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proxy_ws.go
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/
proxy_ws.go
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// Copyright 2021 Northern.tech AS
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package proxy
// Inspired by https://github.com/koding/websocketproxy
import (
"fmt"
"net/http"
"net/url"
"strings"
"sync"
"github.com/gorilla/websocket"
log "github.com/sirupsen/logrus"
)
const (
maxWsConnections = 1
)
func newUpgrader() *websocket.Upgrader {
return &websocket.Upgrader{
CheckOrigin: func(r *http.Request) bool {
return true
},
}
}
func wsSchemeFromHttpScheme(httpScheme string) string {
switch httpScheme {
case "http":
return "ws"
case "https":
return "wss"
default:
return ""
}
}
func (pc *ProxyController) wsRunning() bool {
pc.wsConnectionsMutex.Lock()
defer pc.wsConnectionsMutex.Unlock()
return len(pc.wsConnections) > 0
}
func (pc *proxyControllerInner) wsAvailable() bool {
pc.wsConnectionsMutex.Lock()
defer pc.wsConnectionsMutex.Unlock()
return len(pc.wsConnections) < maxWsConnections
}
func (pc *proxyControllerInner) DoWsUpgrade(w http.ResponseWriter, r *http.Request) {
// Convert server request to client request and override r.URL
r.RequestURI = ""
r.Host = ""
r.URL.Scheme = wsSchemeFromHttpScheme(pc.conf.backend.Scheme)
r.URL.Host = pc.conf.backend.Host
// Copy all headers but delete the websocket's handshake related ones
requestHeader := http.Header{}
copyHeader(requestHeader, r.Header)
requestHeader.Del("Sec-Websocket-Key")
requestHeader.Del("Sec-Websocket-Version")
requestHeader.Del("Upgrade")
requestHeader.Del("Connection")
wsUrl := url.URL{
Host: pc.conf.backend.Host,
Scheme: wsSchemeFromHttpScheme(pc.conf.backend.Scheme),
Path: ApiUrlDevicesConnect,
}
connBackend, resp, err := pc.wsDialer.Dial(wsUrl.String(), requestHeader)
if err != nil {
log.Errorf("couldn't dial to remote backend url %q, err: %s", wsUrl.String(), err.Error())
if resp != nil {
// WebSocket handshake failed, reply the client with backend's resp
if err := copyResponse(w, resp); err != nil {
log.Errorf("couldn't write response after failed remote backend handshake: %s", err)
}
} else {
http.Error(
w,
http.StatusText(http.StatusServiceUnavailable),
http.StatusServiceUnavailable,
)
}
return
}
defer connBackend.Close()
// Only pass certain headers to the upgrader.
upgradeHeader := http.Header{}
if hdr := resp.Header.Get("Sec-Websocket-Protocol"); hdr != "" {
upgradeHeader.Set("Sec-Websocket-Protocol", hdr)
}
if hdr := resp.Header.Get("Set-Cookie"); hdr != "" {
upgradeHeader.Set("Set-Cookie", hdr)
}
// If backend replied with a protocol, use that one for our upgrader
// It shall only be one after the handshake, but Upgrader.Subprotocols
// expects an slice, so copy "all".
upgrader := newUpgrader()
if hdr := resp.Header.Get("Sec-Websocket-Protocol"); hdr != "" {
backendProtocols := strings.Split(hdr, ",")
for i := range backendProtocols {
backendProtocols[i] = strings.TrimSpace(backendProtocols[i])
}
upgrader.Subprotocols = backendProtocols
}
// Now ready to upgrade connection from client to proxy!
connClient, err := upgrader.Upgrade(w, r, upgradeHeader)
if err != nil {
log.Errorf("couldn't upgrade %s", err)
return
}
defer connClient.Close()
newConn := &wsConnection{
connBackend: connBackend,
connClient: connClient,
}
pc.wsConnectionsMutex.Lock()
pc.wsConnections[newConn] = true
pc.wsConnectionsMutex.Unlock()
errClient := make(chan error, 1)
errBackend := make(chan error, 1)
go pc.forwardWsConnection(
newConn.connClient,
newConn.connBackend,
errClient,
&newConn.connClientWriteMutex,
)
go pc.forwardWsConnection(
newConn.connBackend,
newConn.connClient,
errBackend,
&newConn.connBackendWriteMutex,
)
var messageF string
select {
case err = <-errClient:
messageF = "error forwarding from backend to client: %v"
case err = <-errBackend:
messageF = "error forwarding from client to backend: %v"
}
if e, ok := err.(*websocket.CloseError); !ok || e.Code != websocket.CloseNormalClosure {
log.Errorf(messageF, err.Error())
}
pc.wsConnectionsMutex.Lock()
delete(pc.wsConnections, newConn)
pc.wsConnectionsMutex.Unlock()
}
func (pc *proxyControllerInner) forwardWsConnection(
dst, src *websocket.Conn,
errChann chan error,
mutex *sync.Mutex,
) {
for {
msgType, msg, err := src.ReadMessage()
if err != nil {
m := websocket.FormatCloseMessage(websocket.CloseNormalClosure, fmt.Sprintf("%v", err))
if e, ok := err.(*websocket.CloseError); ok {
if e.Code != websocket.CloseNoStatusReceived {
m = websocket.FormatCloseMessage(e.Code, e.Text)
}
}
mutex.Lock()
errWrite := dst.WriteMessage(websocket.CloseMessage, m)
mutex.Unlock()
if errWrite != nil {
log.Warningf("error while sending close message: %v", errWrite.Error())
}
errChann <- err
break
}
mutex.Lock()
err = dst.WriteMessage(msgType, msg)
mutex.Unlock()
if err != nil {
errChann <- err
break
}
}
}
func (pc *ProxyController) CloseWsConnections() {
log.Info("shutting down websocket connections")
m := websocket.FormatCloseMessage(websocket.CloseNormalClosure, "shutting down proxy")
pc.wsConnectionsMutex.Lock()
defer pc.wsConnectionsMutex.Unlock()
for c := range pc.wsConnections {
c.connBackendWriteMutex.Lock()
errWrite := c.connBackend.WriteMessage(websocket.CloseMessage, m)
if errWrite != nil {
log.Errorf("error while sending close message to backend: %v", errWrite.Error())
}
c.connBackendWriteMutex.Unlock()
c.connClientWriteMutex.Lock()
errWrite = c.connClient.WriteMessage(websocket.CloseMessage, m)
if errWrite != nil {
log.Errorf("error while sending close message to backend: %v", errWrite.Error())
}
c.connClientWriteMutex.Unlock()
delete(pc.wsConnections, c)
}
}