Merge #14811: Mining: Enforce that segwit option must be set in GBT

d2ce315fbf [docs] add release note for change to GBT (John Newbery)
0025c9eae4 [mining] segwit option must be set in GBT (John Newbery)

Pull request description:

  Calling getblocktemplate without the segwit rule specified is most
  likely a client error, since it results in lower fees for the miner.
  Prevent this client error by failing getblocktemplate if called without
  the segwit rule specified.

  Of the previous 1000 blocks (measured at block [551591 (hash 0x...173c811)](https://blockstream.info/block/000000000000000000173c811e79858808abc3216af607035973f002bef60a7a)), 991 included segwit transactions.

Tree-SHA512: 7933b073d72683c9ab9318db46a085ec19a56a14937945c73f783ac7656887619a86b74db0bdfcb8121df44f63a1d6a6fb19e98505b2a26a6a8a6e768e442fee

11 files changed, 39 insertions, 62 deletions

diff --git a/doc/release-notes.md b/doc/release-notes.md
index f5c139e3f..946525831 100644
--- a/doc/release-notes.md
+++ b/doc/release-notes.md
@@ -65,6 +65,13 @@ platform.
 Notable changes
 ===============
 
+Mining
+------
+
+- Calls to `getblocktemplate` will fail if the segwit rule is not specified.
+  Calling `getblocktemplate` without segwit specified is almost certainly
+  a misconfiguration since doing so results in lower rewards for the miner.
+
 Command line option changes
 ---------------------------
 
@@ -182,6 +189,8 @@ in the Low-level Changes section below.
   P2SH-P2WPKH, and P2SH-P2WSH. Requests for P2WSH and P2SH-P2WSH accept
   an additional `witnessscript` parameter.
 
+- See the [Mining](#mining) section for changes to `getblocktemplate`.
+
 Low-level changes
 =================
 
diff --git a/src/bench/block_assemble.cpp b/src/bench/block_assemble.cpp
index 2def0b23e..7cf27f9f5 100644
--- a/src/bench/block_assemble.cpp
+++ b/src/bench/block_assemble.cpp
@@ -27,7 +27,7 @@ static std::shared_ptr<CBlock> PrepareBlock(const CScript& coinbase_scriptPubKey
 {
     auto block = std::make_shared<CBlock>(
         BlockAssembler{Params()}
-            .CreateNewBlock(coinbase_scriptPubKey, /* fMineWitnessTx */ true)
+            .CreateNewBlock(coinbase_scriptPubKey)
             ->block);
 
     block->nTime = ::chainActive.Tip()->GetMedianTimePast() + 1;
diff --git a/src/miner.cpp b/src/miner.cpp
index 96c9cd6d2..ef48a86e3 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -95,7 +95,7 @@ void BlockAssembler::resetBlock()
     nFees = 0;
 }
 
-std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn, bool fMineWitnessTx)
+std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn)
 {
     int64_t nTimeStart = GetTimeMicros();
 
@@ -139,7 +139,7 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& sc
     // not activated.
     // TODO: replace this with a call to main to assess validity of a mempool
     // transaction (which in most cases can be a no-op).
-    fIncludeWitness = IsWitnessEnabled(pindexPrev, chainparams.GetConsensus()) && fMineWitnessTx;
+    fIncludeWitness = IsWitnessEnabled(pindexPrev, chainparams.GetConsensus());
 
     int nPackagesSelected = 0;
     int nDescendantsUpdated = 0;
diff --git a/src/miner.h b/src/miner.h
index 8cdcf7133..44c50b01a 100644
--- a/src/miner.h
+++ b/src/miner.h
@@ -157,7 +157,7 @@ public:
     BlockAssembler(const CChainParams& params, const Options& options);
 
