syntax = "proto3";

package envoy.config.filter.network.http_connection_manager.v2;

import "envoy/api/v2/core/config_source.proto";
import "envoy/api/v2/core/protocol.proto";
import "envoy/api/v2/route.proto";
import "envoy/api/v2/scoped_route.proto";
import "envoy/config/filter/accesslog/v2/accesslog.proto";
import "envoy/config/trace/v2/http_tracer.proto";
import "envoy/type/percent.proto";
import "envoy/type/tracing/v2/custom_tag.proto";

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

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

option java_package = "io.envoyproxy.envoy.config.filter.network.http_connection_manager.v2";
option java_outer_classname = "HttpConnectionManagerProto";
option java_multiple_files = true;
option go_package = "github.com/envoyproxy/go-control-plane/envoy/config/filter/network/http_connection_manager/v2;http_connection_managerv2";
option (udpa.annotations.file_migrate).move_to_package =
    "envoy.extensions.filters.network.http_connection_manager.v3";
option (udpa.annotations.file_status).package_version_status = FROZEN;

// [#protodoc-title: HTTP connection manager]
// HTTP connection manager :ref:`configuration overview <config_http_conn_man>`.
// [#extension: envoy.filters.network.http_connection_manager]

// [#next-free-field: 37]
message HttpConnectionManager {
  enum CodecType {
    // For every new connection, the connection manager will determine which
    // codec to use. This mode supports both ALPN for TLS listeners as well as
    // protocol inference for plaintext listeners. If ALPN data is available, it
    // is preferred, otherwise protocol inference is used. In almost all cases,
    // this is the right option to choose for this setting.
    AUTO = 0;

    // The connection manager will assume that the client is speaking HTTP/1.1.
    HTTP1 = 1;

    // The connection manager will assume that the client is speaking HTTP/2
    // (Envoy does not require HTTP/2 to take place over TLS or to use ALPN.
    // Prior knowledge is allowed).
    HTTP2 = 2;

    // [#not-implemented-hide:] QUIC implementation is not production ready yet. Use this enum with
    // caution to prevent accidental execution of QUIC code. I.e. `!= HTTP2` is no longer sufficient
    // to distinguish HTTP1 and HTTP2 traffic.
    HTTP3 = 3;
  }

  enum ServerHeaderTransformation {
    // Overwrite any Server header with the contents of server_name.
    OVERWRITE = 0;

    // If no Server header is present, append Server server_name
    // If a Server header is present, pass it through.
    APPEND_IF_ABSENT = 1;

    // Pass through the value of the server header, and do not append a header
    // if none is present.
    PASS_THROUGH = 2;
  }

  // How to handle the :ref:`config_http_conn_man_headers_x-forwarded-client-cert` (XFCC) HTTP
  // header.
  enum ForwardClientCertDetails {
    // Do not send the XFCC header to the next hop. This is the default value.
    SANITIZE = 0;

    // When the client connection is mTLS (Mutual TLS), forward the XFCC header
    // in the request.
    FORWARD_ONLY = 1;

    // When the client connection is mTLS, append the client certificate
    // information to the request’s XFCC header and forward it.
    APPEND_FORWARD = 2;

    // When the client connection is mTLS, reset the XFCC header with the client
    // certificate information and send it to the next hop.
    SANITIZE_SET = 3;

    // Always forward the XFCC header in the request, regardless of whether the
    // client connection is mTLS.
    ALWAYS_FORWARD_ONLY = 4;
  }

  // [#next-free-field: 10]
  message Tracing {
    enum OperationName {
      // The HTTP listener is used for ingress/incoming requests.
      INGRESS = 0;

      // The HTTP listener is used for egress/outgoing requests.
      EGRESS = 1;
    }

    // The span name will be derived from this field. If
    // :ref:`traffic_direction <envoy_api_field_Listener.traffic_direction>` is
    // specified on the parent listener, then it is used instead of this field.
    //
    // .. attention::
    //  This field has been deprecated in favor of `traffic_direction`.
    OperationName operation_name = 1 [
      deprecated = true,
      (validate.rules).enum = {defined_only: true},
      (envoy.annotations.disallowed_by_default) = true
    ];

