netdev - cc: Re: skb configured but can't get data allocated

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Message-id: <200709122341418320c60701@mail.smumn.edu>
Date:	Wed, 12 Sep 2007 18:41:41 -0500
From:	DHAJOGLO <DHAJOGLO@...mn.edu>
To:	Vlad Yasevich <vladislav.yasevich@...com>
cc:	kernelnewbies@...linux.org, macnish@...il.com,
	netdev@...r.kernel.org
Subject: cc: Re: skb configured but can't get data allocated

To All, Thanks for the help.  I ended up adding my data packet after the ip headers and then updated the IP length:

 /* Allocate space for our exp_packet data payload and set the data */
        d_out = (struct exp_packet *)skb_put(skb,sizeof(struct exp_packet));
        d_out->headbits = (reply<<4) & 0xF0;
        d_out->sequence = pkthr.m_seq;
        d_out->payload = htons(pkthr.p_hash);

        /* adjust the total length of this IP packet */
        iplen = skb->tail - (unsigned char *)skb->nh.iph;
        iph->tot_len = htons(iplen);
        ip_send_check(iph);

This is my first venture into the kernel!

On Wednesday, September 12, 2007  3:12 PM, Vlad Yasevich wrote:
>
>Date: Wed, 12 Sep 2007 16:12:37 -0400
>From: Vlad Yasevich
>To: DHAJOGLO <DHAJOGLO@...mn.edu>
>Subject: Re: skb configured but can't get data allocated
>
>You may want to read this page:
>http://vger.kernel.org/~davem/skb.html
>
>You will then see you problem.
>
>Essentially, you are writing your data into an
>area that is never sent.
>
>What you are end up is this:
>
>---------------------------------------------
>| your data| space | ll-header | IPv4 header|
>---------------------------------------------
>
>-vlad



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