versionbits: Move BIP9 status logic for getblocktemplate to versionbits

Rather than having the RPC code have knowledge about how BIP9 is
implemented, create a reporting function in the versionbits code, and
limit the RPC code to coverting the result of that into the appropriate
output for getblocktemplate.

Author: ajtowns

src/rpc/mining.cpp

@@ -565,10 +565,10 @@ static UniValue BIP22ValidationResult(const BlockValidationState& state)
     return "valid?";
 }
 
-static std::string gbt_vb_name(const Consensus::DeploymentPos pos) {
-    const struct VBDeploymentInfo& vbinfo = VersionBitsDeploymentInfo[pos];
-    std::string s = vbinfo.name;
-    if (!vbinfo.gbt_force) {
+static std::string gbt_force_name(const std::string& name, bool gbt_force)
+{
+    std::string s{name};
+    if (!gbt_force) {
         s.insert(s.begin(), '!');
     }
     return s;
@@ -898,45 +898,33 @@ static RPCHelpMan getblocktemplate()
     }
 
     UniValue vbavailable(UniValue::VOBJ);
-    for (int j = 0; j < (int)Consensus::MAX_VERSION_BITS_DEPLOYMENTS; ++j) {
-        Consensus::DeploymentPos pos = Consensus::DeploymentPos(j);
-        ThresholdState state = chainman.m_versionbitscache.State(pindexPrev, consensusParams, pos);
-        switch (state) {
-            case ThresholdState::DEFINED:
-            case ThresholdState::FAILED:
-                // Not exposed to GBT at all
-                break;
-            case ThresholdState::LOCKED_IN:
-                // Ensure bit is set in block version
-                block.nVersion |= chainman.m_versionbitscache.Mask(consensusParams, pos);
-                [[fallthrough]];
-            case ThresholdState::STARTED:
-            {
-                const struct VBDeploymentInfo& vbinfo = VersionBitsDeploymentInfo[pos];
-                vbavailable.pushKV(gbt_vb_name(pos), consensusParams.vDeployments[pos].bit);
-                if (setClientRules.find(vbinfo.name) == setClientRules.end()) {
-                    if (!vbinfo.gbt_force) {
-                        // If the client doesn't support this, don't indicate it in the [default] version
-                        block.nVersion &= ~chainman.m_versionbitscache.Mask(consensusParams, pos);
-                    }
-                }
-                break;
-            }
-            case ThresholdState::ACTIVE:
-            {
-                // Add to rules only
-                const struct VBDeploymentInfo& vbinfo = VersionBitsDeploymentInfo[pos];
-                aRules.push_back(gbt_vb_name(pos));
-                if (setClientRules.find(vbinfo.name) == setClientRules.end()) {
-                    // Not supported by the client; make sure it's safe to proceed
-                    if (!vbinfo.gbt_force) {
-                        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Support for '%s' rule requires explicit client support", vbinfo.name));
-                    }
-                }
-                break;
-            }
+    const auto gbtstatus = chainman.m_versionbitscache.GBTStatus(*pindexPrev, consensusParams);
+
+    for (const auto& [name, info] : gbtstatus.signalling) {
+        vbavailable.pushKV(gbt_force_name(name, info.gbt_force), info.bit);
+        if (!info.gbt_force && !setClientRules.count(name)) {
+            // If the client doesn't support this, don't indicate it in the [default] version
+            block.nVersion &= ~info.mask;
         }
     }
+
+    for (const auto& [name, info] : gbtstatus.locked_in) {
+        block.nVersion |= info.mask;
+        vbavailable.pushKV(gbt_force_name(name, info.gbt_force), info.bit);
+        if (!info.gbt_force && !setClientRules.count(name)) {
+            // If the client doesn't support this, don't indicate it in the [default] version
+            block.nVersion &= ~info.mask;
+        }
+    }
+
+    for (const auto& [name, info] : gbtstatus.active) {
+        aRules.push_back(gbt_force_name(name, info.gbt_force));
+        if (!info.gbt_force && !setClientRules.count(name)) {
+            // Not supported by the client; make sure it's safe to proceed
+            throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Support for '%s' rule requires explicit client support", name));
+        }
+    }
+
     result.pushKV("version", block.nVersion);
     result.pushKV("rules", std::move(aRules));
     result.pushKV("vbavailable", std::move(vbavailable));

src/versionbits.cpp

@@ -3,6 +3,7 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <consensus/params.h>
+#include <deploymentinfo.h>
 #include <kernel/chainparams.h>
 #include <util/check.h>
 #include <versionbits.h>
@@ -246,6 +247,37 @@ BIP9Info VersionBitsCache::Info(const CBlockIndex& block_index, const Consensus:
     return result;
 }
 
+BIP9GBTStatus VersionBitsCache::GBTStatus(const CBlockIndex& block_index, const Consensus::Params& params)
+{
+    BIP9GBTStatus result;
+
+    LOCK(m_mutex);
+    for (int i = 0; i < (int)Consensus::MAX_VERSION_BITS_DEPLOYMENTS; i++) {
+        auto pos = static_cast<Consensus::DeploymentPos>(i);
+        VersionBitsConditionChecker checker(params, pos);
+        ThresholdState state = checker.GetStateFor(&block_index, m_caches[pos]);
+        const VBDeploymentInfo& vbdepinfo = VersionBitsDeploymentInfo[pos];
+        BIP9GBTStatus::Info gbtinfo{.bit=params.vDeployments[pos].bit, .mask=checker.Mask(), .gbt_force=vbdepinfo.gbt_force};
+
+        switch (state) {
+        case DEFINED:
+        case FAILED:
+            // Not exposed to GBT
+            break;
+        case STARTED:
+            result.signalling.try_emplace(vbdepinfo.name, gbtinfo);
+            break;
+        case LOCKED_IN:
+            result.locked_in.try_emplace(vbdepinfo.name, gbtinfo);
+            break;
+        case ACTIVE:
+            result.active.try_emplace(vbdepinfo.name, gbtinfo);
+            break;
+        }
+    }
+    return result;
+}
+
 ThresholdState VersionBitsCache::State(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos)
 {
     LOCK(m_mutex);

src/versionbits.h

@@ -66,6 +66,15 @@ struct BIP9Info {
     std::optional<int> active_since;
 };
 
+struct BIP9GBTStatus {
+    struct Info {
+        int bit;
+        uint32_t mask;
+        bool gbt_force;
+    };
+    std::map<std::string, const Info, std::less<>> signalling, locked_in, active;
+};
+
 /**
  * Abstract class that implements BIP9-style threshold logic, and caches results.
  */
@@ -109,6 +118,8 @@ class VersionBitsCache
 
     BIP9Info Info(const CBlockIndex& block_index, const Consensus::Params& params, Consensus::DeploymentPos id) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
 
+    BIP9GBTStatus GBTStatus(const CBlockIndex& block_index, const Consensus::Params& params) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
+
     /** Get the BIP9 state for a given deployment for the block after pindexPrev. */
     ThresholdState State(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);