doc: explain AcceptToMemoryPoolWorker's coins_to_uncache
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@ -294,6 +294,10 @@ public:
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bool HaveInputs(const CTransaction& tx) const;
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private:
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/**
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* @note this is marked const, but may actually append to `cacheCoins`, increasing
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* memory usage.
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*/
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CCoinsMap::iterator FetchCoin(const COutPoint &outpoint) const;
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};
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@ -565,6 +565,13 @@ static bool CheckInputsFromMempoolAndCache(const CTransaction& tx, CValidationSt
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return CheckInputs(tx, state, view, true, flags, cacheSigStore, true, txdata);
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}
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/**
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* @param[out] coins_to_uncache Return any outpoints which were not previously present in the
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* coins cache, but were added as a result of validating the tx
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* for mempool acceptance. This allows the caller to optionally
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* remove the cache additions if the associated transaction ends
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* up being rejected by the mempool.
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*/
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static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool& pool, CValidationState& state, const CTransactionRef& ptx,
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bool* pfMissingInputs, int64_t nAcceptTime, std::list<CTransactionRef>* plTxnReplaced,
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bool bypass_limits, const CAmount& nAbsurdFee, std::vector<COutPoint>& coins_to_uncache, bool test_accept) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
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@ -660,6 +667,10 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
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if (!pcoinsTip->HaveCoinInCache(txin.prevout)) {
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coins_to_uncache.push_back(txin.prevout);
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}
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// Note: this call may add txin.prevout to the coins cache
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// (pcoinsTip.cacheCoins) by way of FetchCoin(). It should be removed
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// later (via coins_to_uncache) if this tx turns out to be invalid.
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if (!view.HaveCoin(txin.prevout)) {
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// Are inputs missing because we already have the tx?
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for (size_t out = 0; out < tx.vout.size(); out++) {
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@ -981,6 +992,11 @@ static bool AcceptToMemoryPoolWithTime(const CChainParams& chainparams, CTxMemPo
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std::vector<COutPoint> coins_to_uncache;
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bool res = AcceptToMemoryPoolWorker(chainparams, pool, state, tx, pfMissingInputs, nAcceptTime, plTxnReplaced, bypass_limits, nAbsurdFee, coins_to_uncache, test_accept);
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if (!res) {
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// Remove coins that were not present in the coins cache before calling ATMPW;
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// this is to prevent memory DoS in case we receive a large number of
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// invalid transactions that attempt to overrun the in-memory coins cache
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// (`CCoinsViewCache::cacheCoins`).
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for (const COutPoint& hashTx : coins_to_uncache)
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pcoinsTip->Uncache(hashTx);
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}
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