Merge branch 'develop' into ximinez/fix-getledger

* upstream/develop:
  ci: Add dependabot config (6379)
  Fix tautological assertion (6393)

include/xrpl/basics/CanProcess.h

@@ -78,11 +78,6 @@ public:
             cleanup_();
     }
 
-    CanProcess(CanProcess const&) = delete;
-
-    CanProcess&
-    operator=(CanProcess const&) = delete;
-
     explicit
     operator bool() const
     {

include/xrpl/core/HashRouter.h

@@ -139,6 +139,13 @@ private:
             return std::move(peers_);
         }
 
+        /** Return set of peers waiting for reply. Leaves list unchanged. */
+        std::set<PeerShortID> const&
+        peekPeerSet()
+        {
+            return peers_;
+        }
+
         /** Return seated relay time point if the message has been relayed */
         std::optional<Stopwatch::time_point>
         relayed() const
@@ -170,6 +177,20 @@ private:
             return true;
         }
 
+        bool
+        shouldProcessForPeer(
+            PeerShortID peer,
+            Stopwatch::time_point now,
+            std::chrono::seconds interval)
+        {
+            if (peerProcessed_.contains(peer) && ((peerProcessed_[peer] + interval) > now))
+                return false;
+            // Peer may already be in the list, but adding it again doesn't hurt
+            addPeer(peer);
+            peerProcessed_[peer] = now;
+            return true;
+        }
+
     private:
         HashRouterFlags flags_ = HashRouterFlags::UNDEFINED;
         std::set<PeerShortID> peers_;
@@ -177,6 +198,7 @@ private:
         // than one flag needs to expire independently.
         std::optional<Stopwatch::time_point> relayed_;
         std::optional<Stopwatch::time_point> processed_;
+        std::map<PeerShortID, Stopwatch::time_point> peerProcessed_;
     };
 
 public:
@@ -216,6 +238,15 @@ public:
         HashRouterFlags& flags,
         std::chrono::seconds tx_interval);
 
+    /** Determines whether the hashed item should be processed for the given
+       peer. Could be an incoming or outgoing message.
+
+       Items filtered with this function should only be processed for the given
+       peer once. Unlike shouldProcess, it can be processed for other peers.
+     */
+    bool
+    shouldProcessForPeer(uint256 const& key, PeerShortID peer, std::chrono::seconds interval);
+
     /** Set the flags on a hash.
 
         @return `true` if the flags were changed. `false` if unchanged.
@@ -241,6 +272,11 @@ public:
     std::optional<std::set<PeerShortID>>
     shouldRelay(uint256 const& key);
 
+    /** Returns a copy of the set of peers in the Entry for the key
+     */
+    std::set<PeerShortID>
+    getPeers(uint256 const& key);
+
 private:
     // pair.second indicates whether the entry was created
     std::pair<Entry&, bool>

include/xrpl/proto/xrpl.proto

@@ -286,8 +286,18 @@ message TMLedgerData {
   required uint32 ledgerSeq = 2;
   required TMLedgerInfoType type = 3;
   repeated TMLedgerNode nodes = 4;
+  // If the peer supports "responseCookies", this field will
+  // never be populated.
   optional uint32 requestCookie = 5;
   optional TMReplyError error = 6;
+  // The old field is called "requestCookie", but this is
+  // a response, so this name makes more sense
+  repeated uint32 responseCookies = 7;
+  // If a TMGetLedger request was received without a "requestCookie",
+  // and the peer supports it, this flag will be set to true to
+  // indicate that the receiver should process the result in addition
+  // to forwarding it to its "responseCookies" peers.
+  optional bool directResponse = 8;
 }
 
 message TMPing {

src/libxrpl/core/HashRouter.cpp

@@ -70,6 +70,19 @@ HashRouter::shouldProcess(
     return s.shouldProcess(suppressionMap_.clock().now(), tx_interval);
 }
 
+bool
+HashRouter::shouldProcessForPeer(
+    uint256 const& key,
+    PeerShortID peer,
+    std::chrono::seconds interval)
+{
+    std::lock_guard lock(mutex_);
+
+    auto& entry = emplace(key).first;
+
+    return entry.shouldProcessForPeer(peer, suppressionMap_.clock().now(), interval);
+}
+
 HashRouterFlags
 HashRouter::getFlags(uint256 const& key)
 {
@@ -107,4 +120,13 @@ HashRouter::shouldRelay(uint256 const& key) -> std::optional<std::set<PeerShortI
     return s.releasePeerSet();
 }
 
+auto
+HashRouter::getPeers(uint256 const& key) -> std::set<PeerShortID>
+{
+    std::lock_guard lock(mutex_);
+
+    auto& s = emplace(key).first;
+    return s.peekPeerSet();
+}
+
 }  // namespace xrpl

src/test/app/HashRouter_test.cpp

@@ -388,6 +388,33 @@ class HashRouter_test : public beast::unit_test::suite
         BEAST_EXPECT(!any(HF::UNDEFINED));
     }
 
+    void
+    testProcessPeer()
+    {
+        using namespace std::chrono_literals;
+        TestStopwatch stopwatch;
+        HashRouter router(getSetup(5s, 5s), stopwatch);
+        uint256 const key(1);
+        HashRouter::PeerShortID peer1 = 1;
+        HashRouter::PeerShortID peer2 = 2;
+        auto const timeout = 2s;
+
+        BEAST_EXPECT(router.shouldProcessForPeer(key, peer1, timeout));
+        BEAST_EXPECT(!router.shouldProcessForPeer(key, peer1, timeout));
+        ++stopwatch;
+        BEAST_EXPECT(!router.shouldProcessForPeer(key, peer1, timeout));
+        BEAST_EXPECT(router.shouldProcessForPeer(key, peer2, timeout));
+        BEAST_EXPECT(!router.shouldProcessForPeer(key, peer2, timeout));
+        ++stopwatch;
+        BEAST_EXPECT(router.shouldProcessForPeer(key, peer1, timeout));
+        BEAST_EXPECT(!router.shouldProcessForPeer(key, peer2, timeout));
+        ++stopwatch;
+        BEAST_EXPECT(router.shouldProcessForPeer(key, peer2, timeout));
+        ++stopwatch;
+        BEAST_EXPECT(router.shouldProcessForPeer(key, peer1, timeout));
+        BEAST_EXPECT(!router.shouldProcessForPeer(key, peer2, timeout));
+    }
+
 public:
     void
     run() override
@@ -400,6 +427,7 @@ public:
         testProcess();
         testSetup();
         testFlagsOps();
+        testProcessPeer();
     }
 };
 

src/test/app/LedgerReplay_test.cpp

@@ -85,12 +85,7 @@ public:
     }
 
     virtual void
-    acquireAsync(
-        JobType type,
-        std::string const& name,
-        uint256 const& hash,
-        std::uint32_t seq,
-        InboundLedger::Reason reason) override
+    acquireAsync(uint256 const& hash, std::uint32_t seq, InboundLedger::Reason reason) override
     {
     }
 
