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diff --git a/test/functional/p2p-acceptblock.py b/test/functional/p2p-acceptblock.py
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+++ b/test/functional/p2p-acceptblock.py
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+#!/usr/bin/env python3
+# Copyright (c) 2015-2016 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 processing of unrequested blocks.
+
+Since behavior differs when receiving unrequested blocks from whitelisted peers
+versus non-whitelisted peers, this tests the behavior of both (effectively two
+separate tests running in parallel).
+
+Setup: two nodes, node0 and node1, not connected to each other.  Node0 does not
+whitelist localhost, but node1 does. They will each be on their own chain for
+this test.
+
+We have one NodeConn connection to each, test_node and white_node respectively.
+
+The test:
+1. Generate one block on each node, to leave IBD.
+
+2. Mine a new block on each tip, and deliver to each node from node's peer.
+   The tip should advance.
+
+3. Mine a block that forks the previous block, and deliver to each node from
+   corresponding peer.
+   Node0 should not process this block (just accept the header), because it is
+   unrequested and doesn't have more work than the tip.
+   Node1 should process because this is coming from a whitelisted peer.
+
+4. Send another block that builds on the forking block.
+   Node0 should process this block but be stuck on the shorter chain, because
+   it's missing an intermediate block.
+   Node1 should reorg to this longer chain.
+
+4b.Send 288 more blocks on the longer chain.
+   Node0 should process all but the last block (too far ahead in height).
+   Send all headers to Node1, and then send the last block in that chain.
+   Node1 should accept the block because it's coming from a whitelisted peer.
+
+5. Send a duplicate of the block in #3 to Node0.
+   Node0 should not process the block because it is unrequested, and stay on
+   the shorter chain.
+
+6. Send Node0 an inv for the height 3 block produced in #4 above.
+   Node0 should figure out that Node0 has the missing height 2 block and send a
+   getdata.
+
+7. Send Node0 the missing block again.
+   Node0 should process and the tip should advance.
+"""
+
+from test_framework.mininode import *
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import *
+import time
+from test_framework.blocktools import create_block, create_coinbase
+
+# TestNode: bare-bones "peer".  Used mostly as a conduit for a test to sending
+# p2p messages to a node, generating the messages in the main testing logic.
+class TestNode(NodeConnCB):
+    def __init__(self):
+        super().__init__()
+        self.connection = None
+        self.ping_counter = 1
+        self.last_pong = msg_pong()
+
+    def add_connection(self, conn):
+        self.connection = conn
+
+    # Track the last getdata message we receive (used in the test)
+    def on_getdata(self, conn, message):
+        self.last_getdata = message
+
+    # Spin until verack message is received from the node.
+    # We use this to signal that our test can begin. This
+    # is called from the testing thread, so it needs to acquire
+    # the global lock.
+    def wait_for_verack(self):
+        while True:
+            with mininode_lock:
+                if self.verack_received:
+                    return
+            time.sleep(0.05)
+
+    # Wrapper for the NodeConn's send_message function
+    def send_message(self, message):
+        self.connection.send_message(message)
+
+    def on_pong(self, conn, message):
+        self.last_pong = message
+
+class AcceptBlockTest(BitcoinTestFramework):
+    def add_options(self, parser):
+        parser.add_option("--testbinary", dest="testbinary",
+                          default=os.getenv("BITCOIND", "bitcoind"),
+                          help="bitcoind binary to test")
+
+    def __init__(self):
+        super().__init__()
+        self.setup_clean_chain = True
+        self.num_nodes = 2
+
+    def setup_network(self):
+        # Node0 will be used to test behavior of processing unrequested blocks
+        # from peers which are not whitelisted, while Node1 will be used for
+        # the whitelisted case.
+        self.nodes = []
+        self.nodes.append(start_node(0, self.options.tmpdir,
+                                     binary=self.options.testbinary))
+        self.nodes.append(start_node(1, self.options.tmpdir,
+                                     ["-whitelist=127.0.0.1"],
+                                     binary=self.options.testbinary))
+
+    def run_test(self):
+        # Setup the p2p connections and start up the network thread.
+        test_node = TestNode()   # connects to node0 (not whitelisted)
+        white_node = TestNode()  # connects to node1 (whitelisted)
+
+        connections = []
+        connections.append(NodeConn('127.0.0.1', p2p_port(0), self.nodes[0], test_node))
+        connections.append(NodeConn('127.0.0.1', p2p_port(1), self.nodes[1], white_node))
+        test_node.add_connection(connections[0])
+        white_node.add_connection(connections[1])
+
+        NetworkThread().start() # Start up network handling in another thread
+
+        # Test logic begins here
+        test_node.wait_for_verack()
+        white_node.wait_for_verack()
+
+        # 1. Have both nodes mine a block (leave IBD)
+        [ n.generate(1) for n in self.nodes ]
+        tips = [ int("0x" + n.getbestblockhash(), 0) for n in self.nodes ]
+
+        # 2. Send one block that builds on each tip.
+        # This should be accepted.
+        blocks_h2 = []  # the height 2 blocks on each node's chain
+        block_time = int(time.time()) + 1
+        for i in range(2):
+            blocks_h2.append(create_block(tips[i], create_coinbase(2), block_time))
+            blocks_h2[i].solve()
+            block_time += 1
+        test_node.send_message(msg_block(blocks_h2[0]))
+        white_node.send_message(msg_block(blocks_h2[1]))
+
+        [ x.sync_with_ping() for x in [test_node, white_node] ]
+        assert_equal(self.nodes[0].getblockcount(), 2)
+        assert_equal(self.nodes[1].getblockcount(), 2)
+        self.log.info("First height 2 block accepted by both nodes")
+
+        # 3. Send another block that builds on the original tip.
