root/net/bridge/netfilter/ebt_stp.c

DEFINITIONS

1. ebt_filter_config
2. ebt_stp_mt
3. ebt_stp_mt_check
4. ebt_stp_init
5. ebt_stp_fini

/*
 *  ebt_stp
 *
 *      Authors:
 *      Bart De Schuymer <bdschuym@pandora.be>
 *      Stephen Hemminger <shemminger@osdl.org>
 *
 *  July, 2003
 */
#include <linux/etherdevice.h>
#include <linux/module.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_stp.h>

#define BPDU_TYPE_CONFIG 0
#define BPDU_TYPE_TCN 0x80

struct stp_header {
        uint8_t dsap;
        uint8_t ssap;
        uint8_t ctrl;
        uint8_t pid;
        uint8_t vers;
        uint8_t type;
};

struct stp_config_pdu {
        uint8_t flags;
        uint8_t root[8];
        uint8_t root_cost[4];
        uint8_t sender[8];
        uint8_t port[2];
        uint8_t msg_age[2];
        uint8_t max_age[2];
        uint8_t hello_time[2];
        uint8_t forward_delay[2];
};

#define NR16(p) (p[0] << 8 | p[1])
#define NR32(p) ((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3])

static bool ebt_filter_config(const struct ebt_stp_info *info,
   const struct stp_config_pdu *stpc)
{
        const struct ebt_stp_config_info *c;
        uint16_t v16;
        uint32_t v32;
        int verdict, i;

        c = &info->config;
        if ((info->bitmask & EBT_STP_FLAGS) &&
            FWINV(c->flags != stpc->flags, EBT_STP_FLAGS))
                return false;
        if (info->bitmask & EBT_STP_ROOTPRIO) {
                v16 = NR16(stpc->root);
                if (FWINV(v16 < c->root_priol ||
                    v16 > c->root_priou, EBT_STP_ROOTPRIO))
                        return false;
        }
        if (info->bitmask & EBT_STP_ROOTADDR) {
                verdict = 0;
                for (i = 0; i < 6; i++)
                        verdict |= (stpc->root[2+i] ^ c->root_addr[i]) &
                                   c->root_addrmsk[i];
                if (FWINV(verdict != 0, EBT_STP_ROOTADDR))
                        return false;
        }
        if (info->bitmask & EBT_STP_ROOTCOST) {
                v32 = NR32(stpc->root_cost);
                if (FWINV(v32 < c->root_costl ||
                    v32 > c->root_costu, EBT_STP_ROOTCOST))
                        return false;
        }
        if (info->bitmask & EBT_STP_SENDERPRIO) {
                v16 = NR16(stpc->sender);
                if (FWINV(v16 < c->sender_priol ||
                    v16 > c->sender_priou, EBT_STP_SENDERPRIO))
                        return false;
        }
        if (info->bitmask & EBT_STP_SENDERADDR) {
                verdict = 0;
                for (i = 0; i < 6; i++)
                        verdict |= (stpc->sender[2+i] ^ c->sender_addr[i]) &
                                   c->sender_addrmsk[i];
                if (FWINV(verdict != 0, EBT_STP_SENDERADDR))
                        return false;
        }
        if (info->bitmask & EBT_STP_PORT) {
                v16 = NR16(stpc->port);
                if (FWINV(v16 < c->portl ||
                    v16 > c->portu, EBT_STP_PORT))
                        return false;
        }
        if (info->bitmask & EBT_STP_MSGAGE) {
                v16 = NR16(stpc->msg_age);
                if (FWINV(v16 < c->msg_agel ||
                    v16 > c->msg_ageu, EBT_STP_MSGAGE))
                        return false;
        }
        if (info->bitmask & EBT_STP_MAXAGE) {
                v16 = NR16(stpc->max_age);
                if (FWINV(v16 < c->max_agel ||
                    v16 > c->max_ageu, EBT_STP_MAXAGE))
                        return false;
        }
        if (info->bitmask & EBT_STP_HELLOTIME) {
                v16 = NR16(stpc->hello_time);
                if (FWINV(v16 < c->hello_timel ||
                    v16 > c->hello_timeu, EBT_STP_HELLOTIME))
                        return false;
        }
        if (info->bitmask & EBT_STP_FWDD) {
                v16 = NR16(stpc->forward_delay);
                if (FWINV(v16 < c->forward_delayl ||
                    v16 > c->forward_delayu, EBT_STP_FWDD))
                        return false;
        }
        return true;
}

static bool
ebt_stp_mt(const struct sk_buff *skb, const struct xt_match_param *par)
{
        const struct ebt_stp_info *info = par->matchinfo;
        const struct stp_header *sp;
        struct stp_header _stph;
        const uint8_t header[6] = {0x42, 0x42, 0x03, 0x00, 0x00, 0x00};

        sp = skb_header_pointer(skb, 0, sizeof(_stph), &_stph);
        if (sp == NULL)
                return false;

        /* The stp code only considers these */
        if (memcmp(sp, header, sizeof(header)))
                return false;

        if (info->bitmask & EBT_STP_TYPE
            && FWINV(info->type != sp->type, EBT_STP_TYPE))
                return false;

        if (sp->type == BPDU_TYPE_CONFIG &&
            info->bitmask & EBT_STP_CONFIG_MASK) {
                const struct stp_config_pdu *st;
                struct stp_config_pdu _stpc;

                st = skb_header_pointer(skb, sizeof(_stph),
                                        sizeof(_stpc), &_stpc);
                if (st == NULL)
                        return false;
                return ebt_filter_config(info, st);
        }
        return true;
}

static bool ebt_stp_mt_check(const struct xt_mtchk_param *par)
{
        const struct ebt_stp_info *info = par->matchinfo;
        const uint8_t bridge_ula[6] = {0x01, 0x80, 0xc2, 0x00, 0x00, 0x00};
        const uint8_t msk[6] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
        const struct ebt_entry *e = par->entryinfo;

        if (info->bitmask & ~EBT_STP_MASK || info->invflags & ~EBT_STP_MASK ||
            !(info->bitmask & EBT_STP_MASK))
                return false;
        /* Make sure the match only receives stp frames */
        if (compare_ether_addr(e->destmac, bridge_ula) ||
            compare_ether_addr(e->destmsk, msk) || !(e->bitmask & EBT_DESTMAC))
                return false;

        return true;
}

static struct xt_match ebt_stp_mt_reg __read_mostly = {
        .name           = "stp",
        .revision       = 0,
        .family         = NFPROTO_BRIDGE,
        .match          = ebt_stp_mt,
        .checkentry     = ebt_stp_mt_check,
        .matchsize      = XT_ALIGN(sizeof(struct ebt_stp_info)),
        .me             = THIS_MODULE,
};

static int __init ebt_stp_init(void)
{
        return xt_register_match(&ebt_stp_mt_reg);
}

static void __exit ebt_stp_fini(void)
{
        xt_unregister_match(&ebt_stp_mt_reg);
}

module_init(ebt_stp_init);
module_exit(ebt_stp_fini);
MODULE_DESCRIPTION("Ebtables: Spanning Tree Protocol packet match");
MODULE_LICENSE("GPL");