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/*************ltw,tony ipt_REDIRECT.c*/
/** using:insmod ipt_hook.ko remark=2 dst=192.168.0.116
default remark=1,dst=127.0.0.1
*/
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/netfilter.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/ctype.h>
#include <linux/inet.h>
#include <net/checksum.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_conntrack_ecache.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <linux/netfilter/nf_conntrack_ftp.h>
#include <linux/types.h>
#include <linux/skbuff.h> //skb_network_header(skb) CHECKSUM_UNNECESSARY
#include <linux/in.h> //IPPROTO_xxx
#include <linux/timer.h>
#include <net/xfrm.h>
#include <linux/netfilter.h>
#include <linux/netdevice.h> //netif_receive_skb netif_rx
#include <linux/if.h>
#include <linux/inetdevice.h>
#include <net/protocol.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter/x_tables.h>
#include <net/netfilter/nf_nat_rule.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("ltw");
static int remark=1;
char *dst="127.0.0.1";
module_param(remark,uint,0644);
module_param(dst,charp,0644);
MODULE_PARM_DESC(remark,"Copy the packet with the mark is remark");
static struct nf_hook_ops myhook;
unsigned int myhook_func(unsigned int hooknum,struct sk_buff *skb,const struct net_device *in,const struct net_device *out,int(*okfn)(struct sk_buff*))
{
//printk(KERN_ALERT "get hook\n");
struct iphdr *nowiph;
nowiph=(struct iphdr*)skb_network_header(skb);
__u32 mark=skb->mark;
__be32 mydst;
mydst = in_aton(dst);
//__be32 testip= in_aton("203.208.37.99");
//if(nowiph->saddr==testip&&nowiph->daddr==mydst) printk("OK\n");
if(nowiph->daddr==mydst)
{
printk("%8x-%8x\n",ntohl(nowiph->saddr),ntohl(nowiph->daddr));
//if(mydst==in_aton("127.0.0.1")) skb->pkt_type=5;
return NF_ACCEPT;
}
//printk(KERN_ALERT "mark=%d\n",mark);
if(mark==remark)
{
//printk(KERN_ALERT "OK\n");
struct sk_buff *myskb=skb_copy(skb,GFP_ATOMIC);
struct iphdr *myiph;
//myskb->pkt_type=PACKET_OTHERHOST;
myiph=(struct iphdr*)skb_network_header(myskb);
if(myiph==NULL)
{
kfree_skb(myskb);
return NF_ACCEPT;
}
myiph->daddr=mydst;
if(myiph->protocol==IPPROTO_TCP)
{
__wsum csum=0;
struct tcphdr *mytcphdr;
unsigned int tcphoff;
mytcphdr=(struct tcphdr*)(myskb->data+myiph->ihl*4);
if(mytcphdr==NULL)
{
kfree_skb(myskb);
return NF_ACCEPT;
}
nf_reset(myskb);
tcphoff=myiph->ihl*4;
ip_send_check(myiph);
mytcphdr->check=0;
csum=skb_checksum(myskb,tcphoff,myskb->len-tcphoff,0);
myskb->csum=csum;
myskb->ip_summed=CHECKSUM_NONE;
/*mytcphdr->check=csum_tcpudp_magic(myiph->saddr,myiph->daddr,myskb->len,IPPROTO_TCP,csum_partial((char *)mytcphdr,myskb->len-tcphoff,0));
mytcphdr->check+=0x1400;*/
mytcphdr->check=0;
mytcphdr->check=tcp_v4_check(myskb->len-tcphoff,myiph->saddr,myiph->daddr,csum_partial(mytcphdr,myskb->len-tcphoff,0));
//printk("%u--%u\n",ntohs(myiph->saddr),ntohs(myiph->daddr));
netif_rx(myskb);
}
else if(myiph->protocol==IPPROTO_UDP)
{
int csum=0;
struct udphdr *myudphdr;
unsigned int udphoff;
myudphdr=(struct udphdr*)(myskb->data+myiph->ihl*4);
if(myudphdr==NULL)
{
kfree_skb(myskb);
return NF_ACCEPT;
}
udphoff=myiph->ihl*4;
myskb->csum=0;
ip_send_check(myiph);
csum=skb_checksum(myskb,udphoff,myskb->len-udphoff,0);
myskb->csum=csum;
myskb->ip_summed=CHECKSUM_NONE;
myudphdr->check=0;
myudphdr->check=csum_tcpudp_magic(myiph->saddr,myiph->daddr,myskb->len-udphoff,IPPROTO_UDP,csum_partial(myudphdr,myskb->len-udphoff,0));
nf_reset(myskb);
netif_rx(myskb);
}
}
return NF_ACCEPT;
}
static int __init myhook_init(void)
{
printk(KERN_ALERT "ipt_hook init\n");
memset(&myhook,0,sizeof(struct nf_hook_ops));
myhook.hook=myhook_func;
myhook.owner=THIS_MODULE;
myhook.pf=PF_INET;
myhook.hooknum=NF_IP_PRE_ROUTING;
myhook.priority=INT_MAX;
return nf_register_hook(&myhook);
}
static void __exit myhook_exit(void)
{
nf_unregister_hook(&myhook);
}
module_init(myhook_init);
module_exit(myhook_exit);
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