1/* 2 * ebt_arp 3 * 4 * Authors: 5 * Bart De Schuymer <bdschuym@pandora.be> 6 * Tim Gardner <timg@tpi.com> 7 * 8 * April, 2002 9 * 10 */ 11 12#include <linux/netfilter_bridge/ebtables.h> 13#include <linux/netfilter_bridge/ebt_arp.h> 14#include <linux/if_arp.h> 15#include <linux/if_ether.h> 16#include <linux/module.h> 17 18static int ebt_filter_arp(const struct sk_buff *skb, const struct net_device *in, 19 const struct net_device *out, const void *data, unsigned int datalen) 20{ 21 struct ebt_arp_info *info = (struct ebt_arp_info *)data; 22 struct arphdr _arph, *ah; 23 24 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph); 25 if (ah == NULL) 26 return EBT_NOMATCH; 27 if (info->bitmask & EBT_ARP_OPCODE && FWINV(info->opcode != 28 ah->ar_op, EBT_ARP_OPCODE)) 29 return EBT_NOMATCH; 30 if (info->bitmask & EBT_ARP_HTYPE && FWINV(info->htype != 31 ah->ar_hrd, EBT_ARP_HTYPE)) 32 return EBT_NOMATCH; 33 if (info->bitmask & EBT_ARP_PTYPE && FWINV(info->ptype != 34 ah->ar_pro, EBT_ARP_PTYPE)) 35 return EBT_NOMATCH; 36 37 if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP)) { 38 __be32 saddr, daddr, *sap, *dap; 39 40 if (ah->ar_pln != sizeof(__be32) || ah->ar_pro != htons(ETH_P_IP)) 41 return EBT_NOMATCH; 42 sap = skb_header_pointer(skb, sizeof(struct arphdr) + 43 ah->ar_hln, sizeof(saddr), 44 &saddr); 45 if (sap == NULL) 46 return EBT_NOMATCH; 47 dap = skb_header_pointer(skb, sizeof(struct arphdr) + 48 2*ah->ar_hln+sizeof(saddr), 49 sizeof(daddr), &daddr); 50 if (dap == NULL) 51 return EBT_NOMATCH; 52 if (info->bitmask & EBT_ARP_SRC_IP && 53 FWINV(info->saddr != (*sap & info->smsk), EBT_ARP_SRC_IP)) 54 return EBT_NOMATCH; 55 if (info->bitmask & EBT_ARP_DST_IP && 56 FWINV(info->daddr != (*dap & info->dmsk), EBT_ARP_DST_IP)) 57 return EBT_NOMATCH; 58 if (info->bitmask & EBT_ARP_GRAT && 59 FWINV(*dap != *sap, EBT_ARP_GRAT)) 60 return EBT_NOMATCH; 61 } 62 63 if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) { 64 unsigned char _mac[ETH_ALEN], *mp; 65 uint8_t verdict, i; 66 67 if (ah->ar_hln != ETH_ALEN || ah->ar_hrd != htons(ARPHRD_ETHER)) 68 return EBT_NOMATCH; 69 if (info->bitmask & EBT_ARP_SRC_MAC) { 70 mp = skb_header_pointer(skb, sizeof(struct arphdr), 71 sizeof(_mac), &_mac); 72 if (mp == NULL) 73 return EBT_NOMATCH; 74 verdict = 0; 75 for (i = 0; i < 6; i++) 76 verdict |= (mp[i] ^ info->smaddr[i]) & 77 info->smmsk[i]; 78 if (FWINV(verdict != 0, EBT_ARP_SRC_MAC)) 79 return EBT_NOMATCH; 80 } 81 82 if (info->bitmask & EBT_ARP_DST_MAC) { 83 mp = skb_header_pointer(skb, sizeof(struct arphdr) + 84 ah->ar_hln + ah->ar_pln, 85 sizeof(_mac), &_mac); 86 if (mp == NULL) 87 return EBT_NOMATCH; 88 verdict = 0; 89 for (i = 0; i < 6; i++) 90 verdict |= (mp[i] ^ info->dmaddr[i]) & 91 info->dmmsk[i]; 92 if (FWINV(verdict != 0, EBT_ARP_DST_MAC)) 93 return EBT_NOMATCH; 94 } 95 } 96 97 return EBT_MATCH; 98} 99 100static int ebt_arp_check(const char *tablename, unsigned int hookmask, 101 const struct ebt_entry *e, void *data, unsigned int datalen) 102{ 103 struct ebt_arp_info *info = (struct ebt_arp_info *)data; 104 105 if (datalen != EBT_ALIGN(sizeof(struct ebt_arp_info))) 106 return -EINVAL; 107 if ((e->ethproto != htons(ETH_P_ARP) && 108 e->ethproto != htons(ETH_P_RARP)) || 109 e->invflags & EBT_IPROTO) 110 return -EINVAL; 111 if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK) 112 return -EINVAL; 113 return 0; 114} 115 116static struct ebt_match filter_arp = 117{ 118 .name = EBT_ARP_MATCH, 119 .match = ebt_filter_arp, 120 .check = ebt_arp_check, 121 .me = THIS_MODULE, 122}; 123 124static int __init ebt_arp_init(void) 125{ 126 return ebt_register_match(&filter_arp); 127} 128 129static void __exit ebt_arp_fini(void) 130{ 131 ebt_unregister_match(&filter_arp); 132} 133 134module_init(ebt_arp_init); 135module_exit(ebt_arp_fini); 136MODULE_LICENSE("GPL"); 137