Re: problems with netlink_broadcast

[pablo neira <pablo@eurodev.net>]

Hi John,

John Williams Floroiu wrote:

> void uk_task(void *arg) {
>
>         local_bh_disable();
>         printk(KERN_INFO "--- calling netlink_broadcast ---\n");
>         netlink_broadcast(uknl, (struct sk_buff *)arg, 0, UKGRP_TEST, 
> GFP_ATOMIC);
>         local_bh_enable();
>         printk(KERN_INFO "### uk_task terminates ###\n");
> }
>
> void uk_timer_handler(unsigned long arg){
>
>         struct nlmsghdr *nl;
>         struct sk_buff *skb;
>
>         uktimer.expires = jiffies + HZ/2;
>         add_timer(&uktimer);
>
>         skb = alloc_skb(NLMSG_SPACE(256), GFP_ATOMIC);
>         if (!skb) {
>                 printk(KERN_INFO "### uk_task skb allocation failure 
> ###\n");
>                 return;
>         }
>         NLMSG_PUT(skb, 0, 0, UK_NOTIF_TEST, 0); 


I think that you are trying to create a skbuff with no netlink header 
because you set last parameter of NLMSG_PUT to 0.

Set it to:
NLMSG_SPACE(256) - sizeof(struct nlmsghdr)

Have a look at the function __nlmsg_put which is called by the macro 
NLMSG_PUT:
http://lxr.linux.no/source/include/linux/netlink.h#L141

Anyway, if it doesn't work have a look at ip_queue.c and ipt_ULOG.c. It 
could help you out.

cheers,
Pablo

>
>         NETLINK_CB(skb).dst_groups = UKGRP_TEST;
>         printk(KERN_INFO "### skb->len = %d ###\n", skb->len);
>
>         uk_work.data = skb;
>         schedule_work(&uk_work);
>         printk(KERN_INFO "### uk_timer_handler terminates ###\n");
>
>         return;
>
> nlmsg_failure:
>         skb_trim(skb, skb->tail - skb->data);
>         printk(KERN_INFO "### uk_task NLMSG_PUT failure ###\n");
> }
>
> ----------------------------------------------------------------
>
> Unable to handle kernel paging request at virtual address f6a34fb0
>   printing eip:
>  f88233ca
>  *pde = 00488067
>  *pte = 36a34000
>  Oops: 0000 [#1]
>  CPU:    1
>  EIP:    0060:[__crc_utf8_wctomb+5448385/6417782]    Not tainted
>  EFLAGS: 00010246
>  EIP is at uk_task+0xda/0x160 [uk]
>  eax: 00000000   ebx: f6a34f4c   ecx: 00000000   edx: fffffffd
>  esi: f2f1fbf8   edi: f8824460   ebp: c1a95f64   esp: c1a95f48
>  ds: 007b   es: 007b   ss: 0068
>  Process events/1 (pid: 7, threadinfo=c1a94000 task=c1a619b0)
>  Stack: f2fa7e94 f6a34f4c 00000000 00000159 00000020 c1a94000 f8824464 
> c1a95fec
>         c01370f6 00000000 c1a95fa0 00000000 c1a64f90 c1a64fa0 00000000 
> f88232f0
>         00000212 c1a64f88 c1a64f78 5a5a5a5a 5a5a5a5a 5a5a5a5a 00000001 
> 00000000
>  Call Trace:
>   [worker_thread+534/960] worker_thread+0x216/0x3c0
>   [__crc_utf8_wctomb+5448167/6417782] uk_task+0x0/0x160 [uk]
>   [default_wake_function+0/32] default_wake_function+0x0/0x20
>   [ret_from_fork+6/20] ret_from_fork+0x6/0x14
>   [default_wake_function+0/32] default_wake_function+0x0/0x20
>   [worker_thread+0/960] worker_thread+0x0/0x3c0
>   [kernel_thread_helper+5/24] kernel_thread_helper+0x5/0x18
>
>  Code: 8b 43 64 c7 04 24 a0 36 82 f8 89 44 24 04 e8 73 10 90 c7 83
>
>
>
>
>