Merge bitcoin/bitcoin#31897: mining: drop unused -nFees and sigops from CBlockTemplate

226d81f mining: drop unused -nFees and sigops from CBlockTemplate (Sjors Provoost)
53ad845 test: check fees and sigops in getblocktemplate (Sjors Provoost)

Pull request description:

  For the coinbase `vTxFees` used a dummy value of -nFees.

  Similarly the first `vTxSigOpsCost` entry was calculated from
  the dummy coinbase transaction.

  This was introduced in #2115, but the values were never returned by the RPC or used in a test.

  Drop 'm and add code comments to prevent confusion.

  This PR also adds test coverage for the `fees` and `sigops` fields in `getblocktemplate`, so it closes #32053.

ACKs for top commit:
  ismaelsadeeq:
    re-ACK 226d81f
  ryanofsky:
    Code review ACK 226d81f. New test was added since last review, which seems very cleanly written and fixes some missing coverage.
  glozow:
    ACK 226d81f

Tree-SHA512: 79c534e6bc4810d29114b04dd6db798877732cb473e773bf3cc28f83d14ee3982392587bd0baa39857bd53a79eae3b730d7a7029b08a9b6c3b5c51f86657ca5d

Author: glozow

src/interfaces/mining.h

@@ -34,9 +34,12 @@ class BlockTemplate
     virtual ~BlockTemplate() = default;
 
     virtual CBlockHeader getBlockHeader() = 0;
+    // Block contains a dummy coinbase transaction that should not be used.
     virtual CBlock getBlock() = 0;
 
+    // Fees per transaction, not including coinbase transaction.
     virtual std::vector<CAmount> getTxFees() = 0;
+    // Sigop cost per transaction, not including coinbase transaction.
     virtual std::vector<int64_t> getTxSigops() = 0;
 
     virtual CTransactionRef getCoinbaseTx() = 0;

src/node/miner.cpp

@@ -124,10 +124,9 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock()
     pblocktemplate.reset(new CBlockTemplate());
     CBlock* const pblock = &pblocktemplate->block; // pointer for convenience
 
-    // Add dummy coinbase tx as first transaction
+    // Add dummy coinbase tx as first transaction. It is skipped by the
+    // getblocktemplate RPC and mining interface consumers must not use it.
     pblock->vtx.emplace_back();
-    pblocktemplate->vTxFees.push_back(-1); // updated at end
-    pblocktemplate->vTxSigOpsCost.push_back(-1); // updated at end
 
     LOCK(::cs_main);
     CBlockIndex* pindexPrev = m_chainstate.m_chain.Tip();
@@ -165,7 +164,6 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock()
     coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
     pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
     pblocktemplate->vchCoinbaseCommitment = m_chainstate.m_chainman.GenerateCoinbaseCommitment(*pblock, pindexPrev);
-    pblocktemplate->vTxFees[0] = -nFees;
 
     LogPrintf("CreateNewBlock(): block weight: %u txs: %u fees: %ld sigops %d\n", GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);
 
@@ -174,7 +172,6 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock()
     UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
     pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
     pblock->nNonce         = 0;
-    pblocktemplate->vTxSigOpsCost[0] = WITNESS_SCALE_FACTOR * GetLegacySigOpCount(*pblock->vtx[0]);
 
     BlockValidationState state;
     if (m_options.test_block_validity && !TestBlockValidity(state, chainparams, m_chainstate, *pblock, pindexPrev,

src/node/miner.h

@@ -37,7 +37,9 @@ static const bool DEFAULT_PRINT_MODIFIED_FEE = false;
 struct CBlockTemplate
 {
     CBlock block;
+    // Fees per transaction, not including coinbase transaction (unlike CBlock::vtx).
     std::vector<CAmount> vTxFees;
+    // Sigops per transaction, not including coinbase transaction (unlike CBlock::vtx).
     std::vector<int64_t> vTxSigOpsCost;
     std::vector<unsigned char> vchCoinbaseCommitment;
     /* A vector of package fee rates, ordered by the sequence in which

src/rpc/mining.cpp

@@ -893,7 +893,7 @@ static RPCHelpMan getblocktemplate()
         }
         entry.pushKV("depends", std::move(deps));
 
