Merge AuxPoW support from Namecore

Changes are as below:

Wrap CBlockHeader::nVersion into a new class (CBlockVersion).  This allows to take care of interpreting the field into a base version, auxpow flag and the chain ID.

Update getauxblock.py for new 'generate' RPC call.

Add 'auxpow' to block JSON.

Accept auxpow as PoW verification.

Add unit tests for auxpow verification.

Add check for memory-layout of CBlockVersion.

Weaken auxpow chain ID checks for the testnet.

Allow Params() to overrule when to check the auxpow chain ID and for legacy blocks.  Use this to disable the checks on testnet.

Introduce CPureBlockHeader.

Split the block header part that is used by auxpow and the "real" block header (that uses auxpow) to resolve the cyclic dependency between the two.

Differentiate between uint256 and arith_uint256.

This change was done upstream, modify the auxpow code.

Add missing lock in auxpow_tests.

Fix REST header check for auxpow headers.

Those can be longer, thus take that into account.  Also perform the check actually on an auxpow header.

Correctly set the coinbase for getauxblock results.

Call IncrementExtraNonce in getauxblock so that the coinbase is actually initialised with the stuff it should be.  (BIP30 block height and COINBASE_FLAGS.)

Implement getauxblock plus regression test.

Turn auxpow test into FIXTURE test.

This allows using of the Params() calls.

Move CMerkleTx code to auxpow.cpp.

Otherwise we get linker errors when building without wallet.

Fix rebase with BIP66.

Update the code to handle BIP66's nVersion=3.

Enforce that auxpow parent blocks have no auxpow block version.

This is for compatibility with namecoind.  See also https://github.com/namecoin/namecoin/pull/199.

Move auxpow-related parameters to Consensus::Params.

1 files changed, 264 insertions, 3 deletions

diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index 33e234a95..70192686b 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -121,14 +121,16 @@ UniValue generateBlocks(boost::shared_ptr<CReserveScript> coinbaseScript, int nG
             LOCK(cs_main);
             IncrementExtraNonce(pblock, chainActive.Tip(), nExtraNonce);
         }
-        while (nMaxTries > 0 && pblock->nNonce < nInnerLoopCount && !CheckProofOfWork(pblock->GetHash(), pblock->nBits, Params().GetConsensus())) {
-            ++pblock->nNonce;
+        CAuxPow::initAuxPow(*pblock);
+        CPureBlockHeader& miningHeader = pblock->auxpow->parentBlock;
+        while (nMaxTries > 0 && miningHeader.nNonce < nInnerLoopCount && !CheckProofOfWork(miningHeader.GetHash(), pblock->nBits, Params().GetConsensus())) {
+            ++miningHeader.nNonce;
             --nMaxTries;
         }
         if (nMaxTries == 0) {
             break;
         }
-        if (pblock->nNonce == nInnerLoopCount) {
+        if (miningHeader.nNonce == nInnerLoopCount) {
             continue;
         }
         std::shared_ptr<const CBlock> shared_pblock = std::make_shared<const CBlock>(*pblock);
@@ -925,6 +927,262 @@ UniValue estimatesmartpriority(const JSONRPCRequest& request)
     return result;
 }
 
