nf_defrag_ipv4.c

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/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2004 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/types.h>
#include <linux/ip.h>
#include <linux/netfilter.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/route.h>
#include <net/ip.h>

#include <linux/netfilter_bridge.h>
#include <linux/netfilter_ipv4.h>
#include <net/netfilter/ipv4/nf_defrag_ipv4.h>
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
#include <net/netfilter/nf_conntrack.h>
#endif
#include <net/netfilter/nf_conntrack_zones.h>

/* Returns new sk_buff, or NULL */
static int nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
{
    int err;

    skb_orphan(skb);

    local_bh_disable();
    err = ip_defrag(skb, user);
    local_bh_enable();

    if (!err)
        ip_send_check(ip_hdr(skb));

    return err;
}

static enum ip_defrag_users nf_ct_defrag_user(unsigned int hooknum,
                          struct sk_buff *skb)
{
    u16 zone = NF_CT_DEFAULT_ZONE;

#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
    if (skb->nfct)
        zone = nf_ct_zone((struct nf_conn *)skb->nfct);
#endif

#ifdef CONFIG_BRIDGE_NETFILTER
    if (skb->nf_bridge &&
        skb->nf_bridge->mask & BRNF_NF_BRIDGE_PREROUTING)
        return IP_DEFRAG_CONNTRACK_BRIDGE_IN + zone;
#endif
    if (hooknum == NF_INET_PRE_ROUTING)
        return IP_DEFRAG_CONNTRACK_IN + zone;
    else
        return IP_DEFRAG_CONNTRACK_OUT + zone;
}

static unsigned int ipv4_conntrack_defrag(unsigned int hooknum,
                      struct sk_buff *skb,
                      const struct net_device *in,
                      const struct net_device *out,
                      int (*okfn)(struct sk_buff *))
{
    struct sock *sk = skb->sk;
    struct inet_sock *inet = inet_sk(skb->sk);

    if (sk && (sk->sk_family == PF_INET) &&
        inet->nodefrag)
        return NF_ACCEPT;

#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
#if !defined(CONFIG_NF_NAT) && !defined(CONFIG_NF_NAT_MODULE)
    /* Previously seen (loopback)?  Ignore.  Do this before
       fragment check. */
    if (skb->nfct && !nf_ct_is_template((struct nf_conn *)skb->nfct))
        return NF_ACCEPT;
#endif
#endif
    /* Gather fragments. */
    if (ip_is_fragment(ip_hdr(skb))) {
        enum ip_defrag_users user = nf_ct_defrag_user(hooknum, skb);
        if (nf_ct_ipv4_gather_frags(skb, user))
            return NF_STOLEN;
    }
    return NF_ACCEPT;
}

static struct nf_hook_ops ipv4_defrag_ops[] = {
    {
        .hook       = ipv4_conntrack_defrag,
        .owner      = THIS_MODULE,
        .pf     = NFPROTO_IPV4,
        .hooknum    = NF_INET_PRE_ROUTING,
        .priority   = NF_IP_PRI_CONNTRACK_DEFRAG,
    },
    {
        .hook           = ipv4_conntrack_defrag,
        .owner          = THIS_MODULE,
        .pf             = NFPROTO_IPV4,
        .hooknum        = NF_INET_LOCAL_OUT,
        .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
    },
};

static int __init nf_defrag_init(void)
{
    return nf_register_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
}

static void __exit nf_defrag_fini(void)
{
    nf_unregister_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
}

void nf_defrag_ipv4_enable(void)
{
}
EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable);

module_init(nf_defrag_init);
module_exit(nf_defrag_fini);

MODULE_LICENSE("GPL");