From 6ba892126d354219b146f0c7f35d472f9c14bdac Mon Sep 17 00:00:00 2001 From: glozow Date: Thu, 22 Apr 2021 06:17:21 -0700 Subject: refactor + document coin selection strategy Co-authored-by: Xekyo --- src/wallet/wallet.cpp | 63 ++++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 50 insertions(+), 13 deletions(-) (limited to 'src/wallet/wallet.cpp') diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp index 332e7b1397..f0aaee7e4e 100644 --- a/src/wallet/wallet.cpp +++ b/src/wallet/wallet.cpp @@ -2478,7 +2478,7 @@ bool CWallet::SelectCoins(const std::vector& vAvailableCoins, const CAm } } - // remove preset inputs from vCoins + // remove preset inputs from vCoins so that Coin Selection doesn't pick them. for (std::vector::iterator it = vCoins.begin(); it != vCoins.end() && coin_control.HasSelected();) { if (setPresetCoins.count(it->GetInputCoin())) @@ -2490,9 +2490,9 @@ bool CWallet::SelectCoins(const std::vector& vAvailableCoins, const CAm unsigned int limit_ancestor_count = 0; unsigned int limit_descendant_count = 0; chain().getPackageLimits(limit_ancestor_count, limit_descendant_count); - size_t max_ancestors = (size_t)std::max(1, limit_ancestor_count); - size_t max_descendants = (size_t)std::max(1, limit_descendant_count); - bool fRejectLongChains = gArgs.GetBoolArg("-walletrejectlongchains", DEFAULT_WALLET_REJECT_LONG_CHAINS); + const size_t max_ancestors = (size_t)std::max(1, limit_ancestor_count); + const size_t max_descendants = (size_t)std::max(1, limit_descendant_count); + const bool fRejectLongChains = gArgs.GetBoolArg("-walletrejectlongchains", DEFAULT_WALLET_REJECT_LONG_CHAINS); // form groups from remaining coins; note that preset coins will not // automatically have their associated (same address) coins included @@ -2502,16 +2502,53 @@ bool CWallet::SelectCoins(const std::vector& vAvailableCoins, const CAm // explicitly shuffling the outputs before processing Shuffle(vCoins.begin(), vCoins.end(), FastRandomContext()); } - bool res = value_to_select <= 0 || - SelectCoinsMinConf(value_to_select, CoinEligibilityFilter(1, 6, 0), vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used) || - SelectCoinsMinConf(value_to_select, CoinEligibilityFilter(1, 1, 0), vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used) || - (m_spend_zero_conf_change && SelectCoinsMinConf(value_to_select, CoinEligibilityFilter(0, 1, 2), vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used)) || - (m_spend_zero_conf_change && SelectCoinsMinConf(value_to_select, CoinEligibilityFilter(0, 1, std::min((size_t)4, max_ancestors/3), std::min((size_t)4, max_descendants/3)), vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used)) || - (m_spend_zero_conf_change && SelectCoinsMinConf(value_to_select, CoinEligibilityFilter(0, 1, max_ancestors/2, max_descendants/2), vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used)) || - (m_spend_zero_conf_change && SelectCoinsMinConf(value_to_select, CoinEligibilityFilter(0, 1, max_ancestors-1, max_descendants-1, true /* include_partial_groups */), vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used)) || - (m_spend_zero_conf_change && !fRejectLongChains && SelectCoinsMinConf(value_to_select, CoinEligibilityFilter(0, 1, std::numeric_limits::max(), std::numeric_limits::max(), true /* include_partial_groups */), vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used)); - // because SelectCoinsMinConf clears the setCoinsRet, we now add the possible inputs to the coinset + // Coin Selection attempts to select inputs from a pool of eligible UTXOs to fund the + // transaction at a target feerate. If an attempt fails, more attempts may be made using a more + // permissive CoinEligibilityFilter. + const bool res = [&] { + // Pre-selected inputs already cover the target amount. + if (value_to_select <= 0) return true; + + // If possible, fund the transaction with confirmed UTXOs only. Prefer at least six + // confirmations on outputs received from other wallets and only spend confirmed change. + if (SelectCoinsMinConf(value_to_select, CoinEligibilityFilter(1, 6, 0), vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used)) return true; + if (SelectCoinsMinConf(value_to_select, CoinEligibilityFilter(1, 1, 0), vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used)) return true; + + // Fall back to using zero confirmation change (but with as few ancestors in the mempool as + // possible) if we cannot fund the transaction otherwise. We never spend unconfirmed + // outputs received from other wallets. + if (m_spend_zero_conf_change) { + if (SelectCoinsMinConf(value_to_select, CoinEligibilityFilter(0, 1, 2), vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used)) return true; + if (SelectCoinsMinConf(value_to_select, CoinEligibilityFilter(0, 1, std::min((size_t)4, max_ancestors/3), std::min((size_t)4, max_descendants/3)), + vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used)) { + return true; + } + if (SelectCoinsMinConf(value_to_select, CoinEligibilityFilter(0, 1, max_ancestors/2, max_descendants/2), + vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used)) { + return true; + } + // If partial groups are allowed, relax the requirement of spending OutputGroups (groups + // of UTXOs sent to the same address, which are obviously controlled by a single wallet) + // in their entirety. + if (SelectCoinsMinConf(value_to_select, CoinEligibilityFilter(0, 1, max_ancestors-1, max_descendants-1, true /* include_partial_groups */), + vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used)) { + return true; + } + // Try with unlimited ancestors/descendants. The transaction will still need to meet + // mempool ancestor/descendant policy to be accepted to mempool and broadcasted, but + // OutputGroups use heuristics that may overestimate ancestor/descendant counts. + if (!fRejectLongChains && SelectCoinsMinConf(value_to_select, + CoinEligibilityFilter(0, 1, std::numeric_limits::max(), std::numeric_limits::max(), true /* include_partial_groups */), + vCoins, setCoinsRet, nValueRet, coin_selection_params, bnb_used)) { + return true; + } + } + // Coin Selection failed. + return false; + }(); + + // SelectCoinsMinConf clears setCoinsRet, so add the preset inputs from coin_control to the coinset util::insert(setCoinsRet, setPresetCoins); // add preset inputs to the total value selected -- cgit v1.2.3