27 files changed, 435 insertions, 347 deletions

diff --git a/contrib/devtools/gen-manpages.sh b/contrib/devtools/gen-manpages.sh
index b933b264e7..b7bf76ce77 100755
--- a/contrib/devtools/gen-manpages.sh
+++ b/contrib/devtools/gen-manpages.sh
@@ -14,13 +14,14 @@ BITCOIND=${BITCOIND:-$BINDIR/bitcoind}
 BITCOINCLI=${BITCOINCLI:-$BINDIR/bitcoin-cli}
 BITCOINTX=${BITCOINTX:-$BINDIR/bitcoin-tx}
 WALLET_TOOL=${WALLET_TOOL:-$BINDIR/bitcoin-wallet}
+BITCOINUTIL=${BITCOINQT:-$BINDIR/bitcoin-util}
 BITCOINQT=${BITCOINQT:-$BINDIR/qt/bitcoin-qt}
 
 [ ! -x $BITCOIND ] && echo "$BITCOIND not found or not executable." && exit 1
 
 # Don't allow man pages to be generated for binaries built from a dirty tree
 DIRTY=""
-for cmd in $BITCOIND $BITCOINCLI $BITCOINTX $WALLET_TOOL $BITCOINQT; do
+for cmd in $BITCOIND $BITCOINCLI $BITCOINTX $WALLET_TOOL $BITCOINUTIL $BITCOINQT; do
   VERSION_OUTPUT=$($cmd --version)
   if [[ $VERSION_OUTPUT == *"dirty"* ]]; then
     DIRTY="${DIRTY}${cmd}\n"
@@ -43,7 +44,7 @@ read -r -a BTCVER <<< "$($BITCOINCLI --version | head -n1 | awk -F'[ -]' '{ prin
 echo "[COPYRIGHT]" > footer.h2m
 $BITCOIND --version | sed -n '1!p' >> footer.h2m
 
-for cmd in $BITCOIND $BITCOINCLI $BITCOINTX $WALLET_TOOL $BITCOINQT; do
+for cmd in $BITCOIND $BITCOINCLI $BITCOINTX $WALLET_TOOL $BITCOINUTIL $BITCOINQT; do
   cmdname="${cmd##*/}"
   help2man -N --version-string=${BTCVER[0]} --include=footer.h2m -o ${MANDIR}/${cmdname}.1 ${cmd}
   sed -i "s/\\\-${BTCVER[1]}//g" ${MANDIR}/${cmdname}.1
diff --git a/doc/man/Makefile.am b/doc/man/Makefile.am
index edbc0911a1..8f890da532 100644
--- a/doc/man/Makefile.am
+++ b/doc/man/Makefile.am
@@ -16,6 +16,10 @@ if BUILD_BITCOIN_TX
   dist_man1_MANS+=bitcoin-tx.1
 endif
 
+if BUILD_BITCOIN_UTIL
+  dist_man1_MANS+=bitcoin-util.1
+endif
+
 if ENABLE_WALLET
 if BUILD_BITCOIN_WALLET
   dist_man1_MANS+=bitcoin-wallet.1
diff --git a/doc/man/bitcoin-cli.1 b/doc/man/bitcoin-cli.1
index 588ae81fce..6bcad7006b 100644
--- a/doc/man/bitcoin-cli.1
+++ b/doc/man/bitcoin-cli.1
@@ -2,4 +2,4 @@
 .SH NAME
 bitcoin-cli \- manual page for bitcoin-cli
 
-This is a placefolder file. Please follow the instructions in \fIcontrib/devtools/README.md\fR to generate the manual pages after a release.
+This is a placeholder file. Please follow the instructions in \fIcontrib/devtools/README.md\fR to generate the manual pages after a release.
diff --git a/doc/man/bitcoin-qt.1 b/doc/man/bitcoin-qt.1
index 9c75e9fe54..ff4d1d2c7a 100644
--- a/doc/man/bitcoin-qt.1
+++ b/doc/man/bitcoin-qt.1
@@ -2,4 +2,4 @@
 .SH NAME
 bitcoin-qt \- manual page for bitcoin-qt
 
-This is a placefolder file. Please follow the instructions in \fIcontrib/devtools/README.md\fR to generate the manual pages after a release.
+This is a placeholder file. Please follow the instructions in \fIcontrib/devtools/README.md\fR to generate the manual pages after a release.
diff --git a/doc/man/bitcoin-tx.1 b/doc/man/bitcoin-tx.1
index 148a5890b0..776bb46234 100644
--- a/doc/man/bitcoin-tx.1
+++ b/doc/man/bitcoin-tx.1
@@ -2,4 +2,4 @@
 .SH NAME
 bitcoin-tx \- manual page for bitcoin-tx
 
-This is a placefolder file. Please follow the instructions in \fIcontrib/devtools/README.md\fR to generate the manual pages after a release.
+This is a placeholder file. Please follow the instructions in \fIcontrib/devtools/README.md\fR to generate the manual pages after a release.
diff --git a/doc/man/bitcoin-util.1 b/doc/man/bitcoin-util.1
new file mode 100644
index 0000000000..5c733c6e21
--- /dev/null
+++ b/doc/man/bitcoin-util.1
@@ -0,0 +1,5 @@
+.TH BITCOIN-UTIL "1"
+.SH NAME
+bitcoin-util \- manual page for bitcoin-util
+
+This is a placeholder file. Please follow the instructions in \fIcontrib/devtools/README.md\fR to generate the manual pages after a release.
diff --git a/doc/man/bitcoin-wallet.1 b/doc/man/bitcoin-wallet.1
index 69133b33f7..2da43dec66 100644
--- a/doc/man/bitcoin-wallet.1
+++ b/doc/man/bitcoin-wallet.1
@@ -2,4 +2,4 @@
 .SH NAME
 bitcoin-wallet \- manual page for bitcoin-wallet
 
-This is a placefolder file. Please follow the instructions in \fIcontrib/devtools/README.md\fR to generate the manual pages after a release.
+This is a placeholder file. Please follow the instructions in \fIcontrib/devtools/README.md\fR to generate the manual pages after a release.
diff --git a/doc/man/bitcoind.1 b/doc/man/bitcoind.1
index de338182ff..2c88f74520 100644
--- a/doc/man/bitcoind.1
+++ b/doc/man/bitcoind.1
@@ -2,4 +2,4 @@
 .SH NAME
 bitcoind \- manual page for bitcoind
 
-This is a placefolder file. Please follow the instructions in \fIcontrib/devtools/README.md\fR to generate the manual pages after a release.
+This is a placeholder file. Please follow the instructions in \fIcontrib/devtools/README.md\fR to generate the manual pages after a release.
diff --git a/src/Makefile.am b/src/Makefile.am
index ab355dee3f..2871df124c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -230,6 +230,7 @@ BITCOIN_CORE_H = \
   util/error.h \
   util/fees.h \
   util/golombrice.h \
+  util/hasher.h \
   util/macros.h \
   util/memory.h \
   util/message.h \
@@ -550,6 +551,7 @@ libbitcoin_util_a_SOURCES = \
   util/bytevectorhash.cpp \
   util/error.cpp \
   util/fees.cpp \
+  util/hasher.cpp \
   util/system.cpp \
   util/message.cpp \
   util/moneystr.cpp \
diff --git a/src/bitcoin-util.cpp b/src/bitcoin-util.cpp
index f7e670f4e0..b702a68bdf 100644
--- a/src/bitcoin-util.cpp
+++ b/src/bitcoin-util.cpp
@@ -40,6 +40,8 @@ static void SetupBitcoinUtilArgs(ArgsManager &argsman)
 {
     SetupHelpOptions(argsman);
 
+    argsman.AddArg("-version", "Print version and exit", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
+
     SetupChainParamsBaseOptions(argsman);
 }
 
@@ -62,12 +64,14 @@ static int AppInitUtil(int argc, char* argv[])
         return EXIT_FAILURE;
     }
 
