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* Bart De Schuymer <bdschuym@pandora.be>
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* Tim Gardner <timg@tpi.com>
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#include <linux/if_arp.h>
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#include <linux/if_ether.h>
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#include <linux/module.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter_bridge/ebtables.h>
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#include <linux/netfilter_bridge/ebt_arp.h>
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ebt_arp_mt(const struct sk_buff *skb, struct xt_action_param *par)
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const struct ebt_arp_info *info = par->matchinfo;
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const struct arphdr *ah;
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ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
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if (info->bitmask & EBT_ARP_OPCODE && FWINV(info->opcode !=
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ah->ar_op, EBT_ARP_OPCODE))
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if (info->bitmask & EBT_ARP_HTYPE && FWINV(info->htype !=
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ah->ar_hrd, EBT_ARP_HTYPE))
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if (info->bitmask & EBT_ARP_PTYPE && FWINV(info->ptype !=
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ah->ar_pro, EBT_ARP_PTYPE))
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if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP | EBT_ARP_GRAT)) {
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const __be32 *sap, *dap;
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if (ah->ar_pln != sizeof(__be32) || ah->ar_pro != htons(ETH_P_IP))
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sap = skb_header_pointer(skb, sizeof(struct arphdr) +
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ah->ar_hln, sizeof(saddr),
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dap = skb_header_pointer(skb, sizeof(struct arphdr) +
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2*ah->ar_hln+sizeof(saddr),
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sizeof(daddr), &daddr);
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if (info->bitmask & EBT_ARP_SRC_IP &&
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FWINV(info->saddr != (*sap & info->smsk), EBT_ARP_SRC_IP))
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if (info->bitmask & EBT_ARP_DST_IP &&
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FWINV(info->daddr != (*dap & info->dmsk), EBT_ARP_DST_IP))
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if (info->bitmask & EBT_ARP_GRAT &&
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FWINV(*dap != *sap, EBT_ARP_GRAT))
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if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) {
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const unsigned char *mp;
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unsigned char _mac[ETH_ALEN];
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if (ah->ar_hln != ETH_ALEN || ah->ar_hrd != htons(ARPHRD_ETHER))
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if (info->bitmask & EBT_ARP_SRC_MAC) {
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mp = skb_header_pointer(skb, sizeof(struct arphdr),
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for (i = 0; i < 6; i++)
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verdict |= (mp[i] ^ info->smaddr[i]) &
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if (FWINV(verdict != 0, EBT_ARP_SRC_MAC))
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if (info->bitmask & EBT_ARP_DST_MAC) {
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mp = skb_header_pointer(skb, sizeof(struct arphdr) +
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ah->ar_hln + ah->ar_pln,
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for (i = 0; i < 6; i++)
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verdict |= (mp[i] ^ info->dmaddr[i]) &
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if (FWINV(verdict != 0, EBT_ARP_DST_MAC))
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static int ebt_arp_mt_check(const struct xt_mtchk_param *par)
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const struct ebt_arp_info *info = par->matchinfo;
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const struct ebt_entry *e = par->entryinfo;
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if ((e->ethproto != htons(ETH_P_ARP) &&
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e->ethproto != htons(ETH_P_RARP)) ||
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e->invflags & EBT_IPROTO)
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if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK)
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static struct xt_match ebt_arp_mt_reg __read_mostly = {
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.family = NFPROTO_BRIDGE,
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.checkentry = ebt_arp_mt_check,
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.matchsize = sizeof(struct ebt_arp_info),
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static int __init ebt_arp_init(void)
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return xt_register_match(&ebt_arp_mt_reg);
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static void __exit ebt_arp_fini(void)
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xt_unregister_match(&ebt_arp_mt_reg);
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module_init(ebt_arp_init);
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module_exit(ebt_arp_fini);
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MODULE_DESCRIPTION("Ebtables: ARP protocol packet match");
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MODULE_LICENSE("GPL");