Active reward scripts with the staking vault.

This implements ActiveProtocol, to actually activate the protocol
change for custom reward scripts outside of regtest (where it is
already activated from the start).

The activation will happen together with the planned staking-vault
fork, i.e. when 95% of blocks are version 5 or above.  This makes sure
that the upgrade happens only when the network has largely updated to
a new code version.

Author: domob1812

divi/src/main.cpp

@@ -5103,15 +5103,23 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
     return true;
 }
 
-// Note: whenever a protocol update is needed toggle between both implementations (comment out the formerly active one)
-//       so we can leave the existing clients untouched (old SPORK will stay on so they don't see even older clients).
-//       Those old clients won't react to the changes of the other (new) SPORK because at the time of their implementation
-//       it was the one which was commented out
 int ActiveProtocol()
 {
+    /* On regtest, we set the new protocol as active without any further
+       ado.  This allows proper testing of the changed logic.  */
     if (Params().NetworkID() == CBaseChainParams::REGTEST)
         return MN_REWARD_SCRIPT_VERSION;
 
+    /* Otherwise, the protocol update is tied to activation of the "staking vault"
+       fork, which happens by supermajority with block version 5.  */
+    const CBlockIndex* tip;
+    {
+        LOCK(cs_main);
+        tip = chainActive.Tip();
+    }
+    if (tip != nullptr && IsSuperMajority(5, tip, Params().RejectBlockOutdatedMajority()))
+        return MN_REWARD_SCRIPT_VERSION;
+
     return MIN_PEER_PROTO_VERSION_AFTER_ENFORCEMENT;
 }