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tailscale/ipn/ipnserver/server.go

315 lines
7.7 KiB
Go

// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ipnserver
import (
"bufio"
"context"
"fmt"
"log"
"net"
"net/http"
"os"
"os/exec"
"os/signal"
"sync"
"syscall"
"time"
"github.com/klauspost/compress/zstd"
"tailscale.com/control/controlclient"
"tailscale.com/ipn"
"tailscale.com/logtail/backoff"
"tailscale.com/safesocket"
"tailscale.com/types/logger"
"tailscale.com/version"
"tailscale.com/wgengine"
)
// Options is the configuration of the Tailscale node agent.
type Options struct {
// SocketPath, on unix systems, is the unix socket path to listen
// on for frontend connections.
SocketPath string
// Port, on windows, is the localhost TCP port to listen on for
// frontend connections.
Port int
// StatePath is the path to the stored agent state.
StatePath string
// AutostartStateKey, if non-empty, immediately starts the agent
// using the given StateKey. If empty, the agent stays idle and
// waits for a frontend to start it.
AutostartStateKey ipn.StateKey
// LegacyConfigPath optionally specifies the old-style relaynode
// relay.conf location. If both LegacyConfigPath and
// AutostartStateKey are specified and the requested state doesn't
// exist in the backend store, the backend migrates the config
// from LegacyConfigPath.
//
// TODO(danderson): remove some time after the transition to
// tailscaled is done.
LegacyConfigPath string
// SurviveDisconnects specifies how the server reacts to its
// frontend disconnecting. If true, the server keeps running on
// its existing state, and accepts new frontend connections. If
// false, the server dumps its state and becomes idle.
SurviveDisconnects bool
// DebugMux, if non-nil, specifies an HTTP ServeMux in which
// to register a debug handler.
DebugMux *http.ServeMux
}
func pump(logf logger.Logf, ctx context.Context, bs *ipn.BackendServer, s net.Conn) {
defer logf("Control connection done.")
for ctx.Err() == nil && !bs.GotQuit {
msg, err := ipn.ReadMsg(s)
if err != nil {
logf("ReadMsg: %v", err)
break
}
err = bs.GotCommandMsg(msg)
if err != nil {
logf("GotCommandMsg: %v", err)
break
}
}
}
func Run(rctx context.Context, logf logger.Logf, logid string, opts Options, e wgengine.Engine) (err error) {
runDone := make(chan error, 1)
defer func() { runDone <- err }()
listen, _, err := safesocket.Listen(opts.SocketPath, uint16(opts.Port))
if err != nil {
return fmt.Errorf("safesocket.Listen: %v", err)
}
// Go listeners can't take a context, close it instead.
go func() {
select {
case <-rctx.Done():
case <-runDone:
}
listen.Close()
}()
logf("Listening on %v", listen.Addr())
var store ipn.StateStore
if opts.StatePath != "" {
store, err = ipn.NewFileStore(opts.StatePath)
if err != nil {
return fmt.Errorf("ipn.NewFileStore(%q): %v", opts.StatePath, err)
}
} else {
store = &ipn.MemoryStore{}
}
b, err := ipn.NewLocalBackend(logf, logid, store, e)
if err != nil {
return fmt.Errorf("NewLocalBackend: %v", err)
}
b.SetDecompressor(func() (controlclient.Decompressor, error) {
return zstd.NewReader(nil)
})
if opts.DebugMux != nil {
opts.DebugMux.HandleFunc("/debug/ipn", func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "text/html; charset=utf-8")
st := b.Status()
// TODO(bradfitz): add LogID and opts to st?
st.WriteHTML(w)
})
}
var s net.Conn
serverToClient := func(b []byte) {
if s != nil { // TODO: racy access to s?
ipn.WriteMsg(s, b)
}
}
bs := ipn.NewBackendServer(logf, b, serverToClient)
if opts.AutostartStateKey != "" {
bs.GotCommand(&ipn.Command{
Version: version.LONG,
Start: &ipn.StartArgs{
Opts: ipn.Options{
StateKey: opts.AutostartStateKey,
LegacyConfigPath: opts.LegacyConfigPath,
},
},
})
}
var (
oldS net.Conn
ctx context.Context
cancel context.CancelFunc
)
stopAll := func() {
// Currently we only support one client connection at a time.
