IP packet logging function help

hello,
By adding iptable rule
iptable -A OUTPUT -j LOG
I am able to check log of each outgoing packets. But i want to know who
is actually calling ipt_log_target function defined in ipt_LOG.c as
static unsigned int
ipt_log_target(struct sk_buff **pskb,
unsigned int hooknum,
const struct net_device *in,
const struct net_device *out,
const void *targinfo,
void *userinfo)

I want to know which file in source code has pointer to call
ipt_log_target function? I want instance/copy of const struct
net_device *out to my function in kernel to know that eth0 or eth1 is
transmitting packet.