Question

i have made a module which aims to send the ping packet using ioctl command from user space(application). however i am not sure whether its sending a ping packet or not because when i try to recieve a packet thru hook function there is no reply to it. i am sending the ping packet to router(192.168.1.1).following is my code its compiling and running w/o errors:

int device_ioctl(struct net_device *dev,struct ifreq *ifr, int cmd)
{

int len;

//printk("%s , %d",__func__,__LINE__);
switch(cmd)
{
case SIOCDEVPRIVATE:
                     printk("here it is : %s: %d\n",__func__,__LINE__);
                     break;

case WLAN_TRANSMIT :
                     icmp.type = ICMP_ECHO;
                     icmp.code = 0;
                     icmp.un.echo.sequence = i++;
                     icmp.un.echo.id = current->pid & 0xFFFF;
                     printk(KERN_ALERT"ID::%X\n",icmp.un.echo.id);
                     ip4.protocol = 0x01;                               //for icmp protocol
                     ip4.tos = 0x00;
                     ip4.frag_off = 0;
                     ip4.daddr = in_aton(procfs_buffer);
                     ip4.saddr = in_aton(ifr->ifr_addr.sa_data);
                     len = sizeof(data);
                     skb = dev_alloc_skb(1500);
                     skb->dev = __dev_get_by_name(&init_net,"wlan0");
                     skb_reserve(skb,NET_IP_ALIGN);  //header of 2 bytes; increments tail and data pointer
                     skb->data = skb_put(skb,sizeof(len)); // increments all pointer or adds data
                     memcpy(data,skb->data,len);
                    wdev = skb->dev;
                    skb->transport_header =skb_push(skb,sizeof(icmp));
                    memset(skb->transport_header,0,sizeof(struct icmphdr));
                    memcpy(skb->transport_header,&icmp,sizeof(struct icmphdr));

                    skb->network_header=skb_push(skb,sizeof(ip4));
                    memset(skb->network_header,0,sizeof(struct iphdr));
                    memcpy(skb->network_header,&ip4,sizeof(struct iphdr));
                   // printk("i::%d\n",i);
                  // skb->mac_header = skb_push(skb,6*sizeof(0xFF)); 
                //  memset(skb->mac_header,0xFF,6*sizeof(0xFF));  
                   dev_queue_xmit(skb);

                  // kfree(skb);
  }

  return 0;
  }

  unsigned int hook_func(unsigned int hooknum, struct sk_buff *skb1, const struct net_device *in, const struct net_device *out, int (*okfn)(struct sk_buff *))
  {
     struct sk_buff *sock_buff;
     struct iphdr *ip1;
     struct icmphdr *icmp1;
     sock_buff = skb1;
    //printk("ihere we are::%s,%d\n",__func__,__LINE__);
    ip1 = (struct iphdr *)skb_network_header(sock_buff);
  //printk(KERN_ALERT"proto:%d,addr:%X::%X\n",ip1->protocol,ip1->saddr,ip1->daddr);
   if(ip1->protocol==1)
    {
      printk(KERN_ALERT"proto:%d,addr:%X::%X\n",ip1->protocol,ip1->saddr,ip1->daddr);
      icmp1 = (struct icmphdr *)skb_transport_header(sock_buff);
      printk(KERN_ALERT"reply type: %c,,seq : %04X\n",icmp1->type,icmp1->un.echo.id);
         }
   // kfree(sock_buff);
   return NF_ACCEPT;

     }

hook function is working fine but not sure how to send a ping packet(in doubt because not getting a reply packet).

regards

karan

Answer 1

You can check if the ping is going out of your box using the following command, as root:

# tcpdump -i eth0 icmp

Replace eth0 with the real interface name of your machine, of course.
This command will dump all the ICMP traffic in that interface, so you should be able to check what is happening.