diff --git a/doc/release-notes.md b/doc/release-notes.md
index 7608585a42..fcd5ae3f3e 100644
--- a/doc/release-notes.md
+++ b/doc/release-notes.md
@@ -1,12 +1,13 @@
 Bitcoin ABC version 0.20.2 is now available from:
 
   <https://download.bitcoinabc.org/0.20.2/>
 
 This release includes the following features and fixes:
  - Improved initial block download performance by ~20%.
  - Improved initial block download performance during pruning.
  - `bitcoin-qt -resetguisettings` now generates a backup of the former GUI settings.
  - Removed features that were deprecated in 0.19.x, including `signrawtransaction`,
    `fundrawtransaction -reserveChangeKey`, parts of `validateaddress`, use of
    addresses in `createmultisig`, and other miscellaneous behaviors.
  - Minor logging improvements.
+ - Introduced `submitheader` RPC for submitting header candidates as chaintips.
diff --git a/src/core_io.h b/src/core_io.h
index 8e59d5558f..cd2977e17f 100644
--- a/src/core_io.h
+++ b/src/core_io.h
@@ -1,38 +1,40 @@
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_CORE_IO_H
 #define BITCOIN_CORE_IO_H
 
 #include <string>
 #include <vector>
 
 struct Amount;
 class CBlock;
+class CBlockHeader;
 class CMutableTransaction;
 class CScript;
 class CTransaction;
 class uint256;
 class UniValue;
 
 // core_read.cpp
 CScript ParseScript(const std::string &s);
 std::string ScriptToAsmStr(const CScript &script,
                            const bool fAttemptSighashDecode = false);
 bool DecodeHexTx(CMutableTransaction &tx, const std::string &strHexTx);
 bool DecodeHexBlk(CBlock &, const std::string &strHexBlk);
+bool DecodeHexBlockHeader(CBlockHeader &, const std::string &hex_header);
 uint256 ParseHashUV(const UniValue &v, const std::string &strName);
 uint256 ParseHashStr(const std::string &, const std::string &strName);
 std::vector<uint8_t> ParseHexUV(const UniValue &v, const std::string &strName);
 
 // core_write.cpp
 UniValue ValueFromAmount(const Amount &amount);
 std::string FormatScript(const CScript &script);
 std::string EncodeHexTx(const CTransaction &tx, const int serializeFlags = 0);
 void ScriptPubKeyToUniv(const CScript &scriptPubKey, UniValue &out,
                         bool fIncludeHex);
 void TxToUniv(const CTransaction &tx, const uint256 &hashBlock, UniValue &entry,
               bool include_hex = true, int serialize_flags = 0);
 
 #endif // BITCOIN_CORE_IO_H
diff --git a/src/core_read.cpp b/src/core_read.cpp
index 7becc526ad..7166cc5b31 100644
--- a/src/core_read.cpp
+++ b/src/core_read.cpp
@@ -1,252 +1,267 @@
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <core_io.h>
 
 #include <primitives/block.h>
 #include <primitives/transaction.h>
 #include <script/script.h>
 #include <serialize.h>
 #include <streams.h>
 #include <util.h>
 #include <utilstrencodings.h>
 #include <version.h>
 
 #include <boost/algorithm/string/classification.hpp>
 #include <boost/algorithm/string/predicate.hpp>
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/algorithm/string/split.hpp>
 
 #include <univalue.h>
 
 CScript ParseScript(const std::string &s) {
     CScript result;
 
     static std::map<std::string, opcodetype> mapOpNames;
 
     if (mapOpNames.empty()) {
         for (int op = 0; op < FIRST_UNDEFINED_OP_VALUE; op++) {
             if (op < OP_PUSHDATA1) {
                 continue;
             }
 
             const char *name = GetOpName(static_cast<opcodetype>(op));
             if (strcmp(name, "OP_UNKNOWN") == 0) {
                 continue;
             }
 
             std::string strName(name);
             mapOpNames[strName] = static_cast<opcodetype>(op);
             // Convenience: OP_ADD and just ADD are both recognized:
             boost::algorithm::replace_first(strName, "OP_", "");
             mapOpNames[strName] = static_cast<opcodetype>(op);
         }
     }
 
     std::vector<std::string> words;
     boost::algorithm::split(words, s, boost::algorithm::is_any_of(" \t\n"),
                             boost::algorithm::token_compress_on);
 
     size_t push_size = 0, next_push_size = 0;
     size_t script_size = 0;
     // Deal with PUSHDATA1 operation with some more hacks.
     size_t push_data_size = 0;
 
     for (const auto &w : words) {
         if (w.empty()) {
             // Empty string, ignore. (boost::split given '' will return one
             // word)
             continue;
         }
 
         // Update script size.
         script_size = result.size();
 
         // Make sure we keep track of the size of push operations.
         push_size = next_push_size;
         next_push_size = 0;
 
         // Decimal numbers
         if (all(w, boost::algorithm::is_digit()) ||
             (boost::algorithm::starts_with(w, "-") &&
              all(std::string(w.begin() + 1, w.end()),
                  boost::algorithm::is_digit()))) {
             // Number
             int64_t n = atoi64(w);
             result << n;
             goto next;
         }
 
         // Hex Data
         if (boost::algorithm::starts_with(w, "0x") &&
             (w.begin() + 2 != w.end())) {
             if (!IsHex(std::string(w.begin() + 2, w.end()))) {
                 // Should only arrive here for improperly formatted hex values
                 throw std::runtime_error("Hex numbers expected to be formatted "
                                          "in full-byte chunks (ex: 0x00 "
                                          "instead of 0x0)");
             }
 
             // Raw hex data, inserted NOT pushed onto stack:
             std::vector<uint8_t> raw =
                 ParseHex(std::string(w.begin() + 2, w.end()));
 
             result.insert(result.end(), raw.begin(), raw.end());
             goto next;
         }
 
         if (w.size() >= 2 && boost::algorithm::starts_with(w, "'") &&
             boost::algorithm::ends_with(w, "'")) {
             // Single-quoted string, pushed as data. NOTE: this is poor-man's
             // parsing, spaces/tabs/newlines in single-quoted strings won't
             // work.
             std::vector<uint8_t> value(w.begin() + 1, w.end() - 1);
             result << value;
             goto next;
         }
 
         if (mapOpNames.count(w)) {
             // opcode, e.g. OP_ADD or ADD:
             opcodetype op = mapOpNames[w];
 
             result << op;
             goto next;
         }
 
         throw std::runtime_error("Error parsing script: " + s);
 
     next:
         size_t size_change = result.size() - script_size;
 
