Network upgrade activation mechanism

src/Makefile.am

@@ -138,6 +138,7 @@ BITCOIN_CORE_H = \
   compressor.h \
   consensus/consensus.h \
   consensus/params.h \
+  consensus/upgrades.h \
   consensus/validation.h \
   core_io.h \
   core_memusage.h \
@@ -354,6 +355,7 @@ libbitcoin_common_a_SOURCES = \
   chainparams.cpp \
   coins.cpp \
   compressor.cpp \
+  consensus/upgrades.cpp \
   core_read.cpp \
   core_write.cpp \
   hash.cpp \

src/Makefile.gtest.include

@@ -33,6 +33,7 @@ zcash_gtest_SOURCES += \
 	gtest/test_random.cpp \
 	gtest/test_rpc.cpp \
 	gtest/test_transaction.cpp \
+	gtest/test_upgrades.cpp \
 	gtest/test_validation.cpp \
 	gtest/test_circuit.cpp \
 	gtest/test_txid.cpp \

src/chain.h

@@ -94,8 +94,14 @@ enum BlockStatus: uint32_t {
     BLOCK_FAILED_VALID       =   32, //! stage after last reached validness failed
     BLOCK_FAILED_CHILD       =   64, //! descends from failed block
     BLOCK_FAILED_MASK        =   BLOCK_FAILED_VALID | BLOCK_FAILED_CHILD,
+
+    BLOCK_ACTIVATES_UPGRADE  =   128, //! block activates a network upgrade
 };
 
+//! Short-hand for the highest consensus validity we implement.
+//! Blocks with this validity are assumed to satisfy all consensus rules.
+static const BlockStatus BLOCK_VALID_CONSENSUS = BLOCK_VALID_SCRIPTS;
+
 /** The block chain is a tree shaped structure starting with the
  * genesis block at the root, with each block potentially having multiple
  * candidates to be the next block. A blockindex may have multiple pprev pointing
@@ -140,6 +146,11 @@ class CBlockIndex
     //! Verification status of this block. See enum BlockStatus
     unsigned int nStatus;
 
+    //! Branch ID corresponding to the consensus rules used to validate this block.
+    //! Only cached if block validity is BLOCK_VALID_CONSENSUS.
+    //! Persisted at each activation height, memory-only for intervening blocks.
+    boost::optional<uint32_t> nCachedBranchId;
+
     //! The anchor for the tree state up to the start of this block
     uint256 hashAnchor;
 
@@ -180,6 +191,7 @@ class CBlockIndex
         nTx = 0;
         nChainTx = 0;
         nStatus = 0;
+        nCachedBranchId = boost::none;
         hashAnchor = uint256();
         hashAnchorEnd = uint256();
         nSequenceId = 0;
@@ -341,6 +353,18 @@ class CDiskBlockIndex : public CBlockIndex
             READWRITE(VARINT(nDataPos));
         if (nStatus & BLOCK_HAVE_UNDO)
             READWRITE(VARINT(nUndoPos));
+        if (nStatus & BLOCK_ACTIVATES_UPGRADE) {
+            if (ser_action.ForRead()) {
+                uint32_t branchId;
+                READWRITE(branchId);
+                nCachedBranchId = branchId;
+            } else {
+                // nCachedBranchId must always be set if BLOCK_ACTIVATES_UPGRADE is set.
+                assert(nCachedBranchId);
+                uint32_t branchId = *nCachedBranchId;
+                READWRITE(branchId);
+            }
+        }
         READWRITE(hashAnchor);
 
