1 files changed, 202 insertions, 0 deletions
diff --git a/src/txorphanage.cpp b/src/txorphanage.cpp
new file mode 100644
index 0000000000..ed4783f1a5
--- /dev/null
+++ b/src/txorphanage.cpp
@@ -0,0 +1,202 @@
+// Copyright (c) 2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <txorphanage.h>
+
+#include <consensus/validation.h>
+#include <logging.h>
+#include <policy/policy.h>
+
+#include <cassert>
+
+/** Expiration time for orphan transactions in seconds */
+static constexpr int64_t ORPHAN_TX_EXPIRE_TIME = 20 * 60;
+/** Minimum time between orphan transactions expire time checks in seconds */
+static constexpr int64_t ORPHAN_TX_EXPIRE_INTERVAL = 5 * 60;
+
+RecursiveMutex g_cs_orphans;
+
+bool TxOrphanage::AddTx(const CTransactionRef& tx, NodeId peer)
+{
+    AssertLockHeld(g_cs_orphans);
+
+    const uint256& hash = tx->GetHash();
+    if (m_orphans.count(hash))
+        return false;
+
+    // Ignore big transactions, to avoid a
+    // send-big-orphans memory exhaustion attack. If a peer has a legitimate
+    // large transaction with a missing parent then we assume
+    // it will rebroadcast it later, after the parent transaction(s)
+    // have been mined or received.
+    // 100 orphans, each of which is at most 100,000 bytes big is
+    // at most 10 megabytes of orphans and somewhat more byprev index (in the worst case):
+    unsigned int sz = GetTransactionWeight(*tx);
+    if (sz > MAX_STANDARD_TX_WEIGHT)
+    {
+        LogPrint(BCLog::MEMPOOL, "ignoring large orphan tx (size: %u, hash: %s)\n", sz, hash.ToString());
+        return false;
+    }
+
+    auto ret = m_orphans.emplace(hash, OrphanTx{tx, peer, GetTime() + ORPHAN_TX_EXPIRE_TIME, m_orphan_list.size()});
+    assert(ret.second);
+    m_orphan_list.push_back(ret.first);
+    // Allow for lookups in the orphan pool by wtxid, as well as txid
+    m_wtxid_to_orphan_it.emplace(tx->GetWitnessHash(), ret.first);
+    for (const CTxIn& txin : tx->vin) {
+        m_outpoint_to_orphan_it[txin.prevout].insert(ret.first);
+    }
+
+    LogPrint(BCLog::MEMPOOL, "stored orphan tx %s (mapsz %u outsz %u)\n", hash.ToString(),
+             m_orphans.size(), m_outpoint_to_orphan_it.size());
+    return true;
+}
+
+int TxOrphanage::EraseTx(const uint256& txid)
+{
+    AssertLockHeld(g_cs_orphans);
+    std::map<uint256, OrphanTx>::iterator it = m_orphans.find(txid);
+    if (it == m_orphans.end())
+        return 0;
+    for (const CTxIn& txin : it->second.tx->vin)
+    {
+        auto itPrev = m_outpoint_to_orphan_it.find(txin.prevout);
+        if (itPrev == m_outpoint_to_orphan_it.end())
+            continue;
+        itPrev->second.erase(it);
+        if (itPrev->second.empty())
+            m_outpoint_to_orphan_it.erase(itPrev);
+    }
+
+    size_t old_pos = it->second.list_pos;
+    assert(m_orphan_list[old_pos] == it);
+    if (old_pos + 1 != m_orphan_list.size()) {
+        // Unless we're deleting the last entry in m_orphan_list, move the last
+        // entry to the position we're deleting.