@@ -301,6 +296,11 @@ public:
     {
         return false;
     }
+    std::set<std::optional<uint64_t>>
+    releaseRequestCookies(uint256 const& requestHash) override
+    {
+        return {};
+    }
 
     std::string const&
     fingerprint() const override

src/test/basics/CanProcess_test.cpp

@@ -1,165 +0,0 @@
-//------------------------------------------------------------------------------
-/*
-    This file is part of rippled: https://github.com/ripple/rippled
-    Copyright (c) 2012-2016 Ripple Labs Inc.
-
-    Permission to use, copy, modify, and/or distribute this software for any
-    purpose  with  or without fee is hereby granted, provided that the above
-    copyright notice and this permission notice appear in all copies.
-
-    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
-    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
-    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
-    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
-    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
-    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
-    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
-*/
-//==============================================================================
-
-#include <xrpl/basics/CanProcess.h>
-#include <xrpl/beast/unit_test.h>
-
-#include <memory>
-
-namespace ripple {
-namespace test {
-
-struct CanProcess_test : beast::unit_test::suite
-{
-    template <class Mutex, class Collection, class Item>
-    void
-    test(
-        std::string const& name,
-        Mutex& mtx,
-        Collection& collection,
-        std::vector<Item> const& items)
-    {
-        testcase(name);
-
-        if (!BEAST_EXPECT(!items.empty()))
-            return;
-        if (!BEAST_EXPECT(collection.empty()))
-            return;
-
-        // CanProcess objects can't be copied or moved. To make that easier,
-        // store shared_ptrs
-        std::vector<std::shared_ptr<CanProcess>> trackers;
-        // Fill up the vector with two CanProcess for each Item. The first
-        // inserts the item into the collection and is "good". The second does
-        // not and is "bad".
-        for (int i = 0; i < items.size(); ++i)
-        {
-            {
-                auto const& good =
-                    trackers.emplace_back(std::make_shared<CanProcess>(mtx, collection, items[i]));
-                BEAST_EXPECT(*good);
-            }
-            BEAST_EXPECT(trackers.size() == (2 * i) + 1);
-            BEAST_EXPECT(collection.size() == i + 1);
-            {
-                auto const& bad =
-                    trackers.emplace_back(std::make_shared<CanProcess>(mtx, collection, items[i]));
-                BEAST_EXPECT(!*bad);
-            }
-            BEAST_EXPECT(trackers.size() == 2 * (i + 1));
-            BEAST_EXPECT(collection.size() == i + 1);
-        }
-        BEAST_EXPECT(collection.size() == items.size());
-        // Now remove the items from the vector<CanProcess> two at a time, and
-        // try to get another CanProcess for that item.
-        for (int i = 0; i < items.size(); ++i)
-        {
-            // Remove the "bad" one in the second position
-            // This will have no effect on the collection
-            {
-                auto const iter = trackers.begin() + 1;
-                BEAST_EXPECT(!**iter);
-                trackers.erase(iter);
-            }
-            BEAST_EXPECT(trackers.size() == (2 * items.size()) - 1);
-            BEAST_EXPECT(collection.size() == items.size());
-            {
-                // Append a new "bad" one
-                auto const& bad =
-                    trackers.emplace_back(std::make_shared<CanProcess>(mtx, collection, items[i]));
-                BEAST_EXPECT(!*bad);
-            }
-            BEAST_EXPECT(trackers.size() == 2 * items.size());
-            BEAST_EXPECT(collection.size() == items.size());
-
-            // Remove the "good" one from the front
-            {
-                auto const iter = trackers.begin();
-                BEAST_EXPECT(**iter);
-                trackers.erase(iter);
-            }
-            BEAST_EXPECT(trackers.size() == (2 * items.size()) - 1);
-            BEAST_EXPECT(collection.size() == items.size() - 1);
-            {
-                // Append a new "good" one
-                auto const& good =
-                    trackers.emplace_back(std::make_shared<CanProcess>(mtx, collection, items[i]));
-                BEAST_EXPECT(*good);
-            }
-            BEAST_EXPECT(trackers.size() == 2 * items.size());
-            BEAST_EXPECT(collection.size() == items.size());
-        }
-        // Now remove them all two at a time
-        for (int i = items.size() - 1; i >= 0; --i)
-        {
-            // Remove the "bad" one from the front
-            {
-                auto const iter = trackers.begin();
-                BEAST_EXPECT(!**iter);
-                trackers.erase(iter);
-            }
-            BEAST_EXPECT(trackers.size() == (2 * i) + 1);
-            BEAST_EXPECT(collection.size() == i + 1);
-            // Remove the "good" one now in front
-            {
-                auto const iter = trackers.begin();
-                BEAST_EXPECT(**iter);
-                trackers.erase(iter);
-            }
-            BEAST_EXPECT(trackers.size() == 2 * i);
-            BEAST_EXPECT(collection.size() == i);
-        }
-        BEAST_EXPECT(trackers.empty());
-        BEAST_EXPECT(collection.empty());
-    }
-
-    void
-    run() override
-    {
-        {
-            std::mutex m;
-            std::set<int> collection;
-            std::vector<int> const items{1, 2, 3, 4, 5};
-            test("set of int", m, collection, items);
-        }
-        {
-            std::mutex m;
-            std::set<std::string> collection;
-            std::vector<std::string> const items{"one", "two", "three", "four", "five"};
-            test("set of string", m, collection, items);
-        }
-        {
-            std::mutex m;
-            std::unordered_set<char> collection;
-            std::vector<char> const items{'1', '2', '3', '4', '5'};
-            test("unorderd_set of char", m, collection, items);
-        }
-        {
-            std::mutex m;
-            std::unordered_set<std::uint64_t> collection;
-            std::vector<std::uint64_t> const items{100u, 1000u, 150u, 4u, 0u};
-            test("unordered_set of uint64_t", m, collection, items);
-        }
-    }
-};
-
-BEAST_DEFINE_TESTSUITE(CanProcess, ripple_basics, ripple);
-
-}  // namespace test
-}  // namespace ripple

src/test/overlay/ProtocolVersion_test.cpp

@@ -66,8 +66,8 @@ public:
                 negotiateProtocolVersion("RTXP/1.2, XRPL/2.0, XRPL/2.1") == make_protocol(2, 1));
             BEAST_EXPECT(negotiateProtocolVersion("XRPL/2.2") == make_protocol(2, 2));
             BEAST_EXPECT(
-                negotiateProtocolVersion("RTXP/1.2, XRPL/2.2, XRPL/2.3, XRPL/999.999") ==
-                make_protocol(2, 2));
+                negotiateProtocolVersion("RTXP/1.2, XRPL/2.2, XRPL/2.3, XRPL/2.4, XRPL/999.999") ==
+                make_protocol(2, 3));
             BEAST_EXPECT(negotiateProtocolVersion("XRPL/999.999, WebSocket/1.0") == std::nullopt);
             BEAST_EXPECT(negotiateProtocolVersion("") == std::nullopt);
         }

src/test/overlay/reduce_relay_test.cpp

@@ -167,6 +167,11 @@ public:
     removeTxQueue(uint256 const&) override
     {
     }
+    std::set<std::optional<uint64_t>>
+    releaseRequestCookies(uint256 const& requestHash) override
+    {
+        return {};
+    }
 };
 
 /** Manually advanced clock. */

src/xrpld/app/consensus/RCLConsensus.cpp

@@ -105,8 +105,10 @@ RCLConsensus::Adaptor::acquireLedger(LedgerHash const& hash)
             // Tell the ledger acquire system that we need the consensus ledger
             acquiringLedger_ = hash;
 
