extproc: register filter and parse base and override config

internal/envconfig/xds.go

@@ -94,6 +94,7 @@ var (
 	// the client side. For more details, see:
 	// https://github.com/grpc/proposal/blob/master/A93-xds-ext-proc.md
 	XDSClientExtProcEnabled = boolFromEnv("GRPC_EXPERIMENTAL_XDS_EXT_PROC_ON_CLIENT", false)
+
 	// GCPAuthenticationFilterEnabled enables the xDS GCP Authentication
 	// filter. For more details, see:
 	// https://github.com/grpc/proposal/blob/master/A83-xds-gcp-authn-filter.md

internal/xds/httpfilter/extproc/config.go

@@ -0,0 +1,34 @@
+/*
+ *
+ * Copyright 2026 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.
+ *
+ */
+
+package extproc
+
+import (
+	pb "github.com/envoyproxy/go-control-plane/envoy/extensions/filters/http/ext_proc/v3"
+	"google.golang.org/grpc/internal/xds/httpfilter"
+)
+
+type baseConfig struct {
+	httpfilter.FilterConfig
+	config *pb.ExternalProcessor
+}
+
+type overrideConfig struct {
+	httpfilter.FilterConfig
+	config *pb.ExtProcOverrides
+}

internal/xds/httpfilter/extproc/ext_proc.go

@@ -0,0 +1,120 @@
+/*
+ *
+ * Copyright 2026 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.
+ *
+ */
+
+// Package extproc implements the Envoy external processing filter.
+package extproc
+
+import (
+	"fmt"
+
+	"google.golang.org/grpc/internal/envconfig"
+	"google.golang.org/grpc/internal/xds/httpfilter"
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/known/anypb"
+
+	fpb "github.com/envoyproxy/go-control-plane/envoy/extensions/filters/http/ext_proc/v3"
+)
+
+func init() {
+	if envconfig.XDSClientExtProcEnabled {
+		httpfilter.Register(builder{})
+	}
+}
+
+type builder struct{}
+
+func (builder) TypeURLs() []string {
+	return []string{"type.googleapis.com/envoy.extensions.filters.http.ext_proc.v3.ExternalProcessor"}
+}
+
+// validateBodyProcessingMode ensures that the body processing mode is either
+// NONE or GRPC.
+func validateBodyProcessingMode(pMode *fpb.ProcessingMode) error {
+	if reqMode := pMode.GetRequestBodyMode(); reqMode != fpb.ProcessingMode_NONE && reqMode != fpb.ProcessingMode_GRPC {
+		return fmt.Errorf("ext_proc: invalid request body mode %v: want 'NONE' or 'GRPC'", reqMode)
+	}
+	if resMode := pMode.GetResponseBodyMode(); resMode != fpb.ProcessingMode_NONE && resMode != fpb.ProcessingMode_GRPC {
+		return fmt.Errorf("ext_proc: invalid response body mode %v: want 'NONE' or 'GRPC'", resMode)
+	}
+	return nil
+}
+
+func (builder) ParseFilterConfig(cfg proto.Message) (httpfilter.FilterConfig, error) {
+	if cfg == nil {
+		return nil, fmt.Errorf("ext_proc: nil base configuration message provided")
+	}
+	m, ok := cfg.(*anypb.Any)
+	if !ok {
+		return nil, fmt.Errorf("ext_proc: error parsing config %v: unknown type %T", cfg, cfg)
+	}
+	msg := new(fpb.ExternalProcessor)
+	if err := m.UnmarshalTo(msg); err != nil {
+		return nil, fmt.Errorf("ext_proc: failed to unmarshal config %v: %v", cfg, err)
+	}
+	if msg.GetGrpcService() == nil {
+		return nil, fmt.Errorf("ext_proc: empty grpc_service provided in config %v", cfg)
+	}
+	if msg.GetGrpcService().GetGoogleGrpc() == nil {
+		return nil, fmt.Errorf("ext_proc: only google_grpc grpc_service is supported, got %v in config %v", msg.GrpcService.GetTargetSpecifier(), cfg)
+	}
+	if msg.GetProcessingMode() == nil {
+		return nil, fmt.Errorf("ext_proc: missing processing_mode in config %v", cfg)
+	}
+	if err := validateBodyProcessingMode(msg.GetProcessingMode()); err != nil {
+		return nil, err
+	}
+	if mr := msg.GetMutationRules(); mr != nil {
+		if err := mr.GetAllowExpression().Validate(); err != nil {
+			return nil, fmt.Errorf("ext_proc: %v", err)
+		}
+		if err := mr.GetDisallowExpression().Validate(); err != nil {
+			return nil, fmt.Errorf("ext_proc: %v", err)
+		}
+	}
+	return baseConfig{config: msg}, nil
+}
+
+func (builder) ParseFilterConfigOverride(ov proto.Message) (httpfilter.FilterConfig, error) {
+	if ov == nil {
+		return nil, fmt.Errorf("ext_proc: nil override configuration provided")
+	}
+	m, ok := ov.(*anypb.Any)
+	if !ok {
+		return nil, fmt.Errorf("ext_proc: error parsing override %v: unknown type %T", ov, ov)
+	}
+	msg := new(fpb.ExtProcPerRoute)
+	if err := m.UnmarshalTo(msg); err != nil {
+		return nil, fmt.Errorf("ext_proc: failed to unmarshal override %v: %v", ov, err)
+	}
+	override := msg.GetOverrides()
+	// GrpcService can be optionally provided in the override config. If
+	// provided, it must be of type google_grpc.
+	if override.GetGrpcService() != nil && override.GrpcService.GetGoogleGrpc() == nil {
+		return nil, fmt.Errorf("ext_proc: only google_grpc grpc_service is supported, got %v in override %v", override.GrpcService.GetTargetSpecifier(), override)
+	}
+	if pm := override.GetProcessingMode(); pm != nil {
+		if err := validateBodyProcessingMode(pm); err != nil {
+			return nil, err
+		}
+	}
+	return overrideConfig{config: override}, nil
+}
+
+func (builder) IsTerminal() bool {
+	return false
+}