Kernel Module - Packet Capture/Send And Packet Creation/Send

[tyman475]

Hi,

I am currently working on a kernel module that uses a netfilter hook on out-going packets from the machine.

I can currently load the module and tail /var/log/messages and view the packets which match the packets I see using wireshark.

What I am wanting to do:
1. Hook into all out-going packets. (check)
To do this I have a hook:

static struct nf_hook_ops hook_ops_out __read_mostly =
{
	.pf		= PF_INET,
	.priority	= NF_IP_PRI_FIRST,
	.hooknum	= NF_INET_POST_ROUTING,
	.hook		= hook_out,
};

which calls hook_out:

static unsigned int hook_out(unsigned int hooknum, struct sk_buff *skb, const struct net_device *in, const struct net_device *out, int (*okfn)(struct sk_buff*))
{
/* TODO: 1.1, 1.2 */
// Print packet info to make sure it is working
return NF_ACCEPT; // This will send the original out-going packet
}

1.1 Copy the payload of the these packets and place it into a newly created packet with a different dest addr.
I need an example of how to create a packet and fill it with the correct parameters.

1.2 Send both packets.
Sending the original out-going packet is easy by returning NF_ACCEPT at the end of the hook.
Sending the created packet is difficult because I cannot find a working example of how to create and send a packet from inside the kernel code. Everything I have found locks up the machine.

Any thoughts would be greatly appreciated.

Thanks,
tyman