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(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip !=
  60                             ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip)
  61                                 statebit |= XT_CONNTRACK_STATE_SNAT;
  62
  63                         if(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip !=
  64                             ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip)
  65                                 statebit |= XT_CONNTRACK_STATE_DNAT;
  66                 }
  67
  68                 if (FWINV((statebit & sinfo->statemask) == 0, XT_CONNTRACK_STATE))
  69                         return 0;
  70         }
  71
  72         if(sinfo->flags & XT_CONNTRACK_PROTO) {
  73                 if (!ct || FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum != sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum, XT_CONNTRACK_PROTO))
  74                         return 0;
  75         }
  76
  77         if(sinfo->flags & XT_CONNTRACK_ORIGSRC) {
  78                 if (!ct || FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip&sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) != sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip, XT_CONNTRACK_ORIGSRC))
  79                         return 0;
  80         }
  81
  82         if(sinfo->flags & XT_CONNTRACK_ORIGDST) {
  83                 if (!ct || FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip&sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) != sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip, XT_CONNTRACK_ORIGDST))
  84                         return 0;
  85         }
  86
  87         if(sinfo->flags & XT_CONNTRACK_REPLSRC) {
  88                 if (!ct || FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip&sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) != sinfo->tuple[IP_CT_DIR_REPLY].src.ip, XT_CONNTRACK_REPLSRC))
  89                         return 0;
  90         }
  91
  92         if(sinfo->flags & XT_CONNTRACK_REPLDST) {
  93                 if (!ct || FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip&sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) != sinfo->tuple[IP_CT_DIR_REPLY].dst.ip, XT_CONNTRACK_REPLDST))
  94                         return 0;
  95         }
  96
  97         if(sinfo->flags & XT_CONNTRACK_STATUS) {
  98                 if (!ct || FWINV((ct->status & sinfo->statusmask) == 0, XT_CONNTRACK_STATUS))
  99                         return 0;
 100         }
 101
 102         if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
 103                 unsigned long expires;
 104
 105                 if(!ct)
 106                         return 0;
 107
 108                 expires = timer_pending(&ct->timeout) ? (ct->timeout.expires - jiffies)/HZ : 0;
 109
 110                 if (FWINV(!(expires >= sinfo->expires_min && expires <= sinfo->expires_max), XT_CONNTRACK_EXPIRES))
 111                         return 0;
 112         }
 113
 114         return 1;
 115 }
 116
 117 #else /* CONFIG_IP_NF_CONNTRACK */
 118 static int
 119 match(const struct sk_buff *skb,
 120       const struct net_device *in,
 121       const struct net_device *out,
 122       const struct xt_match *match,
 123       const void *matchinfo,
 124       int offset,
 125       unsigned int protoff,
 126       int *hotdrop)
 127 {
 128         const struct xt_conntrack_info *sinfo = matchinfo;
 129         struct nf_conn *ct;
 130         enum ip_conntrack_info ctinfo;
 131         unsigned int statebit;
 132
 133         ct = nf_ct_get((struct sk_buff *)skb, &ctinfo);
 134
 135 #define FWINV(bool,invflg) ((bool) ^ !!(sinfo->invflags & invflg))
 136
 137         if (ct == &nf_conntrack_untracked)
 138                 statebit = XT_CONNTRACK_STATE_UNTRACKED;
 139         else if (ct)
 140                 statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
 141         else
 142                 statebit = XT_CONNTRACK_STATE_INVALID;
 143
 144         if(sinfo->flags & XT_CONNTRACK_STATE) {
 145                 if (ct) {
 146                         if(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip !=
 147                             ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip)
 148                                 statebit |= XT_CONNTRACK_STATE_SNAT;
 149
 150                         if(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip !=
 151                             ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip)
 152                                 statebit |= XT_CONNTRACK_STATE_DNAT;
 153                 }
 154
 155                 if (FWINV((statebit & sinfo->statemask) == 0, XT_CONNTRACK_STATE))
 156                         return 0;
 157         }
 158
 159         if(sinfo->flags & XT_CONNTRACK_PROTO) {
 160                 if (!ct || FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum != sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum, XT_CONNTRACK_PROTO))
 161                         return 0;
 162         }
 163
 164         if(sinfo->flags & XT_CONNTRACK_ORIGSRC) {
 165                 if (!ct || FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip&sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) != sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip, XT_CONNTRACK_ORIGSRC))
 166                         return 0;
 167         }
 168
 169         if(sinfo->flags & XT_CONNTRACK_ORIGDST) {
 170                 if (!ct || FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip&sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) != sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip, XT_CONNTRACK_ORIGDST))
 171                         return 0;
 172         }
 173
 174         if(sinfo->flags & XT_CONNTRACK_REPLSRC) {
 175                 if (!ct || FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip&sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) != sinfo->tuple[IP_CT_DIR_REPLY].src.ip, XT_CONNTRACK_REPLSRC))
 176                         return 0;
 177         }
 178
 179         if(sinfo->flags & XT_CONNTRACK_REPLDST) {
 180                 if (!ct || FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip&sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) != sinfo->tuple[IP_CT_DIR_REPLY].dst.ip, XT_CONNTRACK_REPLDST))
 181                         return 0;
 182         }
 183
 184         if(sinfo->flags & XT_CONNTRACK_STATUS) {
 185                 if (!ct || FWINV((ct->status & sinfo->statusmask) == 0, XT_CONNTRACK_STATUS))
 186                         return 0;
 187         }
 188
 189         if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
 190                 unsigned long expires;
 191
 192                 if(!ct)
 193                         return 0;
 194
 195                 expires = timer_pending(&ct->timeout) ? (ct->timeout.expires - jiffies)/HZ : 0;
 196
 197                 if (FWINV(!(expires >= sinfo->expires_min && expires <= sinfo->expires_max), XT_CONNTRACK_EXPIRES))
 198                         return 0;
 199         }
 200
 201         return 1;
 202 }
 203
 204 #endif /* CONFIG_NF_IP_CONNTRACK */
 205
 206 static int
 207 checkentry(const char *tablename,
 208            const void *ip,
 209            const struct xt_match *match,
 210            void *matchinfo,
 211            unsigned int hook_mask)
 212 {
 213 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 214         if (nf_ct_l3proto_try_module_get(match->family) < 0) {
 215                 printk(KERN_WARNING "can't load nf_conntrack support for "
 216                                     "proto=%d\n", match->family);
 217                 return 0;
 218         }
 219 #endif
 220         return 1;
 221 }
 222
 223 static void
 224 destroy(const struct xt_match *match, void *matchinfo)
 225 {
 226 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 227         nf_ct_l3proto_module_put(match->family);
 228 #endif
 229 }
 230
 231 static struct xt_match conntrack_match = {
 232         .name           = "conntrack",
 233         .match          = match,
 234         .checkentry     = checkentry,
 235         .destroy        = destroy,
 236         .matchsize      = sizeof(struct xt_conntrack_info),
 237         .family         = AF_INET,
 238         .me             = THIS_MODULE,
 239 };
 240
 241 static int __init xt_conntrack_init(void)
 242 {
 243         need_conntrack();
 244         return xt_register_match(&conntrack_match);
 245 }
 246
 247 static void __exit xt_conntrack_fini(void)
 248 {
 249         xt_unregister_match(&conntrack_match);
 250 }
 251
 252 module_init(xt_conntrack_init);
 253 module_exit(xt_conntrack_fini);