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net/tstun: move TUN failure diagnostics to OS-specific files

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Mostly so the Linux one can use Linux-specific stuff in package
syscall and not use os/exec for uname for portability.

But also it helps deps a tiny bit on iOS.

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
main
Brad Fitzpatrick 5 years ago
parent b2eea1ee00
commit e804ab29fd
3 changed files with 116 additions and 82 deletions
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  1. 89
      net/tstun/tun.go
  2. 82
      net/tstun/tun_linux.go
  3. 27
      net/tstun/tun_macos.go

89
net/tstun/tun.go
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@ -7,10 +7,8 @@
package tstun
import (
"bytes"
"errors"
"os"
"os/exec"
"runtime"
"strconv"
"strings"
@ -18,7 +16,6 @@ import (
"golang.zx2c4.com/wireguard/tun"
"tailscale.com/types/logger"
"tailscale.com/version/distro"
)
// tunMTU is the MTU we set on tailscale's TUN interface. wireguard-go
@ -78,90 +75,18 @@ func New(logf logger.Logf, tunName string) (tun.Device, string, error) {
return dev, name, nil
}
// tunDiagnoseFailure, if non-nil, does OS-specific diagnostics of why
// TUN failed to work.
var tunDiagnoseFailure func(tunName string, logf logger.Logf)
// Diagnose tries to explain a tuntap device creation failure.
// It pokes around the system and logs some diagnostic info that might
// help debug why tun creation failed. Because device creation has
// already failed and the program's about to end, log a lot.
func Diagnose(logf logger.Logf, tunName string) {
switch runtime.GOOS {
case "linux":
diagnoseLinuxTUNFailure(tunName, logf)
case "darwin":
diagnoseDarwinTUNFailure(tunName, logf)
default:
if tunDiagnoseFailure != nil {
tunDiagnoseFailure(tunName, logf)
} else {
logf("no TUN failure diagnostics for OS %q", runtime.GOOS)
}
}
func diagnoseDarwinTUNFailure(tunName string, logf logger.Logf) {
if os.Getuid() != 0 {
logf("failed to create TUN device as non-root user; use 'sudo tailscaled', or run under launchd with 'sudo tailscaled install-system-daemon'")
}
if tunName != "utun" {
logf("failed to create TUN device %q; try using tun device \"utun\" instead for automatic selection", tunName)
}
}
func diagnoseLinuxTUNFailure(tunName string, logf logger.Logf) {
kernel, err := exec.Command("uname", "-r").Output()
kernel = bytes.TrimSpace(kernel)
if err != nil {
logf("no TUN, and failed to look up kernel version: %v", err)
return
}
logf("Linux kernel version: %s", kernel)
modprobeOut, err := exec.Command("/sbin/modprobe", "tun").CombinedOutput()
if err == nil {
logf("'modprobe tun' successful")
// Either tun is currently loaded, or it's statically
// compiled into the kernel (which modprobe checks
// with /lib/modules/$(uname -r)/modules.builtin)
//
// So if there's a problem at this point, it's
// probably because /dev/net/tun doesn't exist.
const dev = "/dev/net/tun"
if fi, err := os.Stat(dev); err != nil {
logf("tun module loaded in kernel, but %s does not exist", dev)
} else {
logf("%s: %v", dev, fi.Mode())
}
// We failed to find why it failed. Just let our
// caller report the error it got from wireguard-go.
return
}
logf("is CONFIG_TUN enabled in your kernel? `modprobe tun` failed with: %s", modprobeOut)
switch distro.Get() {
case distro.Debian:
dpkgOut, err := exec.Command("dpkg", "-S", "kernel/drivers/net/tun.ko").CombinedOutput()
if len(bytes.TrimSpace(dpkgOut)) == 0 || err != nil {
logf("tun module not loaded nor found on disk")
return
}
if !bytes.Contains(dpkgOut, kernel) {
logf("kernel/drivers/net/tun.ko found on disk, but not for current kernel; are you in middle of a system update and haven't rebooted? found: %s", dpkgOut)
}
case distro.Arch:
findOut, err := exec.Command("find", "/lib/modules/", "-path", "*/net/tun.ko*").CombinedOutput()
if len(bytes.TrimSpace(findOut)) == 0 || err != nil {
logf("tun module not loaded nor found on disk")
return
}
if !bytes.Contains(findOut, kernel) {
logf("kernel/drivers/net/tun.ko found on disk, but not for current kernel; are you in middle of a system update and haven't rebooted? found: %s", findOut)
}
case distro.OpenWrt:
out, err := exec.Command("opkg", "list-installed").CombinedOutput()
if err != nil {
logf("error querying OpenWrt installed packages: %s", out)
return
}
for _, pkg := range []string{"kmod-tun", "ca-bundle"} {
if !bytes.Contains(out, []byte(pkg+" - ")) {
logf("Missing required package %s; run: opkg install %s", pkg, pkg)
}
}
}
}