         // If push_size is set, ensure have added the right amount of stuff.
         if (push_size != 0 && size_change != push_size) {
             throw std::runtime_error(
                 "Wrong number of bytes being pushed. Expected:" +
                 std::to_string(push_size) +
                 " Pushed:" + std::to_string(size_change));
         }
 
         // If push_size is set, and we have push_data_size set, then we have a
         // PUSHDATAX opcode.  We need to read it's push size as a LE value for
         // the next iteration of this loop.
         if (push_size != 0 && push_data_size != 0) {
             auto offset = &result[script_size];
 
             // Push data size is not a CScriptNum (Because it is
             // 2's-complement instead of 1's complement).  We need to use
             // ReadLE(N) instead of converting to a CScriptNum.
             if (push_data_size == 1) {
                 next_push_size = *offset;
             } else if (push_data_size == 2) {
                 next_push_size = ReadLE16(offset);
             } else if (push_data_size == 4) {
                 next_push_size = ReadLE32(offset);
             }
 
             push_data_size = 0;
         }
 
         // If push_size is unset, but size_change is 1, that means we have an
         // opcode in the form of `0x00` or <opcodename>.  We will check to see
         // if it is a push operation and set state accordingly
         if (push_size == 0 && size_change == 1) {
             opcodetype op = opcodetype(*result.rbegin());
 
             // If we have what looks like an immediate push, figure out its
             // size.
             if (op < OP_PUSHDATA1) {
                 next_push_size = op;
                 continue;
             }
 
             switch (op) {
                 case OP_PUSHDATA1:
                     push_data_size = next_push_size = 1;
                     break;
                 case OP_PUSHDATA2:
                     push_data_size = next_push_size = 2;
                     break;
                 case OP_PUSHDATA4:
                     push_data_size = next_push_size = 4;
                     break;
                 default:
                     break;
             }
         }
     }
 
     return result;
 }
 
 bool DecodeHexTx(CMutableTransaction &tx, const std::string &strHexTx) {
     if (!IsHex(strHexTx)) {
         return false;
     }
 
     std::vector<uint8_t> txData(ParseHex(strHexTx));
 
     CDataStream ssData(txData, SER_NETWORK, PROTOCOL_VERSION);
     try {
         ssData >> tx;
         if (!ssData.empty()) {
             return false;
         }
     } catch (const std::exception &) {
         return false;
     }
 
     return true;
 }
 
+bool DecodeHexBlockHeader(CBlockHeader &header, const std::string &hex_header) {
+    if (!IsHex(hex_header)) {
+        return false;
+    }
+
+    const std::vector<uint8_t> header_data{ParseHex(hex_header)};
+    CDataStream ser_header(header_data, SER_NETWORK, PROTOCOL_VERSION);
+    try {
+        ser_header >> header;
+    } catch (const std::exception &) {
+        return false;
+    }
+    return true;
+}
+
 bool DecodeHexBlk(CBlock &block, const std::string &strHexBlk) {
     if (!IsHex(strHexBlk)) {
         return false;
     }
 
     std::vector<uint8_t> blockData(ParseHex(strHexBlk));
     CDataStream ssBlock(blockData, SER_NETWORK, PROTOCOL_VERSION);
     try {
         ssBlock >> block;
     } catch (const std::exception &) {
         return false;
     }
 
     return true;
 }
 
 uint256 ParseHashUV(const UniValue &v, const std::string &strName) {
     std::string strHex;
     if (v.isStr()) {
         strHex = v.getValStr();
     }
 
     // Note: ParseHashStr("") throws a runtime_error
     return ParseHashStr(strHex, strName);
 }
 
 uint256 ParseHashStr(const std::string &strHex, const std::string &strName) {
     if (!IsHex(strHex)) {
         // Note: IsHex("") is false
         throw std::runtime_error(
             strName + " must be hexadecimal string (not '" + strHex + "')");
     }
 
     uint256 result;
     result.SetHex(strHex);
     return result;
 }
 
 std::vector<uint8_t> ParseHexUV(const UniValue &v, const std::string &strName) {
     std::string strHex;
     if (v.isStr()) {
         strHex = v.getValStr();
     }
 
     if (!IsHex(strHex)) {
         throw std::runtime_error(
             strName + " must be hexadecimal string (not '" + strHex + "')");
     }
 
     return ParseHex(strHex);
 }
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index 409e3d1e8c..e0817f11e9 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -1,795 +1,839 @@
 // Copyright (c) 2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <amount.h>
 #include <blockvalidity.h>
 #include <chain.h>
 #include <chainparams.h>
 #include <config.h>
 #include <consensus/consensus.h>
 #include <consensus/params.h>
 #include <consensus/validation.h>
 #include <core_io.h>
 #include <init.h>
 #include <key_io.h>
 #include <miner.h>
 #include <net.h>
 #include <policy/policy.h>
 #include <pow.h>
 #include <rpc/blockchain.h>
 #include <rpc/mining.h>
 #include <rpc/server.h>
 #include <txmempool.h>
 #include <util.h>
 #include <utilstrencodings.h>
 #include <validation.h>
 #include <validationinterface.h>
 #include <warnings.h>
 
 #include <univalue.h>
 
 #include <cstdint>
 #include <memory>
 
 /**
  * Return average network hashes per second based on the last 'lookup' blocks,
  * or from the last difficulty change if 'lookup' is nonpositive. If 'height' is
  * nonnegative, compute the estimate at the time when a given block was found.
  */
 static UniValue GetNetworkHashPS(int lookup, int height) {
     CBlockIndex *pb = chainActive.Tip();
 
     if (height >= 0 && height < chainActive.Height()) {
         pb = chainActive[height];
     }
 
     if (pb == nullptr || !pb->nHeight) {
         return 0;
     }
 
     // If lookup is -1, then use blocks since last difficulty change.
     if (lookup <= 0) {
         lookup = pb->nHeight %
                      Params().GetConsensus().DifficultyAdjustmentInterval() +
                  1;
     }
 
     // If lookup is larger than chain, then set it to chain length.
     if (lookup > pb->nHeight) {
         lookup = pb->nHeight;
     }
 
     CBlockIndex *pb0 = pb;
     int64_t minTime = pb0->GetBlockTime();
     int64_t maxTime = minTime;
     for (int i = 0; i < lookup; i++) {
         pb0 = pb0->pprev;
         int64_t time = pb0->GetBlockTime();
         minTime = std::min(time, minTime);
         maxTime = std::max(time, maxTime);
     }
 