-            app_.getInboundLedgers().acquireAsync(
-                jtADVANCE, "GetConsL1", hash, 0, InboundLedger::Reason::CONSENSUS);
+            app_.getJobQueue().addJob(jtADVANCE, "GetConsL1", [id = hash, &app = app_, this]() {
+                JLOG(j_.debug()) << "JOB advanceLedger getConsensusLedger1 started";
+                app.getInboundLedgers().acquireAsync(id, 0, InboundLedger::Reason::CONSENSUS);
+            });
         }
         return std::nullopt;
     }

src/xrpld/app/consensus/RCLValidations.cpp

@@ -117,8 +117,12 @@ RCLValidationsAdaptor::acquire(LedgerHash const& hash)
     {
         JLOG(j_.warn()) << "Need validated ledger for preferred ledger analysis " << hash;
 
-        app_.getInboundLedgers().acquireAsync(
-            jtADVANCE, "GetConsL2", hash, 0, InboundLedger::Reason::CONSENSUS);
+        Application* pApp = &app_;
+
+        app_.getJobQueue().addJob(jtADVANCE, "GetConsL2", [pApp, hash, this]() {
+            JLOG(j_.debug()) << "JOB advanceLedger getConsensusLedger2 started";
+            pApp->getInboundLedgers().acquireAsync(hash, 0, InboundLedger::Reason::CONSENSUS);
+        });
         return std::nullopt;
     }
 

src/xrpld/app/ledger/InboundLedger.h

@@ -172,4 +172,22 @@ private:
     std::unique_ptr<PeerSet> mPeerSet;
 };
 
+inline std::string
+to_string(InboundLedger::Reason reason)
+{
+    using enum InboundLedger::Reason;
+    switch (reason)
+    {
+        case HISTORY:
+            return "HISTORY";
+        case GENERIC:
+            return "GENERIC";
+        case CONSENSUS:
+            return "CONSENSUS";
+        default:
+            UNREACHABLE("ripple::to_string(InboundLedger::Reason) : unknown value");
+            return "unknown";
+    }
+}
+
 }  // namespace xrpl

src/xrpld/app/ledger/InboundLedgers.h

@@ -26,12 +26,7 @@ public:
     // Queue. TODO review whether all callers of acquire() can use this
     // instead. Inbound ledger acquisition is asynchronous anyway.
     virtual void
-    acquireAsync(
-        JobType type,
-        std::string const& name,
-        uint256 const& hash,
-        std::uint32_t seq,
-        InboundLedger::Reason reason) = 0;
+    acquireAsync(uint256 const& hash, std::uint32_t seq, InboundLedger::Reason reason) = 0;
 
     virtual std::shared_ptr<InboundLedger>
     find(LedgerHash const& hash) = 0;

src/xrpld/app/ledger/detail/InboundLedgers.cpp

@@ -54,12 +54,78 @@ public:
             XRPL_ASSERT(
                 hash.isNonZero(), "xrpl::InboundLedgersImp::acquire::doAcquire : nonzero hash");
 
-            // probably not the right rule
-            if (app_.getOPs().isNeedNetworkLedger() && (reason != InboundLedger::Reason::GENERIC) &&
-                (reason != InboundLedger::Reason::CONSENSUS))
-                return {};
+            bool const needNetworkLedger = app_.getOPs().isNeedNetworkLedger();
+            bool const shouldAcquire = [&]() {
+                if (!needNetworkLedger)
+                    return true;
+                if (reason == InboundLedger::Reason::GENERIC)
+                    return true;
+                if (reason == InboundLedger::Reason::CONSENSUS)
+                    return true;
+                return false;
+            }();
 
             std::stringstream ss;
+            ss << "InboundLedger::acquire: "
+               << "Request: " << to_string(hash) << ", " << seq
+               << " NeedNetworkLedger: " << (needNetworkLedger ? "yes" : "no")
+               << " Reason: " << to_string(reason)
+               << " Should acquire: " << (shouldAcquire ? "true." : "false.");
+
+            /*  Acquiring ledgers is somewhat expensive. It requires lots of
+             *  computation and network communication. Avoid it when it's not
+             *  appropriate. Every validation from a peer for a ledger that
+             *  we do not have locally results in a call to this function: even
+             *  if we are moments away from validating the same ledger.
+             */
+            bool const shouldBroadcast = [&]() {
+                // If the node is not in "full" state, it needs to sync to
+                // the network, and doesn't have the necessary tx's and
+                // ledger entries to build the ledger.
+                bool const isFull = app_.getOPs().isFull();
+                // If everything else is ok, don't try to acquire the ledger
+                // if the requested seq is in the near future relative to
+                // the validated ledger. If the requested ledger is between
+                // 1 and 19 inclusive ledgers ahead of the valid ledger this
+                // node has not built it yet, but it's possible/likely it
+                // has the tx's necessary to build it and get caught up.
+                // Plus it might not become validated. On the other hand, if
+                // it's more than 20 in the future, this node should request
+                // it so that it can jump ahead and get caught up.
+                LedgerIndex const validSeq = app_.getLedgerMaster().getValidLedgerIndex();
+                constexpr std::size_t lagLeeway = 20;
+                bool const nearFuture = (seq > validSeq) && (seq < validSeq + lagLeeway);
+                // If everything else is ok, don't try to acquire the ledger
+                // if the request is related to consensus. (Note that
+                // consensus calls usually pass a seq of 0, so nearFuture
+                // will be false other than on a brand new network.)
+                bool const consensus = reason == InboundLedger::Reason::CONSENSUS;
+                ss << " Evaluating whether to broadcast requests to peers"
+                   << ". full: " << (isFull ? "true" : "false") << ". ledger sequence " << seq
+                   << ". Valid sequence: " << validSeq << ". Lag leeway: " << lagLeeway
+                   << ". request for near future ledger: " << (nearFuture ? "true" : "false")
+                   << ". Consensus: " << (consensus ? "true" : "false");
+
+                // If the node is not synced, send requests.
+                if (!isFull)
+                    return true;
+                // If the ledger is in the near future, do NOT send requests.
+                // This node is probably about to build it.
+                if (nearFuture)
+                    return false;
+                // If the request is because of consensus, do NOT send requests.
+                // This node is probably about to build it.
+                if (consensus)
+                    return false;
+                return true;
+            }();
+            ss << ". Would broadcast to peers? " << (shouldBroadcast ? "true." : "false.");
+
+            if (!shouldAcquire)
+            {
+                JLOG(j_.debug()) << "Abort(rule): " << ss.str();
+                return {};
+            }
 
             bool isNew = true;
             std::shared_ptr<InboundLedger> inbound;
@@ -111,35 +177,25 @@ public:
     }
 
