Merge #16713: Ignore old versionbit activations to avoid 'unknown softforks' warning

fdb3e8f8b2 Ignore old versionbit activations (Anthony Towns)

Pull request description:

  PR 16060 removed the CSV and Segwit BIP9 softfork definitions and hard-coded ('buried') the activation heights. The versionbits code will warn users if an undefined softfork has been signalled in block header versions, and removing the CSV/Segwit definitions caused those warnings to be triggered.

  Change the BIP 9 warning code to only check for unknown softforks after the segwit activation height.

ACKs for top commit:
  MarcoFalke:
    ACK fdb3e8f8b2
  ajtowns:
    ACK fdb3e8f8b2 for what it's worth
  achow101:
    ACK fdb3e8f8b2
  Sjors:
    ACK fdb3e8f8b2. It makes the bit 0 warning go away in mainnet and testnet QT when a new block arrives. I think the code is clear enough.
  jonatack:
    ACK fdb3e8f8b2

Tree-SHA512: e6fd34e8902f8c7affb28e8951803e47d542710d5f1229000746656a37ee59d754439fc33e36b7eef87544262e5aac374645db91b74cb507e73514003ca7a67f

src/chainparams.cpp

@@ -71,6 +71,7 @@ public:
         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 @@ public:
         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 @@ public:
         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

@@ -1821,7 +1821,8 @@ public:
 
     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;
     }