Merge bitcoin/bitcoin#27460: rpc: Add importmempool RPC

fa776e61cd64a5ffd9a4be589ab8efeb5421861a Add importmempool RPC (MarcoFalke)
fa20d734a29ba50cd19b78cb4fe39a2d826131b7 refactor: Add and use kernel::ImportMempoolOptions (MarcoFalke)
fa8866990dba7817427977bfe834efdb17114d37 doc: Clarify the getmempoolinfo.loaded RPC field documentation (MarcoFalke)
6888886cecf6665da70b3dc3772b3c12ef06ad76 Remove Chainstate::LoadMempool (MarcoFalke)

Pull request description:

  Currently it is possible to import a mempool by placing it in the datadir and starting the node. However this has many issues:

  * Users aren't expected to fiddle with the datadir, possibly corrupting it
  * An existing mempool file in the datadir may be overwritten
  * The node needs to be restarted
  * Importing an untrusted file this way is dangerous, because it can corrupt the mempool

  Fix all issues by adding a new RPC.

ACKs for top commit:
  ajtowns:
    utACK fa776e61cd64a5ffd9a4be589ab8efeb5421861a
  achow101:
    ACK fa776e61cd64a5ffd9a4be589ab8efeb5421861a
  glozow:
    reACK fa776e61cd64a5ffd9a4be589ab8efeb5421861a

Tree-SHA512: fcb1a92d6460839283c546c47a2d930c363ac1013c4c50dc5215ddf9fe5e51921d23fe0abfae0a5a7631983cfc7e2fff3788b70f95937d0a989a203be4d67546

11 files changed, 160 insertions, 32 deletions

diff --git a/src/init.cpp b/src/init.cpp
index 33389e695c..c2c4dbe459 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -116,6 +116,7 @@
 #endif
 
 using kernel::DumpMempool;
+using kernel::LoadMempool;
 using kernel::ValidationCacheSizes;
 
 using node::ApplyArgsManOptions;
@@ -1676,7 +1677,10 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
             return;
         }
         // Load mempool from disk
-        chainman.ActiveChainstate().LoadMempool(ShouldPersistMempool(args) ? MempoolPath(args) : fs::path{});
+        if (auto* pool{chainman.ActiveChainstate().GetMempool()}) {
+            LoadMempool(*pool, ShouldPersistMempool(args) ? MempoolPath(args) : fs::path{}, chainman.ActiveChainstate(), {});
+            pool->SetLoadTried(!chainman.m_interrupt);
+        }
     });
 
     // Wait for genesis block to be processed
diff --git a/src/kernel/mempool_persist.cpp b/src/kernel/mempool_persist.cpp
index d060e45af3..6be07da222 100644
--- a/src/kernel/mempool_persist.cpp
+++ b/src/kernel/mempool_persist.cpp
@@ -19,7 +19,6 @@
 #include <util/time.h>
 #include <validation.h>
 
-#include <chrono>
 #include <cstdint>
 #include <cstdio>
 #include <exception>
@@ -37,11 +36,11 @@ namespace kernel {
 
 static const uint64_t MEMPOOL_DUMP_VERSION = 1;
 
-bool LoadMempool(CTxMemPool& pool, const fs::path& load_path, Chainstate& active_chainstate, FopenFn mockable_fopen_function)
+bool LoadMempool(CTxMemPool& pool, const fs::path& load_path, Chainstate& active_chainstate, ImportMempoolOptions&& opts)
 {
     if (load_path.empty()) return false;
 
-    FILE* filestr{mockable_fopen_function(load_path, "rb")};
+    FILE* filestr{opts.mockable_fopen_function(load_path, "rb")};
     CAutoFile file(filestr, SER_DISK, CLIENT_VERSION);
     if (file.IsNull()) {
         LogPrintf("Failed to open mempool file from disk. Continuing anyway.\n");
@@ -53,7 +52,7 @@ bool LoadMempool(CTxMemPool& pool, const fs::path& load_path, Chainstate& active
     int64_t failed = 0;
     int64_t already_there = 0;
     int64_t unbroadcast = 0;
-    auto now = NodeClock::now();
+    const auto now{NodeClock::now()};
 
     try {
         uint64_t version;
@@ -72,8 +71,12 @@ bool LoadMempool(CTxMemPool& pool, const fs::path& load_path, Chainstate& active
             file >> nTime;
             file >> nFeeDelta;
 
