mpm: improve SGH content len tracking

SGH's track content length for rule grouping.

This patch changes the logic to only consider the pattern that is
used in the mpm for a sig.

src/detect-engine-siggroup.c

@@ -998,6 +998,17 @@ void SigGroupHeadFreeMpmArrays(DetectEngineCtx *de_ctx)
     return;
 }
 
+static uint16_t SignatureGetMpmPatternLen(Signature *s, int list)
+{
+    if (s->sm_lists[list] != NULL && s->mpm_sm != NULL &&
+        SigMatchListSMBelongsTo(s, s->mpm_sm) == list)
+    {
+        DetectContentData *cd = (DetectContentData *)s->mpm_sm->ctx;
+        return cd->content_len;
+    }
+    return 0;
+}
+
 /**
  * \brief Add a Signature to a SigGroupHead.
  *
@@ -1028,12 +1039,13 @@ int SigGroupHeadAppendSig(DetectEngineCtx *de_ctx, SigGroupHead **sgh,
     /* update maxlen for mpm */
     if (s->sm_lists[DETECT_SM_LIST_PMATCH] != NULL) {
         /* check with the precalculated values from the sig */
-        if (s->mpm_content_maxlen > 0) {
+        uint16_t mpm_content_minlen = SignatureGetMpmPatternLen(s, DETECT_SM_LIST_PMATCH);
+        if (mpm_content_minlen > 0) {
             if ((*sgh)->mpm_content_maxlen == 0)
-                (*sgh)->mpm_content_maxlen = s->mpm_content_maxlen;
+                (*sgh)->mpm_content_maxlen = mpm_content_minlen;
 
-            if ((*sgh)->mpm_content_maxlen > s->mpm_content_maxlen)
-                (*sgh)->mpm_content_maxlen = s->mpm_content_maxlen;
+            if ((*sgh)->mpm_content_maxlen > mpm_content_minlen)
+                (*sgh)->mpm_content_maxlen = mpm_content_minlen;
 
             SCLogDebug("(%p)->mpm_content_maxlen %u", *sgh, (*sgh)->mpm_content_maxlen);
         }
@@ -1608,15 +1620,12 @@ uint16_t SigGroupHeadGetMinMpmSize(DetectEngineCtx *de_ctx,
         s = sgh->match_array[sig];
         if (s == NULL)
             continue;
-        if (s->sm_lists[list] == NULL)
-            continue;
 
-        if (s->mpm_sm != NULL && SigMatchListSMBelongsTo(s, s->mpm_sm) == list)
-        {
-            DetectContentData *cd = (DetectContentData *)s->mpm_sm->ctx;
-            if (cd->content_len < min)
-                min = cd->content_len;
-            SCLogDebug("cd->content_len %u", cd->content_len);
+        uint16_t mpm_content_minlen = SignatureGetMpmPatternLen(s, DETECT_SM_LIST_PMATCH);
+        if (mpm_content_minlen > 0) {
+            if (mpm_content_minlen < min)
+                min = mpm_content_minlen;
+            SCLogDebug("mpm_content_minlen %u", mpm_content_minlen);
         }
     }
 

src/detect-parse.c

@@ -1345,7 +1345,6 @@ int SigValidate(DetectEngineCtx *de_ctx, Signature *s)
 static Signature *SigInitHelper(DetectEngineCtx *de_ctx, char *sigstr,
                                 uint8_t dir)
 {
-    SigMatch *sm;
     Signature *sig = SigAlloc();
     if (sig == NULL)
         goto error;
@@ -1390,24 +1389,6 @@ static Signature *SigInitHelper(DetectEngineCtx *de_ctx, char *sigstr,
     if (DetectAppLayerEventPrepare(sig) < 0)
         goto error;
 
-    /* determine the length of the longest pattern in the sig */
-    if (sig->sm_lists[DETECT_SM_LIST_PMATCH] != NULL) {
-        sig->mpm_content_maxlen = 0;
-
-        for (sm = sig->sm_lists[DETECT_SM_LIST_PMATCH]; sm != NULL; sm = sm->next) {
-            if (sm->type == DETECT_CONTENT) {
-                DetectContentData *cd = (DetectContentData *)sm->ctx;
-                 if (cd == NULL)
-                    continue;
-
-                if (sig->mpm_content_maxlen == 0)
-                    sig->mpm_content_maxlen = cd->content_len;
-                if (sig->mpm_content_maxlen < cd->content_len)
-                    sig->mpm_content_maxlen = cd->content_len;
-            }
-        }
-    }
-
     /* set the packet and app layer flags, but only if the
      * app layer flag wasn't already set in which case we
      * only consider the app layer */
@@ -3250,11 +3231,6 @@ int SigParseTestMpm01 (void)
         goto end;
     }
 
-    if (sig->mpm_content_maxlen != 4) {
-        printf("mpm content max len %"PRIu16", expected 4: ", sig->mpm_content_maxlen);
-        goto end;
-    }
-
     result = 1;
 end:
     if (sig != NULL)
@@ -3286,11 +3262,6 @@ int SigParseTestMpm02 (void)
         goto end;
     }
 
-    if (sig->mpm_content_maxlen != 6) {
-        printf("mpm content max len %"PRIu16", expected 6: ", sig->mpm_content_maxlen);
-        goto end;
-    }
-
     result = 1;
 end:
     if (sig != NULL)

src/detect.c

@@ -9792,10 +9792,6 @@ static int SigTestSgh01 (void)
         printf("internal id != 0: ");
         goto end;
     }
-    if (de_ctx->sig_list->mpm_content_maxlen != 3) {
-        printf("de_ctx->sig_list->mpm_content_maxlen %u, expected 3: ", de_ctx->sig_list->mpm_content_maxlen);
-        goto end;
-    }
 
     de_ctx->sig_list->next = SigInit(de_ctx,"alert tcp any any -> any 81 (msg:\"2\"; content:\"two\"; content:\"abcd\"; sid:2;)");
     if (de_ctx->sig_list->next == NULL) {
@@ -9806,10 +9802,6 @@ static int SigTestSgh01 (void)
         printf("internal id != 1: ");
         goto end;
     }
-    if (de_ctx->sig_list->next->mpm_content_maxlen != 4) {
-        printf("de_ctx->sig_list->mpm_content_maxlen %u, expected 4: ", de_ctx->sig_list->next->mpm_content_maxlen);
-        goto end;
-    }
 
     de_ctx->sig_list->next->next = SigInit(de_ctx,"alert tcp any any -> any 80 (msg:\"3\"; content:\"three\"; sid:3;)");
     if (de_ctx->sig_list->next->next == NULL) {
@@ -9820,10 +9812,6 @@ static int SigTestSgh01 (void)
         printf("internal id != 2: ");
         goto end;
     }
-    if (de_ctx->sig_list->next->next->mpm_content_maxlen != 5) {
-        printf("de_ctx->sig_list->next->next->mpm_content_maxlen %u, expected 5: ", de_ctx->sig_list->next->next->mpm_content_maxlen);
-        goto end;
-    }
 
     SigGroupBuild(de_ctx);
     DetectEngineThreadCtxInit(&th_v, (void *)de_ctx, (void *)&det_ctx);

src/detect.h

@@ -450,10 +450,6 @@ typedef struct Signature_ {
     /* the fast pattern added from this signature */
     SigMatch *mpm_sm;
 
-    /* track max length for content. Indirectly used in grouping:
-     * used to set SigGroupHead::mpm_content_maxlen */
-    uint16_t mpm_content_maxlen;
-
     /* SigMatch list used for adding content and friends. E.g. file_data; */
     int list;