eve/flow: log tx_cnt

This patch adds a `tx_cnt` field to `netflow` events to give some
context about the underlying protocol activity.

Ticket: #7635

etc/schema.json

@@ -1982,6 +1982,9 @@
                 },
                 "wrong_thread": {
                     "type": "boolean"
+                },
+                "tx_cnt": {
+                    "type": "integer"
                 }
             },
             "additionalProperties": false

src/output-json-flow.c

@@ -27,6 +27,7 @@
 #include "detect.h"
 #include "pkt-var.h"
 #include "conf.h"
+#include "app-layer-parser.h"
 
 #include "threads.h"
 #include "threadvars.h"
@@ -350,6 +351,13 @@ static void EveFlowLogJSON(OutputJsonThreadCtx *aft, SCJsonBuilder *jb, Flow *f)
         SCJbClose(jb); /* close array */
     }
 
+    if (f->alstate) {
+        uint64_t tx_id = AppLayerParserGetTxCnt(f, f->alstate);
+        if (tx_id) {
+            SCJbSetUint(jb, "tx_cnt", tx_id);
+        }
+    }
+
     /* Close flow. */
     SCJbClose(jb);