nwatalk: probe mars_nwe AFP entry ids from xattrs

Add the first mars_nwe-owned AFP metadata xattr reader before expanding the AFP write surface.  The new versioned org.mars-nwe.afp.entry-id payload gives the compatibility layer a stable, project-owned namespace for persistent AFP entry ids without reusing the unreleased user.mars_nwe.* test names or pretending that Netatalk-owned org.netatalk.* keys are ours to mutate.

The lookup order remains conservative: an existing mars_nwe entry-id xattr wins, then the optional Netatalk/libatalk AppleDouble/CNID helper is consulted, and the AFP handlers continue to fall back to their stat-derived temporary id when no persistent metadata exists.  No Set File Information, CNID allocation, Finder Info write, or resource-fork write path is introduced here.

This keeps the WebSDK/NWAFP read-only endpoint semantics intact while preparing the metadata storage boundary needed by later AFP Set File Information and CNID work.  ENABLE_NETATALK_LIBATALK=OFF still rejects AFP calls at the handler guard, and the xattr reader has an XATTR_SUPPORT-disabled stub so non-xattr builds keep compiling.

Tests:

- git diff --check

- cmake --build build-xattr-off --target nwconn

- cmake -S . -B build-afp-on -DENABLE_NETATALK_LIBATALK=ON -DCMAKE_PREFIX_PATH=/mnt/data/afp_build_prefix

- cmake --build build-afp-on --target nwconn

TODO:

- Add a deliberate write-safe AFP metadata writer/allocator before enabling AFP 2.0 Set File Information.

- Decide whether future mars_nwe AFP metadata stays split across org.mars-nwe.afp.* keys or moves into a compact org.mars-nwe.afp.metadata record.

TODO.md

@@ -271,9 +271,14 @@ Follow-up:
   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.
-- Put 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.
+- 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.  No AFP
+  metadata write path exists yet; Set File Information and CNID allocation
+  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.
 - Extend the Linux AFP smoke tests once additional AFP subfunctions are
   implemented, especially Finder Info updates, fork open/read/write paths,
   resource-fork handling, and broader directory-scan edge cases.

src/nwatalk.c

@@ -6,12 +6,58 @@
 
 #include <string.h>
 
+#if XATTR_SUPPORT
+#include <sys/types.h>
+#include <sys/xattr.h>
+#endif
+
 #if NETATALK_SUPPORT
-#include <errno.h>
 #include <sys/stat.h>
 #include <atalk/adouble.h>
 #endif
 
+#define MARS_NWE_AFP_ENTRY_ID_XATTR "org.mars-nwe.afp.entry-id"
+#define MARS_NWE_AFP_ENTRY_ID_VERSION 1
+
+typedef struct {
+  uint8 version;
+  uint8 reserved[3];
+  uint8 entry_id[4];
+} MARS_NWE_AFP_ENTRY_ID_XATTR_DATA;
+
+
+#if XATTR_SUPPORT
+static int nwatalk_get_mars_entry_id_xattr(const char *path, uint32 *entry_id)
+{
+  MARS_NWE_AFP_ENTRY_ID_XATTR_DATA d;
+  ssize_t len;
+  uint32 id;
+
+  if (!entry_id) return(-0x9c);
+  *entry_id = 0;
+  if (!path || !*path) return(-0x9c);
+
+  memset(&d, 0, sizeof(d));
+  len = getxattr(path, MARS_NWE_AFP_ENTRY_ID_XATTR, &d, sizeof(d));
+  if (len != sizeof(d) || d.version != MARS_NWE_AFP_ENTRY_ID_VERSION)
+    return(-0x9c);
+
+  id = GET_BE32(d.entry_id);
+  id &= 0x7fffffffU;
+  if (!id) return(-0x9c);
+
+  *entry_id = id;
+  return(0);
+}
+#else
+static int nwatalk_get_mars_entry_id_xattr(const char *path, uint32 *entry_id)
+{
+  (void)path;
+  if (entry_id) *entry_id = 0;
+  return(-0xbf);
+}
+#endif
+
 int nwatalk_backend_available(void)
 {
 #if NETATALK_SUPPORT
@@ -104,29 +150,35 @@ int nwatalk_get_resource_fork_size(const char *path, uint32 *resource_size)
 
 int nwatalk_get_entry_id(const char *path, uint32 *entry_id)
 {
-#if NETATALK_SUPPORT
-  struct adouble ad;
-  struct stat stbuff;
-  uint32_t id;
   int result;
 
   if (!entry_id) return(-0x9c);
   *entry_id = 0;
   if (!path || !*path) return(-0x9c);
 
-  if (stat(path, &stbuff)) return(-0x9c);
+  result = nwatalk_get_mars_entry_id_xattr(path, entry_id);
+  if (!result && *entry_id)
+    return(0);
 
-  result = nwatalk_open_adouble(path, &ad);
-  if (result < 0) return(result);
+#if NETATALK_SUPPORT
+  {
+    struct adouble ad;
+    struct stat stbuff;
+    uint32_t id;
 
-  id = ad_getid(&ad, stbuff.st_dev, stbuff.st_ino, 0, NULL);
-  if (id) *entry_id = (uint32)id;
+    if (stat(path, &stbuff)) return(-0x9c);
 
-  ad_close(&ad, 0);
-  return(id ? 0 : -0x9c);
+    result = nwatalk_open_adouble(path, &ad);
+    if (result < 0) return(result);
+
+    id = ad_getid(&ad, stbuff.st_dev, stbuff.st_ino, 0, NULL);
+    if (id) *entry_id = (uint32)id;
+
+    ad_close(&ad, 0);
+    return(id ? 0 : -0x9c);
+  }
 #else
-  (void)path;
-  (void)entry_id;
+  (void)result;
   return(-0xbf); /* invalid namespace / backend unavailable */
 #endif
 }

tests/linux/README.md

@@ -7,6 +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
+current smoke tests do not write AFP metadata; Set File Information and CNID
+allocation remain separate write-safety work.
+
 Build with:
 
 ```sh