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_bridge.h>
  18 #include <linux/netfilter_ipv4.h>
  19 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  20 #include <net/netfilter/nf_conntrack.h>
  21
  22 /* Returns new sk_buff, or NULL */
  23 static int nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
  24 {
  25         int err;
  26
  27         skb_orphan(skb);
  28
  29         local_bh_disable();
  30         err = ip_defrag(skb, user);
  31         local_bh_enable();
  32
  33         if (!err)
  34                 ip_send_check(ip_hdr(skb));
  35
  36         return err;
  37 }
  38
  39 static enum ip_defrag_users nf_ct_defrag_user(unsigned int hooknum,
  40                                               struct sk_buff *skb)
  41 {
  42 #ifdef CONFIG_BRIDGE_NETFILTER
  43         if (skb->nf_bridge &&
  44             skb->nf_bridge->mask & BRNF_NF_BRIDGE_PREROUTING)
  45                 return IP_DEFRAG_CONNTRACK_BRIDGE_IN;
  46 #endif
  47         if (hooknum == NF_INET_PRE_ROUTING)
  48                 return IP_DEFRAG_CONNTRACK_IN;
  49         else
  50                 return IP_DEFRAG_CONNTRACK_OUT;
  51 }
  52
  53 static unsigned int ipv4_conntrack_defrag(unsigned int hooknum,
  54                                           struct sk_buff *skb,
  55                                           const struct net_device *in,
  56                                           const struct net_device *out,
  57                                           int (*okfn)(struct sk_buff *))
  58 {
  59 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
  60 #if !defined(CONFIG_NF_NAT) && !defined(CONFIG_NF_NAT_MODULE)
  61         /* Previously seen (loopback)?  Ignore.  Do this before
  62            fragment check. */
  63         if (skb->nfct && !nf_ct_is_template((struct nf_conn *)skb->nfct))
  64                 return NF_ACCEPT;
  65 #endif
  66 #endif
  67         /* Gather fragments. */
  68         if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) {
  69                 enum ip_defrag_users user = nf_ct_defrag_user(hooknum, skb);
  70                 if (nf_ct_ipv4_gather_frags(skb, user))
  71                         return NF_STOLEN;
  72         }
  73         return NF_ACCEPT;
  74 }
  75
  76 static struct nf_hook_ops ipv4_defrag_ops[] = {
  77         {
  78                 .hook           = ipv4_conntrack_defrag,
  79                 .owner          = THIS_MODULE,
  80                 .pf             = PF_INET,
  81                 .hooknum        = NF_INET_PRE_ROUTING,
  82                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
  83         },
  84         {
  85                 .hook           = ipv4_conntrack_defrag,
  86                 .owner          = THIS_MODULE,
  87                 .pf             = PF_INET,
  88                 .hooknum        = NF_INET_LOCAL_OUT,
  89                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
  90         },
  91 };
  92
  93 static int __init nf_defrag_init(void)
  94 {
  95         return nf_register_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
  96 }
  97
  98 static void __exit nf_defrag_fini(void)
  99 {
 100         nf_unregister_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
 101 }
 102
 103 void nf_defrag_ipv4_enable(void)
 104 {
 105 }
 106 EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable);
 107
 108 module_init(nf_defrag_init);
 109 module_exit(nf_defrag_fini);
 110
 111 MODULE_LICENSE("GPL");