net/ipv4/netfilter/ipt_DSCP.c

   1 /* iptables module for setting the IPv4 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  * ipt_DSCP.c,v 1.8 2002/08/06 18:41:57 laforge Exp
  13 */
  14
  15 #include <linux/module.h>
  16 #include <linux/skbuff.h>
  17 #include <linux/ip.h>
  18 #include <net/checksum.h>
  19
  20 #include <linux/netfilter_ipv4/ip_tables.h>
  21 #include <linux/netfilter_ipv4/ipt_DSCP.h>
  22
  23 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  24 MODULE_DESCRIPTION("iptables DSCP modification module");
  25 MODULE_LICENSE("GPL");
  26
  27 static unsigned int
  28 target(struct sk_buff **pskb,
  29        const struct net_device *in,
  30        const struct net_device *out,
  31        unsigned int hooknum,
  32        const void *targinfo,
  33        void *userinfo)
  34 {
  35         const struct ipt_DSCP_info *dinfo = targinfo;
  36         u_int8_t sh_dscp = ((dinfo->dscp << IPT_DSCP_SHIFT) & IPT_DSCP_MASK);
  37
  38
  39         if (((*pskb)->nh.iph->tos & IPT_DSCP_MASK) != sh_dscp) {
  40                 u_int16_t diffs[2];
  41
  42                 if (!skb_ip_make_writable(pskb, sizeof(struct iphdr)))
  43                         return NF_DROP;
  44
  45                 diffs[0] = htons((*pskb)->nh.iph->tos) ^ 0xFFFF;
  46                 (*pskb)->nh.iph->tos = ((*pskb)->nh.iph->tos & ~IPT_DSCP_MASK)
  47                         | sh_dscp;
  48                 diffs[1] = htons((*pskb)->nh.iph->tos);
  49                 (*pskb)->nh.iph->check
  50                         = csum_fold(csum_partial((char *)diffs,
  51                                                  sizeof(diffs),
  52                                                  (*pskb)->nh.iph->check
  53                                                  ^ 0xFFFF));
  54                 (*pskb)->nfcache |= NFC_ALTERED;
  55         }
  56         return IPT_CONTINUE;
  57 }
  58
  59 static int
  60 checkentry(const char *tablename,
  61            const struct ipt_entry *e,
  62            void *targinfo,
  63            unsigned int targinfosize,
  64            unsigned int hook_mask)
  65 {
  66         const u_int8_t dscp = ((struct ipt_DSCP_info *)targinfo)->dscp;
  67
  68         if (targinfosize != IPT_ALIGN(sizeof(struct ipt_DSCP_info))) {
  69                 printk(KERN_WARNING "DSCP: targinfosize %u != %Zu\n",
  70                        targinfosize,
  71                        IPT_ALIGN(sizeof(struct ipt_DSCP_info)));
  72                 return 0;
  73         }
  74
  75         if (strcmp(tablename, "mangle") != 0) {
  76                 printk(KERN_WARNING "DSCP: can only be called from \"mangle\" table, not \"%s\"\n", tablename);
  77                 return 0;
  78         }
  79
  80         if ((dscp > IPT_DSCP_MAX)) {
  81                 printk(KERN_WARNING "DSCP: dscp %x out of range\n", dscp);
  82                 return 0;
  83         }
  84
  85         return 1;
  86 }
  87
  88 static struct ipt_target ipt_dscp_reg = {
  89         .name           = "DSCP",
  90         .target         = target,
  91         .checkentry     = checkentry,
  92         .me             = THIS_MODULE,
  93 };
  94
  95 static int __init init(void)
  96 {
  97         return ipt_register_target(&ipt_dscp_reg);
  98 }
  99
 100 static void __exit fini(void)
 101 {
 102         ipt_unregister_target(&ipt_dscp_reg);
 103 }
 104
 105 module_init(init);
 106 module_exit(fini);