Ignore old versionbit activations

Adds a hardcoded height to the consensus chain parameters for
ignoring versionbit activations prior to a fixed height.

Author: ajtowns

src/chainparams.cpp

@@ -71,6 +71,7 @@ class CMainParams : public CChainParams {
         consensus.BIP66Height = 363725; // 00000000000000000379eaa19dce8c9b722d46ae6a57c2f1a988119488b50931
         consensus.CSVHeight = 419328; // 000000000000000004a1b34462cb8aeebd5799177f7a29cf28f2d1961716b5b5
         consensus.SegwitHeight = 481824; // 0000000000000000001c8018d9cb3b742ef25114f27563e3fc4a1902167f9893
+        consensus.MinBIP9WarningHeight = consensus.SegwitHeight + consensus.nMinerConfirmationWindow;
         consensus.powLimit = uint256S("00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
         consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
         consensus.nPowTargetSpacing = 10 * 60;
@@ -177,6 +178,7 @@ class CTestNetParams : public CChainParams {
         consensus.BIP66Height = 330776; // 000000002104c8c45e99a8853285a3b592602a3ccde2b832481da85e9e4ba182
         consensus.CSVHeight = 770112; // 00000000025e930139bac5c6c31a403776da130831ab85be56578f3fa75369bb
         consensus.SegwitHeight = 834624; // 00000000002b980fcd729daaa248fd9316a5200e9b367f4ff2c42453e84201ca
+        consensus.MinBIP9WarningHeight = consensus.SegwitHeight + consensus.nMinerConfirmationWindow;
         consensus.powLimit = uint256S("00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
         consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
         consensus.nPowTargetSpacing = 10 * 60;
@@ -261,6 +263,7 @@ class CRegTestParams : public CChainParams {
         consensus.BIP66Height = 1251; // BIP66 activated on regtest (Used in functional tests)
         consensus.CSVHeight = 432; // CSV activated on regtest (Used in rpc activation tests)
         consensus.SegwitHeight = 0; // SEGWIT is always activated on regtest unless overridden
+        consensus.MinBIP9WarningHeight = 0;
         consensus.powLimit = uint256S("7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
         consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
         consensus.nPowTargetSpacing = 10 * 60;

src/consensus/params.h

@@ -62,6 +62,9 @@ struct Params {
      * Note that segwit v0 script rules are enforced on all blocks except the
      * BIP 16 exception blocks. */
     int SegwitHeight;
+    /** Don't warn about unknown BIP 9 activations below this height.
+     * This prevents us from warning about the CSV and segwit activations. */
+    int MinBIP9WarningHeight;
     /**
      * Minimum blocks including miner confirmation of the total of 2016 blocks in a retargeting period,
      * (nPowTargetTimespan / nPowTargetSpacing) which is also used for BIP9 deployments.

src/validation.cpp

@@ -1625,7 +1625,8 @@ class WarningBitsConditionChecker : public AbstractThresholdConditionChecker
 
     bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const override
     {
-        return ((pindex->nVersion & VERSIONBITS_TOP_MASK) == VERSIONBITS_TOP_BITS) &&
+        return pindex->nHeight >= params.MinBIP9WarningHeight &&
+               ((pindex->nVersion & VERSIONBITS_TOP_MASK) == VERSIONBITS_TOP_BITS) &&
                ((pindex->nVersion >> bit) & 1) != 0 &&
                ((ComputeBlockVersion(pindex->pprev, params) >> bit) & 1) == 0;
     }