Merge #9955: Don't require segwit in getblocktemplate for segwit signalling or mining

c85ffe6 Test transaction selection when gbt called without segwit support (Suhas Daftuar)
abe7b3d Don't require segwit in getblocktemplate for segwit signalling or mining (Suhas Daftuar)

Tree-SHA512: 172496b6d7cdf1879de1266748f2b4ed9fd2ba9ff4a1fd964d74d73c674c16d74bf01a3ba42bf25f2d69f348217c0bbf3412ac64821f222efc9de25a287a5240

src/miner.cpp

@@ -137,7 +137,7 @@ void BlockAssembler::resetBlock()
     nFees = 0;
 }
 
-std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn)
+std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn, bool fMineWitnessTx)
 {
     resetBlock();
 
@@ -175,7 +175,7 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& sc
     // -promiscuousmempoolflags is used.
     // TODO: replace this with a call to main to assess validity of a mempool
     // transaction (which in most cases can be a no-op).
-    fIncludeWitness = IsWitnessEnabled(pindexPrev, chainparams.GetConsensus());
+    fIncludeWitness = IsWitnessEnabled(pindexPrev, chainparams.GetConsensus()) && fMineWitnessTx;
 
     addPackageTxs();
 

src/miner.h

@@ -170,7 +170,7 @@ public:
     BlockAssembler(const CChainParams& params, const Options& options);
 
     /** Construct a new block template with coinbase to scriptPubKeyIn */
-    std::unique_ptr<CBlockTemplate> CreateNewBlock(const CScript& scriptPubKeyIn);
+    std::unique_ptr<CBlockTemplate> CreateNewBlock(const CScript& scriptPubKeyIn, bool fMineWitnessTx=true);
 
 private:
     // utility functions

src/rpc/mining.cpp

@@ -514,12 +514,22 @@ UniValue getblocktemplate(const JSONRPCRequest& request)
         // TODO: Maybe recheck connections/IBD and (if something wrong) send an expires-immediately template to stop miners?
     }
 
+    const struct BIP9DeploymentInfo& segwit_info = VersionBitsDeploymentInfo[Consensus::DEPLOYMENT_SEGWIT];
+    // If the caller is indicating segwit support, then allow CreateNewBlock()
+    // to select witness transactions, after segwit activates (otherwise
+    // don't).
+    bool fSupportsSegwit = setClientRules.find(segwit_info.name) != setClientRules.end();
+
     // Update block
     static CBlockIndex* pindexPrev;
     static int64_t nStart;
     static std::unique_ptr<CBlockTemplate> pblocktemplate;
+    // Cache whether the last invocation was with segwit support, to avoid returning
+    // a segwit-block to a non-segwit caller.
+    static bool fLastTemplateSupportsSegwit = true;
     if (pindexPrev != chainActive.Tip() ||
-        (mempool.GetTransactionsUpdated() != nTransactionsUpdatedLast && GetTime() - nStart > 5))
+        (mempool.GetTransactionsUpdated() != nTransactionsUpdatedLast && GetTime() - nStart > 5) ||
+        fLastTemplateSupportsSegwit != fSupportsSegwit)
     {
         // Clear pindexPrev so future calls make a new block, despite any failures from here on
         pindexPrev = nullptr;
@@ -528,10 +538,11 @@ UniValue getblocktemplate(const JSONRPCRequest& request)
         nTransactionsUpdatedLast = mempool.GetTransactionsUpdated();
         CBlockIndex* pindexPrevNew = chainActive.Tip();
         nStart = GetTime();
+        fLastTemplateSupportsSegwit = fSupportsSegwit;
 
         // Create new block
         CScript scriptDummy = CScript() << OP_TRUE;
-        pblocktemplate = BlockAssembler(Params()).CreateNewBlock(scriptDummy);
+        pblocktemplate = BlockAssembler(Params()).CreateNewBlock(scriptDummy, fSupportsSegwit);
         if (!pblocktemplate)
             throw JSONRPCError(RPC_OUT_OF_MEMORY, "Out of memory");
 
@@ -681,8 +692,7 @@ UniValue getblocktemplate(const JSONRPCRequest& request)
     result.push_back(Pair("bits", strprintf("%08x", pblock->nBits)));
     result.push_back(Pair("height", (int64_t)(pindexPrev->nHeight+1)));
 
-    const struct BIP9DeploymentInfo& segwit_info = VersionBitsDeploymentInfo[Consensus::DEPLOYMENT_SEGWIT];
-    if (!pblocktemplate->vchCoinbaseCommitment.empty() && setClientRules.find(segwit_info.name) != setClientRules.end()) {
+    if (!pblocktemplate->vchCoinbaseCommitment.empty() && fSupportsSegwit) {
         result.push_back(Pair("default_witness_commitment", HexStr(pblocktemplate->vchCoinbaseCommitment.begin(), pblocktemplate->vchCoinbaseCommitment.end())));
     }
 

src/versionbits.cpp

@@ -17,7 +17,7 @@ const struct BIP9DeploymentInfo VersionBitsDeploymentInfo[Consensus::MAX_VERSION
     },
     {
         /*.name =*/ "segwit",
-        /*.gbt_force =*/ false,
+        /*.gbt_force =*/ true,
     }
 };