Merge bitcoin/bitcoin#22378: test: remove confusing `MAX_BLOCK_BASE_SIZE`

607076d01bf23c69ac21950c17b01fb4e1130774 test: remove confusing `MAX_BLOCK_BASE_SIZE` (Sebastian Falbesoner)
4af97c74edcda56cd15523bf3a335adea2bad14a test: introduce `get_weight()` helper for CBlock (Sebastian Falbesoner)
a084ebe1330bcec15715e08b0f65319142927ad1 test: introduce `get_weight()` helper for CTransaction (Sebastian Falbesoner)

Pull request description:

  This is a very late follow-up PR to #10618, which removed the constant `MAX_BLOCK_BASE_SIZE` from the core implementation about four years ago (see also #10608 in why it was considered confusing and superfluous).
  Since there is also no point in still keeping it in the functional test framework, the PR switches to weight-based accounting on the relevant test code parts and use `MAX_BLOCK_WEIGHT` instead for the block limit checks. To prepare that, the first two commits introduce `get_weight()` helpers for the classes CTransaction and CBlock, respectively.

ACKs for top commit:
  MarcoFalke:
    review ACK 607076d01bf23c69ac21950c17b01fb4e1130774 🚴

Tree-SHA512: d59aa0b6b3dfd0a849b8063e66de275d252f705f99e25cd3bf6daec028b47d946777ee5b42a060f5283cb18e917ac073119c2c0e11bbc21211f69ef0a6ed335a

6 files changed, 57 insertions, 62 deletions

diff --git a/test/functional/feature_block.py b/test/functional/feature_block.py
index c11eabc917..227be16487 100755
--- a/test/functional/feature_block.py
+++ b/test/functional/feature_block.py
@@ -22,7 +22,7 @@ from test_framework.messages import (
     CTransaction,
     CTxIn,
     CTxOut,
-    MAX_BLOCK_BASE_SIZE,
+    MAX_BLOCK_WEIGHT,
     uint256_from_compact,
     uint256_from_str,
 )
@@ -307,33 +307,33 @@ class FullBlockTest(BitcoinTestFramework):
         b22 = self.next_block(22, spend=out[5])
         self.send_blocks([b22], success=False, reject_reason='bad-txns-premature-spend-of-coinbase', reconnect=True)
 
-        # Create a block on either side of MAX_BLOCK_BASE_SIZE and make sure its accepted/rejected
+        # Create a block on either side of MAX_BLOCK_WEIGHT and make sure its accepted/rejected
         #     genesis -> b1 (0) -> b2 (1) -> b5 (2) -> b6  (3)
         #                                          \-> b12 (3) -> b13 (4) -> b15 (5) -> b23 (6)
         #                                                                           \-> b24 (6) -> b25 (7)
         #                      \-> b3 (1) -> b4 (2)
-        self.log.info("Accept a block of size MAX_BLOCK_BASE_SIZE")
+        self.log.info("Accept a block of weight MAX_BLOCK_WEIGHT")
         self.move_tip(15)
         b23 = self.next_block(23, spend=out[6])
         tx = CTransaction()
-        script_length = MAX_BLOCK_BASE_SIZE - len(b23.serialize()) - 69
+        script_length = (MAX_BLOCK_WEIGHT - b23.get_weight() - 276) // 4
         script_output = CScript([b'\x00' * script_length])
         tx.vout.append(CTxOut(0, script_output))
         tx.vin.append(CTxIn(COutPoint(b23.vtx[1].sha256, 0)))
         b23 = self.update_block(23, [tx])
-        # Make sure the math above worked out to produce a max-sized block
-        assert_equal(len(b23.serialize()), MAX_BLOCK_BASE_SIZE)
+        # Make sure the math above worked out to produce a max-weighted block
+        assert_equal(b23.get_weight(), MAX_BLOCK_WEIGHT)
         self.send_blocks([b23], True)
         self.save_spendable_output()
 
