swrap: export a public socket_wrapper_indicate_no_inet_fd() helper function

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14640

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>

3 files changed, 53 insertions, 0 deletions

diff --git a/src/socket_wrapper.c b/src/socket_wrapper.c
index 63de148..714cd25 100644
--- a/src/socket_wrapper.c
+++ b/src/socket_wrapper.c
@@ -7456,6 +7456,28 @@ static void swrap_remove_stale(int fd)
 	swrap_remove_wrapper(__func__, swrap_noop_close, fd);
 }
 
+/*
+ * This allows socket_wrapper aware applications to
+ * indicate that the given fd does not belong to
+ * an inet socket.
+ *
+ * We already overload a lot of unrelated functions
+ * like eventfd(), timerfd_create(), ... in order to
+ * call swrap_remove_stale() on the returned fd, but
+ * we'll never be able to handle all possible syscalls.
+ *
+ * socket_wrapper_indicate_no_inet_fd() gives them a way
+ * to do the same.
+ *
+ * We don't export swrap_remove_stale() in order to
+ * make it easier to analyze SOCKET_WRAPPER_DEBUGLEVEL=3
+ * log files.
+ */
+void socket_wrapper_indicate_no_inet_fd(int fd)
+{
+	swrap_remove_wrapper(__func__, swrap_noop_close, fd);
+}
+
 static int swrap_close(int fd)
 {
 	return swrap_remove_wrapper(__func__, libc_close, fd);
diff --git a/src/socket_wrapper.h b/src/socket_wrapper.h
index f1a97e8..3ec5031 100644
--- a/src/socket_wrapper.h
+++ b/src/socket_wrapper.h
@@ -61,4 +61,29 @@
  */
 bool socket_wrapper_enabled(void);
 
+/*
+ * This allows socket_wrapper aware applications to
+ * indicate that the given fd does not belong to
+ * an inet socket.
+ *
+ * socket_wrapper may not be able to intercept the __close_nocancel()
+ * syscall made from within libc.so. As result it's possible
+ * that the in memory meta date of socket_wrapper references
+ * stale file descriptors, which are already reused for unrelated
+ * kernel objects, e.g. files, directories, ...
+ *
+ * Socket wrapper already intercepts a lot of unrelated
+ * functions like eventfd(), timerfd_create(), ... in order
+ * to remove stale meta data for the returned fd, but
+ * it will never be able to handle all possible syscalls.
+ *
+ * socket_wrapper_indicate_no_inet_fd() gives applications a way
+ * to do the same, explicitly without waiting for new syscalls to
+ * be added to libsocket_wrapper.so.
+ *
+ * This is a no-op if socket_wrapper is not in use or
+ * if the there is no in memory meta data for the given fd.
+ */
+void socket_wrapper_indicate_no_inet_fd(int fd);
+
 #endif /* __SOCKET_WRAPPER_H__ */
diff --git a/src/socket_wrapper_noop.c b/src/socket_wrapper_noop.c
index 45aff8f..aadf350 100644
--- a/src/socket_wrapper_noop.c
+++ b/src/socket_wrapper_noop.c
@@ -55,3 +55,9 @@ bool socket_wrapper_enabled(void)
 {
 	return false;
 }
+
+void socket_wrapper_indicate_no_inet_fd(int fd)
+{
+	(void) fd; /* unused */
+	return;
+}