ext_proc: send attributes

api/envoy/extensions/filters/http/ext_proc/v3/ext_proc.proto

@@ -125,15 +125,13 @@ message ExternalProcessor {
   // for a reply.
   bool async_mode = 4;
 
-  // [#not-implemented-hide:]
   // Envoy provides a number of :ref:`attributes <arch_overview_attributes>`
   // for expressive policies. Each attribute name provided in this field will be
   // matched against that list and populated in the request_headers message.
   // See the :ref:`attribute documentation <arch_overview_request_attributes>`
   // for the list of supported attributes and their types.
   repeated string request_attributes = 5;
 
-  // [#not-implemented-hide:]
   // Envoy provides a number of :ref:`attributes <arch_overview_attributes>`
   // for expressive policies. Each attribute name provided in this field will be
   // matched against that list and populated in the response_headers message.
@@ -257,12 +255,10 @@ message ExtProcOverrides {
   // Set a different asynchronous processing option than the default.
   bool async_mode = 2;
 
-  // [#not-implemented-hide:]
   // Set different optional attributes than the default setting of the
   // ``request_attributes`` field.
   repeated string request_attributes = 3;
 
-  // [#not-implemented-hide:]
   // Set different optional properties than the default setting of the
   // ``response_attributes`` field.
   repeated string response_attributes = 4;

changelogs/current.yaml

@@ -203,5 +203,12 @@ new_features:
 - area: tracing
   change: |
     Provide initial span attributes to a sampler used in the OpenTelemetry tracer.
+- area: ext_proc
+  change: |
+    implemented
+    :ref:`request_attributes <envoy_v3_api_field_extensions.filters.http.ext_proc.v3.ExternalProcessor.request_attributes>`
+    and
+    :ref:`response_attributes <envoy_v3_api_field_extensions.filters.http.ext_proc.v3.ExternalProcessor.response_attributes>`
+    config APIs to enable sending and receiving attributes from/to the external processing server.
 
 deprecated:

source/extensions/filters/http/ext_proc/BUILD

@@ -19,6 +19,12 @@ envoy_cc_library(
         "ext_proc.h",
         "processor_state.h",
     ],
+    copts = select({
+        "//bazel:windows_x86_64": [],
+        "//conditions:default": [
+            "-DUSE_CEL_PARSER",
+        ],
+    }),
     deps = [
         ":client_interface",
         ":mutation_utils_lib",
@@ -29,24 +35,41 @@ envoy_cc_library(
         "//source/common/buffer:buffer_lib",
         "//source/common/protobuf",
         "//source/common/runtime:runtime_features_lib",
+        "//source/extensions/filters/common/expr:evaluator_lib",
         "//source/extensions/filters/common/mutation_rules:mutation_rules_lib",
         "//source/extensions/filters/http/common:pass_through_filter_lib",
         "@com_google_absl//absl/status",
         "@com_google_absl//absl/strings:str_format",
+        "@com_google_cel_cpp//eval/public:builtin_func_registrar",
+        "@com_google_cel_cpp//eval/public:cel_expr_builder_factory",
         "@envoy_api//envoy/config/common/mutation_rules/v3:pkg_cc_proto",
         "@envoy_api//envoy/config/core/v3:pkg_cc_proto",
         "@envoy_api//envoy/extensions/filters/http/ext_proc/v3:pkg_cc_proto",
         "@envoy_api//envoy/service/ext_proc/v3:pkg_cc_proto",
-    ],
+    ] + select(
+        {
+            "//bazel:windows_x86_64": [],
+            "//conditions:default": [
+                "@com_google_cel_cpp//parser",
+            ],
+        },
+    ),
 )
 
 envoy_cc_extension(
     name = "config",
     srcs = ["config.cc"],
     hdrs = ["config.h"],
+    copts = select({
+        "//bazel:windows_x86_64": [],
+        "//conditions:default": [
+            "-DUSE_CEL_PARSER",
+        ],
+    }),
     deps = [
         ":client_lib",
         ":ext_proc",
+        "//source/extensions/filters/common/expr:evaluator_lib",
         "//source/extensions/filters/http/common:factory_base_lib",
         "@envoy_api//envoy/extensions/filters/http/ext_proc/v3:pkg_cc_proto",
     ],