-        self.log.info("Reject a block of size MAX_BLOCK_BASE_SIZE + 1")
+        self.log.info("Reject a block of weight MAX_BLOCK_WEIGHT + 4")
         self.move_tip(15)
         b24 = self.next_block(24, spend=out[6])
-        script_length = MAX_BLOCK_BASE_SIZE - len(b24.serialize()) - 69
+        script_length = (MAX_BLOCK_WEIGHT - b24.get_weight() - 276) // 4
         script_output = CScript([b'\x00' * (script_length + 1)])
         tx.vout = [CTxOut(0, script_output)]
         b24 = self.update_block(24, [tx])
-        assert_equal(len(b24.serialize()), MAX_BLOCK_BASE_SIZE + 1)
+        assert_equal(b24.get_weight(), MAX_BLOCK_WEIGHT + 1 * 4)
         self.send_blocks([b24], success=False, reject_reason='bad-blk-length', reconnect=True)
 
         b25 = self.next_block(25, spend=out[7])
@@ -484,13 +484,13 @@ class FullBlockTest(BitcoinTestFramework):
         # Until block is full, add tx's with 1 satoshi to p2sh_script, the rest to OP_TRUE
         tx_new = None
         tx_last = tx
-        total_size = len(b39.serialize())
-        while(total_size < MAX_BLOCK_BASE_SIZE):
+        total_weight = b39.get_weight()
+        while total_weight < MAX_BLOCK_WEIGHT:
             tx_new = self.create_tx(tx_last, 1, 1, p2sh_script)
             tx_new.vout.append(CTxOut(tx_last.vout[1].nValue - 1, CScript([OP_TRUE])))
             tx_new.rehash()
-            total_size += len(tx_new.serialize())
-            if total_size >= MAX_BLOCK_BASE_SIZE:
+            total_weight += tx_new.get_weight()
+            if total_weight >= MAX_BLOCK_WEIGHT:
                 break
             b39.vtx.append(tx_new)  # add tx to block
             tx_last = tx_new
@@ -501,7 +501,7 @@ class FullBlockTest(BitcoinTestFramework):
         # Make sure we didn't accidentally make too big a block. Note that the
         # size of the block has non-determinism due to the ECDSA signature in
         # the first transaction.
-        while (len(b39.serialize()) >= MAX_BLOCK_BASE_SIZE):
+        while b39.get_weight() >= MAX_BLOCK_WEIGHT:
             del b39.vtx[-1]
 
         b39 = self.update_block(39, [])
@@ -891,7 +891,7 @@ class FullBlockTest(BitcoinTestFramework):
         self.send_blocks([b63], success=False, reject_reason='bad-txns-nonfinal', reconnect=True)
 
         #  This checks that a block with a bloated VARINT between the block_header and the array of tx such that
-        #  the block is > MAX_BLOCK_BASE_SIZE with the bloated varint, but <= MAX_BLOCK_BASE_SIZE without the bloated varint,
+        #  the block is > MAX_BLOCK_WEIGHT with the bloated varint, but <= MAX_BLOCK_WEIGHT without the bloated varint,
         #  does not cause a subsequent, identical block with canonical encoding to be rejected.  The test does not
         #  care whether the bloated block is accepted or rejected; it only cares that the second block is accepted.
         #
@@ -916,12 +916,12 @@ class FullBlockTest(BitcoinTestFramework):
         tx = CTransaction()
 
         # use canonical serialization to calculate size
-        script_length = MAX_BLOCK_BASE_SIZE - len(b64a.normal_serialize()) - 69
+        script_length = (MAX_BLOCK_WEIGHT - 4 * len(b64a.normal_serialize()) - 276) // 4
         script_output = CScript([b'\x00' * script_length])
         tx.vout.append(CTxOut(0, script_output))
         tx.vin.append(CTxIn(COutPoint(b64a.vtx[1].sha256, 0)))
         b64a = self.update_block("64a", [tx])
-        assert_equal(len(b64a.serialize()), MAX_BLOCK_BASE_SIZE + 8)
+        assert_equal(b64a.get_weight(), MAX_BLOCK_WEIGHT + 8 * 4)
         self.send_blocks([b64a], success=False, reject_reason='non-canonical ReadCompactSize()')
 
