Add test for getheaders behavior

Expect responses to a getheaders iff the node has a chain with more than nMinimumChainWork

test/functional/feature_minchainwork.py

@@ -17,6 +17,7 @@ only succeeds past a given node once its nMinimumChainWork has been exceeded.
 
 import time
 
+from test_framework.p2p import P2PInterface, msg_getheaders
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import assert_equal
 
@@ -41,6 +42,9 @@ class MinimumChainWorkTest(BitcoinTestFramework):
         for i in range(self.num_nodes-1):
             self.connect_nodes(i+1, i)
 
+        # Set clock of node2 2 days ahead, to keep it in IBD during this test.
+        self.nodes[2].setmocktime(int(time.time()) + 48*60*60)
+
     def run_test(self):
         # Start building a chain on node0.  node2 shouldn't be able to sync until node1's
         # minchainwork is exceeded
@@ -71,6 +75,15 @@ class MinimumChainWorkTest(BitcoinTestFramework):
         assert self.nodes[1].getbestblockhash() != self.nodes[0].getbestblockhash()
         assert_equal(self.nodes[2].getblockcount(), starting_blockcount)
 
+        self.log.info("Check that getheaders requests to node2 are ignored")
+        peer = self.nodes[2].add_p2p_connection(P2PInterface())
+        msg = msg_getheaders()
+        msg.locator.vHave = [int(self.nodes[2].getbestblockhash(), 16)]
+        msg.hashstop = 0
+        peer.send_and_ping(msg)
+        time.sleep(5)
+        assert "headers" not in peer.last_message
+
         self.log.info("Generating one more block")
         self.generate(self.nodes[0], 1)
 
@@ -85,5 +98,13 @@ class MinimumChainWorkTest(BitcoinTestFramework):
         self.sync_all()
         self.log.info(f"Blockcounts: {[n.getblockcount() for n in self.nodes]}")
 
+        self.log.info("Test that getheaders requests to node2 are not ignored")
+        peer.send_and_ping(msg)
+        assert "headers" in peer.last_message
+
+        # Verify that node2 is in fact still in IBD (otherwise this test may
+        # not be exercising the logic we want!)
+        assert_equal(self.nodes[2].getblockchaininfo()['initialblockdownload'], True)
+
 if __name__ == '__main__':
     MinimumChainWorkTest().main()