Refactor z2z and additionally set ac_private=1 when loading block index from disk

This should avoid the edge case when a node starts up after the z2z block height but
has not yet seen a new block and so does not yet know it is an -ac_private=1 chain,
as currently that is set in ConnectBlock.

src/main.cpp

@@ -114,6 +114,8 @@ bool fAlerts = DEFAULT_ALERTS;
 /* If the tip is older than this (in seconds), the node is considered to be in initial block download.
  */
 int64_t nMaxTipAge = DEFAULT_MAX_TIP_AGE;
+bool ishush3 = strncmp(ASSETCHAINS_SYMBOL, "HUSH3",5) == 0 ? true : false;
+unsigned int z2zForkHeight = 340000;
 
 unsigned int expiryDelta = DEFAULT_TX_EXPIRY_DELTA;
 extern char ASSETCHAINS_SYMBOL[KOMODO_ASSETCHAIN_MAXLEN];
@@ -1742,14 +1744,12 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
 {
     AssertLockHeld(cs_main);
     uint32_t z2zTransitionWindow = 10;
-    uint32_t z2zTransitionStart  = 340000 - z2zTransitionWindow;
-    uint32_t z2zTransitionEnd    = 340000;
-    bool ishush3 = strncmp(ASSETCHAINS_SYMBOL, "HUSH3",5) == 0 ? true : false;
-    uint32_t nHeight = chainActive.Height();
+    uint32_t z2zTransitionStart  = z2zForkHeight - z2zTransitionWindow;
+    uint32_t nHeight             = chainActive.Height();
 
     // This only applies to HUSH3, other chains can start off z2z via ac_private=1
     if(ishush3) {
-        if((nHeight >= z2zTransitionStart) || (nHeight <= z2zTransitionEnd)) {
+        if((nHeight >= z2zTransitionStart) || (nHeight <= z2zForkHeight)) {
             // During the z2z transition window, only coinbase tx's as part of blocks are allowed
             // Theory: We want an empty mempool at our fork block height, and the only way to assure that
             // is to have an empty mempool for a few previous blocks, to take care of potential re-orgs
@@ -3371,7 +3371,6 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
 
     bool ishush3 = strncmp(ASSETCHAINS_SYMBOL, "HUSH3",5) == 0 ? true : false;
     if(!ASSETCHAINS_PRIVATE && ishush3) {
-        unsigned int z2zForkHeight = 340000;
         unsigned int nHeight       = pindex->GetHeight();
         if(nHeight >= z2zForkHeight) {
             // At startup, HUSH3 doesn't know a block height yet and so we must wait until
@@ -6338,6 +6337,13 @@ bool static LoadBlockIndexDB()
 
     chainActive.SetTip(it->second);
 
+    // Try to detect if we are z2z based on height of blocks on disk
+    // This helps to set it correctly on startup before a new block is connected
+    if(ishush3 && chainActive.Height() >= z2zForkHeight) {
+        LogPrintf("%s: enabled ac_private=1 at height=%d\n", __func__, chainActive.Height());
+        ASSETCHAINS_PRIVATE = 1;
+    }
+
     // Set hashFinalSproutRoot for the end of best chain
     it->second->hashFinalSproutRoot = pcoinsTip->GetBestAnchor(SPROUT);