fsp-server: implement GET_PRO (0x47), which Swiss asks for first

Swiss sent CC_GET_PRO 'swiss/patches' and the server replied "unsupported".
Reply shape, from fsplib's fsp_getpro:

  * pos MUST equal FSP_PRO_BYTES (1), or fsplib fails with ENOMSG
  * the flags byte is at buf[len] -- the first byte of the EXTRA region,
    after the echoed name, NOT inside the data field
  * a missing directory must be CC_ERR so fsplib reports ENOENT, because
    Swiss probes "swiss/patches", then "swiss", then "" and relies on that
    fallback chain

Those bits are not cosmetic.  deviceHandler-FSP.c does:

  if ((pro & (MKDIR|ADD|DEL|GET)) == (MKDIR|ADD|DEL) || (pro & OWNER)) {
      features |= FEAT_PATCHES;  emulable |= EMU_ETHERNET;
  } else { ... clears both ... }

so a plain read-only answer makes Swiss DISABLE patch support on this device.
Default is therefore the honest GET|LIST (0x50) with patches disabled, and
--claim-owner reports OWNER to turn them back on -- flagged in the help as
unsafe for now, because this server has no UP_LOAD or MAKE_DIR, so Swiss
believing it can write here would make a patch write fail rather than degrade.
Try without it first.

T9 checks pos == 1 and that the flags land at buf[len] with GET|LIST and
without OWNER; T10 checks a missing directory gives CC_ERR so the fallback
chain works.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

scripts/fsp-server.py

@@ -40,6 +40,15 @@ import time
 CC_VERSION, CC_INFO = 0x10, 0x11
 CC_ERR, CC_GET_DIR, CC_GET_FILE = 0x40, 0x41, 0x42
 CC_BYE, CC_STAT = 0x4A, 0x4D
+CC_GET_PRO = 0x47
+# Directory protection bits (fsplib.h).  Swiss uses these to decide whether
+# the device supports patches:
+#   if ((pro & (MKDIR|ADD|DEL|GET)) == (MKDIR|ADD|DEL) || (pro & OWNER))
+#       features |= FEAT_PATCHES;  emulable |= EMU_ETHERNET;
+# so a plain read-only answer makes Swiss DISABLE patch support here.
+PRO_OWNER, PRO_DEL, PRO_ADD, PRO_MKDIR = 0x01, 0x02, 0x04, 0x08
+PRO_GET, PRO_README, PRO_LIST, PRO_RENAME = 0x10, 0x20, 0x40, 0x80
+PRO_BYTES = 1
 RDTYPE_END, RDTYPE_FILE, RDTYPE_DIR, RDTYPE_SKIP = 0x00, 0x01, 0x02, 0x2A
 HSIZE, FSP_SPACE = 12, 1024
 SERVER_KEY = 0x1234
@@ -128,6 +137,13 @@ def main():
     ap.add_argument("--port", type=int, default=21)
     ap.add_argument("--quiet-reads", action="store_true",
                     help="only log the rate, not every read")
+    ap.add_argument("--claim-owner", action="store_true",
+                    help="report FSP_DIR_OWNER on GET_PRO, which makes Swiss "
+                         "enable FEAT_PATCHES and EMU_ETHERNET on this device. "
+                         "⚠️ This server is READ-ONLY -- it has no UP_LOAD or "
+                         "MAKE_DIR -- so Swiss believing it can write here "
+                         "will make any patch write fail.  Try without it "
+                         "first; use it only if a boot demands patches.")
     a = ap.parse_args()
     root = os.path.realpath(a.root)
 
@@ -192,6 +208,25 @@ def main():
             s.sendto(pack(CC_STAT, SERVER_KEY, seq, pos, body), peer)
             continue
 
+        if cmd == CC_GET_PRO:
+            # Reply shape (fsplib fsp_getpro): pos MUST equal FSP_PRO_BYTES,
+            # and the flags byte sits at buf[len] -- i.e. the first byte of
+            # the EXTRA region, after the echoed name, not inside data.
+            # A non-existent directory must be CC_ERR so fsplib reports
+            # ENOENT: Swiss probes "swiss/patches", then "swiss", then "".
+            if not os.path.isdir(real):
+                s.sendto(pack(CC_ERR, SERVER_KEY, seq, pos, b"no such dir\0"), peer)
+                print(f"[{peer[0]}] GET_PRO {path!r} -> ENOENT (expected; "
+                      f"Swiss falls back)")
+                continue
+            pro = PRO_GET | PRO_LIST | (PRO_OWNER if a.claim_owner else 0)
+            s.sendto(pack(CC_GET_PRO, SERVER_KEY, seq, PRO_BYTES,
+                          path.encode("latin-1", "replace"), bytes([pro])), peer)
+            print(f"[{peer[0]}] GET_PRO {path!r} -> {pro:#04x}"
+                  + ("  (OWNER: Swiss will enable patches)" if a.claim_owner
+                     else "  (read-only: Swiss disables patches here)"))
+            continue
+
         if cmd == CC_GET_DIR:
             if not os.path.isdir(real):
                 s.sendto(pack(CC_ERR, SERVER_KEY, seq, pos, b"not a dir\0"), peer)