simulating wireless device (if_alloc panic, VirtualBox, VIMAGE)

[Monthadar Al Jaberi]

On Tue, Feb 1, 2011 at 6:25 PM, Julian Elischer <julian at freebsd.org> wrote:
> On 2/1/11 8:40 AM, Monthadar Al Jaberi wrote:
>>
>> Hi,
>>
>> 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 vimage
> 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 can
> tell.
>
>        CURVNET_SET(CRED_TO_VNET(cred));
>        /* find any existing device, or allocate new unit number */
>        i = clone_create(&tunclones, &tun_cdevsw, &u, dev, 0);
>        [blah]
>        if_clone_create(name, namelen, NULL);
>        CURVNET_RESTORE();

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 @
>> /usr/src/sys/net/if.c:414
>> KDB: stack backtrace:
>> db_trace_self_wrapper(c0cf3cdb,1,0,0,0,...) at db_trace_self_wrapper+0x26
>> kdb_backtrace(19e,1,ffffffff,c0f9b194,c2fc9a1c,...) at kdb_backtrace+0x2a
>> _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
>> ifindex_alloc_locked+0x19
>> 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
>> devfs_ioctl_f+0x10b
>> 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
>>
>
>



-- 
//Monthadar Al Jaberi