gcoap/fileserver: recursive directory deletion as default

sys/include/net/gcoap/fileserver.h

@@ -26,8 +26,10 @@
  * In opposite, the If-None-Match option requires a request to be processed,
  * only if the resource does not yet exist, and is most useful for file creation.
  *
- * Directories are expressed to URIs with trailing slashes and can be DELETEd
- * when empty.
+ * Directories are expressed to URIs with trailing slashes. Directories and
+ * their content are deleted as if one would do an `$rm -r`. If you only would
+ * like to delete a directory if it is empty, you must supply an If-Match option
+ * with the special value @ref COAPFILESERVER_DIR_DELETE_ETAG.
  *
  * @note The file server uses ETag for cache validation. The ETags are built
  * from the file system stat values. As clients rely on the ETag to differ when
@@ -80,6 +82,12 @@ extern "C" {
 
 #include "net/nanocoap.h"
 
+/**
+ * @brief   Randomly generated Etag, used by a client when a directory should only be
+ *          deleted, if it is empty
+ */
+#define COAPFILESERVER_DIR_DELETE_ETAG (0x6ce88b56u)
+
 /**
  * @brief File server handler
  *

sys/net/application_layer/gcoap/fileserver.c

@@ -25,6 +25,7 @@
 #include "net/gcoap/fileserver.h"
 #include "net/gcoap.h"
 #include "vfs.h"
+#include "vfs_util.h"
 
 #define ENABLE_DEBUG 0
 #include "debug.h"
@@ -456,10 +457,19 @@ static ssize_t _delete_directory(coap_pkt_t *pdu, uint8_t *buf, size_t len,
 {
     int err;
     if (request->options.exists.if_match && request->options.if_match_len) {
-        return gcoap_fileserver_error_handler(pdu, buf, len, COAP_CODE_PRECONDITION_FAILED);
+        if (request->options.if_match != byteorder_htonl(COAPFILESERVER_DIR_DELETE_ETAG).u32) {
+            return gcoap_fileserver_error_handler(pdu, buf, len, COAP_CODE_PRECONDITION_FAILED);
+        }
+        if ((err = vfs_rmdir(request->namebuf)) < 0) {
+            return gcoap_fileserver_error_handler(pdu, buf, len, err);
+        }
     }
-    if ((err = vfs_rmdir(request->namebuf)) < 0) {
-        return gcoap_fileserver_error_handler(pdu, buf, len, err);
+    else if (IS_USED(MODULE_VFS_UTIL)) {
+        if ((err = vfs_unlink_recursive(request->namebuf,
+                                        request->namebuf,
+                                        sizeof(request->namebuf))) < 0) {
+            gcoap_fileserver_error_handler(pdu, buf, len, err);
+        }
     }
     gcoap_resp_init(pdu, buf, len, COAP_CODE_DELETED);
     return coap_opt_finish(pdu, COAP_OPT_FINISH_NONE);