    // A list of header names used to create tags for the active span. The header name is used to
    // populate the tag name, and the header value is used to populate the tag value. The tag is
    // created if the specified header name is present in the request's headers.
    //
    // .. attention::
    //  This field has been deprecated in favor of :ref:`custom_tags
    //  <envoy_api_field_config.filter.network.http_connection_manager.v2.HttpConnectionManager.tracing.custom_tags>`.
    repeated string request_headers_for_tags = 2 [deprecated = true];

    // Target percentage of requests managed by this HTTP connection manager that will be force
    // traced if the :ref:`x-client-trace-id <config_http_conn_man_headers_x-client-trace-id>`
    // header is set. This field is a direct analog for the runtime variable
    // 'tracing.client_enabled' in the :ref:`HTTP Connection Manager
    // <config_http_conn_man_runtime>`.
    // Default: 100%
    type.Percent client_sampling = 3;

    // Target percentage of requests managed by this HTTP connection manager that will be randomly
    // selected for trace generation, if not requested by the client or not forced. This field is
    // a direct analog for the runtime variable 'tracing.random_sampling' in the
    // :ref:`HTTP Connection Manager <config_http_conn_man_runtime>`.
    // Default: 100%
    type.Percent random_sampling = 4;

    // Target percentage of requests managed by this HTTP connection manager that will be traced
    // after all other sampling checks have been applied (client-directed, force tracing, random
    // sampling). This field functions as an upper limit on the total configured sampling rate. For
    // instance, setting client_sampling to 100% but overall_sampling to 1% will result in only 1%
    // of client requests with the appropriate headers to be force traced. This field is a direct
    // analog for the runtime variable 'tracing.global_enabled' in the
    // :ref:`HTTP Connection Manager <config_http_conn_man_runtime>`.
    // Default: 100%
    type.Percent overall_sampling = 5;

    // Whether to annotate spans with additional data. If true, spans will include logs for stream
    // events.
    bool verbose = 6;

    // Maximum length of the request path to extract and include in the HttpUrl tag. Used to
    // truncate lengthy request paths to meet the needs of a tracing backend.
    // Default: 256
    google.protobuf.UInt32Value max_path_tag_length = 7;

    // A list of custom tags with unique tag name to create tags for the active span.
    repeated type.tracing.v2.CustomTag custom_tags = 8;

    // Configuration for an external tracing provider.
    // If not specified, no tracing will be performed.
    trace.v2.Tracing.Http provider = 9;
  }

  message InternalAddressConfig {
    // Whether unix socket addresses should be considered internal.
    bool unix_sockets = 1;
  }

  // [#next-free-field: 7]
  message SetCurrentClientCertDetails {
    reserved 2;

    // Whether to forward the subject of the client cert. Defaults to false.
    google.protobuf.BoolValue subject = 1;

    // Whether to forward the entire client cert in URL encoded PEM format. This will appear in the
    // XFCC header comma separated from other values with the value Cert="PEM".
    // Defaults to false.
    bool cert = 3;

    // Whether to forward the entire client cert chain (including the leaf cert) in URL encoded PEM
    // format. This will appear in the XFCC header comma separated from other values with the value
    // Chain="PEM".
    // Defaults to false.
    bool chain = 6;

    // Whether to forward the DNS type Subject Alternative Names of the client cert.
    // Defaults to false.
    bool dns = 4;

    // Whether to forward the URI type Subject Alternative Name of the client cert. Defaults to
    // false.
    bool uri = 5;
  }

  // The configuration for HTTP upgrades.
  // For each upgrade type desired, an UpgradeConfig must be added.
  //
  // .. warning::
  //
  //    The current implementation of upgrade headers does not handle
  //    multi-valued upgrade headers. Support for multi-valued headers may be
  //    added in the future if needed.
  //
  // .. warning::
  //    The current implementation of upgrade headers does not work with HTTP/2
  //    upstreams.
  message UpgradeConfig {
    // The case-insensitive name of this upgrade, e.g. "websocket".
    // For each upgrade type present in upgrade_configs, requests with
    // Upgrade: [upgrade_type]
    // will be proxied upstream.
    string upgrade_type = 1;

    // If present, this represents the filter chain which will be created for
    // this type of upgrade. If no filters are present, the filter chain for
    // HTTP connections will be used for this upgrade type.
    repeated HttpFilter filters = 2;

    // Determines if upgrades are enabled or disabled by default. Defaults to true.
    // This can be overridden on a per-route basis with :ref:`cluster
    // <envoy_api_field_route.RouteAction.upgrade_configs>` as documented in the
    // :ref:`upgrade documentation <arch_overview_upgrades>`.
    google.protobuf.BoolValue enabled = 3;
  }

  reserved 27;

