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 match(const struct sk_buff *skb,
  24       const struct net_device *in,
  25       const struct net_device *out,
  26       const struct xt_match *match,
  27       const void *matchinfo,
  28       int offset,
  29       unsigned int protoff,
  30       bool *hotdrop)
  31 {
  32         const struct xt_conntrack_info *sinfo = matchinfo;
  33         const struct nf_conn *ct;
  34         enum ip_conntrack_info ctinfo;
  35         unsigned int statebit;
  36
  37         ct = nf_ct_get(skb, &ctinfo);
  38
  39 #define FWINV(bool,invflg) ((bool) ^ !!(sinfo->invflags & invflg))
  40
  41         if (ct == &nf_conntrack_untracked)
  42                 statebit = XT_CONNTRACK_STATE_UNTRACKED;
  43         else if (ct)
  44                 statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
  45         else
  46                 statebit = XT_CONNTRACK_STATE_INVALID;
  47
  48         if (sinfo->flags & XT_CONNTRACK_STATE) {
  49                 if (ct) {
  50                         if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
  51                                 statebit |= XT_CONNTRACK_STATE_SNAT;
  52                         if (test_bit(IPS_DST_NAT_BIT, &ct->status))
  53                                 statebit |= XT_CONNTRACK_STATE_DNAT;
  54                 }
  55                 if (FWINV((statebit & sinfo->statemask) == 0,
  56                           XT_CONNTRACK_STATE))
  57                         return false;
  58         }
  59
  60         if (ct == NULL) {
  61                 if (sinfo->flags & ~XT_CONNTRACK_STATE)
  62                         return false;
  63                 return true;
  64         }
  65
  66         if (sinfo->flags & XT_CONNTRACK_PROTO &&
  67             FWINV(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.protonum !=
  68                   sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.protonum,
  69                   XT_CONNTRACK_PROTO))
  70                 return false;
  71
  72         if (sinfo->flags & XT_CONNTRACK_ORIGSRC &&
  73             FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip &
  74                    sinfo->sipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
  75                   sinfo->tuple[IP_CT_DIR_ORIGINAL].src.ip,
  76                   XT_CONNTRACK_ORIGSRC))
  77                 return false;
  78
  79         if (sinfo->flags & XT_CONNTRACK_ORIGDST &&
  80             FWINV((ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3.ip &
  81                    sinfo->dipmsk[IP_CT_DIR_ORIGINAL].s_addr) !=
  82                   sinfo->tuple[IP_CT_DIR_ORIGINAL].dst.ip,
  83                   XT_CONNTRACK_ORIGDST))
  84                 return false;
  85
  86         if (sinfo->flags & XT_CONNTRACK_REPLSRC &&
  87             FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip &
  88                    sinfo->sipmsk[IP_CT_DIR_REPLY].s_addr) !=
  89                   sinfo->tuple[IP_CT_DIR_REPLY].src.ip,
  90                   XT_CONNTRACK_REPLSRC))
  91                 return false;
  92
  93         if (sinfo->flags & XT_CONNTRACK_REPLDST &&
  94             FWINV((ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip &
  95                    sinfo->dipmsk[IP_CT_DIR_REPLY].s_addr) !=
  96                   sinfo->tuple[IP_CT_DIR_REPLY].dst.ip,
  97                   XT_CONNTRACK_REPLDST))
  98                 return false;
  99
 100         if (sinfo->flags & XT_CONNTRACK_STATUS &&
 101             FWINV((ct->status & sinfo->statusmask) == 0,
 102                   XT_CONNTRACK_STATUS))
 103                 return false;
 104
 105         if(sinfo->flags & XT_CONNTRACK_EXPIRES) {
 106                 unsigned long expires = timer_pending(&ct->timeout) ?
