Remove 16 bits from versionbits signalling

This removes bits 13-28 inclusive (0x1fffe000) from the versionbits signalling system, preventing warnings from being generated for any miners using these bits. This effectively reserves 16 bit for miscellaneous use by miners for things like version-rolling and nonce-rolling and establishes a zone miners can use without causing unexpected disruption.
btcdrak · Mar 6, 2018 · d12516e · d12516e
1 parent 7deba93
commit d12516e
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Showing 4 changed files with 18 additions and 6 deletions.
diff --git a/src/chainparams.cpp b/src/chainparams.cpp
@@ -87,7 +87,7 @@ class CMainParams : public CChainParams {
         consensus.fPowNoRetargeting = false;
         consensus.nRuleChangeActivationThreshold = 1916; // 95% of 2016
         consensus.nMinerConfirmationWindow = 2016; // nPowTargetTimespan / nPowTargetSpacing
-        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
+        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 12;
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = 1199145601; // January 1, 2008
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = 1230767999; // December 31, 2008
 
@@ -201,7 +201,7 @@ class CTestNetParams : public CChainParams {
         consensus.fPowNoRetargeting = false;
         consensus.nRuleChangeActivationThreshold = 1512; // 75% for testchains
         consensus.nMinerConfirmationWindow = 2016; // nPowTargetTimespan / nPowTargetSpacing
-        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
+        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 12;
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = 1199145601; // January 1, 2008
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = 1230767999; // December 31, 2008
 
@@ -294,7 +294,7 @@ class CRegTestParams : public CChainParams {
         consensus.fPowNoRetargeting = true;
         consensus.nRuleChangeActivationThreshold = 108; // 75% for testchains
         consensus.nMinerConfirmationWindow = 144; // Faster than normal for regtest (144 instead of 2016)
-        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
+        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 12;
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = 0;
         consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
         consensus.vDeployments[Consensus::DEPLOYMENT_CSV].bit = 0;

diff --git a/src/validation.cpp b/src/validation.cpp
@@ -2160,7 +2160,7 @@ void static UpdateTip(const CBlockIndex *pindexNew, const CChainParams& chainPar
         for (int i = 0; i < 100 && pindex != nullptr; i++)
         {
             int32_t nExpectedVersion = ComputeBlockVersion(pindex->pprev, chainParams.GetConsensus());
-            if (pindex->nVersion > VERSIONBITS_LAST_OLD_BLOCK_VERSION && (pindex->nVersion & ~nExpectedVersion) != 0)
+            if (pindex->nVersion > VERSIONBITS_LAST_OLD_BLOCK_VERSION && (pindex->nVersion & ~nExpectedVersion & VERSIONBITS_IGNORE_MASK) != 0)
                 ++nUpgraded;
             pindex = pindex->pprev;
         }

diff --git a/src/versionbits.h b/src/versionbits.h
@@ -15,7 +15,9 @@ static const int32_t VERSIONBITS_TOP_BITS = 0x20000000UL;
 /** What bitmask determines whether versionbits is in use */
 static const int32_t VERSIONBITS_TOP_MASK = 0xE0000000UL;
 /** Total bits available for versionbits */
-static const int32_t VERSIONBITS_NUM_BITS = 29;
+static const int32_t VERSIONBITS_NUM_BITS = 13;
+/** Bitmask for ignored versionbits. It should match VERSIONBITS_NUM_BITS (BIPxxx) */
+static const int32_t VERSIONBITS_IGNORE_MASK = 0xE0001FFFUL;
 
 enum ThresholdState {
     THRESHOLD_DEFINED,

diff --git a/test/functional/feature_versionbits_warning.py b/test/functional/feature_versionbits_warning.py
@@ -19,8 +19,9 @@
 VB_PERIOD = 144           # versionbits period length for regtest
 VB_THRESHOLD = 108        # versionbits activation threshold for regtest
 VB_TOP_BITS = 0x20000000
-VB_UNKNOWN_BIT = 27       # Choose a bit unassigned to any deployment
+VB_UNKNOWN_BIT = 11       # Choose a bit unassigned to any deployment
 VB_UNKNOWN_VERSION = VB_TOP_BITS | (1 << VB_UNKNOWN_BIT)
+VB_IGNORE_VERSION = VB_TOP_BITS | 0x1FFFE000
 
 WARN_UNKNOWN_RULES_MINED = "Unknown block versions being mined! It's possible unknown rules are in effect"
 WARN_UNKNOWN_RULES_ACTIVE = "unknown new rules activated (versionbit {})".format(VB_UNKNOWN_BIT)
@@ -71,6 +72,15 @@ def run_test(self):
         # Mine one period worth of blocks
         node.generate(VB_PERIOD)
 
+        self.log.info("Check that there is no warning if previous VB_BLOCKS have VB_PERIOD blocks with ignored versionbits version.")
+        # Build one period of blocks with ignored bit. There should be no warning
+        self.send_blocks_with_version(node.p2p, VB_PERIOD, VB_IGNORE_VERSION)
+        assert(not WARN_UNKNOWN_RULES_MINED in node.getmininginfo()["warnings"])
+        assert(not WARN_UNKNOWN_RULES_MINED in node.getnetworkinfo()["warnings"])
+        assert(not VB_PATTERN.match(node.getmininginfo()["warnings"]))
+        assert(not VB_PATTERN.match(node.getnetworkinfo()["warnings"]))
+        assert(not self.versionbits_in_alert_file())
+
         self.log.info("Check that there is no warning if previous VB_BLOCKS have <VB_THRESHOLD blocks with unknown versionbits version.")
         # Build one period of blocks with < VB_THRESHOLD blocks signaling some unknown bit
         self.send_blocks_with_version(node.p2p, VB_THRESHOLD - 1, VB_UNKNOWN_VERSION)