-    if (argc < 2 || HelpRequested(gArgs)) {
+    if (argc < 2 || HelpRequested(gArgs) || gArgs.IsArgSet("-version")) {
         // First part of help message is specific to this utility
-        std::string strUsage = PACKAGE_NAME " bitcoin-util utility version " + FormatFullVersion() + "\n\n" +
-            "Usage:  bitcoin-util [options] [commands]  Do stuff\n" +
-            "\n";
-        strUsage += gArgs.GetHelpMessage();
+        std::string strUsage = PACKAGE_NAME " bitcoin-util utility version " + FormatFullVersion() + "\n";
+        if (!gArgs.IsArgSet("-version")) {
+            strUsage += "\n"
+                "Usage:  bitcoin-util [options] [commands]  Do stuff\n";
+            strUsage += "\n" + gArgs.GetHelpMessage();
+        }
 
         tfm::format(std::cout, "%s", strUsage);
 
diff --git a/src/coins.cpp b/src/coins.cpp
index 14f58e956c..dd84e720e7 100644
--- a/src/coins.cpp
+++ b/src/coins.cpp
@@ -31,8 +31,6 @@ bool CCoinsViewBacked::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock)
 CCoinsViewCursor *CCoinsViewBacked::Cursor() const { return base->Cursor(); }
 size_t CCoinsViewBacked::EstimateSize() const { return base->EstimateSize(); }
 
-SaltedOutpointHasher::SaltedOutpointHasher() : k0(GetRand(std::numeric_limits<uint64_t>::max())), k1(GetRand(std::numeric_limits<uint64_t>::max())) {}
-
 CCoinsViewCache::CCoinsViewCache(CCoinsView *baseIn) : CCoinsViewBacked(baseIn), cachedCoinsUsage(0) {}
 
 size_t CCoinsViewCache::DynamicMemoryUsage() const {
diff --git a/src/coins.h b/src/coins.h
index a3e241ac90..d2eb42d8cf 100644
--- a/src/coins.h
+++ b/src/coins.h
@@ -8,11 +8,11 @@
 
 #include <compressor.h>
 #include <core_memusage.h>
-#include <crypto/siphash.h>
 #include <memusage.h>
 #include <primitives/transaction.h>
 #include <serialize.h>
 #include <uint256.h>
+#include <util/hasher.h>
 
 #include <assert.h>
 #include <stdint.h>
@@ -82,33 +82,6 @@ public:
     }
 };
 
-class SaltedOutpointHasher
-{
-private:
-    /** Salt */
-    const uint64_t k0, k1;
-
-public:
-    SaltedOutpointHasher();
-
-    /**
-     * This *must* return size_t. With Boost 1.46 on 32-bit systems the
-     * unordered_map will behave unpredictably if the custom hasher returns a
-     * uint64_t, resulting in failures when syncing the chain (#4634).
-     *
-     * Having the hash noexcept allows libstdc++'s unordered_map to recalculate
-     * the hash during rehash, so it does not have to cache the value. This
-     * reduces node's memory by sizeof(size_t). The required recalculation has
-     * a slight performance penalty (around 1.6%), but this is compensated by
-     * memory savings of about 9% which allow for a larger dbcache setting.
-     *
-     * @see https://gcc.gnu.org/onlinedocs/gcc-9.2.0/libstdc++/manual/manual/unordered_associative.html
-     */
-    size_t operator()(const COutPoint& id) const noexcept {
-        return SipHashUint256Extra(k0, k1, id.hash, id.n);
-    }
-};
-
 /**
  * A Coin in one level of the coins database caching hierarchy.
  *
diff --git a/src/index/blockfilterindex.h b/src/index/blockfilterindex.h
index a9c8188bb6..221ac02c9e 100644
--- a/src/index/blockfilterindex.h
+++ b/src/index/blockfilterindex.h
@@ -9,15 +9,11 @@
 #include <chain.h>
 #include <flatfile.h>
 #include <index/base.h>
+#include <util/hasher.h>
 
 /** Interval between compact filter checkpoints. See BIP 157. */
 static constexpr int CFCHECKPT_INTERVAL = 1000;
 
-struct FilterHeaderHasher
-{
-    size_t operator()(const uint256& hash) const { return ReadLE64(hash.begin()); }
-};
-
 /**
  * BlockFilterIndex is used to store and retrieve block filters, hashes, and headers for a range of
  * blocks by height. An index is constructed for each supported filter type with its own database
diff --git a/src/init.cpp b/src/init.cpp
index 9a63fe0e03..09eb76eaee 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -1410,8 +1410,8 @@ bool AppInitMain(const util::Ref& context, NodeContext& node, interfaces::BlockA
     ChainstateManager& chainman = *Assert(node.chainman);
 
     assert(!node.peerman);
-    node.peerman = std::make_unique<PeerManager>(chainparams, *node.connman, node.banman.get(),
-                                                 *node.scheduler, chainman, *node.mempool, ignores_incoming_txs);
+    node.peerman = PeerManager::make(chainparams, *node.connman, node.banman.get(),
+                                     *node.scheduler, chainman, *node.mempool, ignores_incoming_txs);
     RegisterValidationInterface(node.peerman.get());
 
     // sanitize comments per BIP-0014, format user agent and check total size
diff --git a/src/net.h b/src/net.h
index 4f1a6b89a9..087135a290 100644
--- a/src/net.h
+++ b/src/net.h
@@ -760,11 +760,30 @@ private:
 class NetEventsInterface
 {
 public:
-    virtual bool ProcessMessages(CNode* pnode, std::atomic<bool>& interrupt) = 0;
-    virtual bool SendMessages(CNode* pnode) EXCLUSIVE_LOCKS_REQUIRED(pnode->cs_sendProcessing) = 0;
+    /** Initialize a peer (setup state, queue any initial messages) */
     virtual void InitializeNode(CNode* pnode) = 0;
+
+    /** Handle removal of a peer (clear state) */
     virtual void FinalizeNode(const CNode& node, bool& update_connection_time) = 0;
 
+    /**
+    * Process protocol messages received from a given node
+    *
+    * @param[in]   pnode           The node which we have received messages from.
+    * @param[in]   interrupt       Interrupt condition for processing threads
+    * @return                      True if there is more work to be done
+    */
+    virtual bool ProcessMessages(CNode* pnode, std::atomic<bool>& interrupt) = 0;
+
+    /**
+    * Send queued protocol messages to a given node.
+    *
+    * @param[in]   pnode           The node which we are sending messages to.
+    * @return                      True if there is more work to be done
+    */
+    virtual bool SendMessages(CNode* pnode) EXCLUSIVE_LOCKS_REQUIRED(pnode->cs_sendProcessing) = 0;
+
+
 protected:
     /**
      * Protected destructor so that instances can only be deleted by derived classes.
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 8f1cb952f2..cf73b1dae2 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -26,6 +26,7 @@
 #include <streams.h>
 #include <tinyformat.h>
 #include <txmempool.h>
+#include <txrequest.h>
 #include <util/check.h> // For NDEBUG compile time check
 #include <util/strencodings.h>
 #include <util/system.h>
@@ -168,6 +169,186 @@ void EraseOrphansFor(NodeId peer);
 
