ip6t_rt.c

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/* Kernel module to match ROUTING parameters. */

/* (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.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#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 <asm/byteorder.h>

#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter_ipv6/ip6t_rt.h>

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

/* Returns 1 if the id is matched by the range, 0 otherwise */
static inline bool
segsleft_match(u_int32_t min, u_int32_t max, u_int32_t id, bool invert)
{
    bool r;
    pr_debug("segsleft_match:%c 0x%x <= 0x%x <= 0x%x\n",
         invert ? '!' : ' ', min, id, max);
    r = (id >= min && id <= max) ^ invert;
    pr_debug(" result %s\n", r ? "PASS" : "FAILED");
    return r;
}

static bool rt_mt6(const struct sk_buff *skb, struct xt_action_param *par)
{
    struct ipv6_rt_hdr _route;
    const struct ipv6_rt_hdr *rh;
    const struct ip6t_rt *rtinfo = par->matchinfo;
    unsigned int temp;
    unsigned int ptr = 0;
    unsigned int hdrlen = 0;
    bool ret = false;
    struct in6_addr _addr;
    const struct in6_addr *ap;
    int err;

    err = ipv6_find_hdr(skb, &ptr, NEXTHDR_ROUTING, NULL, NULL);
    if (err < 0) {
        if (err != -ENOENT)
            par->hotdrop = true;
        return false;
    }

    rh = skb_header_pointer(skb, ptr, sizeof(_route), &_route);
    if (rh == NULL) {
        par->hotdrop = true;
        return false;
    }

    hdrlen = ipv6_optlen(rh);
    if (skb->len - ptr < hdrlen) {
        /* Pcket smaller than its length field */
        return false;
    }

    pr_debug("IPv6 RT LEN %u %u ", hdrlen, rh->hdrlen);
    pr_debug("TYPE %04X ", rh->type);
    pr_debug("SGS_LEFT %u %02X\n", rh->segments_left, rh->segments_left);

    pr_debug("IPv6 RT segsleft %02X ",
         segsleft_match(rtinfo->segsleft[0], rtinfo->segsleft[1],
                rh->segments_left,
                !!(rtinfo->invflags & IP6T_RT_INV_SGS)));
    pr_debug("type %02X %02X %02X ",
         rtinfo->rt_type, rh->type,
         (!(rtinfo->flags & IP6T_RT_TYP) ||
          ((rtinfo->rt_type == rh->type) ^
           !!(rtinfo->invflags & IP6T_RT_INV_TYP))));
    pr_debug("len %02X %04X %02X ",
         rtinfo->hdrlen, hdrlen,
         !(rtinfo->flags & IP6T_RT_LEN) ||
          ((rtinfo->hdrlen == hdrlen) ^
           !!(rtinfo->invflags & IP6T_RT_INV_LEN)));
    pr_debug("res %02X %02X %02X ",
         rtinfo->flags & IP6T_RT_RES,
         ((const struct rt0_hdr *)rh)->reserved,
         !((rtinfo->flags & IP6T_RT_RES) &&
           (((const struct rt0_hdr *)rh)->reserved)));

    ret = (rh != NULL) &&
          (segsleft_match(rtinfo->segsleft[0], rtinfo->segsleft[1],
                  rh->segments_left,
                  !!(rtinfo->invflags & IP6T_RT_INV_SGS))) &&
          (!(rtinfo->flags & IP6T_RT_LEN) ||
           ((rtinfo->hdrlen == hdrlen) ^
        !!(rtinfo->invflags & IP6T_RT_INV_LEN))) &&
          (!(rtinfo->flags & IP6T_RT_TYP) ||
           ((rtinfo->rt_type == rh->type) ^
        !!(rtinfo->invflags & IP6T_RT_INV_TYP)));

    if (ret && (rtinfo->flags & IP6T_RT_RES)) {
        const u_int32_t *rp;
        u_int32_t _reserved;
        rp = skb_header_pointer(skb,
                    ptr + offsetof(struct rt0_hdr,
                               reserved),
                    sizeof(_reserved),
                    &_reserved);

        ret = (*rp == 0);
    }

    pr_debug("#%d ", rtinfo->addrnr);
    if (!(rtinfo->flags & IP6T_RT_FST)) {
        return ret;
    } else if (rtinfo->flags & IP6T_RT_FST_NSTRICT) {
        pr_debug("Not strict ");
        if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
            pr_debug("There isn't enough space\n");
            return false;
        } else {
            unsigned int i = 0;

            pr_debug("#%d ", rtinfo->addrnr);
            for (temp = 0;
                 temp < (unsigned int)((hdrlen - 8) / 16);
                 temp++) {
                ap = skb_header_pointer(skb,
                            ptr
                            + sizeof(struct rt0_hdr)
                            + temp * sizeof(_addr),
                            sizeof(_addr),
                            &_addr);

                BUG_ON(ap == NULL);

                if (ipv6_addr_equal(ap, &rtinfo->addrs[i])) {
                    pr_debug("i=%d temp=%d;\n", i, temp);
                    i++;
                }
                if (i == rtinfo->addrnr)
                    break;
            }
            pr_debug("i=%d #%d\n", i, rtinfo->addrnr);
            if (i == rtinfo->addrnr)
                return ret;
            else
                return false;
        }
    } else {
        pr_debug("Strict ");
        if (rtinfo->addrnr > (unsigned int)((hdrlen - 8) / 16)) {
            pr_debug("There isn't enough space\n");
            return false;
        } else {
            pr_debug("#%d ", rtinfo->addrnr);
            for (temp = 0; temp < rtinfo->addrnr; temp++) {
                ap = skb_header_pointer(skb,
                            ptr
                            + sizeof(struct rt0_hdr)
                            + temp * sizeof(_addr),
                            sizeof(_addr),
                            &_addr);
                BUG_ON(ap == NULL);

                if (!ipv6_addr_equal(ap, &rtinfo->addrs[temp]))
                    break;
            }
            pr_debug("temp=%d #%d\n", temp, rtinfo->addrnr);
            if (temp == rtinfo->addrnr &&
                temp == (unsigned int)((hdrlen - 8) / 16))
                return ret;
            else
                return false;
        }
    }

    return false;
}

static int rt_mt6_check(const struct xt_mtchk_param *par)
{
    const struct ip6t_rt *rtinfo = par->matchinfo;

    if (rtinfo->invflags & ~IP6T_RT_INV_MASK) {
        pr_debug("unknown flags %X\n", rtinfo->invflags);
        return -EINVAL;
    }
    if ((rtinfo->flags & (IP6T_RT_RES | IP6T_RT_FST_MASK)) &&
        (!(rtinfo->flags & IP6T_RT_TYP) ||
         (rtinfo->rt_type != 0) ||
         (rtinfo->invflags & IP6T_RT_INV_TYP))) {
        pr_debug("`--rt-type 0' required before `--rt-0-*'");
        return -EINVAL;
    }

    return 0;
}

static struct xt_match rt_mt6_reg __read_mostly = {
    .name       = "rt",
    .family     = NFPROTO_IPV6,
    .match      = rt_mt6,
    .matchsize  = sizeof(struct ip6t_rt),
    .checkentry = rt_mt6_check,
    .me     = THIS_MODULE,
};

static int __init rt_mt6_init(void)
{
    return xt_register_match(&rt_mt6_reg);
}

static void __exit rt_mt6_exit(void)
{
    xt_unregister_match(&rt_mt6_reg);
}

module_init(rt_mt6_init);
module_exit(rt_mt6_exit);