net/netfilter/xt_conntrack.c

   1 /*
   2  *      xt_conntrack - Netfilter module to match connection tracking
   3  *      information. (Superset of Rusty's minimalistic state match.)
   4  *
   5  *      (C) 2001  Marc Boucher (marc@mbsi.ca).
   6  *      Copyright © CC Computer Consultants GmbH, 2007 - 2008
   7  *
   8  *      This program is free software; you can redistribute it and/or modify
   9  *      it under the terms of the GNU General Public License version 2 as
  10  *      published by the Free Software Foundation.
  11  */
  12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13 #include <linux/module.h>
  14 #include <linux/skbuff.h>
  15 #include <net/ipv6.h>
  16 #include <linux/netfilter/x_tables.h>
  17 #include <linux/netfilter/xt_conntrack.h>
  18 #include <net/netfilter/nf_conntrack.h>
  19
  20 MODULE_LICENSE("GPL");
  21 MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
  22 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
  23 MODULE_DESCRIPTION("Xtables: connection tracking state match");
  24 MODULE_ALIAS("ipt_conntrack");
  25 MODULE_ALIAS("ip6t_conntrack");
  26
  27 static bool
  28 conntrack_addrcmp(const union nf_inet_addr *kaddr,
  29                   const union nf_inet_addr *uaddr,
  30                   const union nf_inet_addr *umask, unsigned int l3proto)
  31 {
  32         if (l3proto == NFPROTO_IPV4)
  33                 return ((kaddr->ip ^ uaddr->ip) & umask->ip) == 0;
  34         else if (l3proto == NFPROTO_IPV6)
  35                 return ipv6_masked_addr_cmp(&kaddr->in6, &umask->in6,
  36                        &uaddr->in6) == 0;
  37         else
  38                 return false;
  39 }
  40
  41 static inline bool
  42 conntrack_mt_origsrc(const struct nf_conn *ct,
  43                      const struct xt_conntrack_mtinfo2 *info,
  44                      u_int8_t family)
  45 {
  46         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
  47                &info->origsrc_addr, &info->origsrc_mask, family);
  48 }
  49
  50 static inline bool
  51 conntrack_mt_origdst(const struct nf_conn *ct,
  52                      const struct xt_conntrack_mtinfo2 *info,
  53                      u_int8_t family)
  54 {
  55         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3,
  56                &info->origdst_addr, &info->origdst_mask, family);
  57 }
  58
  59 static inline bool
  60 conntrack_mt_replsrc(const struct nf_conn *ct,
  61                      const struct xt_conntrack_mtinfo2 *info,
  62                      u_int8_t family)
  63 {
  64         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3,
  65                &info->replsrc_addr, &info->replsrc_mask, family);
  66 }
  67
  68 static inline bool
  69 conntrack_mt_repldst(const struct nf_conn *ct,
  70                      const struct xt_conntrack_mtinfo2 *info,
  71                      u_int8_t family)
  72 {
  73         return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3,
  74                &info->repldst_addr, &info->repldst_mask, family);
  75 }
  76
  77 static inline bool
  78 ct_proto_port_check(const struct xt_conntrack_mtinfo2 *info,
  79                     const struct nf_conn *ct)
  80 {
  81         const struct nf_conntrack_tuple *tuple;
  82
  83         tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
  84         if ((info->match_flags & XT_CONNTRACK_PROTO) &&
  85             (nf_ct_protonum(ct) == info->l4proto) ^
  86             !(info->invert_flags & XT_CONNTRACK_PROTO))
  87                 return false;
  88
  89         /* Shortcut to match all recognized protocols by using ->src.all. */
  90         if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
  91             (tuple->src.u.all == info->origsrc_port) ^
  92             !(info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
  93                 return false;
  94
  95         if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
  96             (tuple->dst.u.all == info->origdst_port) ^
  97             !(info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
  98                 return false;
  99
 100         tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
 101
 102         if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
 103             (tuple->src.u.all == info->replsrc_port) ^
 104             !(info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
 105                 return false;
 106
 107         if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
 108             (tuple->dst.u.all == info->repldst_port) ^
 109             !(info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
 110                 return false;
 111
 112         return true;
 113 }
 114
 115 static bool
 116 conntrack_mt(const struct sk_buff *skb, struct xt_action_param *par,
 117              u16 state_mask, u16 status_mask)
 118 {
 119         const struct xt_conntrack_mtinfo2 *info = par->matchinfo;
 120         enum ip_conntrack_info ctinfo;
 121         const struct nf_conn *ct;
 122         unsigned int statebit;
 123
 124         ct = nf_ct_get(skb, &ctinfo);
 125
 126         if (ct == &nf_conntrack_untracked)
 127                 statebit = XT_CONNTRACK_STATE_UNTRACKED;
 128         else if (ct != NULL)
