mining: add -coinbaselocktime

On by default.

Allow Stratum v2 miners to opt out, pending more discussion on the BIP.

Author: Sjors

src/init.cpp

@@ -663,6 +663,7 @@ void SetupServerArgs(ArgsManager& argsman, bool can_listen_ipc)
     argsman.AddArg("-blockreservedweight=<n>", strprintf("Reserve space for the fixed-size block header plus the largest coinbase transaction the mining software may add to the block. (default: %d).", DEFAULT_BLOCK_RESERVED_WEIGHT), ArgsManager::ALLOW_ANY, OptionsCategory::BLOCK_CREATION);
     argsman.AddArg("-blockmintxfee=<amt>", strprintf("Set lowest fee rate (in %s/kvB) for transactions to be included in block creation. (default: %s)", CURRENCY_UNIT, FormatMoney(DEFAULT_BLOCK_MIN_TX_FEE)), ArgsManager::ALLOW_ANY, OptionsCategory::BLOCK_CREATION);
     argsman.AddArg("-blockversion=<n>", "Override block version to test forking scenarios", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::BLOCK_CREATION);
+    argsman.AddArg("-coinbaselocktime", strprintf("Set nLockTime to the current block height and nSequence to enforce it (default: %d)", DEFAULT_COINBASE_LOCKTIME), ArgsManager::ALLOW_ANY, OptionsCategory::BLOCK_CREATION);
 
     argsman.AddArg("-rest", strprintf("Accept public REST requests (default: %u)", DEFAULT_REST_ENABLE), ArgsManager::ALLOW_ANY, OptionsCategory::RPC);
     argsman.AddArg("-rpcallowip=<ip>", "Allow JSON-RPC connections from specified source. Valid values for <ip> are a single IP (e.g. 1.2.3.4), a network/netmask (e.g. 1.2.3.4/255.255.255.0), a network/CIDR (e.g. 1.2.3.4/24), all ipv4 (0.0.0.0/0), or all ipv6 (::/0). RFC4193 is allowed only if -cjdnsreachable=0. This option can be specified multiple times", ArgsManager::ALLOW_ANY, OptionsCategory::RPC);

src/node/miner.cpp

@@ -103,6 +103,7 @@ void ApplyArgsManOptions(const ArgsManager& args, BlockAssembler::Options& optio
     }
     options.print_modified_fee = args.GetBoolArg("-printpriority", options.print_modified_fee);
     options.block_reserved_weight = args.GetIntArg("-blockreservedweight", options.block_reserved_weight);
+    options.coinbase_locktime = args.GetBoolArg("-coinbaselocktime", DEFAULT_COINBASE_LOCKTIME);
 }
 
 void BlockAssembler::resetBlock()
@@ -161,13 +162,17 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock()
     CMutableTransaction coinbaseTx;
     coinbaseTx.vin.resize(1);
     coinbaseTx.vin[0].prevout.SetNull();
-    coinbaseTx.vin[0].nSequence = CTxIn::MAX_SEQUENCE_NONFINAL; // Make sure timelock is enforced.
+    if (m_options.coinbase_locktime) {
+        coinbaseTx.vin[0].nSequence = CTxIn::MAX_SEQUENCE_NONFINAL; // Make sure timelock is enforced.
+    }
     coinbaseTx.vout.resize(1);
     coinbaseTx.vout[0].scriptPubKey = m_options.coinbase_output_script;
     coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());
     coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
     Assert(nHeight > 0);
-    coinbaseTx.nLockTime = static_cast<uint32_t>(nHeight - 1);
+    if (m_options.coinbase_locktime) {
+        coinbaseTx.nLockTime = static_cast<uint32_t>(nHeight - 1);
+    }
     pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
     pblocktemplate->vchCoinbaseCommitment = m_chainstate.m_chainman.GenerateCoinbaseCommitment(*pblock, pindexPrev);
 

src/node/miner.h

@@ -173,6 +173,8 @@ class BlockAssembler
         // Configuration parameters for the block size
         size_t nBlockMaxWeight{DEFAULT_BLOCK_MAX_WEIGHT};
         CFeeRate blockMinFeeRate{DEFAULT_BLOCK_MIN_TX_FEE};
+        // Whether to set nLockTime to the current height
+        bool coinbase_locktime{DEFAULT_COINBASE_LOCKTIME};
         // Whether to call TestBlockValidity() at the end of CreateNewBlock().
         bool test_block_validity{true};
         bool print_modified_fee{DEFAULT_PRINT_MODIFIED_FEE};

src/policy/policy.h

@@ -30,6 +30,8 @@ static constexpr unsigned int DEFAULT_BLOCK_RESERVED_WEIGHT{8000};
 static constexpr unsigned int MINIMUM_BLOCK_RESERVED_WEIGHT{2000};
 /** Default for -blockmintxfee, which sets the minimum feerate for a transaction in blocks created by mining code **/
 static constexpr unsigned int DEFAULT_BLOCK_MIN_TX_FEE{1000};
+/** Default for -coinbaselocktime, which sets the coinbase nLockTime (and nSequence) in blocks created by mining code **/
+static constexpr bool DEFAULT_COINBASE_LOCKTIME{true};
 /** The maximum weight for transactions we're willing to relay/mine */
 static constexpr int32_t MAX_STANDARD_TX_WEIGHT{400000};
 /** The minimum non-witness size for transactions we're willing to relay/mine: one larger than 64  */