+            if (opts.use_current_time) {
+                nTime = TicksSinceEpoch<std::chrono::seconds>(now);
+            }
+
             CAmount amountdelta = nFeeDelta;
-            if (amountdelta) {
+            if (amountdelta && opts.apply_fee_delta_priority) {
                 pool.PrioritiseTransaction(tx->GetHash(), amountdelta);
             }
             if (nTime > TicksSinceEpoch<std::chrono::seconds>(now - pool.m_expiry)) {
@@ -101,17 +104,21 @@ bool LoadMempool(CTxMemPool& pool, const fs::path& load_path, Chainstate& active
         std::map<uint256, CAmount> mapDeltas;
         file >> mapDeltas;
 
-        for (const auto& i : mapDeltas) {
-            pool.PrioritiseTransaction(i.first, i.second);
+        if (opts.apply_fee_delta_priority) {
+            for (const auto& i : mapDeltas) {
+                pool.PrioritiseTransaction(i.first, i.second);
+            }
         }
 
         std::set<uint256> unbroadcast_txids;
         file >> unbroadcast_txids;
-        unbroadcast = unbroadcast_txids.size();
-        for (const auto& txid : unbroadcast_txids) {
-            // Ensure transactions were accepted to mempool then add to
-            // unbroadcast set.
-            if (pool.get(txid) != nullptr) pool.AddUnbroadcastTx(txid);
+        if (opts.apply_unbroadcast_set) {
+            unbroadcast = unbroadcast_txids.size();
+            for (const auto& txid : unbroadcast_txids) {
+                // Ensure transactions were accepted to mempool then add to
+                // unbroadcast set.
+                if (pool.get(txid) != nullptr) pool.AddUnbroadcastTx(txid);
+            }
         }
     } catch (const std::exception& e) {
         LogPrintf("Failed to deserialize mempool data on disk: %s. Continuing anyway.\n", e.what());
diff --git a/src/kernel/mempool_persist.h b/src/kernel/mempool_persist.h
index cb09119e4a..e124a8eadf 100644
--- a/src/kernel/mempool_persist.h
+++ b/src/kernel/mempool_persist.h
@@ -12,15 +12,21 @@ class CTxMemPool;
 
 namespace kernel {
 
-/** Dump the mempool to disk. */
+/** Dump the mempool to a file. */
 bool DumpMempool(const CTxMemPool& pool, const fs::path& dump_path,
                  fsbridge::FopenFn mockable_fopen_function = fsbridge::fopen,
                  bool skip_file_commit = false);
 
-/** Load the mempool from disk. */
+struct ImportMempoolOptions {
+    fsbridge::FopenFn mockable_fopen_function{fsbridge::fopen};
+    bool use_current_time{false};
+    bool apply_fee_delta_priority{true};
+    bool apply_unbroadcast_set{true};
+};
+/** Import the file and attempt to add its contents to the mempool. */
 bool LoadMempool(CTxMemPool& pool, const fs::path& load_path,
                  Chainstate& active_chainstate,
-                 fsbridge::FopenFn mockable_fopen_function = fsbridge::fopen);
+                 ImportMempoolOptions&& opts);
 
 } // namespace kernel
 
diff --git a/src/rpc/client.cpp b/src/rpc/client.cpp
index d289a9240e..2908c37c1f 100644
--- a/src/rpc/client.cpp
+++ b/src/rpc/client.cpp
@@ -229,6 +229,10 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "importaddress", 2, "rescan" },
     { "importaddress", 3, "p2sh" },
     { "importpubkey", 2, "rescan" },
+    { "importmempool", 1, "options" },
+    { "importmempool", 1, "apply_fee_delta_priority" },
+    { "importmempool", 1, "use_current_time" },
+    { "importmempool", 1, "apply_unbroadcast_set" },
     { "importmulti", 0, "requests" },
     { "importmulti", 1, "options" },
     { "importmulti", 1, "rescan" },
diff --git a/src/rpc/mempool.cpp b/src/rpc/mempool.cpp
index 11d2874961..90ee2a48af 100644
--- a/src/rpc/mempool.cpp
+++ b/src/rpc/mempool.cpp
@@ -696,7 +696,7 @@ static RPCHelpMan getmempoolinfo()
         RPCResult{
             RPCResult::Type::OBJ, "", "",
             {
-                {RPCResult::Type::BOOL, "loaded", "True if the mempool is fully loaded"},
+                {RPCResult::Type::BOOL, "loaded", "True if the initial load attempt of the persisted mempool finished"},
                 {RPCResult::Type::NUM, "size", "Current tx count"},
                 {RPCResult::Type::NUM, "bytes", "Sum of all virtual transaction sizes as defined in BIP 141. Differs from actual serialized size because witness data is discounted"},
                 {RPCResult::Type::NUM, "usage", "Total memory usage for the mempool"},
@@ -719,6 +719,66 @@ static RPCHelpMan getmempoolinfo()
     };
 }
 
