feat(routes) add annotations for headers

Add annotation support for headers. The annotation is in the form
"konghq.com/headers/example: value1,value2", where the portion of the
annoation name after "konghq.com/headers" ("example") is the
header name and the value is a CSV of header values.

internal/annotations/annotations.go

@@ -60,6 +60,7 @@ const (
 	WriteTimeoutKey      = "/write-timeout"
 	ReadTimeoutKey       = "/read-timeout"
 	RetriesKey           = "/retries"
+	HeadersKey           = "/headers"
 
 	// GatewayClassUnmanagedAnnotationSuffix is an annotation used on a Gateway resource to
 	// indicate that the GatewayClass should be reconciled according to unmanaged
@@ -293,6 +294,25 @@ func ExtractRetries(anns map[string]string) (string, bool) {
 	return val, true
 }
 
+// ExtractHeaders extracts the parsed headerr annotations values. It returns a map of header names to slices of values.
+func ExtractHeaders(anns map[string]string) (map[string][]string, bool) {
+	headers := make(map[string][]string)
+	prefix := AnnotationPrefix + HeadersKey + "/"
+	for key, val := range anns {
+		if strings.HasPrefix(key, prefix) {
+			header := strings.TrimPrefix(key, prefix)
+			if len(header) == 0 || len(val) == 0 {
+				continue
+			}
+			headers[header] = strings.Split(val, ",")
+		}
+	}
+	if len(headers) == 0 {
+		return headers, false
+	}
+	return headers, true
+}
+
 // ExtractUnmanagedGatewayClassMode extracts the value of the unmanaged gateway
 // mode annotation.
 func ExtractUnmanagedGatewayClassMode(anns map[string]string) string {

internal/annotations/annotations_test.go

@@ -836,3 +836,61 @@ func TestExtractRetries(t *testing.T) {
 		})
 	}
 }
+
+func TestExtractHeaders(t *testing.T) {
+	type args struct {
+		anns map[string]string
+	}
+	tests := []struct {
+		name string
+		args args
+		want map[string][]string
+	}{
+		{
+			name: "empty",
+			want: map[string][]string{},
+		},
+		{
+			name: "non-empty",
+			args: args{
+				anns: map[string]string{
+					"konghq.com/headers/foo": "foo",
+				},
+			},
+			want: map[string][]string{"foo": {"foo"}},
+		},
+		{
+			name: "no separator",
+			args: args{
+				anns: map[string]string{
+					"konghq.com/headersfoo": "foo",
+				},
+			},
+			want: map[string][]string{},
+		},
+		{
+			name: "no header name",
+			args: args{
+				anns: map[string]string{
+					"konghq.com/headers/": "foo",
+				},
+			},
+			want: map[string][]string{},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, ok := ExtractHeaders(tt.args.anns)
+			if len(tt.want) == 0 {
+				assert.False(t, ok)
+			} else {
+				assert.True(t, ok)
+			}
+			for key, val := range tt.want {
+				actual, ok := got[key]
+				assert.True(t, ok)
+				assert.Equal(t, val, actual)
+			}
+		})
+	}
+}

internal/dataplane/kongstate/route.go

@@ -228,6 +228,7 @@ func (r *Route) overrideByAnnotation(log logrus.FieldLogger) {
 	r.overrideRequestBuffering(log, r.Ingress.Annotations)
 	r.overrideResponseBuffering(log, r.Ingress.Annotations)
 	r.overrideHosts(log, r.Ingress.Annotations)
+	r.overrideHeaders(r.Ingress.Annotations)
 }
 
 // override sets Route fields by KongIngress first, then by annotation.
@@ -405,3 +406,11 @@ func (r *Route) overrideHosts(log logrus.FieldLogger, anns map[string]string) {
 
 	r.Hosts = hosts
 }
+
+func (r *Route) overrideHeaders(anns map[string]string) {
+	headers, exists := annotations.ExtractHeaders(anns)
+	if !exists {
+		return
+	}
+	r.Headers = headers
+}

internal/dataplane/kongstate/route_test.go

@@ -1055,3 +1055,85 @@ func TestOverrideHosts(t *testing.T) {
 		})
 	}
 }
+
+func TestOverrideHeaders(t *testing.T) {
+	type args struct {
+		route Route
+		anns  map[string]string
+	}
+	tests := []struct {
+		name string
+		args args
+		want Route
+	}{
+		{name: "basic empty route"},
+		{
+			name: "single header single value",
+			args: args{
+				anns: map[string]string{
+					"konghq.com/headers/x-example": "example",
+				},
+			},
+			want: Route{
+				Route: kong.Route{
+					Headers: map[string][]string{"x-example": {"example"}},
+				},
+			},
+		},
+		{
+			name: "single header multi value",
+			args: args{
+				anns: map[string]string{
+					"konghq.com/headers/x-example": "foo,bar",
+				},
+			},
+			want: Route{
+				Route: kong.Route{
+					Headers: map[string][]string{"x-example": {"foo", "bar"}},
+				},
+			},
+		},
+		{
+			name: "multi header single value",
+			args: args{
+				anns: map[string]string{
+					"konghq.com/headers/x-foo": "example",
+					"konghq.com/headers/x-bar": "example",
+				},
+			},
+			want: Route{
+				Route: kong.Route{
+					Headers: map[string][]string{
+						"x-foo": {"example"},
+						"x-bar": {"example"},
+					},
+				},
+			},
+		},
+		{
+			name: "multi header multi value",
+			args: args{
+				anns: map[string]string{
+					"konghq.com/headers/x-foo": "foo,bar",
+					"konghq.com/headers/x-bar": "bar,baz",
+				},
+			},
+			want: Route{
+				Route: kong.Route{
+					Headers: map[string][]string{
+						"x-foo": {"foo", "bar"},
+						"x-bar": {"bar", "baz"},
+					},
+				},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tt.args.route.overrideHeaders(tt.args.anns)
+			if !reflect.DeepEqual(tt.args.route, tt.want) {
+				t.Errorf("overrideHeaders() got = %v, want %v", tt.args.route, tt.want)
+			}
+		})
+	}
+}