     // In case there's a situation where minTime == maxTime, we don't want a
     // divide by zero exception.
     if (minTime == maxTime) {
         return 0;
     }
 
     arith_uint256 workDiff = pb->nChainWork - pb0->nChainWork;
     int64_t timeDiff = maxTime - minTime;
 
     return workDiff.getdouble() / timeDiff;
 }
 
 static UniValue getnetworkhashps(const Config &config,
                                  const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 2) {
         throw std::runtime_error(
             "getnetworkhashps ( nblocks height )\n"
             "\nReturns the estimated network hashes per second based on the "
             "last n blocks.\n"
             "Pass in [blocks] to override # of blocks, -1 specifies since last "
             "difficulty change.\n"
             "Pass in [height] to estimate the network speed at the time when a "
             "certain block was found.\n"
             "\nArguments:\n"
             "1. nblocks     (numeric, optional, default=120) The number of "
             "blocks, or -1 for blocks since last difficulty change.\n"
             "2. height      (numeric, optional, default=-1) To estimate at the "
             "time of the given height.\n"
             "\nResult:\n"
             "x             (numeric) Hashes per second estimated\n"
             "\nExamples:\n" +
             HelpExampleCli("getnetworkhashps", "") +
             HelpExampleRpc("getnetworkhashps", ""));
     }
 
     LOCK(cs_main);
     return GetNetworkHashPS(
         !request.params[0].isNull() ? request.params[0].get_int() : 120,
         !request.params[1].isNull() ? request.params[1].get_int() : -1);
 }
 
 UniValue generateBlocks(const Config &config,
                         std::shared_ptr<CReserveScript> coinbaseScript,
                         int nGenerate, uint64_t nMaxTries, bool keepScript) {
     static const int nInnerLoopCount = 0x100000;
     int nHeightEnd = 0;
     int nHeight = 0;
 
     {
         // Don't keep cs_main locked.
         LOCK(cs_main);
         nHeight = chainActive.Height();
         nHeightEnd = nHeight + nGenerate;
     }
 
     unsigned int nExtraNonce = 0;
     UniValue blockHashes(UniValue::VARR);
     while (nHeight < nHeightEnd && !ShutdownRequested()) {
         std::unique_ptr<CBlockTemplate> pblocktemplate(
             BlockAssembler(config, g_mempool)
                 .CreateNewBlock(coinbaseScript->reserveScript));
 
         if (!pblocktemplate.get()) {
             throw JSONRPCError(RPC_INTERNAL_ERROR, "Couldn't create new block");
         }
 
         CBlock *pblock = &pblocktemplate->block;
 
         {
             LOCK(cs_main);
             IncrementExtraNonce(config, pblock, chainActive.Tip(), nExtraNonce);
         }
 
         while (nMaxTries > 0 && pblock->nNonce < nInnerLoopCount &&
                !CheckProofOfWork(pblock->GetHash(), pblock->nBits,
                                  config.GetChainParams().GetConsensus())) {
             ++pblock->nNonce;
             --nMaxTries;
         }
 
         if (nMaxTries == 0) {
             break;
         }
 
         if (pblock->nNonce == nInnerLoopCount) {
             continue;
         }
 
         std::shared_ptr<const CBlock> shared_pblock =
             std::make_shared<const CBlock>(*pblock);
         if (!ProcessNewBlock(config, shared_pblock, true, nullptr)) {
             throw JSONRPCError(RPC_INTERNAL_ERROR,
                                "ProcessNewBlock, block not accepted");
         }
         ++nHeight;
         blockHashes.push_back(pblock->GetHash().GetHex());
 
         // Mark script as important because it was used at least for one
         // coinbase output if the script came from the wallet.
         if (keepScript) {
             coinbaseScript->KeepScript();
         }
     }
 
     return blockHashes;
 }
 
 static UniValue generatetoaddress(const Config &config,
                                   const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() < 2 ||
         request.params.size() > 3) {
         throw std::runtime_error(
             "generatetoaddress nblocks address (maxtries)\n"
             "\nMine blocks immediately to a specified address (before the RPC "
             "call returns)\n"
             "\nArguments:\n"
             "1. nblocks      (numeric, required) How many blocks are generated "
             "immediately.\n"
             "2. address      (string, required) The address to send the newly "
             "generated bitcoin to.\n"
             "3. maxtries     (numeric, optional) How many iterations to try "
             "(default = 1000000).\n"
             "\nResult:\n"
             "[ blockhashes ]     (array) hashes of blocks generated\n"
             "\nExamples:\n"
             "\nGenerate 11 blocks to myaddress\n" +
             HelpExampleCli("generatetoaddress", "11 \"myaddress\""));
     }
 
     int nGenerate = request.params[0].get_int();
     uint64_t nMaxTries = 1000000;
     if (!request.params[2].isNull()) {
         nMaxTries = request.params[2].get_int();
     }
 
     CTxDestination destination =
         DecodeDestination(request.params[1].get_str(), config.GetChainParams());
     if (!IsValidDestination(destination)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY,
                            "Error: Invalid address");
     }
 
     std::shared_ptr<CReserveScript> coinbaseScript =
         std::make_shared<CReserveScript>();
     coinbaseScript->reserveScript = GetScriptForDestination(destination);
 
     return generateBlocks(config, coinbaseScript, nGenerate, nMaxTries, false);
 }
 
 static UniValue getmininginfo(const Config &config,
                               const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 0) {
         throw std::runtime_error(
             "getmininginfo\n"
             "\nReturns a json object containing mining-related information."
             "\nResult:\n"
             "{\n"
             "  \"blocks\": nnn,             (numeric) The current block\n"
             "  \"currentblocksize\": nnn,   (numeric) The last block size\n"
             "  \"currentblocktx\": nnn,     (numeric) The last block "
             "transaction\n"
             "  \"difficulty\": xxx.xxxxx    (numeric) The current difficulty\n"
             "  \"networkhashps\": nnn,      (numeric) The network hashes per "
             "second\n"
             "  \"pooledtx\": n              (numeric) The size of the mempool\n"
             "  \"chain\": \"xxxx\",           (string) current network name as "
             "defined in BIP70 (main, test, regtest)\n"
             "  \"warnings\": \"...\"          (string) any network and "
             "blockchain warnings\n"
             "}\n"
             "\nExamples:\n" +
             HelpExampleCli("getmininginfo", "") +
             HelpExampleRpc("getmininginfo", ""));
     }
 
     LOCK(cs_main);
 
