br_sysfs_br.c

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/*
 *  Sysfs attributes of bridge ports
 *  Linux ethernet bridge
 *
 *  Authors:
 *  Stephen Hemminger       <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <linux/capability.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/if_bridge.h>
#include <linux/rtnetlink.h>
#include <linux/spinlock.h>
#include <linux/times.h>

#include "br_private.h"

#define to_dev(obj) container_of(obj, struct device, kobj)
#define to_bridge(cd)   ((struct net_bridge *)netdev_priv(to_net_dev(cd)))

/*
 * Common code for storing bridge parameters.
 */
static ssize_t store_bridge_parm(struct device *d,
                 const char *buf, size_t len,
                 int (*set)(struct net_bridge *, unsigned long))
{
    struct net_bridge *br = to_bridge(d);
    char *endp;
    unsigned long val;
    int err;

    if (!capable(CAP_NET_ADMIN))
        return -EPERM;

    val = simple_strtoul(buf, &endp, 0);
    if (endp == buf)
        return -EINVAL;

    err = (*set)(br, val);
    return err ? err : len;
}


static ssize_t show_forward_delay(struct device *d,
                  struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%lu\n", jiffies_to_clock_t(br->forward_delay));
}

static ssize_t store_forward_delay(struct device *d,
                   struct device_attribute *attr,
                   const char *buf, size_t len)
{
    return store_bridge_parm(d, buf, len, br_set_forward_delay);
}
static DEVICE_ATTR(forward_delay, S_IRUGO | S_IWUSR,
           show_forward_delay, store_forward_delay);

static ssize_t show_hello_time(struct device *d, struct device_attribute *attr,
                   char *buf)
{
    return sprintf(buf, "%lu\n",
               jiffies_to_clock_t(to_bridge(d)->hello_time));
}

static ssize_t store_hello_time(struct device *d,
                struct device_attribute *attr, const char *buf,
                size_t len)
{
    return store_bridge_parm(d, buf, len, br_set_hello_time);
}
static DEVICE_ATTR(hello_time, S_IRUGO | S_IWUSR, show_hello_time,
           store_hello_time);

static ssize_t show_max_age(struct device *d, struct device_attribute *attr,
                char *buf)
{
    return sprintf(buf, "%lu\n",
               jiffies_to_clock_t(to_bridge(d)->max_age));
}

static ssize_t store_max_age(struct device *d, struct device_attribute *attr,
                 const char *buf, size_t len)
{
    return store_bridge_parm(d, buf, len, br_set_max_age);
}
static DEVICE_ATTR(max_age, S_IRUGO | S_IWUSR, show_max_age, store_max_age);

static ssize_t show_ageing_time(struct device *d,
                struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%lu\n", jiffies_to_clock_t(br->ageing_time));
}

static int set_ageing_time(struct net_bridge *br, unsigned long val)
{
    br->ageing_time = clock_t_to_jiffies(val);
    return 0;
}

static ssize_t store_ageing_time(struct device *d,
                 struct device_attribute *attr,
                 const char *buf, size_t len)
{
    return store_bridge_parm(d, buf, len, set_ageing_time);
}
static DEVICE_ATTR(ageing_time, S_IRUGO | S_IWUSR, show_ageing_time,
           store_ageing_time);

static ssize_t show_stp_state(struct device *d,
                  struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%d\n", br->stp_enabled);
}


static ssize_t store_stp_state(struct device *d,
                   struct device_attribute *attr, const char *buf,
                   size_t len)
{
    struct net_bridge *br = to_bridge(d);
    char *endp;
    unsigned long val;

    if (!capable(CAP_NET_ADMIN))
        return -EPERM;

    val = simple_strtoul(buf, &endp, 0);
    if (endp == buf)
        return -EINVAL;

    if (!rtnl_trylock())
        return restart_syscall();
    br_stp_set_enabled(br, val);
    rtnl_unlock();

    return len;
}
static DEVICE_ATTR(stp_state, S_IRUGO | S_IWUSR, show_stp_state,
           store_stp_state);

