test: add functional test for complex reorgs

test/functional/feature_chain_tiebreaks.py

@@ -0,0 +1,103 @@
+#!/usr/bin/env python3
+# Copyright (c) The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Test that the correct active block is chosen in complex reorgs."""
+
+from test_framework.blocktools import create_block
+from test_framework.messages import CBlockHeader
+from test_framework.p2p import P2PDataStore
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_equal
+
+class ChainTiebreaksTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 2
+        self.setup_clean_chain = True
+
+    @staticmethod
+    def send_headers(node, blocks):
+        """Submit headers for blocks to node."""
+        for block in blocks:
+            # Use RPC rather than P2P, to prevent the message from being interpreted as a block
+            # announcement.
+            node.submitheader(hexdata=CBlockHeader(block).serialize().hex())
+
+    def run_test(self):
+        node = self.nodes[0]
+        # Add P2P connection to bitcoind
+        peer = node.add_p2p_connection(P2PDataStore())
+
+        self.log.info('Precomputing blocks')
+        #
+        #          /- B3 -- B7
+        #        B1      \- B8
+        #       /  \
+        #      /    \ B4 -- B9
+        #   B0           \- B10
+        #      \
+        #       \  /- B5
+        #        B2
+        #          \- B6
+        #
+        blocks = []
+
+        # Construct B0, building off genesis.
+        start_height = node.getblockcount()
+        blocks.append(create_block(
+            hashprev=int(node.getbestblockhash(), 16),
+            tmpl={"height": start_height + 1}
+        ))
+        blocks[-1].solve()
+
+        # Construct B1-B10.
+        for i in range(1, 11):
+            blocks.append(create_block(
+                hashprev=blocks[(i - 1) >> 1].hash_int,
+                tmpl={
+                    "height": start_height + (i + 1).bit_length(),
+                    # Make sure each block has a different hash.
+                    "curtime": blocks[-1].nTime + 1,
+                }
+            ))
+            blocks[-1].solve()
+
+        self.log.info('Make sure B0 is accepted normally')
+        peer.send_blocks_and_test([blocks[0]], node, success=True)
+        # B0 must be active chain now.
+        assert_equal(node.getbestblockhash(), blocks[0].hash_hex)
+
+        self.log.info('Send B1 and B2 headers, and then blocks in opposite order')
+        self.send_headers(node, blocks[1:3])
+        peer.send_blocks_and_test([blocks[2]], node, success=True)
+        peer.send_blocks_and_test([blocks[1]], node, success=False)
+        # B2 must be active chain now, as full data for B2 was received first.
+        assert_equal(node.getbestblockhash(), blocks[2].hash_hex)
+
+        self.log.info('Send all further headers in order')
+        self.send_headers(node, blocks[3:])
+        # B2 is still the active chain, headers don't change this.
+        assert_equal(node.getbestblockhash(), blocks[2].hash_hex)
+
+        self.log.info('Send blocks B7-B10')
+        peer.send_blocks_and_test([blocks[7]], node, success=False)
+        peer.send_blocks_and_test([blocks[8]], node, success=False)
+        peer.send_blocks_and_test([blocks[9]], node, success=False)
+        peer.send_blocks_and_test([blocks[10]], node, success=False)
+        # B2 is still the active chain, as B7-B10 have missing parents.
+        assert_equal(node.getbestblockhash(), blocks[2].hash_hex)
+
+        self.log.info('Send parents B3-B4 of B8-B10 in reverse order')
+        peer.send_blocks_and_test([blocks[4]], node, success=False, force_send=True)
+        peer.send_blocks_and_test([blocks[3]], node, success=False, force_send=True)
+        # B9 is now active. Despite B7 being received earlier, the missing parent.
+        assert_equal(node.getbestblockhash(), blocks[9].hash_hex)
+
+        self.log.info('Invalidate B9-B10')
+        node.invalidateblock(blocks[9].hash_hex)
+        node.invalidateblock(blocks[10].hash_hex)
+        # B7 is now active.
+        assert_equal(node.getbestblockhash(), blocks[7].hash_hex)
+
+if __name__ == '__main__':
+    ChainTiebreaksTest(__file__).main()

test/functional/test_runner.py

@@ -320,6 +320,7 @@ BASE_SCRIPTS = [
     'feature_includeconf.py',
     'feature_addrman.py',
     'feature_asmap.py',
+    'feature_chain_tiebreaks.py',
     'feature_fastprune.py',
     'feature_framework_miniwallet.py',
     'mempool_unbroadcast.py',