SERVER-26966 Remove dead legacy find/getMore up and downconversion

9 files changed, 76 insertions, 465 deletions

diff --git a/jstests/multiVersion/skip_version_upgrade.js b/jstests/multiVersion/skip_version_upgrade.js
new file mode 100644
index 00000000000..1c40bdda9e2
--- /dev/null
+++ b/jstests/multiVersion/skip_version_upgrade.js
@@ -0,0 +1,62 @@
+/**
+ * Tests that a mongod on the latest version will refuse to sync from a 3.0 node.
+ */
+(function() {
+    "use strict";
+
+    //
+    // Test that the latest version cannot replicate from a 3.0 node.
+    //
+    var rst = new ReplSetTest({nodes: [{binVersion: "3.0"}, {binVersion: "latest"}]});
+    rst.startSet();
+
+    // Make sure the 3.0 node will be elected.
+    var replSetConfig = rst.getReplSetConfig();
+    replSetConfig.members[0].priority = 1;
+    replSetConfig.members[1].priority = 0;
+    var threeZeroAdminDB = rst.nodes[0].getDB("admin");
+    var latestAdminDB = rst.nodes[1].getDB("admin");
+    assert.commandWorked(threeZeroAdminDB.runCommand({replSetInitiate: replSetConfig}));
+    assert.soon(
+        function() {
+            try {
+                latestAdminDB.runCommand({ping: 1});
+            } catch (e) {
+                return true;
+            }
+            return false;
+        },
+        "Expected latest node to terminate when communicating to node which does not support find" +
+            " commands, but it didn't.");
+
+    rst.stopSet(undefined, undefined, {allowedExitCodes: [MongoRunner.EXIT_ABRUPT]});
+
+    //
+    // Test that a 3.0 node cannot replicate off the latest node if that node is launched with the
+    // default featureCompatibilityVersion.
+    //
+    rst = new ReplSetTest({nodes: [{binVersion: "latest"}]});
+    rst.startSet();
+
+    // Configure the set to use protocol version 0 so that a 3.0 node can participate.
+    replSetConfig = rst.getReplSetConfig();
+    replSetConfig.protocolVersion = 0;
+    rst.initiate(replSetConfig);
+
+    // Add the node, but don't wait for it to start up, since we don't expect it to ever get to
+    // state SECONDARY.
+    rst.add({binVersion: "3.0"});
+
+    // Rig the election so that the first node running latest version remains the primary after the
+    // 3.0 secondary is added to the replica set.
+    replSetConfig = rst.getReplSetConfig();
+    replSetConfig.version = 2;
+    replSetConfig.members[1].priority = 0;
+
+    assert.commandWorked(rst.getPrimary().adminCommand({replSetReconfig: replSetConfig}));
+
+    // Verify that the 3.0 node cannot participate in the set. It should eventually exceed the
+    // maximum number of retries for initial sync and fail.
+    rst.waitForState(rst.nodes, [ReplSetTest.State.SECONDARY, ReplSetTest.State.DOWN]);
+    rst.stopSet(undefined, undefined, {allowedExitCodes: [MongoRunner.EXIT_ABRUPT]});
+})();
diff --git a/src/mongo/executor/SConscript b/src/mongo/executor/SConscript
index 25089c56334..000d751ecde 100644
--- a/src/mongo/executor/SConscript
+++ b/src/mongo/executor/SConscript
@@ -142,6 +142,7 @@ env.Library(
     LIBDEPS=[
         '$BUILD_DIR/mongo/base',
         '$BUILD_DIR/mongo/base/system_error',
+        '$BUILD_DIR/mongo/client/client_query',
         '$BUILD_DIR/mongo/db/auth/authcommon',
         '$BUILD_DIR/mongo/db/commands/test_commands_enabled',
         '$BUILD_DIR/mongo/db/wire_version',
@@ -151,7 +152,6 @@ env.Library(
         'async_stream',
         'async_timer_asio',
         'connection_pool',
-        'downconvert_find_and_getmore_commands',
         'network_interface',
         'task_executor_interface',
     ])
@@ -317,24 +317,6 @@ env.CppUnitTest(
 )
 
