iptable_raw.c

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/*
 * 'raw' table, which is the very first hooked in at PRE_ROUTING and LOCAL_OUT .
 *
 * Copyright (C) 2003 Jozsef Kadlecsik <[email protected]>
 */
#include <linux/module.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/slab.h>
#include <net/ip.h>

#define RAW_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT))

static const struct xt_table packet_raw = {
    .name = "raw",
    .valid_hooks =  RAW_VALID_HOOKS,
    .me = THIS_MODULE,
    .af = NFPROTO_IPV4,
    .priority = NF_IP_PRI_RAW,
};

/* The work comes in here from netfilter.c. */
static unsigned int
iptable_raw_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;

    if (hook == NF_INET_LOCAL_OUT && 
        (skb->len < sizeof(struct iphdr) ||
         ip_hdrlen(skb) < sizeof(struct iphdr)))
        /* root is playing with raw sockets. */
        return NF_ACCEPT;

    net = dev_net((in != NULL) ? in : out);
    return ipt_do_table(skb, hook, in, out, net->ipv4.iptable_raw);
}

static struct nf_hook_ops *rawtable_ops __read_mostly;

static int __net_init iptable_raw_net_init(struct net *net)
{
    struct ipt_replace *repl;

    repl = ipt_alloc_initial_table(&packet_raw);
    if (repl == NULL)
        return -ENOMEM;
    net->ipv4.iptable_raw =
        ipt_register_table(net, &packet_raw, repl);
    kfree(repl);
    return PTR_RET(net->ipv4.iptable_raw);
}

static void __net_exit iptable_raw_net_exit(struct net *net)
{
    ipt_unregister_table(net, net->ipv4.iptable_raw);
}

static struct pernet_operations iptable_raw_net_ops = {
    .init = iptable_raw_net_init,
    .exit = iptable_raw_net_exit,
};

static int __init iptable_raw_init(void)
{
    int ret;

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

    /* Register hooks */
    rawtable_ops = xt_hook_link(&packet_raw, iptable_raw_hook);
    if (IS_ERR(rawtable_ops)) {
        ret = PTR_ERR(rawtable_ops);
        unregister_pernet_subsys(&iptable_raw_net_ops);
    }

    return ret;
}

static void __exit iptable_raw_fini(void)
{
    xt_hook_unlink(&packet_raw, rawtable_ops);
    unregister_pernet_subsys(&iptable_raw_net_ops);
}

module_init(iptable_raw_init);
module_exit(iptable_raw_fini);
MODULE_LICENSE("GPL");