  // Supplies the type of codec that the connection manager should use.
  CodecType codec_type = 1 [(validate.rules).enum = {defined_only: true}];

  // The human readable prefix to use when emitting statistics for the
  // connection manager. See the :ref:`statistics documentation <config_http_conn_man_stats>` for
  // more information.
  string stat_prefix = 2 [(validate.rules).string = {min_bytes: 1}];

  oneof route_specifier {
    option (validate.required) = true;

    // The connection manager’s route table will be dynamically loaded via the RDS API.
    Rds rds = 3;

    // The route table for the connection manager is static and is specified in this property.
    api.v2.RouteConfiguration route_config = 4;

    // A route table will be dynamically assigned to each request based on request attributes
    // (e.g., the value of a header). The "routing scopes" (i.e., route tables) and "scope keys" are
    // specified in this message.
    ScopedRoutes scoped_routes = 31;
  }

  // A list of individual HTTP filters that make up the filter chain for
  // requests made to the connection manager. :ref:`Order matters <arch_overview_http_filters_ordering>`
  // as the filters are processed sequentially as request events happen.
  repeated HttpFilter http_filters = 5;

  // Whether the connection manager manipulates the :ref:`config_http_conn_man_headers_user-agent`
  // and :ref:`config_http_conn_man_headers_downstream-service-cluster` headers. See the linked
  // documentation for more information. Defaults to false.
  google.protobuf.BoolValue add_user_agent = 6;

  // Presence of the object defines whether the connection manager
  // emits :ref:`tracing <arch_overview_tracing>` data to the :ref:`configured tracing provider
  // <envoy_api_msg_config.trace.v2.Tracing>`.
  Tracing tracing = 7;

  // Additional settings for HTTP requests handled by the connection manager. These will be
  // applicable to both HTTP1 and HTTP2 requests.
  api.v2.core.HttpProtocolOptions common_http_protocol_options = 35;

  // Additional HTTP/1 settings that are passed to the HTTP/1 codec.
  api.v2.core.Http1ProtocolOptions http_protocol_options = 8;

  // Additional HTTP/2 settings that are passed directly to the HTTP/2 codec.
  api.v2.core.Http2ProtocolOptions http2_protocol_options = 9;

  // An optional override that the connection manager will write to the server
  // header in responses. If not set, the default is *envoy*.
  string server_name = 10;

  // Defines the action to be applied to the Server header on the response path.
  // By default, Envoy will overwrite the header with the value specified in
  // server_name.
  ServerHeaderTransformation server_header_transformation = 34
      [(validate.rules).enum = {defined_only: true}];

  // The maximum request headers size for incoming connections.
  // If unconfigured, the default max request headers allowed is 60 KiB.
  // Requests that exceed this limit will receive a 431 response.
  google.protobuf.UInt32Value max_request_headers_kb = 29
      [(validate.rules).uint32 = {lte: 8192 gt: 0}];

  // The idle timeout for connections managed by the connection manager. The
  // idle timeout is defined as the period in which there are no active
  // requests. If not set, there is no idle timeout. When the idle timeout is
  // reached the connection will be closed. If the connection is an HTTP/2
  // connection a drain sequence will occur prior to closing the connection.
  // This field is deprecated. Use :ref:`idle_timeout
  // <envoy_api_field_config.filter.network.http_connection_manager.v2.HttpConnectionManager.common_http_protocol_options>`
  // instead.
  google.protobuf.Duration idle_timeout = 11
      [deprecated = true, (envoy.annotations.disallowed_by_default) = true];