 env.Library(
-    target='downconvert_find_and_getmore_commands',
-    source=[
-        'downconvert_find_and_getmore_commands.cpp',
-    ],
-    LIBDEPS=[
-        'remote_command',
-        '$BUILD_DIR/mongo/base',
-        '$BUILD_DIR/mongo/client/client_query',
-        '$BUILD_DIR/mongo/db/query/command_request_response',
-        '$BUILD_DIR/mongo/db/query/command_request_response',
-        '$BUILD_DIR/mongo/db/query/query_request',
-        '$BUILD_DIR/mongo/rpc/protocol',
-        '$BUILD_DIR/mongo/rpc/metadata',
-        '$BUILD_DIR/mongo/util/net/network',
-    ],
-)
-
-env.Library(
     target='task_executor_pool',
     source=[
         'task_executor_pool.cpp',
diff --git a/src/mongo/executor/connection_pool_asio.cpp b/src/mongo/executor/connection_pool_asio.cpp
index 0788a67d7f6..b5f4f803793 100644
--- a/src/mongo/executor/connection_pool_asio.cpp
+++ b/src/mongo/executor/connection_pool_asio.cpp
@@ -272,9 +272,7 @@ void ASIOConnection::refresh(Milliseconds timeout, RefreshCallback cb) {
         setTimeout(timeout, [this] { _impl->connection().stream().cancel(); });
 
