fuzz: added fuzz test for listener filter original_dst (envoyproxy#11847

)

Commit Message: Added fuzz test for listener filter original_dst
Created original_dst_corpus and populated with testcases (different protocol schemes)
Created original_dst_fuzz_test.cc and original_dst_fuzz_test.proto, updated BUILD

increased function and line coverage of original_dst.cc to 100%. fuzzer routes correctly through getOriginalDst() and addressFromSockAddr(), covers all valid cases / lines.
Signed-off-by: Arthur Yan <arthuryan@google.com>

test/extensions/filters/listener/original_dst/BUILD

@@ -1,6 +1,8 @@
 load(
     "//bazel:envoy_build_system.bzl",
+    "envoy_cc_fuzz_test",
     "envoy_package",
+    "envoy_proto_library",
 )
 load(
     "//test/extensions:extensions_build_system.bzl",
@@ -20,3 +22,19 @@ envoy_extension_cc_test(
         "//test/test_common:utility_lib",
     ],
 )
+
+envoy_proto_library(
+    name = "original_dst_fuzz_test_proto",
+    srcs = ["original_dst_fuzz_test.proto"],
+)
+
+envoy_cc_fuzz_test(
+    name = "original_dst_fuzz_test",
+    srcs = ["original_dst_fuzz_test.cc"],
+    corpus = "original_dst_corpus",
+    deps = [
+        ":original_dst_fuzz_test_proto_cc_proto",
+        "//source/extensions/filters/listener/original_dst:original_dst_lib",
+        "//test/mocks/network:network_mocks",
+    ],
+)

test/extensions/filters/listener/original_dst/original_dst_fuzz_test.cc

@@ -0,0 +1,85 @@
+#include "common/network/utility.h"
+
+#include "extensions/filters/listener/original_dst/original_dst.h"
+
+#include "test/extensions/filters/listener/original_dst/original_dst_fuzz_test.pb.validate.h"
+#include "test/fuzz/fuzz_runner.h"
+#include "test/mocks/network/mocks.h"
+
+#include "gmock/gmock.h"
+
+namespace Envoy {
+namespace Extensions {
+namespace ListenerFilters {
+namespace OriginalDst {
+
+class FakeConnectionSocket : public Network::MockConnectionSocket {
+  const Network::Address::InstanceConstSharedPtr& local_address_;
+
+public:
+  ~FakeConnectionSocket() override = default;
+
+  FakeConnectionSocket(const Network::Address::InstanceConstSharedPtr& local_address)
+      : local_address_(local_address) {}
+
+  const Network::Address::InstanceConstSharedPtr& localAddress() const override {
+    return local_address_;
+  }
+
+  Network::Address::Type addressType() const override { return local_address_->type(); }
+
+  absl::optional<Network::Address::IpVersion> ipVersion() const override {
+    if (local_address_->type() != Network::Address::Type::Ip) {
+      return absl::nullopt;
+    }
+
+    return local_address_->ip()->version();
+  }
+
+  Api::SysCallIntResult getSocketOption(int level, int, void* optval, socklen_t*) const override {
+    switch (level) {
+    case SOL_IPV6:
+      static_cast<sockaddr_storage*>(optval)->ss_family = AF_INET6;
+      break;
+    case SOL_IP:
+      static_cast<sockaddr_storage*>(optval)->ss_family = AF_INET;
+      break;
+    default:
+      NOT_REACHED_GCOVR_EXCL_LINE;
+    }
+
+    return Api::SysCallIntResult{0, 0};
+  }
+};
+
+DEFINE_PROTO_FUZZER(
+    const envoy::extensions::filters::listener::original_dst::v3::OriginalDstTestCase& input) {
+
+  try {
+    TestUtility::validate(input);
+  } catch (const ProtoValidationException& e) {
+    ENVOY_LOG_MISC(debug, "ProtoValidationException: {}", e.what());
+    return;
+  }
+
+  NiceMock<Network::MockListenerFilterCallbacks> callbacks;
+  Network::Address::InstanceConstSharedPtr address = nullptr;
+
+  try {
+    address = Network::Utility::resolveUrl(input.address());
+  } catch (const EnvoyException& e) {
+    ENVOY_LOG_MISC(debug, "EnvoyException: {}", e.what());
+    return;
+  }
+
+  FakeConnectionSocket socket(address);
+  ON_CALL(callbacks, socket()).WillByDefault(testing::ReturnRef(socket));
+
+  auto filter = std::make_unique<OriginalDstFilter>();
+  filter->onAccept(callbacks);
+}
+
+} // namespace OriginalDst
+} // namespace ListenerFilters
+} // namespace Extensions
+} // namespace Envoy

test/extensions/filters/listener/original_dst/original_dst_fuzz_test.proto

@@ -0,0 +1,7 @@
+syntax = "proto3";
+
+package envoy.extensions.filters.listener.original_dst.v3;
+
+message OriginalDstTestCase {
+  string address = 2;
+}