net/ipv4/netfilter/ipt_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
  30 #include <linux/netfilter_ipv4/ip_tables.h>
  31 #include <linux/netfilter_ipv4/ipt_CONNMARK.h>
  32 #include <linux/netfilter_ipv4/ip_conntrack.h>
  33
  34 static unsigned int
  35 target(struct sk_buff **pskb,
  36        const struct net_device *in,
  37        const struct net_device *out,
  38        unsigned int hooknum,
  39        const void *targinfo,
  40        void *userinfo)
  41 {
  42         const struct ipt_connmark_target_info *markinfo = targinfo;
  43         unsigned long diff;
  44         unsigned long nfmark;
  45         unsigned long newmark;
  46
  47         enum ip_conntrack_info ctinfo;
  48         struct ip_conntrack *ct = ip_conntrack_get((*pskb), &ctinfo);
  49         if (ct) {
  50             switch(markinfo->mode) {
  51             case IPT_CONNMARK_SET:
  52                 newmark = (ct->mark & ~markinfo->mask) | markinfo->mark;
  53                 if (newmark != ct->mark)
  54                     ct->mark = newmark;
  55                 break;
  56             case IPT_CONNMARK_SAVE:
  57                 newmark = (ct->mark & ~markinfo->mask) | ((*pskb)->nfmark & markinfo->mask);
  58                 if (ct->mark != newmark)
  59                     ct->mark = newmark;
  60                 break;
  61             case IPT_CONNMARK_RESTORE:
  62                 nfmark = (*pskb)->nfmark;
  63                 diff = (ct->mark ^ nfmark) & markinfo->mask;
  64                 if (diff != 0) {
  65                     (*pskb)->nfmark = nfmark ^ diff;
  66                     (*pskb)->nfcache |= NFC_ALTERED;
  67                 }
  68                 break;
  69             }
  70         }
  71
  72         return IPT_CONTINUE;
  73 }
  74
  75 static int
  76 checkentry(const char *tablename,
  77            const struct ipt_entry *e,
  78            void *targinfo,
  79            unsigned int targinfosize,
  80            unsigned int hook_mask)
  81 {
  82         struct ipt_connmark_target_info *matchinfo = targinfo;
  83         if (targinfosize != IPT_ALIGN(sizeof(struct ipt_connmark_target_info))) {
  84                 printk(KERN_WARNING "CONNMARK: targinfosize %u != %Zu\n",
  85                        targinfosize,
  86                        IPT_ALIGN(sizeof(struct ipt_connmark_target_info)));
  87                 return 0;
  88         }
  89
  90         if (matchinfo->mode == IPT_CONNMARK_RESTORE) {
  91             if (strcmp(tablename, "mangle") != 0) {
  92                     printk(KERN_WARNING "CONNMARK: restore can only be called from \"mangle\" table, not \"%s\"\n", tablename);
  93                     return 0;
  94             }
  95         }
  96
  97         return 1;
  98 }
  99
 100 static struct ipt_target ipt_connmark_reg = {
 101         .name = "CONNMARK",
 102         .target = &target,
 103         .checkentry = &checkentry,
 104         .me = THIS_MODULE
 105 };
 106
 107 static int __init init(void)
 108 {
 109         return ipt_register_target(&ipt_connmark_reg);
 110 }
 111
 112 static void __exit fini(void)
 113 {
 114         ipt_unregister_target(&ipt_connmark_reg);
 115 }
 116
 117 module_init(init);
 118 module_exit(fini);