     UniValue obj(UniValue::VOBJ);
     obj.pushKV("blocks", int(chainActive.Height()));
     obj.pushKV("currentblocksize", uint64_t(nLastBlockSize));
     obj.pushKV("currentblocktx", uint64_t(nLastBlockTx));
     obj.pushKV("difficulty", double(GetDifficulty(chainActive.Tip())));
     obj.pushKV("blockprioritypercentage",
                uint8_t(gArgs.GetArg("-blockprioritypercentage",
                                     DEFAULT_BLOCK_PRIORITY_PERCENTAGE)));
     obj.pushKV("networkhashps", getnetworkhashps(config, request));
     obj.pushKV("pooledtx", uint64_t(g_mempool.size()));
     obj.pushKV("chain", config.GetChainParams().NetworkIDString());
     obj.pushKV("warnings", GetWarnings("statusbar"));
 
     return obj;
 }
 
 // NOTE: Unlike wallet RPC (which use BCH values), mining RPCs follow GBT (BIP
 // 22) in using satoshi amounts
 static UniValue prioritisetransaction(const Config &config,
                                       const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() != 3) {
         throw std::runtime_error(
             "prioritisetransaction <txid> <priority delta> <fee delta>\n"
             "Accepts the transaction into mined blocks at a higher (or lower) "
             "priority\n"
             "\nArguments:\n"
             "1. \"txid\"       (string, required) The transaction id.\n"
             "2. priority_delta (numeric, required) The priority to add or "
             "subtract.\n"
             "                  The transaction selection algorithm considers "
             "the tx as it would have a higher priority.\n"
             "                  (priority of a transaction is calculated: "
             "coinage * value_in_satoshis / txsize) \n"
             "3. fee_delta      (numeric, required) The fee value (in satoshis) "
             "to add (or subtract, if negative).\n"
             "                  The fee is not actually paid, only the "
             "algorithm for selecting transactions into a block\n"
             "                  considers the transaction as it would have paid "
             "a higher (or lower) fee.\n"
             "\nResult:\n"
             "true              (boolean) Returns true\n"
             "\nExamples:\n" +
             HelpExampleCli("prioritisetransaction", "\"txid\" 0.0 10000") +
             HelpExampleRpc("prioritisetransaction", "\"txid\", 0.0, 10000"));
     }
 
     LOCK(cs_main);
 
     uint256 hash = ParseHashStr(request.params[0].get_str(), "txid");
     Amount nAmount = request.params[2].get_int64() * SATOSHI;
 
     g_mempool.PrioritiseTransaction(hash, request.params[1].get_real(),
                                     nAmount);
     return true;
 }
 
 // NOTE: Assumes a conclusive result; if result is inconclusive, it must be
 // handled by caller
 static UniValue BIP22ValidationResult(const Config &config,
                                       const CValidationState &state) {
     if (state.IsValid()) {
         return NullUniValue;
     }
 
     if (state.IsError()) {
         throw JSONRPCError(RPC_VERIFY_ERROR, FormatStateMessage(state));
     }
 
     if (state.IsInvalid()) {
         std::string strRejectReason = state.GetRejectReason();
         if (strRejectReason.empty()) {
             return "rejected";
         }
         return strRejectReason;
     }
 
     // Should be impossible.
     return "valid?";
 }
 
 static UniValue getblocktemplate(const Config &config,
                                  const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 1) {
         throw std::runtime_error(
             "getblocktemplate ( TemplateRequest )\n"
             "\nIf the request parameters include a 'mode' key, that is used to "
             "explicitly select between the default 'template' request or a "
             "'proposal'.\n"
             "It returns data needed to construct a block to work on.\n"
             "For full specification, see BIPs 22, 23, 9, and 145:\n"
             "    "
             "https://github.com/bitcoin/bips/blob/master/bip-0022.mediawiki\n"
             "    "
             "https://github.com/bitcoin/bips/blob/master/bip-0023.mediawiki\n"
             "    "
             "https://github.com/bitcoin/bips/blob/master/"
             "bip-0009.mediawiki#getblocktemplate_changes\n"
             "    "
             "https://github.com/bitcoin/bips/blob/master/bip-0145.mediawiki\n"
 
             "\nArguments:\n"
             "1. template_request         (json object, optional) A json object "
             "in the following spec\n"
             "     {\n"
             "       \"mode\":\"template\"    (string, optional) This must be "
             "set to \"template\", \"proposal\" (see BIP 23), or omitted\n"
             "       \"capabilities\":[     (array, optional) A list of "
             "strings\n"
             "           \"support\"          (string) client side supported "
             "feature, 'longpoll', 'coinbasetxn', 'coinbasevalue', 'proposal', "
             "'serverlist', 'workid'\n"
             "           ,...\n"
             "       ]\n"
             "     }\n"
             "\n"
 
             "\nResult:\n"
             "{\n"
             "  \"version\" : n,                    (numeric) The preferred "
             "block version\n"
             "  \"previousblockhash\" : \"xxxx\",     (string) The hash of "
             "current highest block\n"
             "  \"transactions\" : [                (array) contents of "
             "non-coinbase transactions that should be included in the next "
             "block\n"
             "      {\n"
             "         \"data\" : \"xxxx\",             (string) transaction "
             "data encoded in hexadecimal (byte-for-byte)\n"
             "         \"txid\" : \"xxxx\",             (string) transaction id "
             "encoded in little-endian hexadecimal\n"
             "         \"hash\" : \"xxxx\",             (string) hash encoded "
             "in little-endian hexadecimal (including witness data)\n"
             "         \"depends\" : [                (array) array of numbers "
             "\n"
             "             n                          (numeric) transactions "
             "before this one (by 1-based index in 'transactions' list) that "
             "must be present in the final block if this one is\n"
             "             ,...\n"
             "         ],\n"
             "         \"fee\": n,                    (numeric) difference in "
             "value between transaction inputs and outputs (in satoshis); for "
             "coinbase transactions, this is a negative Number of the total "
             "collected block fees (ie, not including the block subsidy); if "
             "key is not present, fee is unknown and clients MUST NOT assume "
             "there isn't one\n"
             "         \"sigops\" : n,                (numeric) total SigOps "
             "cost, as counted for purposes of block limits; if key is not "
             "present, sigop cost is unknown and clients MUST NOT assume it is "
             "zero\n"
             "         \"required\" : true|false      (boolean) if provided and "
             "true, this transaction must be in the final block\n"
             "      }\n"
             "      ,...\n"
             "  ],\n"
             "  \"coinbaseaux\" : {                 (json object) data that "
             "should be included in the coinbase's scriptSig content\n"
             "      \"flags\" : \"xx\"                  (string) key name is to "
             "be ignored, and value included in scriptSig\n"
             "  },\n"
             "  \"coinbasevalue\" : n,              (numeric) maximum allowable "
             "input to coinbase transaction, including the generation award and "
             "transaction fees (in satoshis)\n"
             "  \"coinbasetxn\" : { ... },          (json object) information "
             "for coinbase transaction\n"
             "  \"target\" : \"xxxx\",                (string) The hash target\n"
             "  \"mintime\" : xxx,                  (numeric) The minimum "
             "timestamp appropriate for next block time in seconds since epoch "
             "(Jan 1 1970 GMT)\n"
             "  \"mutable\" : [                     (array of string) list of "
             "ways the block template may be changed \n"
             "     \"value\"                          (string) A way the block "
             "template may be changed, e.g. 'time', 'transactions', "
             "'prevblock'\n"
             "     ,...\n"
             "  ],\n"
             "  \"noncerange\" : \"00000000ffffffff\",(string) A range of valid "
             "nonces\n"
             "  \"sigoplimit\" : n,                 (numeric) limit of sigops "
             "in blocks\n"
             "  \"sizelimit\" : n,                  (numeric) limit of block "
             "size\n"
             "  \"curtime\" : ttt,                  (numeric) current timestamp "
             "in seconds since epoch (Jan 1 1970 GMT)\n"
             "  \"bits\" : \"xxxxxxxx\",              (string) compressed "
             "target of next block\n"
             "  \"height\" : n                      (numeric) The height of the "
             "next block\n"
             "}\n"
 