 // Internal stuff
 namespace {
+/**
+ * Data structure for an individual peer. This struct is not protected by
+ * cs_main since it does not contain validation-critical data.
+ *
+ * Memory is owned by shared pointers and this object is destructed when
+ * the refcount drops to zero.
+ *
+ * Mutexes inside this struct must not be held when locking m_peer_mutex.
+ *
+ * TODO: move most members from CNodeState to this structure.
+ * TODO: move remaining application-layer data members from CNode to this structure.
+ */
+struct Peer {
+    /** Same id as the CNode object for this peer */
+    const NodeId m_id{0};
+
+    /** Protects misbehavior data members */
+    Mutex m_misbehavior_mutex;
+    /** Accumulated misbehavior score for this peer */
+    int m_misbehavior_score GUARDED_BY(m_misbehavior_mutex){0};
+    /** Whether this peer should be disconnected and marked as discouraged (unless it has the noban permission). */
+    bool m_should_discourage GUARDED_BY(m_misbehavior_mutex){false};
+
+    /** Protects block inventory data members */
+    Mutex m_block_inv_mutex;
+    /** List of blocks that we'll announce via an `inv` message.
+     * There is no final sorting before sending, as they are always sent
+     * immediately and in the order requested. */
+    std::vector<uint256> m_blocks_for_inv_relay GUARDED_BY(m_block_inv_mutex);
+    /** Unfiltered list of blocks that we'd like to announce via a `headers`
+     * message. If we can't announce via a `headers` message, we'll fall back to
+     * announcing via `inv`. */
+    std::vector<uint256> m_blocks_for_headers_relay GUARDED_BY(m_block_inv_mutex);
+    /** The final block hash that we sent in an `inv` message to this peer.
+     * When the peer requests this block, we send an `inv` message to trigger
+     * the peer to request the next sequence of block hashes.
+     * Most peers use headers-first syncing, which doesn't use this mechanism */
+    uint256 m_continuation_block GUARDED_BY(m_block_inv_mutex) {};
+
+    /** This peer's reported block height when we connected */
+    std::atomic<int> m_starting_height{-1};
+
+    /** Set of txids to reconsider once their parent transactions have been accepted **/
+    std::set<uint256> m_orphan_work_set GUARDED_BY(g_cs_orphans);
+
+    /** Protects m_getdata_requests **/
+    Mutex m_getdata_requests_mutex;
+    /** Work queue of items requested by this peer **/
+    std::deque<CInv> m_getdata_requests GUARDED_BY(m_getdata_requests_mutex);
+
+    explicit Peer(NodeId id) : m_id(id) {}
+};
+
+using PeerRef = std::shared_ptr<Peer>;
+
+class PeerManagerImpl final : public PeerManager
+{
+public:
+    PeerManagerImpl(const CChainParams& chainparams, CConnman& connman, BanMan* banman,
+                    CScheduler& scheduler, ChainstateManager& chainman, CTxMemPool& pool,
+                    bool ignore_incoming_txs);
+
+    /** Overridden from CValidationInterface. */
+    void BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindexConnected) override;
+    void BlockDisconnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex* pindex) override;
+    void UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload) override;
+    void BlockChecked(const CBlock& block, const BlockValidationState& state) override;
+    void NewPoWValidBlock(const CBlockIndex *pindex, const std::shared_ptr<const CBlock>& pblock) override;
+
+    /** Implement NetEventsInterface */
+    void InitializeNode(CNode* pnode) override;
+    void FinalizeNode(const CNode& node, bool& fUpdateConnectionTime) override;
+    bool ProcessMessages(CNode* pfrom, std::atomic<bool>& interrupt) override;
+    bool SendMessages(CNode* pto) override EXCLUSIVE_LOCKS_REQUIRED(pto->cs_sendProcessing);
+
+    /** Implement PeerManager */
+    void CheckForStaleTipAndEvictPeers() override;
+    bool GetNodeStateStats(NodeId nodeid, CNodeStateStats& stats) override;
+    bool IgnoresIncomingTxs() override { return m_ignore_incoming_txs; }
+    void SetBestHeight(int height) override { m_best_height = height; };
+    void Misbehaving(const NodeId pnode, const int howmuch, const std::string& message) override;
+    void ProcessMessage(CNode& pfrom, const std::string& msg_type, CDataStream& vRecv,
+                        const std::chrono::microseconds time_received, const std::atomic<bool>& interruptMsgProc) override;
+
+private:
+    /** Consider evicting an outbound peer based on the amount of time they've been behind our tip */
+    void ConsiderEviction(CNode& pto, int64_t time_in_seconds) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
+    /** If we have extra outbound peers, try to disconnect the one with the oldest block announcement */
+    void EvictExtraOutboundPeers(int64_t time_in_seconds) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+
+    /** Retrieve unbroadcast transactions from the mempool and reattempt sending to peers */
+    void ReattemptInitialBroadcast(CScheduler& scheduler) const;
+
+    /** Get a shared pointer to the Peer object.
+     *  May return an empty shared_ptr if the Peer object can't be found. */
+    PeerRef GetPeerRef(NodeId id) const;
+
+    /** Get a shared pointer to the Peer object and remove it from m_peer_map.
+     *  May return an empty shared_ptr if the Peer object can't be found. */
+    PeerRef RemovePeer(NodeId id);
+
+    /**
+     * Potentially mark a node discouraged based on the contents of a BlockValidationState object
+     *
+     * @param[in] via_compact_block this bool is passed in because net_processing should
+     * punish peers differently depending on whether the data was provided in a compact
+     * block message or not. If the compact block had a valid header, but contained invalid
+     * txs, the peer should not be punished. See BIP 152.
+     *
+     * @return Returns true if the peer was punished (probably disconnected)
+     */
+    bool MaybePunishNodeForBlock(NodeId nodeid, const BlockValidationState& state,
+                                 bool via_compact_block, const std::string& message = "");
+
+    /**
+     * Potentially disconnect and discourage a node based on the contents of a TxValidationState object
+     *
+     * @return Returns true if the peer was punished (probably disconnected)
+     */
+    bool MaybePunishNodeForTx(NodeId nodeid, const TxValidationState& state, const std::string& message = "");
+
+    /** Maybe disconnect a peer and discourage future connections from its address.
+     *
+     * @param[in]   pnode     The node to check.
+     * @return                True if the peer was marked for disconnection in this function
+     */
+    bool MaybeDiscourageAndDisconnect(CNode& pnode);
+
+    void ProcessOrphanTx(std::set<uint256>& orphan_work_set) EXCLUSIVE_LOCKS_REQUIRED(cs_main, g_cs_orphans);
+    /** Process a single headers message from a peer. */
+    void ProcessHeadersMessage(CNode& pfrom, const Peer& peer,
+                               const std::vector<CBlockHeader>& headers,
+                               bool via_compact_block);
+
+    void SendBlockTransactions(CNode& pfrom, const CBlock& block, const BlockTransactionsRequest& req);
+
+    /** Register with TxRequestTracker that an INV has been received from a
+     *  peer. The announcement parameters are decided in PeerManager and then
+     *  passed to TxRequestTracker. */
+    void AddTxAnnouncement(const CNode& node, const GenTxid& gtxid, std::chrono::microseconds current_time)
+        EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
+
+    /** Send a version message to a peer */
+    void PushNodeVersion(CNode& pnode, int64_t nTime);
+
+    const CChainParams& m_chainparams;
+    CConnman& m_connman;
+    /** Pointer to this node's banman. May be nullptr - check existence before dereferencing. */
+    BanMan* const m_banman;
+    ChainstateManager& m_chainman;
+    CTxMemPool& m_mempool;
+    TxRequestTracker m_txrequest GUARDED_BY(::cs_main);
+
+    /** The height of the best chain */
+    std::atomic<int> m_best_height{-1};
+
+    int64_t m_stale_tip_check_time; //!< Next time to check for stale tip
+
+    /** Whether this node is running in blocks only mode */
+    const bool m_ignore_incoming_txs;
+
+    /** Whether we've completed initial sync yet, for determining when to turn
+      * on extra block-relay-only peers. */
+    bool m_initial_sync_finished{false};
+
+    /** Protects m_peer_map. This mutex must not be locked while holding a lock
+     *  on any of the mutexes inside a Peer object. */
+    mutable Mutex m_peer_mutex;
+    /**
+     * Map of all Peer objects, keyed by peer id. This map is protected
+     * by the m_peer_mutex. Once a shared pointer reference is
+     * taken, the lock may be released. Individual fields are protected by
+     * their own locks.
+     */
+    std::map<NodeId, PeerRef> m_peer_map GUARDED_BY(m_peer_mutex);
+};
+} // namespace
+
+namespace {
     /** Number of nodes with fSyncStarted. */
     int nSyncStarted GUARDED_BY(cs_main) = 0;
 
@@ -683,7 +864,7 @@ static void FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vec
 
 } // namespace
 
-void PeerManager::PushNodeVersion(CNode& pnode, int64_t nTime)
+void PeerManagerImpl::PushNodeVersion(CNode& pnode, int64_t nTime)
 {
     // Note that pnode->GetLocalServices() is a reflection of the local
     // services we were offering when the CNode object was created for this
@@ -709,7 +890,7 @@ void PeerManager::PushNodeVersion(CNode& pnode, int64_t nTime)
     }
 }
 
