net/ipv4/netfilter/ipt_TOS.c

   1 /* This is a module which is used for setting the TOS field of a packet. */
   2
   3 /* (C) 1999-2001 Paul `Rusty' Russell
   4  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   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
  11 #include <linux/module.h>
  12 #include <linux/skbuff.h>
  13 #include <linux/ip.h>
  14 #include <net/checksum.h>
  15
  16 #include <linux/netfilter_ipv4/ip_tables.h>
  17 #include <linux/netfilter_ipv4/ipt_TOS.h>
  18
  19 MODULE_LICENSE("GPL");
  20 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  21 MODULE_DESCRIPTION("iptables TOS mangling module");
  22
  23 static unsigned int
  24 target(struct sk_buff **pskb,
  25        const struct net_device *in,
  26        const struct net_device *out,
  27        unsigned int hooknum,
  28        const struct xt_target *target,
  29        const void *targinfo,
  30        void *userinfo)
  31 {
  32         const struct ipt_tos_target_info *tosinfo = targinfo;
  33
  34         if (((*pskb)->nh.iph->tos & IPTOS_TOS_MASK) != tosinfo->tos) {
  35                 u_int16_t diffs[2];
  36
  37                 if (!skb_make_writable(pskb, sizeof(struct iphdr)))
  38                         return NF_DROP;
  39
  40                 diffs[0] = htons((*pskb)->nh.iph->tos) ^ 0xFFFF;
  41                 (*pskb)->nh.iph->tos
  42                         = ((*pskb)->nh.iph->tos & IPTOS_PREC_MASK)
  43                         | tosinfo->tos;
  44                 diffs[1] = htons((*pskb)->nh.iph->tos);
  45                 (*pskb)->nh.iph->check
  46                         = csum_fold(csum_partial((char *)diffs,
  47                                                  sizeof(diffs),
  48                                                  (*pskb)->nh.iph->check
  49                                                  ^0xFFFF));
  50         }
  51         return IPT_CONTINUE;
  52 }
  53
  54 static int
  55 checkentry(const char *tablename,
  56            const void *e_void,
  57            const struct xt_target *target,
  58            void *targinfo,
  59            unsigned int targinfosize,
  60            unsigned int hook_mask)
  61 {
  62         const u_int8_t tos = ((struct ipt_tos_target_info *)targinfo)->tos;
  63
  64         if (tos != IPTOS_LOWDELAY
  65             && tos != IPTOS_THROUGHPUT
  66             && tos != IPTOS_RELIABILITY
  67             && tos != IPTOS_MINCOST
  68             && tos != IPTOS_NORMALSVC) {
  69                 printk(KERN_WARNING "TOS: bad tos value %#x\n", tos);
  70                 return 0;
  71         }
  72         return 1;
  73 }
  74
  75 static struct ipt_target ipt_tos_reg = {
  76         .name           = "TOS",
  77         .target         = target,
  78         .targetsize     = sizeof(struct ipt_tos_target_info),
  79         .table          = "mangle",
  80         .checkentry     = checkentry,
  81         .me             = THIS_MODULE,
  82 };
  83
  84 static int __init init(void)
  85 {
  86         return ipt_register_target(&ipt_tos_reg);
  87 }
  88
  89 static void __exit fini(void)
  90 {
  91         ipt_unregister_target(&ipt_tos_reg);
  92 }
  93
  94 module_init(init);
  95 module_exit(fini);