skb->data bytes

skb->data bytes

[Sandhya Rallapalli]

Hi,
    As a part of my research work, I've been working on introduction of
bit errors into packets. The main purpose is to choose a random byte
from (skb->head) to (skb->tail) (header & data) and change a bit in the
selected byte. And then, I test the throughput variation according to
the variation in ber using ttcp.

Here, I face a problem:
If a random byte within (skb->head) and (skb->data + 65) is chosen, the 
throughput is acceptable. But, if a byte outside (skb->head) to 
(skb->data + 65) is chosen, the transmission stops. The link becomes 
congested and netstat shows a non-changing number of bytes in Send-Q 
section. i.e., (skb->data + 66) to (skb->tail) are not allowed to be erred.
Is there any significance to the 65th byte and beyond in skb->data?

Thanks,
-Sandhya.

Re: skb->data bytes

[David S. Miller]

You've corrupted the data therefore you have to correct the checksum
in the TCP header.  You can't just randomly corrupt data and expect
the checksums to still pass.