         # bitcoind doesn't disconnect us for sending a bloated block, but if we subsequently
@@ -935,7 +935,7 @@ class FullBlockTest(BitcoinTestFramework):
         b64 = CBlock(b64a)
         b64.vtx = copy.deepcopy(b64a.vtx)
         assert_equal(b64.hash, b64a.hash)
-        assert_equal(len(b64.serialize()), MAX_BLOCK_BASE_SIZE)
+        assert_equal(b64.get_weight(), MAX_BLOCK_WEIGHT)
         self.blocks[64] = b64
         b64 = self.update_block(64, [])
         self.send_blocks([b64], True)
@@ -1269,12 +1269,12 @@ class FullBlockTest(BitcoinTestFramework):
         for i in range(89, LARGE_REORG_SIZE + 89):
             b = self.next_block(i, spend)
             tx = CTransaction()
-            script_length = MAX_BLOCK_BASE_SIZE - len(b.serialize()) - 69
+            script_length = (MAX_BLOCK_WEIGHT - b.get_weight() - 276) // 4
             script_output = CScript([b'\x00' * script_length])
             tx.vout.append(CTxOut(0, script_output))
             tx.vin.append(CTxIn(COutPoint(b.vtx[1].sha256, 0)))
             b = self.update_block(i, [tx])
-            assert_equal(len(b.serialize()), MAX_BLOCK_BASE_SIZE)
+            assert_equal(b.get_weight(), MAX_BLOCK_WEIGHT)
             blocks.append(b)
             self.save_spendable_output()
             spend = self.get_spendable_output()
diff --git a/test/functional/feature_segwit.py b/test/functional/feature_segwit.py
index f36575627e..cbd8521499 100755
--- a/test/functional/feature_segwit.py
+++ b/test/functional/feature_segwit.py
@@ -259,8 +259,8 @@ class SegWitTest(BitcoinTestFramework):
         assert_equal(int(self.nodes[0].getmempoolentry(txid1)["wtxid"], 16), tx1.calc_sha256(True))
 
         # Check that weight and vsize are properly reported in mempool entry (txid1)
-        assert_equal(self.nodes[0].getmempoolentry(txid1)["vsize"], (self.nodes[0].getmempoolentry(txid1)["weight"] + 3) // 4)
-        assert_equal(self.nodes[0].getmempoolentry(txid1)["weight"], len(tx1.serialize_without_witness())*3 + len(tx1.serialize_with_witness()))
+        assert_equal(self.nodes[0].getmempoolentry(txid1)["vsize"], tx1.get_vsize())
+        assert_equal(self.nodes[0].getmempoolentry(txid1)["weight"], tx1.get_weight())
 
         # Now create tx2, which will spend from txid1.
         tx = CTransaction()
@@ -275,8 +275,8 @@ class SegWitTest(BitcoinTestFramework):
         assert_equal(int(self.nodes[0].getmempoolentry(txid2)["wtxid"], 16), tx.calc_sha256(True))
 
         # Check that weight and vsize are properly reported in mempool entry (txid2)
-        assert_equal(self.nodes[0].getmempoolentry(txid2)["vsize"], (self.nodes[0].getmempoolentry(txid2)["weight"] + 3) // 4)
-        assert_equal(self.nodes[0].getmempoolentry(txid2)["weight"], len(tx.serialize_without_witness())*3 + len(tx.serialize_with_witness()))
+        assert_equal(self.nodes[0].getmempoolentry(txid2)["vsize"], tx.get_vsize())
+        assert_equal(self.nodes[0].getmempoolentry(txid2)["weight"], tx.get_weight())
 
         # Now create tx3, which will spend from txid2
         tx = CTransaction()
@@ -298,8 +298,8 @@ class SegWitTest(BitcoinTestFramework):
         assert_equal(int(self.nodes[0].getmempoolentry(txid3)["wtxid"], 16), tx.calc_sha256(True))
 
         # Check that weight and vsize are properly reported in mempool entry (txid3)
-        assert_equal(self.nodes[0].getmempoolentry(txid3)["vsize"], (self.nodes[0].getmempoolentry(txid3)["weight"] + 3) // 4)
-        assert_equal(self.nodes[0].getmempoolentry(txid3)["weight"], len(tx.serialize_without_witness())*3 + len(tx.serialize_with_witness()))
+        assert_equal(self.nodes[0].getmempoolentry(txid3)["vsize"], tx.get_vsize())
+        assert_equal(self.nodes[0].getmempoolentry(txid3)["weight"], tx.get_weight())
 