-void PeerManager::AddTxAnnouncement(const CNode& node, const GenTxid& gtxid, std::chrono::microseconds current_time)
+void PeerManagerImpl::AddTxAnnouncement(const CNode& node, const GenTxid& gtxid, std::chrono::microseconds current_time)
 {
     AssertLockHeld(::cs_main); // For m_txrequest
     NodeId nodeid = node.GetId();
@@ -745,7 +926,8 @@ void UpdateLastBlockAnnounceTime(NodeId node, int64_t time_in_seconds)
     if (state) state->m_last_block_announcement = time_in_seconds;
 }
 
-void PeerManager::InitializeNode(CNode *pnode) {
+void PeerManagerImpl::InitializeNode(CNode *pnode)
+{
     CAddress addr = pnode->addr;
     std::string addrName = pnode->GetAddrName();
     NodeId nodeid = pnode->GetId();
@@ -764,7 +946,7 @@ void PeerManager::InitializeNode(CNode *pnode) {
     }
 }
 
-void PeerManager::ReattemptInitialBroadcast(CScheduler& scheduler) const
+void PeerManagerImpl::ReattemptInitialBroadcast(CScheduler& scheduler) const
 {
     std::set<uint256> unbroadcast_txids = m_mempool.GetUnbroadcastTxs();
 
@@ -785,7 +967,8 @@ void PeerManager::ReattemptInitialBroadcast(CScheduler& scheduler) const
     scheduler.scheduleFromNow([&] { ReattemptInitialBroadcast(scheduler); }, delta);
 }
 
-void PeerManager::FinalizeNode(const CNode& node, bool& fUpdateConnectionTime) {
+void PeerManagerImpl::FinalizeNode(const CNode& node, bool& fUpdateConnectionTime)
+{
     NodeId nodeid = node.GetId();
     fUpdateConnectionTime = false;
     LOCK(cs_main);
@@ -839,14 +1022,14 @@ void PeerManager::FinalizeNode(const CNode& node, bool& fUpdateConnectionTime) {
     LogPrint(BCLog::NET, "Cleared nodestate for peer=%d\n", nodeid);
 }
 
-PeerRef PeerManager::GetPeerRef(NodeId id) const
+PeerRef PeerManagerImpl::GetPeerRef(NodeId id) const
 {
     LOCK(m_peer_mutex);
     auto it = m_peer_map.find(id);
     return it != m_peer_map.end() ? it->second : nullptr;
 }
 
-PeerRef PeerManager::RemovePeer(NodeId id)
+PeerRef PeerManagerImpl::RemovePeer(NodeId id)
 {
     PeerRef ret;
     LOCK(m_peer_mutex);
@@ -858,7 +1041,8 @@ PeerRef PeerManager::RemovePeer(NodeId id)
     return ret;
 }
 
-bool PeerManager::GetNodeStateStats(NodeId nodeid, CNodeStateStats &stats) {
+bool PeerManagerImpl::GetNodeStateStats(NodeId nodeid, CNodeStateStats &stats)
+{
     {
         LOCK(cs_main);
         CNodeState* state = State(nodeid);
@@ -1015,7 +1199,7 @@ unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
     return nEvicted;
 }
 
-void PeerManager::Misbehaving(const NodeId pnode, const int howmuch, const std::string& message)
+void PeerManagerImpl::Misbehaving(const NodeId pnode, const int howmuch, const std::string& message)
 {
     assert(howmuch > 0);
 
@@ -1033,8 +1217,8 @@ void PeerManager::Misbehaving(const NodeId pnode, const int howmuch, const std::
     }
 }
 
-bool PeerManager::MaybePunishNodeForBlock(NodeId nodeid, const BlockValidationState& state,
-                                          bool via_compact_block, const std::string& message)
+bool PeerManagerImpl::MaybePunishNodeForBlock(NodeId nodeid, const BlockValidationState& state,
+                                              bool via_compact_block, const std::string& message)
 {
     switch (state.GetResult()) {
     case BlockValidationResult::BLOCK_RESULT_UNSET:
@@ -1083,7 +1267,7 @@ bool PeerManager::MaybePunishNodeForBlock(NodeId nodeid, const BlockValidationSt
     return false;
 }
 
-bool PeerManager::MaybePunishNodeForTx(NodeId nodeid, const TxValidationState& state, const std::string& message)
+bool PeerManagerImpl::MaybePunishNodeForTx(NodeId nodeid, const TxValidationState& state, const std::string& message)
 {
     switch (state.GetResult()) {
     case TxValidationResult::TX_RESULT_UNSET:
@@ -1129,9 +1313,16 @@ static bool BlockRequestAllowed(const CBlockIndex* pindex, const Consensus::Para
         (GetBlockProofEquivalentTime(*pindexBestHeader, *pindex, *pindexBestHeader, consensusParams) < STALE_RELAY_AGE_LIMIT);
 }
 
-PeerManager::PeerManager(const CChainParams& chainparams, CConnman& connman, BanMan* banman,
-                         CScheduler& scheduler, ChainstateManager& chainman, CTxMemPool& pool,
-                         bool ignore_incoming_txs)
+std::unique_ptr<PeerManager> PeerManager::make(const CChainParams& chainparams, CConnman& connman, BanMan* banman,
+                                               CScheduler& scheduler, ChainstateManager& chainman, CTxMemPool& pool,
+                                               bool ignore_incoming_txs)
+{
+    return std::make_unique<PeerManagerImpl>(chainparams, connman, banman, scheduler, chainman, pool, ignore_incoming_txs);
+}
+
+PeerManagerImpl::PeerManagerImpl(const CChainParams& chainparams, CConnman& connman, BanMan* banman,
+                                 CScheduler& scheduler, ChainstateManager& chainman, CTxMemPool& pool,
+                                 bool ignore_incoming_txs)
     : m_chainparams(chainparams),
       m_connman(connman),
       m_banman(banman),
@@ -1171,7 +1362,7 @@ PeerManager::PeerManager(const CChainParams& chainparams, CConnman& connman, Ban
  * block, remember the recently confirmed transactions, and delete tracked
  * announcements for them. Also save the time of the last tip update.
  */
-void PeerManager::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindex)
+void PeerManagerImpl::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindex)
 {
     {
         LOCK(g_cs_orphans);
@@ -1222,7 +1413,7 @@ void PeerManager::BlockConnected(const std::shared_ptr<const CBlock>& pblock, co
     }
 }
 
-void PeerManager::BlockDisconnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex* pindex)
+void PeerManagerImpl::BlockDisconnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex* pindex)
 {
     // To avoid relay problems with transactions that were previously
     // confirmed, clear our filter of recently confirmed transactions whenever
@@ -1247,7 +1438,8 @@ static bool fWitnessesPresentInMostRecentCompactBlock GUARDED_BY(cs_most_recent_
  * Maintain state about the best-seen block and fast-announce a compact block
  * to compatible peers.
  */
-void PeerManager::NewPoWValidBlock(const CBlockIndex *pindex, const std::shared_ptr<const CBlock>& pblock) {
+void PeerManagerImpl::NewPoWValidBlock(const CBlockIndex *pindex, const std::shared_ptr<const CBlock>& pblock)
+{
     std::shared_ptr<const CBlockHeaderAndShortTxIDs> pcmpctblock = std::make_shared<const CBlockHeaderAndShortTxIDs> (*pblock, true);
     const CNetMsgMaker msgMaker(PROTOCOL_VERSION);
 
@@ -1294,9 +1486,9 @@ void PeerManager::NewPoWValidBlock(const CBlockIndex *pindex, const std::shared_
  * Update our best height and announce any block hashes which weren't previously
  * in ::ChainActive() to our peers.
  */
-void PeerManager::UpdatedBlockTip(const CBlockIndex* pindexNew, const CBlockIndex* pindexFork, bool fInitialDownload)
+void PeerManagerImpl::UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload)
 {
-    m_best_height = pindexNew->nHeight;
+    SetBestHeight(pindexNew->nHeight);
     SetServiceFlagsIBDCache(!fInitialDownload);
 
