stats: Track stream reassembly drops

Issue: 6235
(cherry picked from commit 904f0ddeee)

src/decode.c

@@ -794,6 +794,8 @@ const char *PacketDropReasonToString(enum PacketDropReason r)
             return "stream memcap";
         case PKT_DROP_REASON_STREAM_MIDSTREAM:
             return "stream midstream";
+        case PKT_DROP_REASON_STREAM_REASSEMBLY:
+            return "stream reassembly";
         case PKT_DROP_REASON_APPLAYER_ERROR:
             return "applayer error";
         case PKT_DROP_REASON_APPLAYER_MEMCAP:

src/decode.h

@@ -411,6 +411,7 @@ enum PacketDropReason {
     PKT_DROP_REASON_STREAM_ERROR,
     PKT_DROP_REASON_STREAM_MEMCAP,
     PKT_DROP_REASON_STREAM_MIDSTREAM,
+    PKT_DROP_REASON_STREAM_REASSEMBLY,
 };
 
 /* forward declaration since Packet struct definition requires this */

src/stream-tcp-reassemble.c

@@ -1903,7 +1903,7 @@ int StreamTcpReassembleHandleSegment(ThreadVars *tv, TcpReassemblyThreadCtx *ra_
             SCLogDebug("StreamTcpReassembleHandleSegmentHandleData error");
             /* failure can only be because of memcap hit, so see if this should lead to a drop */
             ExceptionPolicyApply(
-                    p, stream_config.reassembly_memcap_policy, PKT_DROP_REASON_STREAM_MEMCAP);
+                    p, stream_config.reassembly_memcap_policy, PKT_DROP_REASON_STREAM_REASSEMBLY);
             SCReturnInt(-1);
         }