+static RPCHelpMan importmempool()
+{
+    return RPCHelpMan{
+        "importmempool",
+        "Import a mempool.dat file and attempt to add its contents to the mempool.\n"
+        "Warning: Importing untrusted files is dangerous, especially if metadata from the file is taken over.",
+        {
+            {"filepath", RPCArg::Type::STR, RPCArg::Optional::NO, "The mempool file"},
+            {"options",
+             RPCArg::Type::OBJ_NAMED_PARAMS,
+             RPCArg::Optional::OMITTED,
+             "",
+             {
+                 {"use_current_time", RPCArg::Type::BOOL, RPCArg::Default{true},
+                  "Whether to use the current system time or use the entry time metadata from the mempool file.\n"
+                  "Warning: Importing untrusted metadata may lead to unexpected issues and undesirable behavior."},
+                 {"apply_fee_delta_priority", RPCArg::Type::BOOL, RPCArg::Default{false},
+                  "Whether to apply the fee delta metadata from the mempool file.\n"
+                  "It will be added to any existing fee deltas.\n"
+                  "The fee delta can be set by the prioritisetransaction RPC.\n"
+                  "Warning: Importing untrusted metadata may lead to unexpected issues and undesirable behavior.\n"
+                  "Only set this bool if you understand what it does."},
+                 {"apply_unbroadcast_set", RPCArg::Type::BOOL, RPCArg::Default{false},
+                  "Whether to apply the unbroadcast set metadata from the mempool file.\n"
+                  "Warning: Importing untrusted metadata may lead to unexpected issues and undesirable behavior."},
+             },
+             RPCArgOptions{.oneline_description = "\"options\""}},
+        },
+        RPCResult{RPCResult::Type::OBJ, "", "", std::vector<RPCResult>{}},
+        RPCExamples{HelpExampleCli("importmempool", "/path/to/mempool.dat") + HelpExampleRpc("importmempool", "/path/to/mempool.dat")},
+        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue {
+            const NodeContext& node{EnsureAnyNodeContext(request.context)};
+
+            CTxMemPool& mempool{EnsureMemPool(node)};
+            Chainstate& chainstate = EnsureChainman(node).ActiveChainstate();
+
+            if (chainstate.IsInitialBlockDownload()) {
+                throw JSONRPCError(RPC_CLIENT_IN_INITIAL_DOWNLOAD, "Can only import the mempool after the block download and sync is done.");
+            }
+
+            const fs::path load_path{fs::u8path(request.params[0].get_str())};
+            const UniValue& use_current_time{request.params[1]["use_current_time"]};
+            const UniValue& apply_fee_delta{request.params[1]["apply_fee_delta_priority"]};
+            const UniValue& apply_unbroadcast{request.params[1]["apply_unbroadcast_set"]};
+            kernel::ImportMempoolOptions opts{
+                .use_current_time = use_current_time.isNull() ? true : use_current_time.get_bool(),
+                .apply_fee_delta_priority = apply_fee_delta.isNull() ? false : apply_fee_delta.get_bool(),
+                .apply_unbroadcast_set = apply_unbroadcast.isNull() ? false : apply_unbroadcast.get_bool(),
+            };
+
+            if (!kernel::LoadMempool(mempool, load_path, chainstate, std::move(opts))) {
+                throw JSONRPCError(RPC_MISC_ERROR, "Unable to import mempool file, see debug.log for details.");
+            }
+
+            UniValue ret{UniValue::VOBJ};
+            return ret;
+        },
+    };
+}
+
 static RPCHelpMan savemempool()
 {
     return RPCHelpMan{"savemempool",
@@ -921,6 +981,7 @@ void RegisterMempoolRPCCommands(CRPCTable& t)
         {"blockchain", &gettxspendingprevout},
         {"blockchain", &getmempoolinfo},
         {"blockchain", &getrawmempool},
+        {"blockchain", &importmempool},
         {"blockchain", &savemempool},
         {"hidden", &submitpackage},
     };
diff --git a/src/test/fuzz/rpc.cpp b/src/test/fuzz/rpc.cpp
index 2782888dc3..9e76c7be3e 100644
--- a/src/test/fuzz/rpc.cpp
+++ b/src/test/fuzz/rpc.cpp
@@ -78,6 +78,7 @@ const std::vector<std::string> RPC_COMMANDS_NOT_SAFE_FOR_FUZZING{
     "generatetoaddress",    // avoid prohibitively slow execution (when `num_blocks` is large)
     "generatetodescriptor", // avoid prohibitively slow execution (when `nblocks` is large)
     "gettxoutproof",        // avoid prohibitively slow execution
+    "importmempool", // avoid reading from disk
     "importwallet", // avoid reading from disk
     "loadwallet",   // avoid reading from disk
     "savemempool",           // disabled as a precautionary measure: may take a file path argument in the future
diff --git a/src/test/fuzz/validation_load_mempool.cpp b/src/test/fuzz/validation_load_mempool.cpp
index c203dd4e39..5d020b4d59 100644
--- a/src/test/fuzz/validation_load_mempool.cpp
+++ b/src/test/fuzz/validation_load_mempool.cpp
@@ -20,6 +20,7 @@
 #include <vector>
 