         // Our pings are isMaster's
-        auto beginStatus = op->beginCommand(makeIsMasterRequest(this),
-                                            NetworkInterfaceASIO::AsyncCommand::CommandType::kRPC,
-                                            _hostAndPort);
+        auto beginStatus = op->beginCommand(makeIsMasterRequest(this), _hostAndPort);
         if (!beginStatus.isOK()) {
             auto cb = std::move(_refreshCallback);
             cb(this, beginStatus);
diff --git a/src/mongo/executor/downconvert_find_and_getmore_commands.cpp b/src/mongo/executor/downconvert_find_and_getmore_commands.cpp
deleted file mode 100644
index 7d1aa15c817..00000000000
--- a/src/mongo/executor/downconvert_find_and_getmore_commands.cpp
+++ /dev/null
@@ -1,279 +0,0 @@
-/**
- *    Copyright (C) 2015 MongoDB Inc.
- *
- *    This program is free software: you can redistribute it and/or  modify
- *    it under the terms of the GNU Affero General Public License, version 3,
- *    as published by the Free Software Foundation.
- *
- *    This program is distributed in the hope that it will be useful,
- *    but WITHOUT ANY WARRANTY; without even the implied warranty of
- *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *    GNU Affero General Public License for more details.
- *
- *    You should have received a copy of the GNU Affero General Public License
- *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the GNU Affero General Public License in all respects for
- *    all of the code used other than as permitted herein. If you modify file(s)
- *    with this exception, you may extend this exception to your version of the
- *    file(s), but you are not obligated to do so. If you do not wish to do so,
- *    delete this exception statement from your version. If you delete this
- *    exception statement from all source files in the program, then also delete
- *    it in the license file.
- */
-
-#include "mongo/platform/basic.h"
-
-#include "mongo/executor/downconvert_find_and_getmore_commands.h"
-
-#include <memory>
-#include <string>
-#include <tuple>
-
-#include "mongo/base/data_range_cursor.h"
-#include "mongo/base/data_type_validated.h"
-#include "mongo/base/status_with.h"
-#include "mongo/client/constants.h"
-#include "mongo/client/dbclientinterface.h"
-#include "mongo/db/cursor_id.h"
-#include "mongo/db/namespace_string.h"
-#include "mongo/db/query/cursor_response.h"
-#include "mongo/db/query/getmore_request.h"
-#include "mongo/executor/remote_command_request.h"
-#include "mongo/executor/remote_command_response.h"
-#include "mongo/rpc/get_status_from_command_result.h"
-#include "mongo/rpc/metadata/server_selection_metadata.h"
-#include "mongo/rpc/object_check.h"
-#include "mongo/util/assert_util.h"
-#include "mongo/util/net/message.h"
-
-namespace mongo {
-namespace executor {
-
-namespace {
-
-StatusWith<std::tuple<CursorId, BSONArray>> getBatchFromReply(std::int32_t requestId,
-                                                              const Message& response) {
-    auto header = response.header();
-    if (header.getNetworkOp() != mongo::opReply) {
-        return {ErrorCodes::ProtocolError,
-                str::stream() << "Expected to be decoding an OP_REPLY but got "
-                              << mongo::networkOpToString(header.getNetworkOp())};
-    }
-
-    if (header.getResponseToMsgId() != requestId) {
-        return {ErrorCodes::ProtocolError,
-                str::stream() << "responseTo field of OP_REPLY header with value '"
-                              << header.getResponseToMsgId()
-                              << "' does not match requestId '"
-                              << requestId
-                              << "'"};
-    }
-
-    if ((header.dataLen() < 0) ||
-        (static_cast<std::size_t>(header.dataLen()) > mongo::MaxMessageSizeBytes)) {
-        return {ErrorCodes::InvalidLength,
-                str::stream() << "Received message has invalid length field with value "
-                              << header.dataLen()};
-    }
-
-    QueryResult::View qr = response.header().view2ptr();
-
-    auto resultFlags = qr.getResultFlags();
-
-    if (resultFlags & ResultFlag_CursorNotFound) {
-        return {ErrorCodes::CursorNotFound,
-                str::stream() << "Cursor with id '" << qr.getCursorId() << "' not found"};
-    }
-
-    // Use CDRC directly instead of DocumentRange as DocumentRange has a throwing API.
-    ConstDataRangeCursor cdrc{qr.data(), qr.data() + header.dataLen()};
-
-    if (resultFlags & ResultFlag_ErrSet) {
-        if (qr.getNReturned() != 1) {
-            return {ErrorCodes::BadValue,
-                    str::stream() << "ResultFlag_ErrSet flag set on reply, but nReturned was '"
-                                  << qr.getNReturned()
-                                  << "' - expected 1"};
-        }
-        // Convert error document to a Status.
-        // Will throw if first document is invalid BSON.
-        auto first = cdrc.readAndAdvance<Validated<BSONObj>>();
-        if (!first.isOK()) {
-            return first.getStatus();
-        }
-
-        // Convert error document to a status.
-        return getStatusFromCommandResult(first.getValue());
-    }
-
-    Validated<BSONObj> nextObj;
-    BSONArrayBuilder batch;
-    while (!cdrc.empty() && batch.arrSize() < qr.getNReturned()) {
-        auto readStatus = cdrc.readAndAdvance(&nextObj);
-        if (!readStatus.isOK()) {
