Merge #11592: 0.15: Backportsv0.15.1rc1

8195cb0d7 rpc: further constrain the libevent workaround (Cory Fields)
34153a7e4 rpc: work-around an upstream libevent bug (Cory Fields)
fc308a6cd Add unit test for stale tip checking (Suhas Daftuar)
2ed0647ac Add CConnmanTest to mutate g_connman in tests (João Barbosa)
a607a95d8 Connect to an extra outbound peer if our tip is stale (Suhas Daftuar)
459f2db42 Track tip update time and last new block announcement from each peer (Suhas Daftuar)
49bf09018 net: Allow connecting to extra outbound peers (Suhas Daftuar)
bb83fe190 Add release notes describing blockmaxweight deprecation (Matt Corallo)
4c82cea99 Use a sensible default for blockmaxweight (Matt Corallo)
7871a7d3b Deprecate confusing blockmaxsize, fix getmininginfo output (Matt Corallo)
6baa317b5 Fix minchainwork test for 0.15 backport (Suhas Daftuar)
55b7abfa8 Make p2p-acceptablock not an extended test (Matt Corallo)
5bec7744d [qa] test that invalid blocks on an invalid chain get a disconnect (Matt Corallo)
92d6105c4 Reject headers building on invalid chains by tracking invalidity (Matt Corallo)
51001d684 Accept unrequested blocks with work equal to our tip (Matt Corallo)
c6e4d0ce8 Stop always storing blocks from whitelisted peers (Matt Corallo)
e976c36dd Rewrite p2p-acceptblock in preparation for slight behavior changes (Matt Corallo)
ec8dedff4 net: Add missing lock in ProcessHeadersMessage(...) (practicalswift)
59b210d9a Disconnect outbound peers relaying invalid headers (Suhas Daftuar)
fc966bbd2 moveonly: factor out headers processing into separate function (Suhas Daftuar)
e3272242e Add unit test for outbound peer eviction (Suhas Daftuar)
9961abf9e Permit disconnection of outbound peers on bad/slow chains (Suhas Daftuar)
bf191a718 Disconnecting from bad outbound peers in IBD (Suhas Daftuar)
d570aa429 Fix uninitialized g_connman crash in Shutdown() (MeshCollider)
0a5477c7e net: stop both net/net_processing before destroying them (Cory Fields)
b4136f21c net: drop unused connman param (Cory Fields)
dc897e53d net: use an interface class rather than signals for message processing (Cory Fields)
8aee55af3 net: pass CConnman via pointer rather than reference (Cory Fields)
6f279652b Rename fAddnode to a more-descriptive "manual_connection" (Matt Corallo)
ffb6ea4e5 Add comment explaining forced processing of compact blocks (Suhas Daftuar)
2df65eeb9 qa: add test for minchainwork use in acceptblock (Suhas Daftuar)
3acec3878 Don't process unrequested, low-work blocks (Suhas Daftuar)
0e9d04bf0 [qa] Test nMinimumChainWork (Suhas Daftuar)
da4908c3a Allow setting nMinimumChainWork on command line (Suhas Daftuar)
41088795d qa: Remove never used return value of sync_with_ping (MarcoFalke)
f3457d0e8 qa: Make tmpdir option an absolute path (MarcoFalke)
9c8006dc3 Avoid opening copied wallet databases simultaneously (Russell Yanofsky)
de7053f11 [wallet] Fix leak in CDB constructor (João Barbosa)
fd79ed6b2 Ensure backupwallet fails when attempting to backup to source file (Tomas van der Wansem)
d94fc336c scripted-diff: rename assert_raises_jsonrpc to assert_raises_rpc error (John Newbery)
623de0acb [tests] do not allow assert_raises_message to be called with JSONRPCException (John Newbery)
5b728c8e9 [tests] remove direct testing on JSONRPCException from individual test cases (John Newbery)

Pull request description:

Tree-SHA512: 9fdb5c47844a899271023d8d445f7fc728e3ad71916490cd9783464684967594b07cda05dd644b722bfcea9fade74d06cfc501e1a68abf118d6d03fbbf7d7707

1 files changed, 599 insertions, 293 deletions

diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index e09b56a631..dea4b042e6 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -23,6 +23,7 @@
 #include "primitives/transaction.h"
 #include "random.h"
 #include "reverse_iterator.h"
+#include "scheduler.h"
 #include "tinyformat.h"
 #include "txmempool.h"
 #include "ui_interface.h"
@@ -116,6 +117,12 @@ 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;
+
+    /** When our tip was last updated. */
+    int64_t g_last_tip_update = 0;
+
     /** Relay map, protected by cs_main. */
     typedef std::map<uint256, CTransactionRef> MapRelay;
     MapRelay mapRelay;
@@ -123,11 +130,6 @@ namespace {
     std::deque<std::pair<int64_t, MapRelay::iterator>> vRelayExpiration;
 } // namespace
 
-//////////////////////////////////////////////////////////////////////////////
-//
-// Registration of network node signals.
-//
-
 namespace {
 
 struct CBlockReject {
@@ -198,6 +200,36 @@ 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;
+
+    //! Time of last new block announcement
+    int64_t m_last_block_announcement;
+
     CNodeState(CAddress addrIn, std::string addrNameIn) : address(addrIn), name(addrNameIn) {
         fCurrentlyConnected = false;
         nMisbehavior = 0;
@@ -220,6 +252,8 @@ struct CNodeState {
         fHaveWitness = false;
         fWantsCmpctWitness = false;
         fSupportsDesiredCmpctVersion = false;
+        m_chain_sync = { 0, nullptr, false, false };
+        m_last_block_announcement = 0;
     }
 };
 
@@ -244,7 +278,7 @@ void UpdatePreferredDownload(CNode* node, CNodeState* state)
     nPreferredDownload += state->fPreferredDownload;
 }
 
-void PushNodeVersion(CNode *pnode, CConnman& connman, int64_t nTime)
+void PushNodeVersion(CNode *pnode, CConnman* connman, int64_t nTime)
 {
     ServiceFlags nLocalNodeServices = pnode->GetLocalServices();
     uint64_t nonce = pnode->GetLocalNonce();
@@ -255,7 +289,7 @@ void PushNodeVersion(CNode *pnode, CConnman& connman, int64_t nTime)
     CAddress addrYou = (addr.IsRoutable() && !IsProxy(addr) ? addr : CAddress(CService(), addr.nServices));
     CAddress addrMe = CAddress(CService(), nLocalNodeServices);
 
-    connman.PushMessage(pnode, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::VERSION, PROTOCOL_VERSION, (uint64_t)nLocalNodeServices, nTime, addrYou, addrMe,
+    connman->PushMessage(pnode, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::VERSION, PROTOCOL_VERSION, (uint64_t)nLocalNodeServices, nTime, addrYou, addrMe,
             nonce, strSubVersion, nNodeStartingHeight, ::fRelayTxes));
 
     if (fLogIPs) {
@@ -265,49 +299,6 @@ void PushNodeVersion(CNode *pnode, CConnman& connman, int64_t nTime)
     }
 }
 
-void InitializeNode(CNode *pnode, CConnman& connman) {
-    CAddress addr = pnode->addr;
-    std::string addrName = pnode->GetAddrName();
-    NodeId nodeid = pnode->GetId();
-    {
-        LOCK(cs_main);
-        mapNodeState.emplace_hint(mapNodeState.end(), std::piecewise_construct, std::forward_as_tuple(nodeid), std::forward_as_tuple(addr, std::move(addrName)));
-    }
-    if(!pnode->fInbound)
-        PushNodeVersion(pnode, connman, GetTime());
-}
-
-void FinalizeNode(NodeId nodeid, bool& fUpdateConnectionTime) {
-    fUpdateConnectionTime = false;
-    LOCK(cs_main);
-    CNodeState *state = State(nodeid);
-
-    if (state->fSyncStarted)
-        nSyncStarted--;
-
-    if (state->nMisbehavior == 0 && state->fCurrentlyConnected) {
-        fUpdateConnectionTime = true;
-    }
-
-    for (const QueuedBlock& entry : state->vBlocksInFlight) {
-        mapBlocksInFlight.erase(entry.hash);
-    }
-    EraseOrphansFor(nodeid);
-    nPreferredDownload -= state->fPreferredDownload;
-    nPeersWithValidatedDownloads -= (state->nBlocksInFlightValidHeaders != 0);
-    assert(nPeersWithValidatedDownloads >= 0);
-
-    mapNodeState.erase(nodeid);
-
-    if (mapNodeState.empty()) {
-        // Do a consistency check after the last peer is removed.
-        assert(mapBlocksInFlight.empty());
-        assert(nPreferredDownload == 0);
-        assert(nPeersWithValidatedDownloads == 0);
-    }
-    LogPrint(BCLog::NET, "Cleared nodestate for peer=%d\n", nodeid);
-}
-
 // Requires cs_main.
 // Returns a bool indicating whether we requested this block.
 // Also used if a block was /not/ received and timed out or started with another peer
@@ -402,7 +393,7 @@ void UpdateBlockAvailability(NodeId nodeid, const uint256 &hash) {
     }
 }
 
