(testnet) Fall back to hardcoded shielded pool balance to avoid reorgs.

src/chainparams.cpp

@@ -353,6 +353,12 @@ public:
             715          //   total number of tx / (checkpoint block height / (24 * 24))
         };
 
+        // Hardcoded fallback value for the Sprout shielded value pool balance
+        // for nodes that have not reindexed since the introduction of monitoring
+        // in #2795.
+        nSproutValuePoolCheckpointHeight = 440329;
+        nSproutValuePoolCheckpointBalance = 40000029096803;
+
         // Founders reward script expects a vector of 2-of-3 multisig addresses
         vFoundersRewardAddress = {
             "t2UNzUUx8mWBCRYPRezvA363EYXyEpHokyi", "t2N9PH9Wk9xjqYg9iin1Ua3aekJqfAtE543", "t2NGQjYMQhFndDHguvUw4wZdNdsssA6K7x2", "t2ENg7hHVqqs9JwU5cgjvSbxnT2a9USNfhy",

src/chainparams.h

@@ -70,6 +70,9 @@ public:
     const std::vector<unsigned char>& AlertKey() const { return vAlertPubKey; }
     int GetDefaultPort() const { return nDefaultPort; }
 
+    CAmount SproutValuePoolCheckpointHeight() const { return nSproutValuePoolCheckpointHeight; }
+    CAmount SproutValuePoolCheckpointBalance() const { return nSproutValuePoolCheckpointBalance; }
+
     const CBlock& GenesisBlock() const { return genesis; }
     /** Make miner wait to have peers to avoid wasting work */
     bool MiningRequiresPeers() const { return fMiningRequiresPeers; }
@@ -125,6 +128,9 @@ protected:
     bool fTestnetToBeDeprecatedFieldRPC = false;
     CCheckpointData checkpointData;
     std::vector<std::string> vFoundersRewardAddress;
+
+    CAmount nSproutValuePoolCheckpointHeight = 0;
+    CAmount nSproutValuePoolCheckpointBalance = 0;
 };
 
 /**

src/main.cpp

@@ -3296,9 +3296,34 @@ CBlockIndex* AddToBlockIndex(const CBlockHeader& block)
     return pindexNew;
 }
 
+void FallbackSproutValuePoolBalance(
+    CBlockIndex *pindex,
+    const CChainParams& chainparams
+)
+{
+    // Check if the height of this block matches the checkpoint
+    if (pindex->nHeight == chainparams.SproutValuePoolCheckpointHeight()) {
+        // Are we monitoring the Sprout pool?
+        if (!pindex->nChainSproutValue) {
+            // Apparently not. Introduce the hardcoded value.
+            pindex->nChainSproutValue = chainparams.SproutValuePoolCheckpointBalance();
+        } else {
+            // Apparently we have been. So, we should expect the current
+            // value to match the hardcoded one.
+            assert(*pindex->nChainSproutValue == chainparams.SproutValuePoolCheckpointBalance());
+            // And we should expect non-none for the delta stored in the block index here,
+            // or the checkpoint is too early.
+            assert(pindex->nSproutValue != boost::none);
+        }
+    }
+}
+
 /** Mark a block as having its data received and checked (up to BLOCK_VALID_TRANSACTIONS). */
 bool ReceivedBlockTransactions(const CBlock &block, CValidationState& state, CBlockIndex *pindexNew, const CDiskBlockPos& pos)
 {
+    const CChainParams& chainparams = Params();
+    bool this_is_testnet = chainparams.NetworkIDString() == "test";
+
     pindexNew->nTx = block.vtx.size();
     pindexNew->nChainTx = 0;
     CAmount sproutValue = 0;
@@ -3351,6 +3376,13 @@ bool ReceivedBlockTransactions(const CBlock &block, CValidationState& state, CBl
                 pindex->nChainSproutValue = pindex->nSproutValue;
                 pindex->nChainSaplingValue = pindex->nSaplingValue;
             }
+
+            // Fall back to hardcoded Sprout value pool balance if we're on
+            // testnet.
+            if (this_is_testnet) {
+                FallbackSproutValuePoolBalance(pindex, chainparams);
+            }
+
             {
                 LOCK(cs_nBlockSequenceId);
                 pindex->nSequenceId = nBlockSequenceId++;
@@ -4003,6 +4035,8 @@ CBlockIndex * InsertBlockIndex(uint256 hash)
 bool static LoadBlockIndexDB()
 {
     const CChainParams& chainparams = Params();
+    bool this_is_testnet = chainparams.NetworkIDString() == "test";
+
     if (!pblocktree->LoadBlockIndexGuts())
         return false;
 
@@ -4032,6 +4066,7 @@ bool static LoadBlockIndexDB()
                     } else {
                         pindex->nChainSproutValue = boost::none;
                     }
+
                     if (pindex->pprev->nChainSaplingValue) {
                         pindex->nChainSaplingValue = *pindex->pprev->nChainSaplingValue + pindex->nSaplingValue;
                     } else {
@@ -4048,6 +4083,12 @@ bool static LoadBlockIndexDB()
                 pindex->nChainSproutValue = pindex->nSproutValue;
                 pindex->nChainSaplingValue = pindex->nSaplingValue;
             }
+
+            // Fall back to hardcoded Sprout value pool balance if we're on
+            // testnet.
+            if (this_is_testnet) {
+                FallbackSproutValuePoolBalance(pindex, chainparams);
+            }
         }
         // Construct in-memory chain of branch IDs.
         // Relies on invariant: a block that does not activate a network upgrade