net/http: Content-Type is set even with empty body #20784

tw4452852 · 2017-06-24T05:22:05Z

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (`go version`)?

go version devel +1948b7f Wed May 31 10:28:05 2017 +0000 linux/amd64

What operating system and processor architecture are you using (`go env`)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/tw/golib"
GORACE=""
GOROOT="/home/tw/goroot"
GOTOOLDIR="/home/tw/goroot/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build555764928=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config

What did you do?

package main

import (
        "fmt"
        "log"
        "net/http"
        "net/http/httptest"
        "net/http/httputil"
        "net/url"
)

func main() {
        backendServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
                w.WriteHeader(http.StatusOK)
        }))
        defer backendServer.Close()

        rpURL, err := url.Parse(backendServer.URL)
        if err != nil {
                log.Fatal(err)
        }
        frontendProxy := httptest.NewServer(httputil.NewSingleHostReverseProxy(rpURL))
        defer frontendProxy.Close()

        resp, err := http.Get(frontendProxy.URL)
        if err != nil {
                log.Fatal(err)
        }

        fmt.Printf("response header: %#v\n", resp.Header)
}

What did you expect to see?

Content-Type should not be set with empty content.

What did you see instead?

Content-Type is set automatically by Go http server.

response header: http.Header{"Content-Length":[]string{"0"}, "Content-Type":[]string{"text/plain; charset=utf-8"}, "Date":[]string{"Sat, 24 Jun 2017 05:18:32 GMT"}}

I suppose this patch should work:

diff --git a/src/net/http/server.go b/src/net/http/server.go
index add05c2..a48b88b 100644
--- a/src/net/http/server.go
+++ b/src/net/http/server.go
@@ -1304,7 +1304,7 @@ func (cw *chunkWriter) writeHeader(p []byte) {
        if bodyAllowedForStatus(code) {
                // If no content type, apply sniffing algorithm to body.
                _, haveType := header["Content-Type"]
-               if !haveType && !hasTE {
+               if !haveType && !hasTE && len(p) > 0 {
                        setHeader.contentType = DetectContentType(p)
                }
        } else {

Any thoughts ?

The text was updated successfully, but these errors were encountered:

bradfitz · 2017-06-24T05:35:46Z

Sure, seems fine to change. It's harmless as-is and not wrong, but not sending it saves some bandwidth at least.

Feel free to send a change + test: see https://tip.golang.org/doc/contribute.html

gopherbot · 2017-06-24T06:42:17Z

CL https://golang.org/cl/46631 mentions this issue.

tw4452852 · 2017-06-24T06:49:58Z

@bradfitz Yes, it's alright in most cases, but some clients don't expect this header when they encounter a response with a empty blank. I find this when resolving this caddy issue.

gopherbot · 2017-11-28T00:22:32Z

Change https://golang.org/cl/80135 mentions this issue: http2: don't autodetect Content-Type when the response has an empty body

This change was originally made in https://golang.org/cl/46631, however, that change was applited to net/http/h2_bundle.go instead of x/net/http2. Updates golang/go#20784 Change-Id: I947fa4c19f3efc400856573768140bece28276a2 Reviewed-on: https://go-review.googlesource.com/80135 Run-TryBot: Tom Bergan <tombergan@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

gopherbot · 2017-11-28T01:42:09Z

Change https://golang.org/cl/80078 mentions this issue: net/http: update bundled http2

Update http2 to x/net git rev db473f6b23. (And un-skip TestWriteHeader0_h2 added in CL 80077, now fixed.) Includes: http2: remove afterReqBodyWriteError wrapper https://golang.org/cl/75252 http2: fix transport data race on reused *http.Request objects https://golang.org/cl/75530 http2: require either ECDSA or RSA ciphersuite https://golang.org/cl/30721 http2: don't log about timeouts reading client preface on new connections https://golang.org/cl/79498 http2: don't crash in Transport on server's DATA following bogus HEADERS https://golang.org/cl/80056 http2: panic on invalid WriteHeader status code https://golang.org/cl/80076 http2: fix race on ClientConn.maxFrameSize https://golang.org/cl/79238 http2: don't autodetect Content-Type when the response has an empty body https://golang.org/cl/80135 Fixes #18776 Updates #20784 Fixes #21316 Fixes #22721 Fixes #22880 Change-Id: Ie86e24e0ee2582a5a82afe5de3c7c801528be069 Reviewed-on: https://go-review.googlesource.com/80078 Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Tom Bergan <tombergan@google.com>

gopherbot · 2017-12-05T22:32:26Z

Change https://golang.org/cl/82016 mentions this issue: doc: mention net/http Server Content-Type change

gopherbot · 2017-12-05T22:33:18Z

Change https://golang.org/cl/82017 mentions this issue: internal: fix test on Go 1.10