  // The stream idle timeout for connections managed by the connection manager.
  // If not specified, this defaults to 5 minutes. The default value was selected
  // so as not to interfere with any smaller configured timeouts that may have
  // existed in configurations prior to the introduction of this feature, while
  // introducing robustness to TCP connections that terminate without a FIN.
  //
  // This idle timeout applies to new streams and is overridable by the
  // :ref:`route-level idle_timeout
  // <envoy_api_field_route.RouteAction.idle_timeout>`. Even on a stream in
  // which the override applies, prior to receipt of the initial request
  // headers, the :ref:`stream_idle_timeout
  // <envoy_api_field_config.filter.network.http_connection_manager.v2.HttpConnectionManager.stream_idle_timeout>`
  // applies. Each time an encode/decode event for headers or data is processed
  // for the stream, the timer will be reset. If the timeout fires, the stream
  // is terminated with a 408 Request Timeout error code if no upstream response
  // header has been received, otherwise a stream reset occurs.
  //
  // This timeout also specifies the amount of time that Envoy will wait for the peer to open enough
  // window to write any remaining stream data once the entirety of stream data (local end stream is
  // true) has been buffered pending available window. In other words, this timeout defends against
  // a peer that does not release enough window to completely write the stream, even though all
  // data has been proxied within available flow control windows. If the timeout is hit in this
  // case, the :ref:`tx_flush_timeout <config_http_conn_man_stats_per_codec>` counter will be
  // incremented. Note that :ref:`max_stream_duration
  // <envoy_api_field_core.HttpProtocolOptions.max_stream_duration>` does not apply to this corner
  // case.
  //
  // Note that it is possible to idle timeout even if the wire traffic for a stream is non-idle, due
  // to the granularity of events presented to the connection manager. For example, while receiving
  // very large request headers, it may be the case that there is traffic regularly arriving on the
  // wire while the connection manage is only able to observe the end-of-headers event, hence the
  // stream may still idle timeout.
  //
  // A value of 0 will completely disable the connection manager stream idle
  // timeout, although per-route idle timeout overrides will continue to apply.
  google.protobuf.Duration stream_idle_timeout = 24;

  // The amount of time that Envoy will wait for the entire request to be received.
  // The timer is activated when the request is initiated, and is disarmed when the last byte of the
  // request is sent upstream (i.e. all decoding filters have processed the request), OR when the
  // response is initiated. If not specified or set to 0, this timeout is disabled.
  google.protobuf.Duration request_timeout = 28;

  // The time that Envoy will wait between sending an HTTP/2 “shutdown
  // notification” (GOAWAY frame with max stream ID) and a final GOAWAY frame.
  // This is used so that Envoy provides a grace period for new streams that
  // race with the final GOAWAY frame. During this grace period, Envoy will
  // continue to accept new streams. After the grace period, a final GOAWAY
  // frame is sent and Envoy will start refusing new streams. Draining occurs
  // both when a connection hits the idle timeout or during general server
  // draining. The default grace period is 5000 milliseconds (5 seconds) if this
  // option is not specified.
  google.protobuf.Duration drain_timeout = 12;

  // The delayed close timeout is for downstream connections managed by the HTTP connection manager.
  // It is defined as a grace period after connection close processing has been locally initiated
  // during which Envoy will wait for the peer to close (i.e., a TCP FIN/RST is received by Envoy
  // from the downstream connection) prior to Envoy closing the socket associated with that
  // connection.
  // NOTE: This timeout is enforced even when the socket associated with the downstream connection
  // is pending a flush of the write buffer. However, any progress made writing data to the socket
  // will restart the timer associated with this timeout. This means that the total grace period for
  // a socket in this state will be
  // <total_time_waiting_for_write_buffer_flushes>+<delayed_close_timeout>.
  //
  // Delaying Envoy's connection close and giving the peer the opportunity to initiate the close
  // sequence mitigates a race condition that exists when downstream clients do not drain/process
  // data in a connection's receive buffer after a remote close has been detected via a socket
  // write(). This race leads to such clients failing to process the response code sent by Envoy,
  // which could result in erroneous downstream processing.
  //
  // If the timeout triggers, Envoy will close the connection's socket.
  //
  // The default timeout is 1000 ms if this option is not specified.
  //
  // .. NOTE::
  //    To be useful in avoiding the race condition described above, this timeout must be set
  //    to *at least* <max round trip time expected between clients and Envoy>+<100ms to account for
  //    a reasonable "worst" case processing time for a full iteration of Envoy's event loop>.
  //
  // .. WARNING::
  //    A value of 0 will completely disable delayed close processing. When disabled, the downstream
  //    connection's socket will be closed immediately after the write flush is completed or will
  //    never close if the write flush does not complete.
  google.protobuf.Duration delayed_close_timeout = 26;

  // Configuration for :ref:`HTTP access logs <arch_overview_access_logs>`
  // emitted by the connection manager.
  repeated accesslog.v2.AccessLog access_log = 13;

