proxy: set zero content length for default response

proxy/context.go

@@ -1,7 +1,6 @@
 package proxy
 
 import (
-	"bytes"
 	stdlibcontext "context"
 	"errors"
 	"io"
@@ -62,15 +61,15 @@ type noopFlushedResponseWriter struct {
 	ignoredHeader http.Header
 }
 
-func defaultBody() io.ReadCloser {
-	return io.NopCloser(&bytes.Buffer{})
+func noBody() io.ReadCloser {
+	return http.NoBody
 }
 
 func defaultResponse(r *http.Request) *http.Response {
 	return &http.Response{
 		StatusCode: http.StatusNotFound,
 		Header:     make(http.Header),
-		Body:       defaultBody(),
+		Body:       noBody(),
 		Request:    r,
 	}
 }
@@ -89,7 +88,7 @@ func cloneRequestMetadata(r *http.Request) *http.Request {
 		ProtoMinor:       r.ProtoMinor,
 		Header:           cloneHeader(r.Header),
 		Trailer:          cloneHeader(r.Trailer),
-		Body:             defaultBody(),
+		Body:             noBody(),
 		ContentLength:    r.ContentLength,
 		TransferEncoding: r.TransferEncoding,
 		Close:            r.Close,
@@ -109,7 +108,7 @@ func cloneResponseMetadata(r *http.Response) *http.Response {
 		ProtoMinor:       r.ProtoMinor,
 		Header:           cloneHeader(r.Header),
 		Trailer:          cloneHeader(r.Trailer),
-		Body:             defaultBody(),
+		Body:             noBody(),
 		ContentLength:    r.ContentLength,
 		TransferEncoding: r.TransferEncoding,
 		Close:            r.Close,
@@ -180,7 +179,7 @@ func (c *context) ensureDefaultResponse() {
 	}
 
 	if c.response.Body == nil {
-		c.response.Body = defaultBody()
+		c.response.Body = noBody()
 	}
 }
 
@@ -235,7 +234,7 @@ func (c *context) Serve(r *http.Response) {
 	}
 
 	if r.Body == nil {
-		r.Body = defaultBody()
+		r.Body = noBody()
 	}
 
 	c.servedWithResponse = true

proxy/defaultresponse_test.go

@@ -0,0 +1,26 @@
+package proxy_test
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/zalando/skipper/eskip"
+	"github.com/zalando/skipper/proxy/proxytest"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDefaultResponse(t *testing.T) {
+	p := proxytest.Config{
+		Routes: eskip.MustParse(`* -> <shunt>`),
+	}.Create()
+	defer p.Close()
+
+	rsp, body, err := p.Client().GetBody(p.URL)
+	require.NoError(t, err)
+
+	assert.Equal(t, http.StatusNotFound, rsp.StatusCode)
+	assert.Len(t, body, 0)
+	assert.Equal(t, "0", rsp.Header.Get("Content-Length"))
+}

proxy/proxy.go

@@ -958,8 +958,7 @@ func (p *Proxy) rejectBackend(ctx *context, req *http.Request) (*http.Response,
 		if !p.limiters.Get(limit.Settings).Allow(req.Context(), s) {
 			return &http.Response{
 				StatusCode: limit.StatusCode,
-				Header:     http.Header{"Content-Length": []string{"0"}},
-				Body:       io.NopCloser(&bytes.Buffer{}),
+				Body:       noBody(),
 			}, true
 		}
 	}
@@ -1211,6 +1210,9 @@ func (p *Proxy) serveResponse(ctx *context) {
 	start := time.Now()
 	p.tracing.logStreamEvent(ctx.proxySpan, StreamHeadersEvent, StartEvent)
 	copyHeader(ctx.responseWriter.Header(), ctx.response.Header)
+	if ctx.response.Body == noBody() {
+		ctx.responseWriter.Header()["Content-Length"] = []string{"0"}
+	}
 
 	if err := ctx.Request().Context().Err(); err != nil {
 		// deadline exceeded or canceled in stdlib, client closed request