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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, 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
100static 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
114static 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
124static int __init ebt_arp_init(void)
125{
126 return xt_register_match(&ebt_arp_mt_reg);
127}
128
129static void __exit ebt_arp_fini(void)
130{
131 xt_unregister_match(&ebt_arp_mt_reg);
132}
133
134module_init(ebt_arp_init);
135module_exit(ebt_arp_fini);
136MODULE_DESCRIPTION("Ebtables: ARP protocol packet match");
137MODULE_LICENSE("GPL");
138
