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- // SPDX-License-Identifier: GPL-2.0-only
- /*
- * ebt_arp
- *
- * Authors:
- * Bart De Schuymer <bdschuym@pandora.be>
- * Tim Gardner <timg@tpi.com>
- *
- * April, 2002
- *
- */
- #include <linux/if_arp.h>
- #include <linux/if_ether.h>
- #include <linux/module.h>
- #include <linux/netfilter/x_tables.h>
- #include <linux/netfilter_bridge/ebtables.h>
- #include <linux/netfilter_bridge/ebt_arp.h>
- static bool
- ebt_arp_mt(const struct sk_buff *skb, struct xt_action_param *par)
- {
- const struct ebt_arp_info *info = par->matchinfo;
- const struct arphdr *ah;
- struct arphdr _arph;
- ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
- if (ah == NULL)
- return false;
- if ((info->bitmask & EBT_ARP_OPCODE) &&
- NF_INVF(info, EBT_ARP_OPCODE, info->opcode != ah->ar_op))
- return false;
- if ((info->bitmask & EBT_ARP_HTYPE) &&
- NF_INVF(info, EBT_ARP_HTYPE, info->htype != ah->ar_hrd))
- return false;
- if ((info->bitmask & EBT_ARP_PTYPE) &&
- NF_INVF(info, EBT_ARP_PTYPE, info->ptype != ah->ar_pro))
- return false;
- if (info->bitmask & (EBT_ARP_SRC_IP | EBT_ARP_DST_IP | EBT_ARP_GRAT)) {
- const __be32 *sap, *dap;
- __be32 saddr, daddr;
- if (ah->ar_pln != sizeof(__be32) || ah->ar_pro != htons(ETH_P_IP))
- return false;
- sap = skb_header_pointer(skb, sizeof(struct arphdr) +
- ah->ar_hln, sizeof(saddr),
- &saddr);
- if (sap == NULL)
- return false;
- dap = skb_header_pointer(skb, sizeof(struct arphdr) +
- 2*ah->ar_hln+sizeof(saddr),
- sizeof(daddr), &daddr);
- if (dap == NULL)
- return false;
- if ((info->bitmask & EBT_ARP_SRC_IP) &&
- NF_INVF(info, EBT_ARP_SRC_IP,
- info->saddr != (*sap & info->smsk)))
- return false;
- if ((info->bitmask & EBT_ARP_DST_IP) &&
- NF_INVF(info, EBT_ARP_DST_IP,
- info->daddr != (*dap & info->dmsk)))
- return false;
- if ((info->bitmask & EBT_ARP_GRAT) &&
- NF_INVF(info, EBT_ARP_GRAT, *dap != *sap))
- return false;
- }
- if (info->bitmask & (EBT_ARP_SRC_MAC | EBT_ARP_DST_MAC)) {
- const unsigned char *mp;
- unsigned char _mac[ETH_ALEN];
- if (ah->ar_hln != ETH_ALEN || ah->ar_hrd != htons(ARPHRD_ETHER))
- return false;
- if (info->bitmask & EBT_ARP_SRC_MAC) {
- mp = skb_header_pointer(skb, sizeof(struct arphdr),
- sizeof(_mac), &_mac);
- if (mp == NULL)
- return false;
- if (NF_INVF(info, EBT_ARP_SRC_MAC,
- !ether_addr_equal_masked(mp, info->smaddr,
- info->smmsk)))
- return false;
- }
- if (info->bitmask & EBT_ARP_DST_MAC) {
- mp = skb_header_pointer(skb, sizeof(struct arphdr) +
- ah->ar_hln + ah->ar_pln,
- sizeof(_mac), &_mac);
- if (mp == NULL)
- return false;
- if (NF_INVF(info, EBT_ARP_DST_MAC,
- !ether_addr_equal_masked(mp, info->dmaddr,
- info->dmmsk)))
- return false;
- }
- }
- return true;
- }
- static int ebt_arp_mt_check(const struct xt_mtchk_param *par)
- {
- const struct ebt_arp_info *info = par->matchinfo;
- const struct ebt_entry *e = par->entryinfo;
- if ((e->ethproto != htons(ETH_P_ARP) &&
- e->ethproto != htons(ETH_P_RARP)) ||
- e->invflags & EBT_IPROTO)
- return -EINVAL;
- if (info->bitmask & ~EBT_ARP_MASK || info->invflags & ~EBT_ARP_MASK)
- return -EINVAL;
- return 0;
- }
- static struct xt_match ebt_arp_mt_reg __read_mostly = {
- .name = "arp",
- .revision = 0,
- .family = NFPROTO_BRIDGE,
- .match = ebt_arp_mt,
- .checkentry = ebt_arp_mt_check,
- .matchsize = sizeof(struct ebt_arp_info),
- .me = THIS_MODULE,
- };
- static int __init ebt_arp_init(void)
- {
- return xt_register_match(&ebt_arp_mt_reg);
- }
- static void __exit ebt_arp_fini(void)
- {
- xt_unregister_match(&ebt_arp_mt_reg);
- }
- module_init(ebt_arp_init);
- module_exit(ebt_arp_fini);
- MODULE_DESCRIPTION("Ebtables: ARP protocol packet match");
- MODULE_LICENSE("GPL");
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