Merge #6996: Add preciousblock RPC

5805ac8 Add preciousblock tests (Pieter Wuille)
5127c4f Add preciousblock RPC (Pieter Wuille)

7 files changed, 207 insertions, 3 deletions

diff --git a/qa/pull-tester/rpc-tests.py b/qa/pull-tester/rpc-tests.py
index 4a953385e0..7430bb2256 100755
--- a/qa/pull-tester/rpc-tests.py
+++ b/qa/pull-tester/rpc-tests.py
@@ -140,6 +140,7 @@ testScripts = [
     'invalidtxrequest.py',
     'abandonconflict.py',
     'p2p-versionbits-warning.py',
+    'preciousblock.py',
     'importprunedfunds.py',
     'signmessages.py',
     'p2p-compactblocks.py',
diff --git a/qa/rpc-tests/preciousblock.py b/qa/rpc-tests/preciousblock.py
new file mode 100755
index 0000000000..854dcc7251
--- /dev/null
+++ b/qa/rpc-tests/preciousblock.py
@@ -0,0 +1,116 @@
+#!/usr/bin/env python3
+# Copyright (c) 2015 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 PreciousBlock code
+#
+
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import *
+
+def unidirectional_node_sync_via_rpc(node_src, node_dest):
+    blocks_to_copy = []
+    blockhash = node_src.getbestblockhash()
+    while True:
+        try:
+            assert(len(node_dest.getblock(blockhash, False)) > 0)
+            break
+        except:
+            blocks_to_copy.append(blockhash)
+            blockhash = node_src.getblockheader(blockhash, True)['previousblockhash']
+    blocks_to_copy.reverse()
+    for blockhash in blocks_to_copy:
+        blockdata = node_src.getblock(blockhash, False)
+        assert(node_dest.submitblock(blockdata) in (None, 'inconclusive'))
+
+def node_sync_via_rpc(nodes):
+    for node_src in nodes:
+        for node_dest in nodes:
+            if node_src is node_dest:
+                continue
+            unidirectional_node_sync_via_rpc(node_src, node_dest)
+
+class PreciousTest(BitcoinTestFramework):
+    def setup_chain(self):
+        print("Initializing test directory "+self.options.tmpdir)
+        initialize_chain_clean(self.options.tmpdir, 3)
+
+    def setup_network(self):
+        self.nodes = []
+        self.is_network_split = False
+        self.nodes.append(start_node(0, self.options.tmpdir, ["-debug"]))
+        self.nodes.append(start_node(1, self.options.tmpdir, ["-debug"]))
+        self.nodes.append(start_node(2, self.options.tmpdir, ["-debug"]))
+
+    def run_test(self):
+        print("Ensure submitblock can in principle reorg to a competing chain")
+        self.nodes[0].generate(1)
+        assert(self.nodes[0].getblockcount() == 1)
+        (hashY, hashZ) = self.nodes[1].generate(2)
+        assert(self.nodes[1].getblockcount() == 2)
+        node_sync_via_rpc(self.nodes[0:3])
+        assert(self.nodes[0].getbestblockhash() == hashZ)
+
+        print("Mine blocks A-B-C on Node 0")
+        (hashA, hashB, hashC) = self.nodes[0].generate(3)
+        assert(self.nodes[0].getblockcount() == 5)
+        print("Mine competing blocks E-F-G on Node 1")
+        (hashE, hashF, hashG) = self.nodes[1].generate(3)
+        assert(self.nodes[1].getblockcount() == 5)
+        assert(hashC != hashG)
+        print("Connect nodes and check no reorg occurs")
+        # Submit competing blocks via RPC so any reorg should occur before we proceed (no way to wait on inaction for p2p sync)
+        node_sync_via_rpc(self.nodes[0:2])
+        connect_nodes_bi(self.nodes,0,1)
+        assert(self.nodes[0].getbestblockhash() == hashC)
+        assert(self.nodes[1].getbestblockhash() == hashG)
+        print("Make Node0 prefer block G")
+        self.nodes[0].preciousblock(hashG)
+        assert(self.nodes[0].getbestblockhash() == hashG)
+        print("Make Node0 prefer block C again")
+        self.nodes[0].preciousblock(hashC)
+        assert(self.nodes[0].getbestblockhash() == hashC)
+        print("Make Node1 prefer block C")
+        self.nodes[1].preciousblock(hashC)
+        sync_chain(self.nodes[0:2]) # wait because node 1 may not have downloaded hashC
+        assert(self.nodes[1].getbestblockhash() == hashC)
+        print("Make Node1 prefer block G again")
+        self.nodes[1].preciousblock(hashG)
+        assert(self.nodes[1].getbestblockhash() == hashG)
+        print("Make Node0 prefer block G again")
+        self.nodes[0].preciousblock(hashG)
+        assert(self.nodes[0].getbestblockhash() == hashG)
+        print("Make Node1 prefer block C again")
+        self.nodes[1].preciousblock(hashC)
+        assert(self.nodes[1].getbestblockhash() == hashC)
+        print("Mine another block (E-F-G-)H on Node 0 and reorg Node 1")
+        self.nodes[0].generate(1)
+        assert(self.nodes[0].getblockcount() == 6)
+        sync_blocks(self.nodes[0:2])
+        hashH = self.nodes[0].getbestblockhash()
+        assert(self.nodes[1].getbestblockhash() == hashH)
+        print("Node1 should not be able to prefer block C anymore")
+        self.nodes[1].preciousblock(hashC)
+        assert(self.nodes[1].getbestblockhash() == hashH)
+        print("Mine competing blocks I-J-K-L on Node 2")
+        self.nodes[2].generate(4)
+        assert(self.nodes[2].getblockcount() == 6)
+        hashL = self.nodes[2].getbestblockhash()
+        print("Connect nodes and check no reorg occurs")
+        node_sync_via_rpc(self.nodes[0:3])
+        connect_nodes_bi(self.nodes,1,2)
+        connect_nodes_bi(self.nodes,0,2)
+        assert(self.nodes[0].getbestblockhash() == hashH)
+        assert(self.nodes[1].getbestblockhash() == hashH)
+        assert(self.nodes[2].getbestblockhash() == hashL)
+        print("Make Node1 prefer block L")
+        self.nodes[1].preciousblock(hashL)
+        assert(self.nodes[1].getbestblockhash() == hashL)
+        print("Make Node2 prefer block H")
+        self.nodes[2].preciousblock(hashH)
+        assert(self.nodes[2].getbestblockhash() == hashH)
+
+if __name__ == '__main__':
+    PreciousTest().main()
diff --git a/qa/rpc-tests/test_framework/util.py b/qa/rpc-tests/test_framework/util.py
index c6b0367b41..c818af4bd7 100644
--- a/qa/rpc-tests/test_framework/util.py
+++ b/qa/rpc-tests/test_framework/util.py
@@ -137,6 +137,16 @@ def sync_blocks(rpc_connections, wait=1, timeout=60):
         maxheight = max(heights)
     raise AssertionError("Block sync failed")
 
