Merge AuxPoW support from Namecore

Includes the following commits:

commit 2ea1b5cd8cf2bdd08e43ae39fb76352eebe14895
commit f2a8220c34275f022f02d81e9e84d4cec33bd51c
commit 84b8b56113e6057b0253475b83e797dc1fed2eed
commit 8471d5db221f145f5a40022ed1897c1b996b628e
commit 2f125ad0a67e1b8f71b18a14a3b41d7e577391d1
commit e01dbc3608703b4cb4e9882738125f2b7816cdb8
commit f0421312631cd44669f9f84d339a0c470b4423b9
commit 1fd522db5dfddfd0e1b0c794b82fae2cc7bdb099
commit 71f63ad99f70ff6461c795fd728aea16aa1008f8
commit a7c44d98a8ded4df0e8455c4c5629b1a5b303bbf
commit e1d7b4fc15addf3dfeb3853fa66230a8bdacd75f
commit d016f2fa02572fd340129176b942b3f19bd5260b
commit f4716e5a168a697afce854a37350fdae0988bdd8
commit 03a575e3b13bf06cbb0a007d6672b05d2085c26e
commit d7ea37444bd9e9ac461a3dda0b16afefd160b062
commit db22affa01e050ff847a12e20c83b88952d80b59
commit 9b7e14986655f914b2d0903ca1d79367c92c6c7e
commit e21034f9c124893d5b9631e9ca231b0b9ede3d52

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, 178 insertions, 1 deletions

diff --git a/src/rpcmining.cpp b/src/rpcmining.cpp
index 528d5406f..3639ac931 100644
--- a/src/rpcmining.cpp
+++ b/src/rpcmining.cpp
@@ -30,6 +30,30 @@
 using namespace json_spirit;
 using namespace std;
 
+#ifdef ENABLE_WALLET
+// Key used by getwork miners.
+// Allocated in InitRPCMining, free'd in ShutdownRPCMining
+static CReserveKey* pminingKey = NULL;
+
+void InitRPCMining()
+{
+    if (!pwalletMain)
+        return;
+
+    // getwork/getblocktemplate mining rewards paid here:
+    pminingKey = new CReserveKey(pwalletMain);
+}
+
+void ShutdownRPCMining()
+{
+    if (!pminingKey)
+        return;
+
+    delete pminingKey;
+    pminingKey = NULL;
+}
+#endif // ENABLE_WALLET
+
 /**
  * Return average network hashes per second based on the last 'lookup' blocks,
  * or from the last difficulty change if 'lookup' is nonpositive.
@@ -569,7 +593,7 @@ Value getblocktemplate(const Array& params, bool fHelp)
 
     Object result;
     result.push_back(Pair("capabilities", aCaps));
-    result.push_back(Pair("version", pblock->nVersion));
+    result.push_back(Pair("version", pblock->nVersion.GetFullVersion()));
     result.push_back(Pair("previousblockhash", pblock->hashPrevBlock.GetHex()));
     result.push_back(Pair("transactions", transactions));
     result.push_back(Pair("coinbaseaux", aux));
@@ -726,3 +750,156 @@ Value estimatepriority(const Array& params, bool fHelp)
 