-void MaybeSetPeerAsAnnouncingHeaderAndIDs(NodeId nodeid, CConnman& connman) {
+void MaybeSetPeerAsAnnouncingHeaderAndIDs(NodeId nodeid, CConnman* connman) {
     AssertLockHeld(cs_main);
     CNodeState* nodestate = State(nodeid);
     if (!nodestate || !nodestate->fSupportsDesiredCmpctVersion) {
@@ -417,26 +408,35 @@ void MaybeSetPeerAsAnnouncingHeaderAndIDs(NodeId nodeid, CConnman& connman) {
                 return;
             }
         }
-        connman.ForNode(nodeid, [&connman](CNode* pfrom){
+        connman->ForNode(nodeid, [connman](CNode* pfrom){
             bool fAnnounceUsingCMPCTBLOCK = false;
             uint64_t nCMPCTBLOCKVersion = (pfrom->GetLocalServices() & NODE_WITNESS) ? 2 : 1;
             if (lNodesAnnouncingHeaderAndIDs.size() >= 3) {
                 // As per BIP152, we only get 3 of our peers to announce
                 // blocks using compact encodings.
-                connman.ForNode(lNodesAnnouncingHeaderAndIDs.front(), [&connman, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion](CNode* pnodeStop){
-                    connman.PushMessage(pnodeStop, CNetMsgMaker(pnodeStop->GetSendVersion()).Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
+                connman->ForNode(lNodesAnnouncingHeaderAndIDs.front(), [connman, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion](CNode* pnodeStop){
+                    connman->PushMessage(pnodeStop, CNetMsgMaker(pnodeStop->GetSendVersion()).Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
                     return true;
                 });
                 lNodesAnnouncingHeaderAndIDs.pop_front();
             }
             fAnnounceUsingCMPCTBLOCK = true;
-            connman.PushMessage(pfrom, CNetMsgMaker(pfrom->GetSendVersion()).Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
+            connman->PushMessage(pfrom, CNetMsgMaker(pfrom->GetSendVersion()).Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
             lNodesAnnouncingHeaderAndIDs.push_back(pfrom->GetId());
             return true;
         });
     }
 }
 
+bool TipMayBeStale(const Consensus::Params &consensusParams)
+{
+    AssertLockHeld(cs_main);
+    if (g_last_tip_update == 0) {
+        g_last_tip_update = GetTime();
+    }
+    return g_last_tip_update < GetTime() - consensusParams.nPowTargetSpacing * 3 && mapBlocksInFlight.empty();
+}
+
 // Requires cs_main
 bool CanDirectFetch(const Consensus::Params &consensusParams)
 {
@@ -466,7 +466,7 @@ void FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vector<con
     // Make sure pindexBestKnownBlock is up to date, we'll need it.
     ProcessBlockAvailability(nodeid);
 
-    if (state->pindexBestKnownBlock == nullptr || state->pindexBestKnownBlock->nChainWork < chainActive.Tip()->nChainWork || state->pindexBestKnownBlock->nChainWork < UintToArith256(consensusParams.nMinimumChainWork)) {
+    if (state->pindexBestKnownBlock == nullptr || state->pindexBestKnownBlock->nChainWork < chainActive.Tip()->nChainWork || state->pindexBestKnownBlock->nChainWork < nMinimumChainWork) {
         // This peer has nothing interesting.
         return;
     }
@@ -543,6 +543,69 @@ void FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vector<con
 
 } // namespace
 
+// This function is used for testing the stale tip eviction logic, see
+// DoS_tests.cpp
+void UpdateLastBlockAnnounceTime(NodeId node, int64_t time_in_seconds)
+{
+    LOCK(cs_main);
+    CNodeState *state = State(node);
+    if (state) state->m_last_block_announcement = time_in_seconds;
+}
+
+// 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();
+    NodeId nodeid = pnode->GetId();
+    {
+        LOCK(cs_main);
+        mapNodeState.emplace_hint(mapNodeState.end(), std::piecewise_construct, std::forward_as_tuple(nodeid), std::forward_as_tuple(addr, std::move(addrName)));
+    }
+    if(!pnode->fInbound)
+        PushNodeVersion(pnode, connman, GetTime());
+}
+
+void PeerLogicValidation::FinalizeNode(NodeId nodeid, bool& fUpdateConnectionTime) {
+    fUpdateConnectionTime = false;
+    LOCK(cs_main);
+    CNodeState *state = State(nodeid);
+    assert(state != nullptr);
+
+    if (state->fSyncStarted)
+        nSyncStarted--;
+
+    if (state->nMisbehavior == 0 && state->fCurrentlyConnected) {
+        fUpdateConnectionTime = true;
+    }
+
+    for (const QueuedBlock& entry : state->vBlocksInFlight) {
+        mapBlocksInFlight.erase(entry.hash);
+    }
+    EraseOrphansFor(nodeid);
+    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);
+
+    if (mapNodeState.empty()) {
+        // Do a consistency check after the last peer is removed.
+        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);
+}
+
 bool GetNodeStateStats(NodeId nodeid, CNodeStateStats &stats) {
     LOCK(cs_main);
     CNodeState *state = State(nodeid);
@@ -558,22 +621,6 @@ bool GetNodeStateStats(NodeId nodeid, CNodeStateStats &stats) {
     return true;
 }
 
-void RegisterNodeSignals(CNodeSignals& nodeSignals)
-{
-    nodeSignals.ProcessMessages.connect(&ProcessMessages);
-    nodeSignals.SendMessages.connect(&SendMessages);
-    nodeSignals.InitializeNode.connect(&InitializeNode);
-    nodeSignals.FinalizeNode.connect(&FinalizeNode);
-}
-
-void UnregisterNodeSignals(CNodeSignals& nodeSignals)
-{
-    nodeSignals.ProcessMessages.disconnect(&ProcessMessages);
-    nodeSignals.SendMessages.disconnect(&SendMessages);
-    nodeSignals.InitializeNode.disconnect(&InitializeNode);
-    nodeSignals.FinalizeNode.disconnect(&FinalizeNode);
-}
-
 //////////////////////////////////////////////////////////////////////////////
 //
 // mapOrphanTransactions
@@ -725,9 +772,17 @@ void Misbehaving(NodeId pnode, int howmuch)
 // blockchain -> download logic notification
 //
 
-PeerLogicValidation::PeerLogicValidation(CConnman* connmanIn) : connman(connmanIn) {
+PeerLogicValidation::PeerLogicValidation(CConnman* connmanIn, CScheduler &scheduler) : connman(connmanIn), m_stale_tip_check_time(0) {
     // Initialize global variables that cannot be constructed at startup.
     recentRejects.reset(new CRollingBloomFilter(120000, 0.000001));
+
+    const Consensus::Params& consensusParams = Params().GetConsensus();
+    // Stale tip checking and peer eviction are on two different timers, but we
+    // don't want them to get out of sync due to drift in the scheduler, so we
+    // combine them in one function and schedule at the quicker (peer-eviction)
+    // timer.
+    static_assert(EXTRA_PEER_CHECK_INTERVAL < STALE_CHECK_INTERVAL, "peer eviction timer should be less than stale tip check timer");
+    scheduler.scheduleEvery(std::bind(&PeerLogicValidation::CheckForStaleTipAndEvictPeers, this, consensusParams), EXTRA_PEER_CHECK_INTERVAL * 1000);
 }
 
 void PeerLogicValidation::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindex, const std::vector<CTransactionRef>& vtxConflicted) {
@@ -758,6 +813,8 @@ void PeerLogicValidation::BlockConnected(const std::shared_ptr<const CBlock>& pb
         }
         LogPrint(BCLog::MEMPOOL, "Erased %d orphan tx included or conflicted by block\n", nErased);
     }
+
+    g_last_tip_update = GetTime();
 }
 
 // All of the following cache a recent block, and are protected by cs_most_recent_block
@@ -865,7 +922,7 @@ void PeerLogicValidation::BlockChecked(const CBlock& block, const CValidationSta
              !IsInitialBlockDownload() &&
              mapBlocksInFlight.count(hash) == mapBlocksInFlight.size()) {
         if (it != mapBlockSource.end()) {
-            MaybeSetPeerAsAnnouncingHeaderAndIDs(it->second.first, *connman);
+            MaybeSetPeerAsAnnouncingHeaderAndIDs(it->second.first, connman);
         }
     }
     if (it != mapBlockSource.end())
@@ -910,16 +967,16 @@ bool static AlreadyHave(const CInv& inv) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
     return true;
 }
 
-static void RelayTransaction(const CTransaction& tx, CConnman& connman)
+static void RelayTransaction(const CTransaction& tx, CConnman* connman)
 {
     CInv inv(MSG_TX, tx.GetHash());
-    connman.ForEachNode([&inv](CNode* pnode)
+    connman->ForEachNode([&inv](CNode* pnode)
     {
         pnode->PushInventory(inv);
     });
 }
 
-static void RelayAddress(const CAddress& addr, bool fReachable, CConnman& connman)
+static void RelayAddress(const CAddress& addr, bool fReachable, CConnman* connman)
 {
     unsigned int nRelayNodes = fReachable ? 2 : 1; // limited relaying of addresses outside our network(s)
 