     /** Construct a new block template with coinbase to scriptPubKeyIn */
-    std::unique_ptr<CBlockTemplate> CreateNewBlock(const CScript& scriptPubKeyIn, bool fMineWitnessTx=true);
+    std::unique_ptr<CBlockTemplate> CreateNewBlock(const CScript& scriptPubKeyIn);
 
 private:
     // utility functions
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index 29684d0e6..2fd6f99be 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -311,7 +311,7 @@ static UniValue getblocktemplate(const JSONRPCRequest& request)
                 "    https://github.com/bitcoin/bips/blob/master/bip-0009.mediawiki#getblocktemplate_changes\n"
                 "    https://github.com/bitcoin/bips/blob/master/bip-0145.mediawiki\n",
                 {
-                    {"template_request", RPCArg::Type::OBJ, /* opt */ true, /* default_val */ "", "A json object in the following spec",
+                    {"template_request", RPCArg::Type::OBJ, /* opt */ false, /* default_val */ "", "A json object in the following spec",
                         {
                             {"mode", RPCArg::Type::STR, /* opt */ true, /* default_val */ "", "This must be set to \"template\", \"proposal\" (see BIP 23), or omitted"},
                             {"capabilities", RPCArg::Type::ARR, /* opt */ true, /* default_val */ "", "A list of strings",
@@ -319,7 +319,7 @@ static UniValue getblocktemplate(const JSONRPCRequest& request)
                                     {"support", RPCArg::Type::STR, /* opt */ true, /* default_val */ "", "client side supported feature, 'longpoll', 'coinbasetxn', 'coinbasevalue', 'proposal', 'serverlist', 'workid'"},
                                 },
                                 },
-                            {"rules", RPCArg::Type::ARR, /* opt */ true, /* default_val */ "", "A list of strings",
+                            {"rules", RPCArg::Type::ARR, /* opt */ false, /* default_val */ "", "A list of strings",
                                 {
                                     {"support", RPCArg::Type::STR, /* opt */ true, /* default_val */ "", "client side supported softfork deployment"},
                                 },
@@ -503,21 +503,17 @@ static UniValue getblocktemplate(const JSONRPCRequest& request)
     }
 
     const struct VBDeploymentInfo& segwit_info = VersionBitsDeploymentInfo[Consensus::DEPLOYMENT_SEGWIT];
-    // If the caller is indicating segwit support, then allow CreateNewBlock()
-    // to select witness transactions, after segwit activates (otherwise
-    // don't).
-    bool fSupportsSegwit = setClientRules.find(segwit_info.name) != setClientRules.end();
+    // GBT must be called with 'segwit' set in the rules
+    if (setClientRules.count(segwit_info.name) != 1) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, "getblocktemplate must be called with the segwit rule set (call with {\"rules\": [\"segwit\"]})");
+    }
 
     // Update block
     static CBlockIndex* pindexPrev;
     static int64_t nStart;
     static std::unique_ptr<CBlockTemplate> pblocktemplate;
-    // Cache whether the last invocation was with segwit support, to avoid returning
-    // a segwit-block to a non-segwit caller.
-    static bool fLastTemplateSupportsSegwit = true;
     if (pindexPrev != chainActive.Tip() ||
-        (mempool.GetTransactionsUpdated() != nTransactionsUpdatedLast && GetTime() - nStart > 5) ||
-        fLastTemplateSupportsSegwit != fSupportsSegwit)
+        (mempool.GetTransactionsUpdated() != nTransactionsUpdatedLast && GetTime() - nStart > 5))
     {
         // Clear pindexPrev so future calls make a new block, despite any failures from here on
         pindexPrev = nullptr;
@@ -526,11 +522,10 @@ static UniValue getblocktemplate(const JSONRPCRequest& request)
         nTransactionsUpdatedLast = mempool.GetTransactionsUpdated();
         CBlockIndex* pindexPrevNew = chainActive.Tip();
         nStart = GetTime();
-        fLastTemplateSupportsSegwit = fSupportsSegwit;
 
