x/net/websocket: fails to Receive a single frame sent in chunks from Browser

[mattbaird]

Please answer these questions before submitting your issue. Thanks!

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

1.5 to 1.7

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

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/matthew/code/go:/home/matthew/code/go"
GORACE=""
GOROOT="/usr/local/go"
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build629490277=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"

What did you do?

This is a very difficult issue to reproduce, as the browsers themselves don't always exhibit the problem.
Reproducing in our environment means sending a large >120k websocket message from the Browser (tested on Chrome) to the Go program from a "clean" browser - meaning either all caches, cookies cleared, or a new Incognito mode browser.
When sent to the server, the browser will chunk the frame into multiple parts, setting the hybiFrameReader.header.Fin bit to false

What did you expect to see?

I expected the whole frame to arrive.

What did you see instead?

arbitrary cut off of string frame.

My fix was to change the Receive function to check if the frame Fin was false, and if so, goto Again:

// Receive receives single frame from ws, unmarshaled by cd.Unmarshal and stores in v.
func (cd Codec) Receive(ws *Conn, v interface{}) (err error) {
    ws.rio.Lock()
    defer ws.rio.Unlock()
    if ws.frameReader != nil {
        _, err = io.Copy(ioutil.Discard, ws.frameReader)
        if err != nil {
            return err
        }
        ws.frameReader = nil
    }
    var b bytes.Buffer
again:
    frame, err := ws.frameReaderFactory.NewFrameReader()
    if err != nil {
        return err
    }
    frame, err = ws.frameHandler.HandleFrame(frame)
    if err != nil {
        return err
    }
    if frame == nil {
        goto again
    }
    payloadType := frame.PayloadType()
    data, err := ioutil.ReadAll(frame)
    if err != nil {
        return err
    }
    _, err = b.Write(data)
    if err != nil {
        return err
    }
    if !frame.(*hybiFrameReader).header.Fin {
        goto again
    }
    return cd.Unmarshal(b.Bytes(), payloadType, v)
}

I have a feeling Read(...) also suffers from this problem.

[mattbaird]

hi @quentinmit is x/net/ being migrated to just net? I thought I saw something about that, but cannot find it now.

[bradfitz]

@mattbaird, no. Parts of x/net are privately vendored into the standard library when needed, but nothing's moving.

[mattbaird]

@bradfitz thank you, I was a little bit worried there was another bigger refactoring happening.

[mattbaird]

hi @quentinmit how can I help move this issue along?

[mattbaird]

is this version of websockets being abandoned? I see references to Gorilla websockets package in the code comments - are users encouraged to migrate away from this package to the Gorilla version?

[bradfitz]

It's not explicitly abandoned, but nobody works on it either, and its design is basically wrong. It's kept for people who still depend on it but, yes, you should probably use Gorilla.