stp.c

Go to the documentation of this file.

/*
 *  STP SAP demux
 *
 *  Copyright (c) 2008 Patrick McHardy <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  version 2 as published by the Free Software Foundation.
 */
#include <linux/mutex.h>
#include <linux/skbuff.h>
#include <linux/etherdevice.h>
#include <linux/llc.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <net/llc.h>
#include <net/llc_pdu.h>
#include <net/stp.h>

/* 01:80:c2:00:00:20 - 01:80:c2:00:00:2F */
#define GARP_ADDR_MIN   0x20
#define GARP_ADDR_MAX   0x2F
#define GARP_ADDR_RANGE (GARP_ADDR_MAX - GARP_ADDR_MIN)

static const struct stp_proto __rcu *garp_protos[GARP_ADDR_RANGE + 1] __read_mostly;
static const struct stp_proto __rcu *stp_proto __read_mostly;

static struct llc_sap *sap __read_mostly;
static unsigned int sap_registered;
static DEFINE_MUTEX(stp_proto_mutex);

/* Called under rcu_read_lock from LLC */
static int stp_pdu_rcv(struct sk_buff *skb, struct net_device *dev,
               struct packet_type *pt, struct net_device *orig_dev)
{
    const struct ethhdr *eh = eth_hdr(skb);
    const struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
    const struct stp_proto *proto;

    if (pdu->ssap != LLC_SAP_BSPAN ||
        pdu->dsap != LLC_SAP_BSPAN ||
        pdu->ctrl_1 != LLC_PDU_TYPE_U)
        goto err;

    if (eh->h_dest[5] >= GARP_ADDR_MIN && eh->h_dest[5] <= GARP_ADDR_MAX) {
        proto = rcu_dereference(garp_protos[eh->h_dest[5] -
                            GARP_ADDR_MIN]);
        if (proto &&
            !ether_addr_equal(eh->h_dest, proto->group_address))
            goto err;
    } else
        proto = rcu_dereference(stp_proto);

    if (!proto)
        goto err;

    proto->rcv(proto, skb, dev);
    return 0;

err:
    kfree_skb(skb);
    return 0;
}

int stp_proto_register(const struct stp_proto *proto)
{
    int err = 0;

    mutex_lock(&stp_proto_mutex);
    if (sap_registered++ == 0) {
        sap = llc_sap_open(LLC_SAP_BSPAN, stp_pdu_rcv);
        if (!sap) {
            err = -ENOMEM;
            goto out;
        }
    }
    if (is_zero_ether_addr(proto->group_address))
        rcu_assign_pointer(stp_proto, proto);
    else
        rcu_assign_pointer(garp_protos[proto->group_address[5] -
                           GARP_ADDR_MIN], proto);
out:
    mutex_unlock(&stp_proto_mutex);
    return err;
}
EXPORT_SYMBOL_GPL(stp_proto_register);

void stp_proto_unregister(const struct stp_proto *proto)
{
    mutex_lock(&stp_proto_mutex);
    if (is_zero_ether_addr(proto->group_address))
        RCU_INIT_POINTER(stp_proto, NULL);
    else
        RCU_INIT_POINTER(garp_protos[proto->group_address[5] -
                           GARP_ADDR_MIN], NULL);
    synchronize_rcu();

    if (--sap_registered == 0)
        llc_sap_put(sap);
    mutex_unlock(&stp_proto_mutex);
}
EXPORT_SYMBOL_GPL(stp_proto_unregister);

MODULE_LICENSE("GPL");