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Merge #21083: wallet: Avoid requesting fee rates multiple times during coin selection

Browse Source 
f9cd2bfbcc Rename CoinSelectionParams::effective_fee to m_effective_feerate (Andrew Chow)
bdd0c2934b wallet: Move discard feerate fetching to CreateTransaction (Andrew Chow)
448d04b931 wallet: Move long term feerate setting to CreateTransaction (Andrew Chow)
e2f429e6bb wallet: Replace nFeeRateNeeded with effective_fee (Andrew Chow)
1a6a0b0dfb wallet: Use existing feerate instead of getting a new one (Andrew Chow)

Pull request description:

  During coin selection, there are various places where we need to have a feerate. We need the feerate for the transaction itself, the discard fee rate, and long term feerate. Fetching these each time we need them can lead to a race condition where two feerates that should be the same are actually different. One particular instance where this can happen is during the loop in `CreateTransactionInternal`. After inputs are chosen, the expected transaction fee is calculated using a newly fetched feerate. If `pick_new_inputs == false`, the loop will go again with the assumption that the fee for the transaction remains the same. However because the feerate is fetched again, it is possible that it actually isn't and this causes coin selection to fail.

  Instead of fetching the feerate each time it is needed, we fetch them all at once at the top of `CreateTransactionInternal`, store them in `CoinSelectionParams`, and use them where needed.

  While some of these fee rates probably don't need this caching, I've done it for consistency and the guarantee that they remain the same.

  Fixes #19229

ACKs for top commit:
  glozow:
    reACK f9cd2bfbcc
  fjahr:
    Code review re-ACK f9cd2bfbcc
  Xekyo:
    tACK f9cd2bfbcc
  meshcollider:
    Code review + test run ACK f9cd2bfbcc

Tree-SHA512: be83ff64ba473c3cdd3469c812e214659b6e2a9584c22ed2b1595618fce0d4b35d0901e61068cd1069fc1a8fb911db01dd7312d05c3b8cbafbe2504ab7a3e863
This commit is contained in:
Samuel Dobson
2021-03-17 11:46:08 +13:00
parent 5ef16038a1 f9cd2bfbcc
commit d25e28c20b
4 changed files with 53 additions and 35 deletions
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22
src/wallet/test/coinselector_tests.cpp
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@@ -35,7 +35,10 @@ static CAmount balance = 0;
CoinEligibilityFilter filter_standard(1, 6, 0);
CoinEligibilityFilter filter_confirmed(1, 1, 0);
CoinEligibilityFilter filter_standard_extra(6, 6, 0);
CoinSelectionParams coin_selection_params(false, 0, 0, CFeeRate(0), 0, false);
CoinSelectionParams coin_selection_params(/* use_bnb= */ false, /* change_output_size= */ 0,
/* change_spend_size= */ 0, /* effective_feerate= */ CFeeRate(0),
/* long_term_feerate= */ CFeeRate(0), /* discard_feerate= */ CFeeRate(0),
/* tx_no_inputs_size= */ 0, /* avoid_partial= */ false);
static void add_coin(const CAmount& nValue, int nInput, std::vector<CInputCoin>& set)
{
@@ -269,7 +272,10 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
}
// Make sure that effective value is working in SelectCoinsMinConf when BnB is used
CoinSelectionParams coin_selection_params_bnb(true, 0, 0, CFeeRate(3000), 0, false);
CoinSelectionParams coin_selection_params_bnb(/* use_bnb= */ true, /* change_output_size= */ 0,
/* change_spend_size= */ 0, /* effective_feerate= */ CFeeRate(3000),
/* long_term_feerate= */ CFeeRate(1000), /* discard_feerate= */ CFeeRate(1000),
/* tx_no_inputs_size= */ 0, /* avoid_partial= */ false);
CoinSet setCoinsRet;
CAmount nValueRet;
bool bnb_used;
@@ -301,7 +307,7 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
CCoinControl coin_control;
coin_control.fAllowOtherInputs = true;
coin_control.Select(COutPoint(vCoins.at(0).tx->GetHash(), vCoins.at(0).i));
coin_selection_params_bnb.effective_fee = CFeeRate(0);
coin_selection_params_bnb.m_effective_feerate = CFeeRate(0);
BOOST_CHECK(wallet->SelectCoins(vCoins, 10 * CENT, setCoinsRet, nValueRet, coin_control, coin_selection_params_bnb, bnb_used));
BOOST_CHECK(bnb_used);
BOOST_CHECK(coin_selection_params_bnb.use_bnb);
@@ -639,8 +645,14 @@ BOOST_AUTO_TEST_CASE(SelectCoins_test)
CAmount target = rand.randrange(balance - 1000) + 1000;
// Perform selection
CoinSelectionParams coin_selection_params_knapsack(false, 34, 148, CFeeRate(0), 0, false);
CoinSelectionParams coin_selection_params_bnb(true, 34, 148, CFeeRate(0), 0, false);
CoinSelectionParams coin_selection_params_knapsack(/* use_bnb= */ false, /* change_output_size= */ 34,
/* change_spend_size= */ 148, /* effective_feerate= */ CFeeRate(0),
/* long_term_feerate= */ CFeeRate(0), /* discard_feerate= */ CFeeRate(0),
/* tx_no_inputs_size= */ 0, /* avoid_partial= */ false);
CoinSelectionParams coin_selection_params_bnb(/* use_bnb= */ true, /* change_output_size= */ 34,
/* change_spend_size= */ 148, /* effective_feerate= */ CFeeRate(0),
/* long_term_feerate= */ CFeeRate(0), /* discard_feerate= */ CFeeRate(0),
/* tx_no_inputs_size= */ 0, /* avoid_partial= */ false);
CoinSet out_set;
CAmount out_value = 0;
bool bnb_used = false;