logd: sepolicy dynamic rate limiting
Processing overhead for selinux violation messages is costly. We want
to deal with bursts of violations, but we have no intent of allowing
that sustained burst to go unabated as there is a cost of processing
and battery usage.
Tunables in libaudit.h are:
AUDIT_RATE_LIMIT_DEFAULT 20 /* acceptable burst rate */
AUDIT_RATE_LIMIT_BURST_DURATION 10 /* number of seconds of burst */
AUDIT_RATE_LIMIT_MAX 5 /* acceptable sustained rate */
Since we can only asymptotically handle DEFAULT rate, we set an upper
threshold of half way between the MAX and DEFAULT rate.
Default kernel audit subsystem message rate is set to 20 a second.
If sepolicy exceeds 125 violation messages over up to ten seconds
(>=~12/s), tell kernel audit subsystem to drop the rate to 5 messages
a second. If rate drops below 50 messages over the past ten seconds
(<5/s), tell kernel it is ok to increase the burst rate back to 20
messages a second.
Test: gTest logd-unit-tests --gtest_filter=logd.sepolicy_rate_limiter_*
Bug: 27878170
Change-Id: I843f8dcfbb3ecfbbe94a4865ea332c858e3be7f2
diff --git a/logd/libaudit.h b/logd/libaudit.h
index b9e330d..9865d43 100644
--- a/logd/libaudit.h
+++ b/logd/libaudit.h
@@ -33,7 +33,7 @@
#define MAX_AUDIT_MESSAGE_LENGTH 8970
typedef enum {
- GET_REPLY_BLOCKING=0,
+ GET_REPLY_BLOCKING = 0,
GET_REPLY_NONBLOCKING
} reply_t;
@@ -55,7 +55,7 @@
* A valid fd on success or < 0 on error with errno set.
* Returns the same errors as man 2 socket.
*/
-extern int audit_open(void);
+extern int audit_open(void);
/**
* Closes the fd returned from audit_open()
@@ -78,19 +78,36 @@
* @return
* This function returns 0 on success, else -errno.
*/
-extern int audit_get_reply(int fd, struct audit_message *rep, reply_t block,
- int peek);
+extern int audit_get_reply(int fd, struct audit_message *rep, reply_t block,
+ int peek);
/**
- * Sets a pid to recieve audit netlink events from the kernel
+ * Sets a pid to receive audit netlink events from the kernel
* @param fd
* The fd returned by a call to audit_open()
* @param pid
- * The pid whom to set as the reciever of audit messages
+ * The pid whom to set as the receiver of audit messages
* @return
* This function returns 0 on success, -errno on error.
*/
-extern int audit_setup(int fd, uint32_t pid);
+extern int audit_setup(int fd, pid_t pid);
+
+/**
+ * Sets the rate limit to receive audit netlink events from the kernel
+ * @param fd
+ * The fd returned by a call to audit_open()
+ * @param max_rate
+ * The cap of the maximum number of audit messages a second
+ * @return
+ * This function returns 0 on success, -errno on error.
+ */
+
+/* Guidelines to follow for dynamic rate_limit */
+#define AUDIT_RATE_LIMIT_DEFAULT 20 /* acceptable burst rate */
+#define AUDIT_RATE_LIMIT_BURST_DURATION 10 /* number of seconds of burst */
+#define AUDIT_RATE_LIMIT_MAX 5 /* acceptable sustained rate */
+
+extern int audit_rate_limit(int fd, unsigned rate_limit);
__END_DECLS