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