fanotify: send events using read

Send events to userspace by reading the file descriptor from fanotify_init().
One will get blocks of data which look like:

struct fanotify_event_metadata {
	__u32 event_len;
	__u32 vers;
	__s32 fd;
	__u64 mask;
	__s64 pid;
	__u64 cookie;
} __attribute__ ((packed));

Simple code to retrieve and deal with events is below

	while ((len = read(fan_fd, buf, sizeof(buf))) > 0) {
		struct fanotify_event_metadata *metadata;

		metadata = (void *)buf;
		while(FAN_EVENT_OK(metadata, len)) {
			[PROCESS HERE!!]
			if (metadata->fd >= 0 && close(metadata->fd) != 0)
				goto fail;
			metadata = FAN_EVENT_NEXT(metadata, len);
		}
	}

Signed-off-by: Eric Paris <eparis@redhat.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index 95aeea2a3ca..c1c66162a46 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -51,6 +51,30 @@
  */
 #define FAN_ALL_INCOMING_EVENTS	(FAN_ALL_EVENTS |\
 				 FAN_EVENT_ON_CHILD)
+
+#define FAN_ALL_OUTGOING_EVENTS	(FAN_ALL_EVENTS |\
+				 FAN_Q_OVERFLOW)
+
+#define FANOTIFY_METADATA_VERSION	1
+
+struct fanotify_event_metadata {
+	__u32 event_len;
+	__u32 vers;
+	__s32 fd;
+	__u64 mask;
+} __attribute__ ((packed));
+
+/* Helper functions to deal with fanotify_event_metadata buffers */
+#define FAN_EVENT_METADATA_LEN (sizeof(struct fanotify_event_metadata))
+
+#define FAN_EVENT_NEXT(meta, len) ((len) -= (meta)->event_len, \
+				   (struct fanotify_event_metadata*)(((char *)(meta)) + \
+				   (meta)->event_len))
+
+#define FAN_EVENT_OK(meta, len)	((long)(len) >= (long)FAN_EVENT_METADATA_LEN && \
+				(long)(meta)->event_len >= (long)FAN_EVENT_METADATA_LEN && \
+				(long)(meta)->event_len <= (long)(len))
+
 #ifdef __KERNEL__
 
 #endif /* __KERNEL__ */