syntax = "proto3";

package envoy.service.ext_proc.v3;

import "envoy/config/core/v3/base.proto";
import "envoy/extensions/filters/http/ext_proc/v3/processing_mode.proto";
import "envoy/type/v3/http_status.proto";

import "google/protobuf/duration.proto";
import "google/protobuf/struct.proto";

import "xds/annotations/v3/status.proto";

import "envoy/annotations/deprecation.proto";
import "udpa/annotations/status.proto";
import "validate/validate.proto";

option java_package = "io.envoyproxy.envoy.service.ext_proc.v3";
option java_outer_classname = "ExternalProcessorProto";
option java_multiple_files = true;
option go_package = "github.com/envoyproxy/go-control-plane/envoy/service/ext_proc/v3;ext_procv3";
option (udpa.annotations.file_status).package_version_status = ACTIVE;

// [#protodoc-title: External processing service]

// A service that can access and modify HTTP requests and responses
// as part of a filter chain.
// The overall external processing protocol works like this:
//
// 1. Envoy sends to the service information about the HTTP request.
// 2. The service sends back a ProcessingResponse message that directs Envoy
//    to either stop processing, continue without it, or send it the
//    next chunk of the message body.
// 3. If so requested, Envoy sends the server chunks of the message body,
//    or the entire body at once. In either case, the server sends back
//    a ProcessingResponse after each message it receives.
// 4. If so requested, Envoy sends the server the HTTP trailers,
//    and the server sends back a ProcessingResponse.
// 5. At this point, request processing is done, and we pick up again
//    at step 1 when Envoy receives a response from the upstream server.
// 6. At any point above, if the server closes the gRPC stream cleanly,
//    then Envoy proceeds without consulting the server.
// 7. At any point above, if the server closes the gRPC stream with an error,
//    then Envoy returns a 500 error to the client, unless the filter
//    was configured to ignore errors.
//
// In other words, the process is a request/response conversation, but
// using a gRPC stream to make it easier for the server to
// maintain state.
service ExternalProcessor {
  // This begins the bidirectional stream that Envoy will use to
  // give the server control over what the filter does. The actual
  // protocol is described by the ProcessingRequest and ProcessingResponse
  // messages below.
  rpc Process(stream ProcessingRequest) returns (stream ProcessingResponse) {
  }
}

// This represents the different types of messages that Envoy can send
// to an external processing server.
// [#next-free-field: 11]
message ProcessingRequest {
  reserved 1;

  reserved "async_mode";

  // Each request message will include one of the following sub-messages. Which
  // ones are set for a particular HTTP request/response depend on the
  // processing mode.
  oneof request {
    option (validate.required) = true;

    // Information about the HTTP request headers, as well as peer info and additional
    // properties. Unless ``observability_mode`` is ``true``, the server must send back a
    // HeaderResponse message, an ImmediateResponse message, or close the stream.
    HttpHeaders request_headers = 2;

    // Information about the HTTP response headers, as well as peer info and additional
    // properties. Unless ``observability_mode`` is ``true``, the server must send back a
    // HeaderResponse message or close the stream.
    HttpHeaders response_headers = 3;

    // A chunk of the HTTP request body. Unless ``observability_mode`` is true, the server must send back
    // a BodyResponse message, an ImmediateResponse message, or close the stream.
    HttpBody request_body = 4;

    // A chunk of the HTTP response body. Unless ``observability_mode`` is ``true``, the server must send back
    // a BodyResponse message or close the stream.
    HttpBody response_body = 5;

    // The HTTP trailers for the request path. Unless ``observability_mode`` is ``true``, the server
    // must send back a TrailerResponse message or close the stream.
    //
    // This message is only sent if the trailers processing mode is set to ``SEND`` and
    // the original downstream request has trailers.
    HttpTrailers request_trailers = 6;

    // The HTTP trailers for the response path. Unless ``observability_mode`` is ``true``, the server
    // must send back a TrailerResponse message or close the stream.
    //
    // This message is only sent if the trailers processing mode is set to ``SEND`` and
    // the original upstream response has trailers.
    HttpTrailers response_trailers = 7;
  }

  // Dynamic metadata associated with the request.
  config.core.v3.Metadata metadata_context = 8;

