simulating wireless device (if_alloc panic, VirtualBox, VIMAGE)

Thu Feb 3 10:00:24 UTC 2011

On Thu, 3 Feb 2011, Monthadar Al Jaberi wrote:

> On Wed, Feb 2, 2011 at 8:06 PM, Julian Elischer <julian at freebsd.org> wrote:
>> On 2/2/11 10:05 AM, Monthadar Al Jaberi wrote:
>>>
>>> I just tried something that seems to work, but please dont hit me ^^;;;
>>>
>>> in wtap_ioctl I assigned curthread->td_vnet myself to point to a VNET
>>> (saved it when the module first loaded) (I have not created any jails
>>> yet)... and it works... I didnt put any CURVNET macros...
>>
>> td->td_vnet is exactly what the CURVNET_SET macro sets.
>> You should use the Macros because we may change the place where we store it.
>>
>> The vnet for the current thread is picked up from several places depending
>> on the context,
>> and it is cleared again when it is not needed.  the V_xxx usages in the code
>> end up being
>> in effect expanded to curthread->td_vnet.xxx, where each 'xxx' is sort of
>> like an element in a structure
>> but not quite.
>>
>> Now, theoretically we could just leave it set all the time but then it would
>> be nearly impossible
>> to find places where we should have changed it, but forgot and just got the
>> existing one.
>>
>> if you want to find the correct place to go, then look at the vnet of the
>> calling process
>> which should be in the process cred. or just use vnet0.
>
> Can I check it from user space?
>
>>
>> I don't understand why you saw a CRED_TO_VNET of 0
>> I was under the impression that every process/thread in the system would be
>> on vnet0
>> in a vimage kernel.
>
> This is how my printf looks like:
> struct thread *td = curthread;
> struct vnet *v = TD_TO_VNET(td);
> struct ucred *cred = CRED_TO_VNET(td->ucred);
> struct vnet *td_vnet = td->td_vnet;

here's your problem:

strcut vnet *vnet = cred->cr_prison->pr_vnet;

> printf("td=%p, td->td_vnet=%p, td->td_ucred=%p, TD_TO_VNET=%p,
> CRED_TO_VNET=%p\n", td, td_vnet, td->td_ucred, v, cred);
>
> I made a fast search in /usr/src for "td_vnet" and found it was
> assigned only in
> int fork1(td, flags, pages, procp):
> #ifdef VIMAGE
> 	td2->td_vnet = NULL;
> 	td2->td_vnet_lpush = NULL;
> #endif

Nice try.  Want another search?  Hint: there is this in vnet.h:

#define curvnet curthread->td_vnet

And then you'll, again, find the CURVNET_SET_* macros.

> Maybe something wrong with how I declare my wtap_ioctl:
>
> static struct cdevsw wtap_cdevsw = {
> 	.d_version =	D_VERSION,
> 	.d_flags =	0,
> 	.d_ioctl =	wtap_ioctl,
> 	.d_name =	"wtapctl",
> };
> ...
> make_dev(&wtap_cdevsw,0,UID_ROOT,GID_WHEEL,0600,(const char *)"wtapctl");
>
>>
>> your stored vnet idea is ok as well, but may go strange if you load the
>> driver from a vnet jail
>> and then remove the jail.
>
> Ok, will document it in the code for now
>
>>
>>
>>
>>
>>> my assumption is that if ath drivers dont use VNET I shouldnt :P
>>>
>>> What is wrong with this hack?
>>>
>>> br,
>>>
>>> P.S. I have printed "porting to vnet" text to have it always at hand,
>>> but its a bit hard for me... doing my best.
>>>
>>> On Wed, Feb 2, 2011 at 6:30 PM, Julian Elischer<julian at freebsd.org>
>>>  wrote:
>>>>
>>>> On 2/2/11 9:12 AM, Bjoern A. Zeeb wrote:
>>>>>
>>>>> On Wed, 2 Feb 2011, Monthadar Al Jaberi wrote:
>>>>>
>>>>> Hi,
>>>>>
>>>>>> Thanx makes more sense, but I have noticed something weired if you can
>>>>>> shade some light on.
>>>>>>
>>>>>> I added printfs one when the module is first loaded (static int
>>>>>> event_handler(module_t module, int event, void *arg)):
>>>>>> curthread=0xc3f95870
>>>>>> curthread->td_vnet=0xc3170e00
>>>>>> curthread->td_ucred=0xc3185d00
>>>>>> TD_TO_VNET=0
>>>>>> CRED_TO_VNET=0
>>>>>
>>>>> Try to load it from laoder on boot; I think that should work as we are
>>>>> setting the curvent for the kernel startup.
>>>>>
>>>>> The problem you are seeing is a bug in the current implementation that
>>>>> you cannot add any physical network interface after the kernel started.
>>>>> This applies to cardbus/usb/... as well as any kind of ethernet
>>>>> interface, so a kldload igb should yield it as well.
>>>>>
>>>>> The fix for that is easy and hard at the same time:
>>>>> A) either touch all drivers
>>>>> B) or touch all cloned interfaces and change 3 common lines.
>>>>>   or try to make cloners aware of vimages.
>>>>>
>>>>> Solution B) is sitting in perforce with the entire stuff that it depends
>>>>> on and was started with CH=179022,179255 but not limited to that if you
>>>>> want to have a peek.
>>>>>
>>>>> What you certainly can do locally to your driver for now is to make a
>>>>> change like this:
>>>>>
>>>>> +#ifdef VIMAGE
>>>>> +       CURVNET_SET(vnet0);
>>>>> +#endif
>>>>>        ifp = if_alloc(IFT_ETHER);
>>>>> +#ifdef VIMAGE
>>>>> +       CURVNET_RESTORE();
>>>>> +#endif
>>>>>
>>>> you don't really need  the #ifdef except for readability as CURVNET_XXX
>>>> ar
>>>> enot defined for !vnet
>>>>
>>>>> It's the type A) kind of change from above that will break eventually
>>>>> in the future.
>>>>>
>>>>> /bz
>>>>>
>>>>
>>>
>>>
>>
>>
>
>
>
>

-- 
Bjoern A. Zeeb                                 You have to have visions!
         <ks> Going to jail sucks -- <bz> All my daemons like it!
   http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/jails.html