b1 100644 --- a/net/core/utils.c +++ b/net/core/utils.c @@ -338,3 +338,51 @@ void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb, csum_unfold(*sum))); } EXPORT_SYMBOL(inet_proto_csum_replace16); + +struct __net_random_once_work { + struct work_struct work; + struct static_key *key; +}; + +static void __net_random_once_deferred(struct work_struct *w) +{ + struct __net_random_once_work *work = + container_of(w, struct __net_random_once_work, work); + if (!static_key_enabled(work->key)) + static_key_slow_inc(work->key); + kfree(work); +} + +static void __net_random_once_disable_jump(struct static_key *key) +{ + struct __net_random_once_work *w; + + w = kmalloc(sizeof(*w), GFP_ATOMIC); + if (!w) + return; + + INIT_WORK(&w->work, __net_random_once_deferred); + w->key = key; + schedule_work(&w->work); +} + +bool __net_get_random_once(void *buf, int nbytes, bool *done, + struct static_key *done_key) +{ + static DEFINE_SPINLOCK(lock); + + spin_lock_bh(&lock); + if (*done) { + spin_unlock_bh(&lock); + return false; + } + + get_random_bytes(buf, nbytes); + *done = true; + spin_unlock_bh(&lock); + + __net_random_once_disable_jump(done_key); + + return true; +} +EXPORT_SYMBOL(__net_get_random_once); |