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 void *targinfo,
  41        void *userinfo)
  42 {
  43         const struct xt_connmark_target_info *markinfo = targinfo;
  44         u_int32_t diff;
  45         u_int32_t nfmark;
  46         u_int32_t newmark;
  47         u_int32_t ctinfo;
  48         u_int32_t *ctmark = nf_ct_get_mark(*pskb, &ctinfo);
  49
  50         if (ctmark) {
  51             switch(markinfo->mode) {
  52             case XT_CONNMARK_SET:
  53                 newmark = (*ctmark & ~markinfo->mask) | markinfo->mark;
  54                 if (newmark != *ctmark)
  55                     *ctmark = newmark;
  56                 break;
  57             case XT_CONNMARK_SAVE:
  58                 newmark = (*ctmark & ~markinfo->mask) | ((*pskb)->nfmark & markinfo->mask);
  59                 if (*ctmark != newmark)
  60                     *ctmark = newmark;
  61                 break;
  62             case XT_CONNMARK_RESTORE:
  63                 nfmark = (*pskb)->nfmark;
  64                 diff = (*ctmark ^ nfmark) & markinfo->mask;
  65                 if (diff != 0)
  66                     (*pskb)->nfmark = nfmark ^ diff;
  67                 break;
  68             }
  69         }
  70
  71         return XT_CONTINUE;
  72 }
  73
  74 static int
  75 checkentry(const char *tablename,
  76            const void *entry,
  77            void *targinfo,
  78            unsigned int targinfosize,
  79            unsigned int hook_mask)
  80 {
  81         struct xt_connmark_target_info *matchinfo = targinfo;
  82         if (targinfosize != XT_ALIGN(sizeof(struct xt_connmark_target_info))) {
  83                 printk(KERN_WARNING "CONNMARK: targinfosize %u != %Zu\n",
  84                        targinfosize,
  85                        XT_ALIGN(sizeof(struct xt_connmark_target_info)));
  86                 return 0;
  87         }
  88
  89         if (matchinfo->mode == XT_CONNMARK_RESTORE) {
  90             if (strcmp(tablename, "mangle") != 0) {
  91                     printk(KERN_WARNING "CONNMARK: restore can only be called from \"mangle\" table, not \"%s\"\n", tablename);
  92                     return 0;
  93             }
  94         }
  95
  96         if (matchinfo->mark > 0xffffffff || matchinfo->mask > 0xffffffff) {
  97                 printk(KERN_WARNING "CONNMARK: Only supports 32bit mark\n");
  98                 return 0;
  99         }
 100
 101         return 1;
 102 }
 103
 104 static struct xt_target connmark_reg = {
 105         .name = "CONNMARK",
 106         .target = &target,
 107         .checkentry = &checkentry,
 108         .me = THIS_MODULE
 109 };
 110 static struct xt_target connmark6_reg = {
 111         .name = "CONNMARK",
 112         .target = &target,
 113         .checkentry = &checkentry,
 114         .me = THIS_MODULE
 115 };
 116
 117 static int __init init(void)
 118 {
 119         int ret;
 120
 121         need_conntrack();
 122
 123         ret = xt_register_target(AF_INET, &connmark_reg);
 124         if (ret)
 125                 return ret;
 126
 127         ret = xt_register_target(AF_INET6, &connmark6_reg);
 128         if (ret)
 129                 xt_unregister_target(AF_INET, &connmark_reg);
 130
 131         return ret;
 132 }
 133
 134 static void __exit fini(void)
 135 {
 136         xt_unregister_target(AF_INET, &connmark_reg);
 137         xt_unregister_target(AF_INET6, &connmark6_reg);
 138 }
 139
 140 module_init(init);
 141 module_exit(fini);