net/ipv4/netfilter/arpt_mangle.c

   1 /* module that allows mangling of the arp payload */
   2 #include <linux/module.h>
   3 #include <linux/netfilter.h>
   4 #include <linux/netfilter_arp/arpt_mangle.h>
   5 #include <net/sock.h>
   6
   7 MODULE_LICENSE("GPL");
   8 MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
   9 MODULE_DESCRIPTION("arptables arp payload mangle target");
  10
  11 static unsigned int
  12 target(struct sk_buff *skb,
  13        const struct net_device *in, const struct net_device *out,
  14        unsigned int hooknum, const struct xt_target *target,
  15        const void *targinfo)
  16 {
  17         const struct arpt_mangle *mangle = targinfo;
  18         struct arphdr *arp;
  19         unsigned char *arpptr;
  20         int pln, hln;
  21
  22 <<<<<<< HEAD:net/ipv4/netfilter/arpt_mangle.c
  23         if (skb_make_writable(skb, skb->len))
  24 =======
  25         if (!skb_make_writable(skb, skb->len))
  26 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:net/ipv4/netfilter/arpt_mangle.c
  27                 return NF_DROP;
  28
  29         arp = arp_hdr(skb);
  30         arpptr = skb_network_header(skb) + sizeof(*arp);
  31         pln = arp->ar_pln;
  32         hln = arp->ar_hln;
  33         /* We assume that pln and hln were checked in the match */
  34         if (mangle->flags & ARPT_MANGLE_SDEV) {
  35                 if (ARPT_DEV_ADDR_LEN_MAX < hln ||
  36                    (arpptr + hln > skb_tail_pointer(skb)))
  37                         return NF_DROP;
  38                 memcpy(arpptr, mangle->src_devaddr, hln);
  39         }
  40         arpptr += hln;
  41         if (mangle->flags & ARPT_MANGLE_SIP) {
  42                 if (ARPT_MANGLE_ADDR_LEN_MAX < pln ||
  43                    (arpptr + pln > skb_tail_pointer(skb)))
  44                         return NF_DROP;
  45                 memcpy(arpptr, &mangle->u_s.src_ip, pln);
  46         }
  47         arpptr += pln;
  48         if (mangle->flags & ARPT_MANGLE_TDEV) {
  49                 if (ARPT_DEV_ADDR_LEN_MAX < hln ||
  50                    (arpptr + hln > skb_tail_pointer(skb)))
  51                         return NF_DROP;
  52                 memcpy(arpptr, mangle->tgt_devaddr, hln);
  53         }
  54         arpptr += hln;
  55         if (mangle->flags & ARPT_MANGLE_TIP) {
  56                 if (ARPT_MANGLE_ADDR_LEN_MAX < pln ||
  57                    (arpptr + pln > skb_tail_pointer(skb)))
  58                         return NF_DROP;
  59                 memcpy(arpptr, &mangle->u_t.tgt_ip, pln);
  60         }
  61         return mangle->target;
  62 }
  63
  64 static bool
  65 checkentry(const char *tablename, const void *e, const struct xt_target *target,
  66            void *targinfo, unsigned int hook_mask)
  67 {
  68         const struct arpt_mangle *mangle = targinfo;
  69
  70         if (mangle->flags & ~ARPT_MANGLE_MASK ||
  71             !(mangle->flags & ARPT_MANGLE_MASK))
  72                 return false;
  73
  74         if (mangle->target != NF_DROP && mangle->target != NF_ACCEPT &&
  75            mangle->target != ARPT_CONTINUE)
  76                 return false;
  77         return true;
  78 }
  79
  80 static struct arpt_target arpt_mangle_reg __read_mostly = {
  81         .name           = "mangle",
  82         .target         = target,
  83         .targetsize     = sizeof(struct arpt_mangle),
  84         .checkentry     = checkentry,
  85         .me             = THIS_MODULE,
  86 };
  87
  88 static int __init arpt_mangle_init(void)
  89 {
  90         if (arpt_register_target(&arpt_mangle_reg))
  91                 return -EINVAL;
  92
  93         return 0;
  94 }
  95
  96 static void __exit arpt_mangle_fini(void)
  97 {
  98         arpt_unregister_target(&arpt_mangle_reg);
  99 }
 100
 101 module_init(arpt_mangle_init);
 102 module_exit(arpt_mangle_fini);