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wsproxy.go
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wsproxy.go
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package expose
import (
"fmt"
"io"
"net/http"
"net/http/httputil"
"sync/atomic"
"time"
"github.com/gorilla/websocket"
)
// httputil.ReverseProxy in Go1.10 doesn't support websockets, so we intercept
// that particular situation and do so manually. This can all be removed once
// generic-worker is upgraded to Go1.12 or higher.
// What follows is based on websocktunnel's wsmux/wsmux.go
type proxy struct {
targetPort uint16
}
var debug = false
func (p *proxy) logf(format string, v ...interface{}) {
if debug {
fmt.Printf(format+"\n", v...)
}
}
func (p *proxy) websocketProxy(w http.ResponseWriter, r *http.Request) error {
// at this point, we are sure that r is a http websocket upgrade request
p.logf("creating WS bridge: path=%s", r.URL.RequestURI())
dialer := &websocket.Dialer{
Subprotocols: websocket.Subprotocols(r),
}
// create new header
// copy request headers to new header. Avoid websocket headers
// as these will be added by Dial
reqHeader := make(http.Header)
for k, v := range r.Header {
if k == "Upgrade" ||
k == "Connection" ||
k == "Sec-Websocket-Key" ||
k == "Sec-Websocket-Version" ||
k == "Sec-Websocket-Extensions" ||
k == "Sec-Websocket-Protocol" {
continue
}
reqHeader[k] = v
}
uri := fmt.Sprintf("ws://127.0.0.1:%d", p.targetPort)
p.logf("dialing ws at: %s", uri)
tunnelConn, resp, err := dialer.Dial(uri, reqHeader)
if err != nil {
p.logf("could not dial tunnel: path=%s, error: %v", r.URL.RequestURI(), err)
return err
}
defer resp.Body.Close()
upgrader := websocket.Upgrader{
Subprotocols: websocket.Subprotocols(r),
CheckOrigin: func(r *http.Request) bool {
return true
},
}
viewerConn, err := upgrader.Upgrade(w, r, nil)
if err != nil {
p.logf("could not upgrade client connection: path=%s, error: %v", r.URL.RequestURI(), err)
// close tunnel connection
_ = tunnelConn.Close()
return err
}
p.logf("initiating connection bridge")
// bridge both websocket connections
bridgeErr := p.bridgeConn(tunnelConn, viewerConn)
if bridgeErr != nil {
p.logf("bridge closed with err: %v", bridgeErr)
}
if bridgeErr != nil {
return bridgeErr
}
return err
}
func (p *proxy) bridgeConn(conn1 *websocket.Conn, conn2 *websocket.Conn) error {
// set ping and pong handlers
conn1.SetPingHandler(forwardControl(websocket.PingMessage, conn2))
conn2.SetPingHandler(forwardControl(websocket.PingMessage, conn1))
conn1.SetPongHandler(forwardControl(websocket.PongMessage, conn2))
conn2.SetPongHandler(forwardControl(websocket.PongMessage, conn1))
// set close handlers
conn1.SetCloseHandler(func(code int, text string) error {
return nil
})
conn2.SetCloseHandler(func(code int, text string) error {
return nil
})
// ensure connections are closed after bridge exits
defer func() {
_ = conn1.Close()
_ = conn2.Close()
}()
kill := make(chan bool, 1)
var eSrc, eDest atomic.Value
// Wait until errors are written
go func() {
err := copyWsData(conn1, conn2, kill)
if err != nil {
eSrc.Store(err)
}
}()
go func() {
err := copyWsData(conn2, conn1, kill)
if err != nil {
eDest.Store(err)
}
}()
<-kill
if err, ok := eSrc.Load().(error); ok && err != nil {
return err
}
if err, ok := eDest.Load().(error); ok && err != nil {
return err
}
return nil
}
func copyWsData(dest *websocket.Conn, src *websocket.Conn, kill chan bool) error {
defer asyncClose(kill)
for {
mtype, reader, err := src.NextReader()
if err != nil {
// Abnormal closure occurs if the websocket is over a wsmux stream
if websocket.IsUnexpectedCloseError(err, websocket.CloseNormalClosure,
websocket.CloseGoingAway, websocket.CloseAbnormalClosure) {
return err
}
return nil
}
writer, err := dest.NextWriter(mtype)
if err != nil {
// Abnormal closure occurs if the websocket is over a wsmux stream
if websocket.IsUnexpectedCloseError(err, websocket.CloseNormalClosure,
websocket.CloseGoingAway, websocket.CloseAbnormalClosure) {
return err
}
return nil
}
_, err = io.Copy(writer, reader)
_ = writer.Close()
if err != nil {
return err
}
select {
case <-kill:
return nil
default:
}
}
}
func forwardControl(messageType int, dest *websocket.Conn) func(string) error {
return func(appData string) error {
return dest.WriteControl(messageType, []byte(appData), time.Now().Add(20*time.Second))
}
}
func asyncClose(kill chan bool) {
select {
case <-kill:
default:
close(kill)
}
}
// the main entry point: generate an http.HandlerFunc that will mostly just use
// the given ReverseProxy, but will handle websockets, too.
func websockCompatibleHandlerFunc(reverseproxy *httputil.ReverseProxy, targetPort uint16) http.HandlerFunc {
return func(w http.ResponseWriter, r *http.Request) {
if websocket.IsWebSocketUpgrade(r) {
p := proxy{targetPort: targetPort}
_ = p.websocketProxy(w, r)
}
// not a websocket thing; defer to ReverseProxy
reverseproxy.ServeHTTP(w, r)
}
}