             "\nExamples:\n" +
             HelpExampleCli("getblocktemplate", "") +
             HelpExampleRpc("getblocktemplate", ""));
     }
 
     LOCK(cs_main);
 
     std::string strMode = "template";
     UniValue lpval = NullUniValue;
     std::set<std::string> setClientRules;
     if (!request.params[0].isNull()) {
         const UniValue &oparam = request.params[0].get_obj();
         const UniValue &modeval = find_value(oparam, "mode");
         if (modeval.isStr()) {
             strMode = modeval.get_str();
         } else if (modeval.isNull()) {
             /* Do nothing */
         } else {
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid mode");
         }
         lpval = find_value(oparam, "longpollid");
 
         if (strMode == "proposal") {
             const UniValue &dataval = find_value(oparam, "data");
             if (!dataval.isStr()) {
                 throw JSONRPCError(RPC_TYPE_ERROR,
                                    "Missing data String key for proposal");
             }
 
             CBlock block;
             if (!DecodeHexBlk(block, dataval.get_str())) {
                 throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                                    "Block decode failed");
             }
 
             uint256 hash = block.GetHash();
             const CBlockIndex *pindex = LookupBlockIndex(hash);
             if (pindex) {
                 if (pindex->IsValid(BlockValidity::SCRIPTS)) {
                     return "duplicate";
                 }
                 if (pindex->nStatus.isInvalid()) {
                     return "duplicate-invalid";
                 }
                 return "duplicate-inconclusive";
             }
 
             CBlockIndex *const pindexPrev = chainActive.Tip();
             // TestBlockValidity only supports blocks built on the current Tip
             if (block.hashPrevBlock != pindexPrev->GetBlockHash()) {
                 return "inconclusive-not-best-prevblk";
             }
             CValidationState state;
             TestBlockValidity(config, state, block, pindexPrev,
                               BlockValidationOptions(config)
                                   .withCheckPoW(false)
                                   .withCheckMerkleRoot(true));
             return BIP22ValidationResult(config, state);
         }
     }
 
     if (strMode != "template") {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid mode");
     }
 
     if (!g_connman) {
         throw JSONRPCError(
             RPC_CLIENT_P2P_DISABLED,
             "Error: Peer-to-peer functionality missing or disabled");
     }
 
     if (g_connman->GetNodeCount(CConnman::CONNECTIONS_ALL) == 0) {
         throw JSONRPCError(RPC_CLIENT_NOT_CONNECTED,
                            "Bitcoin is not connected!");
     }
 
     if (IsInitialBlockDownload()) {
         throw JSONRPCError(RPC_CLIENT_IN_INITIAL_DOWNLOAD,
                            "Bitcoin is downloading blocks...");
     }
 
     static unsigned int nTransactionsUpdatedLast;
 
     if (!lpval.isNull()) {
         // Wait to respond until either the best block changes, OR a minute has
         // passed and there are more transactions
         uint256 hashWatchedChain;
         std::chrono::steady_clock::time_point checktxtime;
         unsigned int nTransactionsUpdatedLastLP;
 
         if (lpval.isStr()) {
             // Format: <hashBestChain><nTransactionsUpdatedLast>
             std::string lpstr = lpval.get_str();
 
             hashWatchedChain.SetHex(lpstr.substr(0, 64));
             nTransactionsUpdatedLastLP = atoi64(lpstr.substr(64));
         } else {
             // NOTE: Spec does not specify behaviour for non-string longpollid,
             // but this makes testing easier
             hashWatchedChain = chainActive.Tip()->GetBlockHash();
             nTransactionsUpdatedLastLP = nTransactionsUpdatedLast;
         }
 
         // Release the wallet and main lock while waiting
         LEAVE_CRITICAL_SECTION(cs_main);
         {
             checktxtime =
                 std::chrono::steady_clock::now() + std::chrono::minutes(1);
 
             WAIT_LOCK(g_best_block_mutex, lock);
             while (g_best_block == hashWatchedChain && IsRPCRunning()) {
                 if (g_best_block_cv.wait_until(lock, checktxtime) ==
                     std::cv_status::timeout) {
                     // Timeout: Check transactions for update
                     if (g_mempool.GetTransactionsUpdated() !=
                         nTransactionsUpdatedLastLP) {
                         break;
                     }
                     checktxtime += std::chrono::seconds(10);
                 }
             }
         }
         ENTER_CRITICAL_SECTION(cs_main);
 
         if (!IsRPCRunning()) {
             throw JSONRPCError(RPC_CLIENT_NOT_CONNECTED, "Shutting down");
         }
         // TODO: Maybe recheck connections/IBD and (if something wrong) send an
         // expires-immediately template to stop miners?
     }
 
     // Update block
     static CBlockIndex *pindexPrev;
     static int64_t nStart;
     static std::unique_ptr<CBlockTemplate> pblocktemplate;
     if (pindexPrev != chainActive.Tip() ||
         (g_mempool.GetTransactionsUpdated() != nTransactionsUpdatedLast &&
          GetTime() - nStart > 5)) {
         // Clear pindexPrev so future calls make a new block, despite any
         // failures from here on
         pindexPrev = nullptr;
 
         // Store the pindexBest used before CreateNewBlock, to avoid races
         nTransactionsUpdatedLast = g_mempool.GetTransactionsUpdated();
         CBlockIndex *pindexPrevNew = chainActive.Tip();
         nStart = GetTime();
 
         // Create new block
         CScript scriptDummy = CScript() << OP_TRUE;
         pblocktemplate =
             BlockAssembler(config, g_mempool).CreateNewBlock(scriptDummy);
         if (!pblocktemplate) {
             throw JSONRPCError(RPC_OUT_OF_MEMORY, "Out of memory");
         }
 
