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 net *net, struct sk_buff *skb,
  26                                    u_int32_t user)
  27 {
  28         int err;
  29
  30         local_bh_disable();
  31         err = ip_defrag(net, skb, user);
  32         local_bh_enable();
  33
  34         if (!err)
  35                 skb->ignore_df = 1;
  36
  37         return err;
  38 }
  39
  40 static enum ip_defrag_users nf_ct_defrag_user(unsigned int hooknum,
  41                                               struct sk_buff *skb)
  42 {
  43         u16 zone_id = NF_CT_DEFAULT_ZONE_ID;
  44 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  45         if (skb->nfct) {
  46                 enum ip_conntrack_info ctinfo;
  47                 const struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
  48
  49                 zone_id = nf_ct_zone_id(nf_ct_zone(ct), CTINFO2DIR(ctinfo));
  50         }
  51 #endif
  52         if (nf_bridge_in_prerouting(skb))
  53                 return IP_DEFRAG_CONNTRACK_BRIDGE_IN + zone_id;
  54
  55         if (hooknum == NF_INET_PRE_ROUTING)
  56                 return IP_DEFRAG_CONNTRACK_IN + zone_id;
  57         else
  58                 return IP_DEFRAG_CONNTRACK_OUT + zone_id;
  59 }
  60
  61 static unsigned int ipv4_conntrack_defrag(void *priv,
  62                                           struct sk_buff *skb,
  63                                           const struct nf_hook_state *state)
  64 {
  65         struct sock *sk = skb->sk;
  66
  67         if (sk && sk_fullsock(sk) && (sk->sk_family == PF_INET) &&
  68             inet_sk(sk)->nodefrag)
  69                 return NF_ACCEPT;
  70
  71 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  72 #if !IS_ENABLED(CONFIG_NF_NAT)
  73         /* Previously seen (loopback)?  Ignore.  Do this before
  74            fragment check. */
  75         if (skb->nfct && !nf_ct_is_template((struct nf_conn *)skb->nfct))
  76                 return NF_ACCEPT;
  77 #endif
  78 #endif
  79         /* Gather fragments. */
  80         if (ip_is_fragment(ip_hdr(skb))) {
  81                 enum ip_defrag_users user =
  82                         nf_ct_defrag_user(state->hook, skb);
  83
  84                 if (nf_ct_ipv4_gather_frags(state->net, skb, user))
  85                         return NF_STOLEN;
  86         }
  87         return NF_ACCEPT;
  88 }
  89
  90 static struct nf_hook_ops ipv4_defrag_ops[] = {
  91         {
  92                 .hook           = ipv4_conntrack_defrag,
  93                 .pf             = NFPROTO_IPV4,
  94                 .hooknum        = NF_INET_PRE_ROUTING,
  95                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
  96         },
  97         {
  98                 .hook           = ipv4_conntrack_defrag,
  99                 .pf             = NFPROTO_IPV4,
 100                 .hooknum        = NF_INET_LOCAL_OUT,
 101                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
 102         },
 103 };
 104
 105 static int __init nf_defrag_init(void)
 106 {
 107         return nf_register_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
 108 }
 109
 110 static void __exit nf_defrag_fini(void)
 111 {
 112         nf_unregister_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
 113 }
 114
 115 void nf_defrag_ipv4_enable(void)
 116 {
 117 }
 118 EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable);
 119
 120 module_init(nf_defrag_init);
 121 module_exit(nf_defrag_fini);
 122
 123 MODULE_LICENSE("GPL");