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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 | // SPDX-License-Identifier: GPL-2.0-only /* * ebt_arpreply * * Authors: * Grzegorz Borowiak <grzes@gnu.univ.gda.pl> * Bart De Schuymer <bdschuym@pandora.be> * * August, 2003 * */ #include <linux/if_arp.h> #include <net/arp.h> #include <linux/module.h> #include <linux/netfilter/x_tables.h> #include <linux/netfilter_bridge/ebtables.h> #include <linux/netfilter_bridge/ebt_arpreply.h> static unsigned int ebt_arpreply_tg(struct sk_buff *skb, const struct xt_action_param *par) { const struct ebt_arpreply_info *info = par->targinfo; const __be32 *siptr, *diptr; __be32 _sip, _dip; const struct arphdr *ap; struct arphdr _ah; const unsigned char *shp; unsigned char _sha[ETH_ALEN]; ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah); if (ap == NULL) return EBT_DROP; if (ap->ar_op != htons(ARPOP_REQUEST) || ap->ar_hln != ETH_ALEN || ap->ar_pro != htons(ETH_P_IP) || ap->ar_pln != 4) return EBT_CONTINUE; shp = skb_header_pointer(skb, sizeof(_ah), ETH_ALEN, &_sha); if (shp == NULL) return EBT_DROP; siptr = skb_header_pointer(skb, sizeof(_ah) + ETH_ALEN, sizeof(_sip), &_sip); if (siptr == NULL) return EBT_DROP; diptr = skb_header_pointer(skb, sizeof(_ah) + 2 * ETH_ALEN + sizeof(_sip), sizeof(_dip), &_dip); if (diptr == NULL) return EBT_DROP; arp_send(ARPOP_REPLY, ETH_P_ARP, *siptr, (struct net_device *)xt_in(par), *diptr, shp, info->mac, shp); return info->target; } static int ebt_arpreply_tg_check(const struct xt_tgchk_param *par) { const struct ebt_arpreply_info *info = par->targinfo; const struct ebt_entry *e = par->entryinfo; if (BASE_CHAIN && info->target == EBT_RETURN) return -EINVAL; if (e->ethproto != htons(ETH_P_ARP) || e->invflags & EBT_IPROTO) return -EINVAL; if (ebt_invalid_target(info->target)) return -EINVAL; return 0; } static struct xt_target ebt_arpreply_tg_reg __read_mostly = { .name = "arpreply", .revision = 0, .family = NFPROTO_BRIDGE, .table = "nat", .hooks = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_PRE_ROUTING), .target = ebt_arpreply_tg, .checkentry = ebt_arpreply_tg_check, .targetsize = sizeof(struct ebt_arpreply_info), .me = THIS_MODULE, }; static int __init ebt_arpreply_init(void) { return xt_register_target(&ebt_arpreply_tg_reg); } static void __exit ebt_arpreply_fini(void) { xt_unregister_target(&ebt_arpreply_tg_reg); } module_init(ebt_arpreply_init); module_exit(ebt_arpreply_fini); MODULE_DESCRIPTION("Ebtables: ARP reply target"); MODULE_LICENSE("GPL"); |