Hi,

 From ip_nat_core.c. Rusty says:
-                       /* future: put this in a l4-proto specific function,
-                        * and call this function here. */
-                       if (!ip_nat_seq_adjust(pskb, ct, ctinfo)

A hamster that claims to be Rusty's pet came to visit me, after he had 
some beers and got bored. So he decided to put ip_nat_seq_adjust in a 
l4-proto nat helper.

regards,
Pablo