move-only: Add txorphanage module

This module captures orphan tracking code for tx relay.

Can be reviewed with --color-moved=dimmed-zebra

1 files changed, 107 insertions, 0 deletions

diff --git a/src/txorphanage.cpp b/src/txorphanage.cpp
new file mode 100644
index 0000000000..fb03914681
--- /dev/null
+++ b/src/txorphanage.cpp
@@ -0,0 +1,107 @@
+// 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>
+
+/** Minimum time between orphan transactions expire time checks in seconds */
+static constexpr int64_t ORPHAN_TX_EXPIRE_INTERVAL = 5 * 60;
+
+RecursiveMutex g_cs_orphans;
+
+std::map<uint256, COrphanTx> mapOrphanTransactions GUARDED_BY(g_cs_orphans);
+std::map<uint256, std::map<uint256, COrphanTx>::iterator> g_orphans_by_wtxid GUARDED_BY(g_cs_orphans);
+
+    std::map<COutPoint, std::set<std::map<uint256, COrphanTx>::iterator, IteratorComparator>> mapOrphanTransactionsByPrev GUARDED_BY(g_cs_orphans);
+
+    std::vector<std::map<uint256, COrphanTx>::iterator> g_orphan_list GUARDED_BY(g_cs_orphans);
+
+int EraseOrphanTx(uint256 hash)
+{
+    std::map<uint256, COrphanTx>::iterator it = mapOrphanTransactions.find(hash);
+    if (it == mapOrphanTransactions.end())
+        return 0;
+    for (const CTxIn& txin : it->second.tx->vin)
+    {
+        auto itPrev = mapOrphanTransactionsByPrev.find(txin.prevout);
+        if (itPrev == mapOrphanTransactionsByPrev.end())
+            continue;
+        itPrev->second.erase(it);
+        if (itPrev->second.empty())
+            mapOrphanTransactionsByPrev.erase(itPrev);
+    }
+
+    size_t old_pos = it->second.list_pos;
+    assert(g_orphan_list[old_pos] == it);
+    if (old_pos + 1 != g_orphan_list.size()) {
+        // Unless we're deleting the last entry in g_orphan_list, move the last
+        // entry to the position we're deleting.
+        auto it_last = g_orphan_list.back();
+        g_orphan_list[old_pos] = it_last;
+        it_last->second.list_pos = old_pos;
+    }
+    g_orphan_list.pop_back();
+    g_orphans_by_wtxid.erase(it->second.tx->GetWitnessHash());
+
+    mapOrphanTransactions.erase(it);
+    return 1;
+}
+
+void EraseOrphansFor(NodeId peer)
+{
+    LOCK(g_cs_orphans);
+    int nErased = 0;
+    std::map<uint256, COrphanTx>::iterator iter = mapOrphanTransactions.begin();
+    while (iter != mapOrphanTransactions.end())
+    {
+        std::map<uint256, COrphanTx>::iterator maybeErase = iter++; // increment to avoid iterator becoming invalid
+        if (maybeErase->second.fromPeer == peer)
+        {
+            nErased += EraseOrphanTx(maybeErase->second.tx->GetHash());
+        }
+    }
+    if (nErased > 0) LogPrint(BCLog::MEMPOOL, "Erased %d orphan tx from peer=%d\n", nErased, peer);
+}
+
+unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
+{
+    LOCK(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, COrphanTx>::iterator iter = mapOrphanTransactions.begin();
+        while (iter != mapOrphanTransactions.end())
+        {
+            std::map<uint256, COrphanTx>::iterator maybeErase = iter++;
+            if (maybeErase->second.nTimeExpire <= nNow) {
+                nErased += EraseOrphanTx(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 (mapOrphanTransactions.size() > nMaxOrphans)
+    {
+        // Evict a random orphan:
+        size_t randompos = rng.randrange(g_orphan_list.size());
+        EraseOrphanTx(g_orphan_list[randompos]->first);
+        ++nEvicted;
+    }
+    return nEvicted;
+}
+