 129                 statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
 130         else
 131                 statebit = XT_CONNTRACK_STATE_INVALID;
 132
 133         if (info->match_flags & XT_CONNTRACK_STATE) {
 134                 if (ct != NULL) {
 135                         if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
 136                                 statebit |= XT_CONNTRACK_STATE_SNAT;
 137                         if (test_bit(IPS_DST_NAT_BIT, &ct->status))
 138                                 statebit |= XT_CONNTRACK_STATE_DNAT;
 139                 }
 140                 if (!!(state_mask & statebit) ^
 141                     !(info->invert_flags & XT_CONNTRACK_STATE))
 142                         return false;
 143         }
 144
 145         if (ct == NULL)
 146                 return info->match_flags & XT_CONNTRACK_STATE;
 147         if ((info->match_flags & XT_CONNTRACK_DIRECTION) &&
 148             (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) ^
 149             !!(info->invert_flags & XT_CONNTRACK_DIRECTION))
 150                 return false;
 151
 152         if (info->match_flags & XT_CONNTRACK_ORIGSRC)
 153                 if (conntrack_mt_origsrc(ct, info, par->family) ^
 154                     !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
 155                         return false;
 156
 157         if (info->match_flags & XT_CONNTRACK_ORIGDST)
 158                 if (conntrack_mt_origdst(ct, info, par->family) ^
 159                     !(info->invert_flags & XT_CONNTRACK_ORIGDST))
 160                         return false;
 161
 162         if (info->match_flags & XT_CONNTRACK_REPLSRC)
 163                 if (conntrack_mt_replsrc(ct, info, par->family) ^
 164                     !(info->invert_flags & XT_CONNTRACK_REPLSRC))
 165                         return false;
 166
 167         if (info->match_flags & XT_CONNTRACK_REPLDST)
 168                 if (conntrack_mt_repldst(ct, info, par->family) ^
 169                     !(info->invert_flags & XT_CONNTRACK_REPLDST))
 170                         return false;
 171
 172         if (!ct_proto_port_check(info, ct))
 173                 return false;
 174
 175         if ((info->match_flags & XT_CONNTRACK_STATUS) &&
 176             (!!(status_mask & ct->status) ^
 177             !(info->invert_flags & XT_CONNTRACK_STATUS)))
 178                 return false;
 179
 180         if (info->match_flags & XT_CONNTRACK_EXPIRES) {
 181                 unsigned long expires = 0;
 182
 183                 if (timer_pending(&ct->timeout))
 184                         expires = (ct->timeout.expires - jiffies) / HZ;
 185                 if ((expires >= info->expires_min &&
 186                     expires <= info->expires_max) ^
 187                     !(info->invert_flags & XT_CONNTRACK_EXPIRES))
 188                         return false;
 189         }
 190         return true;
 191 }
 192
 193 static bool
 194 conntrack_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
 195 {
 196         const struct xt_conntrack_mtinfo1 *info = par->matchinfo;
 197
 198         return conntrack_mt(skb, par, info->state_mask, info->status_mask);
 199 }
 200
 201 static bool
 202 conntrack_mt_v2(const struct sk_buff *skb, struct xt_action_param *par)
 203 {
 204         const struct xt_conntrack_mtinfo2 *info = par->matchinfo;
 205
 206         return conntrack_mt(skb, par, info->state_mask, info->status_mask);
 207 }
 208
 209 static int conntrack_mt_check(const struct xt_mtchk_param *par)
 210 {
 211         int ret;
 212
 213         ret = nf_ct_l3proto_try_module_get(par->family);
 214         if (ret < 0)
 215                 pr_info("cannot load conntrack support for proto=%u\n",
 216                         par->family);
 217         return ret;
 218 }
 219
 220 static void conntrack_mt_destroy(const struct xt_mtdtor_param *par)
 221 {
 222         nf_ct_l3proto_module_put(par->family);
 223 }
 224
 225 static struct xt_match conntrack_mt_reg[] __read_mostly = {
 226         {
 227                 .name       = "conntrack",
 228                 .revision   = 1,
 229                 .family     = NFPROTO_UNSPEC,
 230                 .matchsize  = sizeof(struct xt_conntrack_mtinfo1),
 231                 .match      = conntrack_mt_v1,
 232                 .checkentry = conntrack_mt_check,
 233                 .destroy    = conntrack_mt_destroy,
 234                 .me         = THIS_MODULE,
 235         },
 236         {
 237                 .name       = "conntrack",
 238                 .revision   = 2,
 239                 .family     = NFPROTO_UNSPEC,
 240                 .matchsize  = sizeof(struct xt_conntrack_mtinfo2),
 241                 .match      = conntrack_mt_v2,
 242                 .checkentry = conntrack_mt_check,
 243                 .destroy    = conntrack_mt_destroy,
 244                 .me         = THIS_MODULE,
 245         },
 246 };
 247
 248 static int __init conntrack_mt_init(void)
 249 {
 250         return xt_register_matches(conntrack_mt_reg,
 251                ARRAY_SIZE(conntrack_mt_reg));
 252 }
 253
 254 static void __exit conntrack_mt_exit(void)
 255 {
 256         xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
 257 }
 258
 259 module_init(conntrack_mt_init);
 260 module_exit(conntrack_mt_exit);