+def sync_chain(rpc_connections, wait=1):
+    """
+    Wait until everybody has the same best block
+    """
+    while True:
+        counts = [ x.getbestblockhash() for x in rpc_connections ]
+        if counts == [ counts[0] ]*len(counts):
+            break
+        time.sleep(wait)
+
 def sync_mempools(rpc_connections, wait=1, timeout=60):
     """
     Wait until everybody has the same transactions in their memory
diff --git a/src/chain.h b/src/chain.h
index 6588e8f57d..e2f8c56522 100644
--- a/src/chain.h
+++ b/src/chain.h
@@ -200,7 +200,7 @@ public:
     unsigned int nNonce;
 
     //! (memory only) Sequential id assigned to distinguish order in which blocks are received.
-    uint32_t nSequenceId;
+    int32_t nSequenceId;
 
     void SetNull()
     {
diff --git a/src/main.cpp b/src/main.cpp
index 9f3116e358..cb3e771602 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -169,7 +169,11 @@ namespace {
      */
     CCriticalSection cs_nBlockSequenceId;
     /** Blocks loaded from disk are assigned id 0, so start the counter at 1. */
-    uint32_t nBlockSequenceId = 1;
+    int32_t nBlockSequenceId = 1;
+    /** Decreasing counter (used by subsequent preciousblock calls). */
+    int32_t nBlockReverseSequenceId = -1;
+    /** chainwork for the last block that preciousblock has been applied to. */
+    arith_uint256 nLastPreciousChainwork = 0;
 
     /**
      * Sources of received blocks, saved to be able to send them reject
@@ -3137,6 +3141,36 @@ bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams,
     return true;
 }
 