         // block header

src/chainparams.cpp

@@ -90,6 +90,13 @@ class CMainParams : public CChainParams {
         consensus.nPowMaxAdjustDown = 32; // 32% adjustment down
         consensus.nPowMaxAdjustUp = 16; // 16% adjustment up
         consensus.nPowTargetSpacing = 2.5 * 60;
+        consensus.vUpgrades[Consensus::BASE_SPROUT].nActivationHeight =
+            Consensus::NetworkUpgrade::ALWAYS_ACTIVE;
+        consensus.vUpgrades[Consensus::UPGRADE_TESTDUMMY].nActivationHeight =
+            Consensus::NetworkUpgrade::NO_ACTIVATION_HEIGHT;
+        consensus.vUpgrades[Consensus::UPGRADE_OVERWINTER].nActivationHeight =
+            Consensus::NetworkUpgrade::NO_ACTIVATION_HEIGHT;
+
         /**
          * The message start string should be awesome! ⓩ❤
          */
@@ -241,6 +248,13 @@ class CTestNetParams : public CChainParams {
         consensus.nPowMaxAdjustDown = 32; // 32% adjustment down
         consensus.nPowMaxAdjustUp = 16; // 16% adjustment up
         consensus.nPowTargetSpacing = 2.5 * 60;
+        consensus.vUpgrades[Consensus::BASE_SPROUT].nActivationHeight =
+            Consensus::NetworkUpgrade::ALWAYS_ACTIVE;
+        consensus.vUpgrades[Consensus::UPGRADE_TESTDUMMY].nActivationHeight =
+            Consensus::NetworkUpgrade::NO_ACTIVATION_HEIGHT;
+        consensus.vUpgrades[Consensus::UPGRADE_OVERWINTER].nActivationHeight =
+            Consensus::NetworkUpgrade::NO_ACTIVATION_HEIGHT;
+
         pchMessageStart[0] = 0xfa;
         pchMessageStart[1] = 0x1a;
         pchMessageStart[2] = 0xf9;
@@ -341,6 +355,12 @@ class CRegTestParams : public CChainParams {
         consensus.nPowMaxAdjustDown = 0; // Turn off adjustment down
         consensus.nPowMaxAdjustUp = 0; // Turn off adjustment up
         consensus.nPowTargetSpacing = 2.5 * 60;
+        consensus.vUpgrades[Consensus::BASE_SPROUT].nActivationHeight =
+            Consensus::NetworkUpgrade::ALWAYS_ACTIVE;
+        consensus.vUpgrades[Consensus::UPGRADE_TESTDUMMY].nActivationHeight =
+            Consensus::NetworkUpgrade::NO_ACTIVATION_HEIGHT;
+        consensus.vUpgrades[Consensus::UPGRADE_OVERWINTER].nActivationHeight =
+            Consensus::NetworkUpgrade::NO_ACTIVATION_HEIGHT;
 
         pchMessageStart[0] = 0xaa;
         pchMessageStart[1] = 0xe8;
@@ -394,6 +414,12 @@ class CRegTestParams : public CChainParams {
         vFoundersRewardAddress = { "t2FwcEhFdNXuFMv1tcYwaBJtYVtMj8b1uTg" };
         assert(vFoundersRewardAddress.size() <= consensus.GetLastFoundersRewardBlockHeight());
     }
+
+    void UpdateNetworkUpgradeParameters(Consensus::UpgradeIndex idx, int nActivationHeight)
+    {
+        assert(idx > Consensus::BASE_SPROUT && idx < Consensus::MAX_NETWORK_UPGRADES);
+        consensus.vUpgrades[idx].nActivationHeight = nActivationHeight;
+    }
 };
 static CRegTestParams regTestParams;
 
@@ -467,3 +493,8 @@ std::string CChainParams::GetFoundersRewardAddressAtIndex(int i) const {
     assert(i >= 0 && i < vFoundersRewardAddress.size());
     return vFoundersRewardAddress[i];
 }
+
+void UpdateNetworkUpgradeParameters(Consensus::UpgradeIndex idx, int nActivationHeight)
+{
+    regTestParams.UpdateNetworkUpgradeParameters(idx, nActivationHeight);
+}

src/chainparams.h

@@ -134,4 +134,9 @@ void SelectParams(CBaseChainParams::Network network);
  */
 bool SelectParamsFromCommandLine();
 
+/**
+ * Allows modifying the network upgrade regtest parameters.
+ */
+void UpdateNetworkUpgradeParameters(Consensus::UpgradeIndex idx, int nActivationHeight);
+
 #endif // BITCOIN_CHAINPARAMS_H

src/consensus/params.h

@@ -9,6 +9,49 @@
 #include "uint256.h"
 
 namespace Consensus {
+
+/**
+ * Index into Params.vUpgrades and NetworkUpgradeInfo
+ *
+ * Being array indices, these MUST be numbered consecutively.
+ *
+ * The order of these indices MUST match the order of the upgrades on-chain, as
+ * several functions depends on the enum being sorted.
+ */
+enum UpgradeIndex {
+    // Sprout must be first
+    BASE_SPROUT,
+    UPGRADE_TESTDUMMY,
+    UPGRADE_OVERWINTER,
+    // NOTE: Also add new upgrades to NetworkUpgradeInfo in upgrades.cpp
+    MAX_NETWORK_UPGRADES
+};
+
+struct NetworkUpgrade {
+    /**
+     * Height of the first block for which the new consensus rules will be active
+     */
+    int nActivationHeight;
+
+    /**
+     * Special value for nActivationHeight indicating that the upgrade is always active.
+     * This is useful for testing, as it means tests don't need to deal with the activation
+     * process (namely, faking a chain of somewhat-arbitrary length).
+     *
+     * New blockchains that want to enable upgrade rules from the beginning can also use
+     * this value. However, additional care must be taken to ensure the genesis block
+     * satisfies the enabled rules.
+     */
+    static constexpr int ALWAYS_ACTIVE = 0;
+
+    /**
+     * Special value for nActivationHeight indicating that the upgrade will never activate.
+     * This is useful when adding upgrade code that has a testnet activation height, but
+     * should remain disabled on mainnet.
+     */
+    static constexpr int NO_ACTIVATION_HEIGHT = -1;
+};
+
 /**
  * Parameters that influence chain consensus.
  */
@@ -39,6 +82,7 @@ struct Params {
     int nMajorityEnforceBlockUpgrade;
     int nMajorityRejectBlockOutdated;
     int nMajorityWindow;
+    NetworkUpgrade vUpgrades[MAX_NETWORK_UPGRADES];
     /** Proof of work parameters */
     uint256 powLimit;
     int64_t nPowAveragingWindow;

