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/netns/generic.h>
  15 #include <net/route.h>
  16 #include <net/ip.h>
  17
  18 #include <linux/netfilter_bridge.h>
  19 #include <linux/netfilter_ipv4.h>
  20 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
  21 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  22 #include <net/netfilter/nf_conntrack.h>
  23 #endif
  24 #include <net/netfilter/nf_conntrack_zones.h>
  25
  26 static DEFINE_MUTEX(defrag4_mutex);
  27
  28 static int nf_ct_ipv4_gather_frags(struct net *net, struct sk_buff *skb,
  29                                    u_int32_t user)
  30 {
  31         int err;
  32
  33         local_bh_disable();
  34         err = ip_defrag(net, skb, user);
  35         local_bh_enable();
  36
  37         if (!err)
  38                 skb->ignore_df = 1;
  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(skb)) {
  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(void *priv,
  65                                           struct sk_buff *skb,
  66                                           const struct nf_hook_state *state)
  67 {
  68         struct sock *sk = skb->sk;
  69
  70         if (sk && sk_fullsock(sk) && (sk->sk_family == PF_INET) &&
  71             inet_sk(sk)->nodefrag)
  72                 return NF_ACCEPT;
  73
  74 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  75 #if !IS_ENABLED(CONFIG_NF_NAT)
  76         /* Previously seen (loopback)?  Ignore.  Do this before
  77            fragment check. */
  78         if (skb_nfct(skb) && !nf_ct_is_template((struct nf_conn *)skb_nfct(skb)))
  79                 return NF_ACCEPT;
  80 #endif
  81         if (skb->_nfct == IP_CT_UNTRACKED)
  82                 return NF_ACCEPT;
  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 const struct nf_hook_ops ipv4_defrag_ops[] = {
  96         {
  97                 .hook           = ipv4_conntrack_defrag,
  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                 .pf             = NFPROTO_IPV4,
 105                 .hooknum        = NF_INET_LOCAL_OUT,
 106                 .priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
 107         },
 108 };
 109
 110 static void __net_exit defrag4_net_exit(struct net *net)
 111 {
 112         if (net->nf.defrag_ipv4) {
 113                 nf_unregister_net_hooks(net, ipv4_defrag_ops,
 114                                         ARRAY_SIZE(ipv4_defrag_ops));
 115                 net->nf.defrag_ipv4 = false;
 116         }
 117 }
 118
 119 static struct pernet_operations defrag4_net_ops = {
 120         .exit = defrag4_net_exit,
 121 };
 122
 123 static int __init nf_defrag_init(void)
 124 {
 125         return register_pernet_subsys(&defrag4_net_ops);
 126 }
 127
 128 static void __exit nf_defrag_fini(void)
 129 {
 130         unregister_pernet_subsys(&defrag4_net_ops);
 131 }
 132
 133 int nf_defrag_ipv4_enable(struct net *net)
 134 {
 135         int err = 0;
 136
 137         might_sleep();
 138
 139         if (net->nf.defrag_ipv4)
 140                 return 0;
 141
 142         mutex_lock(&defrag4_mutex);
 143         if (net->nf.defrag_ipv4)
 144                 goto out_unlock;
 145
 146         err = nf_register_net_hooks(net, ipv4_defrag_ops,
 147                                     ARRAY_SIZE(ipv4_defrag_ops));
 148         if (err == 0)
 149                 net->nf.defrag_ipv4 = true;
 150
 151  out_unlock:
 152         mutex_unlock(&defrag4_mutex);
 153         return err;
 154 }
 155 EXPORT_SYMBOL_GPL(nf_defrag_ipv4_enable);
 156
 157 module_init(nf_defrag_init);
 158 module_exit(nf_defrag_fini);
 159
 160 MODULE_LICENSE("GPL");