2005-04-16 22:20:36 +00:00
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/* module that allows mangling of the arp payload */
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#include <linux/module.h>
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#include <linux/netfilter_arp/arpt_mangle.h>
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#include <net/sock.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
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MODULE_DESCRIPTION("arptables arp payload mangle target");
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static unsigned int
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2006-03-21 02:02:56 +00:00
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target(struct sk_buff **pskb,
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const struct net_device *in, const struct net_device *out,
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unsigned int hooknum, const struct xt_target *target,
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2006-08-22 07:35:47 +00:00
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const void *targinfo)
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2005-04-16 22:20:36 +00:00
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{
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const struct arpt_mangle *mangle = targinfo;
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struct arphdr *arp;
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unsigned char *arpptr;
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int pln, hln;
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if (skb_shared(*pskb) || skb_cloned(*pskb)) {
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struct sk_buff *nskb;
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nskb = skb_copy(*pskb, GFP_ATOMIC);
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if (!nskb)
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return NF_DROP;
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if ((*pskb)->sk)
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skb_set_owner_w(nskb, (*pskb)->sk);
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kfree_skb(*pskb);
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*pskb = nskb;
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}
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arp = (*pskb)->nh.arph;
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arpptr = (*pskb)->nh.raw + sizeof(*arp);
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pln = arp->ar_pln;
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hln = arp->ar_hln;
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/* We assume that pln and hln were checked in the match */
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if (mangle->flags & ARPT_MANGLE_SDEV) {
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if (ARPT_DEV_ADDR_LEN_MAX < hln ||
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(arpptr + hln > (**pskb).tail))
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return NF_DROP;
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memcpy(arpptr, mangle->src_devaddr, hln);
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}
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arpptr += hln;
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if (mangle->flags & ARPT_MANGLE_SIP) {
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if (ARPT_MANGLE_ADDR_LEN_MAX < pln ||
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(arpptr + pln > (**pskb).tail))
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return NF_DROP;
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memcpy(arpptr, &mangle->u_s.src_ip, pln);
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}
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arpptr += pln;
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if (mangle->flags & ARPT_MANGLE_TDEV) {
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if (ARPT_DEV_ADDR_LEN_MAX < hln ||
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(arpptr + hln > (**pskb).tail))
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return NF_DROP;
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memcpy(arpptr, mangle->tgt_devaddr, hln);
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}
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arpptr += hln;
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if (mangle->flags & ARPT_MANGLE_TIP) {
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if (ARPT_MANGLE_ADDR_LEN_MAX < pln ||
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(arpptr + pln > (**pskb).tail))
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return NF_DROP;
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memcpy(arpptr, &mangle->u_t.tgt_ip, pln);
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}
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return mangle->target;
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}
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static int
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2006-03-21 02:02:56 +00:00
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checkentry(const char *tablename, const void *e, const struct xt_target *target,
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2006-08-22 07:36:37 +00:00
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void *targinfo, unsigned int hook_mask)
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2005-04-16 22:20:36 +00:00
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{
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const struct arpt_mangle *mangle = targinfo;
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if (mangle->flags & ~ARPT_MANGLE_MASK ||
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!(mangle->flags & ARPT_MANGLE_MASK))
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return 0;
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if (mangle->target != NF_DROP && mangle->target != NF_ACCEPT &&
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mangle->target != ARPT_CONTINUE)
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return 0;
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return 1;
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}
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2006-03-21 02:01:28 +00:00
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static struct arpt_target arpt_mangle_reg = {
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.name = "mangle",
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.target = target,
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.targetsize = sizeof(struct arpt_mangle),
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.checkentry = checkentry,
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.me = THIS_MODULE,
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2005-04-16 22:20:36 +00:00
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};
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2006-03-29 00:37:06 +00:00
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static int __init arpt_mangle_init(void)
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2005-04-16 22:20:36 +00:00
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{
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if (arpt_register_target(&arpt_mangle_reg))
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return -EINVAL;
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return 0;
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}
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2006-03-29 00:37:06 +00:00
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static void __exit arpt_mangle_fini(void)
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2005-04-16 22:20:36 +00:00
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{
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arpt_unregister_target(&arpt_mangle_reg);
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}
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2006-03-29 00:37:06 +00:00
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module_init(arpt_mangle_init);
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module_exit(arpt_mangle_fini);
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