Add regtest-only -nurejectoldversions option

This enables us to write RPC tests for network upgrades before they have
been activated on testnet.

src/init.cpp

@@ -437,6 +437,7 @@ std::string HelpMessage(HelpMessageMode mode)
         strUsage += HelpMessageOpt("-fuzzmessagestest=<n>", "Randomly fuzz 1 of every <n> network messages");
         strUsage += HelpMessageOpt("-stopafterblockimport", strprintf("Stop running after importing blocks from disk (default: %u)", DEFAULT_STOPAFTERBLOCKIMPORT));
         strUsage += HelpMessageOpt("-nuparams=hexBranchId:activationHeight", "Use given activation height for specified network upgrade (regtest-only)");
+        strUsage += HelpMessageOpt("-nurejectoldversions", strprintf("Reject peers that don't know about the current epoch (regtest-only) (default: %u)", DEFAULT_NU_REJECT_OLD_VERSIONS));
     }
     string debugCategories = "addrman, alert, bench, coindb, db, estimatefee, http, libevent, lock, mempool, net, partitioncheck, pow, proxy, prune, "
                              "rand, reindex, rpc, selectcoins, tor, zmq, zrpc, zrpcunsafe (implies zrpc)"; // Don't translate these
@@ -1083,6 +1084,12 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
         }
     }
 
+    if (mapArgs.count("-nurejectoldversions")) {
+        if (Params().NetworkIDString() != "regtest") {
+            return InitError("-nurejectoldversions may only be set on regtest.");
+        }
+    }
+
     // ********************************************************* Step 4: application initialization: dir lock, daemonize, pidfile, debug log
 
     // Initialize libsodium

src/main.cpp

@@ -5349,8 +5349,12 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         // Reject incoming connections from nodes that don't know about the current epoch
         const Consensus::Params& consensusParams = chainparams.GetConsensus();
         auto currentEpoch = CurrentEpoch(GetHeight(), consensusParams);
-        if (pfrom->nVersion < consensusParams.vUpgrades[currentEpoch].nProtocolVersion)
-        {
+        if (pfrom->nVersion < consensusParams.vUpgrades[currentEpoch].nProtocolVersion &&
+            !(
+                chainparams.NetworkIDString() == "regtest" &&
+                !GetBoolArg("-nurejectoldversions", DEFAULT_NU_REJECT_OLD_VERSIONS)
+            )
+        ) {
             LogPrintf("peer=%d using obsolete version %i; disconnecting\n", pfrom->id, pfrom->nVersion);
             pfrom->PushMessage("reject", strCommand, REJECT_OBSOLETE,
                             strprintf("Version must be %d or greater",
@@ -5482,8 +5486,12 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
     // 1. The version message has been received
     // 2. Peer version is below the minimum version for the current epoch
     else if (pfrom->nVersion < chainparams.GetConsensus().vUpgrades[
-        CurrentEpoch(GetHeight(), chainparams.GetConsensus())].nProtocolVersion)
-    {
+        CurrentEpoch(GetHeight(), chainparams.GetConsensus())].nProtocolVersion &&
+        !(
+            chainparams.NetworkIDString() == "regtest" &&
+            !GetBoolArg("-nurejectoldversions", DEFAULT_NU_REJECT_OLD_VERSIONS)
+        )
+    ) {
         LogPrintf("peer=%d using obsolete version %i; disconnecting\n", pfrom->id, pfrom->nVersion);
         pfrom->PushMessage("reject", strCommand, REJECT_OBSOLETE,
                             strprintf("Version must be %d or greater",

src/main.h

@@ -111,6 +111,9 @@ static const bool DEFAULT_CHECKPOINTS_ENABLED = true;
 static const bool DEFAULT_TXINDEX = false;
 static const unsigned int DEFAULT_BANSCORE_THRESHOLD = 100;
 
+/** Default for -nurejectoldversions */
+static const bool DEFAULT_NU_REJECT_OLD_VERSIONS = true;
+
 #define equihash_parameters_acceptable(N, K) \
     ((CBlockHeader::HEADER_SIZE + equihash_solution_size(N, K))*MAX_HEADERS_RESULTS < \
      MAX_PROTOCOL_MESSAGE_LENGTH-1000)

src/net.cpp

@@ -832,7 +832,12 @@ static bool AttemptToEvictConnection(bool fPreferNewConnection) {
         {
             // Find any nodes which don't support the protocol version for the next upgrade
             for (const CNodeRef &node : vEvictionCandidates) {
-                if (node->nVersion < params.vUpgrades[idx].nProtocolVersion) {
+                if (node->nVersion < params.vUpgrades[idx].nProtocolVersion &&
+                    !(
+                        Params().NetworkIDString() == "regtest" &&
+                        !GetBoolArg("-nurejectoldversions", DEFAULT_NU_REJECT_OLD_VERSIONS)
+                    )
+                ) {
                     vTmpEvictionCandidates.push_back(node);
                 }
             }