@@ -927,7 +984,7 @@ static void RelayAddress(const CAddress& addr, bool fReachable, CConnman& connma
     // Use deterministic randomness to send to the same nodes for 24 hours
     // at a time so the addrKnowns of the chosen nodes prevent repeats
     uint64_t hashAddr = addr.GetHash();
-    const CSipHasher hasher = connman.GetDeterministicRandomizer(RANDOMIZER_ID_ADDRESS_RELAY).Write(hashAddr << 32).Write((GetTime() + hashAddr) / (24*60*60));
+    const CSipHasher hasher = connman->GetDeterministicRandomizer(RANDOMIZER_ID_ADDRESS_RELAY).Write(hashAddr << 32).Write((GetTime() + hashAddr) / (24*60*60));
     FastRandomContext insecure_rand;
 
     std::array<std::pair<uint64_t, CNode*>,2> best{{{0, nullptr}, {0, nullptr}}};
@@ -952,10 +1009,10 @@ static void RelayAddress(const CAddress& addr, bool fReachable, CConnman& connma
         }
     };
 
-    connman.ForEachNodeThen(std::move(sortfunc), std::move(pushfunc));
+    connman->ForEachNodeThen(std::move(sortfunc), std::move(pushfunc));
 }
 
-void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParams, CConnman& connman, const std::atomic<bool>& interruptMsgProc)
+void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParams, CConnman* connman, const std::atomic<bool>& interruptMsgProc)
 {
     std::deque<CInv>::iterator it = pfrom->vRecvGetData.begin();
     std::vector<CInv> vNotFound;
@@ -1017,7 +1074,7 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                 // disconnect node in case we have reached the outbound limit for serving historical blocks
                 // never disconnect whitelisted nodes
                 static const int nOneWeek = 7 * 24 * 60 * 60; // assume > 1 week = historical
-                if (send && connman.OutboundTargetReached(true) && ( ((pindexBestHeader != nullptr) && (pindexBestHeader->GetBlockTime() - mi->second->GetBlockTime() > nOneWeek)) || inv.type == MSG_FILTERED_BLOCK) && !pfrom->fWhitelisted)
+                if (send && connman->OutboundTargetReached(true) && ( ((pindexBestHeader != nullptr) && (pindexBestHeader->GetBlockTime() - mi->second->GetBlockTime() > nOneWeek)) || inv.type == MSG_FILTERED_BLOCK) && !pfrom->fWhitelisted)
                 {
                     LogPrint(BCLog::NET, "historical block serving limit reached, disconnect peer=%d\n", pfrom->GetId());
 
@@ -1040,9 +1097,9 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                         pblock = pblockRead;
                     }
                     if (inv.type == MSG_BLOCK)
-                        connman.PushMessage(pfrom, msgMaker.Make(SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::BLOCK, *pblock));
+                        connman->PushMessage(pfrom, msgMaker.Make(SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::BLOCK, *pblock));
                     else if (inv.type == MSG_WITNESS_BLOCK)
-                        connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::BLOCK, *pblock));
+                        connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::BLOCK, *pblock));
                     else if (inv.type == MSG_FILTERED_BLOCK)
                     {
                         bool sendMerkleBlock = false;
@@ -1055,7 +1112,7 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                             }
                         }
                         if (sendMerkleBlock) {
-                            connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::MERKLEBLOCK, merkleBlock));
+                            connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::MERKLEBLOCK, merkleBlock));
                             // CMerkleBlock just contains hashes, so also push any transactions in the block the client did not see
                             // This avoids hurting performance by pointlessly requiring a round-trip
                             // Note that there is currently no way for a node to request any single transactions we didn't send here -
@@ -1064,7 +1121,7 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                             // however we MUST always provide at least what the remote peer needs
                             typedef std::pair<unsigned int, uint256> PairType;
                             for (PairType& pair : merkleBlock.vMatchedTxn)
-                                connman.PushMessage(pfrom, msgMaker.Make(SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::TX, *pblock->vtx[pair.first]));
+                                connman->PushMessage(pfrom, msgMaker.Make(SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::TX, *pblock->vtx[pair.first]));
                         }
                         // else
                             // no response
@@ -1079,13 +1136,13 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                         int nSendFlags = fPeerWantsWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS;
                         if (CanDirectFetch(consensusParams) && mi->second->nHeight >= chainActive.Height() - MAX_CMPCTBLOCK_DEPTH) {
                             if ((fPeerWantsWitness || !fWitnessesPresentInARecentCompactBlock) && a_recent_compact_block && a_recent_compact_block->header.GetHash() == mi->second->GetBlockHash()) {
-                                connman.PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, *a_recent_compact_block));
+                                connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, *a_recent_compact_block));
                             } else {
                                 CBlockHeaderAndShortTxIDs cmpctblock(*pblock, fPeerWantsWitness);
-                                connman.PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
+                                connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
                             }
                         } else {
-                            connman.PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::BLOCK, *pblock));
+                            connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::BLOCK, *pblock));
                         }
                     }
 
@@ -1097,7 +1154,7 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                         // wait for other stuff first.
                         std::vector<CInv> vInv;
                         vInv.push_back(CInv(MSG_BLOCK, chainActive.Tip()->GetBlockHash()));
-                        connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::INV, vInv));
+                        connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::INV, vInv));
                         pfrom->hashContinue.SetNull();
                     }
                 }
@@ -1109,14 +1166,14 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                 auto mi = mapRelay.find(inv.hash);
                 int nSendFlags = (inv.type == MSG_TX ? SERIALIZE_TRANSACTION_NO_WITNESS : 0);
                 if (mi != mapRelay.end()) {
-                    connman.PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *mi->second));
+                    connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *mi->second));
                     push = true;
                 } else if (pfrom->timeLastMempoolReq) {
                     auto txinfo = mempool.info(inv.hash);
                     // To protect privacy, do not answer getdata using the mempool when
                     // that TX couldn't have been INVed in reply to a MEMPOOL request.
                     if (txinfo.tx && txinfo.nTime <= pfrom->timeLastMempoolReq) {
-                        connman.PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *txinfo.tx));
+                        connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::TX, *txinfo.tx));
                         push = true;
                     }
                 }
@@ -1143,7 +1200,7 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
         // do that because they want to know about (and store and rebroadcast and
         // risk analyze) the dependencies of transactions relevant to them, without
         // having to download the entire memory pool.
-        connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::NOTFOUND, vNotFound));
+        connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::NOTFOUND, vNotFound));
     }
 }
 
@@ -1155,7 +1212,7 @@ uint32_t GetFetchFlags(CNode* pfrom) {
     return nFetchFlags;
 }
 
-inline void static SendBlockTransactions(const CBlock& block, const BlockTransactionsRequest& req, CNode* pfrom, CConnman& connman) {
+inline void static SendBlockTransactions(const CBlock& block, const BlockTransactionsRequest& req, CNode* pfrom, CConnman* connman) {
     BlockTransactions resp(req);
     for (size_t i = 0; i < req.indexes.size(); i++) {
         if (req.indexes[i] >= block.vtx.size()) {
@@ -1169,10 +1226,229 @@ inline void static SendBlockTransactions(const CBlock& block, const BlockTransac
     LOCK(cs_main);
     const CNetMsgMaker msgMaker(pfrom->GetSendVersion());
     int nSendFlags = State(pfrom->GetId())->fWantsCmpctWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS;
-    connman.PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::BLOCKTXN, resp));
+    connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::BLOCKTXN, resp));
 }
 
-bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStream& vRecv, int64_t nTimeReceived, const CChainParams& chainparams, CConnman& connman, const std::atomic<bool>& interruptMsgProc)
+bool static ProcessHeadersMessage(CNode *pfrom, CConnman *connman, const std::vector<CBlockHeader>& headers, const CChainParams& chainparams, bool punish_duplicate_invalid)
+{
+    const CNetMsgMaker msgMaker(pfrom->GetSendVersion());
+    size_t nCount = headers.size();
+
+    if (nCount == 0) {
+        // Nothing interesting. Stop asking this peers for more headers.
+        return true;
+    }
+
+    bool received_new_header = false;
+    const CBlockIndex *pindexLast = nullptr;
+    {
+        LOCK(cs_main);
+        CNodeState *nodestate = State(pfrom->GetId());
+
+        // If this looks like it could be a block announcement (nCount <
+        // MAX_BLOCKS_TO_ANNOUNCE), use special logic for handling headers that
+        // don't connect:
+        // - Send a getheaders message in response to try to connect the chain.
+        // - The peer can send up to MAX_UNCONNECTING_HEADERS in a row that
+        //   don't connect before giving DoS points
+        // - Once a headers message is received that is valid and does connect,
+        //   nUnconnectingHeaders gets reset back to 0.
+        if (mapBlockIndex.find(headers[0].hashPrevBlock) == mapBlockIndex.end() && nCount < MAX_BLOCKS_TO_ANNOUNCE) {
+            nodestate->nUnconnectingHeaders++;
+            connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256()));
+            LogPrint(BCLog::NET, "received header %s: missing prev block %s, sending getheaders (%d) to end (peer=%d, nUnconnectingHeaders=%d)\n",
+                    headers[0].GetHash().ToString(),
+                    headers[0].hashPrevBlock.ToString(),
+                    pindexBestHeader->nHeight,
+                    pfrom->GetId(), nodestate->nUnconnectingHeaders);
+            // Set hashLastUnknownBlock for this peer, so that if we
+            // eventually get the headers - even from a different peer -
+            // we can use this peer to download.
+            UpdateBlockAvailability(pfrom->GetId(), headers.back().GetHash());
+
+            if (nodestate->nUnconnectingHeaders % MAX_UNCONNECTING_HEADERS == 0) {
+                Misbehaving(pfrom->GetId(), 20);
+            }
+            return true;
+        }
+
+        uint256 hashLastBlock;
+        for (const CBlockHeader& header : headers) {
+            if (!hashLastBlock.IsNull() && header.hashPrevBlock != hashLastBlock) {
+                Misbehaving(pfrom->GetId(), 20);
+                return error("non-continuous headers sequence");
+            }
+            hashLastBlock = header.GetHash();
+        }
+
+        // If we don't have the last header, then they'll have given us
+        // something new (if these headers are valid).
+        if (mapBlockIndex.find(hashLastBlock) == mapBlockIndex.end()) {
+            received_new_header = true;
+        }
+    }
+
+    CValidationState state;
+    CBlockHeader first_invalid_header;
+    if (!ProcessNewBlockHeaders(headers, state, chainparams, &pindexLast, &first_invalid_header)) {
+        int nDoS;
+        if (state.IsInvalid(nDoS)) {
+            LOCK(cs_main);
+            if (nDoS > 0) {
+                Misbehaving(pfrom->GetId(), nDoS);
+            }
+            if (punish_duplicate_invalid && mapBlockIndex.find(first_invalid_header.GetHash()) != mapBlockIndex.end()) {
+                // Goal: don't allow outbound peers to use up our outbound
+                // connection slots if they are on incompatible chains.
+                //
+                // We ask the caller to set punish_invalid appropriately based
+                // on the peer and the method of header delivery (compact
+                // blocks are allowed to be invalid in some circumstances,
+                // under BIP 152).
+                // Here, we try to detect the narrow situation that we have a
+                // valid block header (ie it was valid at the time the header
+                // was received, and hence stored in mapBlockIndex) but know the
+                // block is invalid, and that a peer has announced that same
+                // block as being on its active chain.
+                // Disconnect the peer in such a situation.
+                //
+                // Note: if the header that is invalid was not accepted to our
+                // mapBlockIndex at all, that may also be grounds for
+                // disconnecting the peer, as the chain they are on is likely
+                // to be incompatible. However, there is a circumstance where
+                // that does not hold: if the header's timestamp is more than
+                // 2 hours ahead of our current time. In that case, the header
+                // may become valid in the future, and we don't want to
+                // disconnect a peer merely for serving us one too-far-ahead
+                // block header, to prevent an attacker from splitting the
+                // network by mining a block right at the 2 hour boundary.
+                //
+                // TODO: update the DoS logic (or, rather, rewrite the
+                // DoS-interface between validation and net_processing) so that
+                // the interface is cleaner, and so that we disconnect on all the
+                // reasons that a peer's headers chain is incompatible
+                // with ours (eg block->nVersion softforks, MTP violations,
+                // etc), and not just the duplicate-invalid case.
+                pfrom->fDisconnect = true;
+            }
+            return error("invalid header received");
+        }
+    }
+
+    {
+        LOCK(cs_main);
+        CNodeState *nodestate = State(pfrom->GetId());
+        if (nodestate->nUnconnectingHeaders > 0) {
+            LogPrint(BCLog::NET, "peer=%d: resetting nUnconnectingHeaders (%d -> 0)\n", pfrom->GetId(), nodestate->nUnconnectingHeaders);
+        }
+        nodestate->nUnconnectingHeaders = 0;
+
+        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 (received_new_header && pindexLast->nChainWork > chainActive.Tip()->nChainWork) {
+            nodestate->m_last_block_announcement = GetTime();
+        }
+
+        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
+            // from there instead.
+            LogPrint(BCLog::NET, "more getheaders (%d) to end to peer=%d (startheight:%d)\n", pindexLast->nHeight, pfrom->GetId(), pfrom->nStartingHeight);
+            connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexLast), uint256()));
+        }
+
+        bool fCanDirectFetch = CanDirectFetch(chainparams.GetConsensus());
+        // If this set of headers is valid and ends in a block with at least as
+        // much work as our tip, download as much as possible.
+        if (fCanDirectFetch && pindexLast->IsValid(BLOCK_VALID_TREE) && chainActive.Tip()->nChainWork <= pindexLast->nChainWork) {
+            std::vector<const CBlockIndex*> vToFetch;
+            const CBlockIndex *pindexWalk = pindexLast;
+            // Calculate all the blocks we'd need to switch to pindexLast, up to a limit.
+            while (pindexWalk && !chainActive.Contains(pindexWalk) && vToFetch.size() <= MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
+                if (!(pindexWalk->nStatus & BLOCK_HAVE_DATA) &&
+                        !mapBlocksInFlight.count(pindexWalk->GetBlockHash()) &&
+                        (!IsWitnessEnabled(pindexWalk->pprev, chainparams.GetConsensus()) || State(pfrom->GetId())->fHaveWitness)) {
+                    // We don't have this block, and it's not yet in flight.
+                    vToFetch.push_back(pindexWalk);
+                }
+                pindexWalk = pindexWalk->pprev;
+            }
+            // If pindexWalk still isn't on our main chain, we're looking at a
+            // very large reorg at a time we think we're close to caught up to
+            // the main chain -- this shouldn't really happen.  Bail out on the
+            // direct fetch and rely on parallel download instead.
+            if (!chainActive.Contains(pindexWalk)) {
+                LogPrint(BCLog::NET, "Large reorg, won't direct fetch to %s (%d)\n",
+                        pindexLast->GetBlockHash().ToString(),
+                        pindexLast->nHeight);
+            } else {
+                std::vector<CInv> vGetData;
+                // Download as much as possible, from earliest to latest.
+                for (const CBlockIndex *pindex : reverse_iterate(vToFetch)) {
+                    if (nodestate->nBlocksInFlight >= MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
+                        // Can't download any more from this peer
+                        break;
+                    }
+                    uint32_t nFetchFlags = GetFetchFlags(pfrom);
+                    vGetData.push_back(CInv(MSG_BLOCK | nFetchFlags, pindex->GetBlockHash()));
+                    MarkBlockAsInFlight(pfrom->GetId(), pindex->GetBlockHash(), pindex);
+                    LogPrint(BCLog::NET, "Requesting block %s from  peer=%d\n",
+                            pindex->GetBlockHash().ToString(), pfrom->GetId());
+                }
+                if (vGetData.size() > 1) {
+                    LogPrint(BCLog::NET, "Downloading blocks toward %s (%d) via headers direct fetch\n",
+                            pindexLast->GetBlockHash().ToString(), pindexLast->nHeight);
+                }
+                if (vGetData.size() > 0) {
+                    if (nodestate->fSupportsDesiredCmpctVersion && vGetData.size() == 1 && mapBlocksInFlight.size() == 1 && pindexLast->pprev->IsValid(BLOCK_VALID_CHAIN)) {
+                        // In any case, we want to download using a compact block, not a regular one
+                        vGetData[0] = CInv(MSG_CMPCT_BLOCK, vGetData[0].hash);
+                    }
+                    connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vGetData));
+                }
+            }
+        }
+        // If we're in IBD, we want outbound peers that will serve us a useful
+        // chain. Disconnect peers that are on chains with insufficient work.
+        if (IsInitialBlockDownload() && nCount != MAX_HEADERS_RESULTS) {
+            // When nCount < MAX_HEADERS_RESULTS, we know we have no more
+            // headers to fetch from this peer.
+            if (nodestate->pindexBestKnownBlock && nodestate->pindexBestKnownBlock->nChainWork < nMinimumChainWork) {
+                // This peer has too little work on their headers chain to help
+                // us sync -- disconnect if using an outbound slot (unless
+                // whitelisted or addnode).
+                // Note: We compare their tip to nMinimumChainWork (rather than
+                // 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,
+                // 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) {
+                LogPrint(BCLog::NET, "Protecting outbound peer=%d from eviction\n", pfrom->GetId());
+                nodestate->m_chain_sync.m_protect = true;
+                ++g_outbound_peers_with_protect_from_disconnect;
+            }
+        }
+    }
+
+    return true;
+}
+
+bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStream& vRecv, int64_t nTimeReceived, const CChainParams& chainparams, CConnman* connman, const std::atomic<bool>& interruptMsgProc)
 {
     LogPrint(BCLog::NET, "received: %s (%u bytes) peer=%d\n", SanitizeString(strCommand), vRecv.size(), pfrom->GetId());
     if (gArgs.IsArgSet("-dropmessagestest") && GetRand(gArgs.GetArg("-dropmessagestest", 0)) == 0)
@@ -1225,7 +1501,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         // Each connection can only send one version message
         if (pfrom->nVersion != 0)
         {
-            connman.PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_DUPLICATE, std::string("Duplicate version message")));
+            connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_DUPLICATE, std::string("Duplicate version message")));
             LOCK(cs_main);
             Misbehaving(pfrom->GetId(), 1);
             return false;
@@ -1249,12 +1525,12 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         nServices = ServiceFlags(nServiceInt);
         if (!pfrom->fInbound)
         {
-            connman.SetServices(pfrom->addr, nServices);
+            connman->SetServices(pfrom->addr, nServices);
         }
         if (pfrom->nServicesExpected & ~nServices)
         {
             LogPrint(BCLog::NET, "peer=%d does not offer the expected services (%08x offered, %08x expected); disconnecting\n", pfrom->GetId(), nServices, pfrom->nServicesExpected);
-            connman.PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_NONSTANDARD,
+            connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_NONSTANDARD,
                                strprintf("Expected to offer services %08x", pfrom->nServicesExpected)));
             pfrom->fDisconnect = true;
             return false;
@@ -1275,7 +1551,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         {
             // disconnect from peers older than this proto version
             LogPrintf("peer=%d using obsolete version %i; disconnecting\n", pfrom->GetId(), nVersion);
-            connman.PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_OBSOLETE,
+            connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_OBSOLETE,
                                strprintf("Version must be %d or greater", MIN_PEER_PROTO_VERSION)));
             pfrom->fDisconnect = true;
             return false;
@@ -1295,7 +1571,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         if (!vRecv.empty())
             vRecv >> fRelay;
         // Disconnect if we connected to ourself
-        if (pfrom->fInbound && !connman.CheckIncomingNonce(nNonce))
+        if (pfrom->fInbound && !connman->CheckIncomingNonce(nNonce))
         {
             LogPrintf("connected to self at %s, disconnecting\n", pfrom->addr.ToString());
             pfrom->fDisconnect = true;
@@ -1311,7 +1587,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         if (pfrom->fInbound)
             PushNodeVersion(pfrom, connman, GetAdjustedTime());
 
