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path: root/net/ipv4/netfilter/arpt_mangle.c
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Diffstat (limited to 'net/ipv4/netfilter/arpt_mangle.c')
-rw-r--r--net/ipv4/netfilter/arpt_mangle.c104
1 files changed, 104 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/arpt_mangle.c b/net/ipv4/netfilter/arpt_mangle.c
new file mode 100644
index 00000000000..3e592ec8648
--- /dev/null
+++ b/net/ipv4/netfilter/arpt_mangle.c
@@ -0,0 +1,104 @@
+/* module that allows mangling of the arp payload */
+#include <linux/module.h>
+#include <linux/netfilter_arp/arpt_mangle.h>
+#include <net/sock.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
+MODULE_DESCRIPTION("arptables arp payload mangle target");
+
+static unsigned int
+target(struct sk_buff **pskb, unsigned int hooknum, const struct net_device *in,
+ const struct net_device *out, const void *targinfo, void *userinfo)
+{
+ const struct arpt_mangle *mangle = targinfo;
+ struct arphdr *arp;
+ unsigned char *arpptr;
+ int pln, hln;
+
+ if (skb_shared(*pskb) || skb_cloned(*pskb)) {
+ struct sk_buff *nskb;
+
+ nskb = skb_copy(*pskb, GFP_ATOMIC);
+ if (!nskb)
+ return NF_DROP;
+ if ((*pskb)->sk)
+ skb_set_owner_w(nskb, (*pskb)->sk);
+ kfree_skb(*pskb);
+ *pskb = nskb;
+ }
+
+ arp = (*pskb)->nh.arph;
+ arpptr = (*pskb)->nh.raw + sizeof(*arp);
+ pln = arp->ar_pln;
+ hln = arp->ar_hln;
+ /* We assume that pln and hln were checked in the match */
+ if (mangle->flags & ARPT_MANGLE_SDEV) {
+ if (ARPT_DEV_ADDR_LEN_MAX < hln ||
+ (arpptr + hln > (**pskb).tail))
+ return NF_DROP;
+ memcpy(arpptr, mangle->src_devaddr, hln);
+ }
+ arpptr += hln;
+ if (mangle->flags & ARPT_MANGLE_SIP) {
+ if (ARPT_MANGLE_ADDR_LEN_MAX < pln ||
+ (arpptr + pln > (**pskb).tail))
+ return NF_DROP;
+ memcpy(arpptr, &mangle->u_s.src_ip, pln);
+ }
+ arpptr += pln;
+ if (mangle->flags & ARPT_MANGLE_TDEV) {
+ if (ARPT_DEV_ADDR_LEN_MAX < hln ||
+ (arpptr + hln > (**pskb).tail))
+ return NF_DROP;
+ memcpy(arpptr, mangle->tgt_devaddr, hln);
+ }
+ arpptr += hln;
+ if (mangle->flags & ARPT_MANGLE_TIP) {
+ if (ARPT_MANGLE_ADDR_LEN_MAX < pln ||
+ (arpptr + pln > (**pskb).tail))
+ return NF_DROP;
+ memcpy(arpptr, &mangle->u_t.tgt_ip, pln);
+ }
+ return mangle->target;
+}
+
+static int
+checkentry(const char *tablename, const struct arpt_entry *e, void *targinfo,
+ unsigned int targinfosize, unsigned int hook_mask)
+{
+ const struct arpt_mangle *mangle = targinfo;
+
+ if (mangle->flags & ~ARPT_MANGLE_MASK ||
+ !(mangle->flags & ARPT_MANGLE_MASK))
+ return 0;
+
+ if (mangle->target != NF_DROP && mangle->target != NF_ACCEPT &&
+ mangle->target != ARPT_CONTINUE)
+ return 0;
+ return 1;
+}
+
+static struct arpt_target arpt_mangle_reg
+= {
+ .name = "mangle",
+ .target = target,
+ .checkentry = checkentry,
+ .me = THIS_MODULE,
+};
+
+static int __init init(void)
+{
+ if (arpt_register_target(&arpt_mangle_reg))
+ return -EINVAL;
+
+ return 0;
+}
+
+static void __exit fini(void)
+{
+ arpt_unregister_target(&arpt_mangle_reg);
+}
+
+module_init(init);
+module_exit(fini);