[Xen-devel] Reading network data from netback.c

[#PATHANGI JANARDHANAN JATINSHRAVAN# <JATINSHR001@xxxxxxxxxxxx>]

Hi all, 

Recently, I’ve been trying to modify netback.c to print network data that is going into the VM. For example, I’m doing an SSL handshake with the VM as the server, and I send the following hexadecimal string from the client to the VM:

160302002f0100002b03026161616161616161616161616161616161616161616161616161616161616161000002000501000000

Now,  to read this ingoing data to the VM from netback.c, I’ve been trying to get the sk_buff from the function xenvif_rx_action() and extract the TCP header from it using the tcp_hdr(skb) function. 

I then try to get the data from the TCP header using the line: (unsigned char *)((unsigned char *)tcph + (tcph->doff * 4))

But I am not able to parse the hexadecimal string as shown above. Printing the userdata portion of the sk_buff, I notice that I get things like the below:

\xffffffe9\xffffffe9

0CNCL-FYP03G\xffffff88\xffffffff\xffffffff\xfff\xffffff81\xffffffff\xffffffff\xffffffff\xffffffff\xffffffe8\xffffffbd|G\xffffff88\xffffffff\xffffffff)G\xffffff81\xffffffff\xffffffff\xffffffff\xffffffff 

The above data was truncated to 104 bytes.

Can anyone point me in the right direction regarding this and how to read the above data?

Thanks

Jatin

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