nwatalk: cache AFP fallback entry ids in xattrs

The AFP smoke endpoints can now read mars_nwe-owned entry ids from the versioned org.mars-nwe.afp.entry-id xattr, but a newly discovered file still had to fall back to the temporary stat-derived id on every request until a real CNID allocator exists.

Preserve the existing WebSDK/NWAFP response semantics while making that fallback sticky: when Get Entry ID, Get File Information, or Scan File Information has no mars_nwe xattr and no Netatalk/libatalk AppleDouble/CNID id, derive the existing compatibility id and cache it through nwatalk_set_entry_id().  The first request still logs fallback so diagnostics remain honest about the id origin; subsequent requests should read the xattr directly and avoid re-entering the stat fallback path.

Keep the write narrowly scoped to mars_nwe's private AFP metadata namespace.  The payload is versioned, big-endian, and stored through the nwxattr helper, so Linux persists it as user.org.mars-nwe.afp.entry-id while source-level code continues to use the Netatalk-style org.mars-nwe.afp.entry-id name.  This does not implement CNID allocation, parent-id lookup, entry-id-only resolution, FinderInfo mutation beyond the existing smoke path, or resource-fork semantics.

Tests:

- git diff --check

- cmake --build build-xattr-off --target nwconn with ENABLE_NETATALK_LIBATALK=OFF

- cmake --build build-xattr-on --target nwconn with ENABLE_NETATALK_LIBATALK=ON against Netatalk 4.4.3 headers plus local link stubs

TODO.md

@@ -251,11 +251,14 @@ Current status:
   `tests/linux/afp_set_file_info_smoke`; runtime coverage is green for
   `SYS:PUBLIC/pmdflts.ini` with Finder type `TEXT` and creator `MARS`.  The
   helper writes 32 bytes of FinderInfo to `org.mars-nwe.afp.finder-info` and
-  verifies the result through AFP 2.0 Get File Information.  A `fallback` marker
-  on the verification Get File Information diagnostic still describes the
-  stat-derived entry-id source, not the FinderInfo write result.  All other Set
-  File Information bits remain rejected until their write semantics are
-  explicitly designed.
+  verifies the result through AFP 2.0 Get File Information.  The first
+  stat-derived AFP entry id for a path is now cached in the versioned
+  `org.mars-nwe.afp.entry-id` xattr; a `fallback` marker on that first
+  verification Get File Information diagnostic describes the entry-id origin,
+  not the FinderInfo write result.  Follow-up probes should read the cached
+  mars_nwe entry id and omit the fallback marker.  All other Set File
+  Information bits remain rejected until their write semantics are explicitly
+  designed.
 - The AFP dispatcher now decodes the WebSDK/NWAFP subfunction number in
   diagnostics so real client probes can be mapped to the corresponding AFP
   call before implementation work starts.
@@ -282,14 +285,15 @@ Follow-up:
 - Keep returning invalid namespace for AFP calls that still lack a real per-volume Mac
   namespace/AFP metadata layer. Do not return success for additional AFP calls without
   data/resource fork and Finder Info semantics.
-- Replace the temporary stat-derived AFP entry-id fallback with a persistent
-  CNID/directory-id mapping once the libatalk/CNID backend is integrated.
+- Replace the compatibility stat-derived AFP entry-id generator with a real
+  CNID/directory-id allocator once the libatalk/CNID backend is integrated.
 - mars_nwe-owned AFP entry ids are probed first from the versioned
   `org.mars-nwe.afp.entry-id` xattr before consulting Netatalk/libatalk
-  AppleDouble/CNID metadata and, finally, the stat-derived fallback.
-  FinderInfo now has a deliberately narrow write path through AFP 2.0 Set File
-  Information; CNID allocation and broader AFP metadata writes still need a
-  deliberate write-safe design.
+  AppleDouble/CNID metadata.  If neither source has an id, mars_nwe derives the
+  existing stat-compatible id and caches it in that xattr so subsequent probes
+  can use persistent mars_nwe metadata.  FinderInfo now has a deliberately narrow
+  write path through AFP 2.0 Set File Information; CNID allocation and broader
+  AFP metadata writes still need a deliberate write-safe design.
 - Put additional future mars_nwe-owned AFP metadata under `org.mars-nwe.afp.*`
   (or a compact `org.mars-nwe.afp.metadata` record) and keep Netatalk-owned
   metadata under Netatalk's own `org.netatalk.*` keys.

