[Click] click_tcp

[Sofia Rodriguez]

Hi!
I am creating an element (based on another one) where I receive a packet and queue it,. Afterwards I receive an ACK and compare if the queued packet matches the received ack. If so, the packet is dropped. My problem comes with the click_tcp struct, because whenever I use it for the queued packet, everything works, but when I try to use the set pointer for the tcp packet of the incoming ack, it does not work. The pointer is pointing to the beginning of the header, but when I try to use for example tcph->seq, it points to null and causes me segmentation error.
Do you have any idea why would that be happening? 

I initialized the header this way:
const click_tcp *tcph = p->tcp_header();

Thank you so much