+        auto it_last = m_orphan_list.back();
+        m_orphan_list[old_pos] = it_last;
+        it_last->second.list_pos = old_pos;
+    }
+    m_orphan_list.pop_back();
+    m_wtxid_to_orphan_it.erase(it->second.tx->GetWitnessHash());
+
+    m_orphans.erase(it);
+    return 1;
+}
+
+void TxOrphanage::EraseForPeer(NodeId peer)
+{
+    AssertLockHeld(g_cs_orphans);
+
+    int nErased = 0;
+    std::map<uint256, OrphanTx>::iterator iter = m_orphans.begin();
+    while (iter != m_orphans.end())
+    {
+        std::map<uint256, OrphanTx>::iterator maybeErase = iter++; // increment to avoid iterator becoming invalid
+        if (maybeErase->second.fromPeer == peer)
+        {
+            nErased += EraseTx(maybeErase->second.tx->GetHash());
+        }
+    }
+    if (nErased > 0) LogPrint(BCLog::MEMPOOL, "Erased %d orphan tx from peer=%d\n", nErased, peer);
+}
+
+unsigned int TxOrphanage::LimitOrphans(unsigned int max_orphans)
+{
+    AssertLockHeld(g_cs_orphans);
+
+    unsigned int nEvicted = 0;
+    static int64_t nNextSweep;
+    int64_t nNow = GetTime();
+    if (nNextSweep <= nNow) {
+        // Sweep out expired orphan pool entries:
+        int nErased = 0;
+        int64_t nMinExpTime = nNow + ORPHAN_TX_EXPIRE_TIME - ORPHAN_TX_EXPIRE_INTERVAL;
+        std::map<uint256, OrphanTx>::iterator iter = m_orphans.begin();
+        while (iter != m_orphans.end())
+        {
+            std::map<uint256, OrphanTx>::iterator maybeErase = iter++;
+            if (maybeErase->second.nTimeExpire <= nNow) {
+                nErased += EraseTx(maybeErase->second.tx->GetHash());
+            } else {
+                nMinExpTime = std::min(maybeErase->second.nTimeExpire, nMinExpTime);
+            }
+        }
+        // Sweep again 5 minutes after the next entry that expires in order to batch the linear scan.
+        nNextSweep = nMinExpTime + ORPHAN_TX_EXPIRE_INTERVAL;
+        if (nErased > 0) LogPrint(BCLog::MEMPOOL, "Erased %d orphan tx due to expiration\n", nErased);
+    }
+    FastRandomContext rng;
+    while (m_orphans.size() > max_orphans)
+    {
+        // Evict a random orphan:
+        size_t randompos = rng.randrange(m_orphan_list.size());
+        EraseTx(m_orphan_list[randompos]->first);
+        ++nEvicted;
+    }
+    return nEvicted;
+}
+
+void TxOrphanage::AddChildrenToWorkSet(const CTransaction& tx, std::set<uint256>& orphan_work_set) const
+{
+    AssertLockHeld(g_cs_orphans);
+    for (unsigned int i = 0; i < tx.vout.size(); i++) {
+        const auto it_by_prev = m_outpoint_to_orphan_it.find(COutPoint(tx.GetHash(), i));
+        if (it_by_prev != m_outpoint_to_orphan_it.end()) {
+            for (const auto& elem : it_by_prev->second) {
+                orphan_work_set.insert(elem->first);
+            }
+        }
+    }
+}
+
+bool TxOrphanage::HaveTx(const GenTxid& gtxid) const
+{
+    LOCK(g_cs_orphans);
+    if (gtxid.IsWtxid()) {
+        return m_wtxid_to_orphan_it.count(gtxid.GetHash());
+    } else {
+        return m_orphans.count(gtxid.GetHash());
+    }
+}
+
+std::pair<CTransactionRef, NodeId> TxOrphanage::GetTx(const uint256& txid) const
+{
+    AssertLockHeld(g_cs_orphans);
+
+    const auto it = m_orphans.find(txid);
+    if (it == m_orphans.end()) return {nullptr, -1};
+    return {it->second.tx, it->second.fromPeer};
+}
+
+void TxOrphanage::EraseForBlock(const CBlock& block)
+{
+    LOCK(g_cs_orphans);
+
+    std::vector<uint256> vOrphanErase;
+
+    for (const CTransactionRef& ptx : block.vtx) {
+        const CTransaction& tx = *ptx;
+
+        // Which orphan pool entries must we evict?
+        for (const auto& txin : tx.vin) {
+            auto itByPrev = m_outpoint_to_orphan_it.find(txin.prevout);
+            if (itByPrev == m_outpoint_to_orphan_it.end()) continue;
+            for (auto mi = itByPrev->second.begin(); mi != itByPrev->second.end(); ++mi) {
+                const CTransaction& orphanTx = *(*mi)->second.tx;
+                const uint256& orphanHash = orphanTx.GetHash();
+                vOrphanErase.push_back(orphanHash);
+            }
+        }
+    }
+
+    // Erase orphan transactions included or precluded by this block
+    if (vOrphanErase.size()) {
+        int nErased = 0;
+        for (const uint256& orphanHash : vOrphanErase) {
+            nErased += EraseTx(orphanHash);
+        }
+        LogPrint(BCLog::MEMPOOL, "Erased %d orphan tx included or conflicted by block\n", nErased);
+    }
+}