1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192 |
- // SPDX-License-Identifier: GPL-2.0-only
- /* module that allows mangling of the arp payload */
- #include <linux/module.h>
- #include <linux/netfilter.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 *skb, const struct xt_action_param *par)
- {
- const struct arpt_mangle *mangle = par->targinfo;
- const struct arphdr *arp;
- unsigned char *arpptr;
- int pln, hln;
- if (skb_ensure_writable(skb, skb->len))
- return NF_DROP;
- arp = arp_hdr(skb);
- arpptr = skb_network_header(skb) + 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 > skb_tail_pointer(skb)))
- 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 > skb_tail_pointer(skb)))
- 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 > skb_tail_pointer(skb)))
- 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 > skb_tail_pointer(skb)))
- return NF_DROP;
- memcpy(arpptr, &mangle->u_t.tgt_ip, pln);
- }
- return mangle->target;
- }
- static int checkentry(const struct xt_tgchk_param *par)
- {
- const struct arpt_mangle *mangle = par->targinfo;
- if (mangle->flags & ~ARPT_MANGLE_MASK ||
- !(mangle->flags & ARPT_MANGLE_MASK))
- return -EINVAL;
- if (mangle->target != NF_DROP && mangle->target != NF_ACCEPT &&
- mangle->target != XT_CONTINUE)
- return -EINVAL;
- return 0;
- }
- static struct xt_target arpt_mangle_reg __read_mostly = {
- .name = "mangle",
- .family = NFPROTO_ARP,
- .target = target,
- .targetsize = sizeof(struct arpt_mangle),
- .checkentry = checkentry,
- .me = THIS_MODULE,
- };
- static int __init arpt_mangle_init(void)
- {
- return xt_register_target(&arpt_mangle_reg);
- }
- static void __exit arpt_mangle_fini(void)
- {
- xt_unregister_target(&arpt_mangle_reg);
- }
- module_init(arpt_mangle_init);
- module_exit(arpt_mangle_fini);
|