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 #include <linux/netfilter_ipv4/ipt_TOS.h>
  22
  23 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  24 MODULE_DESCRIPTION("Xtables: DSCP/TOS field modification");
  25 MODULE_LICENSE("GPL");
  26 MODULE_ALIAS("ipt_DSCP");
  27 MODULE_ALIAS("ip6t_DSCP");
  28 MODULE_ALIAS("ipt_TOS");
  29 MODULE_ALIAS("ip6t_TOS");
  30
  31 static unsigned int
  32 dscp_tg(struct sk_buff *skb, const struct net_device *in,
  33         const struct net_device *out, unsigned int hooknum,
  34         const struct xt_target *target, const void *targinfo)
  35 {
  36         const struct xt_DSCP_info *dinfo = targinfo;
  37         u_int8_t dscp = ipv4_get_dsfield(ip_hdr(skb)) >> XT_DSCP_SHIFT;
  38
  39         if (dscp != dinfo->dscp) {
  40                 if (!skb_make_writable(skb, sizeof(struct iphdr)))
  41                         return NF_DROP;
  42
  43                 ipv4_change_dsfield(ip_hdr(skb), (__u8)(~XT_DSCP_MASK),
  44                                     dinfo->dscp << XT_DSCP_SHIFT);
  45
  46         }
  47         return XT_CONTINUE;
  48 }
  49
  50 static unsigned int
  51 dscp_tg6(struct sk_buff *skb, const struct net_device *in,
  52          const struct net_device *out, unsigned int hooknum,
  53          const struct xt_target *target, const void *targinfo)
  54 {
  55         const struct xt_DSCP_info *dinfo = targinfo;
  56         u_int8_t dscp = ipv6_get_dsfield(ipv6_hdr(skb)) >> XT_DSCP_SHIFT;
  57
  58         if (dscp != dinfo->dscp) {
  59                 if (!skb_make_writable(skb, sizeof(struct ipv6hdr)))
  60                         return NF_DROP;
  61
  62                 ipv6_change_dsfield(ipv6_hdr(skb), (__u8)(~XT_DSCP_MASK),
  63                                     dinfo->dscp << XT_DSCP_SHIFT);
  64         }
  65         return XT_CONTINUE;
  66 }
  67
  68 static bool
  69 dscp_tg_check(const char *tablename, const void *e_void,
  70               const struct xt_target *target, void *targinfo,
  71               unsigned int hook_mask)
  72 {
  73         const u_int8_t dscp = ((struct xt_DSCP_info *)targinfo)->dscp;
  74
  75         if (dscp > XT_DSCP_MAX) {
  76                 printk(KERN_WARNING "DSCP: dscp %x out of range\n", dscp);
  77                 return false;
  78         }
  79         return true;
  80 }
  81
  82 static unsigned int
  83 tos_tg_v0(struct sk_buff *skb, const struct net_device *in,
  84           const struct net_device *out, unsigned int hooknum,
  85           const struct xt_target *target, const void *targinfo)
  86 {
  87         const struct ipt_tos_target_info *info = targinfo;
  88         struct iphdr *iph = ip_hdr(skb);
  89         u_int8_t oldtos;
  90
  91         if ((iph->tos & IPTOS_TOS_MASK) != info->tos) {
  92                 if (!skb_make_writable(skb, sizeof(struct iphdr)))
  93                         return NF_DROP;
  94
  95                 iph      = ip_hdr(skb);
  96                 oldtos   = iph->tos;
  97                 iph->tos = (iph->tos & IPTOS_PREC_MASK) | info->tos;
  98                 csum_replace2(&iph->check, htons(oldtos), htons(iph->tos));
  99         }
 100
 101         return XT_CONTINUE;
 102 }
 103
 104 static bool
 105 tos_tg_check_v0(const char *tablename, const void *e_void,
 106                 const struct xt_target *target, void *targinfo,
 107                 unsigned int hook_mask)
 108 {
 109         const u_int8_t tos = ((struct ipt_tos_target_info *)targinfo)->tos;
 110
 111         if (tos != IPTOS_LOWDELAY && tos != IPTOS_THROUGHPUT &&
 112             tos != IPTOS_RELIABILITY && tos != IPTOS_MINCOST &&
 113             tos != IPTOS_NORMALSVC) {
 114                 printk(KERN_WARNING "TOS: bad tos value %#x\n", tos);
 115                 return false;
 116         }
 117
 118         return true;
 119 }
 120
 121 static unsigned int
 122 tos_tg(struct sk_buff *skb, const struct net_device *in,
