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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
18static bool
19ebt_arp_mt(const struct sk_buff *skb, const struct xt_match_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 && FWINV(info->opcode !=
29 ah->ar_op, EBT_ARP_OPCODE))
30 return false;
31 if (info->bitmask & EBT_ARP_HTYPE && FWINV(info->htype !=
32 ah->ar_hrd, EBT_ARP_HTYPE))
33 return false;
34 if (info->bitmask & EBT_ARP_PTYPE && FWINV(info->ptype !=
35 ah->ar_pro, EBT_ARP_PTYPE))
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 FWINV(info->saddr != (*sap & info->smsk), EBT_ARP_SRC_IP))
56 return false;
57 if (info->bitmask & EBT_ARP_DST_IP &&
58 FWINV(info->daddr != (*dap & info->dmsk), EBT_ARP_DST_IP))
59 return false;
60 if (info->bitmask & EBT_ARP_GRAT &&
61 FWINV(*dap != *sap, EBT_ARP_GRAT))
62 return false;
63 }
64
65 if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) {
66 const unsigned char *mp;
67 unsigned char _mac[ETH_ALEN];
68 uint8_t verdict, i;
69
70 if (ah->ar_hln != ETH_ALEN || ah->ar_hrd != htons(ARPHRD_ETHER))
71 return false;
72 if (info->bitmask & EBT_ARP_SRC_MAC) {
73 mp = skb_header_pointer(skb, sizeof(struct arphdr),
74 sizeof(_mac), &_mac);
75 if (mp == NULL)
76 return false;
77 verdict = 0;
78 for (i = 0; i < 6; i++)
79 verdict |= (mp[i] ^ info->smaddr[i]) &
80 info->smmsk[i];
81 if (FWINV(verdict != 0, EBT_ARP_SRC_MAC))
82 return false;
83 }
84
85 if (info->bitmask & EBT_ARP_DST_MAC) {
86 mp = skb_header_pointer(skb, sizeof(struct arphdr) +
87 ah->ar_hln + ah->ar_pln,
88 sizeof(_mac), &_mac);
89 if (mp == NULL)
90 return false;
91 verdict = 0;
92 for (i = 0; i < 6; i++)
93 verdict |= (mp[i] ^ info->dmaddr[i]) &
94 info->dmmsk[i];
95 if (FWINV(verdict != 0, EBT_ARP_DST_MAC))
96 return false;
97 }
98 }
99
100 return true;
101}
102
103static bool ebt_arp_mt_check(const struct xt_mtchk_param *par)
104{
105 const struct ebt_arp_info *info = par->matchinfo;
106 const struct ebt_entry *e = par->entryinfo;
107
108 if ((e->ethproto != htons(ETH_P_ARP) &&
109 e->ethproto != htons(ETH_P_RARP)) ||
110 e->invflags & EBT_IPROTO)
111 return false;
112 if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK)
113 return false;
114 return true;
115}
116
117static struct xt_match ebt_arp_mt_reg __read_mostly = {
118 .name = "arp",
119 .revision = 0,
120 .family = NFPROTO_BRIDGE,
121 .match = ebt_arp_mt,
122 .checkentry = ebt_arp_mt_check,
123 .matchsize = XT_ALIGN(sizeof(struct ebt_arp_info)),
124 .me = THIS_MODULE,
125};
126
127static int __init ebt_arp_init(void)
128{
129 return xt_register_match(&ebt_arp_mt_reg);
130}
131
132static void __exit ebt_arp_fini(void)
133{
134 xt_unregister_match(&ebt_arp_mt_reg);
135}
136
137module_init(ebt_arp_init);
138module_exit(ebt_arp_fini);
139MODULE_DESCRIPTION("Ebtables: ARP protocol packet match");
140MODULE_LICENSE("GPL");
141
