Merge pull request #7296

bebe58b SQUASHME: Fix rpc tests that assumed fallback to minRelayTxFee (Alex Morcos)
e420a1b Add sane fallback for fee estimation (Alex Morcos)
995b9f3 Always respect GetRequiredFee for wallet txs (Alex Morcos)

4 files changed, 30 insertions, 10 deletions

diff --git a/src/init.cpp b/src/init.cpp
index 220df5ebf7..374e756abd 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -393,6 +393,8 @@ std::string HelpMessage(HelpMessageMode mode)
     strUsage += HelpMessageGroup(_("Wallet options:"));
     strUsage += HelpMessageOpt("-disablewallet", _("Do not load the wallet and disable wallet RPC calls"));
     strUsage += HelpMessageOpt("-keypool=<n>", strprintf(_("Set key pool size to <n> (default: %u)"), DEFAULT_KEYPOOL_SIZE));
+    strUsage += HelpMessageOpt("-fallbackfee=<amt>", strprintf(_("A fee rate (in %s/kB) that will be used when fee estimation has insufficient data (default: %s)"),
+        CURRENCY_UNIT, FormatMoney(DEFAULT_FALLBACK_FEE)));
     strUsage += HelpMessageOpt("-mintxfee=<amt>", strprintf(_("Fees (in %s/kB) smaller than this are considered zero fee for transaction creation (default: %s)"),
             CURRENCY_UNIT, FormatMoney(DEFAULT_TRANSACTION_MINFEE)));
     strUsage += HelpMessageOpt("-paytxfee=<amt>", strprintf(_("Fee (in %s/kB) to add to transactions you send (default: %s)"),
@@ -959,6 +961,15 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
         else
             return InitError(AmountErrMsg("mintxfee", mapArgs["-mintxfee"]));
     }
+    if (mapArgs.count("-fallbackfee"))
+    {
+        CAmount nFeePerK = 0;
+        if (!ParseMoney(mapArgs["-fallbackfee"], nFeePerK))
+            return InitError(strprintf(_("Invalid amount for -fallbackfee=<amount>: '%s'"), mapArgs["-fallbackfee"]));
+        if (nFeePerK > nHighTransactionFeeWarning)
+            InitWarning(_("-fallbackfee is set very high! This is the transaction fee you may pay when fee estimates are not available."));
+        CWallet::fallbackFee = CFeeRate(nFeePerK);
+    }
     if (mapArgs.count("-paytxfee"))
     {
         CAmount nFeePerK = 0;
diff --git a/src/qt/sendcoinsdialog.cpp b/src/qt/sendcoinsdialog.cpp
index 31c9028c4b..c834c3b564 100644
--- a/src/qt/sendcoinsdialog.cpp
+++ b/src/qt/sendcoinsdialog.cpp
@@ -640,13 +640,15 @@ void SendCoinsDialog::updateSmartFeeLabel()
     CFeeRate feeRate = mempool.estimateSmartFee(nBlocksToConfirm, &estimateFoundAtBlocks);
     if (feeRate <= CFeeRate(0)) // not enough data => minfee
     {
-        ui->labelSmartFee->setText(BitcoinUnits::formatWithUnit(model->getOptionsModel()->getDisplayUnit(), CWallet::GetRequiredFee(1000)) + "/kB");
+        ui->labelSmartFee->setText(BitcoinUnits::formatWithUnit(model->getOptionsModel()->getDisplayUnit(),
+                                                                std::max(CWallet::fallbackFee.GetFeePerK(), CWallet::GetRequiredFee(1000))) + "/kB");
         ui->labelSmartFee2->show(); // (Smart fee not initialized yet. This usually takes a few blocks...)
         ui->labelFeeEstimation->setText("");
     }
     else
     {
-        ui->labelSmartFee->setText(BitcoinUnits::formatWithUnit(model->getOptionsModel()->getDisplayUnit(), feeRate.GetFeePerK()) + "/kB");
+        ui->labelSmartFee->setText(BitcoinUnits::formatWithUnit(model->getOptionsModel()->getDisplayUnit(),
+                                                                std::max(feeRate.GetFeePerK(), CWallet::GetRequiredFee(1000))) + "/kB");
         ui->labelSmartFee2->hide();
         ui->labelFeeEstimation->setText(tr("Estimated to begin confirmation within %n block(s).", "", estimateFoundAtBlocks));
     }
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 1904361bae..6b2ebebba7 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -47,6 +47,12 @@ bool fSendFreeTransactions = DEFAULT_SEND_FREE_TRANSACTIONS;
  * Override with -mintxfee
  */
 CFeeRate CWallet::minTxFee = CFeeRate(DEFAULT_TRANSACTION_MINFEE);
+/**
+ * If fee estimation does not have enough data to provide estimates, use this fee instead.
+ * Has no effect if not using fee estimation
+ * Override with -fallbackfee
+ */
+CFeeRate CWallet::fallbackFee = CFeeRate(DEFAULT_FALLBACK_FEE);
 
 /** @defgroup mapWallet
  *
@@ -2230,14 +2236,12 @@ CAmount CWallet::GetMinimumFee(unsigned int nTxBytes, unsigned int nConfirmTarge
     if (nFeeNeeded == 0) {
         int estimateFoundTarget = nConfirmTarget;
         nFeeNeeded = pool.estimateSmartFee(nConfirmTarget, &estimateFoundTarget).GetFee(nTxBytes);
-        // ... unless we don't have enough mempool data for our desired target
-        // so we make sure we're paying at least minTxFee
-        if (nFeeNeeded == 0 || (unsigned int)estimateFoundTarget > nConfirmTarget)
-            nFeeNeeded = std::max(nFeeNeeded, GetRequiredFee(nTxBytes));
-    }
-    // prevent user from paying a non-sense fee (like 1 satoshi): 0 < fee < minRelayFee
-    if (nFeeNeeded < ::minRelayTxFee.GetFee(nTxBytes))
-        nFeeNeeded = ::minRelayTxFee.GetFee(nTxBytes);
+        // ... unless we don't have enough mempool data for estimatefee, then use fallbackFee
+        if (nFeeNeeded == 0)
+            nFeeNeeded = fallbackFee.GetFee(nTxBytes);
+    }
+    // prevent user from paying a fee below minRelayTxFee or minTxFee
+    nFeeNeeded = std::max(nFeeNeeded, GetRequiredFee(nTxBytes));
     // But always obey the maximum
     if (nFeeNeeded > maxTxFee)
         nFeeNeeded = maxTxFee;
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index a9d0c3f604..9bbd52f14c 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -41,6 +41,8 @@ static const unsigned int DEFAULT_KEYPOOL_SIZE = 100;
 static const CAmount DEFAULT_TRANSACTION_FEE = 0;
 //! -paytxfee will warn if called with a higher fee than this amount (in satoshis) per KB
 static const CAmount nHighTransactionFeeWarning = 0.01 * COIN;
+//! -fallbackfee default
+static const CAmount DEFAULT_FALLBACK_FEE = 20000;
 //! -mintxfee default
 static const CAmount DEFAULT_TRANSACTION_MINFEE = 1000;
 //! -maxtxfee default
@@ -745,6 +747,7 @@ public:
     bool AddAccountingEntry(const CAccountingEntry&, CWalletDB & pwalletdb);
 
     static CFeeRate minTxFee;
+    static CFeeRate fallbackFee;
     /**
      * Estimate the minimum fee considering user set parameters
      * and the required fee