xt_NETMAP.c

Go to the documentation of this file.

/*
 * (C) 2000-2001 Svenning Soerensen <[email protected]>
 * Copyright (c) 2011 Patrick McHardy <[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/ip.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/ipv6.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv6.h>
#include <linux/netfilter/x_tables.h>
#include <net/netfilter/nf_nat.h>

static unsigned int
netmap_tg6(struct sk_buff *skb, const struct xt_action_param *par)
{
    const struct nf_nat_range *range = par->targinfo;
    struct nf_nat_range newrange;
    struct nf_conn *ct;
    enum ip_conntrack_info ctinfo;
    union nf_inet_addr new_addr, netmask;
    unsigned int i;

    ct = nf_ct_get(skb, &ctinfo);
    for (i = 0; i < ARRAY_SIZE(range->min_addr.ip6); i++)
        netmask.ip6[i] = ~(range->min_addr.ip6[i] ^
                   range->max_addr.ip6[i]);

    if (par->hooknum == NF_INET_PRE_ROUTING ||
        par->hooknum == NF_INET_LOCAL_OUT)
        new_addr.in6 = ipv6_hdr(skb)->daddr;
    else
        new_addr.in6 = ipv6_hdr(skb)->saddr;

    for (i = 0; i < ARRAY_SIZE(new_addr.ip6); i++) {
        new_addr.ip6[i] &= ~netmask.ip6[i];
        new_addr.ip6[i] |= range->min_addr.ip6[i] &
                   netmask.ip6[i];
    }

    newrange.flags  = range->flags | NF_NAT_RANGE_MAP_IPS;
    newrange.min_addr   = new_addr;
    newrange.max_addr   = new_addr;
    newrange.min_proto  = range->min_proto;
    newrange.max_proto  = range->max_proto;

    return nf_nat_setup_info(ct, &newrange, HOOK2MANIP(par->hooknum));
}

static int netmap_tg6_checkentry(const struct xt_tgchk_param *par)
{
    const struct nf_nat_range *range = par->targinfo;

    if (!(range->flags & NF_NAT_RANGE_MAP_IPS))
        return -EINVAL;
    return 0;
}

static unsigned int
netmap_tg4(struct sk_buff *skb, const struct xt_action_param *par)
{
    struct nf_conn *ct;
    enum ip_conntrack_info ctinfo;
    __be32 new_ip, netmask;
    const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
    struct nf_nat_range newrange;

    NF_CT_ASSERT(par->hooknum == NF_INET_PRE_ROUTING ||
             par->hooknum == NF_INET_POST_ROUTING ||
             par->hooknum == NF_INET_LOCAL_OUT ||
             par->hooknum == NF_INET_LOCAL_IN);
    ct = nf_ct_get(skb, &ctinfo);

    netmask = ~(mr->range[0].min_ip ^ mr->range[0].max_ip);

    if (par->hooknum == NF_INET_PRE_ROUTING ||
        par->hooknum == NF_INET_LOCAL_OUT)
        new_ip = ip_hdr(skb)->daddr & ~netmask;
    else
        new_ip = ip_hdr(skb)->saddr & ~netmask;
    new_ip |= mr->range[0].min_ip & netmask;

    memset(&newrange.min_addr, 0, sizeof(newrange.min_addr));
    memset(&newrange.max_addr, 0, sizeof(newrange.max_addr));
    newrange.flags       = mr->range[0].flags | NF_NAT_RANGE_MAP_IPS;
    newrange.min_addr.ip = new_ip;
    newrange.max_addr.ip = new_ip;
    newrange.min_proto   = mr->range[0].min;
    newrange.max_proto   = mr->range[0].max;

    /* Hand modified range to generic setup. */
    return nf_nat_setup_info(ct, &newrange, HOOK2MANIP(par->hooknum));
}

static int netmap_tg4_check(const struct xt_tgchk_param *par)
{
    const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;

    if (!(mr->range[0].flags & NF_NAT_RANGE_MAP_IPS)) {
        pr_debug("bad MAP_IPS.\n");
        return -EINVAL;
    }
    if (mr->rangesize != 1) {
        pr_debug("bad rangesize %u.\n", mr->rangesize);
        return -EINVAL;
    }
    return 0;
}

static struct xt_target netmap_tg_reg[] __read_mostly = {
    {
        .name       = "NETMAP",
        .family     = NFPROTO_IPV6,
        .revision   = 0,
        .target     = netmap_tg6,
        .targetsize = sizeof(struct nf_nat_range),
        .table      = "nat",
        .hooks      = (1 << NF_INET_PRE_ROUTING) |
                      (1 << NF_INET_POST_ROUTING) |
                      (1 << NF_INET_LOCAL_OUT) |
                      (1 << NF_INET_LOCAL_IN),
        .checkentry = netmap_tg6_checkentry,
        .me         = THIS_MODULE,
    },
    {
        .name       = "NETMAP",
        .family     = NFPROTO_IPV4,
        .revision   = 0,
        .target     = netmap_tg4,
        .targetsize = sizeof(struct nf_nat_ipv4_multi_range_compat),
        .table      = "nat",
        .hooks      = (1 << NF_INET_PRE_ROUTING) |
                      (1 << NF_INET_POST_ROUTING) |
                      (1 << NF_INET_LOCAL_OUT) |
                      (1 << NF_INET_LOCAL_IN),
        .checkentry = netmap_tg4_check,
        .me         = THIS_MODULE,
    },
};

static int __init netmap_tg_init(void)
{
    return xt_register_targets(netmap_tg_reg, ARRAY_SIZE(netmap_tg_reg));
}

static void netmap_tg_exit(void)
{
    xt_unregister_targets(netmap_tg_reg, ARRAY_SIZE(netmap_tg_reg));
}

module_init(netmap_tg_init);
module_exit(netmap_tg_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Xtables: 1:1 NAT mapping of subnets");
MODULE_AUTHOR("Patrick McHardy <[email protected]>");
MODULE_ALIAS("ip6t_NETMAP");
MODULE_ALIAS("ipt_NETMAP");