// SPDX-License-Identifier: GPL-2.0-only
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/*
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* ebt_arp
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*
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* Authors:
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* Bart De Schuymer <bdschuym@pandora.be>
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* Tim Gardner <timg@tpi.com>
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*
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* April, 2002
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*
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*/
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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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static bool
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ebt_arp_mt(const struct sk_buff *skb, struct xt_action_param *par)
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{
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const struct ebt_arp_info *info = par->matchinfo;
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const struct arphdr *ah;
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struct arphdr _arph;
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ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
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if (ah == NULL)
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return false;
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if ((info->bitmask & EBT_ARP_OPCODE) &&
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NF_INVF(info, EBT_ARP_OPCODE, info->opcode != ah->ar_op))
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return false;
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if ((info->bitmask & EBT_ARP_HTYPE) &&
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NF_INVF(info, EBT_ARP_HTYPE, info->htype != ah->ar_hrd))
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return false;
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if ((info->bitmask & EBT_ARP_PTYPE) &&
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NF_INVF(info, EBT_ARP_PTYPE, info->ptype != ah->ar_pro))
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return false;
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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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__be32 saddr, daddr;
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if (ah->ar_pln != sizeof(__be32) || ah->ar_pro != htons(ETH_P_IP))
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return false;
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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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&saddr);
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if (sap == NULL)
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return false;
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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 (dap == NULL)
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return false;
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if ((info->bitmask & EBT_ARP_SRC_IP) &&
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NF_INVF(info, EBT_ARP_SRC_IP,
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info->saddr != (*sap & info->smsk)))
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return false;
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if ((info->bitmask & EBT_ARP_DST_IP) &&
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NF_INVF(info, EBT_ARP_DST_IP,
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info->daddr != (*dap & info->dmsk)))
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return false;
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if ((info->bitmask & EBT_ARP_GRAT) &&
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NF_INVF(info, EBT_ARP_GRAT, *dap != *sap))
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return false;
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}
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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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return false;
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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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sizeof(_mac), &_mac);
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if (mp == NULL)
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return false;
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if (NF_INVF(info, EBT_ARP_SRC_MAC,
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!ether_addr_equal_masked(mp, info->smaddr,
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info->smmsk)))
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return false;
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}
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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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sizeof(_mac), &_mac);
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if (mp == NULL)
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return false;
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if (NF_INVF(info, EBT_ARP_DST_MAC,
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!ether_addr_equal_masked(mp, info->dmaddr,
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info->dmmsk)))
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return false;
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}
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}
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return true;
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}
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static int ebt_arp_mt_check(const struct xt_mtchk_param *par)
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{
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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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return -EINVAL;
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if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK)
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return -EINVAL;
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return 0;
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}
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static struct xt_match ebt_arp_mt_reg __read_mostly = {
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.name = "arp",
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.revision = 0,
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.family = NFPROTO_BRIDGE,
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.match = ebt_arp_mt,
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.checkentry = ebt_arp_mt_check,
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.matchsize = sizeof(struct ebt_arp_info),
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.me = THIS_MODULE,
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};
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static int __init ebt_arp_init(void)
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{
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return xt_register_match(&ebt_arp_mt_reg);
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}
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static void __exit ebt_arp_fini(void)
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{
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xt_unregister_match(&ebt_arp_mt_reg);
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}
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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");
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