 using kernel::DumpMempool;
+using kernel::LoadMempool;
 
 using node::MempoolPath;
 
@@ -47,6 +48,10 @@ FUZZ_TARGET(validation_load_mempool, .init = initialize_validation_load_mempool)
     auto fuzzed_fopen = [&](const fs::path&, const char*) {
         return fuzzed_file_provider.open();
     };
-    (void)chainstate.LoadMempool(MempoolPath(g_setup->m_args), fuzzed_fopen);
+    (void)LoadMempool(pool, MempoolPath(g_setup->m_args), chainstate,
+                      {
+                          .mockable_fopen_function = fuzzed_fopen,
+                      });
+    pool.SetLoadTried(true);
     (void)DumpMempool(pool, MempoolPath(g_setup->m_args), fuzzed_fopen, true);
 }
diff --git a/src/txmempool.h b/src/txmempool.h
index a1867eb895..fa1dbbf4b5 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -663,13 +663,13 @@ public:
     void GetTransactionAncestry(const uint256& txid, size_t& ancestors, size_t& descendants, size_t* ancestorsize = nullptr, CAmount* ancestorfees = nullptr) const;
 
     /**
-     * @returns true if we've made an attempt to load the mempool regardless of
+     * @returns true if an initial attempt to load the persisted mempool was made, regardless of
      *          whether the attempt was successful or not
      */
     bool GetLoadTried() const;
 
     /**
-     * Set whether or not we've made an attempt to load the mempool (regardless
+     * Set whether or not an initial attempt to load the persisted mempool was made (regardless
      * of whether the attempt was successful or not)
      */
     void SetLoadTried(bool load_tried);
diff --git a/src/validation.cpp b/src/validation.cpp
index c45c847471..cec6d13181 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -69,7 +69,6 @@
 using kernel::CCoinsStats;
 using kernel::CoinStatsHashType;
 using kernel::ComputeUTXOStats;
-using kernel::LoadMempool;
 using kernel::Notifications;
 
 using fsbridge::FopenFn;
@@ -4126,13 +4125,6 @@ void PruneBlockFilesManual(Chainstate& active_chainstate, int nManualPruneHeight
     }
 }
 
-void Chainstate::LoadMempool(const fs::path& load_path, FopenFn mockable_fopen_function)
-{
-    if (!m_mempool) return;
-    ::LoadMempool(*m_mempool, load_path, *this, mockable_fopen_function);
-    m_mempool->SetLoadTried(!m_chainman.m_interrupt);
-}
-
 bool Chainstate::LoadChainTip()
 {
     AssertLockHeld(cs_main);
diff --git a/src/validation.h b/src/validation.h
index d7ad86a5e8..4c9f807f5d 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -712,9 +712,6 @@ public:
     /** Find the last common block of this chain and a locator. */
     const CBlockIndex* FindForkInGlobalIndex(const CBlockLocator& locator) const EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
-    /** Load the persisted mempool from disk */
-    void LoadMempool(const fs::path& load_path, fsbridge::FopenFn mockable_fopen_function = fsbridge::fopen);
-
     /** Update the chain tip based on database information, i.e. CoinsTip()'s best block. */
     bool LoadChainTip() EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
diff --git a/test/functional/mempool_persist.py b/test/functional/mempool_persist.py
index a1335ff069..32a927084a 100755
--- a/test/functional/mempool_persist.py
+++ b/test/functional/mempool_persist.py
@@ -46,7 +46,7 @@ from test_framework.util import (
     assert_greater_than_or_equal,
     assert_raises_rpc_error,
 )
-from test_framework.wallet import MiniWallet
+from test_framework.wallet import MiniWallet, COIN
 
 
 class MempoolPersistTest(BitcoinTestFramework):
@@ -159,6 +159,16 @@ class MempoolPersistTest(BitcoinTestFramework):
         assert self.nodes[0].getmempoolinfo()["loaded"]
         assert_equal(len(self.nodes[0].getrawmempool()), 0)
 