     void
-    acquireAsync(
-        JobType type,
-        std::string const& name,
-        uint256 const& hash,
-        std::uint32_t seq,
-        InboundLedger::Reason reason) override
+    acquireAsync(uint256 const& hash, std::uint32_t seq, InboundLedger::Reason reason) override
     {
-        if (auto check = std::make_shared<CanProcess const>(acquiresMutex_, pendingAcquires_, hash);
-            *check)
+        if (CanProcess const check{acquiresMutex_, pendingAcquires_, hash})
         {
-            app_.getJobQueue().addJob(type, name, [check, name, hash, seq, reason, this]() {
-                JLOG(j_.debug()) << "JOB acquireAsync " << name << " started ";
-                try
-                {
-                    acquire(hash, seq, reason);
-                }
-                catch (std::exception const& e)
-                {
-                    JLOG(j_.warn()) << "Exception thrown for acquiring new "
-                                       "inbound ledger "
-                                    << hash << ": " << e.what();
-                }
-                catch (...)
-                {
-                    JLOG(j_.warn()) << "Unknown exception thrown for acquiring new "
-                                       "inbound ledger "
-                                    << hash;
-                }
-            });
+            try
+            {
+                acquire(hash, seq, reason);
+            }
+            catch (std::exception const& e)
+            {
+                JLOG(j_.warn()) << "Exception thrown for acquiring new inbound ledger " << hash
+                                << ": " << e.what();
+            }
+            catch (...)
+            {
+                JLOG(j_.warn()) << "Unknown exception thrown for acquiring new "
+                                   "inbound ledger "
+                                << hash;
+            }
         }
     }
 

src/xrpld/overlay/Peer.h

@@ -17,6 +17,7 @@ enum class ProtocolFeature {
     ValidatorListPropagation,
     ValidatorList2Propagation,
     LedgerReplay,
+    LedgerDataCookies
 };
 
 /** Represents a peer connection in the overlay. */
@@ -116,6 +117,13 @@ public:
 
     virtual bool
     txReduceRelayEnabled() const = 0;
+
+    //
+    // Messages
+    //
+
+    virtual std::set<std::optional<uint64_t>>
+    releaseRequestCookies(uint256 const& requestHash) = 0;
 };
 
 }  // namespace xrpl

src/xrpld/overlay/detail/PeerImp.cpp

@@ -7,6 +7,7 @@
 #include <xrpld/app/misc/ValidatorList.h>
 #include <xrpld/overlay/Cluster.h>
 #include <xrpld/overlay/detail/PeerImp.h>
+#include <xrpld/overlay/detail/ProtocolMessage.h>
 #include <xrpld/overlay/detail/Tuning.h>
 
 #include <xrpl/basics/UptimeClock.h>
@@ -45,6 +46,8 @@ std::chrono::seconds constexpr peerTimerInterval{60};
 /** The timeout for a shutdown timer */
 std::chrono::seconds constexpr shutdownTimerInterval{5};
 
+/** How often we process duplicate incoming TMGetLedger messages */
+std::chrono::seconds constexpr getledgerInterval{15};
 }  // namespace
 
 // TODO: Remove this exclusion once unit tests are added after the hotfix
@@ -473,6 +476,8 @@ PeerImp::supportsFeature(ProtocolFeature f) const
             return protocol_ >= make_protocol(2, 2);
         case ProtocolFeature::LedgerReplay:
             return ledgerReplayEnabled_;
+        case ProtocolFeature::LedgerDataCookies:
+            return protocol_ >= make_protocol(2, 3);
     }
     return false;
 }
@@ -1394,8 +1399,9 @@ PeerImp::handleTransaction(
 void
 PeerImp::onMessage(std::shared_ptr<protocol::TMGetLedger> const& m)
 {
-    auto badData = [&](std::string const& msg) {
-        fee_.update(Resource::feeInvalidData, "get_ledger " + msg);
+    auto badData = [&](std::string const& msg, bool chargefee = true) {
+        if (chargefee)
+            fee_.update(Resource::feeInvalidData, "get_ledger " + msg);
         JLOG(p_journal_.warn()) << "TMGetLedger: " << msg;
     };
     auto const itype{m->itype()};
@@ -1469,11 +1475,68 @@ PeerImp::onMessage(std::shared_ptr<protocol::TMGetLedger> const& m)
         }
     }
 
+    // Drop duplicate requests from the same peer for at least
+    // `getLedgerInterval` seconds.
+    // Append a little junk to prevent the hash of an incoming messsage
+    // from matching the hash of the same outgoing message.
+    // `shouldProcessForPeer` does not distingish between incoming and
+    // outgoing, and some of the message relay logic checks the hash to see
+    // if the message has been relayed already. If the hashes are the same,
+    // a duplicate will be detected when sending the message is attempted,
+    // so it will fail.
+    auto const messageHash = sha512Half(*m, nullptr);
+    // Request cookies are not included in the hash. Track them here.
+    auto const requestCookie = [&m]() -> std::optional<uint64_t> {
+        if (m->has_requestcookie())
+            return m->requestcookie();
+        return std::nullopt;
+    }();
+    auto const [inserted, pending] = [&] {
+        std::lock_guard lock{cookieLock_};
+        auto& cookies = messageRequestCookies_[messageHash];
+        bool const pending = !cookies.empty();
+        return std::pair{cookies.emplace(requestCookie).second, pending};
+    }();
+    // Check if the request has been seen from this peer.
+    if (!app_.getHashRouter().shouldProcessForPeer(messageHash, id_, getledgerInterval))
+    {
+        // This request has already been seen from this peer.
+        // Has it been seen with this request cookie (or lack thereof)?
+
+        if (inserted)
+        {
+            // This is a duplicate request, but with a new cookie. When a
+            // response is ready, one will be sent for each request cookie.
+            JLOG(p_journal_.debug())
+                << "TMGetLedger: duplicate request with new request cookie: "
+                << requestCookie.value_or(0) << ". Job pending: " << (pending ? "yes" : "no")
+                << ": " << messageHash;
+            if (pending)
+            {
+                // Don't bother queueing up a new job if other requests are
+                // already pending. This should limit entries in the job queue
+                // to one per peer per unique request.
+                JLOG(p_journal_.debug()) << "TMGetLedger: Suppressing recvGetLedger job, since one "
+                                            "is pending: "
+                                         << messageHash;
+                return;
+            }
+        }
+        else
+        {
+            // Don't punish nodes that don't know any better
+            return badData(
+                "duplicate request: " + to_string(messageHash),
+                supportsFeature(ProtocolFeature::LedgerDataCookies));
+        }
+    }
+
     // Queue a job to process the request
+    JLOG(p_journal_.debug()) << "TMGetLedger: Adding recvGetLedger job: " << messageHash;
     std::weak_ptr<PeerImp> weak = shared_from_this();
-    app_.getJobQueue().addJob(jtLEDGER_REQ, "RcvGetLedger", [weak, m]() {
+    app_.getJobQueue().addJob(jtLEDGER_REQ, "RcvGetLedger", [weak, m, messageHash]() {
         if (auto peer = weak.lock())
-            peer->processLedgerRequest(m);
+            peer->processLedgerRequest(m, messageHash);
     });
 }
 
@@ -1572,8 +1635,9 @@ PeerImp::onMessage(std::shared_ptr<protocol::TMReplayDeltaResponse> const& m)
 void
 PeerImp::onMessage(std::shared_ptr<protocol::TMLedgerData> const& m)
 {
-    auto badData = [&](std::string const& msg) {
-        fee_.update(Resource::feeInvalidData, msg);
+    auto badData = [&](std::string const& msg, bool charge = true) {
+        if (charge)
+            fee_.update(Resource::feeInvalidData, msg);
         JLOG(p_journal_.warn()) << "TMLedgerData: " << msg;
     };
 
@@ -1620,23 +1684,96 @@ PeerImp::onMessage(std::shared_ptr<protocol::TMLedgerData> const& m)
         return badData("Invalid Ledger/TXset nodes " + std::to_string(m->nodes_size()));
     }
 
