Re: [mpls-linux-general] regarding sk_buff structure....

[Abhijit G. <gab...@ee...>]

If you want to send the packet to user-space application, mpls_sendmsg is
perhaps not the way you shd to it. Well what i think is happening is (its
most likely like that, i m not sure)

mpls_sendmsg or subsequent calls from it (if any) are refering to skb->dev
or skb->dst somewhere. And its likely that these are not set properly.

Also you can have a look at the sources of tun-tap device in drivers/net/
to check how to send packets to userspace. (Excellent stuff! I have seen
so far).

hth

-abhijit

vvk...@hs... wrote :

>
>
>Hi  Experts !
>
>     I have come across with one problem that , i want to get the packet  and
>send it to an application ,
>running in user space ..........  My objective is to get the  SHIM ,src,dest
>address and packet data ........
>
>  I am following  style.......................of code.
>
>#define MPLS_MAX_BUFF_SIZE   1500
>#define MPLS_MAX_DATA_SIZE   1500 - 4* sizeof ( unsigned long ) -1
>
>int  mpls_get_packet_data( struct sk_buff *skb,    unsigned long shim,
>                  int type )
>{
>   char        *fname="mpls_get_packet_data";
>   mpls_info_t *buff=NULL;
>
>      printk(KERN_ALERT"%s : entering .....\n",fname);
>
>      buff=(mpls_info_t *)kmalloc(sizeof(mpls_info_t), GFP_KERNEL);
>      if ( buff == NULL )
>      {
>         printk(KERN_ALERT"%s: kmalloc error",fname);
>         return -ENOMEM;
>      }
>
>      if ( skb == NULL )
>      {
>         printk(KERN_ALERT"%s: skb NULL argument error",fname);
>         kfree(buff);
>         return -EINVAL;
>      }
>
>      /* Now get the  "src", "fec ..i.e dest address",
>       * "data" from sk_buff structure .........
>       * Fill it in the "mpls_info_t" structure...
>       * and place the msg in the queue .......
>       */
>
>
>       buff->type = type;  /* Label Type ...IN or OUT Label */
>       buff->shim = shim;  /* fill the SHIM info .......*/
>       buff->src  = skb->nh.iph->saddr;  /* src address from sk_buff */
>       buff->fec  = skb->nh.iph->daddr;  /* dest address from sk_buff */
>       memset(buff->data, 0, MPLS_MAX_DATA_SIZE-1);
>
>       if ( skb->data != NULL )
>       {
>             printk(KERN_ALERT"%s: skb data length [%d]\n",fname,skb->len);
>             memcpy(buff->data, skb->data, skb->len);
>       }
>
>       return mpls_sendmsg(buff, MPLS_MAX_BUFF_SIZE);
> }
>
>This function i am calling in the "mpls_output2"  function in the file :  "
>mpls_output.c" file of mpls
>src for kinux............
>
>here problem is .........  after some time  kernel  panic msg arriving and
>system is hanging up ....
>no response ............    Error is : invalid operand : 00000
>
>Is the way i am following is correct or not ?
>Can  you  please guide me , how to retrieve the data............from  "sk_buff"
>structure ...............?
>
>Please guide me in this ..............
>
>I am following the Linux Device Drivers book by oerilly .. by alessandro
>rubini............
>
>Thanks in advance........
>Regards,Ramki kvv.
>
>Hughes Software Systems