Go 1.10 no longer sets implicit Content-Type on empty output. Updates golang/go#20784 Change-Id: I3f13f76b94b58869481218ea2e1805f5f4175fd7 Reviewed-on: https://go-review.googlesource.com/82017 Reviewed-by: Ian Lance Taylor <iant@golang.org>

Updates #20784 Change-Id: Ic07c78a86da5026e407ac9ecb3117d320c198048 Reviewed-on: https://go-review.googlesource.com/82016 Reviewed-by: Andrew Bonventre <andybons@golang.org>

gopherbot · 2018-02-13T21:02:45Z

Change https://golang.org/cl/93695 mentions this issue: [release-branch.go1.10] doc: mention net/http Server Content-Type change

Updates #20784 Change-Id: Ic07c78a86da5026e407ac9ecb3117d320c198048 Reviewed-on: https://go-review.googlesource.com/93695 Reviewed-by: Andrew Bonventre <andybons@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This change was originally made in https://golang.org/cl/46631, however, that change was applited to net/http/h2_bundle.go instead of x/net/http2. Updates golang/go#20784 Change-Id: I947fa4c19f3efc400856573768140bece28276a2 Reviewed-on: https://go-review.googlesource.com/80135 Run-TryBot: Tom Bergan <tombergan@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Update http2 to x/net git rev db473f6b23. (And un-skip TestWriteHeader0_h2 added in CL 80077, now fixed.) Includes: http2: remove afterReqBodyWriteError wrapper https://golang.org/cl/75252 http2: fix transport data race on reused *http.Request objects https://golang.org/cl/75530 http2: require either ECDSA or RSA ciphersuite https://golang.org/cl/30721 http2: don't log about timeouts reading client preface on new connections https://golang.org/cl/79498 http2: don't crash in Transport on server's DATA following bogus HEADERS https://golang.org/cl/80056 http2: panic on invalid WriteHeader status code https://golang.org/cl/80076 http2: fix race on ClientConn.maxFrameSize https://golang.org/cl/79238 http2: don't autodetect Content-Type when the response has an empty body https://golang.org/cl/80135 Fixes golang/go#18776 Updates golang/go#20784 Fixes golang/go#21316 Fixes golang/go#22721 Fixes golang/go#22880 Change-Id: Ie86e24e0ee2582a5a82afe5de3c7c801528be069 Reviewed-on: https://go-review.googlesource.com/80078 Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Tom Bergan <tombergan@google.com>

bradfitz added this to the Go1.10 milestone Jun 24, 2017

bradfitz added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Jun 24, 2017

databus23 mentioned this issue Sep 15, 2017

Content-Type header set for empty responses. go-openapi/runtime#64

Closed

databus23 mentioned this issue Nov 6, 2017

Remove Content-Type for empty responses go-swagger/go-swagger#1249

Merged

gopherbot closed this as completed in 8cdd999 Nov 15, 2017

golang locked and limited conversation to collaborators Feb 13, 2019

gopherbot added the FrozenDueToAge label Feb 13, 2019

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

net/http: Content-Type is set even with empty body #20784

net/http: Content-Type is set even with empty body #20784

tw4452852 commented Jun 24, 2017

bradfitz commented Jun 24, 2017

gopherbot commented Jun 24, 2017

tw4452852 commented Jun 24, 2017

gopherbot commented Nov 28, 2017

gopherbot commented Nov 28, 2017

gopherbot commented Dec 5, 2017

gopherbot commented Dec 5, 2017

gopherbot commented Feb 13, 2018

net/http: Content-Type is set even with empty body #20784

net/http: Content-Type is set even with empty body #20784

Comments

tw4452852 commented Jun 24, 2017

What version of Go are you using (go version)?

What operating system and processor architecture are you using (go env)?

What did you do?

What did you expect to see?

What did you see instead?

bradfitz commented Jun 24, 2017

gopherbot commented Jun 24, 2017

tw4452852 commented Jun 24, 2017

gopherbot commented Nov 28, 2017

gopherbot commented Nov 28, 2017

gopherbot commented Dec 5, 2017

gopherbot commented Dec 5, 2017

gopherbot commented Feb 13, 2018

What version of Go are you using (`go version`)?

What operating system and processor architecture are you using (`go env`)?