 123        const struct net_device *out, unsigned int hooknum,
 124        const struct xt_target *target, const void *targinfo)
 125 {
 126         const struct xt_tos_target_info *info = targinfo;
 127         struct iphdr *iph = ip_hdr(skb);
 128         u_int8_t orig, nv;
 129
 130         orig = ipv4_get_dsfield(iph);
 131         nv   = (orig & ~info->tos_mask) ^ info->tos_value;
 132
 133         if (orig != nv) {
 134                 if (!skb_make_writable(skb, sizeof(struct iphdr)))
 135                         return NF_DROP;
 136                 iph = ip_hdr(skb);
 137                 ipv4_change_dsfield(iph, 0, nv);
 138         }
 139
 140         return XT_CONTINUE;
 141 }
 142
 143 static unsigned int
 144 tos_tg6(struct sk_buff *skb, const struct net_device *in,
 145         const struct net_device *out, unsigned int hooknum,
 146         const struct xt_target *target, const void *targinfo)
 147 {
 148         const struct xt_tos_target_info *info = targinfo;
 149         struct ipv6hdr *iph = ipv6_hdr(skb);
 150         u_int8_t orig, nv;
 151
 152         orig = ipv6_get_dsfield(iph);
 153         nv   = (orig & info->tos_mask) ^ info->tos_value;
 154
 155         if (orig != nv) {
 156                 if (!skb_make_writable(skb, sizeof(struct iphdr)))
 157                         return NF_DROP;
 158                 iph = ipv6_hdr(skb);
 159                 ipv6_change_dsfield(iph, 0, nv);
 160         }
 161
 162         return XT_CONTINUE;
 163 }
 164
 165 static struct xt_target dscp_tg_reg[] __read_mostly = {
 166         {
 167                 .name           = "DSCP",
 168                 .family         = AF_INET,
 169                 .checkentry     = dscp_tg_check,
 170                 .target         = dscp_tg,
 171                 .targetsize     = sizeof(struct xt_DSCP_info),
 172                 .table          = "mangle",
 173                 .me             = THIS_MODULE,
 174         },
 175         {
 176                 .name           = "DSCP",
 177                 .family         = AF_INET6,
 178                 .checkentry     = dscp_tg_check,
 179                 .target         = dscp_tg6,
 180                 .targetsize     = sizeof(struct xt_DSCP_info),
 181                 .table          = "mangle",
 182                 .me             = THIS_MODULE,
 183         },
 184         {
 185                 .name           = "TOS",
 186                 .revision       = 0,
 187                 .family         = AF_INET,
 188                 .table          = "mangle",
 189                 .target         = tos_tg_v0,
 190                 .targetsize     = sizeof(struct ipt_tos_target_info),
 191                 .checkentry     = tos_tg_check_v0,
 192                 .me             = THIS_MODULE,
 193         },
 194         {
 195                 .name           = "TOS",
 196                 .revision       = 1,
 197                 .family         = AF_INET,
 198                 .table          = "mangle",
 199                 .target         = tos_tg,
 200                 .targetsize     = sizeof(struct xt_tos_target_info),
 201                 .me             = THIS_MODULE,
 202         },
 203         {
 204                 .name           = "TOS",
 205                 .revision       = 1,
 206                 .family         = AF_INET6,
 207                 .table          = "mangle",
 208                 .target         = tos_tg6,
 209                 .targetsize     = sizeof(struct xt_tos_target_info),
 210                 .me             = THIS_MODULE,
 211         },
 212 };
 213
 214 static int __init dscp_tg_init(void)
 215 {
 216         return xt_register_targets(dscp_tg_reg, ARRAY_SIZE(dscp_tg_reg));
 217 }
 218
 219 static void __exit dscp_tg_exit(void)
 220 {
 221         xt_unregister_targets(dscp_tg_reg, ARRAY_SIZE(dscp_tg_reg));
 222 }
 223
 224 module_init(dscp_tg_init);
 225 module_exit(dscp_tg_exit);