         # Mine a block to clear the gbt cache again.
         self.nodes[0].generate(1)
diff --git a/test/functional/mempool_accept.py b/test/functional/mempool_accept.py
index 60c0953f6f..97d29ff197 100755
--- a/test/functional/mempool_accept.py
+++ b/test/functional/mempool_accept.py
@@ -15,7 +15,7 @@ from test_framework.messages import (
     COutPoint,
     CTxIn,
     CTxOut,
-    MAX_BLOCK_BASE_SIZE,
+    MAX_BLOCK_WEIGHT,
     MAX_MONEY,
     tx_from_hex,
 )
@@ -209,7 +209,7 @@ class MempoolAcceptanceTest(BitcoinTestFramework):
 
         self.log.info('A really large transaction')
         tx = tx_from_hex(raw_tx_reference)
-        tx.vin = [tx.vin[0]] * math.ceil(MAX_BLOCK_BASE_SIZE / len(tx.vin[0].serialize()))
+        tx.vin = [tx.vin[0]] * math.ceil(MAX_BLOCK_WEIGHT // 4 / len(tx.vin[0].serialize()))
         self.check_mempool_result(
             result_expected=[{'txid': tx.rehash(), 'allowed': False, 'reject-reason': 'bad-txns-oversize'}],
             rawtxs=[tx.serialize().hex()],
diff --git a/test/functional/mining_prioritisetransaction.py b/test/functional/mining_prioritisetransaction.py
index 1426fdaacb..9fc38ebf53 100755
--- a/test/functional/mining_prioritisetransaction.py
+++ b/test/functional/mining_prioritisetransaction.py
@@ -6,7 +6,7 @@
 
 import time
 
-from test_framework.messages import COIN, MAX_BLOCK_BASE_SIZE
+from test_framework.messages import COIN, MAX_BLOCK_WEIGHT
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import assert_equal, assert_raises_rpc_error, create_confirmed_utxos, create_lots_of_big_transactions, gen_return_txouts
 
@@ -61,15 +61,15 @@ class PrioritiseTransactionTest(BitcoinTestFramework):
             txids[i] = create_lots_of_big_transactions(self.nodes[0], self.txouts, utxos[start_range:end_range], end_range - start_range, (i+1)*base_fee)
 
         # Make sure that the size of each group of transactions exceeds
-        # MAX_BLOCK_BASE_SIZE -- otherwise the test needs to be revised to create
-        # more transactions.
+        # MAX_BLOCK_WEIGHT // 4 -- otherwise the test needs to be revised to
+        # create more transactions.
         mempool = self.nodes[0].getrawmempool(True)
         sizes = [0, 0, 0]
         for i in range(3):
             for j in txids[i]:
                 assert j in mempool
                 sizes[i] += mempool[j]['vsize']
-            assert sizes[i] > MAX_BLOCK_BASE_SIZE  # Fail => raise utxo_count
+            assert sizes[i] > MAX_BLOCK_WEIGHT // 4  # Fail => raise utxo_count
 
         # add a fee delta to something in the cheapest bucket and make sure it gets mined
         # also check that a different entry in the cheapest bucket is NOT mined
diff --git a/test/functional/p2p_segwit.py b/test/functional/p2p_segwit.py
index c53feaf0c6..e5093855ff 100755
--- a/test/functional/p2p_segwit.py
+++ b/test/functional/p2p_segwit.py
@@ -4,7 +4,6 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Test segwit transactions and blocks on P2P network."""
 from decimal import Decimal
-import math
 import random
 import struct
 import time
@@ -21,7 +20,7 @@ from test_framework.messages import (
     CTxInWitness,
     CTxOut,
     CTxWitness,
-    MAX_BLOCK_BASE_SIZE,
+    MAX_BLOCK_WEIGHT,
     MSG_BLOCK,
     MSG_TX,
     MSG_WITNESS_FLAG,
@@ -106,16 +105,6 @@ def sign_p2pk_witness_input(script, tx_to, in_idx, hashtype, value, key):
     tx_to.wit.vtxinwit[in_idx].scriptWitness.stack = [signature, script]
     tx_to.rehash()
 