+
+bool PreciousBlock(CValidationState& state, const CChainParams& params, CBlockIndex *pindex)
+{
+    {
+        LOCK(cs_main);
+        if (pindex->nChainWork < chainActive.Tip()->nChainWork) {
+            // Nothing to do, this block is not at the tip.
+            return true;
+        }
+        if (chainActive.Tip()->nChainWork > nLastPreciousChainwork) {
+            // The chain has been extended since the last call, reset the counter.
+            nBlockReverseSequenceId = -1;
+        }
+        nLastPreciousChainwork = chainActive.Tip()->nChainWork;
+        setBlockIndexCandidates.erase(pindex);
+        pindex->nSequenceId = nBlockReverseSequenceId;
+        if (nBlockReverseSequenceId > std::numeric_limits<int32_t>::min()) {
+            // We can't keep reducing the counter if somebody really wants to
+            // call preciousblock 2**31-1 times on the same set of tips...
+            nBlockReverseSequenceId--;
+        }
+        if (pindex->IsValid(BLOCK_VALID_TRANSACTIONS) && pindex->nChainTx) {
+            setBlockIndexCandidates.insert(pindex);
+            PruneBlockIndexCandidates();
+        }
+    }
+
+    return ActivateBestChain(state, params);
+}
+
 bool InvalidateBlock(CValidationState& state, const CChainParams& chainparams, CBlockIndex *pindex)
 {
     AssertLockHeld(cs_main);
@@ -4531,7 +4565,7 @@ void static CheckBlockIndex(const Consensus::Params& consensusParams)
             assert(pindex->GetBlockHash() == consensusParams.hashGenesisBlock); // Genesis block's hash must match.
             assert(pindex == chainActive.Genesis()); // The current active chain's genesis block must be this block.
         }
-        if (pindex->nChainTx == 0) assert(pindex->nSequenceId == 0);  // nSequenceId can't be set for blocks that aren't linked
+        if (pindex->nChainTx == 0) assert(pindex->nSequenceId <= 0);  // nSequenceId can't be set positive for blocks that aren't linked (negative is used for preciousblock)
         // VALID_TRANSACTIONS is equivalent to nTx > 0 for all nodes (whether or not pruning has occurred).
         // HAVE_DATA is only equivalent to nTx > 0 (or VALID_TRANSACTIONS) if no pruning has occurred.
         if (!fHavePruned) {
diff --git a/src/main.h b/src/main.h
index db58b27487..49768f21c1 100644
--- a/src/main.h
+++ b/src/main.h
@@ -509,6 +509,9 @@ public:
 /** Find the last common block between the parameter chain and a locator. */
 CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator);
 
+/** Mark a block as precious and reorganize. */
+bool PreciousBlock(CValidationState& state, const CChainParams& params, CBlockIndex *pindex);
+
 /** Mark a block as invalid. */
 bool InvalidateBlock(CValidationState& state, const CChainParams& chainparams, CBlockIndex *pindex);
 
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 1e04fcc01c..1ca4a7c6d7 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -1251,6 +1251,44 @@ UniValue getmempoolinfo(const UniValue& params, bool fHelp)
     return mempoolInfoToJSON();
 }
 
+UniValue preciousblock(const UniValue& params, bool fHelp)
+{
+    if (fHelp || params.size() != 1)
+        throw runtime_error(
+            "preciousblock \"hash\"\n"
+            "\nTreats a block as if it were received before others with the same work.\n"
+            "\nA later preciousblock call can override the effect of an earlier one.\n"
+            "\nThe effects of preciousblock are not retained across restarts.\n"
+            "\nArguments:\n"
+            "1. hash   (string, required) the hash of the block to mark as precious\n"
+            "\nResult:\n"
+            "\nExamples:\n"
+            + HelpExampleCli("preciousblock", "\"blockhash\"")
+            + HelpExampleRpc("preciousblock", "\"blockhash\"")
+        );
+
+    std::string strHash = params[0].get_str();
+    uint256 hash(uint256S(strHash));
+    CBlockIndex* pblockindex;
+
+    {
+        LOCK(cs_main);
+        if (mapBlockIndex.count(hash) == 0)
+            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
+
+        pblockindex = mapBlockIndex[hash];
+    }
+
+    CValidationState state;
+    PreciousBlock(state, Params(), pblockindex);
+
+    if (!state.IsValid()) {
+        throw JSONRPCError(RPC_DATABASE_ERROR, state.GetRejectReason());
+    }
+
+    return NullUniValue;
+}
+
 UniValue invalidateblock(const UniValue& params, bool fHelp)
 {
     if (fHelp || params.size() != 1)
@@ -1346,6 +1384,8 @@ static const CRPCCommand commands[] =
     { "blockchain",         "gettxoutsetinfo",        &gettxoutsetinfo,        true  },
     { "blockchain",         "verifychain",            &verifychain,            true  },
 
+    { "blockchain",         "preciousblock",          &preciousblock,          true  },
+
     /* Not shown in help */
     { "hidden",             "invalidateblock",        &invalidateblock,        true  },
     { "hidden",             "reconsiderblock",        &reconsiderblock,        true  },