[MongoDB Parsing 2/3] Add the types header file for MongoDB Frames (p…

…ixie-io#1703)

Summary: This PR adds the header file the parsing logic uses (currently
in pixie-io#1704 ) to get the MongoDB wire protocol's frame specifications. The
header file currently contains the frame spec for a standard message
header, the spec of a payload of type `OP_MSG` and contains the basic
structure for a `Record`.

Related issues: pixie-io#640

Type of change: /kind feature

Test Plan: Tested the integration of this and the parsing logic through
unit tests.

---------

Signed-off-by: Kartik Pattaswamy <kpattaswamy@pixielabs.ai>
Signed-off-by: Chinmay <chinmaysharma1020@gmail.com>

src/stirling/source_connectors/socket_tracer/protocols/mongodb/BUILD.bazel

@@ -0,0 +1,40 @@
+# Copyright 2018- The Pixie Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+load("//bazel:pl_build_system.bzl", "pl_cc_library")
+
+package(default_visibility = ["//src/stirling:__subpackages__"])
+
+pl_cc_library(
+    name = "cc_library",
+    srcs = glob(
+        [
+            "*.cc",
+        ],
+        exclude = [
+            "**/*_test.cc",
+        ],
+    ),
+    hdrs = glob(
+        [
+            "*.h",
+        ],
+    ),
+    deps = [
+        "//src/stirling/source_connectors/socket_tracer/protocols/common:cc_library",
+        "//src/stirling/utils:cc_library",
+    ],
+)

src/stirling/source_connectors/socket_tracer/protocols/mongodb/types.h

@@ -0,0 +1,148 @@
+/*
+ * Copyright 2018- The Pixie Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "src/stirling/source_connectors/socket_tracer/protocols/common/event_parser.h"
+#include "src/stirling/utils/utils.h"
+
+namespace px {
+namespace stirling {
+namespace protocols {
+namespace mongodb {
+
+enum class Type : int32_t {
+  kOPReply = 1,
+  kOPUpdate = 2001,
+  kOPInsert = 2002,
+  kReserved = 2003,
+  kOPQuery = 2004,
+  kOPGetMore = 2005,
+  kOPDelete = 2006,
+  kOPKillCursors = 2007,
+  kOPCompressed = 2012,
+  kOPMsg = 2013,
+};
+
+constexpr uint8_t kHeaderLength = 16;
+constexpr uint8_t kMessageLengthSize = 4;
+constexpr uint8_t kSectionLengthSize = 4;
+
+struct Section {
+  uint8_t kind = 0;
+  int32_t length = 0;
+  std::vector<std::string> documents;
+};
+
+// Types of OP_MSG requests/responses
+constexpr std::string_view insert = "insert";
+constexpr std::string_view delete_ = "delete";
+constexpr std::string_view update = "update";
+constexpr std::string_view find = "find";
+constexpr std::string_view cursor = "cursor";
+constexpr std::string_view ok = "ok";
+
+constexpr int32_t kMaxBSONOBjSize = 16000000;
+
+/**
+ * MongoDB's Wire Protocol documentation can be found here:
+ * https://www.mongodb.com/docs/manual/reference/mongodb-wire-protocol/#std-label-wire-msg-sections
+ *
+ * The header for a standard message looks like:
+ * -----------------------------------------------------------------------
+ * |  int32 length  | int32 requestID | int32 responseTo|  int32 opCode  |
+ * -----------------------------------------------------------------------
+ *
+ * Documentation regarding OP_MSG frames can be found here:
+ * https://github.com/mongodb/specifications/blob/master/source/message/OP_MSG.rst#sections
+ *
+ * A frame of type OP_MSG looks like:
+ * -----------------------------------------------------------------------
+ * |  int32 length  | int32 requestID | int32 responseTo|  int32 opCode  |
+ * -----------------------------------------------------------------------
+ * | uint32 flagBits|  Sections[] sections  |  optional uint32 checksum  |
+ * -----------------------------------------------------------------------
+ *
+ * There must be only one payload section of kind 0 and any number of payload sections of kind 1.
+ *
+ * A payload section of kind 0 looks like:
+ * -----------------------------------------------------------------------
+ * |  uint8 kind | int32 document payload length |        document       |
+ * -----------------------------------------------------------------------
+ *
+ * A payload section of kind 1 looks like:
+ * -----------------------------------------------------------------------
+ * |  uint8 kind  |               int32 section length                   |
+ * -----------------------------------------------------------------------
+ * |       identifier (command argument that ends with \x00)             |
+ * -----------------------------------------------------------------------
+ * | int32 document payload length |              document               |
+ * -----------------------------------------------------------------------
+ *
+ * There can be 0 or more documents in a section of kind 1 without a separator between them.
+ */
+
+struct Frame : public FrameBase {
+  // Message Header Fields
+  // Length of the mongodb header and the wire protocol data.
+  int32_t length = 0;
+  int32_t request_id = 0;
+  int32_t response_to = 0;
+  int32_t op_code = 0;
+
+  // OP_MSG Fields
+  // Relevant flag bits
+  bool checksum_present = false;
+  bool more_to_come = false;
+  bool exhaust_allowed = false;
+  std::vector<Section> sections;
+  std::string op_msg_type;
+  uint32_t checksum = 0;
+
+  bool consumed = false;
+  size_t ByteSize() const override { return sizeof(Frame); }
+
+  std::string ToString() const override {
+    return absl::Substitute(
+        "MongoDB message [length=$0 requestID=$1 responseTo=$2 opCode=$3 checksum=$4]", length,
+        request_id, response_to, op_code, checksum);
+  }
+};
+
+struct Record {
+  Frame req;
+  Frame resp;
+
+  std::string ToString() const {
+    return absl::Substitute("req=[$0] resp=[$1]", req.ToString(), resp.ToString());
+  }
+};
+
+struct ProtocolTraits : public BaseProtocolTraits<Record> {
+  using frame_type = Frame;
+  using record_type = Record;
+  using state_type = NoState;
+};
+
+}  // namespace mongodb
+}  // namespace protocols
+}  // namespace stirling
+}  // namespace px