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/* Kernel module to match ESP parameters. */

#include <linux/module.h>

#include <linux/skbuff.h>

#include <linux/ipv6.h>

#include <linux/types.h>

#include <net/checksum.h>

#include <net/ipv6.h>

#include <linux/netfilter_ipv6/ip6_tables.h>

#include <linux/netfilter_ipv6/ip6t_esp.h>

EXPORT_NO_SYMBOLS;

MODULE_LICENSE("GPL");

MODULE_DESCRIPTION("IPv6 ESP match");

MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");

#if 0

#define DEBUGP printk

#else

#define DEBUGP(format, args...)

#endif

struct esphdr {

        __u32   spi;

};

/* Returns 1 if the spi is matched by the range, 0 otherwise */

static inline int

spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, int invert)

{

        int r=0;

        DEBUGP("esp spi_match:%c 0x%x <= 0x%x <= 0x%x",invert? '!':' ',

                min,spi,max);

        r=(spi >= min && spi <= max) ^ invert;

        DEBUGP(" result %s\n",r? "PASS\n" : "FAILED\n");

        return r;

}

static int

match(const struct sk_buff *skb,

      const struct net_device *in,

      const struct net_device *out,

      const void *matchinfo,

      int offset,

      const void *protohdr,

      u_int16_t datalen,

      int *hotdrop)

{

        struct esphdr *esp = NULL;

        const struct ip6t_esp *espinfo = matchinfo;

        unsigned int temp;

        int len;

        u8 nexthdr;

        unsigned int ptr;

        /* Make sure this isn't an evil packet */

        /*DEBUGP("ipv6_esp entered \n");*/

        /* type of the 1st exthdr */

        nexthdr = skb->nh.ipv6h->nexthdr;

        /* pointer to the 1st exthdr */

        ptr = sizeof(struct ipv6hdr);

        /* available length */

        len = skb->len - ptr;

        temp = 0;

        while (ip6t_ext_hdr(nexthdr)) {

                struct ipv6_opt_hdr *hdr;

                int hdrlen;

                DEBUGP("ipv6_esp header iteration \n");

                /* Is there enough space for the next ext header? */

                if (len < (int)sizeof(struct ipv6_opt_hdr))

                        return 0;

                /* No more exthdr -> evaluate */

                if (nexthdr == NEXTHDR_NONE) {

                        break;

                }

                /* ESP -> evaluate */

                if (nexthdr == NEXTHDR_ESP) {

                        temp |= MASK_ESP;

                        break;

                }

                hdr=(struct ipv6_opt_hdr *)skb->data+ptr;

                /* Calculate the header length */

                if (nexthdr == NEXTHDR_FRAGMENT) {

                        hdrlen = 8;

                } else if (nexthdr == NEXTHDR_AUTH)

                        hdrlen = (hdr->hdrlen+2)<<2;

                else

                        hdrlen = ipv6_optlen(hdr);

                /* set the flag */

                switch (nexthdr){

                        case NEXTHDR_HOP:

                        case NEXTHDR_ROUTING:

                        case NEXTHDR_FRAGMENT:

                        case NEXTHDR_AUTH:

                        case NEXTHDR_DEST:

                                break;

                        default:

                                DEBUGP("ipv6_esp match: unknown nextheader %u\n",nexthdr);

                                return 0;

                                break;

                }

                nexthdr = hdr->nexthdr;

                len -= hdrlen;

                ptr += hdrlen;

                if ( ptr > skb->len ) {

                        DEBUGP("ipv6_esp: new pointer too large! \n");

                        break;

                }

        }

        /* ESP header not found */

        if ( temp != MASK_ESP ) return 0;

       if (len < (int)sizeof(struct esphdr)){

               *hotdrop = 1;

                return 0;

       }

        esp = (struct esphdr *) (skb->data + ptr);

        DEBUGP("IPv6 ESP SPI %u %08X\n", ntohl(esp->spi), ntohl(esp->spi));

        return (esp != NULL)

                && spi_match(espinfo->spis[0], espinfo->spis[1],

                              ntohl(esp->spi),

                              !!(espinfo->invflags & IP6T_ESP_INV_SPI));

}

/* Called when user tries to insert an entry of this type. */

static int

checkentry(const char *tablename,

           const struct ip6t_ip6 *ip,

           void *matchinfo,

           unsigned int matchinfosize,

           unsigned int hook_mask)

{

        const struct ip6t_esp *espinfo = matchinfo;

        if (matchinfosize != IP6T_ALIGN(sizeof(struct ip6t_esp))) {

                DEBUGP("ip6t_esp: matchsize %u != %u\n",

                         matchinfosize, IP6T_ALIGN(sizeof(struct ip6t_esp)));

                return 0;

        }

        if (espinfo->invflags & ~IP6T_ESP_INV_MASK) {

                DEBUGP("ip6t_esp: unknown flags %X\n",

                         espinfo->invflags);

                return 0;

        }

        return 1;

}

static struct ip6t_match esp_match

= { { NULL, NULL }, "esp", &match, &checkentry, NULL, THIS_MODULE };

static int __init init(void)

{

        return ip6t_register_match(&esp_match);

}

static void __exit cleanup(void)

{

        ip6t_unregister_match(&esp_match);

}

module_init(init);

module_exit(cleanup);