// Theoretically we could allow multiple clients, by passing
// notifications to all of them and accepting commands from
// any of them, but there doesn't seem to be much need for
// that right now.
if oldS != nil {
cancel()
safesocket.ConnCloseRead(oldS)
safesocket.ConnCloseWrite(oldS)
}
}
bo := backoff.NewBackoff("ipnserver", logf)
for i := 1; rctx.Err() == nil; i++ {
s, err = listen.Accept()
if err != nil {
logf("%d: Accept: %v", i, err)
bo.BackOff(rctx, err)
continue
}
logf("%d: Incoming control connection.", i)
stopAll()
ctx, cancel = context.WithCancel(rctx)
oldS = s
go func(ctx context.Context, s net.Conn, i int) {
logf := logger.WithPrefix(logf, fmt.Sprintf("%d: ", i))
pump(logf, ctx, bs, s)
if !opts.SurviveDisconnects || bs.GotQuit {
bs.Reset()
s.Close()
}
// Quitting not allowed, just keep going.
bs.GotQuit = false
}(ctx, s, i)
bo.BackOff(ctx, nil)
}
stopAll()
return rctx.Err()
}
func BabysitProc(ctx context.Context, args []string, logf logger.Logf) {
executable, err := os.Executable()
if err != nil {
panic("cannot determine executable: " + err.Error())
}
var proc struct {
mu sync.Mutex
p *os.Process
}
done := make(chan struct{})
go func() {
interrupt := make(chan os.Signal, 1)
signal.Notify(interrupt, syscall.SIGINT, syscall.SIGTERM)
var sig os.Signal
select {
case sig = <-interrupt:
logf("BabysitProc: got signal: %v", sig)
close(done)
case <-ctx.Done():
logf("BabysitProc: context done")
sig = os.Kill
close(done)
}
proc.mu.Lock()
proc.p.Signal(sig)
proc.mu.Unlock()
}()
bo := backoff.NewBackoff("BabysitProc", logf)
for {
startTime := time.Now()
log.Printf("exec: %#v %v", executable, args)
cmd := exec.Command(executable, args...)
// Create a pipe object to use as the subproc's stdin.
// When the writer goes away, the reader gets EOF.
// A subproc can watch its stdin and exit when it gets EOF;
// this is a very reliable way to have a subproc die when
// its parent (us) disappears.
// We never need to actually write to wStdin.
rStdin, wStdin, err := os.Pipe()
if err != nil {
log.Printf("os.Pipe 1: %v", err)
return
}
// Create a pipe object to use as the subproc's stdout/stderr.
// We'll read from this pipe and send it to logf, line by line.
// We can't use os.exec's io.Writer for this because it
// doesn't care about lines, and thus ends up merging multiple
// log lines into one or splitting one line into multiple
// logf() calls. bufio is more appropriate.
rStdout, wStdout, err := os.Pipe()
if err != nil {
log.Printf("os.Pipe 2: %v", err)
}
go func(r *os.File) {
defer r.Close()
rb := bufio.NewReader(r)
for {
s, err := rb.ReadString('\n')
if s != "" {
logf("%s", s)
}
if err != nil {
break
}
}
}(rStdout)
cmd.Stdin = rStdin
cmd.Stdout = wStdout
cmd.Stderr = wStdout
err = cmd.Start()
// Now that the subproc is started, get rid of our copy of the
// pipe reader. Bad things happen on Windows if more than one
// process owns the read side of a pipe.
rStdin.Close()
wStdout.Close()
if err != nil {
log.Printf("starting subprocess failed: %v", err)
} else {
proc.mu.Lock()
proc.p = cmd.Process
proc.mu.Unlock()
err = cmd.Wait()
log.Printf("subprocess exited: %v", err)
}
// If the process finishes, clean up the write side of the
// pipe. We'll make a new one when we restart the subproc.
wStdin.Close()
if time.Since(startTime) < 60*time.Second {
bo.BackOff(ctx, fmt.Errorf("subproc early exit: %v", err))
} else {
// Reset the timeout, since the process ran for a while.
bo.BackOff(ctx, nil)
}
select {
case <-done:
return
default:
}
}
}