+        self.log.debug("Import mempool at runtime to node0.")
+        assert_equal({}, self.nodes[0].importmempool(mempooldat0))
+        assert_equal(len(self.nodes[0].getrawmempool()), 7)
+        fees = self.nodes[0].getmempoolentry(txid=last_txid)["fees"]
+        assert_equal(fees["base"], fees["modified"])
+        assert_equal({}, self.nodes[0].importmempool(mempooldat0, {"apply_fee_delta_priority": True, "apply_unbroadcast_set": True}))
+        assert_equal(2, self.nodes[0].getmempoolinfo()["unbroadcastcount"])
+        fees = self.nodes[0].getmempoolentry(txid=last_txid)["fees"]
+        assert_equal(fees["base"] + Decimal("0.00001000"), fees["modified"])
+
         self.log.debug("Stop-start node0. Verify that it has the transactions in its mempool.")
         self.stop_nodes()
         self.start_node(0)
@@ -186,6 +196,7 @@ class MempoolPersistTest(BitcoinTestFramework):
         assert_raises_rpc_error(-1, "Unable to dump mempool to disk", self.nodes[1].savemempool)
         os.rmdir(mempooldotnew1)
 
+        self.test_importmempool_union()
         self.test_persist_unbroadcast()
 
     def test_persist_unbroadcast(self):
@@ -210,6 +221,46 @@ class MempoolPersistTest(BitcoinTestFramework):
         node0.mockscheduler(16 * 60)  # 15 min + 1 for buffer
         self.wait_until(lambda: len(conn.get_invs()) == 1)
 
+    def test_importmempool_union(self):
+        self.log.debug("Submit different transactions to node0 and node1's mempools")
+        self.start_node(0)
+        self.start_node(2)
+        tx_node0 = self.mini_wallet.send_self_transfer(from_node=self.nodes[0])
+        tx_node1 = self.mini_wallet.send_self_transfer(from_node=self.nodes[1])
+        tx_node01 = self.mini_wallet.create_self_transfer()
+        tx_node01_secret = self.mini_wallet.create_self_transfer()
+        self.nodes[0].prioritisetransaction(tx_node01["txid"], 0, COIN)
+        self.nodes[0].prioritisetransaction(tx_node01_secret["txid"], 0, 2 * COIN)
+        self.nodes[1].prioritisetransaction(tx_node01_secret["txid"], 0, 3 * COIN)
+        self.nodes[0].sendrawtransaction(tx_node01["hex"])
+        self.nodes[1].sendrawtransaction(tx_node01["hex"])
+        assert tx_node0["txid"] in self.nodes[0].getrawmempool()
+        assert not tx_node0["txid"] in self.nodes[1].getrawmempool()
+        assert not tx_node1["txid"] in self.nodes[0].getrawmempool()
+        assert tx_node1["txid"] in self.nodes[1].getrawmempool()
+        assert tx_node01["txid"] in self.nodes[0].getrawmempool()
+        assert tx_node01["txid"] in self.nodes[1].getrawmempool()
+        assert not tx_node01_secret["txid"] in self.nodes[0].getrawmempool()
+        assert not tx_node01_secret["txid"] in self.nodes[1].getrawmempool()
+
+        self.log.debug("Check that importmempool can add txns without replacing the entire mempool")
+        mempooldat0 = str(self.nodes[0].chain_path / "mempool.dat")
+        result0 = self.nodes[0].savemempool()
+        assert_equal(mempooldat0, result0["filename"])
+        assert_equal({}, self.nodes[1].importmempool(mempooldat0, {"apply_fee_delta_priority": True}))
+        # All transactions should be in node1's mempool now.
+        assert tx_node0["txid"] in self.nodes[1].getrawmempool()
+        assert tx_node1["txid"] in self.nodes[1].getrawmempool()
+        assert not tx_node1["txid"] in self.nodes[0].getrawmempool()
+        # For transactions that already existed, priority should be changed
+        entry_node01 = self.nodes[1].getmempoolentry(tx_node01["txid"])
+        assert_equal(entry_node01["fees"]["base"] + 1, entry_node01["fees"]["modified"])
+        # Deltas for not-yet-submitted transactions should be applied as well (prioritisation is stackable).
+        self.nodes[1].sendrawtransaction(tx_node01_secret["hex"])
+        entry_node01_secret = self.nodes[1].getmempoolentry(tx_node01_secret["txid"])
+        assert_equal(entry_node01_secret["fees"]["base"] + 5, entry_node01_secret["fees"]["modified"])
+        self.stop_nodes()
+
 
 if __name__ == "__main__":
     MempoolPersistTest().main()