Fw: [Bugme-new] [Bug 3777] New: tun driver fails to open when built in, must be modular

Fw: [Bugme-new] [Bug 3777] New: tun driver fails to open when built in, must be modular

[Andrew Morton]

Begin forwarded message:

Date: Fri, 19 Nov 2004 14:19:35 -0800
From: bugme-daemon@osdl.org
To: bugme-new@lists.osdl.org
Subject: [Bugme-new] [Bug 3777] New: tun driver fails to open when built in, must be modular


http://bugme.osdl.org/show_bug.cgi?id=3777

           Summary: tun driver fails to open when built in, must be modular
    Kernel Version: 2.6.10-rc2
            Status: NEW
          Severity: normal
             Owner: jgarzik@pobox.com
         Submitter: bill@crowellsystems.com


Distribution: slackware/mfxlinux
Hardware Environment:i386
Software Environment:
Problem Description: kernel will not assign/open a tun device when tun.o is
compiled as a built-in. ifconfig gives 'unable to open /dev/net/tun' error.
compiling as a module fixes.

Steps to reproduce:
Compile kernel with tun/tap device driver as a built-in. Run ifconfig to see
error. recompile as a module, modprobe tun and run ifconfig - no error.

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Re: Fw: [Bugme-new] [Bug 3777] New: tun driver fails to open when built in, must be modular

[Michael Renzmann]

Hi.

Andrew Morton wrote:
> Problem Description: kernel will not assign/open a tun device when tun.o is
> compiled as a built-in. ifconfig gives 'unable to open /dev/net/tun' error.
> compiling as a module fixes.

If anyone can give me a small general hints for what might be the cause 
of this problem, I could take a look at it. I already have some patches 
for tun.o (that needs to be sent to the maintainer), another one doesn't 
hurt :) But since I'm not yet too experienced with programming of kernel 
modules, any help would be appreciated.

Bye, Mike

Re: Fw: [Bugme-new] [Bug 3777] New: tun driver fails to open whenbuilt in, must be modular

[shemminger]

> Hi.
>
> Andrew Morton wrote:
>> Problem Description: kernel will not assign/open a tun device when tun.o
>> is
>> compiled as a built-in. ifconfig gives 'unable to open /dev/net/tun'
>> error.
>> compiling as a module fixes.
>
> If anyone can give me a small general hints for what might be the cause
> of this problem, I could take a look at it. I already have some patches
> for tun.o (that needs to be sent to the maintainer), another one doesn't
> hurt :) But since I'm not yet too experienced with programming of kernel
> modules, any help would be appreciated.
>
> Bye, Mike
>

See if it successfully registers with the misc driver (misc_register).
I suspect it is an initialization order type thing. Probably the
code to register with the misc driver (to create the device) should
just be delayed until the network device is brought up (ie dev->open)
is called.

Good luck.