2021-03-25 22:38:40 +00:00
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// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package ipnlocal
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import (
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"context"
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"errors"
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"fmt"
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"hash/crc32"
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"html"
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"io"
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"net"
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"net/http"
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"strconv"
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"inet.af/netaddr"
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2021-03-26 04:41:37 +00:00
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"tailscale.com/net/interfaces"
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2021-03-25 22:38:40 +00:00
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"tailscale.com/tailcfg"
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)
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2021-03-26 04:41:37 +00:00
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var initListenConfig func(*net.ListenConfig, netaddr.IP, *interfaces.State) error
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2021-03-25 22:38:40 +00:00
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2021-03-26 04:41:37 +00:00
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func peerAPIListen(ip netaddr.IP, ifState *interfaces.State) (ln net.Listener, err error) {
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2021-03-25 22:38:40 +00:00
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var lc net.ListenConfig
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if initListenConfig != nil {
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// On iOS/macOS, this sets the lc.Control hook to
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// setsockopt the interface index to bind to, to get
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// out of the network sandbox.
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2021-03-26 04:41:37 +00:00
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if err := initListenConfig(&lc, ip, ifState); err != nil {
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2021-03-25 22:38:40 +00:00
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return nil, err
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}
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}
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// Make a best effort to pick a deterministic port number for
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// the ip The lower three bytes are the same for IPv4 and IPv6
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// Tailscale addresses (at least currently), so we'll usually
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// get the same port number on both address families for
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// dev/debugging purposes, which is nice. But it's not so
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// deterministic that people will bake this into clients.
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// We try a few times just in case something's already
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// listening on that port (on all interfaces, probably).
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for try := uint8(0); try < 5; try++ {
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a16 := ip.As16()
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hashData := a16[len(a16)-3:]
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hashData[0] += try
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tryPort := (32 << 10) | uint16(crc32.ChecksumIEEE(hashData))
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ln, err = lc.Listen(context.Background(), "tcp", net.JoinHostPort(ip.String(), strconv.Itoa(int(tryPort))))
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if err == nil {
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return ln, nil
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}
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}
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// Fall back to random ephemeral port.
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return lc.Listen(context.Background(), "tcp", net.JoinHostPort(ip.String(), "0"))
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}
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type peerAPIListener struct {
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ln net.Listener
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lb *LocalBackend
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}
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func (pln *peerAPIListener) serve() {
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defer pln.ln.Close()
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logf := pln.lb.logf
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for {
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c, err := pln.ln.Accept()
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if errors.Is(err, net.ErrClosed) {
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return
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}
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if err != nil {
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logf("peerapi.Accept: %v", err)
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return
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}
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ta, ok := c.RemoteAddr().(*net.TCPAddr)
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if !ok {
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c.Close()
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logf("peerapi: unexpected RemoteAddr %#v", c.RemoteAddr())
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continue
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}
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ipp, ok := netaddr.FromStdAddr(ta.IP, ta.Port, "")
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if !ok {
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logf("peerapi: bogus TCPAddr %#v", ta)
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c.Close()
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continue
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}
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peerNode, peerUser, ok := pln.lb.WhoIs(ipp)
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if !ok {
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logf("peerapi: unknown peer %v", ipp)
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c.Close()
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continue
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}
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pas := &peerAPIServer{
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remoteAddr: ipp,
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peerNode: peerNode,
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peerUser: peerUser,
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lb: pln.lb,
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}
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httpServer := &http.Server{
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Handler: pas,
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}
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go httpServer.Serve(&oneConnListener{Listener: pln.ln, conn: c})
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}
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}
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type oneConnListener struct {
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net.Listener
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conn net.Conn
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}
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func (l *oneConnListener) Accept() (c net.Conn, err error) {
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c = l.conn
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if c == nil {
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err = io.EOF
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return
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}
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err = nil
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l.conn = nil
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return
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}
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func (l *oneConnListener) Close() error { return nil }
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type peerAPIServer struct {
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remoteAddr netaddr.IPPort
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peerNode *tailcfg.Node
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peerUser tailcfg.UserProfile
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lb *LocalBackend
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}
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func (s *peerAPIServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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fmt.Fprintf(w, `<html>
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<meta name="viewport" content="width=device-width, initial-scale=1">
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<body>
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<h1>Hello, %s (%v)</h1>
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This is my Tailscale device. Your device is %v.
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`, html.EscapeString(s.peerUser.DisplayName), s.remoteAddr.IP, html.EscapeString(s.peerNode.ComputedName))
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}
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