nlr

src/chainparams.cpp

@@ -139,6 +139,7 @@ public:
         pchMessageStart[3] = 0xf1;
         nDefaultPort = 7312;
         nPruneAfterHeight = 100000;
+        nNlrLimit = 100; // 100 * ~40s = ~66 minutes
 
         genesis = CreateGenesisBlock(1371488396, 1000112548, 0x1e0ffff0, 1, 100 * COIN);
         consensus.hashGenesisBlock = genesis.GetHash();
@@ -275,6 +276,7 @@ public:
         pchMessageStart[3] = 0xf2;
         nDefaultPort = 17312;
         nPruneAfterHeight = 100000;
+        nNlrLimit = 50; // 50 * ~40s = ~33 minutes
 
         genesis = CreateGenesisBlock(1371387277, 1000580675, 0x1e0ffff0, 1, 100 * COIN);
         consensus.hashGenesisBlock = genesis.GetHash();
@@ -389,6 +391,7 @@ public:
         pchMessageStart[3] = 0xda;
         nDefaultPort = 17412;
         nPruneAfterHeight = 1000;
+        nNlrLimit = 10;
 
         genesis = CreateGenesisBlock(1371387277, 0, 0x207fffff, 1, 100 * COIN);
         consensus.hashGenesisBlock = genesis.GetHash();

src/chainparams.h

@@ -63,6 +63,7 @@ public:
     const Consensus::Params& GetConsensus() const { return consensus; }
     const CMessageHeader::MessageStartChars& MessageStart() const { return pchMessageStart; }
     int GetDefaultPort() const { return nDefaultPort; }
+    int NoLargeReorgLimit() const { return nNlrLimit; }
 
     const CBlock& GenesisBlock() const { return genesis; }
     /** Default value for -checkmempool and -checkblockindex argument */
@@ -87,6 +88,7 @@ protected:
     CMessageHeader::MessageStartChars pchMessageStart;
     int nDefaultPort;
     uint64_t nPruneAfterHeight;
+    int nNlrLimit;
     std::vector<CDNSSeedData> vSeeds;
     std::vector<unsigned char> base58Prefixes[MAX_BASE58_TYPES];
     std::string strNetworkID;

src/init.cpp

@@ -401,6 +401,7 @@ std::string HelpMessage(HelpMessageMode mode)
     strUsage += HelpMessageOpt("-maxreceivebuffer=<n>", strprintf(_("Maximum per-connection receive buffer, <n>*1000 bytes (default: %u)"), DEFAULT_MAXRECEIVEBUFFER));
     strUsage += HelpMessageOpt("-maxsendbuffer=<n>", strprintf(_("Maximum per-connection send buffer, <n>*1000 bytes (default: %u)"), DEFAULT_MAXSENDBUFFER));
     strUsage += HelpMessageOpt("-maxtimeadjustment", strprintf(_("Maximum allowed median peer time offset adjustment. Local perspective of time may be influenced by peers forward or backward by this amount. (default: %u seconds)"), DEFAULT_MAX_TIME_ADJUSTMENT));
+    strUsage += HelpMessageOpt("-nlrlimit=<n>", strprintf(_("Set the limit to be considered a large reorg, -nlrlimit=0 to disable NLR mode (default: %u)"), defaultChainParams->NoLargeReorgLimit()));
     strUsage += HelpMessageOpt("-onion=<ip:port>", strprintf(_("Use separate SOCKS5 proxy to reach peers via Tor hidden services (default: %s)"), "-proxy"));
     strUsage += HelpMessageOpt("-onlynet=<net>", _("Only connect to nodes in network <net> (ipv4, ipv6 or onion)"));
     strUsage += HelpMessageOpt("-permitbaremultisig", strprintf(_("Relay non-P2SH multisig (default: %u)"), DEFAULT_PERMIT_BAREMULTISIG));

src/rpc/blockchain.cpp

@@ -1457,7 +1457,7 @@ UniValue reconsiderblock(const JSONRPCRequest& request)
     }
 
