Implement BIP 9 GBT changes

- BIP9DeploymentInfo struct for static deployment info
- VersionBitsDeploymentInfo: Avoid C++11ism by commenting parameter names
- getblocktemplate: Make sure to set deployments in the version if it is LOCKED_IN
- In this commit, all rules are considered required for clients to support

6 files changed, 70 insertions, 3 deletions

diff --git a/src/consensus/params.h b/src/consensus/params.h
index 4f3480b89b..6c4cc49479 100644
--- a/src/consensus/params.h
+++ b/src/consensus/params.h
@@ -16,6 +16,7 @@ enum DeploymentPos
 {
     DEPLOYMENT_TESTDUMMY,
     DEPLOYMENT_CSV, // Deployment of BIP68, BIP112, and BIP113.
+    // NOTE: Also add new deployments to VersionBitsDeploymentInfo in versionbits.cpp
     MAX_VERSION_BITS_DEPLOYMENTS
 };
 
diff --git a/src/main.cpp b/src/main.cpp
index f74cb30574..623d77985c 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -2122,7 +2122,7 @@ void PartitionCheck(bool (*initialDownloadCheck)(), CCriticalSection& cs, const
 }
 
 // Protected by cs_main
-static VersionBitsCache versionbitscache;
+VersionBitsCache versionbitscache;
 
 int32_t ComputeBlockVersion(const CBlockIndex* pindexPrev, const Consensus::Params& params)
 {
diff --git a/src/main.h b/src/main.h
index 6936b5379a..404a787e4d 100644
--- a/src/main.h
+++ b/src/main.h
@@ -551,6 +551,8 @@ extern CBlockTreeDB *pblocktree;
  */
 int GetSpendHeight(const CCoinsViewCache& inputs);
 
+extern VersionBitsCache versionbitscache;
+
 /**
  * Determine what nVersion a new block should use.
  */
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index c33082fca0..277696fe0b 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -7,6 +7,7 @@
 #include "chain.h"
 #include "chainparams.h"
 #include "consensus/consensus.h"
+#include "consensus/params.h"
 #include "consensus/validation.h"
 #include "core_io.h"
 #include "init.h"
@@ -260,6 +261,13 @@ static UniValue BIP22ValidationResult(const CValidationState& state)
     return "valid?";
 }
 
+std::string gbt_vb_name(const Consensus::DeploymentPos pos) {
+    const struct BIP9DeploymentInfo& vbinfo = VersionBitsDeploymentInfo[pos];
+    std::string s = vbinfo.name;
+    s.insert(s.begin(), '!');
+    return s;
+}
+
 UniValue getblocktemplate(const UniValue& params, bool fHelp)
 {
     if (fHelp || params.size() > 1)
@@ -267,7 +275,9 @@ UniValue getblocktemplate(const UniValue& params, bool fHelp)
             "getblocktemplate ( \"jsonrequestobject\" )\n"
             "\nIf the request parameters include a 'mode' key, that is used to explicitly select between the default 'template' request or a 'proposal'.\n"
             "It returns data needed to construct a block to work on.\n"
-            "See https://en.bitcoin.it/wiki/BIP_0022 for full specification.\n"
+            "For full specification, see BIPs 22 and 9:\n"
+            "    https://github.com/bitcoin/bips/blob/master/bip-0022.mediawiki\n"
+            "    https://github.com/bitcoin/bips/blob/master/bip-0009.mediawiki#getblocktemplate_changes\n"
 
             "\nArguments:\n"
             "1. \"jsonrequestobject\"       (string, optional) A json object in the following spec\n"
@@ -283,6 +293,12 @@ UniValue getblocktemplate(const UniValue& params, bool fHelp)
             "\nResult:\n"
             "{\n"
             "  \"version\" : n,                    (numeric) The block version\n"
+            "  \"rules\" : [ \"rulename\", ... ],    (array of strings) specific block rules that are to be enforced\n"
+            "  \"vbavailable\" : {                 (json object) set of pending, supported versionbit (BIP 9) softfork deployments\n"
+            "      \"rulename\" : bitnumber        (numeric) identifies the bit number as indicating acceptance and readiness for the named softfork rule\n"
+            "      ,...\n"
+            "  },\n"
+            "  \"vbrequired\" : n,                 (numeric) bit mask of versionbits the server requires set in submissions\n"
             "  \"previousblockhash\" : \"xxxx\",    (string) The hash of current highest block\n"
             "  \"transactions\" : [                (array) contents of non-coinbase transactions that should be included in the next block\n"
             "      {\n"
@@ -458,9 +474,10 @@ UniValue getblocktemplate(const UniValue& params, bool fHelp)
         pindexPrev = pindexPrevNew;
     }
     CBlock* pblock = &pblocktemplate->block; // pointer for convenience
+    const Consensus::Params& consensusParams = Params().GetConsensus();
 
