cors: remove unnecessary code (#37274)

Commit Message:
Additional Description:
Risk Level:
Testing:
Docs Changes:
Release Notes:
Platform Specific Features:
[Optional Runtime guard:]
[Optional Fixes #Issue]
[Optional Fixes commit #PR or SHA]
[Optional Deprecated:]
[Optional [API
Considerations](https://github.com/envoyproxy/envoy/blob/main/api/review_checklist.md):]

Signed-off-by: wangbaiping(wbpcode) <wangbaiping@bytedance.com>

source/extensions/filters/http/cors/BUILD

@@ -25,6 +25,7 @@ envoy_cc_library(
         "//source/common/http:header_map_lib",
         "//source/common/http:headers_lib",
         "//source/common/http:utility_lib",
+        "//source/extensions/filters/http/common:pass_through_filter_lib",
         "@com_google_absl//absl/container:inlined_vector",
     ],
 )

source/extensions/filters/http/cors/cors_filter.cc

@@ -206,10 +206,6 @@ Http::FilterHeadersStatus CorsFilter::encodeHeaders(Http::ResponseHeaderMap& hea
   return Http::FilterHeadersStatus::Continue;
 }
 
-void CorsFilter::setDecoderFilterCallbacks(Http::StreamDecoderFilterCallbacks& callbacks) {
-  decoder_callbacks_ = &callbacks;
-}
-
 bool CorsFilter::isOriginAllowed(const Http::HeaderString& origin) {
   for (const auto& allow_origin : allowOrigins()) {
     if (allow_origin->match("*") || allow_origin->match(origin.getStringView())) {

source/extensions/filters/http/cors/cors_filter.h

@@ -5,6 +5,7 @@
 #include "envoy/stats/stats_macros.h"
 
 #include "source/common/buffer/buffer_impl.h"
+#include "source/extensions/filters/http/common/pass_through_filter.h"
 
 #include "absl/container/inlined_vector.h"
 
@@ -44,44 +45,19 @@ class CorsFilterConfig {
 };
 using CorsFilterConfigSharedPtr = std::shared_ptr<CorsFilterConfig>;
 
-class CorsFilter : public Http::StreamFilter {
+class CorsFilter : public Http::PassThroughFilter {
 public:
   CorsFilter(CorsFilterConfigSharedPtr config);
 
   void initializeCorsPolicies();
 
-  // Http::StreamFilterBase
-  void onDestroy() override {}
-
   // Http::StreamDecoderFilter
   Http::FilterHeadersStatus decodeHeaders(Http::RequestHeaderMap& headers,
                                           bool end_stream) override;
-  Http::FilterDataStatus decodeData(Buffer::Instance&, bool) override {
-    return Http::FilterDataStatus::Continue;
-  };
-  Http::FilterTrailersStatus decodeTrailers(Http::RequestTrailerMap&) override {
-    return Http::FilterTrailersStatus::Continue;
-  };
-  void setDecoderFilterCallbacks(Http::StreamDecoderFilterCallbacks& callbacks) override;
 
   // Http::StreamEncoderFilter
-  Http::Filter1xxHeadersStatus encode1xxHeaders(Http::ResponseHeaderMap&) override {
-    return Http::Filter1xxHeadersStatus::Continue;
-  }
   Http::FilterHeadersStatus encodeHeaders(Http::ResponseHeaderMap& headers,
                                           bool end_stream) override;
-  Http::FilterDataStatus encodeData(Buffer::Instance&, bool) override {
-    return Http::FilterDataStatus::Continue;
-  };
-  Http::FilterTrailersStatus encodeTrailers(Http::ResponseTrailerMap&) override {
-    return Http::FilterTrailersStatus::Continue;
-  };
-  Http::FilterMetadataStatus encodeMetadata(Http::MetadataMap&) override {
-    return Http::FilterMetadataStatus::Continue;
-  }
-  void setEncoderFilterCallbacks(Http::StreamEncoderFilterCallbacks& callbacks) override {
-    encoder_callbacks_ = &callbacks;
-  };
 
   const auto& policiesForTest() const { return policies_; }
 
@@ -100,8 +76,6 @@ class CorsFilter : public Http::StreamFilter {
   bool isOriginAllowed(const Http::HeaderString& origin);
   bool forwardNotMatchingPreflights();
 
-  Http::StreamDecoderFilterCallbacks* decoder_callbacks_{};
-  Http::StreamEncoderFilterCallbacks* encoder_callbacks_{};
   absl::InlinedVector<std::reference_wrapper<const Envoy::Router::CorsPolicy>, 4> policies_;
   bool is_cors_request_{};
   std::string latched_origin_;