Re: if_tun module doesn't autoload if opening /dev/tunN

[Paul Goyette <paul%whooppee.com@localhost>]

FWIW, even if you manually create the tun0 interface with ifconfig, it 
is not accessible via /dev/tun0 - accessing the /dev/tun0 node results 
in ENXIO (errno == 6, Device not configured).

I suspect that similar issues may well exist with other "cloners" such 
as if_tap ...  (Note that if_gif, if_gre, if_ppp, and if_pppoe do not 
claim to be accessible via /dev so there shouldn't be any problems...)

I'll try to have a look at these sometime in the next few days, but if 
anyone else wants to dive in, please don't hesitate!  :)



On Wed, 7 Sep 2016, Paul Goyette wrote:

> According to the tun(4) man page, you can create an interface "by using the 
> ifconfig(8) create command" and this works just fine.  The man page goes on 
> to say "An open() call on /dev/tunN, will also create a network interface..." 
> but this does not work.
>
> I think this is because the code in sys/miscfs/specfs/spec_vnops.c assumes 
> that the module name is the same as the device name, ie it expects that 
> /dev/tunN will be handled by module tun.kmod  However, the module is actually 
> named if_tun.kmod so it never gets loaded, and the open() fails.
>
> I can see a couple of ways to "fix" this:
>
> 	1. Rename the module (with all appropriate updates to the
> 	   sets lists in src/distrib/sets/lists), or
> 	2. Add code to spec_vnops.c to try loading module if_xxx if the
> 	   autoload of module xxx fails.
>
> Comments?  Preferences?  Any other options I haven't yet seen?
>
>
> +------------------+--------------------------+------------------------+
> | Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:      |
> | (Retired)        | FA29 0E3B 35AF E8AE 6651 | paul at whooppee.com   |
> | Kernel Developer | 0786 F758 55DE 53BA 7731 | pgoyette at netbsd.org |
> +------------------+--------------------------+------------------------+

+------------------+--------------------------+------------------------+
| Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:      |
| (Retired)        | FA29 0E3B 35AF E8AE 6651 | paul at whooppee.com   |
| Kernel Developer | 0786 F758 55DE 53BA 7731 | pgoyette at netbsd.org |
+------------------+--------------------------+------------------------+