2022-03-03 16:01:31 -07:00
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package headscale
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import (
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"context"
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"fmt"
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"net"
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"net/http"
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2022-03-05 12:04:31 -07:00
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"net/url"
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"strconv"
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2022-03-03 16:01:31 -07:00
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"strings"
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"time"
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"github.com/gin-gonic/gin"
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"github.com/rs/zerolog/log"
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"tailscale.com/derp"
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"tailscale.com/net/stun"
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2022-03-05 12:04:31 -07:00
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"tailscale.com/tailcfg"
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2022-03-03 16:01:31 -07:00
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"tailscale.com/types/key"
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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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2022-03-05 11:30:30 -07:00
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type DERPServer struct {
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tailscaleDERP *derp.Server
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region tailcfg.DERPRegion
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}
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func (h *Headscale) NewDERPServer() (*DERPServer, error) {
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s := derp.NewServer(key.NodePrivate(*h.privateKey), log.Info().Msgf)
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2022-03-05 12:04:31 -07:00
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region, err := h.generateRegionLocalDERP()
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if err != nil {
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return nil, err
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}
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return &DERPServer{s, region}, nil
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}
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func (h *Headscale) generateRegionLocalDERP() (tailcfg.DERPRegion, error) {
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serverURL, err := url.Parse(h.cfg.ServerURL)
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if err != nil {
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return tailcfg.DERPRegion{}, err
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}
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var host string
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var port int
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host, portStr, err := net.SplitHostPort(serverURL.Host)
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if err != nil {
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if serverURL.Scheme == "https" {
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host = serverURL.Host
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port = 443
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} else {
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host = serverURL.Host
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port = 80
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}
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} else {
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port, err = strconv.Atoi(portStr)
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if err != nil {
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return tailcfg.DERPRegion{}, err
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}
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}
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2022-03-05 12:04:31 -07:00
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localDERPregion := tailcfg.DERPRegion{
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RegionID: 999,
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RegionCode: "headscale",
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RegionName: "Headscale Embedded DERP",
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Avoid: false,
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Nodes: []*tailcfg.DERPNode{
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{
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Name: "999a",
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RegionID: 999,
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HostName: host,
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DERPPort: port,
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},
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},
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}
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return localDERPregion, nil
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}
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func (h *Headscale) DERPHandler(ctx *gin.Context) {
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log.Trace().Caller().Msgf("/derp request from %v", ctx.ClientIP())
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up := strings.ToLower(ctx.Request.Header.Get("Upgrade"))
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if up != "websocket" && up != "derp" {
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if up != "" {
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log.Warn().Caller().Msgf("Weird websockets connection upgrade: %q", up)
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}
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ctx.String(http.StatusUpgradeRequired, "DERP requires connection upgrade")
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return
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}
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fastStart := ctx.Request.Header.Get(fastStartHeader) == "1"
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hijacker, ok := ctx.Writer.(http.Hijacker)
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if !ok {
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log.Error().Caller().Msg("DERP requires Hijacker interface from Gin")
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ctx.String(http.StatusInternalServerError, "HTTP does not support general TCP support")
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return
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}
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netConn, conn, err := hijacker.Hijack()
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if err != nil {
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log.Error().Caller().Err(err).Msgf("Hijack failed")
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ctx.String(http.StatusInternalServerError, "HTTP does not support general TCP support")
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return
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}
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if !fastStart {
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pubKey := h.privateKey.Public()
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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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h.DERPServer.tailscaleDERP.Accept(netConn, conn, netConn.RemoteAddr().String())
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}
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// DERPProbeHandler is the endpoint that js/wasm clients hit to measure
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// DERP latency, since they can't do UDP STUN queries.
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func (h *Headscale) DERPProbeHandler(ctx *gin.Context) {
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switch ctx.Request.Method {
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case "HEAD", "GET":
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ctx.Writer.Header().Set("Access-Control-Allow-Origin", "*")
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default:
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ctx.String(http.StatusMethodNotAllowed, "bogus probe method")
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}
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}
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2022-03-05 17:23:35 -07:00
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// DERPBootstrapDNSHandler implements the /bootsrap-dns endpoint
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// Described in https://github.com/tailscale/tailscale/issues/1405,
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// this endpoint provides a way to help a client when it fails to start up
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// because its DNS are broken.
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// The initial implementation is here https://github.com/tailscale/tailscale/pull/1406
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// They have a cache, but not clear if that is really necessary at Headscale, uh, scale.
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func (h *Headscale) DERPBootstrapDNSHandler(ctx *gin.Context) {
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dnsEntries := make(map[string][]net.IP)
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resolvCtx, cancel := context.WithTimeout(context.Background(), time.Minute)
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defer cancel()
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var r net.Resolver
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for _, region := range h.DERPMap.Regions {
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for _, node := range region.Nodes { // we don't care if we override some nodes
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addrs, err := r.LookupIP(resolvCtx, "ip", node.HostName)
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if err != nil {
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log.Trace().Caller().Err(err).Msgf("bootstrap DNS lookup failed %q", node.HostName)
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continue
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}
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dnsEntries[node.HostName] = addrs
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}
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}
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ctx.JSON(http.StatusOK, dnsEntries)
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}
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// ServeSTUN starts a STUN server on udp/3478
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func (h *Headscale) ServeSTUN() {
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pc, err := net.ListenPacket("udp", "0.0.0.0:3478")
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if err != nil {
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log.Fatal().Msgf("failed to open STUN listener: %v", err)
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}
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log.Trace().Msgf("STUN server started at %s", pc.LocalAddr())
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serverSTUNListener(context.Background(), pc.(*net.UDPConn))
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}
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func serverSTUNListener(ctx context.Context, pc *net.UDPConn) {
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var buf [64 << 10]byte
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var (
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n int
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ua *net.UDPAddr
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err error
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)
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for {
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n, ua, err = pc.ReadFromUDP(buf[:])
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if err != nil {
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if ctx.Err() != nil {
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return
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}
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log.Error().Caller().Err(err).Msgf("STUN ReadFrom")
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time.Sleep(time.Second)
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continue
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}
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log.Trace().Caller().Msgf("STUN request from %v", ua)
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pkt := buf[:n]
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if !stun.Is(pkt) {
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continue
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}
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txid, err := stun.ParseBindingRequest(pkt)
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if err != nil {
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continue
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}
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res := stun.Response(txid, ua.IP, uint16(ua.Port))
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pc.WriteTo(res, ua)
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}
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}
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