net/netfilter/xt_CONNMARK.c

   1 /* This kernel module is used to modify the connection mark values, or
   2  * to optionally restore the skb nfmark from the connection mark
   3  *
   4  * Copyright (C) 2002,2004 MARA Systems AB <http://www.marasystems.com>
   5  * by Henrik Nordstrom <hno@marasystems.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21 #include <linux/module.h>
  22 #include <linux/skbuff.h>
  23 #include <linux/ip.h>
  24 #include <net/checksum.h>
  25
  26 MODULE_AUTHOR("Henrik Nordstrom <hno@marasystems.com>");
  27 MODULE_DESCRIPTION("IP tables CONNMARK matching module");
  28 MODULE_LICENSE("GPL");
  29 MODULE_ALIAS("ipt_CONNMARK");
  30 MODULE_ALIAS("ip6t_CONNMARK");
  31
  32 #include <linux/netfilter/x_tables.h>
  33 #include <linux/netfilter/xt_CONNMARK.h>
  34 #include <net/netfilter/nf_conntrack_ecache.h>
  35
  36 static unsigned int
  37 target(struct sk_buff *skb,
  38        const struct net_device *in,
  39        const struct net_device *out,
  40        unsigned int hooknum,
  41        const struct xt_target *target,
  42        const void *targinfo)
  43 {
  44         const struct xt_connmark_target_info *markinfo = targinfo;
  45         struct nf_conn *ct;
  46         enum ip_conntrack_info ctinfo;
  47         u_int32_t diff;
  48         u_int32_t mark;
  49         u_int32_t newmark;
  50
  51         ct = nf_ct_get(skb, &ctinfo);
  52         if (ct) {
  53                 switch(markinfo->mode) {
  54                 case XT_CONNMARK_SET:
  55                         newmark = (ct->mark & ~markinfo->mask) | markinfo->mark;
  56                         if (newmark != ct->mark) {
  57                                 ct->mark = newmark;
  58                                 nf_conntrack_event_cache(IPCT_MARK, skb);
  59                         }
  60                         break;
  61                 case XT_CONNMARK_SAVE:
  62                         newmark = (ct->mark & ~markinfo->mask) |
  63                                   (skb->mark & markinfo->mask);
  64                         if (ct->mark != newmark) {
  65                                 ct->mark = newmark;
  66                                 nf_conntrack_event_cache(IPCT_MARK, skb);
  67                         }
  68                         break;
  69                 case XT_CONNMARK_RESTORE:
  70                         mark = skb->mark;
  71                         diff = (ct->mark ^ mark) & markinfo->mask;
  72                         skb->mark = mark ^ diff;
  73                         break;
  74                 }
  75         }
  76
  77         return XT_CONTINUE;
  78 }
  79
  80 static bool
  81 checkentry(const char *tablename,
  82            const void *entry,
  83            const struct xt_target *target,
  84            void *targinfo,
  85            unsigned int hook_mask)
  86 {
  87         const struct xt_connmark_target_info *matchinfo = targinfo;
  88
  89         if (matchinfo->mode == XT_CONNMARK_RESTORE) {
  90                 if (strcmp(tablename, "mangle") != 0) {
  91                         printk(KERN_WARNING "CONNMARK: restore can only be "
  92                                "called from \"mangle\" table, not \"%s\"\n",
  93                                tablename);
  94                         return false;
  95                 }
  96         }
  97         if (matchinfo->mark > 0xffffffff || matchinfo->mask > 0xffffffff) {
  98                 printk(KERN_WARNING "CONNMARK: Only supports 32bit mark\n");
  99                 return false;
 100         }
 101         if (nf_ct_l3proto_try_module_get(target->family) < 0) {
 102                 printk(KERN_WARNING "can't load conntrack support for "
 103                                     "proto=%d\n", target->family);
 104                 return false;
 105         }
 106         return true;
 107 }
 108
 109 static void
 110 destroy(const struct xt_target *target, void *targinfo)
 111 {
 112         nf_ct_l3proto_module_put(target->family);
 113 }
 114
 115 #ifdef CONFIG_COMPAT
 116 struct compat_xt_connmark_target_info {
 117         compat_ulong_t  mark, mask;
 118         u_int8_t        mode;
 119         u_int8_t        __pad1;
 120         u_int16_t       __pad2;
 121 };
 122
 123 static void compat_from_user(void *dst, void *src)
 124 {
 125         const struct compat_xt_connmark_target_info *cm = src;
 126         struct xt_connmark_target_info m = {
 127                 .mark   = cm->mark,
 128                 .mask   = cm->mask,
 129                 .mode   = cm->mode,
 130         };
 131         memcpy(dst, &m, sizeof(m));
 132 }
 133
 134 static int compat_to_user(void __user *dst, void *src)
 135 {
 136         const struct xt_connmark_target_info *m = src;
 137         struct compat_xt_connmark_target_info cm = {
 138                 .mark   = m->mark,
 139                 .mask   = m->mask,
 140                 .mode   = m->mode,
 141         };
 142         return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
 143 }
 144 #endif /* CONFIG_COMPAT */
 145
 146 static struct xt_target xt_connmark_target[] __read_mostly = {
 147         {
 148                 .name           = "CONNMARK",
 149                 .family         = AF_INET,
 150                 .checkentry     = checkentry,
 151                 .destroy        = destroy,
 152                 .target         = target,
 153                 .targetsize     = sizeof(struct xt_connmark_target_info),
 154 #ifdef CONFIG_COMPAT
 155                 .compatsize     = sizeof(struct compat_xt_connmark_target_info),
 156                 .compat_from_user = compat_from_user,
 157                 .compat_to_user = compat_to_user,
 158 #endif
 159                 .me             = THIS_MODULE
 160         },
 161         {
 162                 .name           = "CONNMARK",
 163                 .family         = AF_INET6,
 164                 .checkentry     = checkentry,
 165                 .destroy        = destroy,
 166                 .target         = target,
 167                 .targetsize     = sizeof(struct xt_connmark_target_info),
 168                 .me             = THIS_MODULE
 169         },
 170 };
 171
 172 static int __init xt_connmark_init(void)
 173 {
 174         return xt_register_targets(xt_connmark_target,
 175                                    ARRAY_SIZE(xt_connmark_target));
 176 }
 177
 178 static void __exit xt_connmark_fini(void)
 179 {
 180         xt_unregister_targets(xt_connmark_target,
 181                               ARRAY_SIZE(xt_connmark_target));
 182 }
 183
 184 module_init(xt_connmark_init);
 185 module_exit(xt_connmark_fini);