static ssize_t show_group_fwd_mask(struct device *d,
                  struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%#x\n", br->group_fwd_mask);
}


static ssize_t store_group_fwd_mask(struct device *d,
                   struct device_attribute *attr, const char *buf,
                   size_t len)
{
    struct net_bridge *br = to_bridge(d);
    char *endp;
    unsigned long val;

    if (!capable(CAP_NET_ADMIN))
        return -EPERM;

    val = simple_strtoul(buf, &endp, 0);
    if (endp == buf)
        return -EINVAL;

    if (val & BR_GROUPFWD_RESTRICTED)
        return -EINVAL;

    br->group_fwd_mask = val;

    return len;
}
static DEVICE_ATTR(group_fwd_mask, S_IRUGO | S_IWUSR, show_group_fwd_mask,
           store_group_fwd_mask);

static ssize_t show_priority(struct device *d, struct device_attribute *attr,
                 char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%d\n",
               (br->bridge_id.prio[0] << 8) | br->bridge_id.prio[1]);
}

static int set_priority(struct net_bridge *br, unsigned long val)
{
    br_stp_set_bridge_priority(br, (u16) val);
    return 0;
}

static ssize_t store_priority(struct device *d, struct device_attribute *attr,
                   const char *buf, size_t len)
{
    return store_bridge_parm(d, buf, len, set_priority);
}
static DEVICE_ATTR(priority, S_IRUGO | S_IWUSR, show_priority, store_priority);

static ssize_t show_root_id(struct device *d, struct device_attribute *attr,
                char *buf)
{
    return br_show_bridge_id(buf, &to_bridge(d)->designated_root);
}
static DEVICE_ATTR(root_id, S_IRUGO, show_root_id, NULL);

static ssize_t show_bridge_id(struct device *d, struct device_attribute *attr,
                  char *buf)
{
    return br_show_bridge_id(buf, &to_bridge(d)->bridge_id);
}
static DEVICE_ATTR(bridge_id, S_IRUGO, show_bridge_id, NULL);

static ssize_t show_root_port(struct device *d, struct device_attribute *attr,
                  char *buf)
{
    return sprintf(buf, "%d\n", to_bridge(d)->root_port);
}
static DEVICE_ATTR(root_port, S_IRUGO, show_root_port, NULL);

static ssize_t show_root_path_cost(struct device *d,
                   struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "%d\n", to_bridge(d)->root_path_cost);
}
static DEVICE_ATTR(root_path_cost, S_IRUGO, show_root_path_cost, NULL);

static ssize_t show_topology_change(struct device *d,
                    struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "%d\n", to_bridge(d)->topology_change);
}
static DEVICE_ATTR(topology_change, S_IRUGO, show_topology_change, NULL);

static ssize_t show_topology_change_detected(struct device *d,
                         struct device_attribute *attr,
                         char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%d\n", br->topology_change_detected);
}
static DEVICE_ATTR(topology_change_detected, S_IRUGO,
           show_topology_change_detected, NULL);

static ssize_t show_hello_timer(struct device *d,
                struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%ld\n", br_timer_value(&br->hello_timer));
}
static DEVICE_ATTR(hello_timer, S_IRUGO, show_hello_timer, NULL);

static ssize_t show_tcn_timer(struct device *d, struct device_attribute *attr,
                  char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%ld\n", br_timer_value(&br->tcn_timer));
}
static DEVICE_ATTR(tcn_timer, S_IRUGO, show_tcn_timer, NULL);

static ssize_t show_topology_change_timer(struct device *d,
                      struct device_attribute *attr,
                      char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%ld\n", br_timer_value(&br->topology_change_timer));
}
static DEVICE_ATTR(topology_change_timer, S_IRUGO, show_topology_change_timer,
           NULL);

static ssize_t show_gc_timer(struct device *d, struct device_attribute *attr,
                 char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%ld\n", br_timer_value(&br->gc_timer));
}
static DEVICE_ATTR(gc_timer, S_IRUGO, show_gc_timer, NULL);