-        connman.PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::VERACK));
+        connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::VERACK));
 
         pfrom->nServices = nServices;
         pfrom->SetAddrLocal(addrMe);
@@ -1362,12 +1638,12 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             }
 
             // Get recent addresses
-            if (pfrom->fOneShot || pfrom->nVersion >= CADDR_TIME_VERSION || connman.GetAddressCount() < 1000)
+            if (pfrom->fOneShot || pfrom->nVersion >= CADDR_TIME_VERSION || connman->GetAddressCount() < 1000)
             {
-                connman.PushMessage(pfrom, CNetMsgMaker(nSendVersion).Make(NetMsgType::GETADDR));
+                connman->PushMessage(pfrom, CNetMsgMaker(nSendVersion).Make(NetMsgType::GETADDR));
                 pfrom->fGetAddr = true;
             }
-            connman.MarkAddressGood(pfrom->addr);
+            connman->MarkAddressGood(pfrom->addr);
         }
 
         std::string remoteAddr;
@@ -1386,7 +1662,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         // If the peer is old enough to have the old alert system, send it the final alert.
         if (pfrom->nVersion <= 70012) {
             CDataStream finalAlert(ParseHex("60010000000000000000000000ffffff7f00000000ffffff7ffeffff7f01ffffff7f00000000ffffff7f00ffffff7f002f555247454e543a20416c657274206b657920636f6d70726f6d697365642c2075706772616465207265717569726564004630440220653febd6410f470f6bae11cad19c48413becb1ac2c17f908fd0fd53bdc3abd5202206d0e9c96fe88d4a0f01ed9dedae2b6f9e00da94cad0fecaae66ecf689bf71b50"), SER_NETWORK, PROTOCOL_VERSION);
-            connman.PushMessage(pfrom, CNetMsgMaker(nSendVersion).Make("alert", finalAlert));
+            connman->PushMessage(pfrom, CNetMsgMaker(nSendVersion).Make("alert", finalAlert));
         }
 
         // Feeler connections exist only to verify if address is online.
@@ -1424,7 +1700,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             // We send this to non-NODE NETWORK peers as well, because even
             // non-NODE NETWORK peers can announce blocks (such as pruning
             // nodes)
-            connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDHEADERS));
+            connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDHEADERS));
         }
         if (pfrom->nVersion >= SHORT_IDS_BLOCKS_VERSION) {
             // Tell our peer we are willing to provide version 1 or 2 cmpctblocks
@@ -1435,9 +1711,9 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             bool fAnnounceUsingCMPCTBLOCK = false;
             uint64_t nCMPCTBLOCKVersion = 2;
             if (pfrom->GetLocalServices() & NODE_WITNESS)
-                connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
+                connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
             nCMPCTBLOCKVersion = 1;
-            connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
+            connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDCMPCT, fAnnounceUsingCMPCTBLOCK, nCMPCTBLOCKVersion));
         }
         pfrom->fSuccessfullyConnected = true;
     }
@@ -1456,7 +1732,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         vRecv >> vAddr;
 
         // Don't want addr from older versions unless seeding
-        if (pfrom->nVersion < CADDR_TIME_VERSION && connman.GetAddressCount() > 1000)
+        if (pfrom->nVersion < CADDR_TIME_VERSION && connman->GetAddressCount() > 1000)
             return true;
         if (vAddr.size() > 1000)
         {
@@ -1490,7 +1766,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             if (fReachable)
                 vAddrOk.push_back(addr);
         }
-        connman.AddNewAddresses(vAddrOk, pfrom->addr, 2 * 60 * 60);
+        connman->AddNewAddresses(vAddrOk, pfrom->addr, 2 * 60 * 60);
         if (vAddr.size() < 1000)
             pfrom->fGetAddr = false;
         if (pfrom->fOneShot)
@@ -1568,7 +1844,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                     // fell back to inv we probably have a reorg which we should get the headers for first,
                     // we now only provide a getheaders response here. When we receive the headers, we will
                     // then ask for the blocks we need.
-                    connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), inv.hash));
+                    connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), inv.hash));
                     LogPrint(BCLog::NET, "getheaders (%d) %s to peer=%d\n", pindexBestHeader->nHeight, inv.hash.ToString(), pfrom->GetId());
                 }
             }
@@ -1774,7 +2050,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         // will re-announce the new block via headers (or compact blocks again)
         // in the SendMessages logic.
         nodestate->pindexBestHeaderSent = pindex ? pindex : chainActive.Tip();
-        connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::HEADERS, vHeaders));
+        connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::HEADERS, vHeaders));
     }
 
 
@@ -1955,7 +2231,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                 pfrom->GetId(),
                 FormatStateMessage(state));
             if (state.GetRejectCode() > 0 && state.GetRejectCode() < REJECT_INTERNAL) // Never send AcceptToMemoryPool's internal codes over P2P
-                connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::REJECT, strCommand, (unsigned char)state.GetRejectCode(),
+                connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::REJECT, strCommand, (unsigned char)state.GetRejectCode(),
                                    state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), inv.hash));
             if (nDoS > 0) {
                 Misbehaving(pfrom->GetId(), nDoS);
@@ -1969,15 +2245,21 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         CBlockHeaderAndShortTxIDs cmpctblock;
         vRecv >> cmpctblock;
 
+        bool received_new_header = false;
+
         {
         LOCK(cs_main);
 
         if (mapBlockIndex.find(cmpctblock.header.hashPrevBlock) == mapBlockIndex.end()) {
             // Doesn't connect (or is genesis), instead of DoSing in AcceptBlockHeader, request deeper headers
             if (!IsInitialBlockDownload())
-                connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256()));
+                connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256()));
             return true;
         }
+
+        if (mapBlockIndex.find(cmpctblock.header.GetHash()) == mapBlockIndex.end()) {
+            received_new_header = true;
+        }
         }
 
         const CBlockIndex *pindex = nullptr;
@@ -2004,7 +2286,6 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         // If we end up treating this as a plain headers message, call that as well
         // without cs_main.
         bool fRevertToHeaderProcessing = false;
-        CDataStream vHeadersMsg(SER_NETWORK, PROTOCOL_VERSION);
 
         // Keep a CBlock for "optimistic" compactblock reconstructions (see
         // below)
@@ -2017,6 +2298,14 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         assert(pindex);
         UpdateBlockAvailability(pfrom->GetId(), pindex->GetBlockHash());
 
+        CNodeState *nodestate = State(pfrom->GetId());
+
+        // If this was a new header with more work than our tip, update the
+        // peer's last block announcement time
+        if (received_new_header && pindex->nChainWork > chainActive.Tip()->nChainWork) {
+            nodestate->m_last_block_announcement = GetTime();
+        }
+
         std::map<uint256, std::pair<NodeId, std::list<QueuedBlock>::iterator> >::iterator blockInFlightIt = mapBlocksInFlight.find(pindex->GetBlockHash());
         bool fAlreadyInFlight = blockInFlightIt != mapBlocksInFlight.end();
 
@@ -2030,7 +2319,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                 // so we just grab the block via normal getdata
                 std::vector<CInv> vInv(1);
                 vInv[0] = CInv(MSG_BLOCK | GetFetchFlags(pfrom), cmpctblock.header.GetHash());
-                connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
+                connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
             }
             return true;
         }
@@ -2039,8 +2328,6 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         if (!fAlreadyInFlight && !CanDirectFetch(chainparams.GetConsensus()))
             return true;
 
