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/x_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 {
  31         const struct ipt_tos_target_info *tosinfo = targinfo;
  32         struct iphdr *iph = ip_hdr(*pskb);
  33
  34         if ((iph->tos & IPTOS_TOS_MASK) != tosinfo->tos) {
  35                 __u8 oldtos;
  36                 if (!skb_make_writable(pskb, sizeof(struct iphdr)))
  37                         return NF_DROP;
  38                 iph = ip_hdr(*pskb);
  39                 oldtos = iph->tos;
  40                 iph->tos = (iph->tos & IPTOS_PREC_MASK) | tosinfo->tos;
  41                 nf_csum_replace2(&iph->check, htons(oldtos), htons(iph->tos));
  42         }
  43         return XT_CONTINUE;
  44 }
  45
  46 static int
  47 checkentry(const char *tablename,
  48            const void *e_void,
  49            const struct xt_target *target,
  50            void *targinfo,
  51            unsigned int hook_mask)
  52 {
  53         const u_int8_t tos = ((struct ipt_tos_target_info *)targinfo)->tos;
  54
  55         if (tos != IPTOS_LOWDELAY
  56             && tos != IPTOS_THROUGHPUT
  57             && tos != IPTOS_RELIABILITY
  58             && tos != IPTOS_MINCOST
  59             && tos != IPTOS_NORMALSVC) {
  60                 printk(KERN_WARNING "TOS: bad tos value %#x\n", tos);
  61                 return 0;
  62         }
  63         return 1;
  64 }
  65
  66 static struct xt_target ipt_tos_reg = {
  67         .name           = "TOS",
  68         .family         = AF_INET,
  69         .target         = target,
  70         .targetsize     = sizeof(struct ipt_tos_target_info),
  71         .table          = "mangle",
  72         .checkentry     = checkentry,
  73         .me             = THIS_MODULE,
  74 };
  75
  76 static int __init ipt_tos_init(void)
  77 {
  78         return xt_register_target(&ipt_tos_reg);
  79 }
  80
  81 static void __exit ipt_tos_fini(void)
  82 {
  83         xt_unregister_target(&ipt_tos_reg);
  84 }
  85
  86 module_init(ipt_tos_init);
  87 module_exit(ipt_tos_fini);