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-rw-r--r--src/net_processing.cpp113
-rw-r--r--src/net_processing.h8
2 files changed, 120 insertions, 1 deletions
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 8551e84558..f83a20102e 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -124,6 +124,9 @@ namespace {
/** Number of peers from which we're downloading blocks. */
int nPeersWithValidatedDownloads = 0;
+ /** Number of outbound peers with m_chain_sync.m_protect. */
+ int g_outbound_peers_with_protect_from_disconnect = 0;
+
/** Relay map, protected by cs_main. */
typedef std::map<uint256, CTransactionRef> MapRelay;
MapRelay mapRelay;
@@ -201,6 +204,33 @@ struct CNodeState {
*/
bool fSupportsDesiredCmpctVersion;
+ /** State used to enforce CHAIN_SYNC_TIMEOUT
+ * Only in effect for outbound, non-manual connections, with
+ * m_protect == false
+ * Algorithm: if a peer's best known block has less work than our tip,
+ * set a timeout CHAIN_SYNC_TIMEOUT seconds in the future:
+ * - If at timeout their best known block now has more work than our tip
+ * when the timeout was set, then either reset the timeout or clear it
+ * (after comparing against our current tip's work)
+ * - If at timeout their best known block still has less work than our
+ * tip did when the timeout was set, then send a getheaders message,
+ * and set a shorter timeout, HEADERS_RESPONSE_TIME seconds in future.
+ * If their best known block is still behind when that new timeout is
+ * reached, disconnect.
+ */
+ struct ChainSyncTimeoutState {
+ //! A timeout used for checking whether our peer has sufficiently synced
+ int64_t m_timeout;
+ //! A header with the work we require on our peer's chain
+ const CBlockIndex * m_work_header;
+ //! After timeout is reached, set to true after sending getheaders
+ bool m_sent_getheaders;
+ //! Whether this peer is protected from disconnection due to a bad/slow chain
+ bool m_protect;
+ };
+
+ ChainSyncTimeoutState m_chain_sync;
+
CNodeState(CAddress addrIn, std::string addrNameIn) : address(addrIn), name(addrNameIn) {
fCurrentlyConnected = false;
nMisbehavior = 0;
@@ -223,6 +253,7 @@ struct CNodeState {
fHaveWitness = false;
fWantsCmpctWitness = false;
fSupportsDesiredCmpctVersion = false;
+ m_chain_sync = { 0, nullptr, false, false };
}
};
@@ -502,6 +533,13 @@ void FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vector<con
} // namespace
+// Returns true for outbound peers, excluding manual connections, feelers, and
+// one-shots
+bool IsOutboundDisconnectionCandidate(const CNode *node)
+{
+ return !(node->fInbound || node->m_manual_connection || node->fFeeler || node->fOneShot);
+}
+
void PeerLogicValidation::InitializeNode(CNode *pnode) {
CAddress addr = pnode->addr;
std::string addrName = pnode->GetAddrName();
@@ -534,6 +572,8 @@ void PeerLogicValidation::FinalizeNode(NodeId nodeid, bool& fUpdateConnectionTim
nPreferredDownload -= state->fPreferredDownload;
nPeersWithValidatedDownloads -= (state->nBlocksInFlightValidHeaders != 0);
assert(nPeersWithValidatedDownloads >= 0);
+ g_outbound_peers_with_protect_from_disconnect -= state->m_chain_sync.m_protect;
+ assert(g_outbound_peers_with_protect_from_disconnect >= 0);
mapNodeState.erase(nodeid);
@@ -542,6 +582,7 @@ void PeerLogicValidation::FinalizeNode(NodeId nodeid, bool& fUpdateConnectionTim
assert(mapBlocksInFlight.empty());
assert(nPreferredDownload == 0);
assert(nPeersWithValidatedDownloads == 0);
+ assert(g_outbound_peers_with_protect_from_disconnect == 0);
}
LogPrint(BCLog::NET, "Cleared nodestate for peer=%d\n", nodeid);
}
@@ -2324,6 +2365,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
assert(pindexLast);
UpdateBlockAvailability(pfrom->GetId(), pindexLast->GetBlockHash());
+ // From here, pindexBestKnownBlock should be guaranteed to be non-null,
+ // because it is set in UpdateBlockAvailability. Some nullptr checks
+ // are still present, however, as belt-and-suspenders.
+
if (nCount == MAX_HEADERS_RESULTS) {
// Headers message had its maximum size; the peer may have more headers.
// TODO: optimize: if pindexLast is an ancestor of chainActive.Tip or pindexBestHeader, continue
@@ -2396,11 +2441,22 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
// chainActive.Tip()) because we won't start block download
// until we have a headers chain that has at least
// nMinimumChainWork, even if a peer has a chain past our tip,
- if (!(pfrom->fInbound || pfrom->fWhitelisted || pfrom->m_manual_connection)) {
+ // as an anti-DoS measure.
+ if (IsOutboundDisconnectionCandidate(pfrom)) {
+ LogPrintf("Disconnecting outbound peer %d -- headers chain has insufficient work\n", pfrom->GetId());
pfrom->fDisconnect = true;
}
}
}
+
+ if (!pfrom->fDisconnect && IsOutboundDisconnectionCandidate(pfrom) && nodestate->pindexBestKnownBlock != nullptr) {
+ // If this is an outbound peer, check to see if we should protect
+ // it from the bad/lagging chain logic.
+ if (g_outbound_peers_with_protect_from_disconnect < MAX_OUTBOUND_PEERS_TO_PROTECT_FROM_DISCONNECT && nodestate->pindexBestKnownBlock->nChainWork >= chainActive.Tip()->nChainWork && !nodestate->m_chain_sync.m_protect) {
+ nodestate->m_chain_sync.m_protect = true;
+ ++g_outbound_peers_with_protect_from_disconnect;
+ }
+ }
}
}
@@ -2799,6 +2855,58 @@ bool PeerLogicValidation::ProcessMessages(CNode* pfrom, std::atomic<bool>& inter
return fMoreWork;
}
+void PeerLogicValidation::ConsiderEviction(CNode *pto, int64_t time_in_seconds)
+{
+ AssertLockHeld(cs_main);
+
+ CNodeState &state = *State(pto->GetId());
+ const CNetMsgMaker msgMaker(pto->GetSendVersion());
+
+ if (!state.m_chain_sync.m_protect && IsOutboundDisconnectionCandidate(pto) && state.fSyncStarted) {
+ // This is an outbound peer subject to disconnection if they don't
+ // announce a block with as much work as the current tip within
+ // CHAIN_SYNC_TIMEOUT + HEADERS_RESPONSE_TIME seconds (note: if
+ // their chain has more work than ours, we should sync to it,
+ // unless it's invalid, in which case we should find that out and
+ // disconnect from them elsewhere).
+ if (state.pindexBestKnownBlock != nullptr && state.pindexBestKnownBlock->nChainWork >= chainActive.Tip()->nChainWork) {
+ if (state.m_chain_sync.m_timeout != 0) {
+ state.m_chain_sync.m_timeout = 0;
+ state.m_chain_sync.m_work_header = nullptr;
+ state.m_chain_sync.m_sent_getheaders = false;
+ }
+ } else if (state.m_chain_sync.m_timeout == 0 || (state.m_chain_sync.m_work_header != nullptr && state.pindexBestKnownBlock != nullptr && state.pindexBestKnownBlock->nChainWork >= state.m_chain_sync.m_work_header->nChainWork)) {
+ // Our best block known by this peer is behind our tip, and we're either noticing
+ // that for the first time, OR this peer was able to catch up to some earlier point
+ // where we checked against our tip.
+ // Either way, set a new timeout based on current tip.
+ state.m_chain_sync.m_timeout = time_in_seconds + CHAIN_SYNC_TIMEOUT;
+ state.m_chain_sync.m_work_header = chainActive.Tip();
+ state.m_chain_sync.m_sent_getheaders = false;
+ } else if (state.m_chain_sync.m_timeout > 0 && time_in_seconds > state.m_chain_sync.m_timeout) {
+ // No evidence yet that our peer has synced to a chain with work equal to that
+ // of our tip, when we first detected it was behind. Send a single getheaders
+ // message to give the peer a chance to update us.
+ if (state.m_chain_sync.m_sent_getheaders) {
+ // They've run out of time to catch up!
+ LogPrintf("Disconnecting outbound peer %d for old chain, best known block = %s\n", pto->GetId(), state.pindexBestKnownBlock != nullptr ? state.pindexBestKnownBlock->GetBlockHash().ToString() : "<none>");
+ pto->fDisconnect = true;
+ } else {
+ LogPrint(BCLog::NET, "sending getheaders to outbound peer=%d to verify chain work (current best known block:%s, benchmark blockhash: %s)\n", pto->GetId(), state.pindexBestKnownBlock != nullptr ? state.pindexBestKnownBlock->GetBlockHash().ToString() : "<none>", state.m_chain_sync.m_work_header->GetBlockHash().ToString());
+ connman->PushMessage(pto, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(state.m_chain_sync.m_work_header->pprev), uint256()));
+ state.m_chain_sync.m_sent_getheaders = true;
+ constexpr int64_t HEADERS_RESPONSE_TIME = 120; // 2 minutes
+ // Bump the timeout to allow a response, which could clear the timeout
+ // (if the response shows the peer has synced), reset the timeout (if
+ // the peer syncs to the required work but not to our tip), or result
+ // in disconnect (if we advance to the timeout and pindexBestKnownBlock
+ // has not sufficiently progressed)
+ state.m_chain_sync.m_timeout = time_in_seconds + HEADERS_RESPONSE_TIME;
+ }
+ }
+ }
+}
+
class CompareInvMempoolOrder
{
CTxMemPool *mp;
@@ -3265,6 +3373,9 @@ bool PeerLogicValidation::SendMessages(CNode* pto, std::atomic<bool>& interruptM
}
}
+ // Check that outbound peers have reasonable chains
+ // GetTime() is used by this anti-DoS logic so we can test this using mocktime
+ ConsiderEviction(pto, GetTime());
//
// Message: getdata (blocks)
diff --git a/src/net_processing.h b/src/net_processing.h
index 79745cdd42..656324bba0 100644
--- a/src/net_processing.h
+++ b/src/net_processing.h
@@ -21,6 +21,12 @@ static const unsigned int DEFAULT_BLOCK_RECONSTRUCTION_EXTRA_TXN = 100;
* Timeout = base + per_header * (expected number of headers) */
static constexpr int64_t HEADERS_DOWNLOAD_TIMEOUT_BASE = 15 * 60 * 1000000; // 15 minutes
static constexpr int64_t HEADERS_DOWNLOAD_TIMEOUT_PER_HEADER = 1000; // 1ms/header
+/** Protect at least this many outbound peers from disconnection due to slow/
+ * behind headers chain.
+ */
+static constexpr int32_t MAX_OUTBOUND_PEERS_TO_PROTECT_FROM_DISCONNECT = 4;
+/** Timeout for (unprotected) outbound peers to sync to our chainwork, in seconds */
+static constexpr int64_t CHAIN_SYNC_TIMEOUT = 20 * 60; // 20 minutes
class PeerLogicValidation : public CValidationInterface, public NetEventsInterface {
private:
@@ -47,6 +53,8 @@ public:
* @return True if there is more work to be done
*/
bool SendMessages(CNode* pto, std::atomic<bool>& interrupt) override;
+
+ void ConsiderEviction(CNode *pto, int64_t time_in_seconds);
};
struct CNodeStateStats {