implement direct response

config/constants.go

@@ -14,13 +14,13 @@ const (
 )
 
 var (
-	errKeysMustBeStrings          = errors.New("cannot convert nested map: all keys must be strings")
-	errZeroWeight                 = errors.New("zero load balancing weight not permitted")
-	errEndpointWeightsSpec        = errors.New("either no weights should be provided, or all endpoints must have non-zero weight specified")
-	errHostnameMustBeSpecified    = errors.New("endpoint hostname must be specified")
-	errSchemeMustBeSpecified      = errors.New("url scheme must be provided")
-	errEmptyUrls                  = errors.New("url list is empty")
-	errEitherToOrRedirectRequired = errors.New("policy should have either `to` or `redirect` defined")
+	errKeysMustBeStrings                    = errors.New("cannot convert nested map: all keys must be strings")
+	errZeroWeight                           = errors.New("zero load balancing weight not permitted")
+	errEndpointWeightsSpec                  = errors.New("either no weights should be provided, or all endpoints must have non-zero weight specified")
+	errHostnameMustBeSpecified              = errors.New("endpoint hostname must be specified")
+	errSchemeMustBeSpecified                = errors.New("url scheme must be provided")
+	errEmptyUrls                            = errors.New("url list is empty")
+	errEitherToOrRedirectOrResponseRequired = errors.New("policy should have either `to` or `redirect` or `response` defined")
 )
 
 var protoPartial = protojson.UnmarshalOptions{AllowPartial: true, DiscardUnknown: true}

config/envoyconfig/routes.go

@@ -282,6 +282,9 @@ func (b *Builder) buildRouteForPolicyAndMatch(
 			return nil, err
 		}
 		route.Action = &envoy_config_route_v3.Route_Redirect{Redirect: action}
+	} else if policy.Response != nil {
+		action := b.buildPolicyRouteDirectResponseAction(policy.Response)
+		route.Action = &envoy_config_route_v3.Route_DirectResponse{DirectResponse: action}
 	} else {
 		action, err := b.buildPolicyRouteRouteAction(cfg.Options, policy)
 		if err != nil {
@@ -343,6 +346,17 @@ func (b *Builder) buildRouteForPolicyAndMatch(
 	return route, nil
 }
 
+func (b *Builder) buildPolicyRouteDirectResponseAction(r *config.DirectResponse) *envoy_config_route_v3.DirectResponseAction {
+	return &envoy_config_route_v3.DirectResponseAction{
+		Status: uint32(r.Status),
+		Body: &envoy_config_core_v3.DataSource{
+			Specifier: &envoy_config_core_v3.DataSource_InlineString{
+				InlineString: r.Body,
+			},
+		},
+	}
+}
+
 func (b *Builder) buildPolicyRouteRedirectAction(r *config.PolicyRedirect) (*envoy_config_route_v3.RedirectAction, error) {
 	action := &envoy_config_route_v3.RedirectAction{}
 	switch {

config/policy.go

@@ -28,8 +28,9 @@ import (
 type Policy struct {
 	ID string `mapstructure:"-" yaml:"-" json:"-"`
 
-	From string       `mapstructure:"from" yaml:"from"`
-	To   WeightedURLs `mapstructure:"to" yaml:"to"`
+	From     string          `mapstructure:"from" yaml:"from"`
+	To       WeightedURLs    `mapstructure:"to" yaml:"to"`
+	Response *DirectResponse `mapstructure:"response" yaml:"response,omitempty" json:"response,omitempty"`
 
 	// LbWeights are optional load balancing weights applied to endpoints specified in To
 	// this field exists for compatibility with mapstructure
@@ -213,6 +214,12 @@ type PolicyRedirect struct {
 	StripQuery     *bool   `mapstructure:"strip_query" yaml:"strip_query,omitempty" json:"strip_query,omitempty"`
 }
 
+// A DirectResponse is the response to an HTTP request.
+type DirectResponse struct {
+	Status int    `mapstructure:"status" yaml:"status,omitempty" json:"status,omitempty"`
+	Body   string `mapstructure:"body" yaml:"body,omitempty" json:"body,omitempty"`
+}
+
 // NewPolicyFromProto creates a new Policy from a protobuf policy config route.
 func NewPolicyFromProto(pb *configpb.Route) (*Policy, error) {
 	var timeout *time.Duration
@@ -446,8 +453,8 @@ func (p *Policy) Validate() error {
 			source.String())
 	}
 
-	if len(p.To) == 0 && p.Redirect == nil {
-		return errEitherToOrRedirectRequired
+	if len(p.To) == 0 && p.Redirect == nil && p.Response == nil {
+		return errEitherToOrRedirectOrResponseRequired
 	}
 
 	for _, u := range p.To {
@@ -567,8 +574,11 @@ func (p *Policy) RouteID() (uint64, error) {
 		id.To = dst
 	} else if p.Redirect != nil {
 		id.Redirect = p.Redirect
+	} else if p.Response != nil {
+		id.DirectResponseStatus = p.Response.Status
+		id.DirectResponseBody = p.Response.Body
 	} else {
-		return 0, errEitherToOrRedirectRequired
+		return 0, errEitherToOrRedirectOrResponseRequired
 	}
 
 	return hashutil.Hash(id)
@@ -679,12 +689,14 @@ func (p *Policy) GetPassIdentityHeaders(options *Options) bool {
 }
 
 type routeID struct {
-	From     string
-	To       []string
-	Prefix   string
-	Path     string
-	Regex    string
-	Redirect *PolicyRedirect
+	From                 string
+	To                   []string
+	Prefix               string
+	Path                 string
+	Regex                string
+	Redirect             *PolicyRedirect
+	DirectResponseStatus int
+	DirectResponseBody   string
 }
 
 /*

pkg/grpc/config/config.proto

@@ -33,12 +33,18 @@ message RouteRedirect {
   optional bool strip_query = 8;
 }
 
-// Next ID: 62.
+message RouteDirectResponse {
+  uint32 status = 1;
+  string body = 2;
+}
+
+// Next ID: 63.
 message Route {
   string name = 1;
 
   string from = 2;
   repeated string to = 3;
+  RouteDirectResponse response = 62;
 
   // https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/endpoint/v3/endpoint_components.proto#envoy-v3-api-msg-config-endpoint-v3-lbendpoint
   // optional load balancing weights assigned to upstream servers defined in TO