packet_in.c

一种AODV实现方法

/*
               Kernel AODV  v2.0
National Institute of Standards and Technology
               Luke Klein-Berndt
-----------------------------------------------------
  Version 2.0 new features:
     * Updated to AODV draft version 11
     * Managed internet gatewaying
     * Monitor wireles signal strength
     * 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: [e-mail]

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;

/*
********************************
*
*  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 rrep *tmp_rrep;
    struct route_table_entry *tmp_route;
    struct neighbor_list_entry  *tmp_entry;
    struct iphdr *ip,*ip2;
    struct ethhdr *eth;
    u_int64_t curr_time;
    u_int32_t tmp_ip;
    char src_ip[16];
    char dst_ip[16];
    int print_it=1;

    // Create aodv message types
    u_int8_t aodv_type;
    u_int8_t ttl;

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

    curr_time=getcurrtime();


#ifdef TRACE
    printk("PACKET_IN: Entered\n");
#endif

    //get pointers to the important parts of the message
    ip  = packet->nh.iph;
    ip2 = packet->h.ipiph;
    eth = packet->mac.ethernet;
    dev = packet->dev;
    ttl = ip->ttl;

    //converts the IP address to strings
    strcpy(src_ip,inet_ntoa(ip->saddr));
    strcpy(dst_ip,inet_ntoa(ip->daddr));


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



    if (tmp_ip==ip->saddr)
    {
        print_it=0;
        goto drop;
    }



    if ((strcmp(dev->name,"lo")==0) && !USE_LO)
    {
        goto drop;
    }


    if (ip->daddr !=g_broadcast_ip)
    {
        tmp_route=find_route_table_entry(ip->daddr);
        if ((tmp_route==NULL) || !tmp_route->route_valid)
            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_offset,aodv_type,packet->data+start_point))
    {
	#ifdef MESSAGES
        printk("PACKET_IN: Packet of type: %d and of size %u failed packet check!\n",aodv_type,packet->len-start_offset);
	#endif
        goto drop;
    }

    tmp_route=find_route_table_entry(ip->saddr);

    if ((tmp_route!=NULL) && (tmp_route->route_valid))
    {

        tmp_route->lifetime=MAX(tmp_route->lifetime,(HELLO_INTERVAL * ALLOWED_HELLO_LOSS) + curr_time);

        tmp_entry=find_neighbor_list_entry(ip->saddr);
        if (tmp_entry!=NULL)
        {
            delete_timer_queue_entry_of_id(tmp_entry->ip, EVENT_NEIGHBOR);
            insert_timer_queue_entry(HELLO_INTERVAL * ALLOWED_HELLO_LOSS + curr_time + 20,NULL,0,ip->saddr,0,0,EVENT_NEIGHBOR);
            update_timer_queue();
        }

    }

    //place packet in the event queue!

    insert_event_queue_entry(ip->saddr,ip->daddr,(unsigned char *) &(eth->h_source),dev,aodv_type,packet->len-start_offset,packet->data+start_point,ttl);






drop:
#ifdef TRACE
    if(print_it)
        printk("PACKET_IN: We recieved a malformed AODV Message\n");
#endif

    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 *iph=(*skb)->nh.iph;
    struct udphdr *hdr;
    void* p;
    struct iphdr *ip;
    ip  = (*skb)->nh.iph;


#ifdef TRACE
    printk("INPUT_HANDLER: enter\n");
#endif



    if ((*skb)->h.uh!=NULL)
    {
        p= (u_int32_t *) iph + iph->ihl;
        hdr=p;

        if (hdr->dest==htons(AODVPORT))
        {

            return packet_in(*(skb));
        }
    }
    return NF_ACCEPT;

}