kernel/linux/net/ipv4/netfilter/ipt_FTOS.c

   1 /* Set TOS field in header to any value
   2  *
   3  * (C) 2000 by Matthew G. Marsh <mgm@paktronix.com>
   4  *
   5  * This software is distributed under GNU GPL v2, 1991
   6  *
   7  * ipt_FTOS.c borrowed heavily from ipt_TOS.c  11/09/2000
   8  *
   9  * Updated 3/4/02 - added in Rusty's skb_clone fix
  10  *                - added MODULE Political License
  11  *                - redid checksum routine somewhat
  12 */
  13
  14 #include <linux/module.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/ip.h>
  17 #include <net/checksum.h>
  18
  19 #include <linux/netfilter_ipv4/ip_tables.h>
  20 #include <linux/netfilter_ipv4/ipt_FTOS.h>
  21
  22 static unsigned int
  23 target(struct sk_buff **pskb,
  24        unsigned int hooknum,
  25        const struct net_device *in,
  26        const struct net_device *out,
  27        const void *targinfo,
  28        void *userinfo)
  29 {
  30         struct iphdr *iph = (*pskb)->nh.iph;
  31         const struct ipt_FTOS_info *ftosinfo = targinfo;
  32
  33         if ((iph->tos & IPTOS_TOS_MASK) != ftosinfo->ftos) {
  34                 u_int16_t diffs[2];
  35
  36                 /* raw socket (tcpdump) may have clone of incoming
  37                    skb: don't disturb it --RR */
  38                 if (skb_cloned(*pskb) && !(*pskb)->sk) {
  39                         struct sk_buff *nskb = skb_copy(*pskb, GFP_ATOMIC);
  40                         if (!nskb)
  41                                 return NF_DROP;
  42                         kfree_skb(*pskb);
  43                         *pskb = nskb;
  44                         iph = (*pskb)->nh.iph;
  45                 }
  46
  47                 diffs[0] = htons(iph->tos) ^ 0xFFFF;
  48                 iph->tos = ftosinfo->ftos;
  49                 diffs[1] = htons(iph->tos);
  50                 iph->check = csum_fold(csum_partial((char *)diffs,
  51                                                     sizeof(diffs),
  52                                                     iph->check^0xFFFF));
  53                 (*pskb)->nfcache |= NFC_ALTERED;
  54         }
  55         return IPT_CONTINUE;
  56 }
  57
  58 static int
  59 checkentry(const char *tablename,
  60            const struct ipt_entry *e,
  61            void *targinfo,
  62            unsigned int targinfosize,
  63            unsigned int hook_mask)
  64 {
  65         const u_int8_t ftos = ((struct ipt_FTOS_info *)targinfo)->ftos;
  66
  67         if (targinfosize != IPT_ALIGN(sizeof(struct ipt_FTOS_info))) {
  68                 printk(KERN_WARNING "FTOS: targinfosize %u != %Zu\n",
  69                        targinfosize,
  70                        IPT_ALIGN(sizeof(struct ipt_FTOS_info)));
  71                 return 0;
  72         }
  73
  74         if (strcmp(tablename, "mangle") != 0) {
  75                 printk(KERN_WARNING "FTOS: can only be called from \"mangle\" table, not \"%s\"\n", tablename);
  76                 return 0;
  77         }
  78
  79         return 1;
  80 }
  81
  82 #if defined(CONFIG_MIPS_BRCM)
  83 static struct ipt_target ipt_ftos_reg = {
  84         .name           = "FTOS",
  85         .target         = target,
  86         .checkentry     = checkentry,
  87         .me             = THIS_MODULE,
  88 };
  89 #else
  90 static struct ipt_target ipt_ftos_reg
  91 = { { NULL, NULL }, "FTOS", target, checkentry, NULL, THIS_MODULE };
  92 #endif
  93
  94 static int __init init(void)
  95 {
  96         if (ipt_register_target(&ipt_ftos_reg))
  97                 return -EINVAL;
  98
  99         return 0;
 100 }
 101
 102 static void __exit fini(void)
 103 {
 104         ipt_unregister_target(&ipt_ftos_reg);
 105 }
 106
 107 module_init(init);
 108 module_exit(fini);
 109 MODULE_LICENSE("GPL");