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

4 files changed, 18 insertions, 8 deletions

diff --git a/src/miner.cpp b/src/miner.cpp
index 67e7ff155..ff28a5680 100644
--- a/src/miner.cpp
+++ b/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();
 
diff --git a/src/miner.h b/src/miner.h
index c105d07c2..a159b0553 100644
--- a/src/miner.h
+++ b/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
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index abdfa651a..4db8ffaa7 100644
--- a/src/rpc/mining.cpp
+++ b/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())));
     }
 
diff --git a/src/versionbits.cpp b/src/versionbits.cpp
index d73f34051..8a7cce748 100644
--- a/src/versionbits.cpp
+++ b/src/versionbits.cpp
@@ -17,7 +17,7 @@ const struct BIP9DeploymentInfo VersionBitsDeploymentInfo[Consensus::MAX_VERSION
     },
     {
         /*.name =*/ "segwit",
-        /*.gbt_force =*/ false,
+        /*.gbt_force =*/ true,
     }
 };