-    // If there is a request cookie, attempt to relay the message
-    if (m->has_requestcookie())
+    auto const messageHash = sha512Half(*m);
+    if (!app_.getHashRouter().addSuppressionPeer(messageHash, id_))
     {
-        if (auto peer = overlay_.findPeerByShortID(m->requestcookie()))
+        // Don't punish nodes that don't know any better
+        return badData(
+            "Duplicate message: " + to_string(messageHash),
+            supportsFeature(ProtocolFeature::LedgerDataCookies));
+    }
+
+    bool const routed =
+        m->has_directresponse() || m->responsecookies_size() || m->has_requestcookie();
+
+    {
+        // Check if this message needs to be forwarded to one or more peers.
+        // Maximum of one of the relevant fields should be populated.
+        XRPL_ASSERT(
+            !m->has_requestcookie() || !m->responsecookies_size(),
+            "ripple::PeerImp::onMessage(TMLedgerData) : valid cookie fields");
+
+        // Make a copy of the response cookies, then wipe the list so it can be
+        // forwarded cleanly
+        auto const responseCookies = m->responsecookies();
+        m->clear_responsecookies();
+        // Flag indicating if this response should be processed locally,
+        // possibly in addition to being forwarded.
+        bool const directResponse = m->has_directresponse() && m->directresponse();
+        m->clear_directresponse();
+
+        auto const relay = [this, m, &messageHash](auto const cookie) {
+            if (auto peer = overlay_.findPeerByShortID(cookie))
+            {
+                XRPL_ASSERT(
+                    !m->has_requestcookie() && !m->responsecookies_size(),
+                    "ripple::PeerImp::onMessage(TMLedgerData) relay : no "
+                    "cookies");
+                if (peer->supportsFeature(ProtocolFeature::LedgerDataCookies))
+                    // Setting this flag is not _strictly_ necessary for peers
+                    // that support it if there are no cookies included in the
+                    // message, but it is more accurate.
+                    m->set_directresponse(true);
+                else
+                    m->clear_directresponse();
+                peer->send(std::make_shared<Message>(*m, protocol::mtLEDGER_DATA));
+            }
+            else
+                JLOG(p_journal_.info()) << "Unable to route TX/ledger data reply to peer ["
+                                        << cookie << "]: " << messageHash;
+        };
+        // If there is a request cookie, attempt to relay the message
+        if (m->has_requestcookie())
         {
+            XRPL_ASSERT(
+                responseCookies.empty(),
+                "ripple::PeerImp::onMessage(TMLedgerData) : no response "
+                "cookies");
             m->clear_requestcookie();
-            peer->send(std::make_shared<Message>(*m, protocol::mtLEDGER_DATA));
+            relay(m->requestcookie());
+            if (!directResponse && responseCookies.empty())
+                return;
         }
-        else
+        // If there's a list of request cookies, attempt to relay the message to
+        // all of them.
+        if (responseCookies.size())
         {
-            JLOG(p_journal_.info()) << "Unable to route TX/ledger data reply";
+            for (auto const cookie : responseCookies)
+                relay(cookie);
+            if (!directResponse)
+                return;
+        }
+    }
+
+    // Now that any forwarding is done check the base message (data only, no
+    // routing info for duplicates)
+    if (routed)
+    {
+        m->clear_directresponse();
+        XRPL_ASSERT(
+            !m->has_requestcookie() && !m->responsecookies_size(),
+            "ripple::PeerImp::onMessage(TMLedgerData) : no cookies");
+        auto const baseMessageHash = sha512Half(*m);
+        if (!app_.getHashRouter().addSuppressionPeer(baseMessageHash, id_))
+        {
+            // Don't punish nodes that don't know any better
+            return badData(
+                "Duplicate message: " + to_string(baseMessageHash),
+                supportsFeature(ProtocolFeature::LedgerDataCookies));
         }
-        return;
     }
 
     uint256 const ledgerHash{m->ledgerhash()};
-
     // Otherwise check if received data for a candidate transaction set
     if (m->type() == protocol::liTS_CANDIDATE)
     {
@@ -2946,16 +3083,21 @@ PeerImp::checkValidation(
 // the TX tree with the specified root hash.
 //
 static std::shared_ptr<PeerImp>
-getPeerWithTree(OverlayImpl& ov, uint256 const& rootHash, PeerImp const* skip)
+getPeerWithTree(
+    OverlayImpl& ov,
+    uint256 const& rootHash,
+    PeerImp const* skip,
+    std::function<bool(Peer::id_t)> shouldProcessCallback)
 {
     std::shared_ptr<PeerImp> ret;
     int retScore = 0;
 
+    XRPL_ASSERT(shouldProcessCallback, "ripple::getPeerWithTree : callback provided");
     ov.for_each([&](std::shared_ptr<PeerImp>&& p) {
         if (p->hasTxSet(rootHash) && p.get() != skip)
         {
             auto score = p->getScore(true);
-            if (!ret || (score > retScore))
+            if (!ret || (score > retScore && shouldProcessCallback(p->id())))
             {
                 ret = std::move(p);
                 retScore = score;
@@ -2974,16 +3116,18 @@ getPeerWithLedger(
     OverlayImpl& ov,
     uint256 const& ledgerHash,
     LedgerIndex ledger,
-    PeerImp const* skip)
+    PeerImp const* skip,
+    std::function<bool(Peer::id_t)> shouldProcessCallback)
 {
     std::shared_ptr<PeerImp> ret;
     int retScore = 0;
 
+    XRPL_ASSERT(shouldProcessCallback, "ripple::getPeerWithLedger : callback provided");
     ov.for_each([&](std::shared_ptr<PeerImp>&& p) {
         if (p->hasLedger(ledgerHash, ledger) && p.get() != skip)
         {
             auto score = p->getScore(true);
-            if (!ret || (score > retScore))
+            if (!ret || (score > retScore && shouldProcessCallback(p->id())))
             {
                 ret = std::move(p);
                 retScore = score;
@@ -2997,7 +3141,8 @@ getPeerWithLedger(
 void
 PeerImp::sendLedgerBase(
     std::shared_ptr<Ledger const> const& ledger,
-    protocol::TMLedgerData& ledgerData)
+    protocol::TMLedgerData& ledgerData,
+    PeerCookieMap const& destinations)
 {
     JLOG(p_journal_.trace()) << "sendLedgerBase: Base data";
 
