Cannot open TUN/TAP dev error

[Stephen Becker]

Short question: what is the best script to run the modprobe tun command to ensure tun devices are setup after reboot? It does not appear to work correctly when included in services-start

Long version with background:
I am using fastd to setup an IP tunnel to another Asus-Merlin router, but ran into an issue where the service does not start correctly after a reboot. The error says "could not open TUN/TAP device file: No such file or directory"

The command modprobe tun creates /dev/tun and /dev/net/tun allowing the service to start, however, only when I run the command manually. I have tried adding that command to /jffs/scripts/services-start before Entware is called, but it does not work. It creates /dev/tun but not /dev/net/tun.

I suspect either a kernel mod has not yet loaded, or the firmware does something shortly after boot that resets network devices.

Any advice on how to fix this? I could probably have the script sleep an arbitrary amount of time before running modprobe and starting Entware, but I would like a more graceful solution. Also not entirely sure if the services-start script blocks anything else on the router that may make sleeping just postpone the same issue.

 

[Stephen Becker]

Here is a services-start script I got working. It did not work until I added those longer sleeps. For some reason with a simple 1 second sleep it was testing positive for the mod loading, but then the mod would unload again. Probably something the firmware was doing at the same time.

#!/bin/sh

RC='/opt/etc/init.d/rc.unslung'
sleep 30

i=12
until [ "$(lsmod | grep tun)" ] ; do
  i=$(($i-1))
  if [ "$i" -lt 1 ] ; then
    logger "Could not load tun mod"
    break
  fi
  modprobe tun
  sleep 10
done

i=30
until [ -x "$RC" ] ; do
  i=$(($i-1))
  if [ "$i" -lt 1 ] ; then
    logger "Could not start Entware"
    exit
  fi
  sleep 1
done

$RC start