static ssize_t show_group_addr(struct device *d,
                   struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%x:%x:%x:%x:%x:%x\n",
               br->group_addr[0], br->group_addr[1],
               br->group_addr[2], br->group_addr[3],
               br->group_addr[4], br->group_addr[5]);
}

static ssize_t store_group_addr(struct device *d,
                struct device_attribute *attr,
                const char *buf, size_t len)
{
    struct net_bridge *br = to_bridge(d);
    unsigned int new_addr[6];
    int i;

    if (!capable(CAP_NET_ADMIN))
        return -EPERM;

    if (sscanf(buf, "%x:%x:%x:%x:%x:%x",
           &new_addr[0], &new_addr[1], &new_addr[2],
           &new_addr[3], &new_addr[4], &new_addr[5]) != 6)
        return -EINVAL;

    /* Must be 01:80:c2:00:00:0X */
    for (i = 0; i < 5; i++)
        if (new_addr[i] != br_group_address[i])
            return -EINVAL;

    if (new_addr[5] & ~0xf)
        return -EINVAL;

    if (new_addr[5] == 1 ||     /* 802.3x Pause address */
        new_addr[5] == 2 ||     /* 802.3ad Slow protocols */
        new_addr[5] == 3)       /* 802.1X PAE address */
        return -EINVAL;

    spin_lock_bh(&br->lock);
    for (i = 0; i < 6; i++)
        br->group_addr[i] = new_addr[i];
    spin_unlock_bh(&br->lock);
    return len;
}

static DEVICE_ATTR(group_addr, S_IRUGO | S_IWUSR,
           show_group_addr, store_group_addr);

static ssize_t store_flush(struct device *d,
               struct device_attribute *attr,
               const char *buf, size_t len)
{
    struct net_bridge *br = to_bridge(d);

    if (!capable(CAP_NET_ADMIN))
        return -EPERM;

    br_fdb_flush(br);
    return len;
}
static DEVICE_ATTR(flush, S_IWUSR, NULL, store_flush);

#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
static ssize_t show_multicast_router(struct device *d,
                     struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%d\n", br->multicast_router);
}

static ssize_t store_multicast_router(struct device *d,
                      struct device_attribute *attr,
                      const char *buf, size_t len)
{
    return store_bridge_parm(d, buf, len, br_multicast_set_router);
}
static DEVICE_ATTR(multicast_router, S_IRUGO | S_IWUSR, show_multicast_router,
           store_multicast_router);

static ssize_t show_multicast_snooping(struct device *d,
                       struct device_attribute *attr,
                       char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%d\n", !br->multicast_disabled);
}

static ssize_t store_multicast_snooping(struct device *d,
                    struct device_attribute *attr,
                    const char *buf, size_t len)
{
    return store_bridge_parm(d, buf, len, br_multicast_toggle);
}
static DEVICE_ATTR(multicast_snooping, S_IRUGO | S_IWUSR,
           show_multicast_snooping, store_multicast_snooping);

static ssize_t show_multicast_querier(struct device *d,
                      struct device_attribute *attr,
                      char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%d\n", br->multicast_querier);
}

static ssize_t store_multicast_querier(struct device *d,
                       struct device_attribute *attr,
                       const char *buf, size_t len)
{
    return store_bridge_parm(d, buf, len, br_multicast_set_querier);
}
static DEVICE_ATTR(multicast_querier, S_IRUGO | S_IWUSR,
           show_multicast_querier, store_multicast_querier);

static ssize_t show_hash_elasticity(struct device *d,
                    struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%u\n", br->hash_elasticity);
}

static int set_elasticity(struct net_bridge *br, unsigned long val)
{
    br->hash_elasticity = val;
    return 0;
}

static ssize_t store_hash_elasticity(struct device *d,
                     struct device_attribute *attr,
                     const char *buf, size_t len)
{
    return store_bridge_parm(d, buf, len, set_elasticity);
}
static DEVICE_ATTR(hash_elasticity, S_IRUGO | S_IWUSR, show_hash_elasticity,
           store_hash_elasticity);

static ssize_t show_hash_max(struct device *d, struct device_attribute *attr,
                 char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%u\n", br->hash_max);
}