         // Create new block
         CScript scriptDummy = CScript() << OP_TRUE;
-        pblocktemplate = BlockAssembler(Params()).CreateNewBlock(scriptDummy, fSupportsSegwit);
+        pblocktemplate = BlockAssembler(Params()).CreateNewBlock(scriptDummy);
         if (!pblocktemplate)
             throw JSONRPCError(RPC_OUT_OF_MEMORY, "Out of memory");
 
@@ -682,7 +677,7 @@ static UniValue getblocktemplate(const JSONRPCRequest& request)
     result.pushKV("bits", strprintf("%08x", pblock->nBits));
     result.pushKV("height", (int64_t)(pindexPrev->nHeight+1));
 
-    if (!pblocktemplate->vchCoinbaseCommitment.empty() && fSupportsSegwit) {
+    if (!pblocktemplate->vchCoinbaseCommitment.empty()) {
         result.pushKV("default_witness_commitment", HexStr(pblocktemplate->vchCoinbaseCommitment.begin(), pblocktemplate->vchCoinbaseCommitment.end()));
     }
 
diff --git a/src/test/validation_block_tests.cpp b/src/test/validation_block_tests.cpp
index 62dfed6c4..44432cd0a 100644
--- a/src/test/validation_block_tests.cpp
+++ b/src/test/validation_block_tests.cpp
@@ -54,7 +54,7 @@ std::shared_ptr<CBlock> Block(const uint256& prev_hash)
     CScript pubKey;
     pubKey << i++ << OP_TRUE;
 
-    auto ptemplate = BlockAssembler(Params()).CreateNewBlock(pubKey, false);
+    auto ptemplate = BlockAssembler(Params()).CreateNewBlock(pubKey);
     auto pblock = std::make_shared<CBlock>(ptemplate->block);
     pblock->hashPrevBlock = prev_hash;
     pblock->nTime = ++time;
diff --git a/test/functional/feature_segwit.py b/test/functional/feature_segwit.py
index 7098a03f1..4bcdf9af5 100755
--- a/test/functional/feature_segwit.py
+++ b/test/functional/feature_segwit.py
@@ -90,7 +90,7 @@ class SegWitTest(BitcoinTestFramework):
 
         self.log.info("Verify sigops are counted in GBT with pre-BIP141 rules before the fork")
         txid = self.nodes[0].sendtoaddress(self.nodes[0].getnewaddress(), 1)
-        tmpl = self.nodes[0].getblocktemplate({})
+        tmpl = self.nodes[0].getblocktemplate({'rules': ['segwit']})
         assert(tmpl['sizelimit'] == 1000000)
         assert('weightlimit' not in tmpl)
         assert(tmpl['sigoplimit'] == 20000)
@@ -232,15 +232,7 @@ class SegWitTest(BitcoinTestFramework):
         assert(tx.wit.is_null())
         assert(txid3 in self.nodes[0].getrawmempool())
 
-        # Now try calling getblocktemplate() without segwit support.
-        template = self.nodes[0].getblocktemplate()
-
-        # Check that tx1 is the only transaction of the 3 in the template.
-        template_txids = [t['txid'] for t in template['transactions']]
-        assert(txid2 not in template_txids and txid3 not in template_txids)
-        assert(txid1 in template_txids)
-
-        # Check that running with segwit support results in all 3 being included.
+        # Check that getblocktemplate includes all transactions.
         template = self.nodes[0].getblocktemplate({"rules": ["segwit"]})
         template_txids = [t['txid'] for t in template['transactions']]
         assert(txid1 in template_txids)
diff --git a/test/functional/mining_basic.py b/test/functional/mining_basic.py
index 6e7473134..661d9f4c9 100755
--- a/test/functional/mining_basic.py
+++ b/test/functional/mining_basic.py
@@ -30,7 +30,7 @@ from test_framework.script import CScriptNum
 def assert_template(node, block, expect, rehash=True):
     if rehash:
         block.hashMerkleRoot = block.calc_merkle_root()
-    rsp = node.getblocktemplate(template_request={'data': b2x(block.serialize()), 'mode': 'proposal'})
+    rsp = node.getblocktemplate(template_request={'data': b2x(block.serialize()), 'mode': 'proposal', 'rules': ['segwit']})
     assert_equal(rsp, expect)
 
