Also factors out device creation and associated OS workarounds to net/tun. Signed-off-by: David Anderson <danderson@tailscale.com>main
David Anderson
5 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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