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* Bart De Schuymer <bdschuym@pandora.be>
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* Stephen Hemminger <shemminger@osdl.org>
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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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#define BPDU_TYPE_TCN 0x80
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struct stp_config_pdu {
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uint8_t hello_time[2];
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uint8_t forward_delay[2];
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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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const struct ebt_stp_config_info *c;
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if ((info->bitmask & EBT_STP_FLAGS) &&
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FWINV(c->flags != stpc->flags, EBT_STP_FLAGS))
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if (info->bitmask & EBT_STP_ROOTPRIO) {
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v16 = NR16(stpc->root);
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if (FWINV(v16 < c->root_priol ||
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v16 > c->root_priou, EBT_STP_ROOTPRIO))
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if (info->bitmask & EBT_STP_ROOTADDR) {
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for (i = 0; i < 6; i++)
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verdict |= (stpc->root[2+i] ^ c->root_addr[i]) &
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if (FWINV(verdict != 0, EBT_STP_ROOTADDR))
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if (info->bitmask & EBT_STP_ROOTCOST) {
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v32 = NR32(stpc->root_cost);
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if (FWINV(v32 < c->root_costl ||
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v32 > c->root_costu, EBT_STP_ROOTCOST))
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if (info->bitmask & EBT_STP_SENDERPRIO) {
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v16 = NR16(stpc->sender);
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if (FWINV(v16 < c->sender_priol ||
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v16 > c->sender_priou, EBT_STP_SENDERPRIO))
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if (info->bitmask & EBT_STP_SENDERADDR) {
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for (i = 0; i < 6; i++)
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verdict |= (stpc->sender[2+i] ^ c->sender_addr[i]) &
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if (FWINV(verdict != 0, EBT_STP_SENDERADDR))
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if (info->bitmask & EBT_STP_PORT) {
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v16 = NR16(stpc->port);
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if (FWINV(v16 < c->portl ||
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v16 > c->portu, EBT_STP_PORT))
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if (info->bitmask & EBT_STP_MSGAGE) {
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v16 = NR16(stpc->msg_age);
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if (FWINV(v16 < c->msg_agel ||
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v16 > c->msg_ageu, EBT_STP_MSGAGE))
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if (info->bitmask & EBT_STP_MAXAGE) {
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v16 = NR16(stpc->max_age);
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if (FWINV(v16 < c->max_agel ||
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v16 > c->max_ageu, EBT_STP_MAXAGE))
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if (info->bitmask & EBT_STP_HELLOTIME) {
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v16 = NR16(stpc->hello_time);
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if (FWINV(v16 < c->hello_timel ||
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v16 > c->hello_timeu, EBT_STP_HELLOTIME))
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if (info->bitmask & EBT_STP_FWDD) {
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v16 = NR16(stpc->forward_delay);
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if (FWINV(v16 < c->forward_delayl ||
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v16 > c->forward_delayu, EBT_STP_FWDD))
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ebt_stp_mt(const struct sk_buff *skb, struct xt_action_param *par)
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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 uint8_t 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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/* The stp code only considers these */
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if (memcmp(sp, header, sizeof(header)))
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if (info->bitmask & EBT_STP_TYPE &&
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FWINV(info->type != sp->type, EBT_STP_TYPE))
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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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return ebt_filter_config(info, st);
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static int ebt_stp_mt_check(const struct xt_mtchk_param *par)
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const struct ebt_stp_info *info = par->matchinfo;
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const uint8_t bridge_ula[6] = {0x01, 0x80, 0xc2, 0x00, 0x00, 0x00};
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const uint8_t msk[6] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
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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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/* Make sure the match only receives stp frames */
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if (compare_ether_addr(e->destmac, bridge_ula) ||
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compare_ether_addr(e->destmsk, msk) || !(e->bitmask & EBT_DESTMAC))
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static struct xt_match ebt_stp_mt_reg __read_mostly = {
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.family = NFPROTO_BRIDGE,
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.checkentry = ebt_stp_mt_check,
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.matchsize = sizeof(struct ebt_stp_info),
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static int __init ebt_stp_init(void)
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return xt_register_match(&ebt_stp_mt_reg);
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static void __exit ebt_stp_fini(void)
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xt_unregister_match(&ebt_stp_mt_reg);
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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");