source/extensions/filters/http/ext_proc/config.cc

@@ -15,9 +15,9 @@ Http::FilterFactoryCb ExternalProcessingFilterConfig::createFilterFactoryFromPro
       PROTOBUF_GET_MS_OR_DEFAULT(proto_config, message_timeout, DefaultMessageTimeoutMs);
   const uint32_t max_message_timeout_ms =
       PROTOBUF_GET_MS_OR_DEFAULT(proto_config, max_message_timeout, DefaultMaxMessageTimeoutMs);
-  const auto filter_config =
-      std::make_shared<FilterConfig>(proto_config, std::chrono::milliseconds(message_timeout_ms),
-                                     max_message_timeout_ms, context.scope(), stats_prefix);
+  const auto filter_config = std::make_shared<FilterConfig>(
+      proto_config, std::chrono::milliseconds(message_timeout_ms), max_message_timeout_ms,
+      context.scope(), stats_prefix, Envoy::Extensions::Filters::Common::Expr::getBuilder(context));
 
   return [filter_config, grpc_service = proto_config.grpc_service(),
           &context](Http::FilterChainFactoryCallbacks& callbacks) {
@@ -45,9 +45,10 @@ ExternalProcessingFilterConfig::createFilterFactoryFromProtoWithServerContextTyp
       PROTOBUF_GET_MS_OR_DEFAULT(proto_config, message_timeout, DefaultMessageTimeoutMs);
   const uint32_t max_message_timeout_ms =
       PROTOBUF_GET_MS_OR_DEFAULT(proto_config, max_message_timeout, DefaultMaxMessageTimeoutMs);
-  const auto filter_config =
-      std::make_shared<FilterConfig>(proto_config, std::chrono::milliseconds(message_timeout_ms),
-                                     max_message_timeout_ms, server_context.scope(), stats_prefix);
+  const auto filter_config = std::make_shared<FilterConfig>(
+      proto_config, std::chrono::milliseconds(message_timeout_ms), max_message_timeout_ms,
+      server_context.scope(), stats_prefix,
+      Envoy::Extensions::Filters::Common::Expr::getBuilder(server_context));
 
   return [filter_config, grpc_service = proto_config.grpc_service(),
           &server_context](Http::FilterChainFactoryCallbacks& callbacks) {

source/extensions/filters/http/ext_proc/config.h

@@ -5,6 +5,7 @@
 #include "envoy/extensions/filters/http/ext_proc/v3/ext_proc.pb.h"
 #include "envoy/extensions/filters/http/ext_proc/v3/ext_proc.pb.validate.h"
 
+#include "source/extensions/filters/common/expr/evaluator.h"
 #include "source/extensions/filters/http/common/factory_base.h"
 
 namespace Envoy {
@@ -29,7 +30,7 @@ class ExternalProcessingFilterConfig
 
   Router::RouteSpecificFilterConfigConstSharedPtr createRouteSpecificFilterConfigTyped(
       const envoy::extensions::filters::http::ext_proc::v3::ExtProcPerRoute& proto_config,
-      Server::Configuration::ServerFactoryContext& context,
+      Server::Configuration::ServerFactoryContext&,
       ProtobufMessage::ValidationVisitor& validator) override;
 
   Http::FilterFactoryCb createFilterFactoryFromProtoWithServerContextTyped(

source/extensions/filters/http/ext_proc/ext_proc.cc

@@ -8,6 +8,10 @@
 
 #include "absl/strings/str_format.h"
 
+#if defined(USE_CEL_PARSER)
+#include "parser/parser.h"
+#endif
+
 namespace Envoy {
 namespace Extensions {
 namespace HttpFilters {
@@ -113,6 +117,27 @@ ExtProcLoggingInfo::grpcCalls(envoy::config::core::v3::TrafficDirection traffic_
              : encoding_processor_grpc_calls_;
 }
 