-            return readStatus;
-        }
-        batch.append(nextObj.val);
-    }
-    if (qr.getNReturned() != batch.arrSize()) {
-        return {ErrorCodes::InvalidLength,
-                str::stream() << "Count of documents in OP_REPLY message (" << batch.arrSize()
-                              << ") did not match the value specified in the nReturned field ("
-                              << qr.getNReturned()
-                              << ")"};
-    }
-
-    return {std::make_tuple(qr.getCursorId(), batch.arr())};
-}
-
-}  // namespace
-
-StatusWith<Message> downconvertFindCommandRequest(const RemoteCommandRequest& request) {
-    const auto& cmdObj = request.cmdObj;
-    const NamespaceString nss(request.dbname, cmdObj.firstElement().String());
-    if (!nss.isValid()) {
-        return {ErrorCodes::InvalidNamespace,
-                str::stream() << "Invalid collection name: " << nss.ns()};
-    }
-
-    const std::string& ns = nss.ns();
-
-    // It is a little heavy handed to use QueryRequest to convert the command object to
-    // query() arguments but we get validation and consistent behavior with the find
-    // command implementation on the remote server.
-    auto qrStatus = QueryRequest::makeFromFindCommand(nss, cmdObj, false);
-    if (!qrStatus.isOK()) {
-        return qrStatus.getStatus();
-    }
-
-    auto qr = std::move(qrStatus.getValue());
-
-    // We are downconverting a find command, and find command can only have ntoreturn
-    // if it was generated by mongos.
-    invariant(!qr->getNToReturn());
-    Query query(qr->getFilter());
-    if (!qr->getSort().isEmpty()) {
-        query.sort(qr->getSort());
-    }
-    if (!qr->getHint().isEmpty()) {
-        query.hint(qr->getHint());
-    }
-    if (!qr->getMin().isEmpty()) {
-        query.minKey(qr->getMin());
-    }
-    if (!qr->getMax().isEmpty()) {
-        query.minKey(qr->getMax());
-    }
-    if (qr->isExplain()) {
-        query.explain();
-    }
-    if (qr->isSnapshot()) {
-        query.snapshot();
-    }
-
-    const int nToReturn = qr->getLimit().value_or(0) * -1;
-    const int nToSkip = qr->getSkip().value_or(0);
-    const BSONObj* fieldsToReturn = &qr->getProj();
-    int queryOptions = qr->getOptions();  // non-const so we can set slaveOk if we need to
-    const int batchSize = qr->getBatchSize().value_or(0);
-
-    const int nextBatchSize = [batchSize, nToReturn]() {
-        if (nToReturn == 0)
-            return batchSize;
-        if (batchSize == 0)
-            return nToReturn;
-        return batchSize < nToReturn ? batchSize : nToReturn;
-    }();
-
-    // We can't downconvert all metadata, since we aren't sending a command, but we do need to
-    // downconvert $secondaryOk to the slaveOK bit.
-    auto ssm = rpc::ServerSelectionMetadata::readFromMetadata(
-        request.metadata.getField(rpc::ServerSelectionMetadata::fieldName()));
-    if (!ssm.isOK()) {
-        return ssm.getStatus();
-    }
-    if (ssm.getValue().isSecondaryOk()) {
-        queryOptions |= mongo::QueryOption_SlaveOk;
-    }
-
-    Message message;
-    assembleQueryRequest(
-        ns, query.obj, nextBatchSize, nToSkip, fieldsToReturn, queryOptions, message);
-
-    return {std::move(message)};
-}
-
-RemoteCommandResponse upconvertLegacyQueryResponse(std::int32_t requestId,
-                                                   StringData cursorNamespace,
-                                                   const Message& response) {
-    auto swBatch = getBatchFromReply(requestId, response);
-    if (!swBatch.isOK()) {
-        return {swBatch.getStatus()};
-    }
-
-    BSONArray batch;
-    CursorId cursorId;
-    std::tie(cursorId, batch) = std::move(swBatch.getValue());
-
-    BSONObjBuilder result;
-    appendCursorResponseObject(cursorId, cursorNamespace, std::move(batch), &result);
-    // Using Command::appendCommandStatus would create a circular dep, so it's simpler to just do
-    // this.
-    result.append("ok", 1.0);
-
-    RemoteCommandResponse upconvertedResponse;
-    upconvertedResponse.data = result.obj();
-
-    return upconvertedResponse;
-}
-
-StatusWith<Message> downconvertGetMoreCommandRequest(const RemoteCommandRequest& request) {
-    auto swGetMoreRequest = GetMoreRequest::parseFromBSON(request.dbname, request.cmdObj);
-    if (!swGetMoreRequest.isOK()) {
-        return swGetMoreRequest.getStatus();
-    }
-
-    auto getMoreRequest = std::move(swGetMoreRequest.getValue());
-
-    BufBuilder b;
-    b.appendNum(std::int32_t{0});  // reserved bits
-    b.appendStr(getMoreRequest.nss.ns());
-    // Without this static cast, we will append batchSize as an int64 and get an invalid message.
-    b.appendNum(static_cast<std::int32_t>(getMoreRequest.batchSize.value_or(0)));
-    b.appendNum(getMoreRequest.cursorid);
-    Message m;
-    m.setData(dbGetMore, b.buf(), b.len());
-
-    return {std::move(m)};
-}
-
-RemoteCommandResponse upconvertLegacyGetMoreResponse(std::int32_t requestId,
-                                                     StringData cursorNamespace,
-                                                     const Message& response) {
-    auto swBatch = getBatchFromReply(requestId, response);
-    if (!swBatch.isOK()) {
-        return {swBatch.getStatus()};
-    }
-
-    BSONArray batch;
-    CursorId cursorId;
-
-    std::tie(cursorId, batch) = std::move(swBatch.getValue());
-
-    BSONObjBuilder result;