  // If set to true, the connection manager will use the real remote address
  // of the client connection when determining internal versus external origin and manipulating
  // various headers. If set to false or absent, the connection manager will use the
  // :ref:`config_http_conn_man_headers_x-forwarded-for` HTTP header. See the documentation for
  // :ref:`config_http_conn_man_headers_x-forwarded-for`,
  // :ref:`config_http_conn_man_headers_x-envoy-internal`, and
  // :ref:`config_http_conn_man_headers_x-envoy-external-address` for more information.
  google.protobuf.BoolValue use_remote_address = 14;

  // The number of additional ingress proxy hops from the right side of the
  // :ref:`config_http_conn_man_headers_x-forwarded-for` HTTP header to trust when
  // determining the origin client's IP address. The default is zero if this option
  // is not specified. See the documentation for
  // :ref:`config_http_conn_man_headers_x-forwarded-for` for more information.
  uint32 xff_num_trusted_hops = 19;

  // Configures what network addresses are considered internal for stats and header sanitation
  // purposes. If unspecified, only RFC1918 IP addresses will be considered internal.
  // See the documentation for :ref:`config_http_conn_man_headers_x-envoy-internal` for more
  // information about internal/external addresses.
  InternalAddressConfig internal_address_config = 25;

  // If set, Envoy will not append the remote address to the
  // :ref:`config_http_conn_man_headers_x-forwarded-for` HTTP header. This may be used in
  // conjunction with HTTP filters that explicitly manipulate XFF after the HTTP connection manager
  // has mutated the request headers. While :ref:`use_remote_address
  // <envoy_api_field_config.filter.network.http_connection_manager.v2.HttpConnectionManager.use_remote_address>`
  // will also suppress XFF addition, it has consequences for logging and other
  // Envoy uses of the remote address, so *skip_xff_append* should be used
  // when only an elision of XFF addition is intended.
  bool skip_xff_append = 21;

  // Via header value to append to request and response headers. If this is
  // empty, no via header will be appended.
  string via = 22;

  // Whether the connection manager will generate the :ref:`x-request-id
  // <config_http_conn_man_headers_x-request-id>` header if it does not exist. This defaults to
  // true. Generating a random UUID4 is expensive so in high throughput scenarios where this feature
  // is not desired it can be disabled.
  google.protobuf.BoolValue generate_request_id = 15;

  // Whether the connection manager will keep the :ref:`x-request-id
  // <config_http_conn_man_headers_x-request-id>` header if passed for a request that is edge
  // (Edge request is the request from external clients to front Envoy) and not reset it, which
  // is the current Envoy behaviour. This defaults to false.
  bool preserve_external_request_id = 32;

  // How to handle the :ref:`config_http_conn_man_headers_x-forwarded-client-cert` (XFCC) HTTP
  // header.
  ForwardClientCertDetails forward_client_cert_details = 16
      [(validate.rules).enum = {defined_only: true}];

  // This field is valid only when :ref:`forward_client_cert_details
  // <envoy_api_field_config.filter.network.http_connection_manager.v2.HttpConnectionManager.forward_client_cert_details>`
  // is APPEND_FORWARD or SANITIZE_SET and the client connection is mTLS. It specifies the fields in
  // the client certificate to be forwarded. Note that in the
  // :ref:`config_http_conn_man_headers_x-forwarded-client-cert` header, *Hash* is always set, and
  // *By* is always set when the client certificate presents the URI type Subject Alternative Name
  // value.
  SetCurrentClientCertDetails set_current_client_cert_details = 17;

  // If proxy_100_continue is true, Envoy will proxy incoming "Expect:
  // 100-continue" headers upstream, and forward "100 Continue" responses
  // downstream. If this is false or not set, Envoy will instead strip the
  // "Expect: 100-continue" header, and send a "100 Continue" response itself.
  bool proxy_100_continue = 18;