     // Don't relay inventory during initial block download.
@@ -1333,7 +1525,8 @@ void PeerManager::UpdatedBlockTip(const CBlockIndex* pindexNew, const CBlockInde
  * Handle invalid block rejection and consequent peer discouragement, maintain which
  * peers announce compact blocks.
  */
-void PeerManager::BlockChecked(const CBlock& block, const BlockValidationState& state) {
+void PeerManagerImpl::BlockChecked(const CBlock& block, const BlockValidationState& state)
+{
     LOCK(cs_main);
 
     const uint256 hash(block.GetHash());
@@ -1761,7 +1954,8 @@ static uint32_t GetFetchFlags(const CNode& pfrom) EXCLUSIVE_LOCKS_REQUIRED(cs_ma
     return nFetchFlags;
 }
 
-void PeerManager::SendBlockTransactions(CNode& pfrom, const CBlock& block, const BlockTransactionsRequest& req) {
+void PeerManagerImpl::SendBlockTransactions(CNode& pfrom, const CBlock& block, const BlockTransactionsRequest& req)
+{
     BlockTransactions resp(req);
     for (size_t i = 0; i < req.indexes.size(); i++) {
         if (req.indexes[i] >= block.vtx.size()) {
@@ -1776,9 +1970,9 @@ void PeerManager::SendBlockTransactions(CNode& pfrom, const CBlock& block, const
     m_connman.PushMessage(&pfrom, msgMaker.Make(nSendFlags, NetMsgType::BLOCKTXN, resp));
 }
 
-void PeerManager::ProcessHeadersMessage(CNode& pfrom, const Peer& peer,
-                                        const std::vector<CBlockHeader>& headers,
-                                        bool via_compact_block)
+void PeerManagerImpl::ProcessHeadersMessage(CNode& pfrom, const Peer& peer,
+                                            const std::vector<CBlockHeader>& headers,
+                                            bool via_compact_block)
 {
     const CNetMsgMaker msgMaker(pfrom.GetCommonVersion());
     size_t nCount = headers.size();
@@ -1970,7 +2164,7 @@ void PeerManager::ProcessHeadersMessage(CNode& pfrom, const Peer& peer,
  *                                  may be added to if accepting an orphan causes its children to be
  *                                  reconsidered.
  */
-void PeerManager::ProcessOrphanTx(std::set<uint256>& orphan_work_set)
+void PeerManagerImpl::ProcessOrphanTx(std::set<uint256>& orphan_work_set)
 {
     AssertLockHeld(cs_main);
     AssertLockHeld(g_cs_orphans);
@@ -2267,9 +2461,9 @@ static void ProcessGetCFCheckPt(CNode& peer, CDataStream& vRecv, const CChainPar
     connman.PushMessage(&peer, std::move(msg));
 }
 
-void PeerManager::ProcessMessage(CNode& pfrom, const std::string& msg_type, CDataStream& vRecv,
-                                         const std::chrono::microseconds time_received,
-                                         const std::atomic<bool>& interruptMsgProc)
+void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type, CDataStream& vRecv,
+                                     const std::chrono::microseconds time_received,
+                                     const std::atomic<bool>& interruptMsgProc)
 {
     LogPrint(BCLog::NET, "received: %s (%u bytes) peer=%d\n", SanitizeString(msg_type), vRecv.size(), pfrom.GetId());
 
@@ -3755,7 +3949,7 @@ void PeerManager::ProcessMessage(CNode& pfrom, const std::string& msg_type, CDat
     return;
 }
 
-bool PeerManager::MaybeDiscourageAndDisconnect(CNode& pnode)
+bool PeerManagerImpl::MaybeDiscourageAndDisconnect(CNode& pnode)
 {
     const NodeId peer_id{pnode.GetId()};
     PeerRef peer = GetPeerRef(peer_id);
@@ -3797,7 +3991,7 @@ bool PeerManager::MaybeDiscourageAndDisconnect(CNode& pnode)
     return true;
 }
 
-bool PeerManager::ProcessMessages(CNode* pfrom, std::atomic<bool>& interruptMsgProc)
+bool PeerManagerImpl::ProcessMessages(CNode* pfrom, std::atomic<bool>& interruptMsgProc)
 {
     bool fMoreWork = false;
 
@@ -3872,7 +4066,7 @@ bool PeerManager::ProcessMessages(CNode* pfrom, std::atomic<bool>& interruptMsgP
     return fMoreWork;
 }
 
-void PeerManager::ConsiderEviction(CNode& pto, int64_t time_in_seconds)
+void PeerManagerImpl::ConsiderEviction(CNode& pto, int64_t time_in_seconds)
 {
     AssertLockHeld(cs_main);
 
@@ -3925,7 +4119,7 @@ void PeerManager::ConsiderEviction(CNode& pto, int64_t time_in_seconds)
     }
 }
 
-void PeerManager::EvictExtraOutboundPeers(int64_t time_in_seconds)
+void PeerManagerImpl::EvictExtraOutboundPeers(int64_t time_in_seconds)
 {
     // If we have any extra block-relay-only peers, disconnect the youngest unless
     // it's given us a block -- in which case, compare with the second-youngest, and
@@ -4026,7 +4220,7 @@ void PeerManager::EvictExtraOutboundPeers(int64_t time_in_seconds)
     }
 }
 
-void PeerManager::CheckForStaleTipAndEvictPeers()
+void PeerManagerImpl::CheckForStaleTipAndEvictPeers()
 {
     LOCK(cs_main);
 
@@ -4073,7 +4267,7 @@ public:
 };
 }
 
-bool PeerManager::SendMessages(CNode* pto)
+bool PeerManagerImpl::SendMessages(CNode* pto)
 {
     PeerRef peer = GetPeerRef(pto->GetId());
     const Consensus::Params& consensusParams = m_chainparams.GetConsensus();
diff --git a/src/net_processing.h b/src/net_processing.h
index 322fabbe11..eaa3b142a8 100644
--- a/src/net_processing.h
+++ b/src/net_processing.h
@@ -6,19 +6,13 @@
 #ifndef BITCOIN_NET_PROCESSING_H
 #define BITCOIN_NET_PROCESSING_H
 
-#include <consensus/params.h>
 #include <net.h>
 #include <sync.h>
-#include <txrequest.h>
 #include <validationinterface.h>
 
-class BlockTransactionsRequest;
-class BlockValidationState;
-class CBlockHeader;
 class CChainParams;
 class CTxMemPool;
 class ChainstateManager;
-class TxValidationState;
 
 extern RecursiveMutex cs_main;
 extern RecursiveMutex g_cs_orphans;
@@ -39,216 +33,39 @@ struct CNodeStateStats {
     std::vector<int> vHeightInFlight;
 };
 
