net/netfilter/xt_CT.c

   1 /*
   2  * Copyright (c) 2010 Patrick McHardy <kaber@trash.net>
   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/module.h>
  10 #include <linux/skbuff.h>
  11 #include <linux/selinux.h>
  12 #include <linux/netfilter_ipv4/ip_tables.h>
  13 #include <linux/netfilter_ipv6/ip6_tables.h>
  14 #include <linux/netfilter/x_tables.h>
  15 #include <linux/netfilter/xt_CT.h>
  16 #include <net/netfilter/nf_conntrack.h>
  17 #include <net/netfilter/nf_conntrack_helper.h>
  18 #include <net/netfilter/nf_conntrack_ecache.h>
  19 #include <net/netfilter/nf_conntrack_zones.h>
  20
  21 static unsigned int xt_ct_target(struct sk_buff *skb,
  22                                  const struct xt_target_param *par)
  23 {
  24         const struct xt_ct_target_info *info = par->targinfo;
  25         struct nf_conn *ct = info->ct;
  26
  27         /* Previously seen (loopback)? Ignore. */
  28         if (skb->nfct != NULL)
  29                 return XT_CONTINUE;
  30
  31         atomic_inc(&ct->ct_general.use);
  32         skb->nfct = &ct->ct_general;
  33         skb->nfctinfo = IP_CT_NEW;
  34
  35         return XT_CONTINUE;
  36 }
  37
  38 static u8 xt_ct_find_proto(const struct xt_tgchk_param *par)
  39 {
  40         if (par->family == AF_INET) {
  41                 const struct ipt_entry *e = par->entryinfo;
  42
  43                 if (e->ip.invflags & IPT_INV_PROTO)
  44                         return 0;
  45                 return e->ip.proto;
  46         } else if (par->family == AF_INET6) {
  47                 const struct ip6t_entry *e = par->entryinfo;
  48
  49                 if (e->ipv6.invflags & IP6T_INV_PROTO)
  50                         return 0;
  51                 return e->ipv6.proto;
  52         } else
  53                 return 0;
  54 }
  55
  56 static bool xt_ct_tg_check(const struct xt_tgchk_param *par)
  57 {
  58         struct xt_ct_target_info *info = par->targinfo;
  59         struct nf_conntrack_tuple t;
  60         struct nf_conn_help *help;
  61         struct nf_conn *ct;
  62         u8 proto;
  63
  64         if (info->flags & ~XT_CT_NOTRACK)
  65                 return false;
  66
  67         if (info->flags & XT_CT_NOTRACK) {
  68                 ct = &nf_conntrack_untracked;
  69                 atomic_inc(&ct->ct_general.use);
  70                 goto out;
  71         }
  72
  73 #ifndef CONFIG_NF_CONNTRACK_ZONES
  74         if (info->zone)
  75                 goto err1;
  76 #endif
  77
  78         if (nf_ct_l3proto_try_module_get(par->family) < 0)
  79                 goto err1;
  80
  81         memset(&t, 0, sizeof(t));
  82         ct = nf_conntrack_alloc(par->net, info->zone, &t, &t, GFP_KERNEL);
  83         if (IS_ERR(ct))
  84                 goto err2;
  85
  86         if ((info->ct_events || info->exp_events) &&
  87             !nf_ct_ecache_ext_add(ct, info->ct_events, info->exp_events,
  88                                   GFP_KERNEL))
  89                 goto err3;
  90
  91         if (info->helper[0]) {
  92                 proto = xt_ct_find_proto(par);
  93                 if (!proto)
  94                         goto err3;
  95
  96                 help = nf_ct_helper_ext_add(ct, GFP_KERNEL);
  97                 if (help == NULL)
  98                         goto err3;
  99
 100                 help->helper = nf_conntrack_helper_try_module_get(info->helper,
 101                                                                   par->family,
 102                                                                   proto);
 103                 if (help->helper == NULL)
 104                         goto err3;
 105         }
 106
 107         __set_bit(IPS_TEMPLATE_BIT, &ct->status);
 108         __set_bit(IPS_CONFIRMED_BIT, &ct->status);
 109 out:
 110         info->ct = ct;
 111         return true;
 112
 113 err3:
 114         nf_conntrack_free(ct);
 115 err2:
 116         nf_ct_l3proto_module_put(par->family);
 117 err1:
 118         return false;
 119 }
 120
 121 static void xt_ct_tg_destroy(const struct xt_tgdtor_param *par)
 122 {
 123         struct xt_ct_target_info *info = par->targinfo;
 124         struct nf_conn *ct = info->ct;
 125         struct nf_conn_help *help;
 126
 127         if (ct != &nf_conntrack_untracked) {
 128                 help = nfct_help(ct);
 129                 if (help)
 130                         module_put(help->helper->me);
 131
 132                 nf_ct_l3proto_module_put(par->family);
 133         }
 134         nf_ct_put(info->ct);
 135 }
 136
 137 static struct xt_target xt_ct_tg __read_mostly = {
 138         .name           = "CT",
 139         .family         = NFPROTO_UNSPEC,
 140         .targetsize     = XT_ALIGN(sizeof(struct xt_ct_target_info)),
 141         .checkentry     = xt_ct_tg_check,
 142         .destroy        = xt_ct_tg_destroy,
 143         .target         = xt_ct_target,
 144         .table          = "raw",
 145         .me             = THIS_MODULE,
 146 };
 147
 148 static int __init xt_ct_tg_init(void)
 149 {
 150         return xt_register_target(&xt_ct_tg);
 151 }
 152
 153 static void __exit xt_ct_tg_exit(void)
 154 {
 155         xt_unregister_target(&xt_ct_tg);
 156 }
 157
 158 module_init(xt_ct_tg_init);
 159 module_exit(xt_ct_tg_exit);
 160
 161 MODULE_LICENSE("GPL");
 162 MODULE_DESCRIPTION("Xtables: connection tracking target");
 163 MODULE_ALIAS("ipt_CT");
 164 MODULE_ALIAS("ip6t_CT");