-        CNodeState *nodestate = State(pfrom->GetId());
-
         if (IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) && !nodestate->fSupportsDesiredCmpctVersion) {
             // Don't bother trying to process compact blocks from v1 peers
             // after segwit activates.
@@ -2074,7 +2361,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                     // Duplicate txindexes, the block is now in-flight, so just request it
                     std::vector<CInv> vInv(1);
                     vInv[0] = CInv(MSG_BLOCK | GetFetchFlags(pfrom), cmpctblock.header.GetHash());
-                    connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
+                    connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
                     return true;
                 }
 
@@ -2091,7 +2378,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                     fProcessBLOCKTXN = true;
                 } else {
                     req.blockhash = pindex->GetBlockHash();
-                    connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETBLOCKTXN, req));
+                    connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETBLOCKTXN, req));
                 }
             } else {
                 // This block is either already in flight from a different
@@ -2117,14 +2404,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                 // mempool will probably be useless - request the block normally
                 std::vector<CInv> vInv(1);
                 vInv[0] = CInv(MSG_BLOCK | GetFetchFlags(pfrom), cmpctblock.header.GetHash());
-                connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
+                connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vInv));
                 return true;
             } else {
                 // If this was an announce-cmpctblock, we want the same treatment as a header message
-                // Dirty hack to process as if it were just a headers message (TODO: move message handling into their own functions)
-                std::vector<CBlock> headers;
-                headers.push_back(cmpctblock.header);
-                vHeadersMsg << headers;
                 fRevertToHeaderProcessing = true;
             }
         }
@@ -2133,8 +2416,14 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         if (fProcessBLOCKTXN)
             return ProcessMessage(pfrom, NetMsgType::BLOCKTXN, blockTxnMsg, nTimeReceived, chainparams, connman, interruptMsgProc);
 
-        if (fRevertToHeaderProcessing)
-            return ProcessMessage(pfrom, NetMsgType::HEADERS, vHeadersMsg, nTimeReceived, chainparams, connman, interruptMsgProc);
+        if (fRevertToHeaderProcessing) {
+            // Headers received from HB compact block peers are permitted to be
+            // relayed before full validation (see BIP 152), so we don't want to disconnect
+            // the peer if the header turns out to be for an invalid block.
+            // Note that if a peer tries to build on an invalid chain, that
+            // will be detected and the peer will be banned.
+            return ProcessHeadersMessage(pfrom, connman, {cmpctblock.header}, chainparams, /*punish_duplicate_invalid=*/false);
+        }
 
         if (fBlockReconstructed) {
             // If we got here, we were able to optimistically reconstruct a
@@ -2144,7 +2433,16 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                 mapBlockSource.emplace(pblock->GetHash(), std::make_pair(pfrom->GetId(), false));
             }
             bool fNewBlock = false;
-            ProcessNewBlock(chainparams, pblock, true, &fNewBlock);
+            // Setting fForceProcessing to true means that we bypass some of
+            // our anti-DoS protections in AcceptBlock, which filters
+            // unrequested blocks that might be trying to waste our resources
+            // (eg disk space). Because we only try to reconstruct blocks when
+            // we're close to caught up (via the CanDirectFetch() requirement
+            // above, combined with the behavior of not requesting blocks until
+            // we have a chain with at least nMinimumChainWork), and we ignore
+            // compact blocks with less work than our tip, it is safe to treat
+            // reconstructed compact blocks as having been requested.
+            ProcessNewBlock(chainparams, pblock, /*fForceProcessing=*/true, &fNewBlock);
             if (fNewBlock) {
                 pfrom->nLastBlockTime = GetTime();
             } else {
@@ -2191,7 +2489,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
                 // Might have collided, fall back to getdata now :(
                 std::vector<CInv> invs;
                 invs.push_back(CInv(MSG_BLOCK | GetFetchFlags(pfrom), resp.blockhash));
-                connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, invs));
+                connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, invs));
             } else {
                 // Block is either okay, or possibly we received
                 // READ_STATUS_CHECKBLOCK_FAILED.
@@ -2224,7 +2522,11 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             bool fNewBlock = false;
             // Since we requested this block (it was in mapBlocksInFlight), force it to be processed,
             // even if it would not be a candidate for new tip (missing previous block, chain not long enough, etc)
-            ProcessNewBlock(chainparams, pblock, true, &fNewBlock);
+            // This bypasses some anti-DoS logic in AcceptBlock (eg to prevent
+            // disk-space attacks), but this should be safe due to the
+            // protections in the compact block handler -- see related comment
+            // in compact block optimistic reconstruction handling.
+            ProcessNewBlock(chainparams, pblock, /*fForceProcessing=*/true, &fNewBlock);
             if (fNewBlock) {
                 pfrom->nLastBlockTime = GetTime();
             } else {
@@ -2252,136 +2554,12 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             ReadCompactSize(vRecv); // ignore tx count; assume it is 0.
         }
 
-        if (nCount == 0) {
-            // Nothing interesting. Stop asking this peers for more headers.
-            return true;
-        }
-
-        const CBlockIndex *pindexLast = nullptr;
-        {
-        LOCK(cs_main);
-        CNodeState *nodestate = State(pfrom->GetId());
-
-        // If this looks like it could be a block announcement (nCount <
-        // MAX_BLOCKS_TO_ANNOUNCE), use special logic for handling headers that
-        // don't connect:
-        // - Send a getheaders message in response to try to connect the chain.
-        // - The peer can send up to MAX_UNCONNECTING_HEADERS in a row that
-        //   don't connect before giving DoS points
-        // - Once a headers message is received that is valid and does connect,
-        //   nUnconnectingHeaders gets reset back to 0.
-        if (mapBlockIndex.find(headers[0].hashPrevBlock) == mapBlockIndex.end() && nCount < MAX_BLOCKS_TO_ANNOUNCE) {
-            nodestate->nUnconnectingHeaders++;
-            connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256()));
-            LogPrint(BCLog::NET, "received header %s: missing prev block %s, sending getheaders (%d) to end (peer=%d, nUnconnectingHeaders=%d)\n",
-                    headers[0].GetHash().ToString(),
-                    headers[0].hashPrevBlock.ToString(),
-                    pindexBestHeader->nHeight,
-                    pfrom->GetId(), nodestate->nUnconnectingHeaders);
-            // Set hashLastUnknownBlock for this peer, so that if we
-            // eventually get the headers - even from a different peer -
-            // we can use this peer to download.
-            UpdateBlockAvailability(pfrom->GetId(), headers.back().GetHash());
-
-            if (nodestate->nUnconnectingHeaders % MAX_UNCONNECTING_HEADERS == 0) {
-                Misbehaving(pfrom->GetId(), 20);
-            }
-            return true;
-        }
-
-        uint256 hashLastBlock;
-        for (const CBlockHeader& header : headers) {
-            if (!hashLastBlock.IsNull() && header.hashPrevBlock != hashLastBlock) {
-                Misbehaving(pfrom->GetId(), 20);
-                return error("non-continuous headers sequence");
-            }
-            hashLastBlock = header.GetHash();
-        }
-        }
-
-        CValidationState state;
-        if (!ProcessNewBlockHeaders(headers, state, chainparams, &pindexLast)) {
-            int nDoS;
-            if (state.IsInvalid(nDoS)) {
-                if (nDoS > 0) {
-                    LOCK(cs_main);
-                    Misbehaving(pfrom->GetId(), nDoS);
-                }
-                return error("invalid header received");
-            }
-        }
-
-        {
-        LOCK(cs_main);
-        CNodeState *nodestate = State(pfrom->GetId());
-        if (nodestate->nUnconnectingHeaders > 0) {
-            LogPrint(BCLog::NET, "peer=%d: resetting nUnconnectingHeaders (%d -> 0)\n", pfrom->GetId(), nodestate->nUnconnectingHeaders);
-        }
-        nodestate->nUnconnectingHeaders = 0;
-
-        assert(pindexLast);
-        UpdateBlockAvailability(pfrom->GetId(), pindexLast->GetBlockHash());
-
-        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
-            // from there instead.
-            LogPrint(BCLog::NET, "more getheaders (%d) to end to peer=%d (startheight:%d)\n", pindexLast->nHeight, pfrom->GetId(), pfrom->nStartingHeight);
-            connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexLast), uint256()));
-        }
-
-        bool fCanDirectFetch = CanDirectFetch(chainparams.GetConsensus());
-        // If this set of headers is valid and ends in a block with at least as
-        // much work as our tip, download as much as possible.
-        if (fCanDirectFetch && pindexLast->IsValid(BLOCK_VALID_TREE) && chainActive.Tip()->nChainWork <= pindexLast->nChainWork) {
-            std::vector<const CBlockIndex*> vToFetch;
-            const CBlockIndex *pindexWalk = pindexLast;
-            // Calculate all the blocks we'd need to switch to pindexLast, up to a limit.
-            while (pindexWalk && !chainActive.Contains(pindexWalk) && vToFetch.size() <= MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
-                if (!(pindexWalk->nStatus & BLOCK_HAVE_DATA) &&
-                        !mapBlocksInFlight.count(pindexWalk->GetBlockHash()) &&
-                        (!IsWitnessEnabled(pindexWalk->pprev, chainparams.GetConsensus()) || State(pfrom->GetId())->fHaveWitness)) {
-                    // We don't have this block, and it's not yet in flight.
-                    vToFetch.push_back(pindexWalk);
-                }
-                pindexWalk = pindexWalk->pprev;
-            }
-            // If pindexWalk still isn't on our main chain, we're looking at a
-            // very large reorg at a time we think we're close to caught up to
-            // the main chain -- this shouldn't really happen.  Bail out on the
-            // direct fetch and rely on parallel download instead.
-            if (!chainActive.Contains(pindexWalk)) {
-                LogPrint(BCLog::NET, "Large reorg, won't direct fetch to %s (%d)\n",
-                        pindexLast->GetBlockHash().ToString(),
-                        pindexLast->nHeight);
-            } else {
-                std::vector<CInv> vGetData;
-                // Download as much as possible, from earliest to latest.
-                for (const CBlockIndex *pindex : reverse_iterate(vToFetch)) {
-                    if (nodestate->nBlocksInFlight >= MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
-                        // Can't download any more from this peer
-                        break;
-                    }
-                    uint32_t nFetchFlags = GetFetchFlags(pfrom);
-                    vGetData.push_back(CInv(MSG_BLOCK | nFetchFlags, pindex->GetBlockHash()));
-                    MarkBlockAsInFlight(pfrom->GetId(), pindex->GetBlockHash(), pindex);
-                    LogPrint(BCLog::NET, "Requesting block %s from  peer=%d\n",
-                            pindex->GetBlockHash().ToString(), pfrom->GetId());
-                }
-                if (vGetData.size() > 1) {
-                    LogPrint(BCLog::NET, "Downloading blocks toward %s (%d) via headers direct fetch\n",
-                            pindexLast->GetBlockHash().ToString(), pindexLast->nHeight);
-                }
-                if (vGetData.size() > 0) {
-                    if (nodestate->fSupportsDesiredCmpctVersion && vGetData.size() == 1 && mapBlocksInFlight.size() == 1 && pindexLast->pprev->IsValid(BLOCK_VALID_CHAIN)) {
-                        // In any case, we want to download using a compact block, not a regular one
-                        vGetData[0] = CInv(MSG_CMPCT_BLOCK, vGetData[0].hash);
-                    }
-                    connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vGetData));
-                }
-            }
-        }
-        }
+        // Headers received via a HEADERS message should be valid, and reflect
+        // the chain the peer is on. If we receive a known-invalid header,
+        // disconnect the peer if it is using one of our outbound connection
+        // slots.
+        bool should_punish = !pfrom->fInbound && !pfrom->m_manual_connection;
+        return ProcessHeadersMessage(pfrom, connman, headers, chainparams, should_punish);
     }
 