-    appendGetMoreResponseObject(cursorId, cursorNamespace, std::move(batch), &result);
-    result.append("ok", 1.0);
-
-    RemoteCommandResponse resp;
-    resp.data = result.obj();
-
-    return resp;
-}
-
-}  // namespace mongo
-}  // namespace executor
diff --git a/src/mongo/executor/downconvert_find_and_getmore_commands.h b/src/mongo/executor/downconvert_find_and_getmore_commands.h
deleted file mode 100644
index dd991358e78..00000000000
--- a/src/mongo/executor/downconvert_find_and_getmore_commands.h
+++ /dev/null
@@ -1,81 +0,0 @@
-/**
- *    Copyright (C) 2015 MongoDB Inc.
- *
- *    This program is free software: you can redistribute it and/or  modify
- *    it under the terms of the GNU Affero General Public License, version 3,
- *    as published by the Free Software Foundation.
- *
- *    This program is distributed in the hope that it will be useful,
- *    but WITHOUT ANY WARRANTY; without even the implied warranty of
- *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *    GNU Affero General Public License for more details.
- *
- *    You should have received a copy of the GNU Affero General Public License
- *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- *    As a special exception, the copyright holders give permission to link the
- *    code of portions of this program with the OpenSSL library under certain
- *    conditions as described in each individual source file and distribute
- *    linked combinations including the program with the OpenSSL library. You
- *    must comply with the GNU Affero General Public License in all respects for
- *    all of the code used other than as permitted herein. If you modify file(s)
- *    with this exception, you may extend this exception to your version of the
- *    file(s), but you are not obligated to do so. If you do not wish to do so,
- *    delete this exception statement from your version. If you delete this
- *    exception statement from all source files in the program, then also delete
- *    it in the license file.
- */
-
-#include <cstdint>
-#include <memory>
-
-namespace mongo {
-
-class Message;
-
-template <typename T>
-class StatusWith;
-
-class StringData;
-class NamespaceString;
-
-namespace executor {
-struct RemoteCommandRequest;
-struct RemoteCommandResponse;
-
-/**
- * Downconverts a find command request to the legacy (non-command) OP_QUERY format. The returned
- * message is formed, with the exception of the messageId header field, which must be set by
- * the caller before sending the message over the wire. Note that our legacy socket code sets the
- * messageId in MessagingPort::say().
- */
-StatusWith<Message> downconvertFindCommandRequest(const RemoteCommandRequest& request);
-
-/**
- * Upconverts the OP_REPLY received in response to a legacy OP_QUERY to a semantically equivalent
- * find command response. The 'requestId' parameter is the messageId of the original OP_QUERY, and
- * the 'cursorNamespace' is the full namespace of the collection the query ran on.
- */
-RemoteCommandResponse upconvertLegacyQueryResponse(std::int32_t requestId,
-                                                   StringData cursorNamespace,
-                                                   const Message& response);
-
-/**
- * Downconverts a getMore command request to the legacy OP_GET_MORE format. The returned message
- * is fully formed, with the exception of the messageId header field, which must be set by the
- * the caller before sending the message over the wire. Note that our legacy socket code sets the
- * messageId in MessagingPort::say().
- */
-StatusWith<Message> downconvertGetMoreCommandRequest(const RemoteCommandRequest& request);
-
-/**
- * Upconverts the OP_REPLY received in response to a legacy OP_GET_MORE to a semantically equivalent
- * getMore command response. The 'requestId' parameter is the messageId of the original OP_GET_MORE,
- * and the 'curesorNamespace' is the full namespace of the collection the original query ran on.
- */
-RemoteCommandResponse upconvertLegacyGetMoreResponse(std::int32_t requestId,
-                                                     StringData cursorNamespace,
-                                                     const Message& response);
-
-}  // namespace mongo
-}  // namespace executor
diff --git a/src/mongo/executor/network_interface_asio.h b/src/mongo/executor/network_interface_asio.h
index 3d7aa2f1445..3fcd2e42771 100644
--- a/src/mongo/executor/network_interface_asio.h
+++ b/src/mongo/executor/network_interface_asio.h
@@ -183,28 +183,7 @@ private:
      */
     class AsyncCommand {
     public:
-        /**
-         * Describes the variant of AsyncCommand this object represents.
-         */
-        enum class CommandType {
-            /**
-             * An ordinary command of an unspecified Protocol.
-             */
-            kRPC,
-
-            /**
-             * A 'find' command that has been downconverted to an OP_QUERY.
-             */
-            kDownConvertedFind,
-
-            /**
-             * A 'getMore' command that has been downconverted to an OP_GET_MORE.
-             */
-            kDownConvertedGetMore,
-        };
-
         AsyncCommand(AsyncConnection* conn,
-                     CommandType type,
                      Message&& command,
                      Date_t now,
                      const HostAndPort& target);
@@ -223,8 +202,6 @@ private:
     private:
         NetworkInterfaceASIO::AsyncConnection* const _conn;
 