+absl::flat_hash_map<std::string, Extensions::Filters::Common::Expr::ExpressionPtr>
+FilterConfig::initExpressions(const Protobuf::RepeatedPtrField<std::string>& matchers) const {
+  absl::flat_hash_map<std::string, Extensions::Filters::Common::Expr::ExpressionPtr> expressions;
+#if defined(USE_CEL_PARSER)
+  for (const auto& matcher : matchers) {
+    auto parse_status = google::api::expr::parser::Parse(matcher);
+    if (!parse_status.ok()) {
+      throw EnvoyException("Unable to parse descriptor expression: " +
+                           parse_status.status().ToString());
+    }
+    expressions.emplace(matcher, Extensions::Filters::Common::Expr::createExpression(
+                                     builder_->builder(), parse_status.value().expr()));
+  }
+#else
+  ENVOY_LOG(warn, "CEL expression parsing is not available for use in this environment."
+                  " Attempted to parse " +
+                      std::to_string(matchers.size()) + " expressions");
+#endif
+  return expressions;
+}
+
 FilterConfigPerRoute::FilterConfigPerRoute(const ExtProcPerRoute& config)
     : disabled_(config.disabled()) {
   if (config.has_overrides()) {
@@ -201,7 +226,8 @@ void Filter::onDestroy() {
 }
 
 FilterHeadersStatus Filter::onHeaders(ProcessorState& state,
-                                      Http::RequestOrResponseHeaderMap& headers, bool end_stream) {
+                                      Http::RequestOrResponseHeaderMap& headers, bool end_stream,
+                                      absl::optional<ProtobufWkt::Struct> proto) {
   switch (openStream()) {
   case StreamOpenState::Error:
     return FilterHeadersStatus::StopIteration;
@@ -219,6 +245,9 @@ FilterHeadersStatus Filter::onHeaders(ProcessorState& state,
   MutationUtils::headersToProto(headers, config_->allowedHeaders(), config_->disallowedHeaders(),
                                 *headers_req->mutable_headers());
   headers_req->set_end_of_stream(end_stream);
+  if (proto.has_value()) {
+    (*headers_req->mutable_attributes())[FilterName] = proto.value();
+  }
   state.onStartProcessorCall(std::bind(&Filter::onMessageTimeout, this), config_->messageTimeout(),
                              ProcessorState::CallbackState::HeadersCallback);
   ENVOY_LOG(debug, "Sending headers message");
@@ -228,6 +257,48 @@ FilterHeadersStatus Filter::onHeaders(ProcessorState& state,
   return FilterHeadersStatus::StopIteration;
 }
 
+const absl::optional<ProtobufWkt::Struct> Filter::evaluateAttributes(
+    Filters::Common::Expr::ActivationPtr activation,
+    const absl::flat_hash_map<std::string, Extensions::Filters::Common::Expr::ExpressionPtr>&
+        expr) {
+  absl::optional<ProtobufWkt::Struct> proto;
+  if (expr.size() > 0) {
+    proto.emplace(ProtobufWkt::Struct{});
+    for (const auto& hash_entry : expr) {
+      ProtobufWkt::Arena arena;
+      const auto result = hash_entry.second.get()->Evaluate(*activation, &arena);
+      if (!result.ok()) {
+        // TODO: Stats?
+        continue;
+      }
+
+      if (result.value().IsError()) {
+        ENVOY_LOG(trace, "error parsing cel expression {}", hash_entry.first);
+        continue;
+      }
+
+      ProtobufWkt::Value value;
+      switch (result.value().type()) {
+      case google::api::expr::runtime::CelValue::Type::kBool:
+        value.set_bool_value(result.value().BoolOrDie());
+        break;
+      case google::api::expr::runtime::CelValue::Type::kNullType:
+        value.set_null_value(ProtobufWkt::NullValue{});
+        break;
+      case google::api::expr::runtime::CelValue::Type::kDouble:
+        value.set_number_value(result.value().DoubleOrDie());
+        break;
+      default:
+        value.set_string_value(Filters::Common::Expr::print(result.value()));
+      }
+
+      (*(proto.value()).mutable_fields())[hash_entry.first] = value;
+    }
+  }
+
+  return proto;
+}
+
 FilterHeadersStatus Filter::decodeHeaders(RequestHeaderMap& headers, bool end_stream) {
   ENVOY_LOG(trace, "decodeHeaders: end_stream = {}", end_stream);
   mergePerRouteConfig();
@@ -237,7 +308,14 @@ FilterHeadersStatus Filter::decodeHeaders(RequestHeaderMap& headers, bool end_st
 