static ssize_t store_hash_max(struct device *d, struct device_attribute *attr,
                  const char *buf, size_t len)
{
    return store_bridge_parm(d, buf, len, br_multicast_set_hash_max);
}
static DEVICE_ATTR(hash_max, S_IRUGO | S_IWUSR, show_hash_max,
           store_hash_max);

static ssize_t show_multicast_last_member_count(struct device *d,
                        struct device_attribute *attr,
                        char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%u\n", br->multicast_last_member_count);
}

static int set_last_member_count(struct net_bridge *br, unsigned long val)
{
    br->multicast_last_member_count = val;
    return 0;
}

static ssize_t store_multicast_last_member_count(struct device *d,
                         struct device_attribute *attr,
                         const char *buf, size_t len)
{
    return store_bridge_parm(d, buf, len, set_last_member_count);
}
static DEVICE_ATTR(multicast_last_member_count, S_IRUGO | S_IWUSR,
           show_multicast_last_member_count,
           store_multicast_last_member_count);

static ssize_t show_multicast_startup_query_count(
    struct device *d, struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%u\n", br->multicast_startup_query_count);
}

static int set_startup_query_count(struct net_bridge *br, unsigned long val)
{
    br->multicast_startup_query_count = val;
    return 0;
}

static ssize_t store_multicast_startup_query_count(
    struct device *d, struct device_attribute *attr, const char *buf,
    size_t len)
{
    return store_bridge_parm(d, buf, len, set_startup_query_count);
}
static DEVICE_ATTR(multicast_startup_query_count, S_IRUGO | S_IWUSR,
           show_multicast_startup_query_count,
           store_multicast_startup_query_count);

static ssize_t show_multicast_last_member_interval(
    struct device *d, struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%lu\n",
               jiffies_to_clock_t(br->multicast_last_member_interval));
}

static int set_last_member_interval(struct net_bridge *br, unsigned long val)
{
    br->multicast_last_member_interval = clock_t_to_jiffies(val);
    return 0;
}

static ssize_t store_multicast_last_member_interval(
    struct device *d, struct device_attribute *attr, const char *buf,
    size_t len)
{
    return store_bridge_parm(d, buf, len, set_last_member_interval);
}
static DEVICE_ATTR(multicast_last_member_interval, S_IRUGO | S_IWUSR,
           show_multicast_last_member_interval,
           store_multicast_last_member_interval);

static ssize_t show_multicast_membership_interval(
    struct device *d, struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%lu\n",
               jiffies_to_clock_t(br->multicast_membership_interval));
}

static int set_membership_interval(struct net_bridge *br, unsigned long val)
{
    br->multicast_membership_interval = clock_t_to_jiffies(val);
    return 0;
}

static ssize_t store_multicast_membership_interval(
    struct device *d, struct device_attribute *attr, const char *buf,
    size_t len)
{
    return store_bridge_parm(d, buf, len, set_membership_interval);
}
static DEVICE_ATTR(multicast_membership_interval, S_IRUGO | S_IWUSR,
           show_multicast_membership_interval,
           store_multicast_membership_interval);

static ssize_t show_multicast_querier_interval(struct device *d,
                           struct device_attribute *attr,
                           char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%lu\n",
               jiffies_to_clock_t(br->multicast_querier_interval));
}

static int set_querier_interval(struct net_bridge *br, unsigned long val)
{
    br->multicast_querier_interval = clock_t_to_jiffies(val);
    return 0;
}

static ssize_t store_multicast_querier_interval(struct device *d,
                        struct device_attribute *attr,
                        const char *buf, size_t len)
{
    return store_bridge_parm(d, buf, len, set_querier_interval);
}
static DEVICE_ATTR(multicast_querier_interval, S_IRUGO | S_IWUSR,
           show_multicast_querier_interval,
           store_multicast_querier_interval);

static ssize_t show_multicast_query_interval(struct device *d,
                         struct device_attribute *attr,
                         char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%lu\n",
               jiffies_to_clock_t(br->multicast_query_interval));
}

