local_in_hook.c

linux netfilterNF_IP_LOCAL_IN处将发给本机的包用netlink重定向到用户空间

#define __KERNEL__
#define MODULE

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/ip.h>                  /* For IP header */
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/if_packet.h>
#include <linux/netdevice.h>
#include <linux/netlink.h>
#include <net/sock.h>
#define NETLINK_RECV_1 30



typedef struct TagRedirectData{
    unsigned long dwPortID;
    unsigned long dwRedirectDataLength;
    unsigned char pvRedirectData[1024];
}TRedirectData;

u32 pidl;
static struct nf_hook_ops nfho;

MODULE_LICENSE("GPL");

struct sock *nl_skl = NULL;
void nl_data_ready (struct sock *sk, int len)
{  
wake_up_interruptible(sk->sleep);
}


static int send_to_user(TRedirectData *ptTempRedirData, int DataLength)
{
	int size, i;
	unsigned char  buff[1029]; 
	unsigned char *old_tail;  
	struct sk_buff *skb;  
	struct nlmsghdr *nlh;  
	size = NLMSG_SPACE(DataLength);
	skb = alloc_skb(size, GFP_ATOMIC);  
	old_tail = skb->tail;
	nlh = NLMSG_PUT(skb, 0, 0, 0, size-sizeof(*nlh));
	
	memcpy(NLMSG_DATA(nlh), ptTempRedirData, DataLength);
	memcpy(buff, NLMSG_DATA(nlh), DataLength); 
	printk(" dwRedirectDataLength: %lu\n",  ptTempRedirData->dwRedirectDataLength);
	nlh->nlmsg_len = skb->tail - old_tail;
	printk( "nlh->nlmsg_len: %u\n", nlh->nlmsg_len);
	for(i=0;i<DataLength;i++)
                {
                      if(i%16 == 0)
                              printk( "\n");
                      printk( "%02x ", buff[i]);
                }

	NETLINK_CB(skb).groups = 0; /* not in mcast group */ 
	NETLINK_CB(skb).pid = 0;      /* from kernel */ 
	NETLINK_CB(skb).dst_pid = pidl; 
	NETLINK_CB(skb).dst_groups = 0;  /* unicast */ 
	return netlink_unicast(nl_skl, skb, pidl, MSG_DONTWAIT);
	nlmsg_failure:
	if(skb)   
	 kfree_skb(skb);  
	return -1;
}

unsigned int hook_localhost(unsigned int hooknum, struct sk_buff **skb, const struct net_device *in, const struct net_device *out, int (*okfn)(struct sk_buff *))
{	
	struct iphdr *iph;
	TRedirectData tTempRedirData;
	int RedirectDataLength;
	struct sk_buff *sb = *skb;
	int i;
	iph = ( struct iphdr * )sb->data;
    printk( "\nPacket info from");
    printk( " %s\n", in->name);
    printk("sb->pkt_type:%d\n", sb->pkt_type);
	if(in->name[0] == 'l')
		return NF_DROP;
	else if((iph->saddr) == 0x010aa8c0)
		return NF_ACCEPT;
	else
	{	
		for(i=0;i<sb->len;i++)
		{
			if(i%16 == 0)
				printk( "\n");
			printk( "%02x ", *(sb->data+i));
		}
		tTempRedirData.dwPortID = in->name[3]-48;
		tTempRedirData.dwRedirectDataLength = sb->len;
		memset(tTempRedirData.pvRedirectData, 0, sizeof(tTempRedirData.pvRedirectData));
		memcpy(tTempRedirData.pvRedirectData, sb->data, sb->len);
		RedirectDataLength = tTempRedirData.dwRedirectDataLength + 2*sizeof(unsigned long);
		printk(" dwRedirectDataLength: %lu\n",  tTempRedirData.dwRedirectDataLength);
		printk(" RedirectDataLength: %d\n", RedirectDataLength);
		send_to_user(&tTempRedirData, RedirectDataLength); 
		return NF_DROP;
	}
		
}
int init_module()
{
	nfho.hook = hook_localhost;
	nfho.hooknum  = NF_IP_LOCAL_IN;
	nfho.pf = PF_INET;
    nfho.priority = NF_IP_PRI_FIRST;
	struct sk_buff *skb = NULL;
	struct nlmsghdr *nlh = NULL;
	int err;       
	nl_skl = netlink_kernel_create(NETLINK_RECV_1, nl_data_ready); /* wait for message coming down from user-space */ 
	skb = skb_recv_datagram(nl_skl, 0, 0, &err); 
	nlh = (struct nlmsghdr *)skb->data; 
	pidl = nlh->nlmsg_pid; /*pidl of sending process */
	return nf_register_hook(&nfho); 
}
void cleanup_module()
{
    sock_release(nl_skl->socket); 
    nf_unregister_hook(&nfho);
}