Add IsCurrentForFeeEstimatation

Make a more conservative notion of whether the node is caught up to the rest of the network and only count transactions as fee estimation data points if the node is caught up.

src/validation.cpp

@@ -525,6 +525,18 @@ std::string FormatStateMessage(const CValidationState &state)
         state.GetRejectCode());
 }
 
+static bool IsCurrentForFeeEstimation()
+{
+    AssertLockHeld(cs_main);
+    if (IsInitialBlockDownload())
+        return false;
+    if (chainActive.Tip()->GetBlockTime() < (GetTime() - MAX_FEE_ESTIMATION_TIP_AGE))
+        return false;
+    if (chainActive.Height() < pindexBestHeader->nHeight - 1)
+        return false;
+    return true;
+}
+
 bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const CTransactionRef& ptx, bool fLimitFree,
                               bool* pfMissingInputs, int64_t nAcceptTime, bool fOverrideMempoolLimit, const CAmount& nAbsurdFee,
                               std::vector<uint256>& vHashTxnToUncache)
@@ -941,8 +953,13 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
         }
         pool.RemoveStaged(allConflicting, false);
 
+        // This transaction should only count for fee estimation if
+        // the node is not behind and it is not dependent on any other
+        // transactions in the mempool
+        bool validForFeeEstimation = IsCurrentForFeeEstimation() && pool.HasNoInputsOf(tx);
+
         // Store transaction in memory
-        pool.addUnchecked(hash, entry, setAncestors, !IsInitialBlockDownload() && pool.HasNoInputsOf(tx));
+        pool.addUnchecked(hash, entry, setAncestors, validForFeeEstimation);
 
         // trim mempool and check if tx was trimmed
         if (!fOverrideMempoolLimit) {

src/validation.h

@@ -130,6 +130,8 @@ static const int64_t BLOCK_DOWNLOAD_TIMEOUT_PER_PEER = 500000;
 static const unsigned int DEFAULT_LIMITFREERELAY = 0;
 static const bool DEFAULT_RELAYPRIORITY = true;
 static const int64_t DEFAULT_MAX_TIP_AGE = 24 * 60 * 60;
+/** Maximum age of our tip for us to be considered current for fee estimation */
+static const int64_t MAX_FEE_ESTIMATION_TIP_AGE = 3 * 60 * 60;
 
 /** Default for -permitbaremultisig */
 static const bool DEFAULT_PERMIT_BAREMULTISIG = true;