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diff --git a/src/net.cpp b/src/net.cpp
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -848,6 +848,7 @@
CAddress addr;
uint64_t nKeyedNetGroup;
bool prefer_evict;
+ bool m_is_local;
};
static bool ReverseCompareNodeMinPingTime(const NodeEvictionCandidate &a,
@@ -860,6 +861,15 @@
return a.nTimeConnected > b.nTimeConnected;
}
+static bool CompareLocalHostTimeConnected(const NodeEvictionCandidate &a,
+ const NodeEvictionCandidate &b) {
+ if (a.m_is_local != b.m_is_local) {
+ return b.m_is_local;
+ }
+
+ return a.nTimeConnected > b.nTimeConnected;
+}
+
static bool CompareNetGroupKeyed(const NodeEvictionCandidate &a,
const NodeEvictionCandidate &b) {
return a.nKeyedNetGroup < b.nKeyedNetGroup;
@@ -899,6 +909,25 @@
return a.nTimeConnected > b.nTimeConnected;
}
+// Pick out the potential block-relay only peers, and sort them by last block
+// time.
+static bool CompareNodeBlockRelayOnlyTime(const NodeEvictionCandidate &a,
+ const NodeEvictionCandidate &b) {
+ if (a.fRelayTxes != b.fRelayTxes) {
+ return a.fRelayTxes;
+ }
+
+ if (a.nLastBlockTime != b.nLastBlockTime) {
+ return a.nLastBlockTime < b.nLastBlockTime;
+ }
+
+ if (a.fRelevantServices != b.fRelevantServices) {
+ return b.fRelevantServices;
+ }
+
+ return a.nTimeConnected > b.nTimeConnected;
+}
+
//! Sort an array by the specified comparator, then erase the last K elements.
template <typename T, typename Comparator>
static void EraseLastKElements(std::vector<T> &elements, Comparator comparator,
@@ -950,7 +979,8 @@
peer_filter_not_null,
node->addr,
node->nKeyedNetGroup,
- node->m_prefer_evict};
+ node->m_prefer_evict,
+ node->addr.IsLocal()};
vEvictionCandidates.push_back(candidate);
}
}
@@ -968,14 +998,46 @@
// into our mempool. An attacker cannot manipulate this metric without
// performing useful work.
EraseLastKElements(vEvictionCandidates, CompareNodeTXTime, 4);
+ // Protect up to 8 non-tx-relay peers that have sent us novel blocks.
+ std::sort(vEvictionCandidates.begin(), vEvictionCandidates.end(),
+ CompareNodeBlockRelayOnlyTime);
+ size_t erase_size = std::min(size_t(8), vEvictionCandidates.size());
+ vEvictionCandidates.erase(
+ std::remove_if(vEvictionCandidates.end() - erase_size,
+ vEvictionCandidates.end(),
+ [](NodeEvictionCandidate const &n) {
+ return !n.fRelayTxes && n.fRelevantServices;
+ }),
+ vEvictionCandidates.end());
+
// Protect 4 nodes that most recently sent us novel blocks.
// An attacker cannot manipulate this metric without performing useful work.
EraseLastKElements(vEvictionCandidates, CompareNodeBlockTime, 4);
+
// Protect the half of the remaining nodes which have been connected the
// longest. This replicates the non-eviction implicit behavior, and
// precludes attacks that start later.
+ // Reserve half of these protected spots for localhost peers, even if
+ // they're not longest-uptime overall. This helps protect tor peers, which
+ // tend to be otherwise disadvantaged under our eviction criteria.
+ size_t initial_size = vEvictionCandidates.size();
+ size_t total_protect_size = initial_size / 2;
+
+ // Pick out up to 1/4 peers that are localhost, sorted by longest uptime.
+ std::sort(vEvictionCandidates.begin(), vEvictionCandidates.end(),
+ CompareLocalHostTimeConnected);
+ size_t local_erase_size = total_protect_size / 2;
+ vEvictionCandidates.erase(
+ std::remove_if(
+ vEvictionCandidates.end() - local_erase_size,
+ vEvictionCandidates.end(),
+ [](NodeEvictionCandidate const &n) { return n.m_is_local; }),
+ vEvictionCandidates.end());
+ // Calculate how many we removed, and update our total number of peers that
+ // we want to protect based on uptime accordingly.
+ total_protect_size -= initial_size - vEvictionCandidates.size();
EraseLastKElements(vEvictionCandidates, ReverseCompareNodeTimeConnected,
- vEvictionCandidates.size() / 2);
+ total_protect_size);
if (vEvictionCandidates.empty()) {
return false;

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