Implement roll-back limit for reorganisation

Closes #713.

qa/pull-tester/rpc-tests.sh

@@ -44,6 +44,7 @@ testScripts=(
     'zcjoinsplit.py'
     'zcjoinsplitdoublespend.py'
     'zkey_import_export.py'
+    'reorg_limit.py'
     'getblocktemplate.py'
     'bip65-cltv-p2p.py'
     'bipdersig-p2p.py'

qa/rpc-tests/reorg_limit.py

@@ -0,0 +1,86 @@
+#!/usr/bin/env python2
+# Copyright (c) 2017 The Zcash developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#
+# Test reorg limit
+#
+
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import (
+    check_node,
+    connect_nodes_bi,
+    initialize_chain_clean,
+    start_node,
+    sync_blocks,
+)
+from time import sleep
+
+def check_stopped(i, timeout=10):
+    stopped = False
+    for x in xrange(1, timeout):
+        ret = check_node(i)
+        if ret is None:
+            sleep(1)
+        else:
+            stopped = True
+            break
+    return stopped
+
+class ReorgLimitTest(BitcoinTestFramework):
+
+    def run_test(self):
+        assert(self.nodes[0].getblockcount() == 200)
+        assert(self.nodes[2].getblockcount() == 200)
+
+        self.split_network()
+
+        print "Test the maximum-allowed reorg:"
+        print "Mine 99 blocks on Node 0"
+        self.nodes[0].generate(99)
+        assert(self.nodes[0].getblockcount() == 299)
+        assert(self.nodes[2].getblockcount() == 200)
+
+        print "Mine competing 100 blocks on Node 2"
+        self.nodes[2].generate(100)
+        assert(self.nodes[0].getblockcount() == 299)
+        assert(self.nodes[2].getblockcount() == 300)
+
+        print "Connect nodes to force a reorg"
+        connect_nodes_bi(self.nodes, 0, 2)
+        self.is_network_split = False
+        sync_blocks(self.nodes)
+
+        print "Check Node 0 is still running and on the correct chain"
+        assert(self.nodes[0].getblockcount() == 300)
+
+        self.split_network()
+
+        print "Test the minimum-rejected reorg:"
+        print "Mine 100 blocks on Node 0"
+        self.nodes[0].generate(100)
+        assert(self.nodes[0].getblockcount() == 400)
+        assert(self.nodes[2].getblockcount() == 300)
+
+        print "Mine competing 101 blocks on Node 2"
+        self.nodes[2].generate(101)
+        assert(self.nodes[0].getblockcount() == 400)
+        assert(self.nodes[2].getblockcount() == 401)
+
+        print "Sync nodes to force a reorg"
+        connect_nodes_bi(self.nodes, 0, 2)
+        self.is_network_split = False
+        # sync_blocks uses RPC calls to wait for nodes to be synced, so don't
+        # call it here, because it will have a non-specific connection error
+        # when Node 0 stops. Instead, we explicitly check for the process itself
+        # to stop.
+
+        print "Check Node 0 is no longer running"
+        assert(check_stopped(0))
+
+        # Dummy stop to enable the test to tear down
+        self.nodes[0].stop = lambda: True
+
+if __name__ == '__main__':
+    ReorgLimitTest().main()

qa/rpc-tests/test_framework/util.py

@@ -213,6 +213,10 @@ def start_nodes(num_nodes, dirname, extra_args=None, rpchost=None, binary=None):
 def log_filename(dirname, n_node, logname):
     return os.path.join(dirname, "node"+str(n_node), "regtest", logname)
 
+def check_node(i):
+    bitcoind_processes[i].poll()
+    return bitcoind_processes[i].returncode
+
 def stop_node(node, i):
     node.stop()
     bitcoind_processes[i].wait()