How to modify IP payload (UDP checksum)?

Hello,

 

 

This may be a novice question, but how does one modify IP payload? I need to modify UDP checksum in a packet, alas this seems close to impossible. UDP has UDP::payload, as does TCP, but IP doesn't?

 

 

Would replacing the payload with original payload force calculation of a checksum, like so:

 

 

when CLIENT_DATA {

 

set length [UDP::payload length]

 

set payload [UDP::payload]

 

UDP::payload replace 0 0 $payload

 

}

 

 

Thanks!

 

 

Pawel