message: Enforce correct port on mainnet for DIP3 MNs
diff: @@ -27,6 +27,15 @@ static bool CheckService(const uint256& proTxHash, const ProTx& proTx, CValidati
  return state.DoS(10, false, REJECT_INVALID, "bad-protx-addr");
  }
  + int mainnetDefaultPort = Params(CBaseChainParams::MAIN).GetDefaultPort();
  + if (Params().NetworkIDString() == CBaseChainParams::MAIN) {
  + if (proTx.addr.GetPort() != mainnetDefaultPort) {
  + return state.DoS(10, false, REJECT_INVALID, "bad-protx-addr-port");
  + }
  + } else if (proTx.addr.GetPort() == mainnetDefaultPort) {
  + return state.DoS(10, false, REJECT_INVALID, "bad-protx-addr-port");
  + }
  +
  if (!proTx.addr.IsIPv4()) {
  return state.DoS(10, false, REJECT_INVALID, "bad-protx-addr");
  }
  