  // The values of properties selected by the ``request_attributes``
  // or ``response_attributes`` list in the configuration. Each entry
  // in the list is populated from the standard
  // :ref:`attributes <arch_overview_attributes>` supported across Envoy.
  map<string, google.protobuf.Struct> attributes = 9;

  // Specify whether the filter that sent this request is running in :ref:`observability_mode
  // <envoy_v3_api_field_extensions.filters.http.ext_proc.v3.ExternalProcessor.observability_mode>`
  // and defaults to false.
  //
  // * A value of ``false`` indicates that the server must respond
  //   to this message by either sending back a matching ProcessingResponse message,
  //   or by closing the stream.
  // * A value of ``true`` indicates that the server should not respond to this message, as any
  //   responses will be ignored. However, it may still close the stream to indicate that no more messages
  //   are needed.
  //
  bool observability_mode = 10;
}

// For every ProcessingRequest received by the server with the ``observability_mode`` field
// set to false, the server must send back exactly one ProcessingResponse message.
// [#next-free-field: 11]
message ProcessingResponse {
  // The response type that is sent by the server.
  oneof response {
    option (validate.required) = true;

    // The server must send back this message in response to a message with the
    // ``request_headers`` field set.
    HeadersResponse request_headers = 1;

    // The server must send back this message in response to a message with the
    // ``response_headers`` field set.
    HeadersResponse response_headers = 2;

    // The server must send back this message in response to a message with
    // the ``request_body`` field set.
    BodyResponse request_body = 3;

    // The server must send back this message in response to a message with
    // the ``response_body`` field set.
    BodyResponse response_body = 4;

    // The server must send back this message in response to a message with
    // the ``request_trailers`` field set.
    TrailersResponse request_trailers = 5;

    // The server must send back this message in response to a message with
    // the ``response_trailers`` field set.
    TrailersResponse response_trailers = 6;

    // If specified, attempt to create a locally generated response, send it
    // downstream, and stop processing additional filters and ignore any
    // additional messages received from the remote server for this request or
    // response. If a response has already started -- for example, if this
    // message is sent response to a ``response_body`` message -- then
    // this will either ship the reply directly to the downstream codec,
    // or reset the stream.
    ImmediateResponse immediate_response = 7;
  }

  // Optional metadata that will be emitted as dynamic metadata to be consumed by
  // following filters. This metadata will be placed in the namespace(s) specified by the top-level
  // field name(s) of the struct.
  google.protobuf.Struct dynamic_metadata = 8;

  // Override how parts of the HTTP request and response are processed
  // for the duration of this particular request/response only. Servers
  // may use this to intelligently control how requests are processed
  // based on the headers and other metadata that they see.
  // This field is only applicable when servers responding to the header requests.
  // If it is set in the response to the body or trailer requests, it will be ignored by Envoy.
  // It is also ignored by Envoy when the ext_proc filter config
  // :ref:`allow_mode_override
  // <envoy_v3_api_field_extensions.filters.http.ext_proc.v3.ExternalProcessor.allow_mode_override>`
  // is set to false, or
  // :ref:`send_body_without_waiting_for_header_response
  // <envoy_v3_api_field_extensions.filters.http.ext_proc.v3.ExternalProcessor.send_body_without_waiting_for_header_response>`
  // is set to true.
  envoy.extensions.filters.http.ext_proc.v3.ProcessingMode mode_override = 9;

  // When ext_proc server receives a request message, in case it needs more
  // time to process the message, it sends back a ProcessingResponse message
  // with a new timeout value. When Envoy receives this response message,
  // it ignores other fields in the response, just stop the original timer,
  // which has the timeout value specified in
  // :ref:`message_timeout
  // <envoy_v3_api_field_extensions.filters.http.ext_proc.v3.ExternalProcessor.message_timeout>`
  // and start a new timer with this ``override_message_timeout`` value and keep the
  // Envoy ext_proc filter state machine intact.
  // Has to be >= 1ms and <=
  // :ref:`max_message_timeout <envoy_v3_api_field_extensions.filters.http.ext_proc.v3.ExternalProcessor.max_message_timeout>`
  // Such message can be sent at most once in a particular Envoy ext_proc filter processing state.
  // To enable this API, one has to set ``max_message_timeout`` to a number >= 1ms.
  google.protobuf.Duration override_message_timeout = 10;
}

// The following are messages that are sent to the server.

