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_id = NF_CT_DEFAULT_ZONE_ID;
  47 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  48         if (skb->nfct) {
  49                 enum ip_conntrack_info ctinfo;
  50                 const struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
  51
  52                 zone_id = nf_ct_zone_id(nf_ct_zone(ct), CTINFO2DIR(ctinfo));
  53         }
  54 #endif
  55         if (nf_bridge_in_prerouting(skb))
  56                 return IP_DEFRAG_CONNTRACK_BRIDGE_IN + zone_id;
  57
  58         if (hooknum == NF_INET_PRE_ROUTING)
  59                 return IP_DEFRAG_CONNTRACK_IN + zone_id;
  60         else
  61                 return IP_DEFRAG_CONNTRACK_OUT + zone_id;
  62 }
  63
  64 static unsigned int ipv4_conntrack_defrag(const struct nf_hook_ops *ops,
  65                                           struct sk_buff *skb,
  66                                           const struct nf_hook_state *state)
  67 {
  68         struct sock *sk = skb->sk;
  69         struct inet_sock *inet = inet_sk(skb->sk);
  70
  71         if (sk && (sk->sk_family == PF_INET) &&
  72             inet->nodefrag)
  73                 return NF_ACCEPT;
  74
  75 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  76 #if !IS_ENABLED(CONFIG_NF_NAT)
  77         /* Previously seen (loopback)?  Ignore.  Do this before
  78            fragment check. */
  79         if (skb->nfct && !nf_ct_is_template((struct nf_conn *)skb->nfct))
  80                 return NF_ACCEPT;
  81 #endif
  82 #endif
  83         /* Gather fragments. */
  84         if (ip_is_fragment(ip_hdr(skb))) {
  85                 enum ip_defrag_users user =
  86                         nf_ct_defrag_user(ops->hooknum, skb);
  87
  88                 if (nf_ct_ipv4_gather_frags(skb, user))
  89                         return NF_STOLEN;
  90         }
  91         return NF_ACCEPT;
  92 }
  93
  94 static struct nf_hook_ops ipv4_defrag_ops[] = {
  95         {
  96                 .hook           = ipv4_conntrack_defrag,
  97                 .owner          = THIS_MODULE,
  98                 .pf             = NFPROTO_IPV4,
  99                 .hooknum        = NF_INET_PRE_ROUTING,
 100                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
 101         },
 102         {
 103                 .hook           = ipv4_conntrack_defrag,
 104                 .owner          = THIS_MODULE,
 105                 .pf             = NFPROTO_IPV4,
 106                 .hooknum        = NF_INET_LOCAL_OUT,
 107                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
 108         },
 109 };
 110
 111 static int __init nf_defrag_init(void)
 112 {
 113         return nf_register_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
 114 }
 115
 116 static void __exit nf_defrag_fini(void)
 117 {
 118         nf_unregister_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
 119 }
 120
 121 void nf_defrag_ipv4_enable(void)
 122 {
 123 }
 124 EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable);
 125
 126 module_init(nf_defrag_init);
 127 module_exit(nf_defrag_fini);
 128
 129 MODULE_LICENSE("GPL");