  // If
  // :ref:`use_remote_address
  // <envoy_api_field_config.filter.network.http_connection_manager.v2.HttpConnectionManager.use_remote_address>`
  // is true and represent_ipv4_remote_address_as_ipv4_mapped_ipv6 is true and the remote address is
  // an IPv4 address, the address will be mapped to IPv6 before it is appended to *x-forwarded-for*.
  // This is useful for testing compatibility of upstream services that parse the header value. For
  // example, 50.0.0.1 is represented as ::FFFF:50.0.0.1. See `IPv4-Mapped IPv6 Addresses
  // <https://tools.ietf.org/html/rfc4291#section-2.5.5.2>`_ for details. This will also affect the
  // :ref:`config_http_conn_man_headers_x-envoy-external-address` header. See
  // :ref:`http_connection_manager.represent_ipv4_remote_address_as_ipv4_mapped_ipv6
  // <config_http_conn_man_runtime_represent_ipv4_remote_address_as_ipv4_mapped_ipv6>` for runtime
  // control.
  // [#not-implemented-hide:]
  bool represent_ipv4_remote_address_as_ipv4_mapped_ipv6 = 20;

  repeated UpgradeConfig upgrade_configs = 23;

  // Should paths be normalized according to RFC 3986 before any processing of
  // requests by HTTP filters or routing? This affects the upstream *:path* header
  // as well. For paths that fail this check, Envoy will respond with 400 to
  // paths that are malformed. This defaults to false currently but will default
  // true in the future. When not specified, this value may be overridden by the
  // runtime variable
  // :ref:`http_connection_manager.normalize_path<config_http_conn_man_runtime_normalize_path>`.
  // See `Normalization and Comparison <https://tools.ietf.org/html/rfc3986#section-6>`_
  // for details of normalization.
  // Note that Envoy does not perform
  // `case normalization <https://tools.ietf.org/html/rfc3986#section-6.2.2.1>`_
  google.protobuf.BoolValue normalize_path = 30;

  // Determines if adjacent slashes in the path are merged into one before any processing of
  // requests by HTTP filters or routing. This affects the upstream *:path* header as well. Without
  // setting this option, incoming requests with path `//dir///file` will not match against route
  // with `prefix` match set to `/dir`. Defaults to `false`. Note that slash merging is not part of
  // `HTTP spec <https://tools.ietf.org/html/rfc3986>`_ and is provided for convenience.
  bool merge_slashes = 33;

  // The configuration of the request ID extension. This includes operations such as
  // generation, validation, and associated tracing operations.
  //
  // If not set, Envoy uses the default UUID-based behavior:
  //
  // 1. Request ID is propagated using *x-request-id* header.
  //
  // 2. Request ID is a universally unique identifier (UUID).
  //
  // 3. Tracing decision (sampled, forced, etc) is set in 14th byte of the UUID.
  RequestIDExtension request_id_extension = 36;
}

message Rds {
  // Configuration source specifier for RDS.
  api.v2.core.ConfigSource config_source = 1 [(validate.rules).message = {required: true}];

  // The name of the route configuration. This name will be passed to the RDS
  // API. This allows an Envoy configuration with multiple HTTP listeners (and
  // associated HTTP connection manager filters) to use different route
  // configurations.
  string route_config_name = 2 [(validate.rules).string = {min_bytes: 1}];
}

// This message is used to work around the limitations with 'oneof' and repeated fields.
message ScopedRouteConfigurationsList {
  repeated api.v2.ScopedRouteConfiguration scoped_route_configurations = 1
      [(validate.rules).repeated = {min_items: 1}];
}

// [#next-free-field: 6]
message ScopedRoutes {
  // Specifies the mechanism for constructing "scope keys" based on HTTP request attributes. These
  // keys are matched against a set of :ref:`Key<envoy_api_msg_ScopedRouteConfiguration.Key>`
  // objects assembled from :ref:`ScopedRouteConfiguration<envoy_api_msg_ScopedRouteConfiguration>`
  // messages distributed via SRDS (the Scoped Route Discovery Service) or assigned statically via
  // :ref:`scoped_route_configurations_list<envoy_api_field_config.filter.network.http_connection_manager.v2.ScopedRoutes.scoped_route_configurations_list>`.
  //
  // Upon receiving a request's headers, the Router will build a key using the algorithm specified
  // by this message. This key will be used to look up the routing table (i.e., the
  // :ref:`RouteConfiguration<envoy_api_msg_RouteConfiguration>`) to use for the request.
  message ScopeKeyBuilder {
    // Specifies the mechanism for constructing key fragments which are composed into scope keys.
    message FragmentBuilder {
      // Specifies how the value of a header should be extracted.
      // The following example maps the structure of a header to the fields in this message.
      //
      // .. code::
      //
      //              <0> <1>   <-- index
      //    X-Header: a=b;c=d
      //    |         || |
      //    |         || \----> <element_separator>
      //    |         ||
      //    |         |\----> <element.separator>
      //    |         |
      //    |         \----> <element.key>
      //    |
      //    \----> <name>
      //
      //    Each 'a=b' key-value pair constitutes an 'element' of the header field.
      message HeaderValueExtractor {
        // Specifies a header field's key value pair to match on.
        message KvElement {
          // The separator between key and value (e.g., '=' separates 'k=v;...').
          // If an element is an empty string, the element is ignored.
          // If an element contains no separator, the whole element is parsed as key and the
          // fragment value is an empty string.
          // If there are multiple values for a matched key, the first value is returned.
          string separator = 1 [(validate.rules).string = {min_bytes: 1}];