   FilterHeadersStatus status = FilterHeadersStatus::Continue;
   if (decoding_state_.sendHeaders()) {
-    status = onHeaders(decoding_state_, headers, end_stream);
+    absl::optional<Envoy::ProtobufWkt::Struct> proto;
+    if (!config_->requestExpr().empty()) {
+      auto activation_ptr = Filters::Common::Expr::createActivation(decoding_state_.streamInfo(),
+                                                                    &headers, nullptr, nullptr);
+      proto = evaluateAttributes(std::move(activation_ptr), config_->requestExpr());
+    }
+
+    status = onHeaders(decoding_state_, headers, end_stream, proto);
     ENVOY_LOG(trace, "onHeaders returning {}", static_cast<int>(status));
   } else {
     ENVOY_LOG(trace, "decodeHeaders: Skipped header processing");
@@ -515,7 +593,14 @@ FilterHeadersStatus Filter::encodeHeaders(ResponseHeaderMap& headers, bool end_s
 
   FilterHeadersStatus status = FilterHeadersStatus::Continue;
   if (!processing_complete_ && encoding_state_.sendHeaders()) {
-    status = onHeaders(encoding_state_, headers, end_stream);
+    absl::optional<Envoy::ProtobufWkt::Struct> proto;
+    if (!config_->responseExpr().empty()) {
+      auto activation_ptr = Filters::Common::Expr::createActivation(encoding_state_.streamInfo(),
+                                                                    nullptr, &headers, nullptr);
+      proto = evaluateAttributes(std::move(activation_ptr), config_->responseExpr());
+    }
+
+    status = onHeaders(encoding_state_, headers, end_stream, proto);
     ENVOY_LOG(trace, "onHeaders returns {}", static_cast<int>(status));
   } else {
     ENVOY_LOG(trace, "encodeHeaders: Skipped header processing");

source/extensions/filters/http/ext_proc/ext_proc.h

@@ -21,6 +21,7 @@
 #include "source/common/common/logger.h"
 #include "source/common/common/matchers.h"
 #include "source/common/protobuf/protobuf.h"
+#include "source/extensions/filters/common/expr/evaluator.h"
 #include "source/extensions/filters/common/mutation_rules/mutation_rules.h"
 #include "source/extensions/filters/http/common/pass_through_filter.h"
 #include "source/extensions/filters/http/ext_proc/client.h"
@@ -121,12 +122,13 @@ class ExtProcLoggingInfo : public Envoy::StreamInfo::FilterState::Object {
   Upstream::HostDescriptionConstSharedPtr upstream_host_;
 };
 
-class FilterConfig {
+class FilterConfig : public Logger::Loggable<Logger::Id::ext_proc> {
 public:
   FilterConfig(const envoy::extensions::filters::http::ext_proc::v3::ExternalProcessor& config,
                const std::chrono::milliseconds message_timeout,
                const uint32_t max_message_timeout_ms, Stats::Scope& scope,
-               const std::string& stats_prefix)
+               const std::string& stats_prefix,
+               Extensions::Filters::Common::Expr::BuilderInstanceSharedPtr builder)
       : failure_mode_allow_(config.failure_mode_allow()),
         disable_clear_route_cache_(config.disable_clear_route_cache()),
         message_timeout_(message_timeout), max_message_timeout_ms_(max_message_timeout_ms),
@@ -136,7 +138,9 @@ class FilterConfig {
         allow_mode_override_(config.allow_mode_override()),
         disable_immediate_response_(config.disable_immediate_response()),
         allowed_headers_(initHeaderMatchers(config.forward_rules().allowed_headers())),
-        disallowed_headers_(initHeaderMatchers(config.forward_rules().disallowed_headers())) {}
+        disallowed_headers_(initHeaderMatchers(config.forward_rules().disallowed_headers())),
+        builder_(builder), request_expr_(initExpressions(config.request_attributes())),
+        response_expr_(initExpressions(config.response_attributes())) {}
 
   bool failureModeAllow() const { return failure_mode_allow_; }
 
@@ -166,6 +170,16 @@ class FilterConfig {
 
   const Envoy::ProtobufWkt::Struct& filterMetadata() const { return filter_metadata_; }
 
