Re: Getting the Received Packet's Sender (IP) Address

On Fri, 2007-01-05 at 15:48 +0000, Siva Sivavakeesar wrote:
> However, I have been having
> trouble finding the received packets IP and MAC address together.
> Although conceptually wrong, I am trying to get the sender's IP
> address for every packet a node receives at the MAC (driver) level.
> For this purpose, I have added the follwing code under ipw_rx() of
> ipw2200.c.
> 
>     static void ipw_rx(struct ipw_priv *priv)
>    {   .
>        :
>        struct iphdr *iph;
>        .
>        :
>        iph = (struct iphdr *) rxb->skb->nh.iph;
> 
>        if (iph != NULL) {
> 
>           saddr = iph->saddr;
>       }
> 
>        .
>        :
> }

You cannot reference ip address this way here, since this the lower
layer of IP stack. the skb->nh.iph is assigned value in the IP stack.

> However, since "iph" always returns NULL, I am not able to find the
> sender's IP address of a packet/frame received. Can you please let me
> know whether accessing the IPHdr information is possible at the driver
> (MAC) level. If not, how can I get around with this problem. 

If you would really want to get IP address here you should parse IEEE
802.11, SNAP and IP protocol (if it is a IP packet) yourself. The
beginning address is skb->data.

Thanks,
-yi

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