+/* ************************************************************************** */
+/* Merge mining.  */
+
+/**
+ * The variables below are used to keep track of created and not yet
+ * submitted auxpow blocks.  Lock them to be sure even for multiple
+ * RPC threads running in parallel.
+ */
+static CCriticalSection cs_auxblockCache;
+static std::map<uint256, CBlock*> mapNewBlock;
+static std::vector<std::unique_ptr<CBlockTemplate>> vNewBlockTemplate;
+
+static
+void AuxMiningCheck()
+{
+  if(!g_connman)
+    throw JSONRPCError(RPC_CLIENT_P2P_DISABLED,
+                       "Error: Peer-to-peer functionality missing or disabled");
+
+  if (g_connman->GetNodeCount(CConnman::CONNECTIONS_ALL) == 0
+        && !Params().MineBlocksOnDemand())
+    throw JSONRPCError(RPC_CLIENT_NOT_CONNECTED,
+                       "Dogecoin is not connected!");
+
+  if (IsInitialBlockDownload() && !Params().MineBlocksOnDemand())
+    throw JSONRPCError(RPC_CLIENT_IN_INITIAL_DOWNLOAD,
+                       "Dogecoin is downloading blocks...");
+
+  /* This should never fail, since the chain is already
+     past the point of merge-mining start.  Check nevertheless.  */
+  {
+    LOCK(cs_main);
+    if (chainActive.Height() + 1 < Params().GetConsensus().nAuxpowStartHeight)
+      throw std::runtime_error("mining auxblock method is not yet available");
+  }
+}
+
+static
+UniValue AuxMiningCreateBlock(const CScript& scriptPubKey)
+{
+    AuxMiningCheck();
+
+    LOCK(cs_auxblockCache);
+
+    static unsigned nTransactionsUpdatedLast;
+    static const CBlockIndex* pindexPrev = nullptr;
+    static uint64_t nStart;
+    static CBlock* pblock = nullptr;
+    static unsigned nExtraNonce = 0;
+
+    // Update block
+    {
+    LOCK(cs_main);
+    if (pindexPrev != chainActive.Tip()
+        || (mempool.GetTransactionsUpdated() != nTransactionsUpdatedLast
+            && GetTime() - nStart > 60))
+    {
+        if (pindexPrev != chainActive.Tip())
+        {
+            // Clear old blocks since they're obsolete now.
+            mapNewBlock.clear();
+            vNewBlockTemplate.clear();
+            pblock = nullptr;
+        }
+
+        // Create new block with nonce = 0 and extraNonce = 1
+        std::unique_ptr<CBlockTemplate> newBlock
+            = BlockAssembler(Params()).CreateNewBlock(scriptPubKey);
+        if (!newBlock)
+            throw JSONRPCError(RPC_OUT_OF_MEMORY, "out of memory");
+
+        // Update state only when CreateNewBlock succeeded
+        nTransactionsUpdatedLast = mempool.GetTransactionsUpdated();
+        pindexPrev = chainActive.Tip();
+        nStart = GetTime();
+
+        // Finalise it by setting the version and building the merkle root
+        IncrementExtraNonce(&newBlock->block, pindexPrev, nExtraNonce);
+        newBlock->block.SetAuxpowFlag(true);
+
+        // Save
+        pblock = &newBlock->block;
+        mapNewBlock[pblock->GetHash()] = pblock;
+        vNewBlockTemplate.push_back(std::move(newBlock));
+    }
+    }
+
+    // At this point, pblock is always initialised:  If we make it here
+    // without creating a new block above, it means that, in particular,
+    // pindexPrev == chainActive.Tip().  But for that to happen, we must
+    // already have created a pblock in a previous call, as pindexPrev is
+    // initialised only when pblock is.
+    assert(pblock);
+
+    arith_uint256 target;
+    bool fNegative, fOverflow;
+    target.SetCompact(pblock->nBits, &fNegative, &fOverflow);
+    if (fNegative || fOverflow || target == 0)
+        throw std::runtime_error("invalid difficulty bits in block");
+
+    UniValue result(UniValue::VOBJ);
+    result.pushKV("hash", pblock->GetHash().GetHex());
+    result.pushKV("chainid", pblock->GetChainId());
+    result.pushKV("previousblockhash", pblock->hashPrevBlock.GetHex());
+    result.pushKV("coinbasevalue", (int64_t)pblock->vtx[0]->vout[0].nValue);
