#include "module.h"

extern int AT_ROUTING;
extern uint32_t at_state;
extern uint32_t at_mycid;
extern struct gateway_list_head *glh;
extern struct gateway_list_head *rlh;


struct nf_hook_ops input_filter;
struct nf_hook_ops output_filter;

int inet_aton(const char *cp, __u32 *addr)
{
    unsigned int val;
    int                     base,
    n;
    char            c;
    u_int           parts[4];
    u_int      *pp = parts;

    for (;;)
    {


        //Collect number up to ``.''. Values are specified as for C:
        // 0x=hex, 0=octal, other=decimal.

        val = 0;
        base = 10;
        if (*cp == '0')
        {
            if (*++cp == 'x' || *cp == 'X')
                base = 16, cp++;
            else
                base = 8;
        }
        while ((c = *cp) != '\0')
        {
            if (isascii(c) && isdigit(c))
            {
                val = (val * base) + (c - '0');
                cp++;
                continue;

            }
            if (base == 16 && isascii(c) && isxdigit(c))
            {
                val = (val << 4) +
                      (c + 10 - (islower(c) ? 'a' : 'A'));
                cp++;
                continue;
            }
            break;
        }
        if (*cp == '.')
        {


            // Internet format: a.b.c.d a.b.c       (with c treated as
            // 16-bits) a.b         (with b treated as 24 bits)

            if (pp >= parts + 3 || val > 0xff)
                return (0);
            *pp++ = val, cp++;
        }
        else
            break;
    }

    // Check for trailing characters.

    if (*cp && (!isascii(*cp) || !isspace(*cp)))
        return (0);


    // Concoct the address according to the number of parts specified.

    n = pp - parts + 1;
    switch (n)
    {

    case 1:                 // a -- 32 bits
        break;

    case 2:                 //a.b -- 8.24 bits
        if (val > 0xffffff)
            return (0);
        val |= parts[0] << 24;
        break;

    case 3:                 //a.b.c -- 8.8.16 bits
        if (val > 0xffff)
            return (0);
        val |= (parts[0] << 24) | (parts[1] << 16);
        break;

    case 4:                 // a.b.c.d -- 8.8.8.8 bits
        if (val > 0xff)
            return (0);
        val |= (parts[0] << 24) | (parts[1] << 16) | (parts[2] << 8);
        break;
    }
    if (addr)
        *addr= htonl(val);
    return (1);
}

int populate_proc_packet_stats(char *page, char **start, off_t offset, int count,
				int *eof, void *data)
{
	*eof = 1;	
	sprintf(page, "%d\n", at_state);	
	return strlen(page);
}


unsigned int output_handler(    unsigned int hooknum,struct sk_buff **skb,const struct net_device *in, const struct net_device *out, int (*okfn)(struct sk_buff *))
{
	struct gateway_list_node gln;	

	gln.gw =  (((*skb)->nh).iph)->daddr;
	
		printk("<1>o/p handler, trying, %u.%u.%u.%u \n", NIPQUAD(gln.gw));
	if(!check_entry_exists(&rlh, &gln))
	{
#ifdef AT_MESSAGES			
		printk("<1>o/p handler, Entry doesn't exist, %u.%u.%u.%u \n", NIPQUAD(gln.gw));
#endif /*AT_MESSAGES*/		
		return NF_QUEUE;/* packets that can't be routed must be dropped */
	}
	return NF_ACCEPT; /*well if they can be, they can go*/

}

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 gateway_list_node gln;	

	gln.gw =  (((*skb)->nh).iph)->daddr;
	if(!check_entry_exists(&rlh, &gln))
	{
#ifdef AT_MESSAGES			
		printk("<1>i/p handler, Entry doesn't exist, %u.%u.%u.%u \n", NIPQUAD(gln.gw));
		printk("<1>i/p handler, source doesn't exist, %u.%u.%u.%u \n", NIPQUAD( (((*skb)->nh).iph)->saddr));
#endif /*AT_MESSAGES*/		
		return NF_DROP;/* packets that can't be routed must be dropped */
	}
	return NF_ACCEPT; /*well if they can be, they can go*/
}

/* initialize  module */
int init_module(void) 
{ 
	/*
	 * Set Alpha-T routing started
	 * Allows the system call add_gateway to start funtioning
	 */
	AT_ROUTING = 1;
	at_state = -1; /* must initialize this variable */
	at_mycid = 0;

	/*initialize gateway list*/
	init_list(&glh);
	init_list(&rlh);

	/*create proc entries, so we can see what's happening*/
	proc_mkdir("at_routing", NULL);
	create_proc_read_entry("at_routing/at_gateways",
							0,
							NULL,
							populate_proc_gateways,
							NULL
							);
	create_proc_read_entry("at_routing/at_routable",
							0,
							NULL,
							populate_proc_routable,
							NULL
							);
	create_proc_read_entry("at_routing/at_state",
							0,
							NULL,
							populate_proc_state,
							NULL
							);
	create_proc_read_entry("at_routing/at_cid",
							0,
							NULL,
							populate_proc_cid,
							NULL
							);

	 /* input hook */
	input_filter.list.next = NULL;
	input_filter.list.prev = NULL;
	input_filter.hook = input_handler;
	input_filter.pf = PF_INET; // IPv4
	input_filter.hooknum = NF_IP_PRE_ROUTING;

	/* output hook */
	output_filter.list.next = NULL;
	output_filter.list.prev = NULL;
	output_filter.hook = output_handler;
	output_filter.pf = PF_INET; // IPv4
	output_filter.hooknum = NF_IP_LOCAL_OUT;

	/* register hooks to handle packets */
	nf_register_hook(&input_filter);
	nf_register_hook(&output_filter);

	return 0;
}
void cleanup_module(void) 
{ 
	/*Remove Alpha-T routing*/
	AT_ROUTING = 0;

	/*remove proc entries*/
	remove_proc_entry("at_routing/at_gateways", NULL);
	remove_proc_entry("at_routing/at_routable", NULL);
	remove_proc_entry("at_routing/at_state", NULL);
	remove_proc_entry("at_routing/at_cid", NULL);
	remove_proc_entry("at_routing", NULL);

	/*remove gateway list*/
	destroy_list(&glh);
	destroy_list(&rlh);

	nf_unregister_hook(&output_filter);
	nf_unregister_hook(&input_filter);
   	return; 
}