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 #include <linux/if_arp.h> 12 #include <linux/if_ether.h> 13 #include <linux/module.h> 14 #include <linux/netfilter/x_tables.h> 15 #include <linux/netfilter_bridge/ebtables.h> 16 #include <linux/netfilter_bridge/ebt_arp.h> 17 18 static bool 19 ebt_arp_mt(const struct sk_buff *skb, struct xt_action_param *par) 20 { 21 const struct ebt_arp_info *info = par->matchinfo; 22 const struct arphdr *ah; 23 struct arphdr _arph; 24 25 ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph); 26 if (ah == NULL) 27 return false; 28 if ((info->bitmask & EBT_ARP_OPCODE) && 29 NF_INVF(info, EBT_ARP_OPCODE, info->opcode != ah->ar_op)) 30 return false; 31 if ((info->bitmask & EBT_ARP_HTYPE) && 32 NF_INVF(info, EBT_ARP_HTYPE, info->htype != ah->ar_hrd)) 33 return false; 34 if ((info->bitmask & EBT_ARP_PTYPE) && 35 NF_INVF(info, EBT_ARP_PTYPE, info->ptype != ah->ar_pro)) 36 return false; 37 38 if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP | EBT_ARP_GRAT)) { 39 const __be32 *sap, *dap; 40 __be32 saddr, daddr; 41 42 if (ah->ar_pln != sizeof(__be32) || ah->ar_pro != htons(ETH_P_IP)) 43 return false; 44 sap = skb_header_pointer(skb, sizeof(struct arphdr) + 45 ah->ar_hln, sizeof(saddr), 46 &saddr); 47 if (sap == NULL) 48 return false; 49 dap = skb_header_pointer(skb, sizeof(struct arphdr) + 50 2*ah->ar_hln+sizeof(saddr), 51 sizeof(daddr), &daddr); 52 if (dap == NULL) 53 return false; 54 if ((info->bitmask & EBT_ARP_SRC_IP) && 55 NF_INVF(info, EBT_ARP_SRC_IP, 56 info->saddr != (*sap & info->smsk))) 57 return false; 58 if ((info->bitmask & EBT_ARP_DST_IP) && 59 NF_INVF(info, EBT_ARP_DST_IP, 60 info->daddr != (*dap & info->dmsk))) 61 return false; 62 if ((info->bitmask & EBT_ARP_GRAT) && 63 NF_INVF(info, EBT_ARP_GRAT, *dap != *sap)) 64 return false; 65 } 66 67 if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) { 68 const unsigned char *mp; 69 unsigned char _mac[ETH_ALEN]; 70 71 if (ah->ar_hln != ETH_ALEN || ah->ar_hrd != htons(ARPHRD_ETHER)) 72 return false; 73 if (info->bitmask & EBT_ARP_SRC_MAC) { 74 mp = skb_header_pointer(skb, sizeof(struct arphdr), 75 sizeof(_mac), &_mac); 76 if (mp == NULL) 77 return false; 78 if (NF_INVF(info, EBT_ARP_SRC_MAC, 79 !ether_addr_equal_masked(mp, info->smaddr, 80 info->smmsk))) 81 return false; 82 } 83 84 if (info->bitmask & EBT_ARP_DST_MAC) { 85 mp = skb_header_pointer(skb, sizeof(struct arphdr) + 86 ah->ar_hln + ah->ar_pln, 87 sizeof(_mac), &_mac); 88 if (mp == NULL) 89 return false; 90 if (NF_INVF(info, EBT_ARP_DST_MAC, 91 !ether_addr_equal_masked(mp, info->dmaddr, 92 info->dmmsk))) 93 return false; 94 } 95 } 96 97 return true; 98 } 99 100 static int ebt_arp_mt_check(const struct xt_mtchk_param *par) 101 { 102 const struct ebt_arp_info *info = par->matchinfo; 103 const struct ebt_entry *e = par->entryinfo; 104 105 if ((e->ethproto != htons(ETH_P_ARP) && 106 e->ethproto != htons(ETH_P_RARP)) || 107 e->invflags & EBT_IPROTO) 108 return -EINVAL; 109 if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK) 110 return -EINVAL; 111 return 0; 112 } 113 114 static struct xt_match ebt_arp_mt_reg __read_mostly = { 115 .name = "arp", 116 .revision = 0, 117 .family = NFPROTO_BRIDGE, 118 .match = ebt_arp_mt, 119 .checkentry = ebt_arp_mt_check, 120 .matchsize = sizeof(struct ebt_arp_info), 121 .me = THIS_MODULE, 122 }; 123 124 static int __init ebt_arp_init(void) 125 { 126 return xt_register_match(&ebt_arp_mt_reg); 127 } 128 129 static void __exit ebt_arp_fini(void) 130 { 131 xt_unregister_match(&ebt_arp_mt_reg); 132 } 133 134 module_init(ebt_arp_init); 135 module_exit(ebt_arp_fini); 136 MODULE_DESCRIPTION("Ebtables: ARP protocol packet match"); 137 MODULE_LICENSE("GPL"); 138