         // Need to update only after we know CreateNewBlock succeeded
         pindexPrev = pindexPrevNew;
     }
 
     assert(pindexPrev);
     // pointer for convenience
     CBlock *pblock = &pblocktemplate->block;
 
     // Update nTime
     UpdateTime(pblock, config.GetChainParams().GetConsensus(), pindexPrev);
     pblock->nNonce = 0;
 
     UniValue aCaps(UniValue::VARR);
     aCaps.push_back("proposal");
 
     UniValue transactions(UniValue::VARR);
     int index_in_template = 0;
     for (const auto &it : pblock->vtx) {
         const CTransaction &tx = *it;
         uint256 txId = tx.GetId();
 
         if (tx.IsCoinBase()) {
             index_in_template++;
             continue;
         }
 
         UniValue entry(UniValue::VOBJ);
         entry.pushKV("data", EncodeHexTx(tx));
         entry.pushKV("txid", txId.GetHex());
         entry.pushKV("hash", tx.GetHash().GetHex());
         entry.pushKV("fee", pblocktemplate->entries[index_in_template].txFee /
                                 SATOSHI);
         int64_t nTxSigOps = pblocktemplate->entries[index_in_template].txSigOps;
         entry.pushKV("sigops", nTxSigOps);
 
         transactions.push_back(entry);
         index_in_template++;
     }
 
     UniValue aux(UniValue::VOBJ);
     aux.pushKV("flags", HexStr(COINBASE_FLAGS.begin(), COINBASE_FLAGS.end()));
 
     arith_uint256 hashTarget = arith_uint256().SetCompact(pblock->nBits);
 
     UniValue aMutable(UniValue::VARR);
     aMutable.push_back("time");
     aMutable.push_back("transactions");
     aMutable.push_back("prevblock");
 
     UniValue result(UniValue::VOBJ);
     result.pushKV("capabilities", aCaps);
 
     result.pushKV("version", pblock->nVersion);
 
     result.pushKV("previousblockhash", pblock->hashPrevBlock.GetHex());
     result.pushKV("transactions", transactions);
     result.pushKV("coinbaseaux", aux);
     result.pushKV("coinbasevalue",
                   int64_t(pblock->vtx[0]->vout[0].nValue / SATOSHI));
     result.pushKV("longpollid", chainActive.Tip()->GetBlockHash().GetHex() +
                                     i64tostr(nTransactionsUpdatedLast));
     result.pushKV("target", hashTarget.GetHex());
     result.pushKV("mintime", int64_t(pindexPrev->GetMedianTimePast()) + 1);
     result.pushKV("mutable", aMutable);
     result.pushKV("noncerange", "00000000ffffffff");
     // FIXME: Allow for mining block greater than 1M.
     result.pushKV("sigoplimit", GetMaxBlockSigOpsCount(DEFAULT_MAX_BLOCK_SIZE));
     result.pushKV("sizelimit", DEFAULT_MAX_BLOCK_SIZE);
     result.pushKV("curtime", pblock->GetBlockTime());
     result.pushKV("bits", strprintf("%08x", pblock->nBits));
     result.pushKV("height", int64_t(pindexPrev->nHeight) + 1);
 
     return result;
 }
 
 class submitblock_StateCatcher : public CValidationInterface {
 public:
     uint256 hash;
     bool found;
     CValidationState state;
 
     explicit submitblock_StateCatcher(const uint256 &hashIn)
         : hash(hashIn), found(false), state() {}
 
 protected:
     void BlockChecked(const CBlock &block,
                       const CValidationState &stateIn) override {
         if (block.GetHash() != hash) {
             return;
         }
 
         found = true;
         state = stateIn;
     }
 };
 
 static UniValue submitblock(const Config &config,
                             const JSONRPCRequest &request) {
     // We allow 2 arguments for compliance with BIP22. Argument 2 is ignored.
     if (request.fHelp || request.params.size() < 1 ||
         request.params.size() > 2) {
         throw std::runtime_error(
             "submitblock \"hexdata\"  ( \"dummy\" )\n"
             "\nAttempts to submit new block to network.\n"
             "See https://en.bitcoin.it/wiki/BIP_0022 for full specification.\n"
 
             "\nArguments\n"
             "1. \"hexdata\"        (string, required) the hex-encoded block "
             "data to submit\n"
             "2. \"dummy\"          (optional) dummy value, for compatibility "
             "with BIP22. This value is ignored.\n"
             "\nResult:\n"
             "\nExamples:\n" +
             HelpExampleCli("submitblock", "\"mydata\"") +
             HelpExampleRpc("submitblock", "\"mydata\""));
     }
 
     std::shared_ptr<CBlock> blockptr = std::make_shared<CBlock>();
     CBlock &block = *blockptr;
     if (!DecodeHexBlk(block, request.params[0].get_str())) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Block decode failed");
     }
 
     if (block.vtx.empty() || !block.vtx[0]->IsCoinBase()) {
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
                            "Block does not start with a coinbase");
     }
 
     uint256 hash = block.GetHash();
     {
         LOCK(cs_main);
         const CBlockIndex *pindex = LookupBlockIndex(hash);
         if (pindex) {
             if (pindex->IsValid(BlockValidity::SCRIPTS)) {
                 return "duplicate";
             }
             if (pindex->nStatus.isInvalid()) {
                 return "duplicate-invalid";
             }
         }
     }
 
     bool new_block;
     submitblock_StateCatcher sc(block.GetHash());
     RegisterValidationInterface(&sc);
     bool accepted =
         ProcessNewBlock(config, blockptr, /* fForceProcessing */ true,
                         /* fNewBlock */ &new_block);
     UnregisterValidationInterface(&sc);
     if (!new_block) {
         if (!accepted) {
             // TODO Maybe pass down fNewBlock to AcceptBlockHeader, so it is
             // properly set to true in this case?
             return "invalid";
         }
         return "duplicate";
     }
 
