Merge bitcoin/bitcoin#24732: Remove buggy and confusing IncrementExtraNonce

cccc4e879a8cb9d858a88ea46b28ea27ab79ca55 Remove nHeightEnd and nHeight in generateBlocks helper (MarcoFalke)
fa38b1c8bd29e2c792737f6481ab928e46396b7e Remove buggy and confusing IncrementExtraNonce (MarcoFalke)

Pull request description:

  IncrementExtraNonce has many issues:

  * It is test-only code, but part of bitcoind
  * It is using the block height of the tip, as opposed to the block's previous block as reference for the new height. See https://github.com/bitcoin/bitcoin/issues/24730#issuecomment-1085586193
  * It has no use case in regtest testing. With a low difficulty the extra nonce won't be incremented. With a high difficulty the test-only functions are clumsy to handle anyway. For example, the generate* RPCs will return an empty array once they reached `maxtries`, as opposed to an error. Also the calls can't be aborted early unless the node shuts down completely. So I think it is fine to just remove the extra nonce functionality and leave it to the outside to implement, if needed. For example, a wrapper script can call the `generate*` RPCs once every second, to use the timestamp as extra nonce.

ACKs for top commit:
  ajtowns:
    ACK cccc4e879a8cb9d858a88ea46b28ea27ab79ca55

Tree-SHA512: d8a3989ad280ebd4b1b574159b3a396b8a42134347e6be3c88445162d86624d221c416456f45ae75aea62ed8c8a1a9bb3a2532924abca2ef7a879cb8e6b15654

4 files changed, 14 insertions, 46 deletions

diff --git a/src/node/miner.cpp b/src/node/miner.cpp
index 917df91933..be5d58527b 100644
--- a/src/node/miner.cpp
+++ b/src/node/miner.cpp
@@ -430,22 +430,4 @@ void BlockAssembler::addPackageTxs(int& nPackagesSelected, int& nDescendantsUpda
         nDescendantsUpdated += UpdatePackagesForAdded(ancestors, mapModifiedTx);
     }
 }
-
-void IncrementExtraNonce(CBlock* pblock, const CBlockIndex* pindexPrev, unsigned int& nExtraNonce)
-{
-    // Update nExtraNonce
-    static uint256 hashPrevBlock;
-    if (hashPrevBlock != pblock->hashPrevBlock) {
-        nExtraNonce = 0;
-        hashPrevBlock = pblock->hashPrevBlock;
-    }
-    ++nExtraNonce;
-    unsigned int nHeight = pindexPrev->nHeight + 1; // Height first in coinbase required for block.version=2
-    CMutableTransaction txCoinbase(*pblock->vtx[0]);
-    txCoinbase.vin[0].scriptSig = (CScript() << nHeight << CScriptNum(nExtraNonce));
-    assert(txCoinbase.vin[0].scriptSig.size() <= 100);
-
-    pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
-    pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
-}
 } // namespace node
diff --git a/src/node/miner.h b/src/node/miner.h
index 5fd9abc280..c8093ec883 100644
--- a/src/node/miner.h
+++ b/src/node/miner.h
@@ -200,8 +200,6 @@ private:
     int UpdatePackagesForAdded(const CTxMemPool::setEntries& alreadyAdded, indexed_modified_transaction_set& mapModifiedTx) EXCLUSIVE_LOCKS_REQUIRED(m_mempool.cs);
 };
 
-/** Modify the extranonce in a block */
-void IncrementExtraNonce(CBlock* pblock, const CBlockIndex* pindexPrev, unsigned int& nExtraNonce);
 int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev);
 
 /** Update an old GenerateCoinbaseCommitment from CreateNewBlock after the block txs have changed */
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index 1d1ae92c58..211026c8d9 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -7,6 +7,7 @@
 #include <chainparams.h>
 #include <consensus/amount.h>
 #include <consensus/consensus.h>
+#include <consensus/merkle.h>
 #include <consensus/params.h>
 #include <consensus/validation.h>
 #include <core_io.h>
@@ -43,7 +44,6 @@
 
 using node::BlockAssembler;
 using node::CBlockTemplate;
-using node::IncrementExtraNonce;
 using node::NodeContext;
 using node::RegenerateCommitments;
 using node::UpdateTime;
@@ -116,14 +116,10 @@ static RPCHelpMan getnetworkhashps()
     };
 }
 
