Add generic functions for library configuration

This is a new way to provide (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 this function prototype is as
agnostic as possible.

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.

Two examples of how to extend the configuration 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

doc/configuration_parameters.md

@@ -0,0 +1,9 @@
+
+# Configuration knobs
+
+TODO
+
+| Protocol | Parameter                          | Default value | Min value | Max value | Description |
+| ------   | ------                             | ------        | ------    | ------    | ------      |
+| NULL     | "packets_limit_per_flow"           | 32            | 0         | 255       | The upper limit on the number of packets per flow that will be subject to DPI, after which classification will be considered complete (0 = no limit)|
+| "tls" | "metadata.sha1_fingerprint.enable"    | 1             | NULL      | NULL      | Enable/disable computation and export of SHA1 fingerprint for TLS flows. Note that if it is disable, the flow risk `NDPI_MALICIOUS_SHA1_CERTIFICATE` is not checked |

example/ndpiReader.c

@@ -96,6 +96,16 @@ u_int8_t enable_protocol_guess = 1, enable_payload_analyzer = 0, num_bin_cluster
 u_int8_t verbose = 0, enable_flow_stats = 0;
 int stun_monitoring_pkts_to_process = -1; /* Default */
 int stun_monitoring_flags = -1; /* Default */
+
+struct cfg {
+  char *proto;
+  char *param;
+  char *value;
+};
+#define MAX_NUM_CFGS 16
+static struct cfg cfgs[MAX_NUM_CFGS];
+static int num_cfgs = 0;
+
 int nDPI_LogLevel = 0;
 char *_debug_protocols = NULL;
 char *_disabled_protocols = NULL;
@@ -594,11 +604,20 @@ static void help(u_int long_help) {
          "  --lru-cache-ttl=NAME:size        | Specify the TTL [in seconds] for this LRU cache (0 to disable it). This flag can be used multiple times\n"
          "  --stun-monitoring=<pkts>:<flags> | Configure STUN monitoring: keep monitoring STUN session for <pkts> more pkts looking for RTP\n"
          "                                   | (0:0 to disable the feature); set the specified features in <flags>\n"
+         "  --cfg=proto,param,value          | Configure the specific attribute of this protocol\n"
          ,
          human_readeable_string_len,
          min_pattern_len, max_pattern_len, max_num_packets_per_flow, max_packet_payload_dissection,
          max_num_reported_top_payloads, max_num_tcp_dissected_pkts, max_num_udp_dissected_pkts);
 
+  NDPI_PROTOCOL_BITMASK all;
+  ndpi_info_mod = ndpi_init_detection_module(init_prefs);
+  NDPI_BITMASK_SET_ALL(all);
+  ndpi_set_protocol_detection_bitmask2(ndpi_info_mod, &all);
+
+  printf("\nProtocols configuration parameters:\n");
+  ndpi_dump_config(ndpi_info_mod, stdout);
+
   printf("\nLRU Cache names: ookla, bittorrent, zoom, stun, tls_cert, mining, msteams, stun_zoom\n");
 
 #ifndef WIN32
@@ -621,24 +640,18 @@ static void help(u_int long_help) {
            ndpi_detection_get_sizeof_ndpi_flow_struct(),
            sizeof(((struct ndpi_flow_struct *)0)->protos));
 
-    NDPI_PROTOCOL_BITMASK all;
-
-    ndpi_info_mod = ndpi_init_detection_module(init_prefs);
     printf("\n\nnDPI supported protocols:\n");
     printf("%3s %-22s %-10s %-8s %-12s %s\n",
 	   "Id", "Protocol", "Layer_4", "Nw_Proto", "Breed", "Category");
     num_threads = 1;
 
-    NDPI_BITMASK_SET_ALL(all);
-    ndpi_set_protocol_detection_bitmask2(ndpi_info_mod, &all);
-
     ndpi_dump_protocols(ndpi_info_mod, stdout);
 
     printf("\n\nnDPI supported risks:\n");
     ndpi_dump_risks_score(stdout);
-
-    ndpi_exit_detection_module(ndpi_info_mod);
   }
+
+  ndpi_exit_detection_module(ndpi_info_mod);
 
   exit(!long_help);
 }
@@ -649,6 +662,8 @@ static void help(u_int long_help) {
 
 #define OPTLONG_VALUE_STUN_MONITORING	2000
 
+#define OPTLONG_VALUE_CFG		3000
+
 static struct option longopts[] = {
   /* mandatory extcap options */
   { "extcap-interfaces", no_argument, NULL, '0'},
@@ -694,6 +709,8 @@ static struct option longopts[] = {
   { "lru-cache-ttl", required_argument, NULL, OPTLONG_VALUE_LRU_CACHE_TTL},
   { "stun-monitoring", required_argument, NULL, OPTLONG_VALUE_STUN_MONITORING},
 
+  { "cfg", required_argument, NULL, OPTLONG_VALUE_CFG},
+
   {0, 0, 0, 0}
 };
 
@@ -950,6 +967,42 @@ static int parse_two_unsigned_integer(char *param, u_int32_t *num1, u_int32_t *n
   return -1;
 }
 
