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@marasytems.com>");
  27 MODULE_DESCRIPTION("IP tables CONNMARK matching module");
  28 MODULE_LICENSE("GPL");
  29 MODULE_ALIAS("ipt_CONNMARK");
  30
  31 #include <linux/netfilter/x_tables.h>
  32 #include <linux/netfilter/xt_CONNMARK.h>
  33 #include <net/netfilter/nf_conntrack_ecache.h>
  34
  35 static unsigned int
  36 target(struct sk_buff **pskb,
  37        const struct net_device *in,
  38        const struct net_device *out,
  39        unsigned int hooknum,
  40        const struct xt_target *target,
  41        const void *targinfo)
  42 {
  43         const struct xt_connmark_target_info *markinfo = targinfo;
  44         struct nf_conn *ct;
  45         enum ip_conntrack_info ctinfo;
  46         u_int32_t diff;
  47         u_int32_t mark;
  48         u_int32_t newmark;
  49
  50         ct = nf_ct_get(*pskb, &ctinfo);
  51         if (ct) {
  52                 switch(markinfo->mode) {
  53                 case XT_CONNMARK_SET:
  54                         newmark = (ct->mark & ~markinfo->mask) | markinfo->mark;
  55                         if (newmark != ct->mark) {
  56                                 ct->mark = newmark;
  57                                 nf_conntrack_event_cache(IPCT_MARK, *pskb);
  58                         }
  59                         break;
  60                 case XT_CONNMARK_SAVE:
  61                         newmark = (ct->mark & ~markinfo->mask) |
  62                                   ((*pskb)->mark & markinfo->mask);
  63                         if (ct->mark != newmark) {
  64                                 ct->mark = newmark;
  65                                 nf_conntrack_event_cache(IPCT_MARK, *pskb);
  66                         }
  67                         break;
  68                 case XT_CONNMARK_RESTORE:
  69                         mark = (*pskb)->mark;
  70                         diff = (ct->mark ^ mark) & markinfo->mask;
  71                         (*pskb)->mark = mark ^ diff;
  72                         break;
  73                 }
  74         }
  75
  76         return XT_CONTINUE;
  77 }
  78
  79 static int
  80 checkentry(const char *tablename,
  81            const void *entry,
  82            const struct xt_target *target,
  83            void *targinfo,
  84            unsigned int hook_mask)
  85 {
  86         struct xt_connmark_target_info *matchinfo = targinfo;
  87
  88         if (nf_ct_l3proto_try_module_get(target->family) < 0) {
  89                 printk(KERN_WARNING "can't load conntrack support for "
  90                                     "proto=%d\n", target->family);
  91                 return 0;
  92         }
  93         if (matchinfo->mode == XT_CONNMARK_RESTORE) {
  94                 if (strcmp(tablename, "mangle") != 0) {
  95                         printk(KERN_WARNING "CONNMARK: restore can only be "
  96                                "called from \"mangle\" table, not \"%s\"\n",
  97                                tablename);
  98                         return 0;
  99                 }
 100         }
 101         if (matchinfo->mark > 0xffffffff || matchinfo->mask > 0xffffffff) {
 102                 printk(KERN_WARNING "CONNMARK: Only supports 32bit mark\n");
 103                 return 0;
 104         }
 105         return 1;
 106 }
 107
 108 static void
 109 destroy(const struct xt_target *target, void *targinfo)
 110 {
 111         nf_ct_l3proto_module_put(target->family);
 112 }
 113
 114 #ifdef CONFIG_COMPAT
 115 struct compat_xt_connmark_target_info {
 116         compat_ulong_t  mark, mask;
 117         u_int8_t        mode;
 118         u_int8_t        __pad1;
 119         u_int16_t       __pad2;
 120 };
 121
 122 static void compat_from_user(void *dst, void *src)
 123 {
 124         struct compat_xt_connmark_target_info *cm = src;
 125         struct xt_connmark_target_info m = {
 126                 .mark   = cm->mark,
 127                 .mask   = cm->mask,
 128                 .mode   = cm->mode,
 129         };
 130         memcpy(dst, &m, sizeof(m));
 131 }
 132
 133 static int compat_to_user(void __user *dst, void *src)
 134 {
 135         struct xt_connmark_target_info *m = src;
 136         struct compat_xt_connmark_target_info cm = {
 137                 .mark   = m->mark,
 138                 .mask   = m->mask,
 139                 .mode   = m->mode,
 140         };
 141         return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
 142 }
 143 #endif /* CONFIG_COMPAT */
 144
 145 static struct xt_target xt_connmark_target[] = {
 146         {
 147                 .name           = "CONNMARK",
 148                 .family         = AF_INET,
 149                 .checkentry     = checkentry,
 150                 .destroy        = destroy,
 151                 .target         = target,
 152                 .targetsize     = sizeof(struct xt_connmark_target_info),
 153 #ifdef CONFIG_COMPAT
 154                 .compatsize     = sizeof(struct compat_xt_connmark_target_info),
 155                 .compat_from_user = compat_from_user,
 156                 .compat_to_user = compat_to_user,
 157 #endif
 158                 .me             = THIS_MODULE
 159         },
 160         {
 161                 .name           = "CONNMARK",
 162                 .family         = AF_INET6,
 163                 .checkentry     = checkentry,
 164                 .destroy        = destroy,
 165                 .target         = target,
 166                 .targetsize     = sizeof(struct xt_connmark_target_info),
 167                 .me             = THIS_MODULE
 168         },
 169 };
 170
 171 static int __init xt_connmark_init(void)
 172 {
 173         return xt_register_targets(xt_connmark_target,
 174                                    ARRAY_SIZE(xt_connmark_target));
 175 }
 176
 177 static void __exit xt_connmark_fini(void)
 178 {
 179         xt_unregister_targets(xt_connmark_target,
 180                               ARRAY_SIZE(xt_connmark_target));
 181 }
 182
 183 module_init(xt_connmark_init);
 184 module_exit(xt_connmark_fini);