detect: introduce 'minimal' detect engine

The minimal detect engine has only the minimal memory use and setup
time. It's to be used for 'delayed' detect where the first detection
engine is essentially empty.

The threads setup are also minimal.

src/detect-engine-mpm.c

@@ -817,7 +817,8 @@ void PatternMatchThreadPrint(MpmThreadCtx *mpm_thread_ctx, uint16_t mpm_matcher)
 void PatternMatchThreadDestroy(MpmThreadCtx *mpm_thread_ctx, uint16_t mpm_matcher)
 {
     SCLogDebug("mpm_thread_ctx %p, mpm_matcher %"PRIu16"", mpm_thread_ctx, mpm_matcher);
-    mpm_table[mpm_matcher].DestroyThreadCtx(NULL, mpm_thread_ctx);
+    if (mpm_table[mpm_matcher].DestroyThreadCtx != NULL)
+        mpm_table[mpm_matcher].DestroyThreadCtx(NULL, mpm_thread_ctx);
 }
 void PatternMatchThreadPrepare(MpmThreadCtx *mpm_thread_ctx, uint16_t mpm_matcher, uint32_t max_id)
 {

src/detect-engine.c

@@ -966,7 +966,7 @@ void DetectEngineSpawnLiveRuleSwapMgmtThread(void)
     SCReturn;
 }
 
-DetectEngineCtx *DetectEngineCtxInit(void)
+static DetectEngineCtx *DetectEngineCtxInitReal(int minimal)
 {
     DetectEngineCtx *de_ctx;
 
@@ -981,6 +981,12 @@ DetectEngineCtx *DetectEngineCtxInit(void)
 
     memset(de_ctx,0,sizeof(DetectEngineCtx));
 
+    if (minimal) {
+        de_ctx->minimal = 1;
+        de_ctx->id = detect_engine_ctx_id++;
+        return de_ctx;
+    }
+
     if (ConfGetBool("engine.init-failure-fatal", (int *)&(de_ctx->failure_fatal)) != 1) {
         SCLogDebug("ConfGetBool could not load the value.");
     }
@@ -1037,8 +1043,6 @@ DetectEngineCtx *DetectEngineCtxInit(void)
         goto error;
     }
 
-    de_ctx->id = detect_engine_ctx_id++;
-
     /* init iprep... ignore errors for now */
     (void)SRepInit(de_ctx);
 
@@ -1053,9 +1057,21 @@ DetectEngineCtx *DetectEngineCtxInit(void)
         goto error;
     }
 
+    de_ctx->id = detect_engine_ctx_id++;
     return de_ctx;
 error:
     return NULL;
+
+}
+
+DetectEngineCtx *DetectEngineCtxInitMinimal(void)
+{
+    return DetectEngineCtxInitReal(1);
+}
+
+DetectEngineCtx *DetectEngineCtxInit(void)
+{
+    return DetectEngineCtxInitReal(0);
 }
 
 static void DetectEngineCtxFreeThreadKeywordData(DetectEngineCtx *de_ctx)
@@ -1572,9 +1588,11 @@ TmEcode DetectEngineThreadCtxInit(ThreadVars *tv, void *initdata, void **data)
 #endif
     }
 
-    if (ThreadCtxDoInit(det_ctx->de_ctx, det_ctx) != TM_ECODE_OK) {
+    if (det_ctx->de_ctx->minimal == 0) {
-        DetectEngineThreadCtxDeinit(tv, det_ctx);
+        if (ThreadCtxDoInit(det_ctx->de_ctx, det_ctx) != TM_ECODE_OK) {
-        return TM_ECODE_FAILED;
+            DetectEngineThreadCtxDeinit(tv, det_ctx);
+            return TM_ECODE_FAILED;
+        }
     }
 
     /** alert counter setup */

src/detect-engine.h

@@ -57,6 +57,7 @@ extern DetectEngineAppInspectionEngine *app_inspection_engine[FLOW_PROTO_DEFAULT
 void DetectEngineRegisterAppInspectionEngines(void);
 void DetectEngineSpawnLiveRuleSwapMgmtThread(void);
 DetectEngineCtx *DetectEngineCtxInit(void);
+DetectEngineCtx *DetectEngineCtxInitMinimal(void);
 void DetectEngineCtxFree(DetectEngineCtx *);
 
 TmEcode DetectEngineThreadCtxInit(ThreadVars *, void *, void **);

src/detect.h

@@ -732,6 +732,9 @@ typedef struct DetectEngineCtx_ {
     struct SCProfileKeywordDetectCtx_ *profile_keyword_ctx_per_list[DETECT_SM_LIST_MAX];
 #endif
 
+    /** minimal: essentially a stub */
+    int minimal;
+
     /** how many de_ctx' are referencing this */
     uint32_t ref_cnt;
     /** list in master: either active or freelist */

src/suricata.c

@@ -2303,7 +2303,12 @@ int main(int argc, char **argv)
 
     DetectEngineCtx *de_ctx = NULL;
     if (!suri.disabled_detect) {
-        de_ctx = DetectEngineCtxInit();
+        SetupDelayedDetect(&suri);
+        if (!suri.delayed_detect) {
+            de_ctx = DetectEngineCtxInit();
+        } else {
+            de_ctx = DetectEngineCtxInitMinimal();
+        }
         if (de_ctx == NULL) {
             SCLogError(SC_ERR_INITIALIZATION, "initializing detection engine "
                     "context failed.");
@@ -2315,7 +2320,6 @@ int main(int argc, char **argv)
             CudaVarsSetDeCtx(de_ctx);
 #endif /* __SC_CUDA_SUPPORT__ */
 
-        SetupDelayedDetect(&suri);
         if (!suri.delayed_detect) {
             if (LoadSignatures(de_ctx, &suri) != TM_ECODE_OK)
                 exit(EXIT_FAILURE);