flow: add aux flags

Flow::flags field ran out of space, and for ABI compatibility the move
to u64 like in main isn't possible. So add a `aux_flags` field in an
alignment hole to facilitate the coming flags.

src/flow-util.h

@@ -49,6 +49,7 @@
         (f)->parent_id = 0;                                                                        \
         (f)->probing_parser_toserver_alproto_masks = 0;                                            \
         (f)->probing_parser_toclient_alproto_masks = 0;                                            \
+        (f)->aux_flags = 0;                                                                        \
         (f)->flags = 0;                                                                            \
         (f)->file_flags = 0;                                                                       \
         (f)->protodetect_dp = 0;                                                                   \
@@ -93,6 +94,7 @@
         (f)->parent_id = 0;                                                                        \
         (f)->probing_parser_toserver_alproto_masks = 0;                                            \
         (f)->probing_parser_toclient_alproto_masks = 0;                                            \
+        (f)->aux_flags = 0;                                                                        \
         (f)->flags = 0;                                                                            \
         (f)->file_flags = 0;                                                                       \
         (f)->protodetect_dp = 0;                                                                   \

src/flow.h

@@ -122,6 +122,8 @@ typedef struct AppLayerParserState_ AppLayerParserState;
 /** next packet in toserver direction will act on updated app-layer state */
 #define FLOW_TS_APP_UPDATE_NEXT BIT_U32(31)
 
+/* aux flags */
+
 /* File flags */
 
 #define FLOWFILE_INIT                   0
@@ -403,6 +405,10 @@ typedef struct Flow_
 
     FlowStateType flow_state;
 
+    /* additional flags: in >8 we updated the flags field to u64, but not breaking the ABI
+     * we add additional flags here. */
+    uint8_t aux_flags;
+
     /** flow tenant id, used to setup flow timeout and stream pseudo
      *  packets with the correct tenant id set */
     uint32_t tenant_id;