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
18 static 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 uint32_t _addr, *ap;
39
40 /* IPv4 addresses are always 4 bytes */
41 if (ah->ar_pln != sizeof(uint32_t))
42 return EBT_NOMATCH;
43 if (info->bitmask & EBT_ARP_SRC_IP) {
44 ap = skb_header_pointer(skb, sizeof(struct arphdr) +
45 ah->ar_hln, sizeof(_addr),
46 &_addr);
47 if (ap == NULL)
48 return EBT_NOMATCH;
49 if (FWINV(info->saddr != (*ap & info->smsk),
50 EBT_ARP_SRC_IP))
51 return EBT_NOMATCH;
52 }
53
54 if (info->bitmask & EBT_ARP_DST_IP) {
55 ap = skb_header_pointer(skb, sizeof(struct arphdr) +
56 2*ah->ar_hln+sizeof(uint32_t),
57 sizeof(_addr), &_addr);
58 if (ap == NULL)
59 return EBT_NOMATCH;
60 if (FWINV(info->daddr != (*ap & info->dmsk),
61 EBT_ARP_DST_IP))
62 return EBT_NOMATCH;
63 }
64 }
65
66 if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) {
67 unsigned char _mac[ETH_ALEN], *mp;
68 uint8_t verdict, i;
69
70 /* MAC addresses are 6 bytes */
71 if (ah->ar_hln != ETH_ALEN)
72 return EBT_NOMATCH;
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 EBT_NOMATCH;
78 verdict = 0;
79 for (i = 0; i < 6; i++)
80 verdict |= (mp[i] ^ info->smaddr[i]) &
81 info->smmsk[i];
82 if (FWINV(verdict != 0, EBT_ARP_SRC_MAC))
83 return EBT_NOMATCH;
84 }
85
86 if (info->bitmask & EBT_ARP_DST_MAC) {
87 mp = skb_header_pointer(skb, sizeof(struct arphdr) +
88 ah->ar_hln + ah->ar_pln,
89 sizeof(_mac), &_mac);
90 if (mp == NULL)
91 return EBT_NOMATCH;
92 verdict = 0;
93 for (i = 0; i < 6; i++)
94 verdict |= (mp[i] ^ info->dmaddr[i]) &
95 info->dmmsk[i];
96 if (FWINV(verdict != 0, EBT_ARP_DST_MAC))
97 return EBT_NOMATCH;
98 }
99 }
100
101 return EBT_MATCH;
102 }
103
104 static int ebt_arp_check(const char *tablename, unsigned int hookmask,
105 const struct ebt_entry *e, void *data, unsigned int datalen)
106 {
107 struct ebt_arp_info *info = (struct ebt_arp_info *)data;
108
109 if (datalen != EBT_ALIGN(sizeof(struct ebt_arp_info)))
110 return -EINVAL;
111 if ((e->ethproto != htons(ETH_P_ARP) &&
112 e->ethproto != htons(ETH_P_RARP)) ||
113 e->invflags & EBT_IPROTO)
114 return -EINVAL;
115 if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK)
116 return -EINVAL;
117 return 0;
118 }
119
120 static struct ebt_match filter_arp =
121 {
122 .name = EBT_ARP_MATCH,
123 .match = ebt_filter_arp,
124 .check = ebt_arp_check,
125 .me = THIS_MODULE,
126 };
127
128 static int __init init(void)
129 {
130 return ebt_register_match(&filter_arp);
131 }
132
133 static void __exit fini(void)
134 {
135 ebt_unregister_match(&filter_arp);
136 }
137
138 module_init(init);
139 module_exit(fini);
140 MODULE_LICENSE("GPL");
141
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