1 files changed, 130 insertions, 0 deletions
diff --git a/grpc/src/core/ext/xds/xds_http_filters.h b/grpc/src/core/ext/xds/xds_http_filters.h
new file mode 100644
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+++ b/grpc/src/core/ext/xds/xds_http_filters.h
@@ -0,0 +1,130 @@
+//
+// Copyright 2021 gRPC 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.
+//
+
+#ifndef GRPC_CORE_EXT_XDS_XDS_HTTP_FILTERS_H
+#define GRPC_CORE_EXT_XDS_XDS_HTTP_FILTERS_H
+
+#include <grpc/support/port_platform.h>
+
+#include <memory>
+#include <set>
+#include <string>
+
+#include "absl/status/statusor.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+#include "google/protobuf/any.upb.h"
+#include "upb/def.h"
+
+#include <grpc/grpc.h>
+
+#include "src/core/lib/channel/channel_stack.h"
+#include "src/core/lib/json/json.h"
+
+namespace grpc_core {
+
+extern const char* kXdsHttpRouterFilterConfigName;
+
+class XdsHttpFilterImpl {
+ public:
+  struct FilterConfig {
+    absl::string_view config_proto_type_name;
+    Json config;
+
+    bool operator==(const FilterConfig& other) const {
+      return config_proto_type_name == other.config_proto_type_name &&
+             config == other.config;
+    }
+    std::string ToString() const {
+      return absl::StrCat("{config_proto_type_name=", config_proto_type_name,
+                          " config=", config.Dump(), "}");
+    }
+  };
+
+  // Service config data for the filter, returned by GenerateServiceConfig().
+  struct ServiceConfigJsonEntry {
+    // The top-level field name in the method config.
+    // Filter implementations should use their primary config proto type
+    // name for this.
+    // The value of this field in the method config will be a JSON array,
+    // which will be populated with the elements returned by each filter
+    // instance.
+    std::string service_config_field_name;
+    // The element to add to the JSON array.
+    std::string element;
+  };
+
+  virtual ~XdsHttpFilterImpl() = default;
+
+  // Loads the proto message into the upb symtab.
+  virtual void PopulateSymtab(upb_symtab* symtab) const = 0;
+
+  // Generates a Config from the xDS filter config proto.
+  // Used for the top-level config in the HCM HTTP filter list.
+  virtual absl::StatusOr<FilterConfig> GenerateFilterConfig(
+      upb_strview serialized_filter_config, upb_arena* arena) const = 0;
+
+  // Generates a Config from the xDS filter config proto.
+  // Used for the typed_per_filter_config override in VirtualHost and Route.
+  virtual absl::StatusOr<FilterConfig> GenerateFilterConfigOverride(
+      upb_strview serialized_filter_config, upb_arena* arena) const = 0;
+
+  // C-core channel filter implementation.
+  virtual const grpc_channel_filter* channel_filter() const = 0;
+
+  // Modifies channel args that may affect service config parsing (not
+  // visible to the channel as a whole).
+  // Takes ownership of args.  Caller takes ownership of return value.
+  virtual grpc_channel_args* ModifyChannelArgs(grpc_channel_args* args) const {
+    return args;
+  }
+
+  // Function to convert the Configs into a JSON string to be added to the
+  // per-method part of the service config.
+  // The hcm_filter_config comes from the HttpConnectionManager config.
+  // The filter_config_override comes from the first of the ClusterWeight,
+  // Route, or VirtualHost entries that it is found in, or null if
+  // there is no override in any of those locations.
+  virtual absl::StatusOr<ServiceConfigJsonEntry> GenerateServiceConfig(
+      const FilterConfig& hcm_filter_config,
+      const FilterConfig* filter_config_override) const = 0;
+
+  // Returns true if the filter is supported on clients; false otherwise
+  virtual bool IsSupportedOnClients() const = 0;
+
+  // Returns true if the filter is supported on servers; false otherwise
+  virtual bool IsSupportedOnServers() const = 0;
+};
+
+class XdsHttpFilterRegistry {
+ public:
+  static void RegisterFilter(
+      std::unique_ptr<XdsHttpFilterImpl> filter,
+      const std::set<absl::string_view>& config_proto_type_names);
+
+  static const XdsHttpFilterImpl* GetFilterForType(
+      absl::string_view proto_type_name);
+
+  static void PopulateSymtab(upb_symtab* symtab);
+
+  // Global init and shutdown.
+  static void Init();
+  static void Shutdown();
+};
+
+}  // namespace grpc_core
+
+#endif /* GRPC_CORE_EXT_XDS_XDS_HTTP_FILTERS_H */