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         skb_orphan(skb);
  31
  32         local_bh_disable();
  33         err = ip_defrag(net, skb, user);
  34         local_bh_enable();
  35
  36         if (!err) {
  37                 ip_send_check(ip_hdr(skb));
  38                 skb->ignore_df = 1;
  39         }
  40
  41         return err;
  42 }
  43
  44 static enum ip_defrag_users nf_ct_defrag_user(unsigned int hooknum,
  45                                               struct sk_buff *skb)
  46 {
  47         u16 zone_id = NF_CT_DEFAULT_ZONE_ID;
  48 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  49         if (skb->nfct) {
  50                 enum ip_conntrack_info ctinfo;
  51                 const struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
  52
  53                 zone_id = nf_ct_zone_id(nf_ct_zone(ct), CTINFO2DIR(ctinfo));
  54         }
  55 #endif
  56         if (nf_bridge_in_prerouting(skb))
  57                 return IP_DEFRAG_CONNTRACK_BRIDGE_IN + zone_id;
  58
  59         if (hooknum == NF_INET_PRE_ROUTING)
  60                 return IP_DEFRAG_CONNTRACK_IN + zone_id;
  61         else
  62                 return IP_DEFRAG_CONNTRACK_OUT + zone_id;
  63 }
  64
  65 static unsigned int ipv4_conntrack_defrag(void *priv,
  66                                           struct sk_buff *skb,
  67                                           const struct nf_hook_state *state)
  68 {
  69         struct sock *sk = skb->sk;
  70         struct inet_sock *inet = inet_sk(skb->sk);
  71
  72         if (sk && (sk->sk_family == PF_INET) &&
  73             inet->nodefrag)
  74                 return NF_ACCEPT;
  75
  76 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  77 #if !IS_ENABLED(CONFIG_NF_NAT)
  78         /* Previously seen (loopback)?  Ignore.  Do this before
  79            fragment check. */
  80         if (skb->nfct && !nf_ct_is_template((struct nf_conn *)skb->nfct))
  81                 return NF_ACCEPT;
  82 #endif
  83 #endif
  84         /* Gather fragments. */
  85         if (ip_is_fragment(ip_hdr(skb))) {
  86                 enum ip_defrag_users user =
  87                         nf_ct_defrag_user(state->hook, skb);
  88
  89                 if (nf_ct_ipv4_gather_frags(state->net, skb, user))
  90                         return NF_STOLEN;
  91         }
  92         return NF_ACCEPT;
  93 }
  94
  95 static struct nf_hook_ops ipv4_defrag_ops[] = {
  96         {
  97                 .hook           = ipv4_conntrack_defrag,
  98                 .owner          = THIS_MODULE,
  99                 .pf             = NFPROTO_IPV4,
 100                 .hooknum        = NF_INET_PRE_ROUTING,
 101                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
 102         },
 103         {
 104                 .hook           = ipv4_conntrack_defrag,
 105                 .owner          = THIS_MODULE,
 106                 .pf             = NFPROTO_IPV4,
 107                 .hooknum        = NF_INET_LOCAL_OUT,
 108                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
 109         },
 110 };
 111
 112 static int __init nf_defrag_init(void)
 113 {
 114         return nf_register_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
 115 }
 116
 117 static void __exit nf_defrag_fini(void)
 118 {
 119         nf_unregister_hooks(ipv4_defrag_ops, ARRAY_SIZE(ipv4_defrag_ops));
 120 }
 121
 122 void nf_defrag_ipv4_enable(void)
 123 {
 124 }
 125 EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable);
 126
 127 module_init(nf_defrag_init);
 128 module_exit(nf_defrag_fini);
 129
 130 MODULE_LICENSE("GPL");