-        int index_in_template = i - 1;
+        int index_in_template = i - 2;
         entry.pushKV("fee", tx_fees.at(index_in_template));
         int64_t nTxSigOps{tx_sigops.at(index_in_template)};
         if (fPreSegWit) {

test/functional/mining_basic.py

@@ -40,7 +40,10 @@
     assert_raises_rpc_error,
     get_fee,
 )
-from test_framework.wallet import MiniWallet
+from test_framework.wallet import (
+    MiniWallet,
+    MiniWalletMode,
+)
 
 
 DIFFICULTY_ADJUSTMENT_INTERVAL = 144
@@ -93,6 +96,57 @@ def mine_chain(self):
         self.restart_node(0)
         self.connect_nodes(0, 1)
 
+    def test_fees_and_sigops(self):
+        self.log.info("Test fees and sigops in getblocktemplate result")
+        node = self.nodes[0]
+
+        # Generate a coinbases with p2pk transactions for its sigops.
+        wallet_sigops = MiniWallet(node, mode=MiniWalletMode.RAW_P2PK)
+        self.generate(wallet_sigops, 1, sync_fun=self.no_op)
+
+        # Mature with regular coinbases to prevent inteference with other tests
+        self.generate(self.wallet, 100, sync_fun=self.no_op)
+
+        # Generate three transactions that must be mined in sequence
+        #
+        #      tx_a (1 sat/vbyte)
+        #        |
+        #        |
+        #      tx_b (2 sat/vbyte)
+        #        |
+        #        |
+        #      tx_c (3 sat/vbyte)
+        #
+        tx_a = wallet_sigops.send_self_transfer(from_node=node,
+                                                fee_rate=Decimal("0.00001"))
+        tx_b = wallet_sigops.send_self_transfer(from_node=node,
+                                                fee_rate=Decimal("0.00002"),
+                                                utxo_to_spend=tx_a["new_utxo"])
+        tx_c = wallet_sigops.send_self_transfer(from_node=node,
+                                                fee_rate=Decimal("0.00003"),
+                                                utxo_to_spend=tx_b["new_utxo"])
+
+        # Generate transaction without sigops. It will go first because it pays
+        # higher fees (100 sat/vbyte) and descends from a different coinbase.
+        tx_d = self.wallet.send_self_transfer(from_node=node,
+                                              fee_rate=Decimal("0.00100"))
+
+        block_template_txs = node.getblocktemplate(NORMAL_GBT_REQUEST_PARAMS)['transactions']
+
+        block_template_fees = [tx['fee'] for tx in block_template_txs]
+        assert_equal(block_template_fees, [
+            tx_d["fee"] * COIN,
+            tx_a["fee"] * COIN,
+            tx_b["fee"] * COIN,
+            tx_c["fee"] * COIN
+        ])
+
+        block_template_sigops = [tx['sigops'] for tx in block_template_txs]
+        assert_equal(block_template_sigops, [0, 4, 4, 4])
+
+        # Clear mempool
+        self.generate(self.wallet, 1, sync_fun=self.no_op)
+
     def test_blockmintxfee_parameter(self):
         self.log.info("Test -blockmintxfee setting")
         self.restart_node(0, extra_args=['-minrelaytxfee=0', '-persistmempool=0'])
@@ -533,6 +587,7 @@ def chain_tip(b_hash, *, status='headers-only', branchlen=1):
         node.submitheader(hexdata=CBlockHeader(bad_block_root).serialize().hex())
         assert_equal(node.submitblock(hexdata=block.serialize().hex()), 'duplicate')  # valid
 
+        self.test_fees_and_sigops()
         self.test_blockmintxfee_parameter()
         self.test_block_max_weight()
         self.test_timewarp()