     else if (strCommand == NetMsgType::BLOCK && !fImporting && !fReindex) // Ignore blocks received while importing
@@ -2391,11 +2569,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
 
         LogPrint(BCLog::NET, "received block %s peer=%d\n", pblock->GetHash().ToString(), pfrom->GetId());
 
-        // Process all blocks from whitelisted peers, even if not requested,
-        // unless we're still syncing with the network.
-        // Such an unrequested block may still be processed, subject to the
-        // conditions in AcceptBlock().
-        bool forceProcessing = pfrom->fWhitelisted && !IsInitialBlockDownload();
+        bool forceProcessing = false;
         const uint256 hash(pblock->GetHash());
         {
             LOCK(cs_main);
@@ -2438,7 +2612,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         pfrom->fSentAddr = true;
 
         pfrom->vAddrToSend.clear();
-        std::vector<CAddress> vAddr = connman.GetAddresses();
+        std::vector<CAddress> vAddr = connman->GetAddresses();
         FastRandomContext insecure_rand;
         for (const CAddress &addr : vAddr)
             pfrom->PushAddress(addr, insecure_rand);
@@ -2454,7 +2628,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             return true;
         }
 
-        if (connman.OutboundTargetReached(false) && !pfrom->fWhitelisted)
+        if (connman->OutboundTargetReached(false) && !pfrom->fWhitelisted)
         {
             LogPrint(BCLog::NET, "mempool request with bandwidth limit reached, disconnect peer=%d\n", pfrom->GetId());
             pfrom->fDisconnect = true;
@@ -2483,7 +2657,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
             // it, if the remote node sends a ping once per second and this node takes 5
             // seconds to respond to each, the 5th ping the remote sends would appear to
             // return very quickly.
-            connman.PushMessage(pfrom, msgMaker.Make(NetMsgType::PONG, nonce));
+            connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::PONG, nonce));
         }
     }
 
@@ -2629,13 +2803,13 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
     return true;
 }
 
-static bool SendRejectsAndCheckIfBanned(CNode* pnode, CConnman& connman)
+static bool SendRejectsAndCheckIfBanned(CNode* pnode, CConnman* connman)
 {
     AssertLockHeld(cs_main);
     CNodeState &state = *State(pnode->GetId());
 
     for (const CBlockReject& reject : state.rejects) {
-        connman.PushMessage(pnode, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, (std::string)NetMsgType::BLOCK, reject.chRejectCode, reject.strRejectReason, reject.hashBlock));
+        connman->PushMessage(pnode, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, (std::string)NetMsgType::BLOCK, reject.chRejectCode, reject.strRejectReason, reject.hashBlock));
     }
     state.rejects.clear();
 
@@ -2643,7 +2817,7 @@ static bool SendRejectsAndCheckIfBanned(CNode* pnode, CConnman& connman)
         state.fShouldBan = false;
         if (pnode->fWhitelisted)
             LogPrintf("Warning: not punishing whitelisted peer %s!\n", pnode->addr.ToString());
-        else if (pnode->fAddnode)
+        else if (pnode->m_manual_connection)
             LogPrintf("Warning: not punishing addnoded peer %s!\n", pnode->addr.ToString());
         else {
             pnode->fDisconnect = true;
@@ -2651,7 +2825,7 @@ static bool SendRejectsAndCheckIfBanned(CNode* pnode, CConnman& connman)
                 LogPrintf("Warning: not banning local peer %s!\n", pnode->addr.ToString());
             else
             {
-                connman.Ban(pnode->addr, BanReasonNodeMisbehaving);
+                connman->Ban(pnode->addr, BanReasonNodeMisbehaving);
             }
         }
         return true;
@@ -2659,7 +2833,7 @@ static bool SendRejectsAndCheckIfBanned(CNode* pnode, CConnman& connman)
     return false;
 }
 
-bool ProcessMessages(CNode* pfrom, CConnman& connman, const std::atomic<bool>& interruptMsgProc)
+bool PeerLogicValidation::ProcessMessages(CNode* pfrom, std::atomic<bool>& interruptMsgProc)
 {
     const CChainParams& chainparams = Params();
     //
@@ -2693,7 +2867,7 @@ bool ProcessMessages(CNode* pfrom, CConnman& connman, const std::atomic<bool>& i
         // Just take one message
         msgs.splice(msgs.begin(), pfrom->vProcessMsg, pfrom->vProcessMsg.begin());
         pfrom->nProcessQueueSize -= msgs.front().vRecv.size() + CMessageHeader::HEADER_SIZE;
-        pfrom->fPauseRecv = pfrom->nProcessQueueSize > connman.GetReceiveFloodSize();
+        pfrom->fPauseRecv = pfrom->nProcessQueueSize > connman->GetReceiveFloodSize();
         fMoreWork = !pfrom->vProcessMsg.empty();
     }
     CNetMessage& msg(msgs.front());
@@ -2742,7 +2916,7 @@ bool ProcessMessages(CNode* pfrom, CConnman& connman, const std::atomic<bool>& i
     }
     catch (const std::ios_base::failure& e)
     {
-        connman.PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_MALFORMED, std::string("error parsing message")));
+        connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_MALFORMED, std::string("error parsing message")));
         if (strstr(e.what(), "end of data"))
         {
             // Allow exceptions from under-length message on vRecv
@@ -2779,6 +2953,135 @@ bool ProcessMessages(CNode* pfrom, CConnman& connman, const std::atomic<bool>& i
     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;
+            }
+        }
+    }
+}
+
+void PeerLogicValidation::EvictExtraOutboundPeers(int64_t time_in_seconds)
+{
+    // Check whether we have too many outbound peers
+    int extra_peers = connman->GetExtraOutboundCount();
+    if (extra_peers > 0) {
+        // If we have more outbound peers than we target, disconnect one.
+        // Pick the outbound peer that least recently announced
+        // us a new block, with ties broken by choosing the more recent
+        // connection (higher node id)
+        NodeId worst_peer = -1;
+        int64_t oldest_block_announcement = std::numeric_limits<int64_t>::max();
+
+        LOCK(cs_main);
+
+        connman->ForEachNode([&](CNode* pnode) {
+            // Ignore non-outbound peers, or nodes marked for disconnect already
+            if (!IsOutboundDisconnectionCandidate(pnode) || pnode->fDisconnect) return;
+            CNodeState *state = State(pnode->GetId());
+            if (state == nullptr) return; // shouldn't be possible, but just in case
+            // Don't evict our protected peers
+            if (state->m_chain_sync.m_protect) return;
+            if (state->m_last_block_announcement < oldest_block_announcement || (state->m_last_block_announcement == oldest_block_announcement && pnode->GetId() > worst_peer)) {
+                worst_peer = pnode->GetId();
+                oldest_block_announcement = state->m_last_block_announcement;
+            }
+        });
+        if (worst_peer != -1) {
+            bool disconnected = connman->ForNode(worst_peer, [&](CNode *pnode) {
+                // Only disconnect a peer that has been connected to us for
+                // some reasonable fraction of our check-frequency, to give
+                // it time for new information to have arrived.
+                // Also don't disconnect any peer we're trying to download a
+                // block from.
+                CNodeState &state = *State(pnode->GetId());
+                if (time_in_seconds - pnode->nTimeConnected > MINIMUM_CONNECT_TIME && state.nBlocksInFlight == 0) {
+                    LogPrint(BCLog::NET, "disconnecting extra outbound peer=%d (last block announcement received at time %d)\n", pnode->GetId(), oldest_block_announcement);
+                    pnode->fDisconnect = true;
+                    return true;
+                } else {
+                    LogPrint(BCLog::NET, "keeping outbound peer=%d chosen for eviction (connect time: %d, blocks_in_flight: %d)\n", pnode->GetId(), pnode->nTimeConnected, state.nBlocksInFlight);
+                    return false;
+                }
+            });
+            if (disconnected) {
+                // If we disconnected an extra peer, that means we successfully
+                // connected to at least one peer after the last time we
+                // detected a stale tip. Don't try any more extra peers until
+                // we next detect a stale tip, to limit the load we put on the
+                // network from these extra connections.
+                connman->SetTryNewOutboundPeer(false);
+            }
+        }
+    }
+}
+
+void PeerLogicValidation::CheckForStaleTipAndEvictPeers(const Consensus::Params &consensusParams)
+{
+    if (connman == nullptr) return;
+
+    int64_t time_in_seconds = GetTime();
+
+    EvictExtraOutboundPeers(time_in_seconds);
+
+    if (time_in_seconds > m_stale_tip_check_time) {
+        LOCK(cs_main);
+        // Check whether our tip is stale, and if so, allow using an extra
+        // outbound peer
+        if (TipMayBeStale(consensusParams)) {
+            LogPrintf("Potential stale tip detected, will try using extra outbound peer (last tip update: %d seconds ago)\n", time_in_seconds - g_last_tip_update);
+            connman->SetTryNewOutboundPeer(true);
+        } else if (connman->GetTryNewOutboundPeer()) {
+            connman->SetTryNewOutboundPeer(false);
+        }
+        m_stale_tip_check_time = time_in_seconds + STALE_CHECK_INTERVAL;
+    }
+}
+
 class CompareInvMempoolOrder
 {
     CTxMemPool *mp;
@@ -2796,7 +3099,7 @@ public:
     }
 };
 
-bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interruptMsgProc)
+bool PeerLogicValidation::SendMessages(CNode* pto, std::atomic<bool>& interruptMsgProc)
 {
     const Consensus::Params& consensusParams = Params().GetConsensus();
     {
@@ -2828,11 +3131,11 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
             pto->nPingUsecStart = GetTimeMicros();
             if (pto->nVersion > BIP0031_VERSION) {
                 pto->nPingNonceSent = nonce;
-                connman.PushMessage(pto, msgMaker.Make(NetMsgType::PING, nonce));
+                connman->PushMessage(pto, msgMaker.Make(NetMsgType::PING, nonce));
             } else {
                 // Peer is too old to support ping command with nonce, pong will never arrive.
                 pto->nPingNonceSent = 0;
-                connman.PushMessage(pto, msgMaker.Make(NetMsgType::PING));
+                connman->PushMessage(pto, msgMaker.Make(NetMsgType::PING));
             }
         }
 
@@ -2867,14 +3170,14 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
                     // receiver rejects addr messages larger than 1000
                     if (vAddr.size() >= 1000)
                     {
-                        connman.PushMessage(pto, msgMaker.Make(NetMsgType::ADDR, vAddr));
+                        connman->PushMessage(pto, msgMaker.Make(NetMsgType::ADDR, vAddr));
                         vAddr.clear();
                     }
                 }
             }
             pto->vAddrToSend.clear();
             if (!vAddr.empty())
-                connman.PushMessage(pto, msgMaker.Make(NetMsgType::ADDR, vAddr));
+                connman->PushMessage(pto, msgMaker.Make(NetMsgType::ADDR, vAddr));
             // we only send the big addr message once
             if (pto->vAddrToSend.capacity() > 40)
                 pto->vAddrToSend.shrink_to_fit();
@@ -2901,7 +3204,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
                 if (pindexStart->pprev)
                     pindexStart = pindexStart->pprev;
                 LogPrint(BCLog::NET, "initial getheaders (%d) to peer=%d (startheight:%d)\n", pindexStart->nHeight, pto->GetId(), pto->nStartingHeight);
-                connman.PushMessage(pto, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexStart), uint256()));
+                connman->PushMessage(pto, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexStart), uint256()));
             }
         }
 
@@ -2910,7 +3213,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
         // transactions become unconfirmed and spams other nodes.
         if (!fReindex && !fImporting && !IsInitialBlockDownload())
         {
-            GetMainSignals().Broadcast(nTimeBestReceived, &connman);
+            GetMainSignals().Broadcast(nTimeBestReceived, connman);
         }
 
         //
@@ -2994,10 +3297,10 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
                         LOCK(cs_most_recent_block);
                         if (most_recent_block_hash == pBestIndex->GetBlockHash()) {
                             if (state.fWantsCmpctWitness || !fWitnessesPresentInMostRecentCompactBlock)
-                                connman.PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, *most_recent_compact_block));
+                                connman->PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, *most_recent_compact_block));
                             else {
                                 CBlockHeaderAndShortTxIDs cmpctblock(*most_recent_block, state.fWantsCmpctWitness);
-                                connman.PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
+                                connman->PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
                             }
                             fGotBlockFromCache = true;
                         }
@@ -3007,7 +3310,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
                         bool ret = ReadBlockFromDisk(block, pBestIndex, consensusParams);
                         assert(ret);
                         CBlockHeaderAndShortTxIDs cmpctblock(block, state.fWantsCmpctWitness);
-                        connman.PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
+                        connman->PushMessage(pto, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, cmpctblock));
                     }
                     state.pindexBestHeaderSent = pBestIndex;
                 } else if (state.fPreferHeaders) {
@@ -3020,7 +3323,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
                         LogPrint(BCLog::NET, "%s: sending header %s to peer=%d\n", __func__,
                                 vHeaders.front().GetHash().ToString(), pto->GetId());
                     }
-                    connman.PushMessage(pto, msgMaker.Make(NetMsgType::HEADERS, vHeaders));
+                    connman->PushMessage(pto, msgMaker.Make(NetMsgType::HEADERS, vHeaders));
                     state.pindexBestHeaderSent = pBestIndex;
                 } else
                     fRevertToInv = true;
@@ -3066,7 +3369,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
             for (const uint256& hash : pto->vInventoryBlockToSend) {
                 vInv.push_back(CInv(MSG_BLOCK, hash));
                 if (vInv.size() == MAX_INV_SZ) {
-                    connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
+                    connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                     vInv.clear();
                 }
             }
@@ -3112,7 +3415,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
                     pto->filterInventoryKnown.insert(hash);
                     vInv.push_back(inv);
                     if (vInv.size() == MAX_INV_SZ) {
-                        connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
+                        connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                         vInv.clear();
                     }
                 }
@@ -3178,7 +3481,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
                         }
                     }
                     if (vInv.size() == MAX_INV_SZ) {
-                        connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
+                        connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                         vInv.clear();
                     }
                     pto->filterInventoryKnown.insert(hash);
@@ -3186,7 +3489,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
             }
         }
         if (!vInv.empty())
-            connman.PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
+            connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
 
         // Detect whether we're stalling
         nNow = GetTimeMicros();
@@ -3245,6 +3548,9 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
             }
         }
 
+        // 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)
@@ -3281,7 +3587,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
                 vGetData.push_back(inv);
                 if (vGetData.size() >= 1000)
                 {
-                    connman.PushMessage(pto, msgMaker.Make(NetMsgType::GETDATA, vGetData));
+                    connman->PushMessage(pto, msgMaker.Make(NetMsgType::GETDATA, vGetData));
                     vGetData.clear();
                 }
             } else {
@@ -3291,7 +3597,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
             pto->mapAskFor.erase(pto->mapAskFor.begin());
         }
         if (!vGetData.empty())
-            connman.PushMessage(pto, msgMaker.Make(NetMsgType::GETDATA, vGetData));
+            connman->PushMessage(pto, msgMaker.Make(NetMsgType::GETDATA, vGetData));
 
         //
         // Message: feefilter
@@ -3308,7 +3614,7 @@ bool SendMessages(CNode* pto, CConnman& connman, const std::atomic<bool>& interr
                 // We always have a fee filter of at least minRelayTxFee
                 filterToSend = std::max(filterToSend, ::minRelayTxFee.GetFeePerK());
                 if (filterToSend != pto->lastSentFeeFilter) {
-                    connman.PushMessage(pto, msgMaker.Make(NetMsgType::FEEFILTER, filterToSend));
+                    connman->PushMessage(pto, msgMaker.Make(NetMsgType::FEEFILTER, filterToSend));
                     pto->lastSentFeeFilter = filterToSend;
                 }
                 pto->nextSendTimeFeeFilter = PoissonNextSend(timeNow, AVG_FEEFILTER_BROADCAST_INTERVAL);