-static bool GenerateBlock(ChainstateManager& chainman, CBlock& block, uint64_t& max_tries, unsigned int& extra_nonce, uint256& block_hash)
+static bool GenerateBlock(ChainstateManager& chainman, CBlock& block, uint64_t& max_tries, uint256& block_hash)
 {
     block_hash.SetNull();
-
-    {
-        LOCK(cs_main);
-        IncrementExtraNonce(&block, chainman.ActiveChain().Tip(), extra_nonce);
-    }
+    block.hashMerkleRoot = BlockMerkleRoot(block);
 
     CChainParams chainparams(Params());
 
@@ -149,30 +145,20 @@ static bool GenerateBlock(ChainstateManager& chainman, CBlock& block, uint64_t&
 
 static UniValue generateBlocks(ChainstateManager& chainman, const CTxMemPool& mempool, const CScript& coinbase_script, int nGenerate, uint64_t nMaxTries)
 {
-    int nHeightEnd = 0;
-    int nHeight = 0;
-
-    {   // Don't keep cs_main locked
-        LOCK(cs_main);
-        nHeight = chainman.ActiveChain().Height();
-        nHeightEnd = nHeight+nGenerate;
-    }
-    unsigned int nExtraNonce = 0;
     UniValue blockHashes(UniValue::VARR);
-    while (nHeight < nHeightEnd && !ShutdownRequested())
-    {
+    while (nGenerate > 0 && !ShutdownRequested()) {
         std::unique_ptr<CBlockTemplate> pblocktemplate(BlockAssembler(chainman.ActiveChainstate(), mempool, Params()).CreateNewBlock(coinbase_script));
         if (!pblocktemplate.get())
             throw JSONRPCError(RPC_INTERNAL_ERROR, "Couldn't create new block");
         CBlock *pblock = &pblocktemplate->block;
 
         uint256 block_hash;
-        if (!GenerateBlock(chainman, *pblock, nMaxTries, nExtraNonce, block_hash)) {
+        if (!GenerateBlock(chainman, *pblock, nMaxTries, block_hash)) {
             break;
         }
 
         if (!block_hash.IsNull()) {
-            ++nHeight;
+            --nGenerate;
             blockHashes.push_back(block_hash.GetHex());
         }
     }
@@ -397,9 +383,8 @@ static RPCHelpMan generateblock()
 
     uint256 block_hash;
     uint64_t max_tries{DEFAULT_MAX_TRIES};
-    unsigned int extra_nonce{0};
 
-    if (!GenerateBlock(chainman, block, max_tries, extra_nonce, block_hash) || block_hash.IsNull()) {
+    if (!GenerateBlock(chainman, block, max_tries, block_hash) || block_hash.IsNull()) {
         throw JSONRPCError(RPC_MISC_ERROR, "Failed to make block.");
     }
 
diff --git a/src/test/blockfilter_index_tests.cpp b/src/test/blockfilter_index_tests.cpp
index 7c502349b3..82b9617384 100644
--- a/src/test/blockfilter_index_tests.cpp
+++ b/src/test/blockfilter_index_tests.cpp
@@ -4,6 +4,7 @@
 
 #include <blockfilter.h>
 #include <chainparams.h>
+#include <consensus/merkle.h>
 #include <consensus/validation.h>
 #include <index/blockfilterindex.h>
 #include <node/miner.h>
@@ -18,7 +19,6 @@
 
 using node::BlockAssembler;
 using node::CBlockTemplate;
-using node::IncrementExtraNonce;
 
 BOOST_AUTO_TEST_SUITE(blockfilter_index_tests)
 
@@ -76,9 +76,12 @@ CBlock BuildChainTestingSetup::CreateBlock(const CBlockIndex* prev,
     for (const CMutableTransaction& tx : txns) {
         block.vtx.push_back(MakeTransactionRef(tx));
     }
-    // IncrementExtraNonce creates a valid coinbase and merkleRoot
-    unsigned int extraNonce = 0;
-    IncrementExtraNonce(&block, prev, extraNonce);
+    {
+        CMutableTransaction tx_coinbase{*block.vtx.at(0)};
+        tx_coinbase.vin.at(0).scriptSig = CScript{} << prev->nHeight + 1;
+        block.vtx.at(0) = MakeTransactionRef(std::move(tx_coinbase));
+        block.hashMerkleRoot = BlockMerkleRoot(block);
+    }
 
     while (!CheckProofOfWork(block.GetHash(), block.nBits, chainparams.GetConsensus())) ++block.nNonce;