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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9 #include <linux/module.h>
  10 #include <linux/gfp.h>
  11 #include <linux/skbuff.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_action_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 == NFPROTO_IPV4) {
  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 == NFPROTO_IPV6) {
  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 int 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         int ret = 0;
  63         u8 proto;
  64
  65         if (info->flags & ~XT_CT_NOTRACK)
  66                 return -EINVAL;
  67
  68         if (info->flags & XT_CT_NOTRACK) {
  69                 ct = nf_ct_untracked_get();
  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         ret = nf_ct_l3proto_try_module_get(par->family);
  80         if (ret < 0)
  81                 goto err1;
  82
  83         memset(&t, 0, sizeof(t));
  84         ct = nf_conntrack_alloc(par->net, info->zone, &t, &t, GFP_KERNEL);
  85         ret = PTR_ERR(ct);
  86         if (IS_ERR(ct))
  87                 goto err2;
  88
  89         ret = 0;
  90         if ((info->ct_events || info->exp_events) &&
  91             !nf_ct_ecache_ext_add(ct, info->ct_events, info->exp_events,
  92                                   GFP_KERNEL))
  93                 goto err3;
  94
  95         if (info->helper[0]) {
  96                 ret = -ENOENT;
  97                 proto = xt_ct_find_proto(par);
  98                 if (!proto) {
  99                         pr_info("You must specify a L4 protocol, "
 100                                 "and not use inversions on it.\n");
 101                         goto err3;
 102                 }
 103
 104                 ret = -ENOMEM;
 105                 help = nf_ct_helper_ext_add(ct, GFP_KERNEL);
 106                 if (help == NULL)
 107                         goto err3;
 108
 109                 ret = -ENOENT;
 110                 help->helper = nf_conntrack_helper_try_module_get(info->helper,
 111                                                                   par->family,
 112                                                                   proto);
 113                 if (help->helper == NULL) {
 114                         pr_info("No such helper \"%s\"\n", info->helper);
 115                         goto err3;
 116                 }
 117         }
 118
 119         __set_bit(IPS_TEMPLATE_BIT, &ct->status);
 120         __set_bit(IPS_CONFIRMED_BIT, &ct->status);
 121 out:
 122         info->ct = ct;
 123         return 0;
 124
 125 err3:
 126         nf_conntrack_free(ct);
 127 err2:
 128         nf_ct_l3proto_module_put(par->family);
 129 err1:
 130         return ret;
 131 }
 132
 133 static void xt_ct_tg_destroy(const struct xt_tgdtor_param *par)
 134 {
 135         struct xt_ct_target_info *info = par->targinfo;
 136         struct nf_conn *ct = info->ct;
 137         struct nf_conn_help *help;
 138
 139         if (!nf_ct_is_untracked(ct)) {
 140                 help = nfct_help(ct);
 141                 if (help)
 142                         module_put(help->helper->me);
 143
 144                 nf_ct_l3proto_module_put(par->family);
 145         }
 146         nf_ct_put(info->ct);
 147 }
 148
 149 static struct xt_target xt_ct_tg __read_mostly = {
 150         .name           = "CT",
 151         .family         = NFPROTO_UNSPEC,
 152         .targetsize     = sizeof(struct xt_ct_target_info),
 153         .checkentry     = xt_ct_tg_check,
 154         .destroy        = xt_ct_tg_destroy,
 155         .target         = xt_ct_target,
 156         .table          = "raw",
 157         .me             = THIS_MODULE,
 158 };
 159
 160 static int __init xt_ct_tg_init(void)
 161 {
 162         return xt_register_target(&xt_ct_tg);
 163 }
 164
 165 static void __exit xt_ct_tg_exit(void)
 166 {
 167         xt_unregister_target(&xt_ct_tg);
 168 }
 169
 170 module_init(xt_ct_tg_init);
 171 module_exit(xt_ct_tg_exit);
 172
 173 MODULE_LICENSE("GPL");
 174 MODULE_DESCRIPTION("Xtables: connection tracking target");
 175 MODULE_ALIAS("ipt_CT");
 176 MODULE_ALIAS("ip6t_CT");