-def get_virtual_size(witness_block):
-    """Calculate the virtual size of a witness block.
-
-    Virtual size is base + witness/4."""
-    base_size = len(witness_block.serialize(with_witness=False))
-    total_size = len(witness_block.serialize())
-    # the "+3" is so we round up
-    vsize = int((3 * base_size + total_size + 3) / 4)
-    return vsize
-
 def test_transaction_acceptance(node, p2p, tx, with_witness, accepted, reason=None):
     """Send a transaction to the node and check that it's accepted to the mempool
 
@@ -437,8 +426,7 @@ class SegWitTest(BitcoinTestFramework):
             rpc_details = self.nodes[0].getblock(block.hash, True)
             assert_equal(rpc_details["size"], len(block.serialize()))
             assert_equal(rpc_details["strippedsize"], len(block.serialize(False)))
-            weight = 3 * len(block.serialize(False)) + len(block.serialize())
-            assert_equal(rpc_details["weight"], weight)
+            assert_equal(rpc_details["weight"], block.get_weight())
 
             # Upgraded node should not ask for blocks from unupgraded
             block4 = self.build_next_block(version=4)
@@ -849,7 +837,7 @@ class SegWitTest(BitcoinTestFramework):
         block.solve()
 
         block.vtx[0].wit.vtxinwit[0].scriptWitness.stack.append(b'a' * 5000000)
-        assert get_virtual_size(block) > MAX_BLOCK_BASE_SIZE
+        assert block.get_weight() > MAX_BLOCK_WEIGHT
 
         # We can't send over the p2p network, because this is too big to relay
         # TODO: repeat this test with a block that can be relayed
@@ -858,7 +846,7 @@ class SegWitTest(BitcoinTestFramework):
         assert self.nodes[0].getbestblockhash() != block.hash
 
         block.vtx[0].wit.vtxinwit[0].scriptWitness.stack.pop()
-        assert get_virtual_size(block) < MAX_BLOCK_BASE_SIZE
+        assert block.get_weight() < MAX_BLOCK_WEIGHT
         assert_equal(None, self.nodes[0].submitblock(block.serialize().hex()))
 
         assert self.nodes[0].getbestblockhash() == block.hash
@@ -920,11 +908,10 @@ class SegWitTest(BitcoinTestFramework):
         child_tx.rehash()
         self.update_witness_block_with_transactions(block, [parent_tx, child_tx])
 
-        vsize = get_virtual_size(block)
-        additional_bytes = (MAX_BLOCK_BASE_SIZE - vsize) * 4
+        additional_bytes = MAX_BLOCK_WEIGHT - block.get_weight()
         i = 0
         while additional_bytes > 0:
-            # Add some more bytes to each input until we hit MAX_BLOCK_BASE_SIZE+1
+            # Add some more bytes to each input until we hit MAX_BLOCK_WEIGHT+1
             extra_bytes = min(additional_bytes + 1, 55)
             block.vtx[-1].wit.vtxinwit[int(i / (2 * NUM_DROPS))].scriptWitness.stack[i % (2 * NUM_DROPS)] = b'a' * (195 + extra_bytes)
             additional_bytes -= extra_bytes
@@ -933,8 +920,7 @@ class SegWitTest(BitcoinTestFramework):
         block.vtx[0].vout.pop()  # Remove old commitment
         add_witness_commitment(block)
         block.solve()
-        vsize = get_virtual_size(block)
-        assert_equal(vsize, MAX_BLOCK_BASE_SIZE + 1)
+        assert_equal(block.get_weight(), MAX_BLOCK_WEIGHT + 1)
         # Make sure that our test case would exceed the old max-network-message
         # limit
         assert len(block.serialize()) > 2 * 1024 * 1024
@@ -947,7 +933,7 @@ class SegWitTest(BitcoinTestFramework):
         block.vtx[0].vout.pop()
         add_witness_commitment(block)
         block.solve()
-        assert get_virtual_size(block) == MAX_BLOCK_BASE_SIZE
+        assert block.get_weight() == MAX_BLOCK_WEIGHT
 
         test_witness_block(self.nodes[0], self.test_node, block, accepted=True)
 
