On 2/2/11 7:06 AM, Monthadar Al Jaberi wrote:
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)):

And same printf in wtap_ioctl which is called from a user space
program (I am root):

In both cases TD_TO_VNET/CRED_TO_VNET return NULL... shouldn't they
return a pointer same as curthread->td_vnet? Another thing is that in
wtap_ioctl curthread->td_vnet is NULL

that depends on where in your code you did the print..

have you read this file?

use the 'download' button to get a more readable version.

it goes into some of the details of this. especially the initialization or vimage modules.

I still get a panic...


On Tue, Feb 1, 2011 at 8:37 PM, Julian Elischer<jul...@freebsd.org>  wrote:
ok here's how it works..

any place you access a V_xxx variable you need to have the current vnet set.
so somewhere in your code path to get to that point you have to have done
CURVNET_SET() and after you have finised on the way out you should do

you can get the vnet from several places:

1/ as shown below, you can get it from any thread's cred if teh running
thread is part of a
process in the jail in question.
2/ if you have an ifp pointer, you can use ifp->vnet  .   I think that's
right, it's been a while...
3/ I believe though I may be wrong  (I may be thinking of multi FIBS)
that it maybe in the socket structure too but don't trust me on that one..
check it.

if, like in a timer thread you have access to NONE of those, you have
several choices..
1/ the caller of the timer may have given you indirect access to it in the
2/ maybe you juaast have to interate through all the vimages.. to do
whatever it is that you do
(that happens in some protocols)

On 2/1/11 11:04 AM, Monthadar Al Jaberi wrote:
On Tue, Feb 1, 2011 at 6:25 PM, Julian Elischer<jul...@freebsd.org>
On 2/1/11 8:40 AM, Monthadar Al Jaberi wrote:

I hope I am on the write place, second try...

I have written a module that loads fake wifi devices (wtap?) and
distributes packets between them. For now I use route command to route
packets between them from upper layers (TCP,...).
I want to take it to next step and create jails with VNET. I started
reading Julian Elischer's "Vimage: what is it?" and he says that if I
am writing hardware drivers I dont need to make any changes when I
enable VIMAGE option on the kernel, because each one will have their
own stack.

I can give a more detailed explanation on how my module works. But for
now I get a panic when calling if_alloc() when using option VIMAGE.

Thank you,
while this  was true to some extent it i snot 100% true now.
during allocation we now try to have separate interface indexes per
which means that the setup routines do need to know the current vnet.
so I cant call if_alloc directly?

it looks like wtap_ioctl or wtap_attach should have the following:
(copied from the tun driver)

this should not be needed from real hardware based drivers as far as I

        /* find any existing device, or allocate new unit number */
        i = clone_create(&tunclones,&tun_cdevsw,&u, dev, 0);
        if_clone_create(name, namelen, NULL);
My wtap is based on ath driver code (if_ath.c) which should look like
a real device right?
if_ath.c is not using VNET, as far as I can tell....

Currently my module creates a couple of wtaps, which I then create a
corresponding wlan. These wtaps are interconnected together, so no out
world yet... so I dont have struct cdev *dev....

Basic idea is my module have a main queue (simulating air) and each
wtap have a rx_task which sends packets up to higher layers, plus
callout timer for generation beacons...

I will try to use CURVET_SET(...) tomo

My setup:
FreeBSD Current 201010 guest on VirtualBox on Ubuntu 10.04.

Kernel page fault with the following non-sleepable locks held:
exclusive rw ifnet_rw (ifnet_rw) r = 0 (0xc0fc8284) locked @
KDB: stack backtrace:
db_trace_self_wrapper(c0cf3cdb,1,0,0,0,...) at
kdb_backtrace(19e,1,ffffffff,c0f9b194,c2fc9a1c,...) at
_witness_debugger(c0cf6408,c2fc9a30,4,1,0,...) at _witness_debugger+0x25
witness_warn(5,0,c0d2c479,3,c4070d48,...) at witness_warn+0x1fe
trap(c2fc9abc) at trap+0x195
calltrap() at calltrap+0x6
--- trap 0xc, eip = 0xc0970999, esp = 0xc2fc9afc, ebp = 0xc2fc9b1c ---
ifindex_alloc_locked(c0d003cf,c2fc9b36,19e,19e,c15ab714,...) at
if_alloc(47,c4085a16,3,c0de9614,c32aa780,...) at if_alloc+0x85
wtap_attach(c31a7800,c40857c0,0,4,0,...) at wtap_attach+0x29
new_wtap(c32aa780,0,c2fc9bf0,c083ac9b,c3cbb200,...) at new_wtap+0x9b
wtap_ioctl(c3cbb200,80045701,c31edaa0,1,c3f90b40,...) at wtap_ioctl+0x36
devfs_ioctl_f(c3cfe3b8,80045701,c31edaa0,c3185d00,c3f90b40,...) at
kern_ioctl(c3f90b40,3,80045701,c31edaa0,fc9cec,...) at kern_ioctl+0x20d
ioctl(c3f90b40,c2fc9cec,c2fc9d28,c0cf5783,0,...) at ioctl+0x134
syscallenter(c3f90b40,c2fc9ce4,c2fc9ce4,0,0,...) at syscallenter+0x263
syscall(c2fc9d28) at syscall+0x34
Xint0x80_syscall() at Xint0x80_syscall+0x21
--- syscall (54, FreeBSD ELF32, ioctl), eip = 0x28181203, esp =
0xbfbfec3c, ebp = 0xbfbfec58 ---

Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address   = 0x18
fault code              = supervisor read, page not present
instruction pointer     = 0x20:0xc0970999
stack pointer           = 0x28:0xc2fc9afc
frame pointer           = 0x28:0xc2fc9b1c
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 1203 (ioctl)
panic: from debugger
cpuid = 0
Uptime: 21s
Physical memory: 495 MB
Dumping 55 MB: 40 24 8

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