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-rw-r--r--include/linux/net.h25
-rw-r--r--net/core/utils.c48
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);