     // Update nTime
-    UpdateTime(pblock, Params().GetConsensus(), pindexPrev);
+    UpdateTime(pblock, consensusParams, pindexPrev);
     pblock->nNonce = 0;
 
     UniValue aCaps(UniValue::VARR); aCaps.push_back("proposal");
@@ -511,7 +528,36 @@ UniValue getblocktemplate(const UniValue& params, bool fHelp)
 
     UniValue result(UniValue::VOBJ);
     result.push_back(Pair("capabilities", aCaps));
+
+    UniValue aRules(UniValue::VARR);
+    UniValue vbavailable(UniValue::VOBJ);
+    for (int i = 0; i < (int)Consensus::MAX_VERSION_BITS_DEPLOYMENTS; ++i) {
+        Consensus::DeploymentPos pos = Consensus::DeploymentPos(i);
+        ThresholdState state = VersionBitsState(pindexPrev, consensusParams, pos, versionbitscache);
+        switch (state) {
+            case THRESHOLD_DEFINED:
+            case THRESHOLD_FAILED:
+                // Not exposed to GBT at all
+                break;
+            case THRESHOLD_LOCKED_IN:
+                // Ensure bit is set in block version
+                pblock->nVersion |= VersionBitsMask(consensusParams, pos);
+                // FALL THROUGH to get vbavailable set...
+            case THRESHOLD_STARTED:
+                // Add to vbavailable (and it's presumably in version already)
+                vbavailable.push_back(Pair(gbt_vb_name(pos), consensusParams.vDeployments[pos].bit));
+                break;
+            case THRESHOLD_ACTIVE:
+                // Add to rules only
+                aRules.push_back(gbt_vb_name(pos));
+                break;
+        }
+    }
     result.push_back(Pair("version", pblock->nVersion));
+    result.push_back(Pair("rules", aRules));
+    result.push_back(Pair("vbavailable", vbavailable));
+    result.push_back(Pair("vbrequired", int(0)));
+
     result.push_back(Pair("previousblockhash", pblock->hashPrevBlock.GetHex()));
     result.push_back(Pair("transactions", transactions));
     result.push_back(Pair("coinbaseaux", aux));
diff --git a/src/versionbits.cpp b/src/versionbits.cpp
index fbb60c0fc5..041ca2adbc 100644
--- a/src/versionbits.cpp
+++ b/src/versionbits.cpp
@@ -4,6 +4,17 @@
 
 #include "versionbits.h"
 
+#include "consensus/params.h"
+
+const struct BIP9DeploymentInfo VersionBitsDeploymentInfo[Consensus::MAX_VERSION_BITS_DEPLOYMENTS] = {
+    {
+        /*.name =*/ "testdummy",
+    },
+    {
+        /*.name =*/ "csv",
+    }
+};
+
 ThresholdState AbstractThresholdConditionChecker::GetStateFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const
 {
     int nPeriod = Period(params);
diff --git a/src/versionbits.h b/src/versionbits.h
index 04f4738272..d805942028 100644
--- a/src/versionbits.h
+++ b/src/versionbits.h
@@ -30,6 +30,13 @@ enum ThresholdState {
 // will either be NULL or a block with (height + 1) % Period() == 0.
 typedef std::map<const CBlockIndex*, ThresholdState> ThresholdConditionCache;
 
+struct BIP9DeploymentInfo {
+    /** Deployment name */
+    const char *name;
+};
+
+extern const struct BIP9DeploymentInfo VersionBitsDeploymentInfo[];
+
 /**
  * Abstract class that implements BIP9-style threshold logic, and caches results.
  */