detect: inspect all packets in multi-layer tunneling

When the decoders encounter multiple layers of tunneling, multiple tunnel
packets are created. These are then stored in ThreadVars::decode_pq, where
they are processed after the current thread "slot" is done. However, due
to a logic error, the tunnel packets after the first, where not called
for the correct position in the packet pipeline. This would lead to these
packets not going through the FlowWorker module, so skipping everything
from flow tracking, detection and logging.

This would only happen for single and workers, due to how the pipelines
are constructed.

This patch addresses the issue by making sure only a "decode" thread
slot will service the ThreadVars::decode_pq.

Bug: OISF#6402.

src/tm-threads.c

@@ -142,9 +142,11 @@ TmEcode TmThreadsSlotVarRun(ThreadVars *tv, Packet *p, TmSlot *slot)
             TmThreadsSlotProcessPktFail(tv, s, NULL);
             return TM_ECODE_FAILED;
         }
-
-        if (TmThreadsProcessDecodePseudoPackets(tv, &tv->decode_pq, s->slot_next) != TM_ECODE_OK) {
-            return TM_ECODE_FAILED;
+        if (s->tm_flags & TM_FLAG_DECODE_TM) {
+            if (TmThreadsProcessDecodePseudoPackets(tv, &tv->decode_pq, s->slot_next) !=
+                    TM_ECODE_OK) {
+                return TM_ECODE_FAILED;
+            }
         }
     }
 
@@ -661,6 +663,7 @@ void TmSlotSetFuncAppend(ThreadVars *tv, TmModule *tm, const void *data)
     /* we don't have to check for the return value "-1".  We wouldn't have
      * received a TM as arg, if it didn't exist */
     slot->tm_id = TmModuleGetIDForTM(tm);
+    slot->tm_flags |= tm->flags;
 
     tv->tmm_flags |= tm->flags;
     tv->cap_flags |= tm->cap_flags;

src/tm-threads.h

@@ -63,14 +63,18 @@ typedef struct TmSlot_ {
 
     SC_ATOMIC_DECLARE(void *, slot_data);
 
+    /** copy of the TmModule::flags */
+    uint8_t tm_flags;
+
+    /* store the thread module id */
+    int tm_id;
+
     TmEcode (*SlotThreadInit)(ThreadVars *, const void *, void **);
     void (*SlotThreadExitPrintStats)(ThreadVars *, void *);
     TmEcode (*SlotThreadDeinit)(ThreadVars *, void *);
 
     /* data storage */
     const void *slot_initdata;
-    /* store the thread module id */
-    int tm_id;
 
 } TmSlot;