+    result.pushKV("bits", strprintf("%08x", pblock->nBits));
+    result.pushKV("height", static_cast<int64_t> (pindexPrev->nHeight + 1));
+    result.pushKV("_target", HexStr(BEGIN(target), END(target)));
+
+    return result;
+}
+
+static
+bool AuxMiningSubmitBlock(const std::string& hashHex,
+                          const std::string& auxpowHex)
+{
+    AuxMiningCheck();
+
+    LOCK(cs_auxblockCache);
+
+    uint256 hash;
+    hash.SetHex(hashHex);
+
+    const std::map<uint256, CBlock*>::iterator mit = mapNewBlock.find(hash);
+    if (mit == mapNewBlock.end())
+        throw JSONRPCError(RPC_INVALID_PARAMETER, "block hash unknown");
+    CBlock& block = *mit->second;
+
+    const std::vector<unsigned char> vchAuxPow = ParseHex(auxpowHex);
+    CDataStream ss(vchAuxPow, SER_GETHASH, PROTOCOL_VERSION);
+    CAuxPow pow;
+    ss >> pow;
+    block.SetAuxpow(new CAuxPow(pow));
+    assert(block.GetHash() == hash);
+
+    submitblock_StateCatcher sc(block.GetHash());
+    RegisterValidationInterface(&sc);
+    std::shared_ptr<const CBlock> shared_block
+      = std::make_shared<const CBlock>(block);
+    bool fAccepted = ProcessNewBlock(Params(), shared_block, true, nullptr);
+    UnregisterValidationInterface(&sc);
+
+    return fAccepted;
+}
+
+UniValue getauxblock(const JSONRPCRequest& request)
+{
+    if (request.fHelp
+          || (request.params.size() != 0 && request.params.size() != 2))
+        throw std::runtime_error(
+            "getauxblock (hash auxpow)\n"
+            "\nCreate or submit a merge-mined block.\n"
+            "\nWithout arguments, create a new block and return information\n"
+            "required to merge-mine it.  With arguments, submit a solved\n"
+            "auxpow for a previously returned block.\n"
+            "\nArguments:\n"
+            "1. hash      (string, optional) hash of the block to submit\n"
+            "2. auxpow    (string, optional) serialised auxpow found\n"
+            "\nResult (without arguments):\n"
+            "{\n"
+            "  \"hash\"               (string) hash of the created block\n"
+            "  \"chainid\"            (numeric) chain ID for this block\n"
+            "  \"previousblockhash\"  (string) hash of the previous block\n"
+            "  \"coinbasevalue\"      (numeric) value of the block's coinbase\n"
+            "  \"bits\"               (string) compressed target of the block\n"
+            "  \"height\"             (numeric) height of the block\n"
+            "  \"_target\"            (string) target in reversed byte order, deprecated\n"
+            "}\n"
+            "\nResult (with arguments):\n"
+            "xxxxx        (boolean) whether the submitted block was correct\n"
+            "\nExamples:\n"
+            + HelpExampleCli("getauxblock", "")
+            + HelpExampleCli("getauxblock", "\"hash\" \"serialised auxpow\"")
+            + HelpExampleRpc("getauxblock", "")
+            );
+
+    boost::shared_ptr<CReserveScript> coinbaseScript;
+    GetMainSignals().ScriptForMining(coinbaseScript);
+
+    // If the keypool is exhausted, no script is returned at all.  Catch this.
+    if (!coinbaseScript)
+        throw JSONRPCError(RPC_WALLET_KEYPOOL_RAN_OUT, "Error: Keypool ran out, please call keypoolrefill first");
+
+    //throw an error if no script was provided
+    if (!coinbaseScript->reserveScript.size())
+        throw JSONRPCError(RPC_INTERNAL_ERROR, "No coinbase script available (mining requires a wallet)");
+
+    /* Create a new block */
+    if (request.params.size() == 0)
+        return AuxMiningCreateBlock(coinbaseScript->reserveScript);
+
+    /* Submit a block instead.  Note that this need not lock cs_main,
+       since ProcessNewBlock below locks it instead.  */
+    assert(request.params.size() == 2);
+    bool fAccepted = AuxMiningSubmitBlock(request.params[0].get_str(),
