1 files changed, 144 insertions, 0 deletions
diff --git a/test/functional/p2p_headers_sync_with_minchainwork.py b/test/functional/p2p_headers_sync_with_minchainwork.py
new file mode 100755
index 0000000000..6e17525c28
--- /dev/null
+++ b/test/functional/p2p_headers_sync_with_minchainwork.py
@@ -0,0 +1,144 @@
+#!/usr/bin/env python3
+# Copyright (c) 2019-2021 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 we reject low difficulty headers to prevent our block tree from filling up with useless bloat"""
+
+from test_framework.test_framework import BitcoinTestFramework
+
+from test_framework.p2p import (
+    P2PInterface,
+)
+
+from test_framework.messages import (
+    msg_headers,
+)
+
+from test_framework.blocktools import (
+    NORMAL_GBT_REQUEST_PARAMS,
+    create_block,
+)
+
+from test_framework.util import assert_equal
+
+NODE1_BLOCKS_REQUIRED = 15
+NODE2_BLOCKS_REQUIRED = 2047
+
+
+class RejectLowDifficultyHeadersTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.setup_clean_chain = True
+        self.num_nodes = 3
+        # Node0 has no required chainwork; node1 requires 15 blocks on top of the genesis block; node2 requires 2047
+        self.extra_args = [["-minimumchainwork=0x0", "-checkblockindex=0"], ["-minimumchainwork=0x1f", "-checkblockindex=0"], ["-minimumchainwork=0x1000", "-checkblockindex=0"]]
+
+    def setup_network(self):
+        self.setup_nodes()
+        self.reconnect_all()
+        self.sync_all()
+
+    def disconnect_all(self):
+        self.disconnect_nodes(0, 1)
+        self.disconnect_nodes(0, 2)
+
+    def reconnect_all(self):
+        self.connect_nodes(0, 1)
+        self.connect_nodes(0, 2)
+
+    def test_chains_sync_when_long_enough(self):
+        self.log.info("Generate blocks on the node with no required chainwork, and verify nodes 1 and 2 have no new headers in their headers tree")
+        with self.nodes[1].assert_debug_log(expected_msgs=["[net] Ignoring low-work chain (height=14)"]), self.nodes[2].assert_debug_log(expected_msgs=["[net] Ignoring low-work chain (height=14)"]):
+            self.generate(self.nodes[0], NODE1_BLOCKS_REQUIRED-1, sync_fun=self.no_op)
+
+        for node in self.nodes[1:]:
+            chaintips = node.getchaintips()
+            assert(len(chaintips) == 1)
+            assert {
+                'height': 0,
+                'hash': '0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206',
+                'branchlen': 0,
+                'status': 'active',
+            } in chaintips
+
+        self.log.info("Generate more blocks to satisfy node1's minchainwork requirement, and verify node2 still has no new headers in headers tree")
+        with self.nodes[2].assert_debug_log(expected_msgs=["[net] Ignoring low-work chain (height=15)"]):
+            self.generate(self.nodes[0], NODE1_BLOCKS_REQUIRED - self.nodes[0].getblockcount(), sync_fun=self.no_op)
+        self.sync_blocks(self.nodes[0:2])
+
+        assert {
+            'height': 0,
+            'hash': '0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206',
+            'branchlen': 0,
+            'status': 'active',
+        } in self.nodes[2].getchaintips()
+
+        assert(len(self.nodes[2].getchaintips()) == 1)
+
+        self.log.info("Generate long chain for node0/node1")
+        self.generate(self.nodes[0], NODE2_BLOCKS_REQUIRED-self.nodes[0].getblockcount(), sync_fun=self.no_op)
+
+        self.log.info("Verify that node2 will sync the chain when it gets long enough")
+        self.sync_blocks()
+
+    def test_peerinfo_includes_headers_presync_height(self):
+        self.log.info("Test that getpeerinfo() includes headers presync height")
+
+        # Disconnect network, so that we can find our own peer connection more
+        # easily
+        self.disconnect_all()
+
+        p2p = self.nodes[0].add_p2p_connection(P2PInterface())
+        node = self.nodes[0]
+
+        # Ensure we have a long chain already
+        current_height = self.nodes[0].getblockcount()
+        if (current_height < 3000):
+            self.generate(node, 3000-current_height, sync_fun=self.no_op)
+
+        # Send a group of 2000 headers, forking from genesis.
+        new_blocks = []
+        hashPrevBlock = int(node.getblockhash(0), 16)
+        for i in range(2000):
+            block = create_block(hashprev = hashPrevBlock, tmpl=node.getblocktemplate(NORMAL_GBT_REQUEST_PARAMS))
+            block.solve()
+            new_blocks.append(block)
+            hashPrevBlock = block.sha256
+
+        headers_message = msg_headers(headers=new_blocks)
+        p2p.send_and_ping(headers_message)
+
+        # getpeerinfo should show a sync in progress
+        assert_equal(node.getpeerinfo()[0]['presynced_headers'], 2000)
+
+    def test_large_reorgs_can_succeed(self):
+        self.log.info("Test that a 2000+ block reorg, starting from a point that is more than 2000 blocks before a locator entry, can succeed")
+
+        self.sync_all() # Ensure all nodes are synced.
+        self.disconnect_all()
+
+        # locator(block at height T) will have heights:
+        # [T, T-1, ..., T-10, T-12, T-16, T-24, T-40, T-72, T-136, T-264,
+        #  T-520, T-1032, T-2056, T-4104, ...]
+        # So mine a number of blocks > 4104 to ensure that the first window of
+        # received headers during a sync are fully between locator entries.
+        BLOCKS_TO_MINE = 4110
+
+        self.generate(self.nodes[0], BLOCKS_TO_MINE, sync_fun=self.no_op)
+        self.generate(self.nodes[1], BLOCKS_TO_MINE+2, sync_fun=self.no_op)
+
+        self.reconnect_all()
+
+        self.sync_blocks(timeout=300) # Ensure tips eventually agree
+
+
+    def run_test(self):
+        self.test_chains_sync_when_long_enough()
+
+        self.test_large_reorgs_can_succeed()
+
+        self.test_peerinfo_includes_headers_presync_height()
+
+
+
+if __name__ == '__main__':
+    RejectLowDifficultyHeadersTest().main()