packet_in.c

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/*
               Kernel AODV  v2.1
National Institute of Standards and Technology
               Luke Klein-Berndt
-----------------------------------------------------
  Version 2.1 new features:
     * Much more stable!
     * Added locks around important areas
     * Multihop Internet gatewaying now works
     * Multicast hack added
     * Many bug fixes!
-----------------------------------------------------

Originally based upon MadHoc code. I am not
sure how much of it is left anymore, but MadHoc
proved to be a great starting point.

MadHoc was written by - Fredrik Lilieblad,
Oskar Mattsson, Petra Nylund, Dan Ouchterlony
and Anders Roxenhag Mail: mad-hoc@flyinglinux.net

This software is Open Source under the GNU General Public Licence.

*/

#include "packet_in.h"

/****************************************************

   packet_in
----------------------------------------------------
When netfilter intercepts a packet coming into
the system it passes it to Packet in to handle
****************************************************/

extern u_int32_t  g_broadcast_ip;
extern u_int32_t g_my_ip;
extern struct flood_id_queue_entry *multicast_id_queue;

#ifdef AODV_MULTICAST
extern struct socket * multicast_sock;
#endif

/*
********************************
*
*  check_packet
*
* Description:
*   Checks to make sure that the packet is the correct size for
*   the packet type it says it is
*
********************************
*/

/****************************************************

   check_packet
----------------------------------------------------
Checks to make sure that the packet is the correct size for
the packet type it says it is
****************************************************/
int check_packet (int numbytes, int type, void *data_in)
{

    int *data;

    struct rerr *tmp_rerr;
    data=(int *) data_in;

    switch (type)
    {
        //RREQ
    case 1:

        //If it is a normal route rreq
        if (numbytes == 24)
            return 0;
        if (numbytes<=26) //smaller than RREQ plus minimum exstension header
            return 1;
        if (data[25]==3 && data[26]==8 && numbytes==24+2+8)  //Multicast Group Leader Extension
            return 0;
        if (data[25]==4 && data[26]==2 && numbytes==24+2+2)  //Multicast Group Rebuild Extension
            return 0;
        break;

        //RREP
    case 2:

        if (numbytes == 20)  //Normal RREP
            return 0;
        if (numbytes<= 22)  //smaller than RREP plus minimum exstension header
            return 1;
        if (data[21]==5 && data[22]==6 && numbytes==20+2+6) //Multicast Group Information Exstension

            break;

        //RERR
    case 3:

        // Normal RERR
        tmp_rerr=data_in;
        if (numbytes == sizeof(struct rerr) + (sizeof(struct rerrdst) * tmp_rerr->dst_count))
        {
            return 0;
        }
        break;

    case 4:     //Normal RREP-ACK
        if (numbytes == 2)
            return 0;
        break;

    default:
        break;
    }

    return 1;
}


/****************************************************

        packet_in
----------------------------------------------------
This function handles all the packets which
come and either pass them to the correct function
if they are from another AODV program or allows
them to pass through if they are no of AODV type
****************************************************/

int packet_in(struct sk_buff *packet)
{
    struct net_device *dev;
    struct route_table_entry *tmp_route;
    struct iphdr *ip;
    u_int32_t tmp_ip;


    // Create aodv message types
    u_int8_t aodv_type;


    //The packets which come in still have their headers from the IP and UDP
    int start_point=sizeof(struct udphdr)+sizeof(struct iphdr);


    //get pointers to the important parts of the message
    ip  = packet->nh.iph;
    dev = packet->dev;


    //don't want to look at packets coming from us!
    tmp_ip=find_dev_ip(dev);


    if (tmp_ip==ip->saddr)
      {
        return NF_DROP;
      }
    
    if ((strcmp(dev->name,"lo")==0) && !USE_LO)
      {
        return NF_DROP;
      }
    
    if ((ip->daddr!=g_broadcast_ip) &&  (adhoc_subnet_test(ip->daddr)))
      {
        tmp_route=find_route_table_entry(ip->daddr);
        if ((tmp_route==NULL) || !tmp_route->route_valid)
          {
            printk( KERN_NOTICE "AODV: Undestination, %s, unable to forward...\n", inet_ntoa(ip->daddr)); 
            host_unr(ip->daddr);
          }
      }
    
    
    
    //For all AODV packets the type is the first byte.
    aodv_type = (int)packet->data[start_point];
    
    if (check_packet(packet->len-start_point,aodv_type,packet->data+start_point))
      {
        printk(KERN_NOTICE "AODV: Packet of type: %d and of size %u failed packet check!\n",aodv_type,packet->len-start_point);
        return NF_DROP;
        
      }

    tmp_route=find_route_table_entry(ip->saddr);
    
    if ((tmp_route!=NULL) && (tmp_route->route_valid))
      {
        tmp_route->lifetime=(HELLO_INTERVAL * ALLOWED_HELLO_LOSS) + getcurrtime();
      }
    
    //place packet in the event queue!
    insert_event_queue_entry(aodv_type,packet);
    
    return NF_ACCEPT;
}



/****************************************************

   input_handler
----------------------------------------------------
The actaul function which gets called by netfilter
****************************************************/
unsigned int input_handler(unsigned int hooknum, struct sk_buff **skb, const struct net_device *in, const struct net_device *out, int  (*okfn)(struct sk_buff *))
{
  struct iphdr *ip = (*skb)->nh.iph;  
  void *p = (uint32_t *) ip + ip->ihl;
  struct udphdr *hdr=p;// (struct udphdr *) (ip + ip->ihl); //p;
  
  struct ethhdr *mac = (*skb)->mac.ethernet;  //Thanks to Randy Pitz for adding this extra check...
  
    
#ifdef AODV_MULTICAST
    unsigned char *ucp;
#endif


 
    



#ifdef AODV_MULTICAST
    if ((ip!=NULL) &&  (multicast_test(ip->daddr)) && (ip->saddr!=g_my_ip))
      {
        if (check_check(ip->saddr,ntohs(ip->id)))
          {
            ucp=(unsigned char *)&(ip->saddr);
              
            // if (((ucp[3] & 0xff)<111) &&((ucp[3] & 0xff)>100))  
            //  {
        

                  if (sock_wspace(multicast_sock->sk)>40000)
                    insert_rebroadcast_queue_entry(ip->daddr,(*skb)->len,(*skb)->data,ip->ttl);
                  //  }
          }
        else
          {
            
            return NF_DROP;
          }

      }
#endif


    if ((*skb)->h.uh!=NULL)
    {
        if ((hdr->dest==htons(AODVPORT)) && (mac->h_proto==htons(ETH_P_IP)) )
        {

            return packet_in(*(skb));
        }
    }

    return NF_ACCEPT;

}

---