net/ipv4/netfilter/nf_defrag_ipv4.c

   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_ipv4.h>
  18 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  19
  20 /* Returns new sk_buff, or NULL */
  21 static int nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
  22 {
  23         int err;
  24
  25         skb_orphan(skb);
  26
  27         local_bh_disable();
  28         err = ip_defrag(skb, user);
  29         local_bh_enable();
  30
  31         if (!err)
  32                 ip_send_check(ip_hdr(skb));
  33
  34         return err;
  35 }
  36
  37 static unsigned int ipv4_conntrack_defrag(unsigned int hooknum,
  38                                           struct sk_buff *skb,
  39                                           const struct net_device *in,
  40                                           const struct net_device *out,
  41                                           int (*okfn)(struct sk_buff *))
  42 {
  43 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
  44         /* Previously seen (loopback)?  Ignore.  Do this before
  45            fragment check. */
  46         if (skb->nfct)
  47                 return NF_ACCEPT;
  48 #endif
  49
  50         /* Gather fragments. */
  51         if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) {
  52                 if (nf_ct_ipv4_gather_frags(skb,
  53                                             hooknum == NF_INET_PRE_ROUTING ?
  54                                             IP_DEFRAG_CONNTRACK_IN :
  55                                             IP_DEFRAG_CONNTRACK_OUT))
  56                         return NF_STOLEN;
  57         }
  58         return NF_ACCEPT;
  59 }
  60
  61 static struct nf_hook_ops ipv4_defrag_ops[] = {
  62         {
  63                 .hook           = ipv4_conntrack_defrag,
  64                 .owner          = THIS_MODULE,
  65                 .pf             = PF_INET,
  66                 .hooknum        = NF_INET_PRE_ROUTING,
  67                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
  68         },
  69         {
  70                 .hook           = ipv4_conntrack_defrag,
  71                 .owner          = THIS_MODULE,
  72                 .pf             = PF_INET,
  73                 .hooknum        = NF_INET_LOCAL_OUT,
  74                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
  75         },
  76 };
  77
  78 static int __init nf_defrag_init(void)
  79 {
  80         return nf_register_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
  81 }
  82
  83 static void __exit nf_defrag_fini(void)
  84 {
  85         nf_unregister_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
  86 }
  87
  88 void nf_defrag_ipv4_enable(void)
  89 {
  90 }
  91 EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable);
  92
  93 module_init(nf_defrag_init);
  94 module_exit(nf_defrag_fini);
  95
  96 MODULE_LICENSE("GPL");