109c434b8SThomas Gleixner // SPDX-License-Identifier: GPL-2.0-only
21da177e4SLinus Torvalds /*
31da177e4SLinus Torvalds * ebt_arpreply
41da177e4SLinus Torvalds *
51da177e4SLinus Torvalds * Authors:
61da177e4SLinus Torvalds * Grzegorz Borowiak <grzes@gnu.univ.gda.pl>
71da177e4SLinus Torvalds * Bart De Schuymer <bdschuym@pandora.be>
81da177e4SLinus Torvalds *
91da177e4SLinus Torvalds * August, 2003
101da177e4SLinus Torvalds *
111da177e4SLinus Torvalds */
121da177e4SLinus Torvalds #include <linux/if_arp.h>
131da177e4SLinus Torvalds #include <net/arp.h>
141da177e4SLinus Torvalds #include <linux/module.h>
1518219d3fSJan Engelhardt #include <linux/netfilter/x_tables.h>
1618219d3fSJan Engelhardt #include <linux/netfilter_bridge/ebtables.h>
1718219d3fSJan Engelhardt #include <linux/netfilter_bridge/ebt_arpreply.h>
181da177e4SLinus Torvalds
192d06d4a5SJan Engelhardt static unsigned int
ebt_arpreply_tg(struct sk_buff * skb,const struct xt_action_param * par)204b560b44SJan Engelhardt ebt_arpreply_tg(struct sk_buff *skb, const struct xt_action_param *par)
211da177e4SLinus Torvalds {
227eb35586SJan Engelhardt const struct ebt_arpreply_info *info = par->targinfo;
23abfdf1c4SJan Engelhardt const __be32 *siptr, *diptr;
24abfdf1c4SJan Engelhardt __be32 _sip, _dip;
25abfdf1c4SJan Engelhardt const struct arphdr *ap;
26abfdf1c4SJan Engelhardt struct arphdr _ah;
27abfdf1c4SJan Engelhardt const unsigned char *shp;
28abfdf1c4SJan Engelhardt unsigned char _sha[ETH_ALEN];
291da177e4SLinus Torvalds
301da177e4SLinus Torvalds ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah);
311da177e4SLinus Torvalds if (ap == NULL)
321da177e4SLinus Torvalds return EBT_DROP;
331da177e4SLinus Torvalds
341da177e4SLinus Torvalds if (ap->ar_op != htons(ARPOP_REQUEST) ||
351da177e4SLinus Torvalds ap->ar_hln != ETH_ALEN ||
361da177e4SLinus Torvalds ap->ar_pro != htons(ETH_P_IP) ||
371da177e4SLinus Torvalds ap->ar_pln != 4)
381da177e4SLinus Torvalds return EBT_CONTINUE;
391da177e4SLinus Torvalds
401da177e4SLinus Torvalds shp = skb_header_pointer(skb, sizeof(_ah), ETH_ALEN, &_sha);
411da177e4SLinus Torvalds if (shp == NULL)
421da177e4SLinus Torvalds return EBT_DROP;
431da177e4SLinus Torvalds
441da177e4SLinus Torvalds siptr = skb_header_pointer(skb, sizeof(_ah) + ETH_ALEN,
451da177e4SLinus Torvalds sizeof(_sip), &_sip);
461da177e4SLinus Torvalds if (siptr == NULL)
471da177e4SLinus Torvalds return EBT_DROP;
481da177e4SLinus Torvalds
491da177e4SLinus Torvalds diptr = skb_header_pointer(skb,
501da177e4SLinus Torvalds sizeof(_ah) + 2 * ETH_ALEN + sizeof(_sip),
511da177e4SLinus Torvalds sizeof(_dip), &_dip);
521da177e4SLinus Torvalds if (diptr == NULL)
531da177e4SLinus Torvalds return EBT_DROP;
541da177e4SLinus Torvalds
55613dbd95SPablo Neira Ayuso arp_send(ARPOP_REPLY, ETH_P_ARP, *siptr,
56613dbd95SPablo Neira Ayuso (struct net_device *)xt_in(par),
571da177e4SLinus Torvalds *diptr, shp, info->mac, shp);
581da177e4SLinus Torvalds
591da177e4SLinus Torvalds return info->target;
601da177e4SLinus Torvalds }
611da177e4SLinus Torvalds
ebt_arpreply_tg_check(const struct xt_tgchk_param * par)62135367b8SJan Engelhardt static int ebt_arpreply_tg_check(const struct xt_tgchk_param *par)
631da177e4SLinus Torvalds {
64af5d6dc2SJan Engelhardt const struct ebt_arpreply_info *info = par->targinfo;
65af5d6dc2SJan Engelhardt const struct ebt_entry *e = par->entryinfo;
661da177e4SLinus Torvalds
671da177e4SLinus Torvalds if (BASE_CHAIN && info->target == EBT_RETURN)
68d6b00a53SJan Engelhardt return -EINVAL;
691da177e4SLinus Torvalds if (e->ethproto != htons(ETH_P_ARP) ||
701da177e4SLinus Torvalds e->invflags & EBT_IPROTO)
71d6b00a53SJan Engelhardt return -EINVAL;
72c953d635SGao Feng if (ebt_invalid_target(info->target))
73c953d635SGao Feng return -EINVAL;
74c953d635SGao Feng
75d6b00a53SJan Engelhardt return 0;
761da177e4SLinus Torvalds }
771da177e4SLinus Torvalds
78043ef46cSJan Engelhardt static struct xt_target ebt_arpreply_tg_reg __read_mostly = {
79043ef46cSJan Engelhardt .name = "arpreply",
80001a18d3SJan Engelhardt .revision = 0,
81001a18d3SJan Engelhardt .family = NFPROTO_BRIDGE,
82f2ff525cSJan Engelhardt .table = "nat",
83f2ff525cSJan Engelhardt .hooks = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_PRE_ROUTING),
842d06d4a5SJan Engelhardt .target = ebt_arpreply_tg,
852d06d4a5SJan Engelhardt .checkentry = ebt_arpreply_tg_check,
86fc0e3df4SFlorian Westphal .targetsize = sizeof(struct ebt_arpreply_info),
871da177e4SLinus Torvalds .me = THIS_MODULE,
881da177e4SLinus Torvalds };
891da177e4SLinus Torvalds
ebt_arpreply_init(void)9065b4b4e8SAndrew Morton static int __init ebt_arpreply_init(void)
911da177e4SLinus Torvalds {
92043ef46cSJan Engelhardt return xt_register_target(&ebt_arpreply_tg_reg);
931da177e4SLinus Torvalds }
941da177e4SLinus Torvalds
ebt_arpreply_fini(void)9565b4b4e8SAndrew Morton static void __exit ebt_arpreply_fini(void)
961da177e4SLinus Torvalds {
97043ef46cSJan Engelhardt xt_unregister_target(&ebt_arpreply_tg_reg);
981da177e4SLinus Torvalds }
991da177e4SLinus Torvalds
10065b4b4e8SAndrew Morton module_init(ebt_arpreply_init);
10165b4b4e8SAndrew Morton module_exit(ebt_arpreply_fini);
102f776c4cdSJan Engelhardt MODULE_DESCRIPTION("Ebtables: ARP reply target");
1031da177e4SLinus Torvalds MODULE_LICENSE("GPL");
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