// This message is sent to the external server when the HTTP request and responses
// are first received.
message HttpHeaders {
  // The HTTP request headers. All header keys will be
  // lower-cased, because HTTP header keys are case-insensitive.
  // The header value is encoded in the
  // :ref:`raw_value <envoy_v3_api_field_config.core.v3.HeaderValue.raw_value>` field.
  config.core.v3.HeaderMap headers = 1;

  // [#not-implemented-hide:]
  // This field is deprecated and not implemented. Attributes will be sent in
  // the  top-level :ref:`attributes <envoy_v3_api_field_service.ext_proc.v3.ProcessingRequest.attributes`
  // field.
  map<string, google.protobuf.Struct> attributes = 2
      [deprecated = true, (envoy.annotations.deprecated_at_minor_version) = "3.0"];

  // If ``true``, then there is no message body associated with this
  // request or response.
  bool end_of_stream = 3;
}

// This message is sent to the external server when the HTTP request and
// response bodies are received.
message HttpBody {
  // The contents of the body in the HTTP request/response. Note that in
  // streaming mode multiple ``HttpBody`` messages may be sent.
  bytes body = 1;

  // If ``true``, this will be the last ``HttpBody`` message that will be sent and no
  // trailers will be sent for the current request/response.
  bool end_of_stream = 2;
}

// This message is sent to the external server when the HTTP request and
// response trailers are received.
message HttpTrailers {
  // The header value is encoded in the
  // :ref:`raw_value <envoy_v3_api_field_config.core.v3.HeaderValue.raw_value>` field.
  config.core.v3.HeaderMap trailers = 1;
}

// The following are messages that may be sent back by the server.

// This message is sent by the external server to Envoy after ``HttpHeaders`` was
// sent to it.
message HeadersResponse {
  // Details the modifications (if any) to be made by Envoy to the current
  // request/response.
  CommonResponse response = 1;
}

// This message is sent by the external server to Envoy after ``HttpBody`` was
// sent to it.
message BodyResponse {
  // Details the modifications (if any) to be made by Envoy to the current
  // request/response.
  CommonResponse response = 1;
}

// This message is sent by the external server to Envoy after ``HttpTrailers`` was
// sent to it.
message TrailersResponse {
  // Details the modifications (if any) to be made by Envoy to the current
  // request/response trailers.
  HeaderMutation header_mutation = 1;
}

// This message contains common fields between header and body responses.
// [#next-free-field: 6]
message CommonResponse {
  // The status of the response.
  enum ResponseStatus {
    // Apply the mutation instructions in this message to the
    // request or response, and then continue processing the filter
    // stream as normal. This is the default.
    CONTINUE = 0;

    // Apply the specified header mutation, replace the body with the body
    // specified in the body mutation (if present), and do not send any
    // further messages for this request or response even if the processing
    // mode is configured to do so.
    //
    // When used in response to a request_headers or response_headers message,
    // this status makes it possible to either completely replace the body
    // while discarding the original body, or to add a body to a message that
    // formerly did not have one.
    //
    // In other words, this response makes it possible to turn an HTTP GET
    // into a POST, PUT, or PATCH.
    CONTINUE_AND_REPLACE = 1;
  }

  // If set, provide additional direction on how the Envoy proxy should
  // handle the rest of the HTTP filter chain.
  ResponseStatus status = 1 [(validate.rules).enum = {defined_only: true}];

  // Instructions on how to manipulate the headers. When responding to an
  // HttpBody request, header mutations will only take effect if
  // the current processing mode for the body is BUFFERED.
  HeaderMutation header_mutation = 2;

  // Replace the body of the last message sent to the remote server on this
  // stream. If responding to an HttpBody request, simply replace or clear
  // the body chunk that was sent with that request. Body mutations may take
  // effect in response either to ``header`` or ``body`` messages. When it is
  // in response to ``header`` messages, it only take effect if the
  // :ref:`status <envoy_v3_api_field_service.ext_proc.v3.CommonResponse.status>`
  // is set to CONTINUE_AND_REPLACE.
  BodyMutation body_mutation = 3;

