feat: automatically use websockets if DERP upgrade is unavailable #6381
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,72 @@ | ||
| package tailnet | ||
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| import ( | ||
| "bufio" | ||
| "context" | ||
| "log" | ||
| "net/http" | ||
| "strings" | ||
| "sync" | ||
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| "nhooyr.io/websocket" | ||
| "tailscale.com/derp" | ||
| "tailscale.com/net/wsconn" | ||
| ) | ||
|
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| // WithWebsocketSupport returns an http.Handler that upgrades | ||
| // connections to the "derp" subprotocol to WebSockets and | ||
| // passes them to the DERP server. | ||
| // Taken from: https://github.com/tailscale/tailscale/blob/e3211ff88ba85435f70984cf67d9b353f3d650d8/cmd/derper/websocket.go#L21 | ||
| func WithWebsocketSupport(s *derp.Server, base http.Handler) (http.Handler, func()) { | ||
| var mu sync.Mutex | ||
| var waitGroup sync.WaitGroup | ||
| ctx, cancelFunc := context.WithCancel(context.Background()) | ||
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| return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { | ||
| up := strings.ToLower(r.Header.Get("Upgrade")) | ||
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| // Very early versions of Tailscale set "Upgrade: WebSocket" but didn't actually | ||
| // speak WebSockets (they still assumed DERP's binary framing). So to distinguish | ||
| // clients that actually want WebSockets, look for an explicit "derp" subprotocol. | ||
| if up != "websocket" || !strings.Contains(r.Header.Get("Sec-Websocket-Protocol"), "derp") { | ||
| base.ServeHTTP(w, r) | ||
|
There was a problem hiding this comment. Should we log here to better understand why it may not be working? (E.g. future bugs.) There was a problem hiding this comment. I don't think so because this could be spammy. |
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| return | ||
| } | ||
|
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| mu.Lock() | ||
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|
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| if ctx.Err() != nil { | ||
| mu.Unlock() | ||
| return | ||
| } | ||
| waitGroup.Add(1) | ||
| mu.Unlock() | ||
| defer waitGroup.Done() | ||
| c, err := websocket.Accept(w, r, &websocket.AcceptOptions{ | ||
| Subprotocols: []string{"derp"}, | ||
| OriginPatterns: []string{"*"}, | ||
| // Disable compression because we transmit WireGuard messages that | ||
| // are not compressible. | ||
| // Additionally, Safari has a broken implementation of compression | ||
| // (see https://github.com/nhooyr/websocket/issues/218) that makes | ||
| // enabling it actively harmful. | ||
| CompressionMode: websocket.CompressionDisabled, | ||
| }) | ||
| if err != nil { | ||
| log.Printf("websocket.Accept: %v", err) | ||
| return | ||
| } | ||
| defer c.Close(websocket.StatusInternalError, "closing") | ||
| if c.Subprotocol() != "derp" { | ||
| c.Close(websocket.StatusPolicyViolation, "client must speak the derp subprotocol") | ||
| return | ||
| } | ||
| wc := wsconn.NetConn(ctx, c, websocket.MessageBinary) | ||
| brw := bufio.NewReadWriter(bufio.NewReader(wc), bufio.NewWriter(wc)) | ||
| s.Accept(ctx, wc, brw, r.RemoteAddr) | ||
| }), func() { | ||
| cancelFunc() | ||
| mu.Lock() | ||
| waitGroup.Wait() | ||
| mu.Unlock() | ||
| } | ||
| } | ||
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