+        blocks_h2f = []  # Blocks at height 2 that fork off the main chain
+        for i in range(2):
+            blocks_h2f.append(create_block(tips[i], create_coinbase(2), blocks_h2[i].nTime+1))
+            blocks_h2f[i].solve()
+        test_node.send_message(msg_block(blocks_h2f[0]))
+        white_node.send_message(msg_block(blocks_h2f[1]))
+
+        [ x.sync_with_ping() for x in [test_node, white_node] ]
+        for x in self.nodes[0].getchaintips():
+            if x['hash'] == blocks_h2f[0].hash:
+                assert_equal(x['status'], "headers-only")
+
+        for x in self.nodes[1].getchaintips():
+            if x['hash'] == blocks_h2f[1].hash:
+                assert_equal(x['status'], "valid-headers")
+
+        self.log.info("Second height 2 block accepted only from whitelisted peer")
+
+        # 4. Now send another block that builds on the forking chain.
+        blocks_h3 = []
+        for i in range(2):
+            blocks_h3.append(create_block(blocks_h2f[i].sha256, create_coinbase(3), blocks_h2f[i].nTime+1))
+            blocks_h3[i].solve()
+        test_node.send_message(msg_block(blocks_h3[0]))
+        white_node.send_message(msg_block(blocks_h3[1]))
+
+        [ x.sync_with_ping() for x in [test_node, white_node] ]
+        # Since the earlier block was not processed by node0, the new block
+        # can't be fully validated.
+        for x in self.nodes[0].getchaintips():
+            if x['hash'] == blocks_h3[0].hash:
+                assert_equal(x['status'], "headers-only")
+
+        # But this block should be accepted by node0 since it has more work.
+        self.nodes[0].getblock(blocks_h3[0].hash)
+        self.log.info("Unrequested more-work block accepted from non-whitelisted peer")
+
+        # Node1 should have accepted and reorged.
+        assert_equal(self.nodes[1].getblockcount(), 3)
+        self.log.info("Successfully reorged to length 3 chain from whitelisted peer")
+
+        # 4b. Now mine 288 more blocks and deliver; all should be processed but
+        # the last (height-too-high) on node0.  Node1 should process the tip if
+        # we give it the headers chain leading to the tip.
+        tips = blocks_h3
+        headers_message = msg_headers()
+        all_blocks = []   # node0's blocks
+        for j in range(2):
+            for i in range(288):
+                next_block = create_block(tips[j].sha256, create_coinbase(i + 4), tips[j].nTime+1)
+                next_block.solve()
+                if j==0:
+                    test_node.send_message(msg_block(next_block))
+                    all_blocks.append(next_block)
+                else:
+                    headers_message.headers.append(CBlockHeader(next_block))
+                tips[j] = next_block
+
+        time.sleep(2)
+        # Blocks 1-287 should be accepted, block 288 should be ignored because it's too far ahead
+        for x in all_blocks[:-1]:
+            self.nodes[0].getblock(x.hash)
+        assert_raises_jsonrpc(-1, "Block not found on disk", self.nodes[0].getblock, all_blocks[-1].hash)
+
+        headers_message.headers.pop() # Ensure the last block is unrequested
+        white_node.send_message(headers_message) # Send headers leading to tip
+        white_node.send_message(msg_block(tips[1]))  # Now deliver the tip
+        white_node.sync_with_ping()
+        self.nodes[1].getblock(tips[1].hash)
+        self.log.info("Unrequested block far ahead of tip accepted from whitelisted peer")
+
+        # 5. Test handling of unrequested block on the node that didn't process
+        # Should still not be processed (even though it has a child that has more
+        # work).
+        test_node.send_message(msg_block(blocks_h2f[0]))
+
+        # Here, if the sleep is too short, the test could falsely succeed (if the
+        # node hasn't processed the block by the time the sleep returns, and then
+        # the node processes it and incorrectly advances the tip).
+        # But this would be caught later on, when we verify that an inv triggers
+        # a getdata request for this block.
+        test_node.sync_with_ping()
+        assert_equal(self.nodes[0].getblockcount(), 2)
+        self.log.info("Unrequested block that would complete more-work chain was ignored")
+
+        # 6. Try to get node to request the missing block.
+        # Poke the node with an inv for block at height 3 and see if that
+        # triggers a getdata on block 2 (it should if block 2 is missing).
+        with mininode_lock:
+            # Clear state so we can check the getdata request
+            test_node.last_getdata = None
+            test_node.send_message(msg_inv([CInv(2, blocks_h3[0].sha256)]))
+
+        test_node.sync_with_ping()
+        with mininode_lock:
+            getdata = test_node.last_getdata
+
+        # Check that the getdata includes the right block
+        assert_equal(getdata.inv[0].hash, blocks_h2f[0].sha256)
+        self.log.info("Inv at tip triggered getdata for unprocessed block")
+
+        # 7. Send the missing block for the third time (now it is requested)
+        test_node.send_message(msg_block(blocks_h2f[0]))
+
+        test_node.sync_with_ping()
+        assert_equal(self.nodes[0].getblockcount(), 290)
+        self.log.info("Successfully reorged to longer chain from non-whitelisted peer")
+
+        [ c.disconnect_node() for c in connections ]
+
+if __name__ == '__main__':
+    AcceptBlockTest().main()