          // The key to match on.
          string key = 2 [(validate.rules).string = {min_bytes: 1}];
        }

        // The name of the header field to extract the value from.
        //
        // .. note::
        //
        //   If the header appears multiple times only the first value is used.
        string name = 1 [(validate.rules).string = {min_bytes: 1}];

        // The element separator (e.g., ';' separates 'a;b;c;d').
        // Default: empty string. This causes the entirety of the header field to be extracted.
        // If this field is set to an empty string and 'index' is used in the oneof below, 'index'
        // must be set to 0.
        string element_separator = 2;

        oneof extract_type {
          // Specifies the zero based index of the element to extract.
          // Note Envoy concatenates multiple values of the same header key into a comma separated
          // string, the splitting always happens after the concatenation.
          uint32 index = 3;

          // Specifies the key value pair to extract the value from.
          KvElement element = 4;
        }
      }

      oneof type {
        option (validate.required) = true;

        // Specifies how a header field's value should be extracted.
        HeaderValueExtractor header_value_extractor = 1;
      }
    }

    // The final(built) scope key consists of the ordered union of these fragments, which are compared in order with the
    // fragments of a :ref:`ScopedRouteConfiguration<envoy_api_msg_ScopedRouteConfiguration>`.
    // A missing fragment during comparison will make the key invalid, i.e., the computed key doesn't match any key.
    repeated FragmentBuilder fragments = 1 [(validate.rules).repeated = {min_items: 1}];
  }

  // The name assigned to the scoped routing configuration.
  string name = 1 [(validate.rules).string = {min_bytes: 1}];

  // The algorithm to use for constructing a scope key for each request.
  ScopeKeyBuilder scope_key_builder = 2 [(validate.rules).message = {required: true}];

  // Configuration source specifier for RDS.
  // This config source is used to subscribe to RouteConfiguration resources specified in
  // ScopedRouteConfiguration messages.
  api.v2.core.ConfigSource rds_config_source = 3 [(validate.rules).message = {required: true}];

  oneof config_specifier {
    option (validate.required) = true;

    // The set of routing scopes corresponding to the HCM. A scope is assigned to a request by
    // matching a key constructed from the request's attributes according to the algorithm specified
    // by the
    // :ref:`ScopeKeyBuilder<envoy_api_msg_config.filter.network.http_connection_manager.v2.ScopedRoutes.ScopeKeyBuilder>`
    // in this message.
    ScopedRouteConfigurationsList scoped_route_configurations_list = 4;

    // The set of routing scopes associated with the HCM will be dynamically loaded via the SRDS
    // API. A scope is assigned to a request by matching a key constructed from the request's
    // attributes according to the algorithm specified by the
    // :ref:`ScopeKeyBuilder<envoy_api_msg_config.filter.network.http_connection_manager.v2.ScopedRoutes.ScopeKeyBuilder>`
    // in this message.
    ScopedRds scoped_rds = 5;
  }
}

message ScopedRds {
  // Configuration source specifier for scoped RDS.
  api.v2.core.ConfigSource scoped_rds_config_source = 1
      [(validate.rules).message = {required: true}];
}

message HttpFilter {
  reserved 3;

  // The name of the filter to instantiate. The name must match a
  // :ref:`supported filter <config_http_filters>`.
  string name = 1 [(validate.rules).string = {min_bytes: 1}];

  // Filter specific configuration which depends on the filter being instantiated. See the supported
  // filters for further documentation.
  oneof config_type {
    google.protobuf.Struct config = 2 [deprecated = true];

    google.protobuf.Any typed_config = 4;
  }
}

message RequestIDExtension {
  // Request ID extension specific configuration.
  google.protobuf.Any typed_config = 1;
}