+  const absl::flat_hash_map<std::string, Extensions::Filters::Common::Expr::ExpressionPtr>&
+  requestExpr() const {
+    return request_expr_;
+  }
+
+  const absl::flat_hash_map<std::string, Extensions::Filters::Common::Expr::ExpressionPtr>&
+  responseExpr() const {
+    return response_expr_;
+  }
+
 private:
   ExtProcFilterStats generateStats(const std::string& prefix,
                                    const std::string& filter_stats_prefix, Stats::Scope& scope) {
@@ -183,6 +197,9 @@ class FilterConfig {
     return header_matchers;
   }
 
+  absl::flat_hash_map<std::string, Extensions::Filters::Common::Expr::ExpressionPtr>
+  initExpressions(const Protobuf::RepeatedPtrField<std::string>& matchers) const;
+
   const bool failure_mode_allow_;
   const bool disable_clear_route_cache_;
   const std::chrono::milliseconds message_timeout_;
@@ -201,6 +218,13 @@ class FilterConfig {
   const std::vector<Matchers::StringMatcherPtr> allowed_headers_;
   // Empty disallowed_header_ means disallow nothing, i.e, allow all.
   const std::vector<Matchers::StringMatcherPtr> disallowed_headers_;
+
+  Extensions::Filters::Common::Expr::BuilderInstanceSharedPtr builder_;
+
+  const absl::flat_hash_map<std::string, Extensions::Filters::Common::Expr::ExpressionPtr>
+      request_expr_;
+  const absl::flat_hash_map<std::string, Extensions::Filters::Common::Expr::ExpressionPtr>
+      response_expr_;
 };
 
 using FilterConfigSharedPtr = std::shared_ptr<FilterConfig>;
@@ -300,7 +324,13 @@ class Filter : public Logger::Loggable<Logger::Id::ext_proc>,
   void sendImmediateResponse(const envoy::service::ext_proc::v3::ImmediateResponse& response);
 
   Http::FilterHeadersStatus onHeaders(ProcessorState& state,
-                                      Http::RequestOrResponseHeaderMap& headers, bool end_stream);
+                                      Http::RequestOrResponseHeaderMap& headers, bool end_stream,
+                                      absl::optional<ProtobufWkt::Struct> proto);
+
+  const absl::optional<ProtobufWkt::Struct> evaluateAttributes(
+      Filters::Common::Expr::ActivationPtr activation,
+      const absl::flat_hash_map<std::string, Extensions::Filters::Common::Expr::ExpressionPtr>&
+          expr);
   // Return a pair of whether to terminate returning the current result.
   std::pair<bool, Http::FilterDataStatus> sendStreamChunk(ProcessorState& state);
   Http::FilterDataStatus onData(ProcessorState& state, Buffer::Instance& data, bool end_stream);

source/extensions/filters/http/ext_proc/processor_state.h

@@ -172,6 +172,8 @@ class ProcessorState : public Logger::Loggable<Logger::Id::ext_proc> {
   virtual envoy::service::ext_proc::v3::HttpTrailers*
   mutableTrailers(envoy::service::ext_proc::v3::ProcessingRequest& request) const PURE;
 
+  virtual StreamInfo::StreamInfo& streamInfo() PURE;
+
 protected:
   void setBodyMode(
       envoy::extensions::filters::http::ext_proc::v3::ProcessingMode_BodySendMode body_mode);
@@ -283,6 +285,8 @@ class DecodingProcessorState : public ProcessorState {
   void requestWatermark() override;
   void clearWatermark() override;
 
+  StreamInfo::StreamInfo& streamInfo() override { return decoder_callbacks_->streamInfo(); }
+
 private:
   void setProcessingModeInternal(
       const envoy::extensions::filters::http::ext_proc::v3::ProcessingMode& mode);
@@ -356,6 +360,8 @@ class EncodingProcessorState : public ProcessorState {
   void requestWatermark() override;
   void clearWatermark() override;
 
+  StreamInfo::StreamInfo& streamInfo() override { return encoder_callbacks_->streamInfo(); }
+
 private:
   void setProcessingModeInternal(
       const envoy::extensions::filters::http::ext_proc::v3::ProcessingMode& mode);