  // [#not-implemented-hide:]
  // Add new trailers to the message. This may be used when responding to either a
  // HttpHeaders or HttpBody message, but only if this message is returned
  // along with the CONTINUE_AND_REPLACE status.
  // The header value is encoded in the
  // :ref:`raw_value <envoy_v3_api_field_config.core.v3.HeaderValue.raw_value>` field.
  config.core.v3.HeaderMap trailers = 4;

  // Clear the route cache for the current client request. This is necessary
  // if the remote server modified headers that are used to calculate the route.
  // This field is ignored in the response direction. This field is also ignored
  // if the Envoy ext_proc filter is in the upstream filter chain.
  bool clear_route_cache = 5;
}

// This message causes the filter to attempt to create a locally
// generated response, send it  downstream, stop processing
// additional filters, and ignore any additional messages received
// from the remote server for this request or response. If a response
// has already started, then  this will either ship the reply directly
// to the downstream codec, or reset the stream.
// [#next-free-field: 6]
message ImmediateResponse {
  // The response code to return.
  type.v3.HttpStatus status = 1 [(validate.rules).message = {required: true}];

  // Apply changes to the default headers, which will include content-type.
  HeaderMutation headers = 2;

  // The message body to return with the response which is sent using the
  // text/plain content type, or encoded in the grpc-message header.
  bytes body = 3;

  // If set, then include a gRPC status trailer.
  GrpcStatus grpc_status = 4;

  // A string detailing why this local reply was sent, which may be included
  // in log and debug output (e.g. this populates the %RESPONSE_CODE_DETAILS%
  // command operator field for use in access logging).
  string details = 5;
}

// This message specifies a gRPC status for an ImmediateResponse message.
message GrpcStatus {
  // The actual gRPC status.
  uint32 status = 1;
}

// Change HTTP headers or trailers by appending, replacing, or removing
// headers.
message HeaderMutation {
  // Add or replace HTTP headers. Attempts to set the value of
  // any ``x-envoy`` header, and attempts to set the ``:method``,
  // ``:authority``, ``:scheme``, or ``host`` headers will be ignored.
  // The header value is encoded in the
  // :ref:`raw_value <envoy_v3_api_field_config.core.v3.HeaderValue.raw_value>` field.
  repeated config.core.v3.HeaderValueOption set_headers = 1;

  // Remove these HTTP headers. Attempts to remove system headers --
  // any header starting with ``:``, plus ``host`` -- will be ignored.
  repeated string remove_headers = 2;
}

// The body response message corresponding to FULL_DUPLEX_STREAMED body mode.
message StreamedBodyResponse {
  // The body response chunk that will be passed to the upstream/downstream by Envoy.
  bytes body = 1;

  // The server sets this flag to true if it has received a body request with
  // :ref:`end_of_stream <envoy_v3_api_field_service.ext_proc.v3.HttpBody.end_of_stream>` set to true,
  // and this is the last chunk of body responses.
  bool end_of_stream = 2;
}

// This message specifies the body mutation the server sends to Envoy.
message BodyMutation {
  // The type of mutation for the body.
  oneof mutation {
    // The entire body to replace.
    // Should only be used when the corresponding ``BodySendMode`` in the
    // :ref:`processing_mode <envoy_v3_api_field_extensions.filters.http.ext_proc.v3.ExternalProcessor.processing_mode>`
    // is not set to ``FULL_DUPLEX_STREAMED``.
    bytes body = 1;

    // Clear the corresponding body chunk.
    // Should only be used when the corresponding ``BodySendMode`` in the
    // :ref:`processing_mode <envoy_v3_api_field_extensions.filters.http.ext_proc.v3.ExternalProcessor.processing_mode>`
    // is not set to ``FULL_DUPLEX_STREAMED``.
    // Clear the corresponding body chunk.
    bool clear_body = 2;

    // Must be used when the corresponding ``BodySendMode`` in the
    // :ref:`processing_mode <envoy_v3_api_field_extensions.filters.http.ext_proc.v3.ExternalProcessor.processing_mode>`
    // is set to ``FULL_DUPLEX_STREAMED``.
    StreamedBodyResponse streamed_response = 3
        [(xds.annotations.v3.field_status).work_in_progress = true];
  }
}
