Add 'invalidateblock' and 'reconsiderblock' RPC commands.

These can be used for testing reorganizations or for manual intervention in case of
chain forks.

src/rpcblockchain.cpp

@@ -561,3 +561,79 @@ Value getmempoolinfo(const Array& params, bool fHelp)
     return ret;
 }
 
+Value invalidateblock(const Array& params, bool fHelp)
+{
+    if (fHelp || params.size() != 1)
+        throw runtime_error(
+            "invalidateblock \"hash\"\n"
+            "\nPermanently marks a block as invalid, as if it violated a consensus rule.\n"
+            "\nArguments:\n"
+            "1. hash   (string, required) the hash of the block to mark as invalid\n"
+            "\nResult:\n"
+            "\nExamples:\n"
+            + HelpExampleCli("invalidateblock", "\"blockhash\"")
+            + HelpExampleRpc("invalidateblock", "\"blockhash\"")
+        );
+
+    std::string strHash = params[0].get_str();
+    uint256 hash(strHash);
+    CValidationState state;
+
+    {
+        LOCK(cs_main);
+        if (mapBlockIndex.count(hash) == 0)
+            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
+
+        CBlockIndex* pblockindex = mapBlockIndex[hash];
+        InvalidateBlock(state, pblockindex);
+    }
+
+    if (state.IsValid()) {
+        ActivateBestChain(state);
+    }
+
+    if (!state.IsValid()) {
+        throw JSONRPCError(RPC_DATABASE_ERROR, state.GetRejectReason());
+    }
+
+    return Value::null;
+}
+
+Value reconsiderblock(const Array& params, bool fHelp)
+{
+    if (fHelp || params.size() != 1)
+        throw runtime_error(
+            "reconsiderblock \"hash\"\n"
+            "\nRemoves invalidity status of a block and its descendants, reconsider them for activation.\n"
+            "This can be used to undo the effects of invalidateblock.\n"
+            "\nArguments:\n"
+            "1. hash   (string, required) the hash of the block to reconsider\n"
+            "\nResult:\n"
+            "\nExamples:\n"
+            + HelpExampleCli("reconsiderblock", "\"blockhash\"")
+            + HelpExampleRpc("reconsiderblock", "\"blockhash\"")
+        );
+
+    std::string strHash = params[0].get_str();
+    uint256 hash(strHash);
+    CValidationState state;
+
+    {
+        LOCK(cs_main);
+        if (mapBlockIndex.count(hash) == 0)
+            throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
+
+        CBlockIndex* pblockindex = mapBlockIndex[hash];
+        ReconsiderBlock(state, pblockindex);
+    }
+
+    if (state.IsValid()) {
+        ActivateBestChain(state);
+    }
+
+    if (!state.IsValid()) {
+        throw JSONRPCError(RPC_DATABASE_ERROR, state.GetRejectReason());
+    }
+
+    return Value::null;
+}