-/**
- * Data structure for an individual peer. This struct is not protected by
- * cs_main since it does not contain validation-critical data.
- *
- * Memory is owned by shared pointers and this object is destructed when
- * the refcount drops to zero.
- *
- * Mutexes inside this struct must not be held when locking m_peer_mutex.
- *
- * TODO: move most members from CNodeState to this structure.
- * TODO: move remaining application-layer data members from CNode to this structure.
- */
-struct Peer {
-    /** Same id as the CNode object for this peer */
-    const NodeId m_id{0};
-
-    /** Protects misbehavior data members */
-    Mutex m_misbehavior_mutex;
-    /** Accumulated misbehavior score for this peer */
-    int m_misbehavior_score GUARDED_BY(m_misbehavior_mutex){0};
-    /** Whether this peer should be disconnected and marked as discouraged (unless it has the noban permission). */
-    bool m_should_discourage GUARDED_BY(m_misbehavior_mutex){false};
-
-    /** Protects block inventory data members */
-    Mutex m_block_inv_mutex;
-    /** List of blocks that we'll announce via an `inv` message.
-     * There is no final sorting before sending, as they are always sent
-     * immediately and in the order requested. */
-    std::vector<uint256> m_blocks_for_inv_relay GUARDED_BY(m_block_inv_mutex);
-    /** Unfiltered list of blocks that we'd like to announce via a `headers`
-     * message. If we can't announce via a `headers` message, we'll fall back to
-     * announcing via `inv`. */
-    std::vector<uint256> m_blocks_for_headers_relay GUARDED_BY(m_block_inv_mutex);
-    /** The final block hash that we sent in an `inv` message to this peer.
-     * When the peer requests this block, we send an `inv` message to trigger
-     * the peer to request the next sequence of block hashes.
-     * Most peers use headers-first syncing, which doesn't use this mechanism */
-    uint256 m_continuation_block GUARDED_BY(m_block_inv_mutex) {};
-
-    /** This peer's reported block height when we connected */
-    std::atomic<int> m_starting_height{-1};
-
-    /** Set of txids to reconsider once their parent transactions have been accepted **/
-    std::set<uint256> m_orphan_work_set GUARDED_BY(g_cs_orphans);
-
-    /** Protects m_getdata_requests **/
-    Mutex m_getdata_requests_mutex;
-    /** Work queue of items requested by this peer **/
-    std::deque<CInv> m_getdata_requests GUARDED_BY(m_getdata_requests_mutex);
-
-    explicit Peer(NodeId id) : m_id(id) {}
-};
-
-using PeerRef = std::shared_ptr<Peer>;
-
-class PeerManager final : public CValidationInterface, public NetEventsInterface {
+class PeerManager : public CValidationInterface, public NetEventsInterface
+{
 public:
-    PeerManager(const CChainParams& chainparams, CConnman& connman, BanMan* banman,
-                CScheduler& scheduler, ChainstateManager& chainman, CTxMemPool& pool,
-                bool ignore_incoming_txs);
+    static std::unique_ptr<PeerManager> make(const CChainParams& chainparams, CConnman& connman, BanMan* banman,
+                                             CScheduler& scheduler, ChainstateManager& chainman, CTxMemPool& pool,
+                                             bool ignore_incoming_txs);
+    virtual ~PeerManager() { }
 
-    /**
-     * Overridden from CValidationInterface.
-     */
-    void BlockConnected(const std::shared_ptr<const CBlock>& pblock, const CBlockIndex* pindexConnected) override;
-    void BlockDisconnected(const std::shared_ptr<const CBlock> &block, const CBlockIndex* pindex) override;
-    /**
-     * Overridden from CValidationInterface.
-     */
-    void UpdatedBlockTip(const CBlockIndex *pindexNew, const CBlockIndex *pindexFork, bool fInitialDownload) override;
-    /**
-     * Overridden from CValidationInterface.
-     */
-    void BlockChecked(const CBlock& block, const BlockValidationState& state) override;
-    /**
-     * Overridden from CValidationInterface.
-     */
-    void NewPoWValidBlock(const CBlockIndex *pindex, const std::shared_ptr<const CBlock>& pblock) override;
-
-    /** Initialize a peer by adding it to mapNodeState and pushing a message requesting its version */
-    void InitializeNode(CNode* pnode) override;
-    /** Handle removal of a peer by updating various state and removing it from mapNodeState */
-    void FinalizeNode(const CNode& node, bool& fUpdateConnectionTime) override;
-    /**
-    * Process protocol messages received from a given node
-    *
-    * @param[in]   pfrom           The node which we have received messages from.
-    * @param[in]   interrupt       Interrupt condition for processing threads
-    */
-    bool ProcessMessages(CNode* pfrom, std::atomic<bool>& interrupt) override;
-    /**
-    * Send queued protocol messages to be sent to a give node.
-    *
-    * @param[in]   pto             The node which we are sending messages to.
-    * @return                      True if there is more work to be done
-    */
-    bool SendMessages(CNode* pto) override EXCLUSIVE_LOCKS_REQUIRED(pto->cs_sendProcessing);
+    /** Get statistics from node state */
+    virtual bool GetNodeStateStats(NodeId nodeid, CNodeStateStats& stats) = 0;
 
-    /** Consider evicting an outbound peer based on the amount of time they've been behind our tip */
-    void ConsiderEviction(CNode& pto, int64_t time_in_seconds) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
-    /** Evict extra outbound peers. If we think our tip may be stale, connect to an extra outbound */
-    void CheckForStaleTipAndEvictPeers();
-    /** If we have extra outbound peers, try to disconnect the one with the oldest block announcement */
-    void EvictExtraOutboundPeers(int64_t time_in_seconds) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
-    /** Retrieve unbroadcast transactions from the mempool and reattempt sending to peers */
-    void ReattemptInitialBroadcast(CScheduler& scheduler) const;
+    /** Whether this node ignores txs received over p2p. */
+    virtual bool IgnoresIncomingTxs() = 0;
 
-    /** Process a single message from a peer. Public for fuzz testing */
-    void ProcessMessage(CNode& pfrom, const std::string& msg_type, CDataStream& vRecv,
-                        const std::chrono::microseconds time_received, const std::atomic<bool>& interruptMsgProc);
+    /** Set the best height */
+    virtual void SetBestHeight(int height) = 0;
 
     /**
      * Increment peer's misbehavior score. If the new value >= DISCOURAGEMENT_THRESHOLD, mark the node
      * to be discouraged, meaning the peer might be disconnected and added to the discouragement filter.
      * Public for unit testing.
      */
-    void Misbehaving(const NodeId pnode, const int howmuch, const std::string& message);
-
-    /** Get statistics from node state */
-    bool GetNodeStateStats(NodeId nodeid, CNodeStateStats& stats);
-
-    /** Set the best height */
-    void SetBestHeight(int height) { m_best_height = height; };
-
-    /** Whether this node ignores txs received over p2p. */
-    bool IgnoresIncomingTxs() { return m_ignore_incoming_txs; };
-
-private:
-    /** Get a shared pointer to the Peer object.
-     *  May return an empty shared_ptr if the Peer object can't be found. */
-    PeerRef GetPeerRef(NodeId id) const;
-
-    /** Get a shared pointer to the Peer object and remove it from m_peer_map.
-     *  May return an empty shared_ptr if the Peer object can't be found. */
-    PeerRef RemovePeer(NodeId id);
-
-    /**
-     * Potentially mark a node discouraged based on the contents of a BlockValidationState object
-     *
-     * @param[in] via_compact_block this bool is passed in because net_processing should
-     * punish peers differently depending on whether the data was provided in a compact
-     * block message or not. If the compact block had a valid header, but contained invalid
-     * txs, the peer should not be punished. See BIP 152.
-     *
-     * @return Returns true if the peer was punished (probably disconnected)
-     */
-    bool MaybePunishNodeForBlock(NodeId nodeid, const BlockValidationState& state,
-                                 bool via_compact_block, const std::string& message = "");
+    virtual void Misbehaving(const NodeId pnode, const int howmuch, const std::string& message) = 0;
 
     /**
-     * Potentially disconnect and discourage a node based on the contents of a TxValidationState object
-     *
-     * @return Returns true if the peer was punished (probably disconnected)
-     */
-    bool MaybePunishNodeForTx(NodeId nodeid, const TxValidationState& state, const std::string& message = "");
-
-    /** Maybe disconnect a peer and discourage future connections from its address.
-     *
-     * @param[in]   pnode     The node to check.
-     * @return                True if the peer was marked for disconnection in this function
+     * Evict extra outbound peers. If we think our tip may be stale, connect to an extra outbound.
+     * Public for unit testing.
      */
-    bool MaybeDiscourageAndDisconnect(CNode& pnode);
+    virtual void CheckForStaleTipAndEvictPeers() = 0;
 