-        const CommandType _type;
-
         Message _toSend;
         Message _toRecv;
 
@@ -305,9 +282,7 @@ private:
 
         // This form of beginCommand takes a raw message. It is needed if the caller
         // has to form the command manually (e.g. to use a specific requestBuilder).
-        Status beginCommand(Message&& newCommand,
-                            AsyncCommand::CommandType,
-                            const HostAndPort& target);
+        Status beginCommand(Message&& newCommand, const HostAndPort& target);
 
         AsyncCommand* command();
 
diff --git a/src/mongo/executor/network_interface_asio_auth.cpp b/src/mongo/executor/network_interface_asio_auth.cpp
index 921262f2875..84600d6bde6 100644
--- a/src/mongo/executor/network_interface_asio_auth.cpp
+++ b/src/mongo/executor/network_interface_asio_auth.cpp
@@ -88,8 +88,7 @@ void NetworkInterfaceASIO::_runIsMaster(AsyncOp* op) {
     requestBuilder.setMetadata(rpc::makeEmptyMetadata());
 
     // Set current command to ismaster request and run
-    auto beginStatus = op->beginCommand(
-        requestBuilder.done(), AsyncCommand::CommandType::kRPC, op->request().target);
+    auto beginStatus = op->beginCommand(requestBuilder.done(), op->request().target);
     if (!beginStatus.isOK()) {
         return _completeOperation(op, beginStatus);
     }
diff --git a/src/mongo/executor/network_interface_asio_command.cpp b/src/mongo/executor/network_interface_asio_command.cpp
index 4c981ff41e0..036b2954ee0 100644
--- a/src/mongo/executor/network_interface_asio_command.cpp
+++ b/src/mongo/executor/network_interface_asio_command.cpp
@@ -40,7 +40,6 @@
 #include "mongo/executor/async_stream_interface.h"
 #include "mongo/executor/async_stream_interface.h"
 #include "mongo/executor/connection_pool_asio.h"
-#include "mongo/executor/downconvert_find_and_getmore_commands.h"
 #include "mongo/rpc/factory.h"
 #include "mongo/rpc/metadata/metadata_hook.h"
 #include "mongo/rpc/protocol.h"
@@ -177,11 +176,10 @@ ResponseStatus decodeRPC(Message* received,
 }  // namespace
 
 NetworkInterfaceASIO::AsyncCommand::AsyncCommand(AsyncConnection* conn,
-                                                 CommandType type,
                                                  Message&& command,
                                                  Date_t now,
                                                  const HostAndPort& target)
-    : _conn(conn), _type(type), _toSend(std::move(command)), _start(now), _target(target) {
+    : _conn(conn), _toSend(std::move(command)), _start(now), _target(target) {
     _toSend.header().setResponseToMsgId(0);
 }
 
@@ -214,23 +212,10 @@ ResponseStatus NetworkInterfaceASIO::AsyncCommand::response(AsyncOp* op,
         received = std::move(swm.getValue());
     }
 
-    switch (_type) {
-        case CommandType::kRPC: {
-            auto rs = decodeRPC(&received, protocol, now - _start, _target, metadataHook);
-            if (rs.isOK())
-                op->setResponseMetadata(rs.metadata);
-            return rs;
-        }
-        case CommandType::kDownConvertedFind: {
-            auto ns = DbMessage(_toSend).getns();
-            return upconvertLegacyQueryResponse(_toSend.header().getId(), ns, received);
-        }
-        case CommandType::kDownConvertedGetMore: {
-            auto ns = DbMessage(_toSend).getns();
-            return upconvertLegacyGetMoreResponse(_toSend.header().getId(), ns, received);
-        }
-    }
-    MONGO_UNREACHABLE;
+    auto rs = decodeRPC(&received, protocol, now - _start, _target, metadataHook);
+    if (rs.isOK())
+        op->setResponseMetadata(rs.metadata);
+    return rs;
 }
 
