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_compat.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        void *userinfo)
  43 {
  44         const struct xt_connmark_target_info *markinfo = targinfo;
  45         u_int32_t diff;
  46         u_int32_t nfmark;
  47         u_int32_t newmark;
  48         u_int32_t ctinfo;
  49         u_int32_t *ctmark = nf_ct_get_mark(*pskb, &ctinfo);
  50
  51         if (ctmark) {
  52             switch(markinfo->mode) {
  53             case XT_CONNMARK_SET:
  54                 newmark = (*ctmark & ~markinfo->mask) | markinfo->mark;
  55                 if (newmark != *ctmark)
  56                     *ctmark = newmark;
  57                 break;
  58             case XT_CONNMARK_SAVE:
  59                 newmark = (*ctmark & ~markinfo->mask) | ((*pskb)->nfmark & markinfo->mask);
  60                 if (*ctmark != newmark)
  61                     *ctmark = newmark;
  62                 break;
  63             case XT_CONNMARK_RESTORE:
  64                 nfmark = (*pskb)->nfmark;
  65                 diff = (*ctmark ^ nfmark) & markinfo->mask;
  66                 if (diff != 0)
  67                     (*pskb)->nfmark = nfmark ^ diff;
  68                 break;
  69             }
  70         }
  71
  72         return XT_CONTINUE;
  73 }
  74
  75 static int
  76 checkentry(const char *tablename,
  77            const void *entry,
  78            const struct xt_target *target,
  79            void *targinfo,
  80            unsigned int targinfosize,
  81            unsigned int hook_mask)
  82 {
  83         struct xt_connmark_target_info *matchinfo = targinfo;
  84
  85         if (matchinfo->mode == XT_CONNMARK_RESTORE) {
  86             if (strcmp(tablename, "mangle") != 0) {
  87                     printk(KERN_WARNING "CONNMARK: restore can only be called from \"mangle\" table, not \"%s\"\n", tablename);
  88                     return 0;
  89             }
  90         }
  91
  92         if (matchinfo->mark > 0xffffffff || matchinfo->mask > 0xffffffff) {
  93                 printk(KERN_WARNING "CONNMARK: Only supports 32bit mark\n");
  94                 return 0;
  95         }
  96
  97         return 1;
  98 }
  99
 100 static struct xt_target connmark_reg = {
 101         .name           = "CONNMARK",
 102         .target         = target,
 103         .targetsize     = sizeof(struct xt_connmark_target_info),
 104         .checkentry     = checkentry,
 105         .family         = AF_INET,
 106         .me             = THIS_MODULE
 107 };
 108
 109 static struct xt_target connmark6_reg = {
 110         .name           = "CONNMARK",
 111         .target         = target,
 112         .targetsize     = sizeof(struct xt_connmark_target_info),
 113         .checkentry     = checkentry,
 114         .family         = AF_INET6,
 115         .me             = THIS_MODULE
 116 };
 117
 118 static int __init xt_connmark_init(void)
 119 {
 120         int ret;
 121
 122         need_conntrack();
 123
 124         ret = xt_register_target(&connmark_reg);
 125         if (ret)
 126                 return ret;
 127
 128         ret = xt_register_target(&connmark6_reg);
 129         if (ret)
 130                 xt_unregister_target(&connmark_reg);
 131
 132         return ret;
 133 }
 134
 135 static void __exit xt_connmark_fini(void)
 136 {
 137         xt_unregister_target(&connmark_reg);
 138         xt_unregister_target(&connmark6_reg);
 139 }
 140
 141 module_init(xt_connmark_init);
 142 module_exit(xt_connmark_fini);