detect/state: fix reset bug

Fix issue where after a reset the now empty list elements are not
reused and the values may not be valid for the current detect
engine anymore.

Introduce a 'current' (cur) pointer that points to the store element
currently being filled. This way existing stores will be reused.

If 'cur' is NULL and 'head' is not NULL it means we need to use
'tail' to append a new store.

src/detect-engine-state.c

@@ -1,4 +1,4 @@
-/* Copyright (C) 2007-2013 Open Information Security Foundation
+/* Copyright (C) 2007-2021 Open Information Security Foundation
  *
  * You can copy, redistribute or modify this Program under the terms of
  * the GNU General Public License version 2 as published by the Free
@@ -131,28 +131,32 @@ static void DeStateSignatureAppend(DetectEngineState *state,
     BUG_ON(DeStateSearchState(state, direction, s->num));
 #endif
     DeStateStore *store = dir_state->tail;
-
     if (store == NULL) {
         store = DeStateStoreAlloc();
         dir_state->head = store;
+        dir_state->cur = store;
         dir_state->tail = store;
+    } else if (dir_state->cur) {
+        store = dir_state->cur;
     } else {
-        SCLogDebug("dir_state->cnt %u mod chunksize %u", dir_state->cnt,
-                dir_state->cnt % DE_STATE_CHUNK_SIZE);
-        if (dir_state->cnt && dir_state->cnt % DE_STATE_CHUNK_SIZE == 0) {
-            store = DeStateStoreAlloc();
-            if (store != NULL) {
-                dir_state->tail->next = store;
-                dir_state->tail = store;
-            }
+        store = DeStateStoreAlloc();
+        if (store != NULL) {
+            dir_state->tail->next = store;
+            dir_state->tail = store;
+            dir_state->cur = store;
         }
     }
     if (store == NULL)
         SCReturn;
 
-    SigIntId idx = dir_state->cnt++ % DE_STATE_CHUNK_SIZE;
+    SigIntId idx = dir_state->cnt % DE_STATE_CHUNK_SIZE;
     store->store[idx].sid = s->num;
     store->store[idx].flags = inspect_flags;
+    dir_state->cnt++;
+    /* if current chunk is full, progress cur */
+    if (dir_state->cnt % DE_STATE_CHUNK_SIZE == 0) {
+        dir_state->cur = dir_state->cur->next;
+    }
 
     SCReturn;
 }
@@ -261,10 +265,14 @@ static inline void ResetTxState(DetectEngineState *s)
         s->dir_state[0].cnt = 0;
         s->dir_state[0].filestore_cnt = 0;
         s->dir_state[0].flags = 0;
+        /* reset 'cur' back to the list head */
+        s->dir_state[0].cur = s->dir_state[0].head;
 
         s->dir_state[1].cnt = 0;
         s->dir_state[1].filestore_cnt = 0;
         s->dir_state[1].flags = 0;
+        /* reset 'cur' back to the list head */
+        s->dir_state[1].cur = s->dir_state[1].head;
     }
 }
 
@@ -313,14 +321,14 @@ static int DeStateTest01(void)
 
 static int DeStateTest02(void)
 {
+    uint8_t direction = STREAM_TOSERVER;
     DetectEngineState *state = DetectEngineStateAlloc();
     FAIL_IF_NULL(state);
+    FAIL_IF_NOT_NULL(state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].head);
 
     Signature s;
     memset(&s, 0x00, sizeof(s));
 
-    uint8_t direction = STREAM_TOSERVER;
-
     s.num = 0;
     DeStateSignatureAppend(state, &s, 0, direction);
     s.num = 11;
@@ -349,10 +357,23 @@ static int DeStateTest02(void)
     DeStateSignatureAppend(state, &s, 0, direction);
     s.num = 133;
     DeStateSignatureAppend(state, &s, 0, direction);
+    FAIL_IF_NOT(state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].head ==
+                state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].cur);
+
     s.num = 144;
     DeStateSignatureAppend(state, &s, 0, direction);
+
+    FAIL_IF(state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].head->store[14].sid != 144);
+    FAIL_IF(state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].head ==
+            state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].cur);
+    FAIL_IF_NOT(state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].cur == NULL);
+
     s.num = 155;
     DeStateSignatureAppend(state, &s, 0, direction);
+
+    FAIL_IF_NOT(state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].tail ==
+                state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].cur);
+
     s.num = 166;
     DeStateSignatureAppend(state, &s, 0, direction);
 
@@ -365,6 +386,10 @@ static int DeStateTest02(void)
 
     ResetTxState(state);
 
+    FAIL_IF(state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].head == NULL);
+    FAIL_IF_NOT(state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].head ==
+                state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].cur);
+
     s.num = 0;
     DeStateSignatureAppend(state, &s, 0, direction);
     s.num = 11;
@@ -393,8 +418,15 @@ static int DeStateTest02(void)
     DeStateSignatureAppend(state, &s, 0, direction);
     s.num = 133;
     DeStateSignatureAppend(state, &s, 0, direction);
+    FAIL_IF_NOT(state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].head ==
+                state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].cur);
     s.num = 144;
     DeStateSignatureAppend(state, &s, 0, direction);
+    FAIL_IF(state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].head->store[14].sid != 144);
+    FAIL_IF(state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].head ==
+            state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].cur);
+    FAIL_IF_NOT(state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].tail ==
+                state->dir_state[direction & STREAM_TOSERVER ? 0 : 1].cur);
     s.num = 155;
     DeStateSignatureAppend(state, &s, 0, direction);
     s.num = 166;

src/detect-engine-state.h

@@ -81,8 +81,9 @@ typedef struct DeStateStore_ {
 } DeStateStore;
 
 typedef struct DetectEngineStateDirection_ {
-    DeStateStore *head;
-    DeStateStore *tail;
+    DeStateStore *head; /**< head of the list */
+    DeStateStore *cur;  /**< current active store */
+    DeStateStore *tail; /**< tail of the list */
     SigIntId cnt;
     uint16_t filestore_cnt;
     uint8_t flags;