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