arptable_filter.c

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/*
 * Filtering ARP tables module.
 *
 * Copyright (C) 2002 David S. Miller ([email protected])
 *
 */

#include <linux/module.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_arp/arp_tables.h>
#include <linux/slab.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("David S. Miller <[email protected]>");
MODULE_DESCRIPTION("arptables filter table");

#define FILTER_VALID_HOOKS ((1 << NF_ARP_IN) | (1 << NF_ARP_OUT) | \
               (1 << NF_ARP_FORWARD))

static const struct xt_table packet_filter = {
    .name       = "filter",
    .valid_hooks    = FILTER_VALID_HOOKS,
    .me     = THIS_MODULE,
    .af     = NFPROTO_ARP,
    .priority   = NF_IP_PRI_FILTER,
};

/* The work comes in here from netfilter.c */
static unsigned int
arptable_filter_hook(unsigned int hook, struct sk_buff *skb,
             const struct net_device *in, const struct net_device *out,
             int (*okfn)(struct sk_buff *))
{
    const struct net *net = dev_net((in != NULL) ? in : out);

    return arpt_do_table(skb, hook, in, out, net->ipv4.arptable_filter);
}

static struct nf_hook_ops *arpfilter_ops __read_mostly;

static int __net_init arptable_filter_net_init(struct net *net)
{
    struct arpt_replace *repl;
    
    repl = arpt_alloc_initial_table(&packet_filter);
    if (repl == NULL)
        return -ENOMEM;
    net->ipv4.arptable_filter =
        arpt_register_table(net, &packet_filter, repl);
    kfree(repl);
    if (IS_ERR(net->ipv4.arptable_filter))
        return PTR_ERR(net->ipv4.arptable_filter);
    return 0;
}

static void __net_exit arptable_filter_net_exit(struct net *net)
{
    arpt_unregister_table(net->ipv4.arptable_filter);
}

static struct pernet_operations arptable_filter_net_ops = {
    .init = arptable_filter_net_init,
    .exit = arptable_filter_net_exit,
};

static int __init arptable_filter_init(void)
{
    int ret;

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

    arpfilter_ops = xt_hook_link(&packet_filter, arptable_filter_hook);
    if (IS_ERR(arpfilter_ops)) {
        ret = PTR_ERR(arpfilter_ops);
        goto cleanup_table;
    }
    return ret;

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

static void __exit arptable_filter_fini(void)
{
    xt_hook_unlink(&packet_filter, arpfilter_ops);
    unregister_pernet_subsys(&arptable_filter_net_ops);
}

module_init(arptable_filter_init);
module_exit(arptable_filter_fini);