ip6table_mangle.c

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/*
 * IPv6 packet mangling table, a port of the IPv4 mangle table to IPv6
 *
 * Copyright (C) 2000-2001 by Harald Welte <[email protected]>
 * Copyright (C) 2000-2004 Netfilter Core Team <[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/netfilter_ipv6/ip6_tables.h>
#include <linux/slab.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <[email protected]>");
MODULE_DESCRIPTION("ip6tables mangle table");

#define MANGLE_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
                (1 << NF_INET_LOCAL_IN) | \
                (1 << NF_INET_FORWARD) | \
                (1 << NF_INET_LOCAL_OUT) | \
                (1 << NF_INET_POST_ROUTING))

static const struct xt_table packet_mangler = {
    .name       = "mangle",
    .valid_hooks    = MANGLE_VALID_HOOKS,
    .me     = THIS_MODULE,
    .af     = NFPROTO_IPV6,
    .priority   = NF_IP6_PRI_MANGLE,
};

static unsigned int
ip6t_mangle_out(struct sk_buff *skb, const struct net_device *out)
{
    unsigned int ret;
    struct in6_addr saddr, daddr;
    u_int8_t hop_limit;
    u_int32_t flowlabel, mark;

#if 0
    /* root is playing with raw sockets. */
    if (skb->len < sizeof(struct iphdr) ||
        ip_hdrlen(skb) < sizeof(struct iphdr)) {
        net_warn_ratelimited("ip6t_hook: happy cracking\n");
        return NF_ACCEPT;
    }
#endif

    /* save source/dest address, mark, hoplimit, flowlabel, priority,  */
    memcpy(&saddr, &ipv6_hdr(skb)->saddr, sizeof(saddr));
    memcpy(&daddr, &ipv6_hdr(skb)->daddr, sizeof(daddr));
    mark = skb->mark;
    hop_limit = ipv6_hdr(skb)->hop_limit;

    /* flowlabel and prio (includes version, which shouldn't change either */
    flowlabel = *((u_int32_t *)ipv6_hdr(skb));

    ret = ip6t_do_table(skb, NF_INET_LOCAL_OUT, NULL, out,
                dev_net(out)->ipv6.ip6table_mangle);

    if (ret != NF_DROP && ret != NF_STOLEN &&
        (memcmp(&ipv6_hdr(skb)->saddr, &saddr, sizeof(saddr)) ||
         memcmp(&ipv6_hdr(skb)->daddr, &daddr, sizeof(daddr)) ||
         skb->mark != mark ||
         ipv6_hdr(skb)->hop_limit != hop_limit ||
         flowlabel != *((u_int32_t *)ipv6_hdr(skb))))
        return ip6_route_me_harder(skb) == 0 ? ret : NF_DROP;

    return ret;
}

/* The work comes in here from netfilter.c. */
static unsigned int
ip6table_mangle_hook(unsigned int hook, struct sk_buff *skb,
             const struct net_device *in, const struct net_device *out,
             int (*okfn)(struct sk_buff *))
{
    if (hook == NF_INET_LOCAL_OUT)
        return ip6t_mangle_out(skb, out);
    if (hook == NF_INET_POST_ROUTING)
        return ip6t_do_table(skb, hook, in, out,
                     dev_net(out)->ipv6.ip6table_mangle);
    /* INPUT/FORWARD */
    return ip6t_do_table(skb, hook, in, out,
                 dev_net(in)->ipv6.ip6table_mangle);
}

static struct nf_hook_ops *mangle_ops __read_mostly;
static int __net_init ip6table_mangle_net_init(struct net *net)
{
    struct ip6t_replace *repl;

    repl = ip6t_alloc_initial_table(&packet_mangler);
    if (repl == NULL)
        return -ENOMEM;
    net->ipv6.ip6table_mangle =
        ip6t_register_table(net, &packet_mangler, repl);
    kfree(repl);
    return PTR_RET(net->ipv6.ip6table_mangle);
}

static void __net_exit ip6table_mangle_net_exit(struct net *net)
{
    ip6t_unregister_table(net, net->ipv6.ip6table_mangle);
}

static struct pernet_operations ip6table_mangle_net_ops = {
    .init = ip6table_mangle_net_init,
    .exit = ip6table_mangle_net_exit,
};

static int __init ip6table_mangle_init(void)
{
    int ret;

    ret = register_pernet_subsys(&ip6table_mangle_net_ops);
    if (ret < 0)
        return ret;

    /* Register hooks */
    mangle_ops = xt_hook_link(&packet_mangler, ip6table_mangle_hook);
    if (IS_ERR(mangle_ops)) {
        ret = PTR_ERR(mangle_ops);
        goto cleanup_table;
    }

    return ret;

 cleanup_table:
    unregister_pernet_subsys(&ip6table_mangle_net_ops);
    return ret;
}

static void __exit ip6table_mangle_fini(void)
{
    xt_hook_unlink(&packet_mangler, mangle_ops);
    unregister_pernet_subsys(&ip6table_mangle_net_ops);
}

module_init(ip6table_mangle_init);
module_exit(ip6table_mangle_fini);