src/consensus/upgrades.cpp

@@ -0,0 +1,122 @@
+// Copyright (c) 2018 The Zcash developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "consensus/upgrades.h"
+
+/**
+ * General information about each network upgrade.
+ * Ordered by Consensus::UpgradeIndex.
+ */
+const struct NUInfo NetworkUpgradeInfo[Consensus::MAX_NETWORK_UPGRADES] = {
+    {
+        /*.nBranchId =*/ 0,
+        /*.strName =*/ "Sprout",
+        /*.strInfo =*/ "The Zcash network at launch",
+    },
+    {
+        /*.nBranchId =*/ 0x74736554,
+        /*.strName =*/ "Test dummy",
+        /*.strInfo =*/ "Test dummy info",
+    },
+    {
+        /*.nBranchId =*/ 0x5ba81b19,
+        /*.strName =*/ "Overwinter",
+        /*.strInfo =*/ "TBD",
+    }
+};
+
+UpgradeState NetworkUpgradeState(
+    int nHeight,
+    const Consensus::Params& params,
+    Consensus::UpgradeIndex idx)
+{
+    assert(nHeight >= 0);
+    assert(idx >= Consensus::BASE_SPROUT && idx < Consensus::MAX_NETWORK_UPGRADES);
+    auto nActivationHeight = params.vUpgrades[idx].nActivationHeight;
+
+    if (nActivationHeight == Consensus::NetworkUpgrade::NO_ACTIVATION_HEIGHT) {
+        return UPGRADE_DISABLED;
+    } else if (nHeight >= nActivationHeight) {
+        // From ZIP ???:
+        //
+        // ACTIVATION_HEIGHT
+        //     The block height at which the network upgrade rules will come into effect.
+        //
+        //     For removal of ambiguity, the block at height ACTIVATION_HEIGHT - 1 is
+        //     subject to the pre-upgrade consensus rules.
+        return UPGRADE_ACTIVE;
+    } else {
+        return UPGRADE_PENDING;
+    }
+}
+
+bool NetworkUpgradeActive(
+    int nHeight,
+    const Consensus::Params& params,
+    Consensus::UpgradeIndex idx)
+{
+    return NetworkUpgradeState(nHeight, params, idx) == UPGRADE_ACTIVE;
+}
+
+int CurrentEpoch(int nHeight, const Consensus::Params& params) {
+    for (auto idxInt = Consensus::MAX_NETWORK_UPGRADES - 1; idxInt >= Consensus::BASE_SPROUT; idxInt--) {
+        if (NetworkUpgradeActive(nHeight, params, Consensus::UpgradeIndex(idxInt))) {
+            return idxInt;
+        }
+    }
+}
+
+uint32_t CurrentEpochBranchId(int nHeight, const Consensus::Params& params) {
+    return NetworkUpgradeInfo[CurrentEpoch(nHeight, params)].nBranchId;
+}
+
+bool IsActivationHeight(
+    int nHeight,
+    const Consensus::Params& params,
+    Consensus::UpgradeIndex idx)
+{
+    assert(idx >= Consensus::BASE_SPROUT && idx < Consensus::MAX_NETWORK_UPGRADES);
+
+    // Don't count Sprout as an activation height
+    if (idx == Consensus::BASE_SPROUT) {
+        return false;
+    }
+
+    return nHeight >= 0 && nHeight == params.vUpgrades[idx].nActivationHeight;
+}
+
+bool IsActivationHeightForAnyUpgrade(
+    int nHeight,
+    const Consensus::Params& params)
+{
+    if (nHeight < 0) {
+        return false;
+    }
+
+    // Don't count Sprout as an activation height
+    for (int idx = Consensus::BASE_SPROUT + 1; idx < Consensus::MAX_NETWORK_UPGRADES; idx++) {
+        if (nHeight == params.vUpgrades[idx].nActivationHeight)
+            return true;
+    }
+
+    return false;
+}
+
+boost::optional<int> NextActivationHeight(
+    int nHeight,
+    const Consensus::Params& params)
+{
+    if (nHeight < 0) {
+        return boost::none;
+    }
+
+    // Don't count Sprout as an activation height
+    for (auto idx = Consensus::BASE_SPROUT + 1; idx < Consensus::MAX_NETWORK_UPGRADES; idx++) {
+        if (NetworkUpgradeState(nHeight, params, Consensus::UpgradeIndex(idx)) == UPGRADE_PENDING) {
+            return params.vUpgrades[idx].nActivationHeight;
+        }
+    }
+
+    return boost::none;
+}