+                                          request.params[1].get_str());
+    if (fAccepted)
+        coinbaseScript->KeepScript();
+
+    return fAccepted;
+}
+
+UniValue createauxblock(const JSONRPCRequest& request)
+{
+    if (request.fHelp || request.params.size() != 1)
+        throw std::runtime_error(
+            "createauxblock <address>\n"
+            "\ncreate a new block and return information required to merge-mine it.\n"
+            "\nArguments:\n"
+            "1. address      (string, required) specify coinbase transaction payout address\n"
+            "\nResult:\n"
+            "{\n"
+            "  \"hash\"               (string) hash of the created block\n"
+            "  \"chainid\"            (numeric) chain ID for this block\n"
+            "  \"previousblockhash\"  (string) hash of the previous block\n"
+            "  \"coinbasevalue\"      (numeric) value of the block's coinbase\n"
+            "  \"bits\"               (string) compressed target of the block\n"
+            "  \"height\"             (numeric) height of the block\n"
+            "  \"_target\"            (string) target in reversed byte order, deprecated\n"
+            "}\n"
+            "\nExamples:\n"
+            + HelpExampleCli("createauxblock", "\"address\"")
+            + HelpExampleRpc("createauxblock", "\"address\"")
+            );
+
+    // Check coinbase payout address
+    CBitcoinAddress coinbaseAddress(request.params[0].get_str());
+    if (!coinbaseAddress.IsValid())
+        throw JSONRPCError(RPC_INVALID_PARAMETER,
+                           "Invalid coinbase payout address");
+    const CScript scriptPubKey
+        = GetScriptForDestination(coinbaseAddress.Get());
+
+    return AuxMiningCreateBlock(scriptPubKey);
+}
+
+UniValue submitauxblock(const JSONRPCRequest& request)
+{
+    if (request.fHelp || request.params.size() != 2)
+        throw std::runtime_error(
+            "submitauxblock <hash> <auxpow>\n"
+            "\nsubmit a solved auxpow for a previously block created by 'createauxblock'.\n"
+            "\nArguments:\n"
+            "1. hash      (string, required) hash of the block to submit\n"
+            "2. auxpow    (string, required) serialised auxpow found\n"
+            "\nResult:\n"
+            "xxxxx        (boolean) whether the submitted block was correct\n"
+            "\nExamples:\n"
+            + HelpExampleCli("submitauxblock", "\"hash\" \"serialised auxpow\"")
+            + HelpExampleRpc("submitauxblock", "\"hash\" \"serialised auxpow\"")
+            );
+
+    return AuxMiningSubmitBlock(request.params[0].get_str(),
+                                request.params[1].get_str());
+}
+
 static const CRPCCommand commands[] =
 { //  category              name                      actor (function)         okSafeMode
   //  --------------------- ------------------------  -----------------------  ----------
@@ -933,6 +1191,9 @@ static const CRPCCommand commands[] =
     { "mining",             "prioritisetransaction",  &prioritisetransaction,  true,  {"txid","priority_delta","fee_delta"} },
     { "mining",             "getblocktemplate",       &getblocktemplate,       true,  {"template_request"} },
     { "mining",             "submitblock",            &submitblock,            true,  {"hexdata","parameters"} },
+    { "mining",             "getauxblock",            &getauxblock,            true,  {"hash", "auxpow"} },
+    { "mining",             "createauxblock",         &createauxblock,         true,  {"address"} },
+    { "mining",             "submitauxblock",         &submitauxblock,         true,  {"hash", "auxpow"} },
 
     { "generating",         "generate",               &generate,               true,  {"nblocks","maxtries"} },
     { "generating",         "generatetoaddress",      &generatetoaddress,      true,  {"nblocks","address","maxtries"} },