@@ -3027,14 +3172,92 @@ PeerImp::sendLedgerBase(
         }
     }
 
-    auto message{std::make_shared<Message>(ledgerData, protocol::mtLEDGER_DATA)};
-    send(message);
+    sendToMultiple(ledgerData, destinations);
+}
+
+void
+PeerImp::sendToMultiple(protocol::TMLedgerData& ledgerData, PeerCookieMap const& destinations)
+{
+    bool foundSelf = false;
+    for (auto const& [peer, cookies] : destinations)
+    {
+        if (peer.get() == this)
+            foundSelf = true;
+        bool const multipleCookies = peer->supportsFeature(ProtocolFeature::LedgerDataCookies);
+        std::vector<std::uint64_t> sendCookies;
+
+        bool directResponse = false;
+        if (!multipleCookies)
+        {
+            JLOG(p_journal_.debug()) << "sendToMultiple: Sending " << cookies.size()
+                                     << " TMLedgerData messages to peer [" << peer->id()
+                                     << "]: " << sha512Half(ledgerData);
+        }
+        for (auto const& cookie : cookies)
+        {
+            // Unfortunately, need a separate Message object for every
+            // combination
+            if (cookie)
+            {
+                if (multipleCookies)
+                {
+                    // Save this one for later to send a single message
+                    sendCookies.emplace_back(*cookie);
+                    continue;
+                }
+
+                // Feature not supported, so send a single message with a
+                // single cookie
+                ledgerData.set_requestcookie(*cookie);
+            }
+            else
+            {
+                if (multipleCookies)
+                {
+                    // Set this flag later on the single message
+                    directResponse = true;
+                    continue;
+                }
+
+                ledgerData.clear_requestcookie();
+            }
+            XRPL_ASSERT(
+                !multipleCookies,
+                "ripple::PeerImp::sendToMultiple : ledger data cookies "
+                "unsupported");
+            auto message{std::make_shared<Message>(ledgerData, protocol::mtLEDGER_DATA)};
+            peer->send(message);
+        }
+        if (multipleCookies)
+        {
+            // Send a single message with all the cookies and/or the direct
+            // response flag, so the receiver can farm out the single message to
+            // multiple peers and/or itself
+            XRPL_ASSERT(
+                sendCookies.size() || directResponse,
+                "ripple::PeerImp::sendToMultiple : valid response options");
+            ledgerData.clear_requestcookie();
+            ledgerData.clear_responsecookies();
+            ledgerData.set_directresponse(directResponse);
+            for (auto const& cookie : sendCookies)
+                ledgerData.add_responsecookies(cookie);
+            auto message{std::make_shared<Message>(ledgerData, protocol::mtLEDGER_DATA)};
+            peer->send(message);
+
+            JLOG(p_journal_.debug())
+                << "sendToMultiple: Sent 1 TMLedgerData message to peer [" << peer->id()
+                << "]: including " << (directResponse ? "the direct response flag and " : "")
+                << sendCookies.size() << " response cookies. "
+                << ": " << sha512Half(ledgerData);
+        }
+    }
+    XRPL_ASSERT(foundSelf, "ripple::PeerImp::sendToMultiple : current peer included");
 }
 
 std::shared_ptr<Ledger const>
-PeerImp::getLedger(std::shared_ptr<protocol::TMGetLedger> const& m)
+PeerImp::getLedger(std::shared_ptr<protocol::TMGetLedger> const& m, uint256 const& mHash)
 {
-    JLOG(p_journal_.trace()) << "getLedger: Ledger";
+    JLOG(p_journal_.trace()) << "getLedger: Ledger " << mHash;
 
     std::shared_ptr<Ledger const> ledger;
 
@@ -3050,16 +3273,30 @@ PeerImp::getLedger(std::shared_ptr<protocol::TMGetLedger> const& m)
             if (m->has_querytype() && !m->has_requestcookie())
             {
                 // Attempt to relay the request to a peer
+                // Note repeated messages will not relay to the same peer
+                // before `getLedgerInterval` seconds. This prevents one
+                // peer from getting flooded, and distributes the request
+                // load. If a request has been relayed to all eligible
+                // peers, then this message will not be relayed.
                 if (auto const peer = getPeerWithLedger(
-                        overlay_, ledgerHash, m->has_ledgerseq() ? m->ledgerseq() : 0, this))
+                        overlay_,
+                        ledgerHash,
+                        m->has_ledgerseq() ? m->ledgerseq() : 0,
+                        this,
+                        [&](Peer::id_t id) {
+                            return app_.getHashRouter().shouldProcessForPeer(
+                                mHash, id, getledgerInterval);
+                        }))
                 {
                     m->set_requestcookie(id());
                     peer->send(std::make_shared<Message>(*m, protocol::mtGET_LEDGER));
-                    JLOG(p_journal_.debug()) << "getLedger: Request relayed to peer";
+                    JLOG(p_journal_.debug())
+                        << "getLedger: Request relayed to peer [" << peer->id() << "]: " << mHash;
                     return ledger;
                 }
 
-                JLOG(p_journal_.trace()) << "getLedger: Failed to find peer to relay request";
+                JLOG(p_journal_.trace())
+                    << "getLedger: Don't have ledger with hash " << ledgerHash << ": " << mHash;
             }
         }
     }
@@ -3068,15 +3305,15 @@ PeerImp::getLedger(std::shared_ptr<protocol::TMGetLedger> const& m)
         // Attempt to find ledger by sequence
         if (m->ledgerseq() < app_.getLedgerMaster().getEarliestFetch())
         {
-            JLOG(p_journal_.debug()) << "getLedger: Early ledger sequence request";
+            JLOG(p_journal_.debug()) << "getLedger: Early ledger sequence request " << mHash;
         }
         else
         {
             ledger = app_.getLedgerMaster().getLedgerBySeq(m->ledgerseq());
             if (!ledger)
             {
-                JLOG(p_journal_.debug())
-                    << "getLedger: Don't have ledger with sequence " << m->ledgerseq();
+                JLOG(p_journal_.debug()) << "getLedger: Don't have ledger with sequence "
+                                         << m->ledgerseq() << ": " << mHash;
             }
         }
     }
@@ -3098,27 +3335,29 @@ PeerImp::getLedger(std::shared_ptr<protocol::TMGetLedger> const& m)
                     charge(Resource::feeMalformedRequest, "get_ledger ledgerSeq");
 
                 ledger.reset();
-                JLOG(p_journal_.warn()) << "getLedger: Invalid ledger sequence " << ledgerSeq;
+                JLOG(p_journal_.warn())
+                    << "getLedger: Invalid ledger sequence " << ledgerSeq << ": " << mHash;
             }
         }
         else if (ledgerSeq < app_.getLedgerMaster().getEarliestFetch())
         {
             ledger.reset();
-            JLOG(p_journal_.debug()) << "getLedger: Early ledger sequence request " << ledgerSeq;
+            JLOG(p_journal_.debug())
+                << "getLedger: Early ledger sequence request " << ledgerSeq << ": " << mHash;
         }
     }
     else
     {
-        JLOG(p_journal_.debug()) << "getLedger: Unable to find ledger";
+        JLOG(p_journal_.debug()) << "getLedger: Unable to find ledger " << mHash;
     }
 
     return ledger;
 }
 
 std::shared_ptr<SHAMap const>
-PeerImp::getTxSet(std::shared_ptr<protocol::TMGetLedger> const& m) const
+PeerImp::getTxSet(std::shared_ptr<protocol::TMGetLedger> const& m, uint256 const& mHash) const
 {
-    JLOG(p_journal_.trace()) << "getTxSet: TX set";
+    JLOG(p_journal_.trace()) << "getTxSet: TX set " << mHash;
 