     CValidationState state;
-    ActivateBestChain(state, Params());
+    ActivateBestChain(state, Params(), std::shared_ptr<const CBlock>(), true);
 
     if (!state.IsValid()) {
         throw JSONRPCError(RPC_DATABASE_ERROR, state.GetRejectReason());

src/validation.cpp

@@ -2313,12 +2313,42 @@ static void PruneBlockIndexCandidates() {
  * Try to make some progress towards making pindexMostWork the active block.
  * pblock is either nullptr or a pointer to a CBlock corresponding to pindexMostWork.
  */
-static bool ActivateBestChainStep(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexMostWork, const std::shared_ptr<const CBlock>& pblock, bool& fInvalidFound, ConnectTrace& connectTrace)
+static bool ActivateBestChainStep(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexMostWork, const std::shared_ptr<const CBlock>& pblock, bool& fInvalidFound, ConnectTrace& connectTrace, bool reconsider)
 {
     AssertLockHeld(cs_main);
     const CBlockIndex *pindexOldTip = chainActive.Tip();
     const CBlockIndex *pindexFork = chainActive.FindFork(pindexMostWork);
 
+    int nNlrLimit = gArgs.GetArg("-nlrlimit", Params().NoLargeReorgLimit());
+    if (nNlrLimit != 0 && !reconsider && !IsInitialBlockDownload() && pindexFork != nullptr
+        && chainActive.Tip()->nHeight - pindexFork->nHeight >= nNlrLimit) {
+        LogPrintf("%s: NLR triggered! current height=%d current hash=%s | fork height=%d fork hash=%s\n", __func__,
+                  pindexOldTip->nHeight, pindexOldTip->GetBlockHash().ToString(), pindexMostWork->nHeight,
+                  pindexMostWork->GetBlockHash().ToString());
+        CBlockIndex *pindexWalk = pindexMostWork;
+
+        // mark invalid_child from tip of fork to second block of fork
+        while (pindexWalk->nHeight != pindexFork->nHeight+2) {
+            pindexWalk = pindexWalk->pprev;
+            pindexWalk->nStatus |= BLOCK_FAILED_CHILD;
+            setDirtyBlockIndex.insert(pindexWalk);
+            setBlockIndexCandidates.erase(pindexWalk);
+        }
+
+        // mark invalid first block of fork
+        pindexWalk = pindexWalk->pprev;
+        pindexWalk->nStatus |= BLOCK_FAILED_VALID;
+        setDirtyBlockIndex.insert(pindexWalk);
+        setBlockIndexCandidates.erase(pindexWalk);
+
+        // sanity check
+        assert(pindexWalk->pprev == pindexFork);
+
+        fInvalidFound = true;
+        InvalidChainFound(pindexMostWork);
+        return true;
+    }
+
     // Disconnect active blocks which are no longer in the best chain.
     bool fBlocksDisconnected = false;
     DisconnectedBlockTransactions disconnectpool;
@@ -2420,7 +2450,7 @@ static void NotifyHeaderTip() {
  * or an activated best chain. pblock is either nullptr or a pointer to a block
  * that is already loaded (to avoid loading it again from disk).
  */
-bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams, std::shared_ptr<const CBlock> pblock) {
+bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams, std::shared_ptr<const CBlock> pblock, bool reconsider) {
     // Note that while we're often called here from ProcessNewBlock, this is
     // far from a guarantee. Things in the P2P/RPC will often end up calling
     // us in the middle of ProcessNewBlock - do not assume pblock is set
@@ -2451,7 +2481,7 @@ bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams,
 
             bool fInvalidFound = false;
             std::shared_ptr<const CBlock> nullBlockPtr;
-            if (!ActivateBestChainStep(state, chainparams, pindexMostWork, pblock && pblock->GetHash() == pindexMostWork->GetBlockHash() ? pblock : nullBlockPtr, fInvalidFound, connectTrace))
+            if (!ActivateBestChainStep(state, chainparams, pindexMostWork, pblock && pblock->GetHash() == pindexMostWork->GetBlockHash() ? pblock : nullBlockPtr, fInvalidFound, connectTrace, reconsider))
                 return false;
 
             if (fInvalidFound) {

src/validation.h

@@ -273,7 +273,7 @@ bool IsInitialBlockDownload();
 /** Retrieve a transaction (from memory pool, or from disk, if possible) */
 bool GetTransaction(const uint256 &hash, CTransactionRef &tx, const Consensus::Params& params, uint256 &hashBlock, bool fAllowSlow = false);
 /** Find the best known block, and make it the tip of the block chain */
-bool ActivateBestChain(CValidationState& state, const CChainParams& chainparams, std::shared_ptr<const CBlock> pblock = std::shared_ptr<const CBlock>());
+bool ActivateBestChain(CValidationState& state, const CChainParams& chainparams, std::shared_ptr<const CBlock> pblock = std::shared_ptr<const CBlock>(), bool reconsider=false);
 CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams);
 