 
@@ -60,7 +60,7 @@ class MiningTest(BitcoinTestFramework):
 
         # Mine a block to leave initial block download
         node.generatetoaddress(1, node.get_deterministic_priv_key().address)
-        tmpl = node.getblocktemplate()
+        tmpl = node.getblocktemplate({'rules': ['segwit']})
         self.log.info("getblocktemplate: Test capability advertised")
         assert 'proposal' in tmpl['capabilities']
         assert 'coinbasetxn' not in tmpl
@@ -86,6 +86,9 @@ class MiningTest(BitcoinTestFramework):
         block.nNonce = 0
         block.vtx = [coinbase_tx]
 
+        self.log.info("getblocktemplate: segwit rule must be set")
+        assert_raises_rpc_error(-8, "getblocktemplate must be called with the segwit rule set", node.getblocktemplate)
+
         self.log.info("getblocktemplate: Test valid block")
         assert_template(node, block, None)
 
@@ -102,7 +105,7 @@ class MiningTest(BitcoinTestFramework):
         assert_raises_rpc_error(-22, "Block does not start with a coinbase", node.submitblock, b2x(bad_block.serialize()))
 
         self.log.info("getblocktemplate: Test truncated final transaction")
-        assert_raises_rpc_error(-22, "Block decode failed", node.getblocktemplate, {'data': b2x(block.serialize()[:-1]), 'mode': 'proposal'})
+        assert_raises_rpc_error(-22, "Block decode failed", node.getblocktemplate, {'data': b2x(block.serialize()[:-1]), 'mode': 'proposal', 'rules': ['segwit']})
 
         self.log.info("getblocktemplate: Test duplicate transaction")
         bad_block = copy.deepcopy(block)
@@ -132,7 +135,7 @@ class MiningTest(BitcoinTestFramework):
         bad_block_sn = bytearray(block.serialize())
         assert_equal(bad_block_sn[TX_COUNT_OFFSET], 1)
         bad_block_sn[TX_COUNT_OFFSET] += 1
-        assert_raises_rpc_error(-22, "Block decode failed", node.getblocktemplate, {'data': b2x(bad_block_sn), 'mode': 'proposal'})
+        assert_raises_rpc_error(-22, "Block decode failed", node.getblocktemplate, {'data': b2x(bad_block_sn), 'mode': 'proposal', 'rules': ['segwit']})
 
         self.log.info("getblocktemplate: Test bad bits")
         bad_block = copy.deepcopy(block)
diff --git a/test/functional/mining_getblocktemplate_longpoll.py b/test/functional/mining_getblocktemplate_longpoll.py
index 9a3c15a4a..72cde8e81 100755
--- a/test/functional/mining_getblocktemplate_longpoll.py
+++ b/test/functional/mining_getblocktemplate_longpoll.py
@@ -15,14 +15,14 @@ class LongpollThread(threading.Thread):
     def __init__(self, node):
         threading.Thread.__init__(self)
         # query current longpollid
-        template = node.getblocktemplate()
+        template = node.getblocktemplate({'rules': ['segwit']})
         self.longpollid = template['longpollid']
         # create a new connection to the node, we can't use the same
         # connection from two threads
         self.node = get_rpc_proxy(node.url, 1, timeout=600, coveragedir=node.coverage_dir)
 
     def run(self):
-        self.node.getblocktemplate({'longpollid':self.longpollid})
+        self.node.getblocktemplate({'longpollid': self.longpollid, 'rules': ['segwit']})
 
 class GetBlockTemplateLPTest(BitcoinTestFramework):
     def set_test_params(self):
@@ -34,10 +34,10 @@ class GetBlockTemplateLPTest(BitcoinTestFramework):
     def run_test(self):
         self.log.info("Warning: this test will take about 70 seconds in the best case. Be patient.")
         self.nodes[0].generate(10)
-        template = self.nodes[0].getblocktemplate()
+        template = self.nodes[0].getblocktemplate({'rules': ['segwit']})
         longpollid = template['longpollid']
         # longpollid should not change between successive invocations if nothing else happens
-        template2 = self.nodes[0].getblocktemplate()
+        template2 = self.nodes[0].getblocktemplate({'rules': ['segwit']})
         assert(template2['longpollid'] == longpollid)
 