include/nwatalk.h

@@ -12,5 +12,6 @@ int nwatalk_set_finder_info(const char *path, const uint8 *finder_info,
                             int finder_info_len);
 int nwatalk_get_resource_fork_size(const char *path, uint32 *resource_size);
 int nwatalk_get_entry_id(const char *path, uint32 *entry_id);
+int nwatalk_set_entry_id(const char *path, uint32 entry_id);
 
 #endif

src/nwatalk.c

@@ -156,6 +156,36 @@ int nwatalk_set_finder_info(const char *path, const uint8 *finder_info,
 #endif
 }
 
+
+int nwatalk_set_entry_id(const char *path, uint32 entry_id)
+{
+#if XATTR_SUPPORT
+  MARS_NWE_AFP_ENTRY_ID_XATTR_DATA d;
+
+  if (!path || !*path) return(-0x9c);
+  entry_id &= 0x7fffffffU;
+  if (!entry_id) return(-0x9c);
+
+  memset(&d, 0, sizeof(d));
+  d.version = MARS_NWE_AFP_ENTRY_ID_VERSION;
+  U32_TO_BE32(entry_id, d.entry_id);
+
+  if (mars_nwe_setxattr(path, MARS_NWE_AFP_ENTRY_ID_XATTR,
+                        &d, sizeof(d), 0)) {
+    int err = errno;
+    XDPRINTF((5,0,"AFP entry-id xattr write ignored for %s entry=0x%08x errno=%d",
+              path, entry_id, err));
+    return(-0x8c);
+  }
+
+  return(0);
+#else
+  (void)path;
+  (void)entry_id;
+  return(-0xbf);
+#endif
+}
+
 int nwatalk_get_resource_fork_size(const char *path, uint32 *resource_size)
 {
 #if NETATALK_SUPPORT

src/nwconn.c

@@ -507,6 +507,34 @@ static uint32 afp_fallback_entry_id(int volume, const struct stat *stb)
 }
 
 
+
+static uint32 afp_get_or_create_entry_id(const char *unixname, int volume,
+                                         const struct stat *stb,
+                                         int *fallback_out)
+/*
+ * Return a persistent mars_nwe AFP entry id when available.  If neither the
+ * mars_nwe xattr nor Netatalk/libatalk metadata contains an id yet, derive the
+ * existing stat-backed compatibility id and cache that id in mars_nwe's private
+ * AFP xattr namespace.  The first caller still records fallback diagnostics so
+ * the log remains honest about the id origin; follow-up requests should read the
+ * xattr directly and no longer need the temporary stat derivation path.
+ */
+{
+  uint32 entry_id = 0;
+  int result;
+
+  result = nwatalk_get_entry_id(unixname, &entry_id);
+  if (!result && entry_id) {
+    if (fallback_out) *fallback_out = 0;
+    return(entry_id);
+  }
+
+  entry_id = afp_fallback_entry_id(volume, stb);
+  if (fallback_out) *fallback_out = 1;
+  (void)nwatalk_set_entry_id(unixname, entry_id);
+  return(entry_id);
+}
+
 static int afp_get_entry_id_from_name(uint8 *afp_req, int afp_len,
                                       uint8 *response)
 {
@@ -561,15 +589,13 @@ static int afp_get_entry_id_from_name(uint8 *afp_req, int afp_len,
     return(-0x9c); /* Invalid Path */
   }
 
