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.

2 files changed, 77 insertions, 44 deletions

diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 193da7655..ce534a905 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -16,6 +16,7 @@
 #include <policy/fees.h>
 #include <policy/policy.h>
 #include <policy/rbf.h>
+#include <rpc/auxpow_miner.h>
 #include <rpc/mining.h>
 #include <rpc/rawtransaction.h>
 #include <rpc/server.h>
@@ -28,7 +29,6 @@
 #include <wallet/coincontrol.h>
 #include <wallet/feebumper.h>
 #include <wallet/rpcwallet.h>
-#include <wallet/wallet.h>
 #include <wallet/walletdb.h>
 #include <wallet/walletutil.h>
 
@@ -4759,6 +4759,75 @@ UniValue walletcreatefundedpsbt(const JSONRPCRequest& request)
     return result;
 }
 
+UniValue getauxblock(const JSONRPCRequest& request)
+{
+    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
+    CWallet* const pwallet = wallet.get();
+
+    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
+        return NullUniValue;
+    }
+
+    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", "")
+            );
+
+    if (pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
+        throw JSONRPCError(RPC_WALLET_ERROR, "Error: Private keys are disabled for this wallet");
+    }
+
+    std::shared_ptr<CReserveScript> coinbaseScript;
+    pwallet->GetScriptForMining(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 g_auxpow_miner->createAuxBlock(coinbaseScript->reserveScript);
+
+    /* Submit a block instead.  */
+    assert(request.params.size() == 2);
+    bool fAccepted
+        = g_auxpow_miner->submitAuxBlock(request.params[0].get_str(),
+                                         request.params[1].get_str());
+    if (fAccepted)
+        coinbaseScript->KeepScript();
+
+    return fAccepted;
+}
+
 extern UniValue abortrescan(const JSONRPCRequest& request); // in rpcdump.cpp
 extern UniValue dumpprivkey(const JSONRPCRequest& request); // in rpcdump.cpp
 extern UniValue importprivkey(const JSONRPCRequest& request);
@@ -4844,6 +4913,7 @@ static const CRPCCommand commands[] =
     { "wallet",             "setlabel",                         &setlabel,                      {"address","label"} },
 
     { "generating",         "generate",                         &generate,                      {"nblocks","maxtries"} },
+    { "mining",             "getauxblock",                      &getauxblock,                   {"hash", "auxpow"} },
 };
 
 void RegisterWalletRPCCommands(CRPCTable &t)
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 7b791ae41..ae5de3e85 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -7,6 +7,7 @@
 #define BITCOIN_WALLET_WALLET_H
 
 #include <amount.h>
+#include <auxpow.h> // contains CBaseMerkleTx
 #include <outputtype.h>
 #include <policy/feerate.h>
 #include <streams.h>
@@ -208,58 +209,21 @@ struct COutputEntry
 };
 
 /** A transaction with a merkle branch linking it to the block chain. */
-class CMerkleTx
+class CMerkleTx : public CBaseMerkleTx
 {
 private:
   /** Constant used in hashBlock to indicate tx has been abandoned */
     static const uint256 ABANDON_HASH;
 
 public:
-    CTransactionRef tx;
-    uint256 hashBlock;
 
-    /* An nIndex == -1 means that hashBlock (in nonzero) refers to the earliest
-     * block in the chain we know this or any in-wallet dependency conflicts
-     * with. Older clients interpret nIndex == -1 as unconfirmed for backward
-     * compatibility.
-     */
-    int nIndex;
-
-    CMerkleTx()
-    {
-        SetTx(MakeTransactionRef());
-        Init();
-    }
+    CMerkleTx() = default;
 
     explicit CMerkleTx(CTransactionRef arg)
-    {
-        SetTx(std::move(arg));
-        Init();
-    }
-
-    void Init()
-    {
-        hashBlock = uint256();
-        nIndex = -1;
-    }
-
-    void SetTx(CTransactionRef arg)
-    {
-        tx = std::move(arg);
-    }
-
-    ADD_SERIALIZE_METHODS;
-
-    template <typename Stream, typename Operation>
-    inline void SerializationOp(Stream& s, Operation ser_action) {
-        std::vector<uint256> vMerkleBranch; // For compatibility with older versions.
-        READWRITE(tx);
-        READWRITE(hashBlock);
-        READWRITE(vMerkleBranch);
-        READWRITE(nIndex);
-    }
+      : CBaseMerkleTx(arg)
+    {}
 
-    void SetMerkleBranch(const CBlockIndex* pIndex, int posInBlock);
+    void SetMerkleBranch(const CBlockIndex* pindex, int posInBlock);
 
     /**
      * Return depth of transaction in blockchain:
@@ -274,7 +238,6 @@ public:
     bool isAbandoned() const { return (hashBlock == ABANDON_HASH); }
     void setAbandoned() { hashBlock = ABANDON_HASH; }
 
-    const uint256& GetHash() const { return tx->GetHash(); }
     bool IsCoinBase() const { return tx->IsCoinBase(); }
 };