Merge #16908: txmempool: Make entry time type-safe (std::chrono)

faec689bed7a5b66e2a7675853d10205b933cec8 txmempool: Make entry time type-safe (std::chrono) (MarcoFalke)
faaa1f01daba94b021ca77515266a16d27f0364e util: Add count_seconds time helper (MarcoFalke)
1111170f2f0141084b5b4ed565b2f07eba48599a test: mempool entry time is persisted (MarcoFalke)

Pull request description:

  This changes the type of the entry time of txs into the mempool from `int64_t` to `std::chrono::seconds`.

  The benefits:
  * Documents the type for developers
  * Type violations result in compile errors
  * After compilation, the two are equivalent (at no run time cost)

ACKs for top commit:
  ajtowns:
    utACK faec689bed7a5b66e2a7675853d10205b933cec8
  laanwj:
    ACK faec689bed7a5b66e2a7675853d10205b933cec8

Tree-SHA512: d958e058755d1a1d54cef536a8b30a11cc502b7df0d6ecf84a0ab1d38bc8105a67668a99cd5087a444f6de2421238111c5fca133cdf8e2e2273cb12cb6957845

7 files changed, 24 insertions, 15 deletions

diff --git a/src/net.h b/src/net.h
index f33147155a..44655abf80 100644
--- a/src/net.h
+++ b/src/net.h
@@ -761,7 +761,7 @@ public:
         // Used for BIP35 mempool sending
         bool fSendMempool GUARDED_BY(cs_tx_inventory){false};
         // Last time a "MEMPOOL" request was serviced.
-        std::atomic<int64_t> timeLastMempoolReq{0};
+        std::atomic<std::chrono::seconds> m_last_mempool_req{std::chrono::seconds{0}};
         int64_t nNextInvSend{0};
 
         CCriticalSection cs_feeFilter;
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 34d349e8e9..e345af604c 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -1541,11 +1541,11 @@ void static ProcessGetData(CNode* pfrom, const CChainParams& chainparams, CConnm
             if (mi != mapRelay.end()) {
                 connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *mi->second));
                 push = true;
-            } else if (pfrom->m_tx_relay->timeLastMempoolReq) {
+            } else if (pfrom->m_tx_relay->m_last_mempool_req.load().count()) {
                 auto txinfo = mempool.info(inv.hash);
                 // To protect privacy, do not answer getdata using the mempool when
                 // that TX couldn't have been INVed in reply to a MEMPOOL request.
-                if (txinfo.tx && txinfo.nTime <= pfrom->m_tx_relay->timeLastMempoolReq) {
+                if (txinfo.tx && txinfo.m_time <= pfrom->m_tx_relay->m_last_mempool_req.load()) {
                     connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *txinfo.tx));
                     push = true;
                 }
@@ -3873,7 +3873,7 @@ bool PeerLogicValidation::SendMessages(CNode* pto)
                             vInv.clear();
                         }
                     }
-                    pto->m_tx_relay->timeLastMempoolReq = GetTime();
+                    pto->m_tx_relay->m_last_mempool_req = GetTime<std::chrono::seconds>();
                 }
 
                 // Determine transactions to relay
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 02717fa80f..3463145f75 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -418,7 +418,7 @@ static void entryToJSON(const CTxMemPool& pool, UniValue& info, const CTxMemPool
     info.pushKV("weight", (int)e.GetTxWeight());
     info.pushKV("fee", ValueFromAmount(e.GetFee()));
     info.pushKV("modifiedfee", ValueFromAmount(e.GetModifiedFee()));
-    info.pushKV("time", e.GetTime());
+    info.pushKV("time", count_seconds(e.GetTime()));
     info.pushKV("height", (int)e.GetHeight());
     info.pushKV("descendantcount", e.GetCountWithDescendants());
     info.pushKV("descendantsize", e.GetSizeWithDescendants());
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index 9257cff718..835b8d63bd 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -917,7 +917,8 @@ void CTxMemPool::RemoveStaged(setEntries &stage, bool updateDescendants, MemPool
     }
 }
 
-int CTxMemPool::Expire(int64_t time) {
+int CTxMemPool::Expire(std::chrono::seconds time)
+{
     AssertLockHeld(cs);
     indexed_transaction_set::index<entry_time>::type::iterator it = mapTx.get<entry_time>().begin();
     setEntries toremove;
diff --git a/src/txmempool.h b/src/txmempool.h
index 6e5ba445d3..f2fc1c8310 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -102,7 +102,7 @@ public:
     const CAmount& GetFee() const { return nFee; }
     size_t GetTxSize() const;
     size_t GetTxWeight() const { return nTxWeight; }
-    int64_t GetTime() const { return nTime; }
+    std::chrono::seconds GetTime() const { return std::chrono::seconds{nTime}; }
     unsigned int GetHeight() const { return entryHeight; }
     int64_t GetSigOpCost() const { return sigOpCost; }
     int64_t GetModifiedFee() const { return nFee + feeDelta; }
@@ -332,7 +332,7 @@ struct TxMempoolInfo
     CTransactionRef tx;
 