         # Test 1: test that the longpolling wait if we do nothing
diff --git a/test/functional/mining_prioritisetransaction.py b/test/functional/mining_prioritisetransaction.py
index da16bfbbf..ca4b621a7 100755
--- a/test/functional/mining_prioritisetransaction.py
+++ b/test/functional/mining_prioritisetransaction.py
@@ -142,10 +142,10 @@ class PrioritiseTransactionTest(BitcoinTestFramework):
         # getblocktemplate to (eventually) return a new block.
         mock_time = int(time.time())
         self.nodes[0].setmocktime(mock_time)
-        template = self.nodes[0].getblocktemplate()
+        template = self.nodes[0].getblocktemplate({'rules': ['segwit']})
         self.nodes[0].prioritisetransaction(txid=tx_id, fee_delta=-int(self.relayfee*COIN))
         self.nodes[0].setmocktime(mock_time+10)
-        new_template = self.nodes[0].getblocktemplate()
+        new_template = self.nodes[0].getblocktemplate({'rules': ['segwit']})
 
         assert(template != new_template)
 
diff --git a/test/functional/p2p_segwit.py b/test/functional/p2p_segwit.py
index afbbfa899..d95da227e 100755
--- a/test/functional/p2p_segwit.py
+++ b/test/functional/p2p_segwit.py
@@ -545,31 +545,13 @@ class SegWitTest(BitcoinTestFramework):
 
     @subtest
     def test_getblocktemplate_before_lockin(self):
-        # Node0 is segwit aware, node2 is not.
-        for node in [self.nodes[0], self.nodes[2]]:
-            gbt_results = node.getblocktemplate()
-            block_version = gbt_results['version']
-            # If we're not indicating segwit support, we will still be
-            # signalling for segwit activation.
-            assert_equal((block_version & (1 << VB_WITNESS_BIT) != 0), node == self.nodes[0])
-            # If we don't specify the segwit rule, then we won't get a default
-            # commitment.
-            assert('default_witness_commitment' not in gbt_results)
-
-        # Workaround:
-        # Can either change the tip, or change the mempool and wait 5 seconds
-        # to trigger a recomputation of getblocktemplate.
         txid = int(self.nodes[0].sendtoaddress(self.nodes[0].getnewaddress(), 1), 16)
-        # Using mocktime lets us avoid sleep()
-        sync_mempools(self.nodes)
-        self.nodes[0].setmocktime(int(time.time()) + 10)
-        self.nodes[2].setmocktime(int(time.time()) + 10)
 
         for node in [self.nodes[0], self.nodes[2]]:
             gbt_results = node.getblocktemplate({"rules": ["segwit"]})
             block_version = gbt_results['version']
             if node == self.nodes[2]:
-                # If this is a non-segwit node, we should still not get a witness
+                # If this is a non-segwit node, we should not get a witness
                 # commitment, nor a version bit signalling segwit.
                 assert_equal(block_version & (1 << VB_WITNESS_BIT), 0)
                 assert('default_witness_commitment' not in gbt_results)
@@ -586,10 +568,6 @@ class SegWitTest(BitcoinTestFramework):
                 script = get_witness_script(witness_root, 0)
                 assert_equal(witness_commitment, bytes_to_hex_str(script))
 
-        # undo mocktime
-        self.nodes[0].setmocktime(0)
-        self.nodes[2].setmocktime(0)
-
     @subtest
     def advance_to_segwit_lockin(self):
         """Mine enough blocks to lock in segwit, but don't activate."""