mirror of https://github.com/tailscale/tailscale/
wgengine: remove Config.TUNName, require caller to create device.
Also factors out device creation and associated OS workarounds to net/tun. Signed-off-by: David Anderson <danderson@tailscale.com>pull/1595/head
David Anderson
4 years ago
committed by
Dave Anderson
parent
0a84aaca0a
commit
44d9929208
@ -0,0 +1,128 @@
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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 tun creates a tuntap device, working around OS-specific
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// quirks if necessary.
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package tun
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import (
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"bytes"
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"os"
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"os/exec"
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"runtime"
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"time"
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"github.com/tailscale/wireguard-go/tun"
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"tailscale.com/types/logger"
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"tailscale.com/version/distro"
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)
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// minimalMTU is the MTU we set on tailscale's TUN
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// interface. wireguard-go defaults to 1420 bytes, which only works if
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// the "outer" MTU is 1500 bytes. This breaks on DSL connections
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// (typically 1492 MTU) and on GCE (1460 MTU?!).
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//
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// 1280 is the smallest MTU allowed for IPv6, which is a sensible
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// "probably works everywhere" setting until we develop proper PMTU
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// discovery.
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const minimalMTU = 1280
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func New(logf logger.Logf, tunName string) (tun.Device, error) {
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dev, err := tun.CreateTUN(tunName, minimalMTU)
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if err != nil {
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return nil, err
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}
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if err := waitInterfaceUp(dev, 90*time.Second, logf); err != nil {
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return nil, err
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}
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return dev, nil
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}
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// Diagnose tries to explain a tuntap device creation failure.
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// It pokes around the system and logs some diagnostic info that might
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// help debug why tun creation failed. Because device creation has
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// already failed and the program's about to end, log a lot.
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func Diagnose(logf logger.Logf, tunName string) {
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switch runtime.GOOS {
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case "linux":
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diagnoseLinuxTUNFailure(tunName, logf)
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case "darwin":
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diagnoseDarwinTUNFailure(tunName, logf)
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default:
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logf("no TUN failure diagnostics for OS %q", runtime.GOOS)
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}
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}
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func diagnoseDarwinTUNFailure(tunName string, logf logger.Logf) {
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if os.Getuid() != 0 {
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logf("failed to create TUN device as non-root user; use 'sudo tailscaled', or run under launchd with 'sudo tailscaled install-system-daemon'")
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}
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if tunName != "utun" {
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logf("failed to create TUN device %q; try using tun device \"utun\" instead for automatic selection", tunName)
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}
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}
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func diagnoseLinuxTUNFailure(tunName string, logf logger.Logf) {
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kernel, err := exec.Command("uname", "-r").Output()
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kernel = bytes.TrimSpace(kernel)
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if err != nil {
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logf("no TUN, and failed to look up kernel version: %v", err)
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return
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}
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logf("Linux kernel version: %s", kernel)
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modprobeOut, err := exec.Command("/sbin/modprobe", "tun").CombinedOutput()
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if err == nil {
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logf("'modprobe tun' successful")
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// Either tun is currently loaded, or it's statically
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// compiled into the kernel (which modprobe checks
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// with /lib/modules/$(uname -r)/modules.builtin)
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//
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// So if there's a problem at this point, it's
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// probably because /dev/net/tun doesn't exist.
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const dev = "/dev/net/tun"
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if fi, err := os.Stat(dev); err != nil {
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logf("tun module loaded in kernel, but %s does not exist", dev)
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} else {
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logf("%s: %v", dev, fi.Mode())
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}
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// We failed to find why it failed. Just let our
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// caller report the error it got from wireguard-go.
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return
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}
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logf("is CONFIG_TUN enabled in your kernel? `modprobe tun` failed with: %s", modprobeOut)
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switch distro.Get() {
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case distro.Debian:
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dpkgOut, err := exec.Command("dpkg", "-S", "kernel/drivers/net/tun.ko").CombinedOutput()
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if len(bytes.TrimSpace(dpkgOut)) == 0 || err != nil {
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logf("tun module not loaded nor found on disk")
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return
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}
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if !bytes.Contains(dpkgOut, kernel) {
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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)
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}
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case distro.Arch:
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findOut, err := exec.Command("find", "/lib/modules/", "-path", "*/net/tun.ko*").CombinedOutput()
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if len(bytes.TrimSpace(findOut)) == 0 || err != nil {
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logf("tun module not loaded nor found on disk")
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return
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}
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if !bytes.Contains(findOut, kernel) {
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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)
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}
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case distro.OpenWrt:
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out, err := exec.Command("opkg", "list-installed").CombinedOutput()
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if err != nil {
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logf("error querying OpenWrt installed packages: %s", out)
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return
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}
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for _, pkg := range []string{"kmod-tun", "ca-bundle"} {
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if !bytes.Contains(out, []byte(pkg+" - ")) {
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logf("Missing required package %s; run: opkg install %s", pkg, pkg)
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}
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}
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}
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}
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