problem about change MAC address

[Jianzhang Peng <pengjianzhang@xxxxxxxxx>]

hi，
i have three PC
A  ip = 192.168.2.249  vip = 192.168.2.99
B ip = 192.168.2.245   vip = 192.168.2.99  no arp
C ip = 192.168.2.19

A send package to 192.168.2.99 , then A get IP package from C and
change it's MAC  and  send  to B. I find A  can  get C's IP package,
but it can't send out. I get the idea from ipvs's dr mode. I guess my
problem in function my_xmit, but i don't know why. Thanks.

======================
#include <linux/init.h>
#include <linux/module.h>
#include <linux/netfilter.h>
#include <linux/socket.h>/*PF_INET*/
#include <linux/netfilter_ipv4.h>/*NF_IP_PRE_FIRST*/
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/inet.h> /*in_aton()*/
#include <net/ip.h>
#include <net/tcp.h>
#include <linux/version.h>
#include <linux/module.h>


#define MAC_FMT "%02x:%02x:%02x:%02x:%02x:%02x"
#define MAC_ARG(x)
((u8*)(x))[0],((u8*)(x))[1],((u8*)(x))[2],((u8*)(x))[3],((u8*)(x))[4],((u8*)(x))[5]

MODULE_LICENSE("GPL");
MODULE_AUTHOR("bbo");
struct nf_hook_ops nfho;
struct nf_hook_ops nfout;

static char * vip="192.168.2.99";
static char server_mac[ETH_ALEN] = {0x90,0xFB,0xA6,0x03,0x06,0x61};


static char * client_ip = "192.168.2.16";

static char *  rs_ip = "192.168.2.245";



#define MY_XMIT(pf, skb, rt)                            \
do {                                                    \
      skb_forward_csum(skb);                          \
      NF_HOOK(pf, NF_INET_LOCAL_OUT , (skb), NULL,    \
              (rt)->u.dst.dev, dst_output);           \
} while (0)

void print_mac_buf(char * buf)
{

      printk("DEST:" MAC_FMT "\n", MAC_ARG(buf));
      printk("SOURCE:" MAC_FMT "\n", MAC_ARG(buf+6));

}


void print_mac(struct ethhdr* eth)
{
      if(eth==NULL)   return;

      if(eth->h_source!=NULL) printk("SOURCE:" MAC_FMT "\n",
MAC_ARG(eth->h_source));

      if(eth->h_dest!=NULL) printk("DEST:" MAC_FMT "\n", MAC_ARG(eth->h_dest));
}


static struct rtable * my_route(int daddr_ip,int  rtos)
{
      struct rtable *rt = NULL;/* Route to the other host */
      struct flowi fl = {
              .oif = 0,
              .nl_u = {
                      .ip4_u = {
                              .daddr = daddr_ip,
                              .saddr = 0,
                              .tos = rtos, }
              },
      };

      if(ip_route_output_key(&init_net, &rt, &fl))
              return NULL;

      if(rt)
      {
              char * buf;
              struct hh_cache * hh = rt->u.dst.hh;
              if(hh)
              {
                      buf = hh->hh_data;
                      print_mac_buf(buf+2);
              }
      }

      return rt;
}



int my_xmit(struct sk_buff *skb, int daddr_ip)
{
      struct rtable *rt;                      /* Route to the other host */
      struct iphdr  *iph = ip_hdr(skb);
      int    mtu;


      rt = my_route(daddr_ip, RT_TOS(iph->tos));

      if(rt == NULL)  return 0;


         /*
       * Call ip_send_check because we are not sure it is called
       * after ip_defrag. Is copy-on-write needed?
       */
      if (unlikely((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)) {
              ip_rt_put(rt);
              return 1;
      }
      ip_send_check(ip_hdr(skb));

      /* drop old route */
      skb_dst_drop(skb);
      skb_dst_set(skb, &rt->u.dst);

      /* Another hack: avoid icmp_send in ip_fragment */
      skb->local_df = 1;

      MY_XMIT(NFPROTO_IPV4, skb, rt);

      return 1;
}


unsigned int checksum(unsigned int hooknum,
                      struct sk_buff *__skb,
                      const struct net_device *in,
                      const struct net_device *out,
                      int (*okfn)(struct sk_buff *))
{
      struct sk_buff *skb;
      struct net_device *dev;
      struct iphdr *iph;
      struct tcphdr *tcph;
      int tot_len;
      int iph_len;
      int tcph_len;
      int ret;

      skb = __skb;
      if(skb == NULL) return NF_ACCEPT;

      iph = ip_hdr(skb);
      if(iph == NULL)  return NF_ACCEPT;

      if((iph->daddr == in_aton(vip)) && (iph->saddr == in_aton(client_ip)))
      {

              if(my_xmit(skb,in_aton(rs_ip)))
              {
                      printk ("route OK\n");
                      return NF_STOLEN;
              }
              else
              {
                      printk ("route false\n");
              }
      }

      return NF_ACCEPT;
}



unsigned int output(unsigned int hooknum,
                      struct sk_buff *__skb,
                      const struct net_device *in,
                      const struct net_device *out,
                      int (*okfn)(struct sk_buff *))
{
      struct sk_buff *skb;
      struct net_device *dev;
      struct iphdr *iph;
      struct tcphdr *tcph;
      int tot_len;
      int iph_len;
      int tcph_len;
      int ret;

      skb = __skb;
      if(skb == NULL) return NF_ACCEPT;

      iph = ip_hdr(skb);
      if(iph == NULL)  return NF_ACCEPT;

      if((iph->daddr == in_aton(vip)) && (iph->saddr == in_aton(client_ip)))
      {
              printk ("In output\n");
      }

      return NF_ACCEPT;
}

static int __init filter_init(void)
{
      int ret;
      nfho.hook = checksum;
      nfho.pf = AF_INET;
//      nfho.hooknum = NF_INET_PRE_ROUTING;
      nfho.hooknum = NF_INET_LOCAL_IN;
//      nfho.hooknum = NF_IP_PRE_ROUTING;
      nfho.priority = NF_IP_PRI_FIRST;


      nfout.hook = output;
      nfout.pf = AF_INET;
      nfout.hooknum = NF_INET_POST_ROUTING;
      nfho.priority = NF_IP_PRI_FIRST;

      printk ("Hello,init forward~~~~~~~.\n");

      ret = nf_register_hook(&nfho);

      if(ret < 0)
      {
          printk("%s\n", "can't modify skb hook!");
          return ret;
      }

      return 0;
}

static void filter_fini(void)
{
      printk ("Hello,remove forward~~~~~~~.\n");
      nf_unregister_hook(&nfho);
}

module_init(filter_init);
module_exit(filter_fini);


--
Jianzhang Peng
--
To unsubscribe from this list: send the line "unsubscribe lvs-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html