How to get data in kernel SEND buffer for a TCP socket from a netfilter based kernel module

HI all,

I want to know ,if there is a way to get data from the kernel SEND
buffer for a socket from a kernel module which is using netfilter
hooks ?? If yes, is there any open source implemenation /example which
i can start with ??
I believe there should be a way to parse sk_buff linked list and get
this data but not very sure being new to networking . Also how
portable this part will be ??
1: To other Linux kernel versions ??
2: To Other Unix* like kernels ??


Thanks,
Rohit