Remove `struct ndpi_id_struct` (#1427)

Remove the last uses of `struct ndpi_id_struct`.
That code is not really used and it has not been updated for a very long
time: see #1279 for details.

Correlation among flows is achieved via LRU caches.

This change allows to further reduce memory consumption (see also
91bb77a8).

At nDPI 4.0 (more precisly, at a6b10cf, because memory stats
were wrong until that commit):
```
nDPI Memory statistics:
	nDPI Memory (once):      221.15 KB
	Flow Memory (per flow):  2.94 KB
```
Now:
```
nDPI Memory statistics:
	nDPI Memory (once):      235.27 KB
	Flow Memory (per flow):  688 B        <--------
```
i.e. memory usage per flow has been reduced by 77%.

Close #1279

1 files changed, 3 insertions, 34 deletions

diff --git a/src/lib/ndpi_main.c b/src/lib/ndpi_main.c
index 200486bf0..063b65a54 100644
--- a/src/lib/ndpi_main.c
+++ b/src/lib/ndpi_main.c
@@ -246,12 +246,6 @@ u_int32_t ndpi_detection_get_sizeof_ndpi_flow_struct(void) {
 
 /* *********************************************************************************** */
 
-u_int32_t ndpi_detection_get_sizeof_ndpi_id_struct(void) {
-  return(sizeof(struct ndpi_id_struct));
-}
-
-/* *********************************************************************************** */
-
 u_int32_t ndpi_detection_get_sizeof_ndpi_flow_tcp_struct(void) {
   return(sizeof(struct ndpi_flow_tcp_struct));
 }
@@ -5279,7 +5273,7 @@ ndpi_protocol ndpi_detection_giveup(struct ndpi_detection_module_struct *ndpi_st
 
 void ndpi_process_extra_packet(struct ndpi_detection_module_struct *ndpi_str, struct ndpi_flow_struct *flow,
 			       const unsigned char *packet_data, const unsigned short packetlen,
-			       const u_int64_t current_time_ms, struct ndpi_id_struct *src, struct ndpi_id_struct *dst) {
+			       const u_int64_t current_time_ms) {
   if(flow == NULL)
     return;
 
@@ -5287,9 +5281,6 @@ void ndpi_process_extra_packet(struct ndpi_detection_module_struct *ndpi_str, st
   if(ndpi_init_packet(ndpi_str, flow, current_time_ms, packet_data, packetlen) != 0)
     return;
 
-  /* detect traffic for tcp or udp only */
-  flow->src = src, flow->dst = dst;
-
   ndpi_connection_tracking(ndpi_str, flow);
 
   /* call the extra packet function (which may add more data/info to flow) */
@@ -5633,8 +5624,7 @@ static int ndpi_do_guess(struct ndpi_detection_module_struct *ndpi_str, struct n
 
 ndpi_protocol ndpi_detection_process_packet(struct ndpi_detection_module_struct *ndpi_str,
 					    struct ndpi_flow_struct *flow, const unsigned char *packet_data,
-					    const unsigned short packetlen, const u_int64_t current_time_ms,
-					    struct ndpi_id_struct *src, struct ndpi_id_struct *dst) {
+					    const unsigned short packetlen, const u_int64_t current_time_ms) {
   struct ndpi_packet_struct *packet = &ndpi_str->packet;
   NDPI_SELECTION_BITMASK_PROTOCOL_SIZE ndpi_selection_packet;
   u_int32_t num_calls = 0;
@@ -5664,7 +5654,7 @@ ndpi_protocol ndpi_detection_process_packet(struct ndpi_detection_module_struct
     ret.app_protocol = flow->detected_protocol_stack[0];
 
   if(flow->check_extra_packets) {
-    ndpi_process_extra_packet(ndpi_str, flow, packet_data, packetlen, current_time_ms, src, dst);
+    ndpi_process_extra_packet(ndpi_str, flow, packet_data, packetlen, current_time_ms);
     /* Update in case of new match */
     ret.master_protocol = flow->detected_protocol_stack[1],
       ret.app_protocol = flow->detected_protocol_stack[0],
@@ -5679,9 +5669,6 @@ ndpi_protocol ndpi_detection_process_packet(struct ndpi_detection_module_struct
   if(ndpi_init_packet(ndpi_str, flow, current_time_ms, packet_data, packetlen) != 0)
     return ret;
 
-  /* detect traffic for tcp or udp only */
-  flow->src = src, flow->dst = dst;
-
   ndpi_connection_tracking(ndpi_str, flow);
 
   /* build ndpi_selection packet bitmask */
@@ -6419,23 +6406,7 @@ u_int8_t ndpi_detection_get_l4(const u_int8_t *l3, u_int16_t l3_len, const u_int
 void ndpi_set_detected_protocol(struct ndpi_detection_module_struct *ndpi_str, struct ndpi_flow_struct *flow,
 				u_int16_t upper_detected_protocol, u_int16_t lower_detected_protocol,
 				ndpi_confidence_t confidence) {
-  struct ndpi_id_struct *src = flow->src, *dst = flow->dst;
-
   ndpi_int_change_protocol(ndpi_str, flow, upper_detected_protocol, lower_detected_protocol, confidence);
-
-  if(src != NULL) {
-    NDPI_ADD_PROTOCOL_TO_BITMASK(src->detected_protocol_bitmask, upper_detected_protocol);
-
-    if(lower_detected_protocol != NDPI_PROTOCOL_UNKNOWN)
-      NDPI_ADD_PROTOCOL_TO_BITMASK(src->detected_protocol_bitmask, lower_detected_protocol);
-  }
-
-  if(dst != NULL) {
-    NDPI_ADD_PROTOCOL_TO_BITMASK(dst->detected_protocol_bitmask, upper_detected_protocol);
-
-    if(lower_detected_protocol != NDPI_PROTOCOL_UNKNOWN)
-      NDPI_ADD_PROTOCOL_TO_BITMASK(dst->detected_protocol_bitmask, lower_detected_protocol);
-  }
 }
 
 /* ********************************************************************************* */
@@ -6857,8 +6828,6 @@ const char *ndpi_confidence_get_name(ndpi_confidence_t confidence)
     return "Match by port";
   case NDPI_CONFIDENCE_MATCH_BY_IP:
     return "Match by IP";
-  case NDPI_CONFIDENCE_DPI_SRC_DST_ID:
-    return "DPI (src/dst ids)";
   case NDPI_CONFIDENCE_DPI_CACHE:
     return "DPI (cache)";
   case NDPI_CONFIDENCE_DPI: