Connect to an extra outbound peer if our tip is stale

If our tip hasn't updated in a while, that may be because our peers are
not relaying blocks to us that we would consider valid. Allow connection
to an additional outbound peer in that circumstance.

Also, periodically check to see if we are exceeding our target number of
outbound peers, and disconnect the one which has least recently
announced a new block to us (choosing the newest such peer in the case
of tie).

1 files changed, 14 insertions, 2 deletions

diff --git a/src/net_processing.h b/src/net_processing.h
index 656324bba0..0a49972eed 100644
--- a/src/net_processing.h
+++ b/src/net_processing.h
@@ -8,6 +8,7 @@
 
 #include "net.h"
 #include "validationinterface.h"
+#include "consensus/params.h"
 
 /** Default for -maxorphantx, maximum number of orphan transactions kept in memory */
 static const unsigned int DEFAULT_MAX_ORPHAN_TRANSACTIONS = 100;
@@ -27,13 +28,19 @@ static constexpr int64_t HEADERS_DOWNLOAD_TIMEOUT_PER_HEADER = 1000; // 1ms/head
 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
+/** How frequently to check for stale tips, in seconds */
+static constexpr int64_t STALE_CHECK_INTERVAL = 10 * 60; // 10 minutes
+/** How frequently to check for extra outbound peers and disconnect, in seconds */
+static constexpr int64_t EXTRA_PEER_CHECK_INTERVAL = 45;
+/** Minimum time an outbound-peer-eviction candidate must be connected for, in order to evict, in seconds */
+static constexpr int64_t MINIMUM_CONNECT_TIME = 30;
 
 class PeerLogicValidation : public CValidationInterface, public NetEventsInterface {
 private:
-    CConnman* connman;
+    CConnman* const connman;
 
 public:
-    explicit PeerLogicValidation(CConnman* connman);
+    explicit PeerLogicValidation(CConnman* connman, CScheduler &scheduler);
 
     void BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindexConnected, const std::vector<CTransactionRef>& vtxConflicted) override;
     void UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload) override;
@@ -55,6 +62,11 @@ public:
     bool SendMessages(CNode* pto, std::atomic<bool>& interrupt) override;
 
     void ConsiderEviction(CNode *pto, int64_t time_in_seconds);
+    void CheckForStaleTipAndEvictPeers(const Consensus::Params &consensusParams);
+    void EvictExtraOutboundPeers(int64_t time_in_seconds);
+
+private:
+    int64_t m_stale_tip_check_time; //! Next time to check for stale tip
 };
 
 struct CNodeStateStats {