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   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/types.h>
  10 #include <linux/ip.h>
  11 #include <linux/netfilter.h>
  12 #include <linux/module.h>
  13 #include <linux/skbuff.h>
  14 #include <net/route.h>
  15 #include <net/ip.h>
  16
  17 #include <linux/netfilter_bridge.h>
  18 #include <linux/netfilter_ipv4.h>
  19 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  20
  21 /* Returns new sk_buff, or NULL */
  22 static int nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
  23 {
  24         int err;
  25
  26         skb_orphan(skb);
  27
  28         local_bh_disable();
  29         err = ip_defrag(skb, user);
  30         local_bh_enable();
  31
  32         if (!err)
  33                 ip_send_check(ip_hdr(skb));
  34
  35         return err;
  36 }
  37
  38 static enum ip_defrag_users nf_ct_defrag_user(unsigned int hooknum,
  39                                               struct sk_buff *skb)
  40 {
  41 #ifdef CONFIG_BRIDGE_NETFILTER
  42         if (skb->nf_bridge &&
  43             skb->nf_bridge->mask & BRNF_NF_BRIDGE_PREROUTING)
  44                 return IP_DEFRAG_CONNTRACK_BRIDGE_IN;
  45 #endif
  46         if (hooknum == NF_INET_PRE_ROUTING)
  47                 return IP_DEFRAG_CONNTRACK_IN;
  48         else
  49                 return IP_DEFRAG_CONNTRACK_OUT;
  50 }
  51
  52 static unsigned int ipv4_conntrack_defrag(unsigned int hooknum,
  53                                           struct sk_buff *skb,
  54                                           const struct net_device *in,
  55                                           const struct net_device *out,
  56                                           int (*okfn)(struct sk_buff *))
  57 {
  58 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
  59 #if !defined(CONFIG_NF_NAT) && !defined(CONFIG_NF_NAT_MODULE)
  60         /* Previously seen (loopback)?  Ignore.  Do this before
  61            fragment check. */
  62         if (skb->nfct)
  63                 return NF_ACCEPT;
  64 #endif
  65 #endif
  66         /* Gather fragments. */
  67         if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) {
  68                 enum ip_defrag_users user = nf_ct_defrag_user(hooknum, skb);
  69                 if (nf_ct_ipv4_gather_frags(skb, user))
  70                         return NF_STOLEN;
  71         }
  72         return NF_ACCEPT;
  73 }
  74
  75 static struct nf_hook_ops ipv4_defrag_ops[] = {
  76         {
  77                 .hook           = ipv4_conntrack_defrag,
  78                 .owner          = THIS_MODULE,
  79                 .pf             = PF_INET,
  80                 .hooknum        = NF_INET_PRE_ROUTING,
  81                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
  82         },
  83         {
  84                 .hook           = ipv4_conntrack_defrag,
  85                 .owner          = THIS_MODULE,
  86                 .pf             = PF_INET,
  87                 .hooknum        = NF_INET_LOCAL_OUT,
  88                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
  89         },
  90 };
  91
  92 static int __init nf_defrag_init(void)
  93 {
  94         return nf_register_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
  95 }
  96
  97 static void __exit nf_defrag_fini(void)
  98 {
  99         nf_unregister_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
 100 }
 101
 102 void nf_defrag_ipv4_enable(void)
 103 {
 104 }
 105 EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable);
 106
 107 module_init(nf_defrag_init);
 108 module_exit(nf_defrag_fini);
 109
 110 MODULE_LICENSE("GPL");