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wgengine: remove Config.TUNName, require caller to create device.

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Also factors out device creation and associated OS workarounds to
net/tun.

Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson
2021-03-26 21:03:21 -07:00
committed by Dave Anderson
parent 0a84aaca0a
commit 44d9929208
7 changed files with 167 additions and 148 deletions
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137
wgengine/userspace.go
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@@ -14,7 +14,6 @@ import (
"io"
"net"
"os"
"os/exec"
"runtime"
"strconv"
"strings"
@@ -43,7 +42,6 @@ import (
"tailscale.com/types/netmap"
"tailscale.com/types/wgkey"
"tailscale.com/version"
"tailscale.com/version/distro"
"tailscale.com/wgengine/filter"
"tailscale.com/wgengine/magicsock"
"tailscale.com/wgengine/monitor"
@@ -53,16 +51,6 @@ import (
"tailscale.com/wgengine/wglog"
)
// minimalMTU is the MTU we set on tailscale's TUN
// interface. wireguard-go defaults to 1420 bytes, which only works if
// the "outer" MTU is 1500 bytes. This breaks on DSL connections
// (typically 1492 MTU) and on GCE (1460 MTU?!).
//
// 1280 is the smallest MTU allowed for IPv6, which is a sensible
// "probably works everywhere" setting until we develop proper PMTU
// discovery.
const minimalMTU = 1280
const magicDNSPort = 53
var magicDNSIP = netaddr.IPv4(100, 100, 100, 100)
@@ -150,13 +138,8 @@ type RouterGen func(logf logger.Logf, tundev tun.Device) (router.Router, error)
// Config is the engine configuration.
type Config struct {
// TUN is the TUN device used by the engine.
// Exactly one of either TUN or TUNName must be specified.
TUN tun.Device
// TUNName is the TUN device to create.
// Exactly one of either TUN or TUNName must be specified.
TUNName string
// RouterGen is the function used to instantiate the router.
// If nil, wgengine/router.New is used.
RouterGen RouterGen
@@ -186,42 +169,18 @@ func NewFakeUserspaceEngine(logf logger.Logf, listenPort uint16) (Engine, error)
// NewUserspaceEngine creates the named tun device and returns a
// Tailscale Engine running on it.
func NewUserspaceEngine(logf logger.Logf, conf Config) (Engine, error) {
if conf.TUN != nil && conf.TUNName != "" {
return nil, errors.New("TUN and TUNName are mutually exclusive")
func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error) {
if conf.TUN == nil {
return nil, errors.New("TUN is required")
}
if conf.TUN == nil && conf.TUNName == "" {
return nil, errors.New("either TUN or TUNName are required")
}
tunDev := conf.TUN
var err error
if tunName := conf.TUNName; tunName != "" {
logf("Starting userspace wireguard engine with tun device %q", tunName)
tunDev, err = tun.CreateTUN(tunName, minimalMTU)
if err != nil {
diagnoseTUNFailure(tunName, logf)
logf("CreateTUN: %v", err)
return nil, err
}
logf("CreateTUN ok.")
if err := waitInterfaceUp(tunDev, 90*time.Second, logf); err != nil {
return nil, err
}
}
if conf.RouterGen == nil {
conf.RouterGen = router.New
}
return newUserspaceEngine(logf, tunDev, conf)
}
func newUserspaceEngine(logf logger.Logf, rawTUNDev tun.Device, conf Config) (_ Engine, reterr error) {
var closePool closeOnErrorPool
defer closePool.closeAllIfError(&reterr)
tsTUNDev := tstun.WrapTUN(logf, rawTUNDev)
tsTUNDev := tstun.WrapTUN(logf, conf.TUN)
closePool.add(tsTUNDev)
e := &userspaceEngine{
@@ -1554,94 +1513,6 @@ func (e *userspaceEngine) peerForIP(ip netaddr.IP) (n *tailcfg.Node, err error)
return nil, fmt.Errorf("node %q found, but not using its %v route", bestInNM.ComputedNameWithHost, bestInNMPrefix)
}
// diagnoseTUNFailure is called if tun.CreateTUN fails, to poke around
// the system and log some diagnostic info that might help debug why
// TUN failed. Because TUN's already failed and things the program's
// about to end, we might as well log a lot.
func diagnoseTUNFailure(tunName string, logf logger.Logf) {
switch runtime.GOOS {
case "linux":
diagnoseLinuxTUNFailure(tunName, logf)
case "darwin":
diagnoseDarwinTUNFailure(tunName, logf)
default:
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)
}
}
}
}
type closeOnErrorPool []func()
func (p *closeOnErrorPool) add(c io.Closer) { *p = append(*p, func() { c.Close() }) }