static int set_query_interval(struct net_bridge *br, unsigned long val)
{
    br->multicast_query_interval = clock_t_to_jiffies(val);
    return 0;
}

static ssize_t store_multicast_query_interval(struct device *d,
                          struct device_attribute *attr,
                          const char *buf, size_t len)
{
    return store_bridge_parm(d, buf, len, set_query_interval);
}
static DEVICE_ATTR(multicast_query_interval, S_IRUGO | S_IWUSR,
           show_multicast_query_interval,
           store_multicast_query_interval);

static ssize_t show_multicast_query_response_interval(
    struct device *d, struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(
        buf, "%lu\n",
        jiffies_to_clock_t(br->multicast_query_response_interval));
}

static int set_query_response_interval(struct net_bridge *br, unsigned long val)
{
    br->multicast_query_response_interval = clock_t_to_jiffies(val);
    return 0;
}

static ssize_t store_multicast_query_response_interval(
    struct device *d, struct device_attribute *attr, const char *buf,
    size_t len)
{
    return store_bridge_parm(d, buf, len, set_query_response_interval);
}
static DEVICE_ATTR(multicast_query_response_interval, S_IRUGO | S_IWUSR,
           show_multicast_query_response_interval,
           store_multicast_query_response_interval);

static ssize_t show_multicast_startup_query_interval(
    struct device *d, struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(
        buf, "%lu\n",
        jiffies_to_clock_t(br->multicast_startup_query_interval));
}

static int set_startup_query_interval(struct net_bridge *br, unsigned long val)
{
    br->multicast_startup_query_interval = clock_t_to_jiffies(val);
    return 0;
}

static ssize_t store_multicast_startup_query_interval(
    struct device *d, struct device_attribute *attr, const char *buf,
    size_t len)
{
    return store_bridge_parm(d, buf, len, set_startup_query_interval);
}
static DEVICE_ATTR(multicast_startup_query_interval, S_IRUGO | S_IWUSR,
           show_multicast_startup_query_interval,
           store_multicast_startup_query_interval);
#endif
#ifdef CONFIG_BRIDGE_NETFILTER
static ssize_t show_nf_call_iptables(
    struct device *d, struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%u\n", br->nf_call_iptables);
}

static int set_nf_call_iptables(struct net_bridge *br, unsigned long val)
{
    br->nf_call_iptables = val ? true : false;
    return 0;
}

static ssize_t store_nf_call_iptables(
    struct device *d, struct device_attribute *attr, const char *buf,
    size_t len)
{
    return store_bridge_parm(d, buf, len, set_nf_call_iptables);
}
static DEVICE_ATTR(nf_call_iptables, S_IRUGO | S_IWUSR,
           show_nf_call_iptables, store_nf_call_iptables);

static ssize_t show_nf_call_ip6tables(
    struct device *d, struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%u\n", br->nf_call_ip6tables);
}

static int set_nf_call_ip6tables(struct net_bridge *br, unsigned long val)
{
    br->nf_call_ip6tables = val ? true : false;
    return 0;
}

static ssize_t store_nf_call_ip6tables(
    struct device *d, struct device_attribute *attr, const char *buf,
    size_t len)
{
    return store_bridge_parm(d, buf, len, set_nf_call_ip6tables);
}
static DEVICE_ATTR(nf_call_ip6tables, S_IRUGO | S_IWUSR,
           show_nf_call_ip6tables, store_nf_call_ip6tables);

static ssize_t show_nf_call_arptables(
    struct device *d, struct device_attribute *attr, char *buf)
{
    struct net_bridge *br = to_bridge(d);
    return sprintf(buf, "%u\n", br->nf_call_arptables);
}

static int set_nf_call_arptables(struct net_bridge *br, unsigned long val)
{
    br->nf_call_arptables = val ? true : false;
    return 0;
}

static ssize_t store_nf_call_arptables(
    struct device *d, struct device_attribute *attr, const char *buf,
    size_t len)
{
    return store_bridge_parm(d, buf, len, set_nf_call_arptables);
}
static DEVICE_ATTR(nf_call_arptables, S_IRUGO | S_IWUSR,
           show_nf_call_arptables, store_nf_call_arptables);
#endif

