New API for library configuration

This is the first step into providing (more) configuration options in nDPI.

The idea is to have a simple way to configure (most of) nDPI: only one
function (`ndpi_set_config()`) to set any configuration parameters
(in the present or on in the future) and we try to keep this function
prototype as agnostic as possible.

You can configure the library:
* via API, using `ndpi_set_config()`
* via a configuration file, in a text format

This way, anytime we need to add a new configuration parameter:
* we don't need to add two public functions (a getter and a setter)
* we don't break API/ABI compatibility of the library; even changing
the parameter type (from integer to a list of integer, for example)
doesn't break the compatibility.

The complete list of configuration options is provided in
`doc/configuration_parameters.md`.

As a first example, two configuration knobs are provided:
* the ability to enable/disable the extraction of the sha1 fingerprint of
the TLS certificates.
* the upper limit on the number of packets per flow that will be subject
to inspection

5 files changed, 36 insertions, 4 deletions

diff --git a/src/include/ndpi_api.h b/src/include/ndpi_api.h
index 8bec8e3eb..3a5c7eccc 100644
--- a/src/include/ndpi_api.h
+++ b/src/include/ndpi_api.h
@@ -2246,6 +2246,15 @@ extern "C" {
 
   /* ******************************* */
 
+  ndpi_cfg_error ndpi_set_config(struct ndpi_detection_module_struct *ndpi_str,
+                                 const char *proto, const char *param, const char *value);
+  char *ndpi_get_config(struct ndpi_detection_module_struct *ndpi_str,
+			const char *proto, const char *param, char *buf, int buf_len);
+  char *ndpi_dump_config(struct ndpi_detection_module_struct *ndpi_str,
+			 FILE *fd);
+
+  /* ******************************* */
+
   /* Can't call libc functions from kernel space, define some stub instead */
 
 #define ndpi_isalpha(ch) (((ch) >= 'a' && (ch) <= 'z') || ((ch) >= 'A' && (ch) <= 'Z'))
diff --git a/src/include/ndpi_define.h.in b/src/include/ndpi_define.h.in
index 3a5585f12..3ec09ebdd 100644
--- a/src/include/ndpi_define.h.in
+++ b/src/include/ndpi_define.h.in
@@ -153,7 +153,6 @@
 
 /* misc definitions */
 #define NDPI_DEFAULT_MAX_TCP_RETRANSMISSION_WINDOW_SIZE 0x10000
-#define NDPI_DEFAULT_MAX_NUM_PKTS_PER_FLOW_TO_DISSECT   32
 
 /* TODO: rebuild all memory areas to have a more aligned memory block here */
 
diff --git a/src/include/ndpi_private.h b/src/include/ndpi_private.h
index df3bfaf2c..d4ff2461f 100644
--- a/src/include/ndpi_private.h
+++ b/src/include/ndpi_private.h
@@ -144,13 +144,24 @@ typedef struct {
 } nbpf_filter;
 #endif
 
+#define CFG_MAX_LEN	256
+
+struct ndpi_detection_module_config_struct {
+  int max_packets_to_process;
+
+  char filename_config[CFG_MAX_LEN];
+
+  /* Protocols */
+
+  int tls_sha1_fingerprint_enabled;
+};
+
 struct ndpi_detection_module_struct {
   NDPI_PROTOCOL_BITMASK detection_bitmask;
 
   u_int64_t current_ts;
-  u_int16_t max_packets_to_process;
   u_int16_t num_tls_blocks_to_follow;
-  u_int8_t skip_tls_blocks_until_change_cipher:1, _notused:7;
+  u_int8_t skip_tls_blocks_until_change_cipher:1, finalized:1, _notused:6;
   u_int8_t tls_certificate_expire_in_x_days;
 
   void *user_data;
@@ -226,6 +237,8 @@ struct ndpi_detection_module_struct {
 
   u_int8_t ip_version_limit;
 
+  struct ndpi_detection_module_config_struct cfg;
+
   /* NDPI_PROTOCOL_TINC */
   struct cache *tinc_cache;
 
diff --git a/src/include/ndpi_typedefs.h b/src/include/ndpi_typedefs.h
index 792aea9ee..3ed4ee50c 100644
--- a/src/include/ndpi_typedefs.h
+++ b/src/include/ndpi_typedefs.h
@@ -234,6 +234,14 @@ typedef enum {
    ndpi_leaf
 } ndpi_VISIT;
 
+typedef enum {
+  NDPI_CFG_INVALID_CONTEXT = -1,
+  NDPI_CFG_NOT_FOUND = -2,
+  NDPI_CFG_INVALID_PARAM = -3,
+  NDPI_CFG_CONTEXT_ALREADY_INITIALIZED = -4,
+
+  NDPI_CFG_OK = 0,
+} ndpi_cfg_error;
 
 /* NDPI_MASK_SIZE */
 typedef u_int32_t ndpi_ndpi_mask;
@@ -1065,7 +1073,6 @@ typedef enum {
 
 typedef enum {
    ndpi_pref_direction_detect_disable = 0,
-   ndpi_pref_max_packets_to_process,
    ndpi_pref_enable_tls_block_dissection, /* nDPI considers only those blocks past the certificate exchange */
 } ndpi_detection_preference;
 
diff --git a/src/include/ndpi_win32.h b/src/include/ndpi_win32.h
index 2ad8602aa..c6b3290f6 100644
--- a/src/include/ndpi_win32.h
+++ b/src/include/ndpi_win32.h
@@ -59,6 +59,10 @@
 #define strdup _strdup
 #endif
 
+#ifndef F_OK
+#define F_OK 0
+#endif
+
 extern char* strsep(char **sp, char *sep);
 
 typedef unsigned char  u_char;