82
net/tstun/tun_linux.go
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@ -0,0 +1,82 @@
// Copyright (c) 2021 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 tstun
import (
"bytes"
"os"
"os/exec"
"tailscale.com/types/logger"
"tailscale.com/version/distro"
)
func init() {
tunDiagnoseFailure = diagnoseLinuxTUNFailure
}
func diagnoseLinuxTUNFailure(tunName string, logf logger.Logf) {
kernel, err := exec.Command("uname", "-r").Output()
kernel = bytes.TrimSpace(kernel)
if err != nil {
logf("no TUN, and failed to look up kernel version: %v", err)
return
}
logf("Linux kernel version: %s", kernel)
modprobeOut, err := exec.Command("/sbin/modprobe", "tun").CombinedOutput()
if err == nil {
logf("'modprobe tun' successful")
// Either tun is currently loaded, or it's statically
// compiled into the kernel (which modprobe checks
// with /lib/modules/$(uname -r)/modules.builtin)
//
// So if there's a problem at this point, it's
// probably because /dev/net/tun doesn't exist.
const dev = "/dev/net/tun"
if fi, err := os.Stat(dev); err != nil {
logf("tun module loaded in kernel, but %s does not exist", dev)
} else {
logf("%s: %v", dev, fi.Mode())
}
// We failed to find why it failed. Just let our
// caller report the error it got from wireguard-go.
return
}
logf("is CONFIG_TUN enabled in your kernel? `modprobe tun` failed with: %s", modprobeOut)
switch distro.Get() {
case distro.Debian:
dpkgOut, err := exec.Command("dpkg", "-S", "kernel/drivers/net/tun.ko").CombinedOutput()
if len(bytes.TrimSpace(dpkgOut)) == 0 || err != nil {
logf("tun module not loaded nor found on disk")
return
}
if !bytes.Contains(dpkgOut, kernel) {
logf("kernel/drivers/net/tun.ko found on disk, but not for current kernel; are you in middle of a system update and haven't rebooted? found: %s", dpkgOut)
}
case distro.Arch:
findOut, err := exec.Command("find", "/lib/modules/", "-path", "*/net/tun.ko*").CombinedOutput()
if len(bytes.TrimSpace(findOut)) == 0 || err != nil {
logf("tun module not loaded nor found on disk")
return
}
if !bytes.Contains(findOut, kernel) {
logf("kernel/drivers/net/tun.ko found on disk, but not for current kernel; are you in middle of a system update and haven't rebooted? found: %s", findOut)
}
case distro.OpenWrt:
out, err := exec.Command("opkg", "list-installed").CombinedOutput()
if err != nil {
logf("error querying OpenWrt installed packages: %s", out)
return
}
for _, pkg := range []string{"kmod-tun", "ca-bundle"} {
if !bytes.Contains(out, []byte(pkg+" - ")) {
logf("Missing required package %s; run: opkg install %s", pkg, pkg)
}
}
}
}

27
net/tstun/tun_macos.go
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@ -0,0 +1,27 @@
// Copyright (c) 2021 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.
//go:build darwin && !ios
// +build darwin,!ios
package tstun
import (
"os"
"tailscale.com/types/logger"
)
func init() {
tunDiagnoseFailure = diagnoseDarwinTUNFailure
}
func diagnoseDarwinTUNFailure(tunName string, logf logger.Logf) {
if os.Getuid() != 0 {
logf("failed to create TUN device as non-root user; use 'sudo tailscaled', or run under launchd with 'sudo tailscaled install-system-daemon'")
}
if tunName != "utun" {
logf("failed to create TUN device %q; try using tun device \"utun\" instead for automatic selection", tunName)
}
}
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