-    void ProcessOrphanTx(std::set<uint256>& orphan_work_set) EXCLUSIVE_LOCKS_REQUIRED(cs_main, g_cs_orphans);
-    /** Process a single headers message from a peer. */
-    void ProcessHeadersMessage(CNode& pfrom, const Peer& peer,
-                               const std::vector<CBlockHeader>& headers,
-                               bool via_compact_block);
-
-    void SendBlockTransactions(CNode& pfrom, const CBlock& block, const BlockTransactionsRequest& req);
-
-    /** Register with TxRequestTracker that an INV has been received from a
-     *  peer. The announcement parameters are decided in PeerManager and then
-     *  passed to TxRequestTracker. */
-    void AddTxAnnouncement(const CNode& node, const GenTxid& gtxid, std::chrono::microseconds current_time)
-        EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
-
-    /** Send a version message to a peer */
-    void PushNodeVersion(CNode& pnode, int64_t nTime);
-
-    const CChainParams& m_chainparams;
-    CConnman& m_connman;
-    /** Pointer to this node's banman. May be nullptr - check existence before dereferencing. */
-    BanMan* const m_banman;
-    ChainstateManager& m_chainman;
-    CTxMemPool& m_mempool;
-    TxRequestTracker m_txrequest GUARDED_BY(::cs_main);
-
-    /** The height of the best chain */
-    std::atomic<int> m_best_height{-1};
-
-    int64_t m_stale_tip_check_time; //!< Next time to check for stale tip
-
-    /** Whether this node is running in blocks only mode */
-    const bool m_ignore_incoming_txs;
-
-    /** Whether we've completed initial sync yet, for determining when to turn
-      * on extra block-relay-only peers. */
-    bool m_initial_sync_finished{false};
-
-    /** Protects m_peer_map. This mutex must not be locked while holding a lock
-     *  on any of the mutexes inside a Peer object. */
-    mutable Mutex m_peer_mutex;
-    /**
-     * Map of all Peer objects, keyed by peer id. This map is protected
-     * by the m_peer_mutex. Once a shared pointer reference is
-     * taken, the lock may be released. Individual fields are protected by
-     * their own locks.
-     */
-    std::map<NodeId, PeerRef> m_peer_map GUARDED_BY(m_peer_mutex);
+    /** Process a single message from a peer. Public for fuzz testing */
+    virtual void ProcessMessage(CNode& pfrom, const std::string& msg_type, CDataStream& vRecv,
+                                const std::chrono::microseconds time_received, const std::atomic<bool>& interruptMsgProc) = 0;
 };
 
 /** Relay transaction to every node */
diff --git a/src/script/sigcache.h b/src/script/sigcache.h
index 512f61f2bf..bf0ba38c2d 100644
--- a/src/script/sigcache.h
+++ b/src/script/sigcache.h
@@ -8,6 +8,7 @@
 
 #include <script/interpreter.h>
 #include <span.h>
+#include <util/hasher.h>
 
 #include <vector>
 
@@ -20,27 +21,6 @@ static const int64_t MAX_MAX_SIG_CACHE_SIZE = 16384;
 
 class CPubKey;
 
-/**
- * We're hashing a nonce into the entries themselves, so we don't need extra
- * blinding in the set hash computation.
- *
- * This may exhibit platform endian dependent behavior but because these are
- * nonced hashes (random) and this state is only ever used locally it is safe.
- * All that matters is local consistency.
- */
-class SignatureCacheHasher
-{
-public:
-    template <uint8_t hash_select>
-    uint32_t operator()(const uint256& key) const
-    {
-        static_assert(hash_select <8, "SignatureCacheHasher only has 8 hashes available.");
-        uint32_t u;
-        std::memcpy(&u, key.begin()+4*hash_select, 4);
-        return u;
-    }
-};
-
 class CachingTransactionSignatureChecker : public TransactionSignatureChecker
 {
 private:
diff --git a/src/test/denialofservice_tests.cpp b/src/test/denialofservice_tests.cpp
index d926f8d767..cf6009d591 100644
--- a/src/test/denialofservice_tests.cpp
+++ b/src/test/denialofservice_tests.cpp
@@ -80,8 +80,8 @@ BOOST_AUTO_TEST_CASE(outbound_slow_chain_eviction)
 {
     const CChainParams& chainparams = Params();
     auto connman = MakeUnique<CConnman>(0x1337, 0x1337);
-    auto peerLogic = std::make_unique<PeerManager>(chainparams, *connman, nullptr, *m_node.scheduler,
-                                                   *m_node.chainman, *m_node.mempool, false);
+    auto peerLogic = PeerManager::make(chainparams, *connman, nullptr, *m_node.scheduler,
+                                       *m_node.chainman, *m_node.mempool, false);
 
     // Mock an outbound peer
     CAddress addr1(ip(0xa0b0c001), NODE_NONE);
@@ -150,8 +150,8 @@ BOOST_AUTO_TEST_CASE(stale_tip_peer_management)
 {
     const CChainParams& chainparams = Params();
     auto connman = MakeUnique<CConnmanTest>(0x1337, 0x1337);
-    auto peerLogic = std::make_unique<PeerManager>(chainparams, *connman, nullptr, *m_node.scheduler,
-                                                   *m_node.chainman, *m_node.mempool, false);
+    auto peerLogic = PeerManager::make(chainparams, *connman, nullptr, *m_node.scheduler,
+                                       *m_node.chainman, *m_node.mempool, false);
 
     constexpr int max_outbound_full_relay = MAX_OUTBOUND_FULL_RELAY_CONNECTIONS;
     CConnman::Options options;
@@ -224,8 +224,8 @@ BOOST_AUTO_TEST_CASE(peer_discouragement)
     const CChainParams& chainparams = Params();
     auto banman = MakeUnique<BanMan>(GetDataDir() / "banlist.dat", nullptr, DEFAULT_MISBEHAVING_BANTIME);
     auto connman = MakeUnique<CConnman>(0x1337, 0x1337);
-    auto peerLogic = std::make_unique<PeerManager>(chainparams, *connman, banman.get(), *m_node.scheduler,
-                                                   *m_node.chainman, *m_node.mempool, false);
+    auto peerLogic = PeerManager::make(chainparams, *connman, banman.get(), *m_node.scheduler,
+                                       *m_node.chainman, *m_node.mempool, false);
 
     banman->ClearBanned();
     CAddress addr1(ip(0xa0b0c001), NODE_NONE);
@@ -271,8 +271,8 @@ BOOST_AUTO_TEST_CASE(DoS_bantime)
     const CChainParams& chainparams = Params();
     auto banman = MakeUnique<BanMan>(GetDataDir() / "banlist.dat", nullptr, DEFAULT_MISBEHAVING_BANTIME);
     auto connman = MakeUnique<CConnman>(0x1337, 0x1337);
-    auto peerLogic = std::make_unique<PeerManager>(chainparams, *connman, banman.get(), *m_node.scheduler,
-                                                   *m_node.chainman, *m_node.mempool, false);
+    auto peerLogic = PeerManager::make(chainparams, *connman, banman.get(), *m_node.scheduler,
+                                       *m_node.chainman, *m_node.mempool, false);
 
     banman->ClearBanned();
     int64_t nStartTime = GetTime();
diff --git a/src/test/util/setup_common.cpp b/src/test/util/setup_common.cpp
index e167fc98fd..738f414cd0 100644
--- a/src/test/util/setup_common.cpp
+++ b/src/test/util/setup_common.cpp
@@ -192,9 +192,9 @@ TestingSetup::TestingSetup(const std::string& chainName, const std::vector<const
 
     m_node.banman = MakeUnique<BanMan>(GetDataDir() / "banlist.dat", nullptr, DEFAULT_MISBEHAVING_BANTIME);
     m_node.connman = MakeUnique<CConnman>(0x1337, 0x1337); // Deterministic randomness for tests.
-    m_node.peerman = std::make_unique<PeerManager>(chainparams, *m_node.connman, m_node.banman.get(),
-                                                   *m_node.scheduler, *m_node.chainman, *m_node.mempool,
-                                                   false);
+    m_node.peerman = PeerManager::make(chainparams, *m_node.connman, m_node.banman.get(),
+                                       *m_node.scheduler, *m_node.chainman, *m_node.mempool,
+                                       false);
     {
         CConnman::Options options;
         options.m_msgproc = m_node.peerman.get();
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index d18182c07d..9ae7b921b3 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -1127,5 +1127,3 @@ CTxMemPool::EpochGuard::~EpochGuard()
     ++pool.m_epoch;
     pool.m_has_epoch_guard = false;
 }
-
-SaltedTxidHasher::SaltedTxidHasher() : k0(GetRand(std::numeric_limits<uint64_t>::max())), k1(GetRand(std::numeric_limits<uint64_t>::max())) {}
diff --git a/src/txmempool.h b/src/txmempool.h
index 15797cbc00..9a1aa9bc2b 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -15,13 +15,13 @@
 