 /** Guess verification progress (as a fraction between 0.0=genesis and 1.0=current tip). */

test/functional/nlr.py

@@ -0,0 +1,105 @@
+#!/usr/bin/env python3
+# Copyright (c) 2014-2016 The Bitcoin Core developers
+# Copyright (c) Flo Developers 2013-2018
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Test the getchaintips RPC.
+
+- introduce a network split
+- work on chains of different lengths
+- join the network together again
+- verify that getchaintips now returns two chain tips.
+"""
+
+import time
+
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_equal
+
+class GetChainTipsTest (BitcoinTestFramework):
+    def __init__(self):
+        super().__init__()
+        self.num_nodes = 4
+        self.extra_args = [['-nlrlimit=0'], ['-nlrlimit=10'], ['-nlrlimit=10'], ['-nlrlimit=10']]
+        self.setup_clean_chain = False
+
+    def run_test (self):
+
+        tips = self.nodes[0].getchaintips ()
+        assert_equal (len (tips), 1)
+        assert_equal (tips[0]['branchlen'], 0)
+        assert_equal (tips[0]['height'], 200)
+        assert_equal (tips[0]['status'], 'active')
+
+        # Split the network and build two chains of different lengths.
+        self.split_network()
+        self.nodes[0].generate(10)
+        self.nodes[2].generate(20)
+        self.sync_all([self.nodes[:2], self.nodes[2:]])
+
+        tips = self.nodes[1].getchaintips ()
+        assert_equal (len (tips), 1)
+        shortTip = tips[0]
+        assert_equal(shortTip['branchlen'], 0)
+        assert_equal(shortTip['height'], 210)
+        assert_equal(tips[0]['status'], 'active')
+
+        tips = self.nodes[3].getchaintips ()
+        assert_equal (len (tips), 1)
+        longTip = tips[0]
+        assert_equal (longTip['branchlen'], 0)
+        assert_equal (longTip['height'], 220)
+        assert_equal (tips[0]['status'], 'active')
+
+        # Join the network halves and check that we now have two tips
+        # (at least at the nodes that previously had the short chain).
+        print("pre join")
+        self.join_network_no_sync ()
+        time.sleep(10)
+        print("post join")
+
+        print("node 0")
+        print(self.nodes[0].getchaintips())
+        print("node 1")
+        print(self.nodes[1].getchaintips())
+        print("node 2")
+        print(self.nodes[2].getchaintips())
+
+        print("reconsider")
+        self.nodes[1].reconsiderblock(self.nodes[2].getbestblockhash())
+        self.sync_all()
+
+        print("node 0")
+        print(self.nodes[0].getchaintips ())
+        print("node 1")
+        print(self.nodes[1].getchaintips ())
+        print("node 2")
+        print(self.nodes[2].getchaintips ())
+        self.nodes[2].generate(20)
+
+        self.sync_all()
+        self.nodes[1].generate(20)
+
+        self.sync_all()
+
+        print("node 0")
+        print(self.nodes[0].getchaintips ())
+        print("node 1")
+        print(self.nodes[1].getchaintips ())
+        print("node 2")
+        print(self.nodes[2].getchaintips ())
+
+        # tips = self.nodes[1].getchaintips ()
+        # assert_equal (len (tips), 2)
+        # assert_equal (tips[0], longTip)
+        #
+        # assert_equal (tips[1]['branchlen'], 10)
+        # assert_equal (tips[1]['status'], 'valid-fork')
+        # tips[1]['branchlen'] = 0
+        # tips[1]['status'] = 'active'
+        # assert_equal (tips[1], shortTip)
+
+        assert_equal(1, 3)
+
+if __name__ == '__main__':
+    GetChainTipsTest().main()

test/functional/test_framework/test_framework.py

@@ -310,6 +310,12 @@ class BitcoinTestFramework(object):
         connect_nodes_bi(self.nodes, 1, 2)
         self.sync_all()
 
+    def join_network_no_sync(self):
+        """
+        Join the (previously split) network halves together. Do not wait sync.
+        """
+        connect_nodes_bi(self.nodes, 1, 2)
+
     def sync_all(self, node_groups=None):
         if not node_groups:
             node_groups = [self.nodes]