net/http: Several 100-continue

[2at2]

Hi!
I send request to some server and i have a trouble with several 100-continue responses.

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

go version go1.9 darwin/amd64

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

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/..."
GORACE=""
GOROOT="/Users/.../go1.9"
GOTOOLDIR="/Users/.../go1.9/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/kz/4rf1vvhj2kb910mwtq44qzvr0000gn/T/go-build703834570=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
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?

libcurl example:

curl -i https://*** -H 'Authorization: Basic ***' -H 'Expect: 100-continue' --data 'some content' -v
***
> POST /secure/gateway HTTP/1.1
> Host: ***
> User-Agent: curl/7.54.0
> Accept: */*
> Authorization: Basic ***
> Expect: 100-continue
> Content-Length: 12
> Content-Type: application/x-www-form-urlencoded
>
< HTTP/1.1 100 Continue
HTTP/1.1 100 Continue

* We are completely uploaded and fine
< HTTP/1.1 100 Continue
HTTP/1.1 100 Continue

< HTTP/1.1 200 OK
HTTP/1.1 200 OK
< Date: Wed, 04 Oct 2017 10:48:22 GMT
Date: Wed, 04 Oct 2017 10:48:22 GMT
< Content-Type: text/xml
Content-Type: text/xml
< Connection: close
Connection: close
< Transfer-Encoding: chunked
Transfer-Encoding: chunked

In example you see two HTTP/1.1 100 Continue

GO 1.9 example:

func main() {
	content := bytes.NewReader([]byte("my super body"))

	request, err := http.NewRequest("POST", "***", content)

	if err != nil {
		panic(err)
	}

	request.Header = make(http.Header)
	request.Header.Set("Authorization", "Basic ***")
	request.Header.Set("Expect", "100-continue")
	
        client := &http.Client{}
	resp, err := client.Do(request)

	if err != nil {
		panic(err)
	}
	defer resp.Body.Close()

	_, err = ioutil.ReadAll(resp.Body)

	if err != nil {
		panic(err)
	}

	fmt.Println(resp.StatusCode)
	fmt.Println(resp.Status)
}

Result of this example:

100
100 Continue

What did you expect to see?

200
200 Ok

What did you see instead?

100
100 Continue

I found problem in src/net/http/transport.go:1698

What do you think about:

diff --git a/src/net/http/transport.go b/src/net/http/transport.go
index 6a89392a99..9f85f07700 100644
--- a/src/net/http/transport.go
+++ b/src/net/http/transport.go
@@ -1715,13 +1715,17 @@ func (pc *persistConn) readResponse(rc requestAndChan, trace *httptrace.ClientTr
 			close(rc.continueCh)
 		}
 	}
-	if resp.StatusCode == 100 {
-		pc.readLimit = pc.maxHeaderResponseSize() // reset the limit
-		resp, err = ReadResponse(pc.br, rc.req)
-		if err != nil {
-			return
+
+	for {
+		if resp.StatusCode == 100 {
+			pc.readLimit = pc.maxHeaderResponseSize() // reset the limit
+			resp, err = ReadResponse(pc.br, rc.req)
+			if err != nil {
+				return
+			}
 		}
 	}
+
 	resp.TLS = pc.tlsState
 	return
 }

I know endless cycle it's not good idea =)

UPD: The similar problem https://stackoverflow.com/questions/22818059/several-100-continue-received-from-the-server . Request to an IIS 7.5 server.

[ianlancetaylor]

CC @tombergan

[tombergan]

Thanks for the report. As best I can tell, the server and the Go client library are both wrong. The server should not send multiple 100-continues and Go should ignore the extra 100-continues.

https://tools.ietf.org/html/rfc7231#section-6.2

A client MUST be able to parse one or more 1xx responses received
prior to a final response, even if the client does not expect one. A
user agent MAY ignore unexpected 1xx responses.

The second 100-continue response is an unexpected 1xx response that we should ignore. This is definitely a bug we should fix, however, I'm going to close this issue because it's a dup of #17739, which is the exact same problem (Go does not ignore unexpected 1xx responses).

[fraenkel]

I took your code and created a complete example
https://play.golang.org/p/wRfdbQhViw

I get your expected output.

[tombergan]

@fraenkel That doesn't repro the problem. The server is Go, which should send a single 100-continue. To repro, the server would need to send multiple 100-continue messages. Here's a repro:

https://play.golang.org/p/Czf4GKg2qt [edit: I had a typo in the prior link]

[fraenkel]

Right. I was saying I couldn't do it with go if I wasn't clear.

…

On Oct 4, 2017 6:31 PM, "tombergan" ***@***.***> wrote: @fraenkel <https://github.com/fraenkel> That doesn't repro the problem. The server is Go, which should send a single 100-continue. To repro, the server would need to send multiple 100-continue messages. Here's a repro: https://play.golang.org/p/jWKbT4MhQB — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#22128 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AA4uYaldmFMhQ3IBIgoAjrUdBfkJ7qIkks5spAdBgaJpZM4PtcxF> .