     /** Time the transaction entered the mempool. */
-    int64_t nTime;
+    std::chrono::seconds m_time;
 
     /** Feerate of the transaction. */
     CFeeRate feeRate;
@@ -657,7 +657,7 @@ public:
     void TrimToSize(size_t sizelimit, std::vector<COutPoint>* pvNoSpendsRemaining = nullptr) EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /** Expire all transaction (and their dependencies) in the mempool older than time. Return the number of removed transactions. */
-    int Expire(int64_t time) EXCLUSIVE_LOCKS_REQUIRED(cs);
+    int Expire(std::chrono::seconds time) EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /**
      * Calculate the ancestor and descendant count for the given transaction.
diff --git a/src/util/time.h b/src/util/time.h
index e4f9996777..c0470a2136 100644
--- a/src/util/time.h
+++ b/src/util/time.h
@@ -11,6 +11,14 @@
 #include <chrono>
 
 /**
+ * Helper to count the seconds of a duration.
+ *
+ * All durations should be using std::chrono and calling this should generally be avoided in code. Though, it is still
+ * preferred to an inline t.count() to protect against a reliance on the exact type of t.
+ */
+inline int64_t count_seconds(std::chrono::seconds t) { return t.count(); }
+
+/**
  * DEPRECATED
  * Use either GetSystemTimeInSeconds (not mockable) or GetTime<T> (mockable)
  */
diff --git a/src/validation.cpp b/src/validation.cpp
index ac98bd61c7..726f251c5a 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -314,10 +314,10 @@ bool CheckSequenceLocks(const CTxMemPool& pool, const CTransaction& tx, int flag
 // Returns the script flags which should be checked for a given block
 static unsigned int GetBlockScriptFlags(const CBlockIndex* pindex, const Consensus::Params& chainparams);
 
-static void LimitMempoolSize(CTxMemPool& pool, size_t limit, unsigned long age)
+static void LimitMempoolSize(CTxMemPool& pool, size_t limit, std::chrono::seconds age)
     EXCLUSIVE_LOCKS_REQUIRED(pool.cs, ::cs_main)
 {
-    int expired = pool.Expire(GetTime() - age);
+    int expired = pool.Expire(GetTime<std::chrono::seconds>() - age);
     if (expired != 0) {
         LogPrint(BCLog::MEMPOOL, "Expired %i transactions from the memory pool\n", expired);
     }
@@ -389,7 +389,7 @@ static void UpdateMempoolForReorg(DisconnectedBlockTransactions& disconnectpool,
     // We also need to remove any now-immature transactions
     mempool.removeForReorg(&::ChainstateActive().CoinsTip(), ::ChainActive().Tip()->nHeight + 1, STANDARD_LOCKTIME_VERIFY_FLAGS);
     // Re-limit mempool size, in case we added any transactions
-    LimitMempoolSize(mempool, gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60);
+    LimitMempoolSize(mempool, gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, std::chrono::hours{gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY)});
 }
 
 // Used to avoid mempool polluting consensus critical paths if CCoinsViewMempool
@@ -1011,7 +1011,7 @@ bool MemPoolAccept::Finalize(ATMPArgs& args, Workspace& ws)
 
     // trim mempool and check if tx was trimmed
     if (!bypass_limits) {
-        LimitMempoolSize(m_pool, gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60);
+        LimitMempoolSize(m_pool, gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, std::chrono::hours{gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY)});
         if (!m_pool.exists(hash))
             return state.Invalid(ValidationInvalidReason::TX_MEMPOOL_POLICY, false, REJECT_INSUFFICIENTFEE, "mempool full");
     }
@@ -5041,8 +5041,8 @@ bool DumpMempool(const CTxMemPool& pool)
         file << (uint64_t)vinfo.size();
         for (const auto& i : vinfo) {
             file << *(i.tx);
-            file << (int64_t)i.nTime;
-            file << (int64_t)i.nFeeDelta;
+            file << int64_t{count_seconds(i.m_time)};
+            file << int64_t{i.nFeeDelta};
             mapDeltas.erase(i.tx->GetHash());
         }