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, 14 deletions

diff --git a/src/lib/protocols/zattoo.c b/src/lib/protocols/zattoo.c
index 6b3e9625c..b5b305ecb 100644
--- a/src/lib/protocols/zattoo.c
+++ b/src/lib/protocols/zattoo.c
@@ -47,30 +47,16 @@ u_int8_t ndpi_int_zattoo_user_agent_set(struct ndpi_detection_module_struct *ndp
 }
 
 #define ZATTOO_DETECTED \
-      if (src != NULL)				 \
-	src->zattoo_ts = packet->current_time_ms; \
-      if (dst != NULL)				 \
-	dst->zattoo_ts = packet->current_time_ms; \
-						 \
       ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_ZATTOO, NDPI_PROTOCOL_UNKNOWN)
 
 void ndpi_search_zattoo(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
 {
   struct ndpi_packet_struct *packet = &ndpi_struct->packet;
-  struct ndpi_id_struct *src = flow->src;
-  struct ndpi_id_struct *dst = flow->dst;
 
   u_int16_t i;
 
   NDPI_LOG_DBG(ndpi_struct, "search ZATTOO\n");
 
-  if(flow->detected_protocol_stack[0] == NDPI_PROTOCOL_ZATTOO) {
-    if(src != NULL && ((u_int32_t) (packet->current_time_ms - src->zattoo_ts) < ndpi_struct->zattoo_connection_timeout))
-      src->zattoo_ts = packet->current_time_ms;
-    if (dst != NULL && ((u_int32_t) (packet->current_time_ms - dst->zattoo_ts) < ndpi_struct->zattoo_connection_timeout))
-      dst->zattoo_ts = packet->current_time_ms;
-    return;
-  }
   /* search over TCP */
   if(packet->tcp != NULL) {
     if(packet->payload_packet_len > 50 && memcmp(packet->payload, "GET /frontdoor/fd?brand=Zattoo&v=", 33) == 0) {