// SPDX-License-Identifier: GPL-2.0-only
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/*
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* ebt_stp
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*
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* Authors:
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* Bart De Schuymer <bdschuym@pandora.be>
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* Stephen Hemminger <shemminger@osdl.org>
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*
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* July, 2003
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*/
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#include <linux/etherdevice.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_stp.h>
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#define BPDU_TYPE_CONFIG 0
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struct stp_header {
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u8 dsap;
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u8 ssap;
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u8 ctrl;
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u8 pid;
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u8 vers;
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u8 type;
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};
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struct stp_config_pdu {
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u8 flags;
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u8 root[8];
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u8 root_cost[4];
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u8 sender[8];
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u8 port[2];
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u8 msg_age[2];
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u8 max_age[2];
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u8 hello_time[2];
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u8 forward_delay[2];
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};
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#define NR16(p) (p[0] << 8 | p[1])
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#define NR32(p) ((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3])
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static bool ebt_filter_config(const struct ebt_stp_info *info,
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const struct stp_config_pdu *stpc)
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{
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const struct ebt_stp_config_info *c;
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u16 v16;
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u32 v32;
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c = &info->config;
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if ((info->bitmask & EBT_STP_FLAGS) &&
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NF_INVF(info, EBT_STP_FLAGS, c->flags != stpc->flags))
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return false;
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if (info->bitmask & EBT_STP_ROOTPRIO) {
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v16 = NR16(stpc->root);
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if (NF_INVF(info, EBT_STP_ROOTPRIO,
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v16 < c->root_priol || v16 > c->root_priou))
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return false;
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}
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if (info->bitmask & EBT_STP_ROOTADDR) {
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if (NF_INVF(info, EBT_STP_ROOTADDR,
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!ether_addr_equal_masked(&stpc->root[2],
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c->root_addr,
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c->root_addrmsk)))
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return false;
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}
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if (info->bitmask & EBT_STP_ROOTCOST) {
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v32 = NR32(stpc->root_cost);
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if (NF_INVF(info, EBT_STP_ROOTCOST,
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v32 < c->root_costl || v32 > c->root_costu))
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return false;
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}
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if (info->bitmask & EBT_STP_SENDERPRIO) {
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v16 = NR16(stpc->sender);
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if (NF_INVF(info, EBT_STP_SENDERPRIO,
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v16 < c->sender_priol || v16 > c->sender_priou))
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return false;
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}
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if (info->bitmask & EBT_STP_SENDERADDR) {
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if (NF_INVF(info, EBT_STP_SENDERADDR,
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!ether_addr_equal_masked(&stpc->sender[2],
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c->sender_addr,
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c->sender_addrmsk)))
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return false;
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}
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if (info->bitmask & EBT_STP_PORT) {
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v16 = NR16(stpc->port);
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if (NF_INVF(info, EBT_STP_PORT,
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v16 < c->portl || v16 > c->portu))
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return false;
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}
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if (info->bitmask & EBT_STP_MSGAGE) {
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v16 = NR16(stpc->msg_age);
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if (NF_INVF(info, EBT_STP_MSGAGE,
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v16 < c->msg_agel || v16 > c->msg_ageu))
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return false;
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}
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if (info->bitmask & EBT_STP_MAXAGE) {
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v16 = NR16(stpc->max_age);
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if (NF_INVF(info, EBT_STP_MAXAGE,
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v16 < c->max_agel || v16 > c->max_ageu))
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return false;
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}
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if (info->bitmask & EBT_STP_HELLOTIME) {
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v16 = NR16(stpc->hello_time);
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if (NF_INVF(info, EBT_STP_HELLOTIME,
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v16 < c->hello_timel || v16 > c->hello_timeu))
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return false;
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}
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if (info->bitmask & EBT_STP_FWDD) {
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v16 = NR16(stpc->forward_delay);
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if (NF_INVF(info, EBT_STP_FWDD,
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v16 < c->forward_delayl || v16 > c->forward_delayu))
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return false;
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}
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return true;
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}
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static bool
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ebt_stp_mt(const struct sk_buff *skb, struct xt_action_param *par)
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{
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const struct ebt_stp_info *info = par->matchinfo;
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const struct stp_header *sp;
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struct stp_header _stph;
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const u8 header[6] = {0x42, 0x42, 0x03, 0x00, 0x00, 0x00};
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sp = skb_header_pointer(skb, 0, sizeof(_stph), &_stph);
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if (sp == NULL)
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return false;
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/* The stp code only considers these */
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if (memcmp(sp, header, sizeof(header)))
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return false;
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if ((info->bitmask & EBT_STP_TYPE) &&
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NF_INVF(info, EBT_STP_TYPE, info->type != sp->type))
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return false;
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if (sp->type == BPDU_TYPE_CONFIG &&
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info->bitmask & EBT_STP_CONFIG_MASK) {
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const struct stp_config_pdu *st;
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struct stp_config_pdu _stpc;
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st = skb_header_pointer(skb, sizeof(_stph),
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sizeof(_stpc), &_stpc);
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if (st == NULL)
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return false;
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return ebt_filter_config(info, st);
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}
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return true;
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}
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static int ebt_stp_mt_check(const struct xt_mtchk_param *par)
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{
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const struct ebt_stp_info *info = par->matchinfo;
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const struct ebt_entry *e = par->entryinfo;
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if (info->bitmask & ~EBT_STP_MASK || info->invflags & ~EBT_STP_MASK ||
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!(info->bitmask & EBT_STP_MASK))
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return -EINVAL;
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/* Make sure the match only receives stp frames */
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if (!par->nft_compat &&
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(!ether_addr_equal(e->destmac, eth_stp_addr) ||
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!(e->bitmask & EBT_DESTMAC) ||
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!is_broadcast_ether_addr(e->destmsk)))
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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_stp_mt_reg __read_mostly = {
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.name = "stp",
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.revision = 0,
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.family = NFPROTO_BRIDGE,
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.match = ebt_stp_mt,
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.checkentry = ebt_stp_mt_check,
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.matchsize = sizeof(struct ebt_stp_info),
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.me = THIS_MODULE,
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};
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static int __init ebt_stp_init(void)
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{
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return xt_register_match(&ebt_stp_mt_reg);
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}
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static void __exit ebt_stp_fini(void)
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{
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xt_unregister_match(&ebt_stp_mt_reg);
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}
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module_init(ebt_stp_init);
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module_exit(ebt_stp_fini);
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MODULE_DESCRIPTION("Ebtables: Spanning Tree Protocol packet match");
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MODULE_LICENSE("GPL");
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