     if (!sc.found) {
         return "inconclusive";
     }
 
     return BIP22ValidationResult(config, sc.state);
 }
 
+static UniValue submitheader(const Config &config,
+                             const JSONRPCRequest &request) {
+    if (request.fHelp || request.params.size() != 1) {
+        throw std::runtime_error("submitheader \"hexdata\"\n"
+                                 "\nDecode the given hexdata as a header and "
+                                 "submit it as a candidate chain tip if valid."
+                                 "\nThrows when the header is invalid.\n"
+                                 "\nArguments\n"
+                                 "1. \"hexdata\"        (string, required) the "
+                                 "hex-encoded block header data\n"
+                                 "\nResult:\n"
+                                 "None"
+                                 "\nExamples:\n" +
+                                 HelpExampleCli("submitheader", "\"aabbcc\"") +
+                                 HelpExampleRpc("submitheader", "\"aabbcc\""));
+    }
+
+    CBlockHeader h;
+    if (!DecodeHexBlockHeader(h, request.params[0].get_str())) {
+        throw JSONRPCError(RPC_DESERIALIZATION_ERROR,
+                           "Block header decode failed");
+    }
+    {
+        LOCK(cs_main);
+        if (!LookupBlockIndex(h.hashPrevBlock)) {
+            throw JSONRPCError(RPC_VERIFY_ERROR,
+                               "Must submit previous header (" +
+                                   h.hashPrevBlock.GetHex() + ") first");
+        }
+    }
+
+    CValidationState state;
+    ProcessNewBlockHeaders(config, {h}, state, /* ppindex */ nullptr,
+                           /* first_invalid */ nullptr);
+    if (state.IsValid()) {
+        return NullUniValue;
+    }
+    if (state.IsError()) {
+        throw JSONRPCError(RPC_VERIFY_ERROR, FormatStateMessage(state));
+    }
+    throw JSONRPCError(RPC_VERIFY_ERROR, state.GetRejectReason());
+}
+
 static UniValue estimatefee(const Config &config,
                             const JSONRPCRequest &request) {
     if (request.fHelp || request.params.size() > 0) {
         throw std::runtime_error(
             "estimatefee\n"
             "\nEstimates the approximate fee per kilobyte needed for a "
             "transaction\n"
             "\nResult:\n"
             "n              (numeric) estimated fee-per-kilobyte\n"
             "\nExample:\n" +
             HelpExampleCli("estimatefee", ""));
     }
 
     return ValueFromAmount(g_mempool.estimateFee().GetFeePerK());
 }
 
 // clang-format off
 static const ContextFreeRPCCommand commands[] = {
     //  category   name                     actor (function)       argNames
     //  ---------- ------------------------ ---------------------- ----------
     {"mining",     "getnetworkhashps",      getnetworkhashps,      {"nblocks", "height"}},
     {"mining",     "getmininginfo",         getmininginfo,         {}},
     {"mining",     "prioritisetransaction", prioritisetransaction, {"txid", "priority_delta", "fee_delta"}},
     {"mining",     "getblocktemplate",      getblocktemplate,      {"template_request"}},
     {"mining",     "submitblock",           submitblock,           {"hexdata", "dummy"}},
+    {"mining",     "submitheader",          submitheader,          {"hexdata"}},
 
     {"generating", "generatetoaddress",     generatetoaddress,     {"nblocks", "address", "maxtries"}},
 
     {"util",       "estimatefee",           estimatefee,           {"nblocks"}},
 };
 // clang-format on
 
 void RegisterMiningRPCCommands(CRPCTable &t) {
     for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++)
         t.appendCommand(commands[vcidx].name, &commands[vcidx]);
 }
diff --git a/test/functional/mining_basic.py b/test/functional/mining_basic.py
index edfd839dbe..d6c1885291 100755
--- a/test/functional/mining_basic.py
+++ b/test/functional/mining_basic.py
@@ -1,147 +1,228 @@
 #!/usr/bin/env python3
 # Copyright (c) 2014-2016 The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Test mining RPCs
 
 - getmininginfo
 - getblocktemplate proposal mode
 - submitblock"""
 
-from binascii import b2a_hex
 import copy
 from decimal import Decimal
 
 from test_framework.blocktools import create_coinbase
-from test_framework.messages import CBlock
+from test_framework.messages import (
+    CBlock,
+    CBlockHeader,
+)
+from test_framework.mininode import (
+    P2PDataStore,
+)
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal, assert_raises_rpc_error
-
-
-def b2x(b):
-    return b2a_hex(b).decode('ascii')
+from test_framework.util import (
+    assert_equal,
+    assert_raises_rpc_error,
+    bytes_to_hex_str as b2x,
+)
 
 
 def assert_template(node, block, expect, rehash=True):
     if rehash:
         block.hashMerkleRoot = block.calc_merkle_root()
     rsp = node.getblocktemplate(
         {'data': b2x(block.serialize()), 'mode': 'proposal'})
     assert_equal(rsp, expect)
 
 
 class MiningTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 2
         self.setup_clean_chain = False
 
     def run_test(self):
         node = self.nodes[0]
 
         self.log.info('getmininginfo')
         mining_info = node.getmininginfo()
         assert_equal(mining_info['blocks'], 200)
         assert_equal(mining_info['chain'], 'regtest')
         assert_equal(mining_info['currentblocksize'], 0)
         assert_equal(mining_info['currentblocktx'], 0)
         assert_equal(mining_info['difficulty'],
                      Decimal('4.656542373906925E-10'))
         assert_equal(mining_info['networkhashps'],
                      Decimal('0.003333333333333334'))
         assert_equal(mining_info['pooledtx'], 0)
 
         # Mine a block to leave initial block download
         node.generate(1)
         tmpl = node.getblocktemplate()
         self.log.info("getblocktemplate: Test capability advertised")
         assert 'proposal' in tmpl['capabilities']
         assert 'coinbasetxn' not in tmpl
 
         coinbase_tx = create_coinbase(height=int(tmpl["height"]) + 1)
         # sequence numbers must not be max for nLockTime to have effect
         coinbase_tx.vin[0].nSequence = 2 ** 32 - 2
         coinbase_tx.rehash()
 
         block = CBlock()
         block.nVersion = tmpl["version"]
         block.hashPrevBlock = int(tmpl["previousblockhash"], 16)
         block.nTime = tmpl["curtime"]
         block.nBits = int(tmpl["bits"], 16)
         block.nNonce = 0
         block.vtx = [coinbase_tx]
 
         self.log.info("getblocktemplate: Test valid block")
         assert_template(node, block, None)
 
         self.log.info("submitblock: Test block decode failure")
         assert_raises_rpc_error(-22, "Block decode failed",
                                 node.submitblock, b2x(block.serialize()[:-15]))
 
         self.log.info(
             "getblocktemplate: Test bad input hash for coinbase transaction")
         bad_block = copy.deepcopy(block)
         bad_block.vtx[0].vin[0].prevout.hash += 1
         bad_block.vtx[0].rehash()
         assert_template(node, bad_block, 'bad-cb-missing')
 
         self.log.info("submitblock: Test invalid coinbase transaction")
         assert_raises_rpc_error(-22, "Block does not start with a coinbase",
                                 node.submitblock, b2x(bad_block.serialize()))
 
         self.log.info("getblocktemplate: Test truncated final transaction")
         assert_raises_rpc_error(-22, "Block decode failed", node.getblocktemplate,
                                 {'data': b2x(block.serialize()[:-1]), 'mode': 'proposal'})
 
