1/* 2 * ebt_arpreply 3 * 4 * Authors: 5 * Grzegorz Borowiak <grzes@gnu.univ.gda.pl> 6 * Bart De Schuymer <bdschuym@pandora.be> 7 * 8 * August, 2003 9 * 10 */ 11 12#include <linux/netfilter_bridge/ebtables.h> 13#include <linux/netfilter_bridge/ebt_arpreply.h> 14#include <linux/if_arp.h> 15#include <net/arp.h> 16#include <linux/module.h> 17 18static int ebt_target_reply(struct sk_buff **pskb, unsigned int hooknr, 19 const struct net_device *in, const struct net_device *out, 20 const void *data, unsigned int datalen) 21{ 22 struct ebt_arpreply_info *info = (struct ebt_arpreply_info *)data; 23 __be32 _sip, *siptr, _dip, *diptr; 24 struct arphdr _ah, *ap; 25 unsigned char _sha[ETH_ALEN], *shp; 26 struct sk_buff *skb = *pskb; 27 28 ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah); 29 if (ap == NULL) 30 return EBT_DROP; 31 32 if (ap->ar_op != htons(ARPOP_REQUEST) || 33 ap->ar_hln != ETH_ALEN || 34 ap->ar_pro != htons(ETH_P_IP) || 35 ap->ar_pln != 4) 36 return EBT_CONTINUE; 37 38 shp = skb_header_pointer(skb, sizeof(_ah), ETH_ALEN, &_sha); 39 if (shp == NULL) 40 return EBT_DROP; 41 42 siptr = skb_header_pointer(skb, sizeof(_ah) + ETH_ALEN, 43 sizeof(_sip), &_sip); 44 if (siptr == NULL) 45 return EBT_DROP; 46 47 diptr = skb_header_pointer(skb, 48 sizeof(_ah) + 2 * ETH_ALEN + sizeof(_sip), 49 sizeof(_dip), &_dip); 50 if (diptr == NULL) 51 return EBT_DROP; 52 53 arp_send(ARPOP_REPLY, ETH_P_ARP, *siptr, (struct net_device *)in, 54 *diptr, shp, info->mac, shp); 55 56 return info->target; 57} 58 59static int ebt_target_reply_check(const char *tablename, unsigned int hookmask, 60 const struct ebt_entry *e, void *data, unsigned int datalen) 61{ 62 struct ebt_arpreply_info *info = (struct ebt_arpreply_info *)data; 63 64 if (datalen != EBT_ALIGN(sizeof(struct ebt_arpreply_info))) 65 return -EINVAL; 66 if (BASE_CHAIN && info->target == EBT_RETURN) 67 return -EINVAL; 68 if (e->ethproto != htons(ETH_P_ARP) || 69 e->invflags & EBT_IPROTO) 70 return -EINVAL; 71 CLEAR_BASE_CHAIN_BIT; 72 if (strcmp(tablename, "nat") || hookmask & ~(1 << NF_BR_PRE_ROUTING)) 73 return -EINVAL; 74 return 0; 75} 76 77static struct ebt_target reply_target = 78{ 79 .name = EBT_ARPREPLY_TARGET, 80 .target = ebt_target_reply, 81 .check = ebt_target_reply_check, 82 .me = THIS_MODULE, 83}; 84 85static int __init ebt_arpreply_init(void) 86{ 87 return ebt_register_target(&reply_target); 88} 89 90static void __exit ebt_arpreply_fini(void) 91{ 92 ebt_unregister_target(&reply_target); 93} 94 95module_init(ebt_arpreply_init); 96module_exit(ebt_arpreply_fini); 97MODULE_LICENSE("GPL"); 98