     uint256 const txSetHash{m->ledgerhash()};
     std::shared_ptr<SHAMap> shaMap{app_.getInboundTransactions().getSet(txSetHash, false)};
@@ -3127,20 +3366,28 @@ PeerImp::getTxSet(std::shared_ptr<protocol::TMGetLedger> const& m) const
         if (m->has_querytype() && !m->has_requestcookie())
         {
             // Attempt to relay the request to a peer
-            if (auto const peer = getPeerWithTree(overlay_, txSetHash, this))
+            // Note repeated messages will not relay to the same peer
+            // before `getLedgerInterval` seconds. This prevents one
+            // peer from getting flooded, and distributes the request
+            // load. If a request has been relayed to all eligible
+            // peers, then this message will not be relayed.
+            if (auto const peer = getPeerWithTree(overlay_, txSetHash, this, [&](Peer::id_t id) {
+                    return app_.getHashRouter().shouldProcessForPeer(mHash, id, getledgerInterval);
+                }))
             {
                 m->set_requestcookie(id());
                 peer->send(std::make_shared<Message>(*m, protocol::mtGET_LEDGER));
-                JLOG(p_journal_.debug()) << "getTxSet: Request relayed";
+                JLOG(p_journal_.debug())
+                    << "getTxSet: Request relayed to peer [" << peer->id() << "]: " << mHash;
             }
             else
             {
-                JLOG(p_journal_.debug()) << "getTxSet: Failed to find relay peer";
+                JLOG(p_journal_.debug()) << "getTxSet: Failed to find relay peer: " << mHash;
             }
         }
         else
         {
-            JLOG(p_journal_.debug()) << "getTxSet: Failed to find TX set";
+            JLOG(p_journal_.debug()) << "getTxSet: Failed to find TX set " << mHash;
         }
     }
 
@@ -3148,7 +3395,7 @@ PeerImp::getTxSet(std::shared_ptr<protocol::TMGetLedger> const& m) const
 }
 
 void
-PeerImp::processLedgerRequest(std::shared_ptr<protocol::TMGetLedger> const& m)
+PeerImp::processLedgerRequest(std::shared_ptr<protocol::TMGetLedger> const& m, uint256 const& mHash)
 {
     // Do not resource charge a peer responding to a relay
     if (!m->has_requestcookie())
@@ -3161,9 +3408,72 @@ PeerImp::processLedgerRequest(std::shared_ptr<protocol::TMGetLedger> const& m)
     bool fatLeaves{true};
     auto const itype{m->itype()};
 
+    auto getDestinations = [&] {
+        // If a ledger data message is generated, it's going to be sent to every
+        // peer that is waiting for it.
+
+        PeerCookieMap result;
+
+        std::size_t numCookies = 0;
+        {
+            // Don't do the work under this peer if this peer is not waiting for
+            // any replies
+            auto myCookies = releaseRequestCookies(mHash);
+            if (myCookies.empty())
+            {
+                JLOG(p_journal_.debug()) << "TMGetLedger: peer is no longer "
+                                            "waiting for response to request: "
+                                         << mHash;
+                return result;
+            }
+            numCookies += myCookies.size();
+            result[shared_from_this()] = myCookies;
+        }
+
+        std::set<HashRouter::PeerShortID> const peers = app_.getHashRouter().getPeers(mHash);
+        for (auto const peerID : peers)
+        {
+            // This loop does not need to be done under the HashRouter
+            // lock because findPeerByShortID and releaseRequestCookies
+            // are thread safe, and everything else is local
+            if (auto p = overlay_.findPeerByShortID(peerID))
+            {
+                auto cookies = p->releaseRequestCookies(mHash);
+                numCookies += cookies.size();
+                if (result.contains(p))
+                {
+                    // Unlikely, but if a request came in to this peer while
+                    // iterating, add the items instead of copying /
+                    // overwriting.
+                    XRPL_ASSERT(
+                        p.get() == this,
+                        "ripple::PeerImp::processLedgerRequest : found self in "
+                        "map");
+                    for (auto const& cookie : cookies)
+                        result[p].emplace(cookie);
+                }
+                else if (cookies.size())
+                    result[p] = cookies;
+            }
+        }
+
+        JLOG(p_journal_.debug()) << "TMGetLedger: Processing request for " << result.size()
+                                 << " peers. Will send " << numCookies
+                                 << " messages if successful: " << mHash;
+
+        return result;
+    };
+    // Will only populate this if we're going to do work.
+    PeerCookieMap destinations;
+
     if (itype == protocol::liTS_CANDIDATE)
     {
-        if (sharedMap = getTxSet(m); !sharedMap)
+        destinations = getDestinations();
+        if (destinations.empty())
+            // Nowhere to send the response!
+            return;
+
+        if (sharedMap = getTxSet(m, mHash); !sharedMap)
             return;
         map = sharedMap.get();
 
@@ -3171,8 +3481,6 @@ PeerImp::processLedgerRequest(std::shared_ptr<protocol::TMGetLedger> const& m)
         ledgerData.set_ledgerseq(0);
         ledgerData.set_ledgerhash(m->ledgerhash());
         ledgerData.set_type(protocol::liTS_CANDIDATE);
-        if (m->has_requestcookie())
-            ledgerData.set_requestcookie(m->requestcookie());
 
         // We'll already have most transactions
         fatLeaves = false;
@@ -3190,7 +3498,12 @@ PeerImp::processLedgerRequest(std::shared_ptr<protocol::TMGetLedger> const& m)
             return;
         }
 
-        if (ledger = getLedger(m); !ledger)
+        destinations = getDestinations();
+        if (destinations.empty())
+            // Nowhere to send the response!
+            return;
+
+        if (ledger = getLedger(m, mHash); !ledger)
             return;
 
         // Fill out the reply
@@ -3198,13 +3511,11 @@ PeerImp::processLedgerRequest(std::shared_ptr<protocol::TMGetLedger> const& m)
         ledgerData.set_ledgerhash(ledgerHash.begin(), ledgerHash.size());
         ledgerData.set_ledgerseq(ledger->header().seq);
         ledgerData.set_type(itype);
-        if (m->has_requestcookie())
-            ledgerData.set_requestcookie(m->requestcookie());
 
         switch (itype)
         {
             case protocol::liBASE:
-                sendLedgerBase(ledger, ledgerData);
+                sendLedgerBase(ledger, ledgerData, destinations);
                 return;
 
             case protocol::liTX_NODE:
@@ -3313,7 +3624,7 @@ PeerImp::processLedgerRequest(std::shared_ptr<protocol::TMGetLedger> const& m)
     if (ledgerData.nodes_size() == 0)
         return;
 
-    send(std::make_shared<Message>(ledgerData, protocol::mtLEDGER_DATA));
+    sendToMultiple(ledgerData, destinations);
 }
 
 int
@@ -3361,6 +3672,19 @@ PeerImp::isHighLatency() const
     return latency_ >= peerHighLatency;
 }
 
+std::set<std::optional<uint64_t>>
+PeerImp::releaseRequestCookies(uint256 const& requestHash)
+{
+    std::set<std::optional<uint64_t>> result;
+    std::lock_guard lock(cookieLock_);
+    if (messageRequestCookies_.contains(requestHash))
+    {
+        std::swap(result, messageRequestCookies_[requestHash]);
+        messageRequestCookies_.erase(requestHash);
+    }
+    return result;
+};
+
 void
 PeerImp::Metrics::add_message(std::uint64_t bytes)
 {

src/xrpld/overlay/detail/PeerImp.h

@@ -247,6 +247,13 @@ private:
     bool ledgerReplayEnabled_ = false;
     LedgerReplayMsgHandler ledgerReplayMsgHandler_;
 