     return mempool.estimatePriority(nBlocks);
 }
+
+/* ************************************************************************** */
+/* Merge mining.  */
+
+#ifdef ENABLE_WALLET
+Value getauxblock(const Array& params, bool fHelp)
+{
+    if (fHelp || (params.size() != 0 && 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", "")
+            );
+
+    if (pwalletMain == NULL)
+        throw JSONRPCError(RPC_METHOD_NOT_FOUND, "Method not found (disabled)");
+    assert (pminingKey);
+
+    if (vNodes.empty() && !Params().MineBlocksOnDemand())
+        throw JSONRPCError(RPC_CLIENT_NOT_CONNECTED,
+                           "Namecoin is not connected!");
+
+    if (IsInitialBlockDownload() && !Params().MineBlocksOnDemand())
+        throw JSONRPCError(RPC_CLIENT_IN_INITIAL_DOWNLOAD,
+                           "Namecoin 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("getauxblock method is not yet available");
+    }
+
+    /* The variables below are used to keep track of created and not yet
+       submitted auxpow blocks.  Lock them, just in case.  In principle
+       there's only one RPC thread, so it should be fine without locking
+       as well.  But it cannot hurt to be safe.  */
+    static CCriticalSection cs_auxblockCache;
+    LOCK(cs_auxblockCache);
+    static std::map<uint256, CBlock*> mapNewBlock;
+    static std::vector<CBlockTemplate*> vNewBlockTemplate;
+
+    /* Create a new block?  */
+    if (params.size() == 0)
+    {
+        static unsigned nTransactionsUpdatedLast;
+        static const CBlockIndex* pindexPrev = NULL;
+        static uint64_t nStart;
+        static CBlockTemplate* pblocktemplate;
+        static unsigned nExtraNonce = 0;
+
+        // Update block
+        {
+        LOCK(cs_main);
+        if (pindexPrev != chainActive.Tip()
+            || (mempool.GetTransactionsUpdated() != nTransactionsUpdatedLast
+                && GetTime() - nStart > 60))
+        {
+            if (pindexPrev != chainActive.Tip())
+            {
+                // Deallocate old blocks since they're obsolete now
+                mapNewBlock.clear();
+                BOOST_FOREACH(CBlockTemplate* pbt, vNewBlockTemplate)
+                    delete pbt;
+                vNewBlockTemplate.clear();
+            }
+
+            // Create new block with nonce = 0 and extraNonce = 1
+            pblocktemplate = CreateNewBlockWithKey(*pminingKey);
+            if (!pblocktemplate)
+                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
+            CBlock* pblock = &pblocktemplate->block;
+            IncrementExtraNonce(pblock, pindexPrev, nExtraNonce);
+            pblock->nVersion.SetAuxpow(true);
+            pblock->hashMerkleRoot = pblock->BuildMerkleTree();
+
+            // Save
+            mapNewBlock[pblock->GetHash()] = pblock;
+            vNewBlockTemplate.push_back(pblocktemplate);
+        }
+        }
+
+        const CBlock& block = pblocktemplate->block;
+
+        arith_uint256 target;
+        bool fNegative, fOverflow;
+        target.SetCompact(block.nBits, &fNegative, &fOverflow);
+        if (fNegative || fOverflow || target == 0)
+            throw std::runtime_error("invalid difficulty bits in block");
+
+        json_spirit::Object result;
+        result.push_back(Pair("hash", block.GetHash().GetHex()));
+        result.push_back(Pair("chainid", block.nVersion.GetChainId()));
+        result.push_back(Pair("previousblockhash", block.hashPrevBlock.GetHex()));
+        result.push_back(Pair("coinbasevalue", (int64_t)block.vtx[0].vout[0].nValue));
+        result.push_back(Pair("bits", strprintf("%08x", block.nBits)));
+        result.push_back(Pair("height", static_cast<int64_t> (pindexPrev->nHeight + 1)));
+        result.push_back(Pair("_target", HexStr(BEGIN(target), END(target))));
+
+        return result;
+    }
+
+    /* Submit a block instead.  Note that this need not lock cs_main,
+       since ProcessBlockFound below locks it instead.  */
+
+    assert(params.size() == 2);
+    uint256 hash;
+    hash.SetHex(params[0].get_str());
+
+    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(params[1].get_str());
+    CDataStream ss(vchAuxPow, SER_GETHASH, PROTOCOL_VERSION);
+    CAuxPow pow;
+    ss >> pow;
+    block.SetAuxpow(new CAuxPow(pow));
+    assert(block.GetHash() == hash);
+
+    return ProcessBlockFound(&block, *pwalletMain, *pminingKey);
+}
+#endif // ENABLE_WALLET