 #include <amount.h>
 #include <coins.h>
-#include <crypto/siphash.h>
 #include <indirectmap.h>
 #include <optional.h>
 #include <policy/feerate.h>
 #include <primitives/transaction.h>
 #include <sync.h>
 #include <random.h>
+#include <util/hasher.h>
 
 #include <boost/multi_index_container.hpp>
 #include <boost/multi_index/hashed_index.hpp>
@@ -398,20 +398,6 @@ enum class MemPoolRemovalReason {
     REPLACED,    //!< Removed for replacement
 };
 
-class SaltedTxidHasher
-{
-private:
-    /** Salt */
-    const uint64_t k0, k1;
-
-public:
-    SaltedTxidHasher();
-
-    size_t operator()(const uint256& txid) const {
-        return SipHashUint256(k0, k1, txid);
-    }
-};
-
 /**
  * CTxMemPool stores valid-according-to-the-current-best-chain transactions
  * that may be included in the next block.
diff --git a/src/util/hasher.cpp b/src/util/hasher.cpp
new file mode 100644
index 0000000000..5900daf050
--- /dev/null
+++ b/src/util/hasher.cpp
@@ -0,0 +1,19 @@
+// Copyright (c) 2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <random.h>
+#include <util/hasher.h>
+
+#include <limits>
+
+SaltedTxidHasher::SaltedTxidHasher() : k0(GetRand(std::numeric_limits<uint64_t>::max())), k1(GetRand(std::numeric_limits<uint64_t>::max())) {}
+
+SaltedOutpointHasher::SaltedOutpointHasher() : k0(GetRand(std::numeric_limits<uint64_t>::max())), k1(GetRand(std::numeric_limits<uint64_t>::max())) {}
+
+SaltedSipHasher::SaltedSipHasher() : m_k0(GetRand(std::numeric_limits<uint64_t>::max())), m_k1(GetRand(std::numeric_limits<uint64_t>::max())) {}
+
+size_t SaltedSipHasher::operator()(const Span<const unsigned char>& script) const
+{
+    return CSipHasher(m_k0, m_k1).Write(script.data(), script.size()).Finalize();
+}
diff --git a/src/util/hasher.h b/src/util/hasher.h
new file mode 100644
index 0000000000..fa2fea30d8
--- /dev/null
+++ b/src/util/hasher.h
@@ -0,0 +1,99 @@
+// Copyright (c) 2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_HASHER_H
+#define BITCOIN_UTIL_HASHER_H
+
+#include <crypto/siphash.h>
+#include <primitives/transaction.h>
+#include <uint256.h>
+
+class SaltedTxidHasher
+{
+private:
+    /** Salt */
+    const uint64_t k0, k1;
+
+public:
+    SaltedTxidHasher();
+
+    size_t operator()(const uint256& txid) const {
+        return SipHashUint256(k0, k1, txid);
+    }
+};
+
+class SaltedOutpointHasher
+{
+private:
+    /** Salt */
+    const uint64_t k0, k1;
+
+public:
+    SaltedOutpointHasher();
+
+    /**
+     * This *must* return size_t. With Boost 1.46 on 32-bit systems the
+     * unordered_map will behave unpredictably if the custom hasher returns a
+     * uint64_t, resulting in failures when syncing the chain (#4634).
+     *
+     * Having the hash noexcept allows libstdc++'s unordered_map to recalculate
+     * the hash during rehash, so it does not have to cache the value. This
+     * reduces node's memory by sizeof(size_t). The required recalculation has
+     * a slight performance penalty (around 1.6%), but this is compensated by
+     * memory savings of about 9% which allow for a larger dbcache setting.
+     *
+     * @see https://gcc.gnu.org/onlinedocs/gcc-9.2.0/libstdc++/manual/manual/unordered_associative.html
+     */
+    size_t operator()(const COutPoint& id) const noexcept {
+        return SipHashUint256Extra(k0, k1, id.hash, id.n);
+    }
+};
+
+struct FilterHeaderHasher
+{
+    size_t operator()(const uint256& hash) const { return ReadLE64(hash.begin()); }
+};
+
+/**
+ * We're hashing a nonce into the entries themselves, so we don't need extra
+ * blinding in the set hash computation.
+ *
+ * This may exhibit platform endian dependent behavior but because these are
+ * nonced hashes (random) and this state is only ever used locally it is safe.
+ * All that matters is local consistency.
+ */
+class SignatureCacheHasher
+{
+public:
+    template <uint8_t hash_select>
+    uint32_t operator()(const uint256& key) const
+    {
+        static_assert(hash_select <8, "SignatureCacheHasher only has 8 hashes available.");
+        uint32_t u;
+        std::memcpy(&u, key.begin()+4*hash_select, 4);
+        return u;
+    }
+};
+
+struct BlockHasher
+{
+    // this used to call `GetCheapHash()` in uint256, which was later moved; the
+    // cheap hash function simply calls ReadLE64() however, so the end result is
+    // identical
+    size_t operator()(const uint256& hash) const { return ReadLE64(hash.begin()); }
+};
+
+class SaltedSipHasher
+{
+private:
+    /** Salt */
+    const uint64_t m_k0, m_k1;
+
+public:
+    SaltedSipHasher();
+
+    size_t operator()(const Span<const unsigned char>& script) const;
+};
+
+#endif // BITCOIN_UTIL_HASHER_H
diff --git a/src/validation.h b/src/validation.h
index d10b260d8a..1b4e40cd53 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -23,6 +23,7 @@
 #include <txdb.h>
 #include <versionbits.h>
 #include <serialize.h>
+#include <util/hasher.h>
 
 #include <atomic>
 #include <map>
@@ -93,14 +94,6 @@ static const unsigned int DEFAULT_CHECKLEVEL = 3;
 // Setting the target to >= 550 MiB will make it likely we can respect the target.
 static const uint64_t MIN_DISK_SPACE_FOR_BLOCK_FILES = 550 * 1024 * 1024;
 
-struct BlockHasher
-{
-    // this used to call `GetCheapHash()` in uint256, which was later moved; the
-    // cheap hash function simply calls ReadLE64() however, so the end result is
-    // identical
-    size_t operator()(const uint256& hash) const { return ReadLE64(hash.begin()); }
-};
-
 /** Current sync state passed to tip changed callbacks. */
 enum class SynchronizationState {
     INIT_REINDEX,
diff --git a/src/wallet/scriptpubkeyman.h b/src/wallet/scriptpubkeyman.h
index cec46a0fbb..8f6b69bc78 100644
--- a/src/wallet/scriptpubkeyman.h
+++ b/src/wallet/scriptpubkeyman.h
@@ -304,7 +304,7 @@ private:
 
     /* the HD chain data model (external chain counters) */
     CHDChain m_hd_chain;
-    std::unordered_map<CKeyID, CHDChain, KeyIDHasher> m_inactive_hd_chains;
+    std::unordered_map<CKeyID, CHDChain, SaltedSipHasher> m_inactive_hd_chains;
 
     /* HD derive new child key (on internal or external chain) */
     void DeriveNewChildKey(WalletBatch& batch, CKeyMetadata& metadata, CKey& secret, CHDChain& hd_chain, bool internal = false) EXCLUSIVE_LOCKS_REQUIRED(cs_KeyStore);
diff --git a/test/sanitizer_suppressions/tsan b/test/sanitizer_suppressions/tsan
index 29221a94f2..3a04418e8b 100644
--- a/test/sanitizer_suppressions/tsan
+++ b/test/sanitizer_suppressions/tsan
@@ -13,7 +13,7 @@ mutex:CConnman::ThreadOpenConnections
 mutex:CConnman::ThreadOpenAddedConnections
 mutex:CConnman::SocketHandler
 mutex:UpdateTip
-mutex:PeerManager::UpdatedBlockTip
+mutex:PeerManagerImpl::UpdatedBlockTip
 mutex:g_best_block_mutex
 
 # race (TODO fix)