+    // Track message requests and responses
+    // TODO: Use an expiring cache or something
+    using MessageCookieMap = std::map<uint256, std::set<std::optional<uint64_t>>>;
+    using PeerCookieMap = std::map<std::shared_ptr<Peer>, std::set<std::optional<uint64_t>>>;
+    std::mutex mutable cookieLock_;
+    MessageCookieMap messageRequestCookies_;
+
     friend class OverlayImpl;
 
     class Metrics
@@ -489,6 +496,13 @@ public:
         return txReduceRelayEnabled_;
     }
 
+    //
+    // Messages
+    //
+
+    std::set<std::optional<uint64_t>>
+    releaseRequestCookies(uint256 const& requestHash) override;
+
 private:
     /**
      * @brief Handles a failure associated with a specific error code.
@@ -784,16 +798,22 @@ private:
         std::shared_ptr<protocol::TMValidation> const& packet);
 
     void
-    sendLedgerBase(std::shared_ptr<Ledger const> const& ledger, protocol::TMLedgerData& ledgerData);
-
-    std::shared_ptr<Ledger const>
-    getLedger(std::shared_ptr<protocol::TMGetLedger> const& m);
-
-    std::shared_ptr<SHAMap const>
-    getTxSet(std::shared_ptr<protocol::TMGetLedger> const& m) const;
+    sendLedgerBase(
+        std::shared_ptr<Ledger const> const& ledger,
+        protocol::TMLedgerData& ledgerData,
+        PeerCookieMap const& destinations);
 
     void
-    processLedgerRequest(std::shared_ptr<protocol::TMGetLedger> const& m);
+    sendToMultiple(protocol::TMLedgerData& ledgerData, PeerCookieMap const& destinations);
+
+    std::shared_ptr<Ledger const>
+    getLedger(std::shared_ptr<protocol::TMGetLedger> const& m, uint256 const& mHash);
+
+    std::shared_ptr<SHAMap const>
+    getTxSet(std::shared_ptr<protocol::TMGetLedger> const& m, uint256 const& mHash) const;
+
+    void
+    processLedgerRequest(std::shared_ptr<protocol::TMGetLedger> const& m, uint256 const& mHash);
 };
 
 //------------------------------------------------------------------------------

src/xrpld/overlay/detail/PeerSet.cpp

@@ -2,7 +2,9 @@
 #include <xrpld/overlay/Overlay.h>
 #include <xrpld/overlay/PeerSet.h>
 
+#include <xrpl/core/HashRouter.h>
 #include <xrpl/core/JobQueue.h>
+#include <xrpl/protocol/digest.h>
 
 namespace xrpl {
 
@@ -82,16 +84,45 @@ PeerSetImpl::sendRequest(
     std::shared_ptr<Peer> const& peer)
 {
     auto packet = std::make_shared<Message>(message, type);
+
+    auto const messageHash = [&]() {
+        auto const packetBuffer = packet->getBuffer(compression::Compressed::Off);
+        return sha512Half(Slice(packetBuffer.data(), packetBuffer.size()));
+    }();
+
+    // Allow messages to be re-sent to the same peer after a delay
+    using namespace std::chrono_literals;
+    constexpr std::chrono::seconds interval = 30s;
+
     if (peer)
     {
-        peer->send(packet);
+        if (app_.getHashRouter().shouldProcessForPeer(messageHash, peer->id(), interval))
+        {
+            JLOG(journal_.trace()) << "Sending " << protocolMessageName(type) << " message to ["
+                                   << peer->id() << "]: " << messageHash;
+            peer->send(packet);
+        }
+        else
+            JLOG(journal_.debug()) << "Suppressing sending duplicate " << protocolMessageName(type)
+                                   << " message to [" << peer->id() << "]: " << messageHash;
         return;
     }
 
     for (auto id : peers_)
     {
         if (auto p = app_.overlay().findPeerByShortID(id))
-            p->send(packet);
+        {
+            if (app_.getHashRouter().shouldProcessForPeer(messageHash, p->id(), interval))
+            {
+                JLOG(journal_.trace()) << "Sending " << protocolMessageName(type) << " message to ["
+                                       << p->id() << "]: " << messageHash;
+                p->send(packet);
+            }
+            else
+                JLOG(journal_.debug())
+                    << "Suppressing sending duplicate " << protocolMessageName(type)
+                    << " message to [" << p->id() << "]: " << messageHash;
+        }
     }
 }
 

src/xrpld/overlay/detail/ProtocolMessage.h

@@ -23,6 +23,12 @@ protocolMessageType(protocol::TMGetLedger const&)
     return protocol::mtGET_LEDGER;
 }
 
+inline protocol::MessageType
+protocolMessageType(protocol::TMLedgerData const&)
+{
+    return protocol::mtLEDGER_DATA;
+}
+
 inline protocol::MessageType
 protocolMessageType(protocol::TMReplayDeltaRequest const&)
 {
@@ -432,3 +438,63 @@ invokeProtocolMessage(Buffers const& buffers, Handler& handler, std::size_t& hin
 }
 
 }  // namespace xrpl
+
+namespace protocol {
+
+template <class Hasher>
+void
+hash_append(Hasher& h, TMGetLedger const& msg)
+{
+    using beast::hash_append;
+    using namespace xrpl;
+    hash_append(h, safe_cast<int>(protocolMessageType(msg)));
+    hash_append(h, safe_cast<int>(msg.itype()));
+    if (msg.has_ltype())
+        hash_append(h, safe_cast<int>(msg.ltype()));
+
+    if (msg.has_ledgerhash())
+        hash_append(h, msg.ledgerhash());
+
+    if (msg.has_ledgerseq())
+        hash_append(h, msg.ledgerseq());
+
+    for (auto const& nodeId : msg.nodeids())
+        hash_append(h, nodeId);
+    hash_append(h, msg.nodeids_size());
+
+    // Do NOT include the request cookie. It does not affect the content of the
+    // request, but only where to route the results.
+    // if (msg.has_requestcookie())
+    //    hash_append(h, msg.requestcookie());
+
+    if (msg.has_querytype())
+        hash_append(h, safe_cast<int>(msg.querytype()));
+
+    if (msg.has_querydepth())
+        hash_append(h, msg.querydepth());
+}
+
+template <class Hasher>
+void
+hash_append(Hasher& h, TMLedgerData const& msg)
+{
+    using beast::hash_append;
+    using namespace xrpl;
+    hash_append(h, safe_cast<int>(protocolMessageType(msg)));
+    hash_append(h, msg.ledgerhash());
+    hash_append(h, msg.ledgerseq());
+    hash_append(h, safe_cast<int>(msg.type()));
+    for (auto const& node : msg.nodes())
+    {
+        hash_append(h, node.nodedata());
+        if (node.has_nodeid())
+            hash_append(h, node.nodeid());
+    }
+    hash_append(h, msg.nodes_size());
+    if (msg.has_requestcookie())
+        hash_append(h, msg.requestcookie());
+    if (msg.has_error())
+        hash_append(h, safe_cast<int>(msg.error()));
+}
+
+}  // namespace protocol

src/xrpld/overlay/detail/ProtocolVersion.cpp

@@ -21,7 +21,9 @@ namespace xrpl {
 constexpr ProtocolVersion const supportedProtocolList[]
 {
     {2, 1},
-    {2, 2}
+    {2, 2},
+    // Adds TMLedgerData::responseCookies and directResponse
+    {2, 3}
 };
 // clang-format on