82 lines
2.2 KiB
Go
82 lines
2.2 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package derphttp
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import (
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"fmt"
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"log"
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"net/http"
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"strings"
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"tailscale.com/derp"
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)
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// fastStartHeader is the header (with value "1") that signals to the HTTP
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// server that the DERP HTTP client does not want the HTTP 101 response
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// headers and it will begin writing & reading the DERP protocol immediately
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// following its HTTP request.
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const fastStartHeader = "Derp-Fast-Start"
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func Handler(s *derp.Server) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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// These are installed both here and in cmd/derper. The check here
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// catches both cmd/derper run with DERP disabled (STUN only mode) as
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// well as DERP being run in tests with derphttp.Handler directly,
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// as netcheck still assumes this replies.
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switch r.URL.Path {
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case "/derp/probe", "/derp/latency-check":
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ProbeHandler(w, r)
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return
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}
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up := strings.ToLower(r.Header.Get("Upgrade"))
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if up != "websocket" && up != "derp" {
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if up != "" {
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log.Printf("Weird upgrade: %q", up)
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}
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http.Error(w, "DERP requires connection upgrade", http.StatusUpgradeRequired)
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return
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}
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fastStart := r.Header.Get(fastStartHeader) == "1"
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h, ok := w.(http.Hijacker)
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if !ok {
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http.Error(w, "HTTP does not support general TCP support", 500)
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return
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}
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netConn, conn, err := h.Hijack()
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if err != nil {
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log.Printf("Hijack failed: %v", err)
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http.Error(w, "HTTP does not support general TCP support", 500)
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return
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}
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if !fastStart {
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pubKey := s.PublicKey()
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fmt.Fprintf(conn, "HTTP/1.1 101 Switching Protocols\r\n"+
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"Upgrade: DERP\r\n"+
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"Connection: Upgrade\r\n"+
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"Derp-Version: %v\r\n"+
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"Derp-Public-Key: %s\r\n\r\n",
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derp.ProtocolVersion,
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pubKey.UntypedHexString())
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}
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s.Accept(r.Context(), netConn, conn, netConn.RemoteAddr().String())
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})
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}
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// ProbeHandler is the endpoint that clients without UDP access (including js/wasm) hit to measure
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// DERP latency, as a replacement for UDP STUN queries.
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func ProbeHandler(w http.ResponseWriter, r *http.Request) {
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switch r.Method {
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case "HEAD", "GET":
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w.Header().Set("Access-Control-Allow-Origin", "*")
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default:
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http.Error(w, "bogus probe method", http.StatusMethodNotAllowed)
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}
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}
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