-  result = nwatalk_get_entry_id(unixname, &entry_id);
-  if (result < 0 || !entry_id)
-    entry_id = afp_fallback_entry_id(volume, &stbuff);
+  entry_id = afp_get_or_create_entry_id(unixname, volume, &stbuff, &result);
 
   U32_TO_BE32(entry_id, response);
   XDPRINTF((3,0, "AFP Get Entry ID From Name: vol=%d entry=0x%08x path='%s' reply_entry=0x%08x%s",
             (int)volume_number, request_entry_id,
             visable_data(afp_req + 7, path_len), entry_id,
-            (result < 0) ? " fallback" : ""));
+            result ? " fallback" : ""));
   return(4);
 }
 
@@ -612,9 +638,7 @@ static int afp_get_entry_id_from_netware_handle(uint8 *afp_req, int afp_len,
   volume = afp_volume_from_unixname((char *)unixname);
   if (volume < 0) volume = 0;
 
-  result = nwatalk_get_entry_id((char *)unixname, &entry_id);
-  if (result < 0 || !entry_id)
-    entry_id = afp_fallback_entry_id(volume, &stbuff);
+  entry_id = afp_get_or_create_entry_id((char *)unixname, volume, &stbuff, &result);
 
   response[0] = (uint8)volume;
   U32_TO_BE32(entry_id, response + 1);
@@ -622,7 +646,7 @@ static int afp_get_entry_id_from_netware_handle(uint8 *afp_req, int afp_len,
 
   XDPRINTF((3,0, "AFP Get Entry ID From NetWare Handle: handle=%u volume=%d unix='%s' entry=0x%08x%s",
             fhandle, volume, unixname, entry_id,
-            (result < 0) ? " fallback" : ""));
+            result ? " fallback" : ""));
   return(6);
 }
 
@@ -844,14 +868,12 @@ static int afp_get_entry_id_from_path_name(uint8 *afp_req, int afp_len,
     return(-0x9c); /* Invalid Path */
   }
 
-  result = nwatalk_get_entry_id(unixname, &entry_id);
-  if (result < 0 || !entry_id)
-    entry_id = afp_fallback_entry_id(volume, &stbuff);
+  entry_id = afp_get_or_create_entry_id(unixname, volume, &stbuff, &result);
 
   U32_TO_BE32(entry_id, response);
   XDPRINTF((3,0, "AFP Get Entry ID From Path Name: dh=%d path='%s' entry=0x%08x%s",
             (int)dir_handle, visable_data(afp_req + 3, path_len), entry_id,
-            (result < 0) ? " fallback" : ""));
+            result ? " fallback" : ""));
   return(4);
 }
 
@@ -956,16 +978,11 @@ static int afp_fill_file_info_response(const char *unixname,
   uint32 parent_id = 0;
   uint32 resource_size = 0;
   uint8 finder_info[NWATALK_FINDER_INFO_LEN];
-  int result;
 
   if (stat(unixname, &stbuff))
     return(-0x9c); /* Invalid Path */
 
-  result = nwatalk_get_entry_id(unixname, &entry_id);
-  if (result < 0 || !entry_id) {
-    entry_id = afp_fallback_entry_id(volume, &stbuff);
-    if (fallback_out) *fallback_out = 1;
-  } else if (fallback_out) *fallback_out = 0;
+  entry_id = afp_get_or_create_entry_id(unixname, volume, &stbuff, fallback_out);
 
   memset(response, 0, 120);
   U32_TO_BE32(entry_id, response + 0);
@@ -1280,7 +1297,6 @@ static int afp_scan_file_information(uint8 *afp_req, int afp_len,
     struct stat stbuff;
     int child_fallback = 0;
     uint32 child_entry_id = 0;
-    int child_result;
 
     if (!strcmp(de->d_name, ".") || !strcmp(de->d_name, ".."))
       continue;
@@ -1289,11 +1305,8 @@ static int afp_scan_file_information(uint8 *afp_req, int afp_len,
     if (stat(childname, &stbuff))
       continue;
 