+static int parse_three_strings(char *param, char **s1, char **s2, char **s3)
+{
+  char *saveptr, *tmp_str, *s1_str, *s2_str = NULL, *s3_str;
+
+  tmp_str = ndpi_strdup(param);
+  if(tmp_str) {
+    if(param[0] == ',') { /* First parameter might be missing */
+      s1_str = NULL;
+      s2_str = strtok_r(tmp_str, ",", &saveptr);
+    } else {
+      s1_str = strtok_r(tmp_str, ",", &saveptr);
+      if(s1_str) {
+        s2_str = strtok_r(NULL, ",", &saveptr);
+      }
+    }
+    if(s2_str) {
+      s3_str = strtok_r(NULL, ",", &saveptr);
+      if(s3_str) {
+        *s1 = ndpi_strdup(s1_str);
+        *s2 = ndpi_strdup(s2_str);
+        *s3 = ndpi_strdup(s3_str);
+        ndpi_free(tmp_str);
+        if(!s1 || !s2 || !s3) {
+          ndpi_free(s1);
+          ndpi_free(s2);
+          ndpi_free(s3);
+          return -1;
+        }
+        return 0;
+      }
+    }
+  }
+  ndpi_free(tmp_str);
+  return -1;
+}
+
 /* ********************************** */
 
 /**
@@ -968,6 +1021,7 @@ static void parseOptions(int argc, char **argv) {
 #endif
   int cache_idx, cache_size, cache_ttl;
   u_int32_t num_pkts, flags;
+  char *s1, *s2, *s3;
 
 #ifdef USE_DPDK
   {
@@ -1316,6 +1370,18 @@ static void parseOptions(int argc, char **argv) {
       stun_monitoring_flags = flags;
       break;
 
+    case OPTLONG_VALUE_CFG:
+      if(num_cfgs >= MAX_NUM_CFGS ||
+	 parse_three_strings(optarg, &s1, &s2, &s3) == -1) {
+        printf("Invalid parameter [%s] [num:%d/%d]\n", optarg, num_cfgs, MAX_NUM_CFGS);
+        exit(1);
+      }
+      cfgs[num_cfgs].proto = s1;
+      cfgs[num_cfgs].param = s2;
+      cfgs[num_cfgs].value = s3;
+      num_cfgs++;
+      break;
+
     default:
 #ifdef DEBUG_TRACE
       if(trace) fprintf(trace, " #### Unknown option -%c: skipping it #### \n", opt);
@@ -2669,7 +2735,7 @@ static void debug_printf(u_int32_t protocol, void *id_struct,
 static void setupDetection(u_int16_t thread_id, pcap_t * pcap_handle) {
   NDPI_PROTOCOL_BITMASK enabled_bitmask;
   struct ndpi_workflow_prefs prefs;
-  int i;
+  int i, rc;
 
   memset(&prefs, 0, sizeof(prefs));
   prefs.decode_tunnels = decode_tunnels;
@@ -2757,6 +2823,14 @@ static void setupDetection(u_int16_t thread_id, pcap_t * pcap_handle) {
       ndpi_set_protocol_aggressiveness(ndpi_thread_info[thread_id].workflow->ndpi_struct, i, aggressiveness[i]);
   }
 
+  for(i = 0; i < num_cfgs; i++) {
+    rc = ndpi_set_config(ndpi_thread_info[thread_id].workflow->ndpi_struct,
+			 cfgs[i].proto, cfgs[i].param, cfgs[i].value);
+    if (rc != 0)
+      fprintf(stderr, "Error setting config [%s][%s][%s]: %d\n",
+	      cfgs[i].proto, cfgs[i].param, cfgs[i].value, rc);
+  }
+
   if(stun_monitoring_pkts_to_process != -1 &&
      stun_monitoring_flags != -1)
     ndpi_set_monitoring_state(ndpi_thread_info[thread_id].workflow->ndpi_struct, NDPI_PROTOCOL_STUN,
@@ -5684,6 +5758,12 @@ int main(int argc, char **argv) {
   ndpi_free(_debug_protocols);
   ndpi_free(_disabled_protocols);
 
+  for(i = 0; i < num_cfgs; i++) {
+    ndpi_free(cfgs[i].proto);
+    ndpi_free(cfgs[i].param);
+    ndpi_free(cfgs[i].value);
+  }
+
 #ifdef DEBUG_TRACE
   if(trace) fclose(trace);
 #endif

src/include/ndpi_api.h

@@ -2154,6 +2154,15 @@ extern "C" {
 
   /* ******************************* */
 
+  int 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'))

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 */
 

src/include/ndpi_typedefs.h

@@ -1068,7 +1068,6 @@ 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;
 
@@ -1154,6 +1153,14 @@ struct ndpi_risk_information {
   char *info;  
 };
 
+struct ndpi_detection_module_config_struct {
+  int max_packets_to_process;
+
+  /* TLS */
+  int sha1_fingerprint_enabled;
+
+};
+
 struct ndpi_flow_struct {
   u_int16_t detected_protocol_stack[NDPI_PROTOCOL_SIZE];