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net/tstun: don't exec uname -r on Linux in TUN failure diagnostics

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Fixes https://twitter.com/zekjur/status/1425557520513486848

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2021-08-16 12:18:06 -07:00
parent e804ab29fd
commit 833200da6f
1 changed files with 18 additions and 4 deletions
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22
net/tstun/tun_linux.go
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@ -8,6 +8,8 @@ import (
"bytes" "bytes"
"os" "os"
"os/exec" "os/exec"
"strings"
"syscall"
"tailscale.com/types/logger" "tailscale.com/types/logger"
"tailscale.com/version/distro" "tailscale.com/version/distro"
@ -18,12 +20,13 @@ func init() {
} }
func diagnoseLinuxTUNFailure(tunName string, logf logger.Logf) { func diagnoseLinuxTUNFailure(tunName string, logf logger.Logf) {
kernel, err := exec.Command("uname", "-r").Output() var un syscall.Utsname
kernel = bytes.TrimSpace(kernel) err := syscall.Uname(&un)
if err != nil { if err != nil {
logf("no TUN, and failed to look up kernel version: %v", err) logf("no TUN, and failed to look up kernel version: %v", err)
return return
} }
kernel := utsField(&un.Release)
logf("Linux kernel version: %s", kernel) logf("Linux kernel version: %s", kernel)
modprobeOut, err := exec.Command("/sbin/modprobe", "tun").CombinedOutput() modprobeOut, err := exec.Command("/sbin/modprobe", "tun").CombinedOutput()
@ -55,7 +58,7 @@ func diagnoseLinuxTUNFailure(tunName string, logf logger.Logf) {
logf("tun module not loaded nor found on disk") logf("tun module not loaded nor found on disk")
return return
} }
if !bytes.Contains(dpkgOut, kernel) { if !bytes.Contains(dpkgOut, []byte(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) 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: case distro.Arch:
@ -64,7 +67,7 @@ func diagnoseLinuxTUNFailure(tunName string, logf logger.Logf) {
logf("tun module not loaded nor found on disk") logf("tun module not loaded nor found on disk")
return return
} }
if !bytes.Contains(findOut, kernel) { if !bytes.Contains(findOut, []byte(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) 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: case distro.OpenWrt:
@ -80,3 +83,14 @@ func diagnoseLinuxTUNFailure(tunName string, logf logger.Logf) {
} }
} }
} }
func utsField(p *[65]int8) string {
var sb strings.Builder
for _, v := range p {
if v == 0 {
break
}
sb.WriteByte(byte(v))
}
return strings.TrimSpace(sb.String())
}