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 int
  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       int *hotdrop)
  31 {
  32         const struct xt_conntrack_info *sinfo = matchinfo;
  33         struct nf_conn *ct;
  34         enum ip_conntrack_info ctinfo;
  35         unsigned int statebit;
  36
  37         ct = nf_ct_get((struct sk_buff *)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 0;
  58         }
  59
  60         if (ct == NULL) {
  61                 if (sinfo->flags & ~XT_CONNTRACK_STATE)
  62                         return 0;
  63                 return 1;
  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 0;
  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 0;
  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 0;
  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 0;
  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 0;
  99
 100         if (sinfo->flags & XT_CONNTRACK_STATUS &&
 101             FWINV((ct->status & sinfo->statusmask) == 0,
 102                   XT_CONNTRACK_STATUS))
 103                 return 0;
 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 0;
 113         }
 114         return 1;
 115 }
 116
 117 static int
 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 0;
 128         }
 129         return 1;
 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 static struct xt_match conntrack_match = {
 138         .name           = "conntrack",
 139         .match          = match,
 140         .checkentry     = checkentry,
 141         .destroy        = destroy,
 142         .matchsize      = sizeof(struct xt_conntrack_info),
 143         .family         = AF_INET,
 144         .me             = THIS_MODULE,
 145 };
 146
 147 static int __init xt_conntrack_init(void)
 148 {
 149         return xt_register_match(&conntrack_match);
 150 }
 151
 152 static void __exit xt_conntrack_fini(void)
 153 {
 154         xt_unregister_match(&conntrack_match);
 155 }
 156
 157 module_init(xt_conntrack_init);
 158 module_exit(xt_conntrack_fini);