Auto merge of #3443 - daira:testnet-rollback, r=str4d

Support testnet rollback.

Part of #1302. Closes #2905.

src/init.cpp

@@ -1434,6 +1434,8 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
     LogPrintf("* Using %.1fMiB for chain state database\n", nCoinDBCache * (1.0 / 1024 / 1024));
     LogPrintf("* Using %.1fMiB for in-memory UTXO set\n", nCoinCacheUsage * (1.0 / 1024 / 1024));
 
+    bool clearWitnessCaches = false;
+
     bool fLoaded = false;
     while (!fLoaded) {
         bool fReset = fReindex;
@@ -1493,7 +1495,7 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
 
                 if (!fReindex) {
                     uiInterface.InitMessage(_("Rewinding blocks if needed..."));
-                    if (!RewindBlockIndex(chainparams)) {
+                    if (!RewindBlockIndex(chainparams, clearWitnessCaches)) {
                         strLoadError = _("Unable to rewind the database to a pre-upgrade state. You will need to redownload the blockchain");
                         break;
                     }
@@ -1643,7 +1645,7 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
         RegisterValidationInterface(pwalletMain);
 
         CBlockIndex *pindexRescan = chainActive.Tip();
-        if (GetBoolArg("-rescan", false))
+        if (clearWitnessCaches || GetBoolArg("-rescan", false))
         {
             pwalletMain->ClearNoteWitnessCache();
             pindexRescan = chainActive.Genesis();

src/main.cpp

@@ -4217,7 +4217,7 @@ bool CVerifyDB::VerifyDB(CCoinsView *coinsview, int nCheckLevel, int nCheckDepth
     return true;
 }
 
-bool RewindBlockIndex(const CChainParams& params)
+bool RewindBlockIndex(const CChainParams& params, bool& clearWitnessCaches)
 {
     LOCK(cs_main);
 
@@ -4249,23 +4249,45 @@ bool RewindBlockIndex(const CChainParams& params)
 
     // nHeight is now the height of the first insufficiently-validated block, or tipheight + 1
     auto rewindLength = chainActive.Height() - nHeight;
-    if (rewindLength > 0 && rewindLength > MAX_REORG_LENGTH) {
+    clearWitnessCaches = false;
-        auto pindexOldTip = chainActive.Tip();
+
-        auto pindexRewind = chainActive[nHeight - 1];
+    if (rewindLength > 0) {
-        auto msg = strprintf(_(
+        LogPrintf("*** First insufficiently validated block at height %d, rewind length %d\n", nHeight, rewindLength);
-            "A block chain rewind has been detected that would roll back %d blocks! "
+        const uint256 *phashFirstInsufValidated = chainActive[nHeight]->phashBlock;
-            "This is larger than the maximum of %d blocks, and so the node is shutting down for your safety."
+        auto networkID = params.NetworkIDString();
-            ), rewindLength, MAX_REORG_LENGTH) + "\n\n" +
+
-            _("Rewind details") + ":\n" +
+        // This is true when we intend to do a long rewind.
-            "- " + strprintf(_("Current tip:   %s, height %d"),
+        bool intendedRewind =
-                pindexOldTip->phashBlock->GetHex(), pindexOldTip->nHeight) + "\n" +
+            (networkID == "test" && nHeight == 252500 && *phashFirstInsufValidated ==
-            "- " + strprintf(_("Rewinding to:  %s, height %d"),
+             uint256S("0018bd16a9c6f15795a754c498d2b2083ab78f14dae44a66a8d0e90ba8464d9c"));
-                pindexRewind->phashBlock->GetHex(), pindexRewind->nHeight) + "\n\n" +
+
-            _("Please help, human!");
+        clearWitnessCaches = (rewindLength > MAX_REORG_LENGTH && intendedRewind);
-        LogPrintf("*** %s\n", msg);
+
-        uiInterface.ThreadSafeMessageBox(msg, "", CClientUIInterface::MSG_ERROR);
+        if (clearWitnessCaches) {
-        StartShutdown();
+            auto msg = strprintf(_(
-        return false;
+                "An intended block chain rewind has been detected: network %s, hash %s, height %d"
+                ), networkID, phashFirstInsufValidated->GetHex(), nHeight);
+            LogPrintf("*** %s\n", msg);
+        }
+
+        if (rewindLength > MAX_REORG_LENGTH && !intendedRewind) {
+            auto pindexOldTip = chainActive.Tip();
+            auto pindexRewind = chainActive[nHeight - 1];
+            auto msg = strprintf(_(
+                "A block chain rewind has been detected that would roll back %d blocks! "
+                "This is larger than the maximum of %d blocks, and so the node is shutting down for your safety."
+                ), rewindLength, MAX_REORG_LENGTH) + "\n\n" +
+                _("Rewind details") + ":\n" +
+                "- " + strprintf(_("Current tip:   %s, height %d"),
+                    pindexOldTip->phashBlock->GetHex(), pindexOldTip->nHeight) + "\n" +
+                "- " + strprintf(_("Rewinding to:  %s, height %d"),
+                    pindexRewind->phashBlock->GetHex(), pindexRewind->nHeight) + "\n\n" +
+                _("Please help, human!");
+            LogPrintf("*** %s\n", msg);
+            uiInterface.ThreadSafeMessageBox(msg, "", CClientUIInterface::MSG_ERROR);
+            StartShutdown();
+            return false;
+        }
     }
 
     CValidationState state;

src/main.h

@@ -478,8 +478,11 @@ bool AcceptBlockHeader(const CBlockHeader& block, CValidationState& state, CBloc
  * When there are blocks in the active chain with missing data (e.g. if the
  * activation height and branch ID of a particular upgrade have been altered),
  * rewind the chainstate and remove them from the block index.
+ *
+ * clearWitnessCaches is an output parameter that will be set to true iff
+ * witness caches should be cleared in order to handle an intended long rewind.
  */
-bool RewindBlockIndex(const CChainParams& params);
+bool RewindBlockIndex(const CChainParams& params, bool& clearWitnessCaches);
 
 class CBlockFileInfo
 {