net/netfilter/xt_conntrack.c

   1 /* Kernel module to match connection tracking information.
   2  * Superset of Rusty's minimalistic state match.
   3  *
   4  * (C) 2001  Marc Boucher (marc@mbsi.ca).
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/skbuff.h>
  13
  14 #if defined(CONFIG_IP_NF_CONNTRACK) || defined(CONFIG_IP_NF_CONNTRACK_MODULE)
  15 #include <linux/netfilter_ipv4/ip_conntrack.h>
  16 #include <linux/netfilter_ipv4/ip_conntrack_tuple.h>
  17 #else
  18 #include <net/netfilter/nf_conntrack.h>
  19 #endif
  20
  21 #include <linux/netfilter/x_tables.h>
  22 #include <linux/netfilter/xt_conntrack.h>
  23
  24 MODULE_LICENSE("GPL");
  25 MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
  26 MODULE_DESCRIPTION("iptables connection tracking match module");
  27 MODULE_ALIAS("ipt_conntrack");
  28
  29 #if defined(CONFIG_IP_NF_CONNTRACK) || defined(CONFIG_IP_NF_CONNTRACK_MODULE)
  30
  31 static int
  32 match(const struct sk_buff *skb,
  33       const struct net_device *in,
  34       const struct net_device *out,
  35       const struct xt_match *match,
  36       const void *matchinfo,
  37       int offset,
  38       unsigned int protoff,
  39       int *hotdrop)
  40 {
  41         const struct xt_conntrack_info *sinfo = matchinfo;
  42         struct ip_conntrack *ct;
  43         enum ip_conntrack_info ctinfo;
  44         unsigned int statebit;
  45
  46         ct = ip_conntrack_get((struct sk_buff *)skb, &ctinfo);
  47
  48 #define FWINV(bool, invflg) ((bool) ^ !!(sinfo->invflags & invflg))
  49
  50         if (ct == &ip_conntrack_untracked)
  51                 statebit = XT_CONNTRACK_STATE_UNTRACKED;
  52         else if (ct)
  53                 statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
  54         else
  55                 statebit = XT_CONNTRACK_STATE_INVALID;
  56
  57         if (sinfo->flags & XT_CONNTRACK_STATE) {
  58                 if (ct) {
  59                         if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
  60                                 statebit |= XT_CONNTRACK_STATE_SNAT;
  61                         if (test_bit(IPS_DST_NAT_BIT, &ct->status))
  62                                 statebit |= XT_CONNTRACK_STATE_DNAT;
  63                 }
  64                 if (FWINV((statebit & sinfo->statemask) == 0,
  65                           XT_CONNTRACK_STATE))
  66                         return 0;
  67         }
  68
  69         if (ct == NULL) {
  70                 if (sinfo->flags & ~XT_CONNTRACK_STATE)
  71                         return 0;
  72                 return 1;
  73         }
  74
  75         if (sinfo->flags & XT_CONNTRACK_PROTO &&
  76             FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum !=
  77                   sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
  78                   XT_CONNTRACK_PROTO))
  79                 return 0;
  80
  81         if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
  82             FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip &
  83                    sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
  84                   sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
  85                   XT_CONNTRACK_ORIGSRC))
  86                 return 0;
  87
  88         if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
  89             FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip &
  90                    sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
  91                   sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
  92                   XT_CONNTRACK_ORIGDST))
  93                 return 0;
  94
  95         if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
  96             FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip &
  97                    sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
  98                   sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
  99                   XT_CONNTRACK_REPLSRC))
 100                 return 0;
 101
 102         if (sinfo->flags & XT_CONNTRACK_REPLDST &&
 103             FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip &
 104                    sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
 105                   sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
 106                   XT_CONNTRACK_REPLDST))
 107                 return 0;
 108
 109         if (sinfo->flags & XT_CONNTRACK_STATUS &&
 110             FWINV((ct->status & sinfo->statusmask) == 0,
 111                   XT_CONNTRACK_STATUS))
 112                 return 0;
 113
 114         if (sinfo->flags & XT_CONNTRACK_EXPIRES) {
 115                 unsigned long expires = timer_pending(&ct->timeout) ?