@@ -1304,10 +1290,9 @@ class SegWitTest(BitcoinTestFramework):
         raw_tx = self.nodes[0].getrawtransaction(tx3.hash, 1)
         assert_equal(int(raw_tx["hash"], 16), tx3.calc_sha256(True))
         assert_equal(raw_tx["size"], len(tx3.serialize_with_witness()))
-        weight = len(tx3.serialize_with_witness()) + 3 * len(tx3.serialize_without_witness())
-        vsize = math.ceil(weight / 4)
+        vsize = tx3.get_vsize()
         assert_equal(raw_tx["vsize"], vsize)
-        assert_equal(raw_tx["weight"], weight)
+        assert_equal(raw_tx["weight"], tx3.get_weight())
         assert_equal(len(raw_tx["vin"][0]["txinwitness"]), 1)
         assert_equal(raw_tx["vin"][0]["txinwitness"][0], witness_script.hex())
         assert vsize != raw_tx["size"]
@@ -1663,7 +1648,7 @@ class SegWitTest(BitcoinTestFramework):
             block.vtx.append(tx)
 
             # Test the block periodically, if we're close to maxblocksize
-            if (get_virtual_size(block) > MAX_BLOCK_BASE_SIZE - 1000):
+            if block.get_weight() > MAX_BLOCK_WEIGHT - 4000:
                 self.update_witness_block_with_transactions(block, [])
                 test_witness_block(self.nodes[0], self.test_node, block, accepted=True)
                 block = self.build_next_block()
diff --git a/test/functional/test_framework/messages.py b/test/functional/test_framework/messages.py
index 0523627cef..57a2c7da47 100755
--- a/test/functional/test_framework/messages.py
+++ b/test/functional/test_framework/messages.py
@@ -33,7 +33,7 @@ from test_framework.siphash import siphash256
 from test_framework.util import assert_equal
 
 MAX_LOCATOR_SZ = 101
-MAX_BLOCK_BASE_SIZE = 1000000
+MAX_BLOCK_WEIGHT = 4000000
 MAX_BLOOM_FILTER_SIZE = 36000
 MAX_BLOOM_HASH_FUNCS = 50
 
@@ -608,12 +608,15 @@ class CTransaction:
                 return False
         return True
 
-    # Calculate the virtual transaction size using witness and non-witness
+    # Calculate the transaction weight using witness and non-witness
     # serialization size (does NOT use sigops).
-    def get_vsize(self):
+    def get_weight(self):
         with_witness_size = len(self.serialize_with_witness())
         without_witness_size = len(self.serialize_without_witness())
-        return math.ceil(((WITNESS_SCALE_FACTOR - 1) * without_witness_size + with_witness_size) / WITNESS_SCALE_FACTOR)
+        return (WITNESS_SCALE_FACTOR - 1) * without_witness_size + with_witness_size
+
+    def get_vsize(self):
+        return math.ceil(self.get_weight() / WITNESS_SCALE_FACTOR)
 
     def __repr__(self):
         return "CTransaction(nVersion=%i vin=%s vout=%s wit=%s nLockTime=%i)" \
@@ -761,6 +764,13 @@ class CBlock(CBlockHeader):
             self.nNonce += 1
             self.rehash()
 
+    # Calculate the block weight using witness and non-witness
+    # serialization size (does NOT use sigops).
+    def get_weight(self):
+        with_witness_size = len(self.serialize(with_witness=True))
+        without_witness_size = len(self.serialize(with_witness=False))
+        return (WITNESS_SCALE_FACTOR - 1) * without_witness_size + with_witness_size
+
     def __repr__(self):
         return "CBlock(nVersion=%i hashPrevBlock=%064x hashMerkleRoot=%064x nTime=%s nBits=%08x nNonce=%08x vtx=%s)" \
             % (self.nVersion, self.hashPrevBlock, self.hashMerkleRoot,