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 #include <linux/netfilter/x_tables.h>
  14 #include <linux/netfilter/xt_conntrack.h>
  15 #include <net/netfilter/nf_conntrack.h>
  16
  17 MODULE_LICENSE("GPL");
  18 MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
  19 MODULE_DESCRIPTION("iptables connection tracking match module");
  20 MODULE_ALIAS("ipt_conntrack");
  21
  22 static bool
  23 conntrack_mt(const struct sk_buff *skb, const struct net_device *in,
  24              const struct net_device *out, const struct xt_match *match,
  25              const void *matchinfo, int offset, unsigned int protoff,
  26              bool *hotdrop)
  27 {
  28         const struct xt_conntrack_info *sinfo = matchinfo;
  29         const struct nf_conn *ct;
  30         enum ip_conntrack_info ctinfo;
  31         unsigned int statebit;
  32
  33         ct = nf_ct_get(skb, &ctinfo);
  34
  35 #define FWINV(bool, invflg) ((bool) ^ !!(sinfo->invflags & (invflg)))
  36
  37         if (ct == &nf_conntrack_untracked)
  38                 statebit = XT_CONNTRACK_STATE_UNTRACKED;
  39         else if (ct)
  40                 statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
  41         else
  42                 statebit = XT_CONNTRACK_STATE_INVALID;
  43
  44         if (sinfo->flags & XT_CONNTRACK_STATE) {
  45                 if (ct) {
  46                         if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
  47                                 statebit |= XT_CONNTRACK_STATE_SNAT;
  48                         if (test_bit(IPS_DST_NAT_BIT, &ct->status))
  49                                 statebit |= XT_CONNTRACK_STATE_DNAT;
  50                 }
  51                 if (FWINV((statebit & sinfo->statemask) == 0,
  52                           XT_CONNTRACK_STATE))
  53                         return false;
  54         }
  55
  56         if (ct == NULL) {
  57                 if (sinfo->flags & ~XT_CONNTRACK_STATE)
  58                         return false;
  59                 return true;
  60         }
  61
  62         if (sinfo->flags & XT_CONNTRACK_PROTO &&
  63             FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum !=
  64                   sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
  65                   XT_CONNTRACK_PROTO))
  66                 return false;
  67
  68         if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
  69             FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip &
  70                    sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
  71                   sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
  72                   XT_CONNTRACK_ORIGSRC))
  73                 return false;
  74
  75         if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
  76             FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip &
  77                    sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
  78                   sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
  79                   XT_CONNTRACK_ORIGDST))
  80                 return false;
  81
  82         if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
  83             FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip &
  84                    sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
  85                   sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
  86                   XT_CONNTRACK_REPLSRC))
  87                 return false;
  88
  89         if (sinfo->flags & XT_CONNTRACK_REPLDST &&
  90             FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip &
  91                    sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
  92                   sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
  93                   XT_CONNTRACK_REPLDST))
  94                 return false;
  95
  96         if (sinfo->flags & XT_CONNTRACK_STATUS &&
  97             FWINV((ct->status & sinfo->statusmask) == 0,
  98                   XT_CONNTRACK_STATUS))
  99                 return false;
 100
 101         if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
 102                 unsigned long expires = timer_pending(&ct->timeout) ?
 103                                         (ct->timeout.expires - jiffies)/HZ : 0;
 104
 105                 if (FWINV(!(expires >= sinfo->expires_min &&
 106                             expires <= sinfo->expires_max),
 107                           XT_CONNTRACK_EXPIRES))
 108                         return false;
 109         }
 110         return true;
 111 #undef FWINV
 112 }
 113
 114 static bool
 115 conntrack_mt_check(const char *tablename, const void *ip,
 116                    const struct xt_match *match, void *matchinfo,
 117                    unsigned int hook_mask)
 118 {
 119         if (nf_ct_l3proto_try_module_get(match->family) < 0) {
 120                 printk(KERN_WARNING "can't load conntrack support for "
 121                                     "proto=%u\n", match->family);
 122                 return false;
 123         }
 124         return true;
 125 }
 126
 127 static void
 128 conntrack_mt_destroy(const struct xt_match *match, void *matchinfo)
 129 {
 130         nf_ct_l3proto_module_put(match->family);
 131 }
 132
 133 #ifdef CONFIG_COMPAT
 134 struct compat_xt_conntrack_info
 135 {
 136         compat_uint_t                   statemask;
 137         compat_uint_t                   statusmask;
 138         struct ip_conntrack_old_tuple   tuple[IP_CT_DIR_MAX];
 139         struct in_addr                  sipmsk[IP_CT_DIR_MAX];
 140         struct in_addr                  dipmsk[IP_CT_DIR_MAX];
 141         compat_ulong_t                  expires_min;
 142         compat_ulong_t                  expires_max;
 143         u_int8_t                        flags;
 144         u_int8_t                        invflags;
 145 };
 146
 147 static void conntrack_mt_compat_from_user(void *dst, void *src)
 148 {
 149         const struct compat_xt_conntrack_info *cm = src;
 150         struct xt_conntrack_info m = {
 151                 .statemask      = cm->statemask,
 152                 .statusmask     = cm->statusmask,
 153                 .expires_min    = cm->expires_min,
 154                 .expires_max    = cm->expires_max,
 155                 .flags          = cm->flags,
 156                 .invflags       = cm->invflags,
 157         };
 158         memcpy(m.tuple, cm->tuple, sizeof(m.tuple));
 159         memcpy(m.sipmsk, cm->sipmsk, sizeof(m.sipmsk));
 160         memcpy(m.dipmsk, cm->dipmsk, sizeof(m.dipmsk));
 161         memcpy(dst, &m, sizeof(m));
 162 }
 163
 164 static int conntrack_mt_compat_to_user(void __user *dst, void *src)
 165 {
 166         const struct xt_conntrack_info *m = src;
 167         struct compat_xt_conntrack_info cm = {
 168                 .statemask      = m->statemask,
 169                 .statusmask     = m->statusmask,
 170                 .expires_min    = m->expires_min,
 171                 .expires_max    = m->expires_max,
 172                 .flags          = m->flags,
 173                 .invflags       = m->invflags,
 174         };
 175         memcpy(cm.tuple, m->tuple, sizeof(cm.tuple));
 176         memcpy(cm.sipmsk, m->sipmsk, sizeof(cm.sipmsk));
 177         memcpy(cm.dipmsk, m->dipmsk, sizeof(cm.dipmsk));
 178         return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
 179 }
 180 #endif
 181
 182 static struct xt_match conntrack_mt_reg __read_mostly = {
 183         .name           = "conntrack",
 184         .match          = conntrack_mt,
 185         .checkentry     = conntrack_mt_check,
 186         .destroy        = conntrack_mt_destroy,
 187         .matchsize      = sizeof(struct xt_conntrack_info),
 188 #ifdef CONFIG_COMPAT
 189         .compatsize     = sizeof(struct compat_xt_conntrack_info),
 190         .compat_from_user = conntrack_mt_compat_from_user,
 191         .compat_to_user = conntrack_mt_compat_to_user,
 192 #endif
 193         .family         = AF_INET,
 194         .me             = THIS_MODULE,
 195 };
 196
 197 static int __init conntrack_mt_init(void)
 198 {
 199         return xt_register_match(&conntrack_mt_reg);
 200 }
 201
 202 static void __exit conntrack_mt_exit(void)
 203 {
 204         xt_unregister_match(&conntrack_mt_reg);
 205 }
 206
 207 module_init(conntrack_mt_init);
 208 module_exit(conntrack_mt_exit);