-    child_result = nwatalk_get_entry_id(childname, &child_entry_id);
-    if (child_result < 0 || !child_entry_id) {
-      child_entry_id = afp_fallback_entry_id(volume, &stbuff);
-      child_fallback = 1;
-    }
+    child_entry_id = afp_get_or_create_entry_id(childname, volume, &stbuff,
+                                                &child_fallback);
 
     if (last_seen_id && !seen) {
       if (child_entry_id == last_seen_id)

tests/linux/README.md

@@ -7,11 +7,13 @@ The tests use the ncpfs/libncp client library.  They are not built by default
 because they require the host ncpfs development headers/library and a running
 NetWare-compatible server.
 
-The AFP endpoints are intentionally conservative.  When persistent AFP entry
-ids become available, mars_nwe-owned ids are read from the versioned
-`org.mars-nwe.afp.entry-id` xattr before falling back to Netatalk/libatalk
-AppleDouble/CNID metadata and then the temporary stat-derived fallback.  The
-first AFP write smoke path is deliberately limited to the FinderInfo bitmap of
+The AFP endpoints are intentionally conservative.  mars_nwe-owned ids are read
+from the versioned `org.mars-nwe.afp.entry-id` xattr before falling back to
+Netatalk/libatalk AppleDouble/CNID metadata.  When neither source has an id yet,
+the existing stat-derived compatibility id is cached in that xattr so subsequent
+AFP probes can reuse the same mars_nwe-owned id instead of re-entering the
+temporary fallback path.  The first AFP write smoke path is deliberately limited
+to the FinderInfo bitmap of
 AFP 2.0 Set File Information; CNID allocation, DOS attribute mapping, resource
 fork writes, and data-fork writes remain separate write-safety work.  mars_nwe
 source uses Netatalk-style `org.mars-nwe.<domain>.*` xattr names; AFP
@@ -401,13 +403,29 @@ AFP 2.0 Set File Information: vol=0 request_vol=0 entry=0x00000000 mask=0x0020 p
 AFP 2.0 Get File Information: vol=0 entry=0x00000000 mask=0xffff path='SYS:PUBLIC/pmdflts.ini' reply_entry=0x23c8787d fallback
 ```
 
-The `fallback` marker on the verification Get File Information diagnostic still
-refers to the entry-id source: the returned entry id is derived from the current
-stat-backed fallback path because no persistent CNID or `org.mars-nwe.afp.entry-id`
-metadata was present.  It does not mean the FinderInfo write was ignored; the
+The `fallback` marker on the first verification Get File Information diagnostic
+still refers to the entry-id source: the returned entry id was derived from the
+stat-backed compatibility path because no CNID or mars_nwe entry-id xattr existed
+yet.  The server now caches that derived id in `org.mars-nwe.afp.entry-id`, so a
+second probe of the same file should reuse the xattr-backed id and normally omit
+the `fallback` marker.  It does not mean the FinderInfo write was ignored; the
 helper verifies the written FinderInfo through the follow-up Get File Information
 reply.
 
+Linux xattr checks for the FinderInfo and cached Entry ID look like this:
+
+```sh
+getfattr -n user.org.mars-nwe.afp.finder-info -e hex /var/mars_nwe/SYS/public/pmdflts.ini
+getfattr -n user.org.mars-nwe.afp.entry-id -e hex /var/mars_nwe/SYS/public/pmdflts.ini
+```
+
+For the verified FinderInfo smoke run, the FinderInfo xattr starts with
+`TEXTMARS`:
+
+```text
+user.org.mars-nwe.afp.finder-info=0x544558544d415253000000000000000000000000000000000000000000000000
+```
+
 All other Set File Information bitmap bits are intentionally rejected for now.
 That keeps attribute, timestamp, DOS/NetWare mode-bit mapping, resource-fork,
 and Entry-ID-only write semantics out of this first metadata-only write smoke