config: follow-up (#2268)

Some changes in the parameters names.
Add a fuzzer to fuzz the configuration file format.
Add the infrastructure to configuratin callbacks.
Add an helper to map LRU cache indexes to names.

fuzz/fuzz_filecfg_config.c

@@ -0,0 +1,27 @@
+#include "ndpi_api.h"
+#include "ndpi_private.h"
+#include "fuzz_common_code.h"
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+  struct ndpi_detection_module_struct *ndpi_struct;
+  FILE *fd;
+  NDPI_PROTOCOL_BITMASK all;
+
+  /* To allow memory allocation failures */
+  fuzz_set_alloc_callbacks_and_seed(size);
+
+  ndpi_struct = ndpi_init_detection_module();
+  NDPI_BITMASK_SET_ALL(all);
+  ndpi_set_protocol_detection_bitmask2(ndpi_struct, &all);
+
+  ndpi_set_config(ndpi_struct, NULL, "log.level", "3");
+  ndpi_set_config(ndpi_struct, "all", "log", "1");
+
+  fd = buffer_to_file(data, size);
+  load_config_file_fd(ndpi_struct, fd);
+  if(fd)
+    fclose(fd);
+
+  ndpi_exit_detection_module(ndpi_struct);
+  return 0;
+}