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Add recently accepted blocks and txn to AttemptToEvictConnection.

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This protects any not-already-protected peers who were the most
 recent four to relay transactions and most recent four to send
 blocks to us.
This commit is contained in:
Gregory Maxwell
2016-05-22 05:55:15 +00:00
parent 32b7294177
commit 5d0ca81f74
4 changed files with 61 additions and 10 deletions
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48
src/net.cpp
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@@ -838,6 +838,11 @@ struct NodeEvictionCandidate
NodeId id;
int64_t nTimeConnected;
int64_t nMinPingUsecTime;
int64_t nLastBlockTime;
int64_t nLastTXTime;
bool fNetworkNode;
bool fRelayTxes;
bool fBloomFilter;
CAddress addr;
uint64_t nKeyedNetGroup;
};
@@ -854,7 +859,24 @@ static bool ReverseCompareNodeTimeConnected(const NodeEvictionCandidate &a, cons
static bool CompareNetGroupKeyed(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b) {
return a.nKeyedNetGroup < b.nKeyedNetGroup;
};
}
static bool CompareNodeBlockTime(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b)
{
// There is a fall-through here because it is common for a node to have many peers which have not yet relayed a block.
if (a.nLastBlockTime != b.nLastBlockTime) return a.nLastBlockTime < b.nLastBlockTime;
if (a.fNetworkNode != b.fNetworkNode) return b.fNetworkNode;
return a.nTimeConnected > b.nTimeConnected;
}
static bool CompareNodeTXTime(const NodeEvictionCandidate &a, const NodeEvictionCandidate &b)
{
// There is a fall-through here because it is common for a node to have more than a few peers that have not yet relayed txn.
if (a.nLastTXTime != b.nLastTXTime) return a.nLastTXTime < b.nLastTXTime;
if (a.fRelayTxes != b.fRelayTxes) return b.fRelayTxes;
if (a.fBloomFilter != b.fBloomFilter) return a.fBloomFilter;
return a.nTimeConnected > b.nTimeConnected;
}
/** Try to find a connection to evict when the node is full.
* Extreme care must be taken to avoid opening the node to attacker
@@ -864,7 +886,7 @@ static bool CompareNetGroupKeyed(const NodeEvictionCandidate &a, const NodeEvict
* to forge. In order to partition a node the attacker must be
* simultaneously better at all of them than honest peers.
*/
static bool AttemptToEvictConnection(bool fPreferNewConnection) {
static bool AttemptToEvictConnection() {
std::vector<NodeEvictionCandidate> vEvictionCandidates;
{
LOCK(cs_vNodes);
@@ -876,7 +898,9 @@ static bool AttemptToEvictConnection(bool fPreferNewConnection) {
continue;
if (node->fDisconnect)
continue;
NodeEvictionCandidate candidate = {node->id, node->nTimeConnected, node->nMinPingUsecTime, node->addr, node->nKeyedNetGroup};
NodeEvictionCandidate candidate = {node->id, node->nTimeConnected, node->nMinPingUsecTime,
node->nLastBlockTime, node->nLastTXTime, node->fNetworkNode,
node->fRelayTxes, node->pfilter != NULL, node->addr, node->nKeyedNetGroup};
vEvictionCandidates.push_back(candidate);
}
}
@@ -899,6 +923,20 @@ static bool AttemptToEvictConnection(bool fPreferNewConnection) {
if (vEvictionCandidates.empty()) return false;
// Protect 4 nodes that most recently sent us transactions.
// An attacker cannot manipulate this metric without performing useful work.
std::sort(vEvictionCandidates.begin(), vEvictionCandidates.end(), CompareNodeTXTime);
vEvictionCandidates.erase(vEvictionCandidates.end() - std::min(4, static_cast<int>(vEvictionCandidates.size())), vEvictionCandidates.end());
if (vEvictionCandidates.empty()) return false;
// Protect 4 nodes that most recently sent us blocks.
// An attacker cannot manipulate this metric without performing useful work.
std::sort(vEvictionCandidates.begin(), vEvictionCandidates.end(), CompareNodeBlockTime);
vEvictionCandidates.erase(vEvictionCandidates.end() - std::min(4, static_cast<int>(vEvictionCandidates.size())), vEvictionCandidates.end());
if (vEvictionCandidates.empty()) return false;
// 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.
std::sort(vEvictionCandidates.begin(), vEvictionCandidates.end(), ReverseCompareNodeTimeConnected);
@@ -999,7 +1037,7 @@ static void AcceptConnection(const ListenSocket& hListenSocket) {
if (nInbound >= nMaxInbound)
{
if (!AttemptToEvictConnection(whitelisted)) {
if (!AttemptToEvictConnection()) {
// No connection to evict, disconnect the new connection
LogPrint("net", "failed to find an eviction candidate - connection dropped (full)\n");
CloseSocket(hSocket);
@@ -2358,6 +2396,8 @@ CNode::CNode(SOCKET hSocketIn, const CAddress& addrIn, const std::string& addrNa
fSentAddr = false;
pfilter = new CBloomFilter();
timeLastMempoolReq = 0;
nLastBlockTime = 0;
nLastTXTime = 0;
nPingNonceSent = 0;
nPingUsecStart = 0;
nPingUsecTime = 0;