 107                                         (ct->timeout.expires - jiffies)/HZ : 0;
 108
 109                 if (FWINV(!(expires >= sinfo->expires_min &&
 110                             expires <= sinfo->expires_max),
 111                           XT_CONNTRACK_EXPIRES))
 112                         return false;
 113         }
 114         return true;
 115 }
 116
 117 static bool
 118 checkentry(const char *tablename,
 119            const void *ip,
 120            const struct xt_match *match,
 121            void *matchinfo,
 122            unsigned int hook_mask)
 123 {
 124         if (nf_ct_l3proto_try_module_get(match->family) < 0) {
 125                 printk(KERN_WARNING "can't load conntrack support for "
 126                                     "proto=%d\n", match->family);
 127                 return false;
 128         }
 129         return true;
 130 }
 131
 132 static void destroy(const struct xt_match *match, void *matchinfo)
 133 {
 134         nf_ct_l3proto_module_put(match->family);
 135 }
 136
 137 #ifdef CONFIG_COMPAT
 138 struct compat_xt_conntrack_info
 139 {
 140         compat_uint_t                   statemask;
 141         compat_uint_t                   statusmask;
 142         struct ip_conntrack_old_tuple   tuple[IP_CT_DIR_MAX];
 143         struct in_addr                  sipmsk[IP_CT_DIR_MAX];
 144         struct in_addr                  dipmsk[IP_CT_DIR_MAX];
 145         compat_ulong_t                  expires_min;
 146         compat_ulong_t                  expires_max;
 147         u_int8_t                        flags;
 148         u_int8_t                        invflags;
 149 };
 150
 151 static void compat_from_user(void *dst, void *src)
 152 {
 153         const struct compat_xt_conntrack_info *cm = src;
 154         struct xt_conntrack_info m = {
 155                 .statemask      = cm->statemask,
 156                 .statusmask     = cm->statusmask,
 157                 .expires_min    = cm->expires_min,
 158                 .expires_max    = cm->expires_max,
 159                 .flags          = cm->flags,
 160                 .invflags       = cm->invflags,
 161         };
 162         memcpy(m.tuple, cm->tuple, sizeof(m.tuple));
 163         memcpy(m.sipmsk, cm->sipmsk, sizeof(m.sipmsk));
 164         memcpy(m.dipmsk, cm->dipmsk, sizeof(m.dipmsk));
 165         memcpy(dst, &m, sizeof(m));
 166 }
 167
 168 static int compat_to_user(void __user *dst, void *src)
 169 {
 170         const struct xt_conntrack_info *m = src;
 171         struct compat_xt_conntrack_info cm = {
 172                 .statemask      = m->statemask,
 173                 .statusmask     = m->statusmask,
 174                 .expires_min    = m->expires_min,
 175                 .expires_max    = m->expires_max,
 176                 .flags          = m->flags,
 177                 .invflags       = m->invflags,
 178         };
 179         memcpy(cm.tuple, m->tuple, sizeof(cm.tuple));
 180         memcpy(cm.sipmsk, m->sipmsk, sizeof(cm.sipmsk));
 181         memcpy(cm.dipmsk, m->dipmsk, sizeof(cm.dipmsk));
 182         return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
 183 }
 184 #endif
 185
 186 static struct xt_match conntrack_match __read_mostly = {
 187         .name           = "conntrack",
 188         .match          = match,
 189         .checkentry     = checkentry,
 190         .destroy        = destroy,
 191         .matchsize      = sizeof(struct xt_conntrack_info),
 192 #ifdef CONFIG_COMPAT
 193         .compatsize     = sizeof(struct compat_xt_conntrack_info),
 194         .compat_from_user = compat_from_user,
 195         .compat_to_user = compat_to_user,
 196 #endif
 197         .family         = AF_INET,
 198         .me             = THIS_MODULE,
 199 };
 200
 201 static int __init xt_conntrack_init(void)
 202 {
 203         return xt_register_match(&conntrack_match);
 204 }
 205
 206 static void __exit xt_conntrack_fini(void)
 207 {
 208         xt_unregister_match(&conntrack_match);
 209 }
 210
 211 module_init(xt_conntrack_init);
 212 module_exit(xt_conntrack_fini);