net/netfilter/xt_DSCP.c

   1 /* x_tables module for setting the IPv4/IPv6 DSCP field, Version 1.8
   2  *
   3  * (C) 2002 by Harald Welte <laforge@netfilter.org>
   4  * based on ipt_FTOS.c (C) 2000 by Matthew G. Marsh <mgm@paktronix.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * See RFC2474 for a description of the DSCP field within the IP Header.
  11 */
  12
  13 #include <linux/module.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/ip.h>
  16 #include <linux/ipv6.h>
  17 #include <net/dsfield.h>
  18
  19 #include <linux/netfilter/x_tables.h>
  20 #include <linux/netfilter/xt_DSCP.h>
  21
  22 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  23 MODULE_DESCRIPTION("x_tables DSCP modification module");
  24 MODULE_LICENSE("GPL");
  25 MODULE_ALIAS("ipt_DSCP");
  26 MODULE_ALIAS("ip6t_DSCP");
  27
  28 static unsigned int target(struct sk_buff *skb,
  29                            const struct net_device *in,
  30                            const struct net_device *out,
  31                            unsigned int hooknum,
  32                            const struct xt_target *target,
  33                            const void *targinfo)
  34 {
  35         const struct xt_DSCP_info *dinfo = targinfo;
  36         u_int8_t dscp = ipv4_get_dsfield(ip_hdr(skb)) >> XT_DSCP_SHIFT;
  37
  38         if (dscp != dinfo->dscp) {
  39                 if (!skb_make_writable(skb, sizeof(struct iphdr)))
  40                         return NF_DROP;
  41
  42                 ipv4_change_dsfield(ip_hdr(skb), (__u8)(~XT_DSCP_MASK),
  43                                     dinfo->dscp << XT_DSCP_SHIFT);
  44
  45         }
  46         return XT_CONTINUE;
  47 }
  48
  49 static unsigned int target6(struct sk_buff *skb,
  50                             const struct net_device *in,
  51                             const struct net_device *out,
  52                             unsigned int hooknum,
  53                             const struct xt_target *target,
  54                             const void *targinfo)
  55 {
  56         const struct xt_DSCP_info *dinfo = targinfo;
  57         u_int8_t dscp = ipv6_get_dsfield(ipv6_hdr(skb)) >> XT_DSCP_SHIFT;
  58
  59         if (dscp != dinfo->dscp) {
  60                 if (!skb_make_writable(skb, sizeof(struct ipv6hdr)))
  61                         return NF_DROP;
  62
  63                 ipv6_change_dsfield(ipv6_hdr(skb), (__u8)(~XT_DSCP_MASK),
  64                                     dinfo->dscp << XT_DSCP_SHIFT);
  65         }
  66         return XT_CONTINUE;
  67 }
  68
  69 static bool checkentry(const char *tablename,
  70                        const void *e_void,
  71                        const struct xt_target *target,
  72                        void *targinfo,
  73                        unsigned int hook_mask)
  74 {
  75         const u_int8_t dscp = ((struct xt_DSCP_info *)targinfo)->dscp;
  76
  77         if (dscp > XT_DSCP_MAX) {
  78                 printk(KERN_WARNING "DSCP: dscp %x out of range\n", dscp);
  79                 return false;
  80         }
  81         return true;
  82 }
  83
  84 static struct xt_target xt_dscp_target[] __read_mostly = {
  85         {
  86                 .name           = "DSCP",
  87                 .family         = AF_INET,
  88                 .checkentry     = checkentry,
  89                 .target         = target,
  90                 .targetsize     = sizeof(struct xt_DSCP_info),
  91                 .table          = "mangle",
  92                 .me             = THIS_MODULE,
  93         },
  94         {
  95                 .name           = "DSCP",
  96                 .family         = AF_INET6,
  97                 .checkentry     = checkentry,
  98                 .target         = target6,
  99                 .targetsize     = sizeof(struct xt_DSCP_info),
 100                 .table          = "mangle",
 101                 .me             = THIS_MODULE,
 102         },
 103 };
 104
 105 static int __init xt_dscp_target_init(void)
 106 {
 107         return xt_register_targets(xt_dscp_target, ARRAY_SIZE(xt_dscp_target));
 108 }
 109
 110 static void __exit xt_dscp_target_fini(void)
 111 {
 112         xt_unregister_targets(xt_dscp_target, ARRAY_SIZE(xt_dscp_target));
 113 }
 114
 115 module_init(xt_dscp_target_init);
 116 module_exit(xt_dscp_target_fini);