Document that client pid/gid/uid may be zero.

Fixes #67.

1 files changed, 9 insertions, 2 deletions

diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index 0822e51..3765598 100644
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -98,7 +98,14 @@ struct fuse_entry_param {
 	double entry_timeout;
 };
 
-/** Additional context associated with requests */
+/**
+ * Additional context associated with requests.
+ *
+ * Note that the reported client uid, gid and pid may be zero in some
+ * situations. For example, if the FUSE file system is running in a
+ * PID or user namespace but then accessed from outside the namespace,
+ * there is no valid uid/pid/gid that could be reported.
+ */
 struct fuse_ctx {
 	/** User ID of the calling process */
 	uid_t uid;
@@ -109,7 +116,7 @@ struct fuse_ctx {
 	/** Thread ID of the calling process */
 	pid_t pid;
 
-	/** Umask of the calling process (introduced in version 2.8) */
+	/** Umask of the calling process */
 	mode_t umask;
 };