A final(?) effort to reduce memory usage per flow (#1389)

Remove some unused fields and re-organize other ones.
In particular:
* Update the parameters of `ndpi_ssl_version2str()` function
* Zattoo, Thunder: these timestamps aren't really used.
* Ftp/mail: these protocols are dissected only over TCP.
* Attention must be paid to TLS.Bittorrent flows to avoid invalid
read/write to `flow->protos.bittorrent.hash` field.

This is the last(?) commit of a long series (see 22241a1d, 227e586e,
730c2360, a8ffcd8b) aiming to reduce library memory consumption.

Before, at nDPI 4.0 (more precisly, at a6b10cf7, 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):      231.71 KB
	Flow Memory (per flow):  1008 B       <---------
```
i.e. memory usage per flow has been reduced by 66%, dropping below the
psychological threshold of 1 KB.

To further reduce this value, we probably need to look into #1279:
let's fight this battle another day.

1 files changed, 0 insertions, 27 deletions

diff --git a/src/lib/protocols/thunder.c b/src/lib/protocols/thunder.c
index 31fa720d4..1b33c41d7 100644
--- a/src/lib/protocols/thunder.c
+++ b/src/lib/protocols/thunder.c
@@ -32,18 +32,7 @@
 static void ndpi_int_thunder_add_connection(struct ndpi_detection_module_struct *ndpi_struct, 
 					    struct ndpi_flow_struct *flow/* , ndpi_protocol_type_t protocol_type */)
 {
-  struct ndpi_packet_struct *packet = &ndpi_struct->packet;
-  struct ndpi_id_struct *src = flow->src;
-  struct ndpi_id_struct *dst = flow->dst;
-
   ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_THUNDER, NDPI_PROTOCOL_UNKNOWN);
-
-  if (src != NULL) {
-    src->thunder_ts = packet->current_time_ms;
-  }
-  if (dst != NULL) {
-    dst->thunder_ts = packet->current_time_ms;
-  }
 }
 
 
@@ -149,22 +138,6 @@ void ndpi_int_search_thunder_http(struct ndpi_detection_module_struct
   struct ndpi_id_struct *src = flow->src;
   struct ndpi_id_struct *dst = flow->dst;
 
-
-  if (flow->detected_protocol_stack[0] == NDPI_PROTOCOL_THUNDER) {
-    if (src != NULL && ((u_int32_t)
-			(packet->current_time_ms - src->thunder_ts) < ndpi_struct->thunder_timeout)) {
-      NDPI_LOG_DBG2(ndpi_struct,
-	       "thunder : save src connection packet detected\n");
-      src->thunder_ts = packet->current_time_ms;
-    } else if (dst != NULL && ((u_int32_t)
-			       (packet->current_time_ms - dst->thunder_ts) < ndpi_struct->thunder_timeout)) {
-      NDPI_LOG_DBG2(ndpi_struct,
-	       "thunder : save dst connection packet detected\n");
-      dst->thunder_ts = packet->current_time_ms;
-    }
-    return;
-  }
-
   if (packet->payload_packet_len > 5
       && memcmp(packet->payload, "GET /", 5) == 0 && NDPI_SRC_OR_DST_HAS_PROTOCOL(src, dst, NDPI_PROTOCOL_THUNDER)) {
     NDPI_LOG_DBG2(ndpi_struct, "HTTP packet detected\n");