 116                                         (ct->timeout.expires - jiffies)/HZ : 0;
 117
 118                 if (FWINV(!(expires >= sinfo->expires_min &&
 119                             expires <= sinfo->expires_max),
 120                           XT_CONNTRACK_EXPIRES))
 121                         return 0;
 122         }
 123         return 1;
 124 }
 125
 126 #else /* CONFIG_IP_NF_CONNTRACK */
 127 static int
 128 match(const struct sk_buff *skb,
 129       const struct net_device *in,
 130       const struct net_device *out,
 131       const struct xt_match *match,
 132       const void *matchinfo,
 133       int offset,
 134       unsigned int protoff,
 135       int *hotdrop)
 136 {
 137         const struct xt_conntrack_info *sinfo = matchinfo;
 138         struct nf_conn *ct;
 139         enum ip_conntrack_info ctinfo;
 140         unsigned int statebit;
 141
 142         ct = nf_ct_get((struct sk_buff *)skb, &ctinfo);
 143
 144 #define FWINV(bool,invflg) ((bool) ^ !!(sinfo->invflags & invflg))
 145
 146         if (ct == &nf_conntrack_untracked)
 147                 statebit = XT_CONNTRACK_STATE_UNTRACKED;
 148         else if (ct)
 149                 statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
 150         else
 151                 statebit = XT_CONNTRACK_STATE_INVALID;
 152
 153         if (sinfo->flags & XT_CONNTRACK_STATE) {
 154                 if (ct) {
 155                         if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
 156                                 statebit |= XT_CONNTRACK_STATE_SNAT;
 157                         if (test_bit(IPS_DST_NAT_BIT, &ct->status))
 158                                 statebit |= XT_CONNTRACK_STATE_DNAT;
 159                 }
 160                 if (FWINV((statebit & sinfo->statemask) == 0,
 161                           XT_CONNTRACK_STATE))
 162                         return 0;
 163         }
 164
 165         if (ct == NULL) {
 166                 if (sinfo->flags & ~XT_CONNTRACK_STATE)
 167                         return 0;
 168                 return 1;
 169         }
 170
 171         if (sinfo->flags & XT_CONNTRACK_PROTO &&
 172             FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum !=
 173                   sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
 174                   XT_CONNTRACK_PROTO))
 175                 return 0;
 176
 177         if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
 178             FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip &
 179                    sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
 180                   sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
 181                   XT_CONNTRACK_ORIGSRC))
 182                 return 0;
 183
 184         if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
 185             FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip &
 186                    sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
 187                   sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
 188                   XT_CONNTRACK_ORIGDST))
 189                 return 0;
 190
 191         if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
 192             FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip &
 193                    sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
 194                   sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
 195                   XT_CONNTRACK_REPLSRC))
 196                 return 0;
 197
 198         if (sinfo->flags & XT_CONNTRACK_REPLDST &&
 199             FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip &
 200                    sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
 201                   sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
 202                   XT_CONNTRACK_REPLDST))
 203                 return 0;
 204
 205         if (sinfo->flags & XT_CONNTRACK_STATUS &&
 206             FWINV((ct->status & sinfo->statusmask) == 0,
 207                   XT_CONNTRACK_STATUS))
 208                 return 0;
 209
 210         if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
 211                 unsigned long expires = timer_pending(&ct->timeout) ?
 212                                         (ct->timeout.expires - jiffies)/HZ : 0;
 213
 214                 if (FWINV(!(expires >= sinfo->expires_min &&
 215                             expires <= sinfo->expires_max),
 216                           XT_CONNTRACK_EXPIRES))
 217                         return 0;
 218         }
 219         return 1;
 220 }
 221
 222 #endif /* CONFIG_NF_IP_CONNTRACK */
 223
 224 static int
 225 checkentry(const char *tablename,
 226            const void *ip,
 227            const struct xt_match *match,
 228            void *matchinfo,
 229            unsigned int hook_mask)
 230 {
 231 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 232         if (nf_ct_l3proto_try_module_get(match->family) < 0) {
 233                 printk(KERN_WARNING "can't load nf_conntrack support for "
 234                                     "proto=%d\n", match->family);
 235                 return 0;
 236         }
 237 #endif
 238         return 1;
 239 }
 240
 241 static void destroy(const struct xt_match *match, void *matchinfo)
 242 {
 243 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 244         nf_ct_l3proto_module_put(match->family);
 245 #endif
 246 }
 247
 248 static struct xt_match conntrack_match = {
 249         .name           = "conntrack",
 250         .match          = match,
 251         .checkentry     = checkentry,
 252         .destroy        = destroy,
 253         .matchsize      = sizeof(struct xt_conntrack_info),
 254         .family         = AF_INET,
 255         .me             = THIS_MODULE,
 256 };
 257
 258 static int __init xt_conntrack_init(void)
 259 {
 260         need_conntrack();
 261         return xt_register_match(&conntrack_match);
 262 }
 263
 264 static void __exit xt_conntrack_fini(void)
 265 {
 266         xt_unregister_match(&conntrack_match);
 267 }
 268
 269 module_init(xt_conntrack_init);
 270 module_exit(xt_conntrack_fini);