ip6t_ipv6header.c

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/* ipv6header match - matches IPv6 packets based
   on whether they contain certain headers */

/* Original idea: Brad Chapman
 * Rewritten by: Andras Kis-Szabo <[email protected]> */

/* (C) 2001-2002 Andras Kis-Szabo <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#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/x_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter_ipv6/ip6t_ipv6header.h>

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Xtables: IPv6 header types match");
MODULE_AUTHOR("Andras Kis-Szabo <[email protected]>");

static bool
ipv6header_mt6(const struct sk_buff *skb, struct xt_action_param *par)
{
    const struct ip6t_ipv6header_info *info = par->matchinfo;
    unsigned int temp;
    int len;
    u8 nexthdr;
    unsigned int ptr;

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

    /* type of the 1st exthdr */
    nexthdr = ipv6_hdr(skb)->nexthdr;
    /* pointer to the 1st exthdr */
    ptr = sizeof(struct ipv6hdr);
    /* available length */
    len = skb->len - ptr;
    temp = 0;

    while (ip6t_ext_hdr(nexthdr)) {
        const struct ipv6_opt_hdr *hp;
        struct ipv6_opt_hdr _hdr;
        int hdrlen;

        /* No more exthdr -> evaluate */
        if (nexthdr == NEXTHDR_NONE) {
            temp |= MASK_NONE;
            break;
        }
        /* Is there enough space for the next ext header? */
        if (len < (int)sizeof(struct ipv6_opt_hdr))
            return false;
        /* ESP -> evaluate */
        if (nexthdr == NEXTHDR_ESP) {
            temp |= MASK_ESP;
            break;
        }

        hp = skb_header_pointer(skb, ptr, sizeof(_hdr), &_hdr);
        BUG_ON(hp == NULL);

        /* Calculate the header length */
        if (nexthdr == NEXTHDR_FRAGMENT)
            hdrlen = 8;
        else if (nexthdr == NEXTHDR_AUTH)
            hdrlen = (hp->hdrlen + 2) << 2;
        else
            hdrlen = ipv6_optlen(hp);

        /* set the flag */
        switch (nexthdr) {
        case NEXTHDR_HOP:
            temp |= MASK_HOPOPTS;
            break;
        case NEXTHDR_ROUTING:
            temp |= MASK_ROUTING;
            break;
        case NEXTHDR_FRAGMENT:
            temp |= MASK_FRAGMENT;
            break;
        case NEXTHDR_AUTH:
            temp |= MASK_AH;
            break;
        case NEXTHDR_DEST:
            temp |= MASK_DSTOPTS;
            break;
        default:
            return false;
            break;
        }

        nexthdr = hp->nexthdr;
        len -= hdrlen;
        ptr += hdrlen;
        if (ptr > skb->len)
            break;
    }

    if (nexthdr != NEXTHDR_NONE && nexthdr != NEXTHDR_ESP)
        temp |= MASK_PROTO;

    if (info->modeflag)
        return !((temp ^ info->matchflags ^ info->invflags)
             & info->matchflags);
    else {
        if (info->invflags)
            return temp != info->matchflags;
        else
            return temp == info->matchflags;
    }
}

static int ipv6header_mt6_check(const struct xt_mtchk_param *par)
{
    const struct ip6t_ipv6header_info *info = par->matchinfo;

    /* invflags is 0 or 0xff in hard mode */
    if ((!info->modeflag) && info->invflags != 0x00 &&
        info->invflags != 0xFF)
        return -EINVAL;

    return 0;
}

static struct xt_match ipv6header_mt6_reg __read_mostly = {
    .name       = "ipv6header",
    .family     = NFPROTO_IPV6,
    .match      = ipv6header_mt6,
    .matchsize  = sizeof(struct ip6t_ipv6header_info),
    .checkentry = ipv6header_mt6_check,
    .destroy    = NULL,
    .me     = THIS_MODULE,
};

static int __init ipv6header_mt6_init(void)
{
    return xt_register_match(&ipv6header_mt6_reg);
}

static void __exit ipv6header_mt6_exit(void)
{
    xt_unregister_match(&ipv6header_mt6_reg);
}

module_init(ipv6header_mt6_init);
module_exit(ipv6header_mt6_exit);