nwconn: persist additional AFP metadata attributes

Extend the conservative AFP 2.0 Set File Information smoke path to accept the metadata-only System and Backup file attribute bits alongside the already-supported Finder Invisible bit.

The WebSDK/NWAFP Set File Information request uses the file Attributes bitmap to pass a set/clear attribute word. Netatalk stores several AFP file attributes in AppleDouble metadata while computing open-fork state dynamically and leaving enforcement-sensitive bits to the file/fork paths. Mirror only the low-risk mars_nwe subset here: persist Invisible, System, and Backup in the private org.mars-nwe.afp.attributes xattr, and keep NoWrite, NoRename, NoDelete, NoCopy, data-fork-open, resource-fork-open, timestamps, resource forks, and Entry-ID-only write semantics rejected until they have deliberate enforcement and backend design.

The xattr payload remains versioned and unchanged. Reads now expose the three supported metadata bits through Get/Scan File Information, and writes preserve the existing set/clear semantics over the supported mask.

Update the Linux Set File Information smoke helper with --system/--clear-system and --backup/--clear-backup options, while keeping the smoke-suite default unchanged. Document the expected Linux xattr forms 0x01000004 and 0x01000040 for those optional probes.

Tests: git diff --check; gcc -Iinclude -I/mnt/data/stubs -fsyntax-only tests/linux/afp_set_file_info_smoke.c.

src/nwatalk.c

@@ -23,7 +23,11 @@
 #define MARS_NWE_AFP_ATTRIBUTES_VERSION 1
 
 #define NWATALK_AFP_ATTR_INVISIBLE 0x0001
+#define NWATALK_AFP_ATTR_SYSTEM    0x0004
+#define NWATALK_AFP_ATTR_BACKUP    0x0040
 #define NWATALK_AFP_ATTR_SETCLR    0x8000
+#define NWATALK_AFP_ATTR_STORED_MASK \
+  (NWATALK_AFP_ATTR_INVISIBLE | NWATALK_AFP_ATTR_SYSTEM | NWATALK_AFP_ATTR_BACKUP)
 
 typedef struct {
   uint8 version;
@@ -185,7 +189,7 @@ int nwatalk_get_afp_attributes(const char *path, uint16 *attributes)
   len = mars_nwe_getxattr(path, MARS_NWE_AFP_ATTRIBUTES_XATTR,
                           &d, sizeof(d));
   if (len == sizeof(d) && d.version == MARS_NWE_AFP_ATTRIBUTES_VERSION) {
-    *attributes = GET_BE16(d.attributes) & NWATALK_AFP_ATTR_INVISIBLE;
+    *attributes = GET_BE16(d.attributes) & NWATALK_AFP_ATTR_STORED_MASK;
     return(0);
   }
 #else
@@ -205,7 +209,7 @@ int nwatalk_set_afp_attributes(const char *path, uint16 attributes)
 
   if (!path || !*path) return(-0x9c);
 
-  if (requested & ~NWATALK_AFP_ATTR_INVISIBLE) {
+  if (requested & ~NWATALK_AFP_ATTR_STORED_MASK) {
     XDPRINTF((3,0,"AFP attributes xattr write rejected for %s attrs=0x%04x", path, attributes));
     return(-0x9c);
   }

src/nwconn.c

@@ -1096,7 +1096,11 @@ static int afp_get_file_information(uint8 *afp_req, int afp_len,
 #define AFP_FILE_BITMAP_ATTRIBUTES  0x0001
 #define AFP_FILE_BITMAP_FINDER_INFO 0x0020
 #define AFP_ATTR_INVISIBLE         0x0001
+#define AFP_ATTR_SYSTEM            0x0004
+#define AFP_ATTR_BACKUP            0x0040
 #define AFP_ATTR_SETCLR            0x8000
+#define AFP_ATTR_STORED_MASK \
+  (AFP_ATTR_INVISIBLE | AFP_ATTR_SYSTEM | AFP_ATTR_BACKUP)
 
 static int afp_set_file_information(uint8 *afp_req, int afp_len,
                                     const char *call_name)
@@ -1173,7 +1177,7 @@ static int afp_set_file_information(uint8 *afp_req, int afp_len,
   if (request_mask & AFP_FILE_BITMAP_ATTRIBUTES) {
     uint16 requested_attrs = GET_BE16(afp_req + data_off);
     uint16 requested_bits = requested_attrs & ~AFP_ATTR_SETCLR;
-    if (requested_bits & ~AFP_ATTR_INVISIBLE) {
+    if (requested_bits & ~AFP_ATTR_STORED_MASK) {
       XDPRINTF((2,0, "%s rejected: unsupported AFP attributes attrs=0x%04x path='%s'",
                 call_name, requested_attrs, visable_data(afp_req + 9, path_len)));
       return(-0x9c);
@@ -3358,8 +3362,9 @@ static int handle_ncp_serv(void)
                      * effective rights.  Then expose
                      * the read-only AFP Get File Information query for the same
                      * SYS:-style path inputs.  AFP 2.0 Set File Information
-                     * accepts only the FinderInfo bitmap as a metadata-only
-                     * xattr write smoke path.  AFP 2.0 Get File Information
+                     * accepts only FinderInfo plus the
+                     * metadata-only Invisible/System/Backup file attributes as
+                     * xattr write smoke paths.  AFP 2.0 Get File Information
                      * uses the same request/reply layout for this read-only
                      * path-backed subset, so route it through the same helper
                      * until persistent entry-id lookup and richer AFP 2.0