[LARTC] Modify the TCP Window size

[LARTC] Modify the TCP Window size

[Ricardo Leite]

Hi lartc users,

When a packet arrived to a network device it was stored on a skb structure 
and then enqueue on a network stack.

One of the tests that I want to do is modify the TCP window size and verify 
the changes on the bandwidth between two hosts.
To do that I need to know how to modify de packet window size and maybe 
recalculate the checksum value of the TCP packet.

All I can do is read the information of the packet stored on the skb 
structure.

Do you have any ideas? I'll need to be enlighted



Ricardo

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Re: [LARTC] Modify the TCP Window size

[Ed Wildgoose]

Ricardo Leite wrote:

> Hi lartc users,
>
> When a packet arrived to a network device it was stored on a skb 
> structure and then enqueue on a network stack.
>
> One of the tests that I want to do is modify the TCP window size and 
> verify the changes on the bandwidth between two hosts.
> To do that I need to know how to modify de packet window size and 
> maybe recalculate the checksum value of the TCP packet.
>
> All I can do is read the information of the packet stored on the skb 
> structure.


I think I saw a patch in patchomatic for iptables to modify window 
size.  Perhaps have a look at that and see if it offers you some clues.  
I seem to remember the answer is in the ACK packets sent back to the server?

Ed W
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