         self.log.info("getblocktemplate: Test duplicate transaction")
         bad_block = copy.deepcopy(block)
         bad_block.vtx.append(bad_block.vtx[0])
         assert_template(node, bad_block, 'bad-txns-duplicate')
 
         self.log.info("getblocktemplate: Test invalid transaction")
         bad_block = copy.deepcopy(block)
         bad_tx = copy.deepcopy(bad_block.vtx[0])
         bad_tx.vin[0].prevout.hash = 255
         bad_tx.rehash()
         bad_block.vtx.append(bad_tx)
         assert_template(node, bad_block, 'bad-txns-inputs-missingorspent')
 
         self.log.info("getblocktemplate: Test nonfinal transaction")
         bad_block = copy.deepcopy(block)
         bad_block.vtx[0].nLockTime = 2 ** 32 - 1
         bad_block.vtx[0].rehash()
         assert_template(node, bad_block, 'bad-txns-nonfinal')
 
         self.log.info("getblocktemplate: Test bad tx count")
         # The tx count is immediately after the block header
         TX_COUNT_OFFSET = 80
         bad_block_sn = bytearray(block.serialize())
         assert_equal(bad_block_sn[TX_COUNT_OFFSET], 1)
         bad_block_sn[TX_COUNT_OFFSET] += 1
         assert_raises_rpc_error(-22, "Block decode failed", node.getblocktemplate,
                                 {'data': b2x(bad_block_sn), 'mode': 'proposal'})
 
         self.log.info("getblocktemplate: Test bad bits")
         bad_block = copy.deepcopy(block)
         bad_block.nBits = 469762303  # impossible in the real world
         assert_template(node, bad_block, 'bad-diffbits')
 
         self.log.info("getblocktemplate: Test bad merkle root")
         bad_block = copy.deepcopy(block)
         bad_block.hashMerkleRoot += 1
         assert_template(node, bad_block, 'bad-txnmrklroot', False)
 
         self.log.info("getblocktemplate: Test bad timestamps")
         bad_block = copy.deepcopy(block)
         bad_block.nTime = 2 ** 31 - 1
         assert_template(node, bad_block, 'time-too-new')
         bad_block.nTime = 0
         assert_template(node, bad_block, 'time-too-old')
 
         self.log.info("getblocktemplate: Test not best block")
         bad_block = copy.deepcopy(block)
         bad_block.hashPrevBlock = 123
         assert_template(node, bad_block, 'inconclusive-not-best-prevblk')
 
+        self.log.info('submitheader tests')
+        assert_raises_rpc_error(-22, 'Block header decode failed',
+                                lambda: node.submitheader(hexdata='xx' * 80))
+        assert_raises_rpc_error(-22, 'Block header decode failed',
+                                lambda: node.submitheader(hexdata='ff' * 78))
+        assert_raises_rpc_error(-25, 'Must submit previous header',
+                                lambda: node.submitheader(hexdata='ff' * 80))
+
+        block.solve()
+
+        def chain_tip(b_hash, *, status='headers-only', branchlen=1):
+            return {'hash': b_hash, 'height': 202, 'branchlen': branchlen, 'status': status}
+
+        assert chain_tip(block.hash) not in node.getchaintips()
+        node.submitheader(hexdata=b2x(block.serialize()))
+        assert chain_tip(block.hash) in node.getchaintips()
+        # Noop
+        node.submitheader(hexdata=b2x(CBlockHeader(block).serialize()))
+        assert chain_tip(block.hash) in node.getchaintips()
+
+        bad_block_root = copy.deepcopy(block)
+        bad_block_root.hashMerkleRoot += 2
+        bad_block_root.solve()
+        assert chain_tip(bad_block_root.hash) not in node.getchaintips()
+        node.submitheader(hexdata=b2x(
+            CBlockHeader(bad_block_root).serialize()))
+        assert chain_tip(bad_block_root.hash) in node.getchaintips()
+        # Should still reject invalid blocks, even if we have the header:
+        assert_equal(node.submitblock(hexdata=b2x(
+            bad_block_root.serialize())), 'invalid')
+        assert chain_tip(bad_block_root.hash) in node.getchaintips()
+        # We know the header for this invalid block, so should just return early without error:
+        node.submitheader(hexdata=b2x(
+            CBlockHeader(bad_block_root).serialize()))
+        assert chain_tip(bad_block_root.hash) in node.getchaintips()
+
+        bad_block_lock = copy.deepcopy(block)
+        bad_block_lock.vtx[0].nLockTime = 2**32 - 1
+        bad_block_lock.vtx[0].rehash()
+        bad_block_lock.hashMerkleRoot = bad_block_lock.calc_merkle_root()
+        bad_block_lock.solve()
+        assert_equal(node.submitblock(hexdata=b2x(
+            bad_block_lock.serialize())), 'invalid')
+        # Build a "good" block on top of the submitted bad block
+        bad_block2 = copy.deepcopy(block)
+        bad_block2.hashPrevBlock = bad_block_lock.sha256
+        bad_block2.solve()
+        assert_raises_rpc_error(-25, 'bad-prevblk', lambda: node.submitheader(
+            hexdata=b2x(CBlockHeader(bad_block2).serialize())))
+
+        # Should reject invalid header right away
+        bad_block_time = copy.deepcopy(block)
+        bad_block_time.nTime = 1
+        bad_block_time.solve()
+        assert_raises_rpc_error(-25, 'time-too-old', lambda: node.submitheader(
+            hexdata=b2x(CBlockHeader(bad_block_time).serialize())))
+
+        # Should ask for the block from a p2p node, if they announce the header as well:
+        node.add_p2p_connection(P2PDataStore())
+        # Drop the first getheaders
+        node.p2p.wait_for_getheaders(timeout=5)
+        node.p2p.send_blocks_and_test(blocks=[block], node=node)
+        # Must be active now:
+        assert chain_tip(block.hash, status='active',
+                         branchlen=0) in node.getchaintips()
+
+        # Building a few blocks should give the same results
+        node.generate(10)
+        assert_raises_rpc_error(-25, 'time-too-old', lambda: node.submitheader(
+            hexdata=b2x(CBlockHeader(bad_block_time).serialize())))
+        assert_raises_rpc_error(-25, 'bad-prevblk', lambda: node.submitheader(
+            hexdata=b2x(CBlockHeader(bad_block2).serialize())))
+        node.submitheader(hexdata=b2x(CBlockHeader(block).serialize()))
+        node.submitheader(hexdata=b2x(
+            CBlockHeader(bad_block_root).serialize()))
+
 
 if __name__ == '__main__':
     MiningTest().main()