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 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  21 #include <net/netfilter/nf_conntrack.h>
  22 #endif
  23 #include <net/netfilter/nf_conntrack_zones.h>
  24
  25 static int nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
  26 {
  27         int err;
  28
  29         skb_orphan(skb);
  30
  31         local_bh_disable();
  32         err = ip_defrag(skb, user);
  33         local_bh_enable();
  34
  35         if (!err) {
  36                 ip_send_check(ip_hdr(skb));
  37                 skb->ignore_df = 1;
  38         }
  39
  40         return err;
  41 }
  42
  43 static enum ip_defrag_users nf_ct_defrag_user(unsigned int hooknum,
  44                                               struct sk_buff *skb)
  45 {
  46         u16 zone = NF_CT_DEFAULT_ZONE;
  47
  48 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  49         if (skb->nfct)
  50                 zone = nf_ct_zone((struct nf_conn *)skb->nfct);
  51 #endif
  52         if (nf_bridge_in_prerouting(skb))
  53                 return IP_DEFRAG_CONNTRACK_BRIDGE_IN + zone;
  54
  55         if (hooknum == NF_INET_PRE_ROUTING)
  56                 return IP_DEFRAG_CONNTRACK_IN + zone;
  57         else
  58                 return IP_DEFRAG_CONNTRACK_OUT + zone;
  59 }
  60
  61 static unsigned int ipv4_conntrack_defrag(const struct nf_hook_ops *ops,
  62                                           struct sk_buff *skb,
  63                                           const struct nf_hook_state *state)
  64 {
  65         struct sock *sk = skb->sk;
  66         struct inet_sock *inet = inet_sk(skb->sk);
  67
  68         if (sk && (sk->sk_family == PF_INET) &&
  69             inet->nodefrag)
  70                 return NF_ACCEPT;
  71
  72 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  73 #if !IS_ENABLED(CONFIG_NF_NAT)
  74         /* Previously seen (loopback)?  Ignore.  Do this before
  75            fragment check. */
  76         if (skb->nfct && !nf_ct_is_template((struct nf_conn *)skb->nfct))
  77                 return NF_ACCEPT;
  78 #endif
  79 #endif
  80         /* Gather fragments. */
  81         if (ip_is_fragment(ip_hdr(skb))) {
  82                 enum ip_defrag_users user =
  83                         nf_ct_defrag_user(ops->hooknum, skb);
  84
  85                 if (nf_ct_ipv4_gather_frags(skb, user))
  86                         return NF_STOLEN;
  87         }
  88         return NF_ACCEPT;
  89 }
  90
  91 static struct nf_hook_ops ipv4_defrag_ops[] = {
  92         {
  93                 .hook           = ipv4_conntrack_defrag,
  94                 .owner          = THIS_MODULE,
  95                 .pf             = NFPROTO_IPV4,
  96                 .hooknum        = NF_INET_PRE_ROUTING,
  97                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
  98         },
  99         {
 100                 .hook           = ipv4_conntrack_defrag,
 101                 .owner          = THIS_MODULE,
 102                 .pf             = NFPROTO_IPV4,
 103                 .hooknum        = NF_INET_LOCAL_OUT,
 104                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
 105         },
 106 };
 107
 108 static int __init nf_defrag_init(void)
 109 {
 110         return nf_register_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
 111 }
 112
 113 static void __exit nf_defrag_fini(void)
 114 {
 115         nf_unregister_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
 116 }
 117
 118 void nf_defrag_ipv4_enable(void)
 119 {
 120 }
 121 EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable);
 122
 123 module_init(nf_defrag_init);
 124 module_exit(nf_defrag_fini);
 125
 126 MODULE_LICENSE("GPL");