 void NetworkInterfaceASIO::_startCommand(AsyncOp* op) {
diff --git a/src/mongo/executor/network_interface_asio_operation.cpp b/src/mongo/executor/network_interface_asio_operation.cpp
index d595df6c6e8..f56c3be6e16 100644
--- a/src/mongo/executor/network_interface_asio_operation.cpp
+++ b/src/mongo/executor/network_interface_asio_operation.cpp
@@ -37,7 +37,6 @@
 #include "mongo/db/query/query_request.h"
 #include "mongo/executor/async_stream_interface.h"
 #include "mongo/executor/connection_pool_asio.h"
-#include "mongo/executor/downconvert_find_and_getmore_commands.h"
 #include "mongo/executor/network_interface_asio.h"
 #include "mongo/rpc/factory.h"
 #include "mongo/rpc/metadata/metadata_hook.h"
@@ -164,7 +163,6 @@ void NetworkInterfaceASIO::AsyncOp::setConnection(AsyncConnection&& conn) {
 }
 
 Status NetworkInterfaceASIO::AsyncOp::beginCommand(Message&& newCommand,
-                                                   AsyncCommand::CommandType type,
                                                    const HostAndPort& target) {
     // NOTE: We operate based on the assumption that AsyncOp's
     // AsyncConnection does not change over its lifetime.
@@ -176,44 +174,16 @@ Status NetworkInterfaceASIO::AsyncOp::beginCommand(Message&& newCommand,
         return swm.getStatus();
 
     // Construct a new AsyncCommand object for each command.
-    _command.emplace(_connection.get_ptr(), type, std::move(swm.getValue()), _owner->now(), target);
+    _command.emplace(_connection.get_ptr(), std::move(swm.getValue()), _owner->now(), target);
     return Status::OK();
 }
 
 Status NetworkInterfaceASIO::AsyncOp::beginCommand(const RemoteCommandRequest& request) {
-    // Check if we need to downconvert find or getMore commands.
-    StringData commandName = request.cmdObj.firstElement().fieldNameStringData();
-    const auto isFindCmd = commandName == QueryRequest::kFindCommandName;
-    const auto isGetMoreCmd = commandName == GetMoreRequest::kGetMoreCommandName;
-    const auto isFindOrGetMoreCmd = isFindCmd || isGetMoreCmd;
-
-    // If we aren't sending a find or getMore, or the server supports OP_COMMAND we don't have
-    // to worry about downconversion.
-    if (!isFindOrGetMoreCmd || connection().serverProtocols() == rpc::supports::kAll) {
-        auto newCommand = messageFromRequest(request, operationProtocol());
-        if (!newCommand.isOK()) {
-            return newCommand.getStatus();
-        }
-        return beginCommand(
-            std::move(newCommand.getValue()), AsyncCommand::CommandType::kRPC, request.target);
-    } else if (isFindCmd) {
-        auto downconvertedFind = downconvertFindCommandRequest(request);
-        if (!downconvertedFind.isOK()) {
-            return downconvertedFind.getStatus();
-        }
-        return beginCommand(std::move(downconvertedFind.getValue()),
-                            AsyncCommand::CommandType::kDownConvertedFind,
-                            request.target);
-    } else {
-        MONGO_ASYNC_OP_INVARIANT(isGetMoreCmd, "Expected a GetMore command");
-        auto downconvertedGetMore = downconvertGetMoreCommandRequest(request);
-        if (!downconvertedGetMore.isOK()) {
-            return downconvertedGetMore.getStatus();
-        }
-        return beginCommand(std::move(downconvertedGetMore.getValue()),
-                            AsyncCommand::CommandType::kDownConvertedGetMore,
-                            request.target);
+    auto newCommand = messageFromRequest(request, operationProtocol());
+    if (!newCommand.isOK()) {
+        return newCommand.getStatus();
     }
+    return beginCommand(std::move(newCommand.getValue()), request.target);
 }
 
 NetworkInterfaceASIO::AsyncCommand* NetworkInterfaceASIO::AsyncOp::command() {