o Add a 'showattr' function the extattrctl, allowing a backing file to

be inspected to show the maximum attribute size and file.

usr.sbin/extattrctl/extattrctl.8

@@ -50,6 +50,9 @@
 .Ar attrsize
 .Ar attrfile
 .Nm
+.Cm showattr
+.Ar attrfile
+.Nm
 .Cm enable
 .Ar path
 .Ar attrnamespace
@@ -109,6 +112,9 @@ from denying attribute service.
 .Pp
 This file should not exist before running
 .Cm initattr .
+.It Cm showattr Ar attrfile
+Show the attribute header values in the attribute file named by
+.Ar attrfile .
 .It Cm enable Ar path attrnamespace attrname attrfile
 Enable an attribute named
 .Ar attrname

usr.sbin/extattrctl/extattrctl.c

@@ -49,6 +49,7 @@
 #include <unistd.h>
 
 int initattr(int argc, char *argv[]);
+int showattr(int argc, char *argv[]);
 long num_inodes_by_path(char *path);
 void usage(void);
 
@@ -61,6 +62,7 @@ usage()
 	    "  extattrctl start [path]\n"
 	    "  extattrctl stop [path]\n"
 	    "  extattrctl initattr [-f] [-p path] [attrsize] [attrfile]\n"
+	    "  extattrctl showattr [attrfile]\n"
 	    "  extattrctl enable [path] [attrnamespace] [attrname] [attrfile]\n"
 	    "  extattrctl disable [path] [attrnamespace] [attrname]\n");
 	exit(-1);
@@ -160,6 +162,42 @@ initattr(int argc, char *argv[])
 	return (0);
 }
 
+int
+showattr(int argc, char *argv[])
+{
+	struct ufs_extattr_fileheader	uef;
+	int i, fd;
+
+	if (argc != 1)
+		usage();
+
+	fd = open(argv[0], O_RDONLY);
+	if (fd == -1) {
+		perror(argv[0]);
+		return (-1);
+	}
+
+	i = read(fd, &uef, sizeof(uef));
+	if (i == -1) {
+		perror(argv[0]);
+		return (-1);
+	}
+	if (i != sizeof(uef)) {
+		fprintf(stderr, "%s: invalid file header\n", argv[0]);
+		return (-1);
+	}
+
+	if (uef.uef_magic != UFS_EXTATTR_MAGIC) {
+		fprintf(stderr, "%s: bad magic\n", argv[0]);
+		return (-1);
+	}
+
+	printf("%s: version %d, size %d\n", argv[0], uef.uef_version,
+	    uef.uef_size);
+
+	return (0);
+}
+
 int
 main(int argc, char *argv[])
 {
@@ -220,6 +258,12 @@ main(int argc, char *argv[])
 		error = initattr(argc, argv);
 		if (error)
 			return (-1);
+	} else if (!strcmp(argv[1], "showattr")) {
+		argc -= 2;
+		argv += 2;
+		error = showattr(argc, argv);
+		if (error)
+			return (-1);
 	} else
 		usage();