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 void *targinfo,
  29        void *userinfo)
  30 {
  31         const struct ipt_tos_target_info *tosinfo = targinfo;
  32
  33         if (((*pskb)->nh.iph->tos & IPTOS_TOS_MASK) != tosinfo->tos) {
  34                 u_int16_t diffs[2];
  35
  36                 if (!skb_ip_make_writable(pskb, sizeof(struct iphdr)))
  37                         return NF_DROP;
  38
  39                 diffs[0] = htons((*pskb)->nh.iph->tos) ^ 0xFFFF;
  40                 (*pskb)->nh.iph->tos
  41                         = ((*pskb)->nh.iph->tos & IPTOS_PREC_MASK)
  42                         | tosinfo->tos;
  43                 diffs[1] = htons((*pskb)->nh.iph->tos);
  44                 (*pskb)->nh.iph->check
  45                         = csum_fold(csum_partial((char *)diffs,
  46                                                  sizeof(diffs),
  47                                                  (*pskb)->nh.iph->check
  48                                                  ^0xFFFF));
  49                 (*pskb)->nfcache |= NFC_ALTERED;
  50         }
  51         return IPT_CONTINUE;
  52 }
  53
  54 static int
  55 checkentry(const char *tablename,
  56            const struct ipt_entry *e,
  57            void *targinfo,
  58            unsigned int targinfosize,
  59            unsigned int hook_mask)
  60 {
  61         const u_int8_t tos = ((struct ipt_tos_target_info *)targinfo)->tos;
  62
  63         if (targinfosize != IPT_ALIGN(sizeof(struct ipt_tos_target_info))) {
  64                 printk(KERN_WARNING "TOS: targinfosize %u != %Zu\n",
  65                        targinfosize,
  66                        IPT_ALIGN(sizeof(struct ipt_tos_target_info)));
  67                 return 0;
  68         }
  69
  70         if (strcmp(tablename, "mangle") != 0) {
  71                 printk(KERN_WARNING "TOS: can only be called from \"mangle\" table, not \"%s\"\n", tablename);
  72                 return 0;
  73         }
  74
  75         if (tos != IPTOS_LOWDELAY
  76             && tos != IPTOS_THROUGHPUT
  77             && tos != IPTOS_RELIABILITY
  78             && tos != IPTOS_MINCOST
  79             && tos != IPTOS_NORMALSVC) {
  80                 printk(KERN_WARNING "TOS: bad tos value %#x\n", tos);
  81                 return 0;
  82         }
  83
  84         return 1;
  85 }
  86
  87 static struct ipt_target ipt_tos_reg = {
  88         .name           = "TOS",
  89         .target         = target,
  90         .checkentry     = checkentry,
  91         .me             = THIS_MODULE,
  92 };
  93
  94 static int __init init(void)
  95 {
  96         return ipt_register_target(&ipt_tos_reg);
  97 }
  98
  99 static void __exit fini(void)
 100 {
 101         ipt_unregister_target(&ipt_tos_reg);
 102 }
 103
 104 module_init(init);
 105 module_exit(fini);