static struct attribute *bridge_attrs[] = {
    &dev_attr_forward_delay.attr,
    &dev_attr_hello_time.attr,
    &dev_attr_max_age.attr,
    &dev_attr_ageing_time.attr,
    &dev_attr_stp_state.attr,
    &dev_attr_group_fwd_mask.attr,
    &dev_attr_priority.attr,
    &dev_attr_bridge_id.attr,
    &dev_attr_root_id.attr,
    &dev_attr_root_path_cost.attr,
    &dev_attr_root_port.attr,
    &dev_attr_topology_change.attr,
    &dev_attr_topology_change_detected.attr,
    &dev_attr_hello_timer.attr,
    &dev_attr_tcn_timer.attr,
    &dev_attr_topology_change_timer.attr,
    &dev_attr_gc_timer.attr,
    &dev_attr_group_addr.attr,
    &dev_attr_flush.attr,
#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
    &dev_attr_multicast_router.attr,
    &dev_attr_multicast_snooping.attr,
    &dev_attr_multicast_querier.attr,
    &dev_attr_hash_elasticity.attr,
    &dev_attr_hash_max.attr,
    &dev_attr_multicast_last_member_count.attr,
    &dev_attr_multicast_startup_query_count.attr,
    &dev_attr_multicast_last_member_interval.attr,
    &dev_attr_multicast_membership_interval.attr,
    &dev_attr_multicast_querier_interval.attr,
    &dev_attr_multicast_query_interval.attr,
    &dev_attr_multicast_query_response_interval.attr,
    &dev_attr_multicast_startup_query_interval.attr,
#endif
#ifdef CONFIG_BRIDGE_NETFILTER
    &dev_attr_nf_call_iptables.attr,
    &dev_attr_nf_call_ip6tables.attr,
    &dev_attr_nf_call_arptables.attr,
#endif
    NULL
};

static struct attribute_group bridge_group = {
    .name = SYSFS_BRIDGE_ATTR,
    .attrs = bridge_attrs,
};

/*
 * Export the forwarding information table as a binary file
 * The records are struct __fdb_entry.
 *
 * Returns the number of bytes read.
 */
static ssize_t brforward_read(struct file *filp, struct kobject *kobj,
                  struct bin_attribute *bin_attr,
                  char *buf, loff_t off, size_t count)
{
    struct device *dev = to_dev(kobj);
    struct net_bridge *br = to_bridge(dev);
    int n;

    /* must read whole records */
    if (off % sizeof(struct __fdb_entry) != 0)
        return -EINVAL;

    n =  br_fdb_fillbuf(br, buf,
                count / sizeof(struct __fdb_entry),
                off / sizeof(struct __fdb_entry));

    if (n > 0)
        n *= sizeof(struct __fdb_entry);

    return n;
}

static struct bin_attribute bridge_forward = {
    .attr = { .name = SYSFS_BRIDGE_FDB,
          .mode = S_IRUGO, },
    .read = brforward_read,
};

/*
 * Add entries in sysfs onto the existing network class device
 * for the bridge.
 *   Adds a attribute group "bridge" containing tuning parameters.
 *   Binary attribute containing the forward table
 *   Sub directory to hold links to interfaces.
 *
 * Note: the ifobj exists only to be a subdirectory
 *   to hold links.  The ifobj exists in same data structure
 *   as it's parent the bridge so reference counting works.
 */
int br_sysfs_addbr(struct net_device *dev)
{
    struct kobject *brobj = &dev->dev.kobj;
    struct net_bridge *br = netdev_priv(dev);
    int err;

    err = sysfs_create_group(brobj, &bridge_group);
    if (err) {
        pr_info("%s: can't create group %s/%s\n",
            __func__, dev->name, bridge_group.name);
        goto out1;
    }

    err = sysfs_create_bin_file(brobj, &bridge_forward);
    if (err) {
        pr_info("%s: can't create attribute file %s/%s\n",
            __func__, dev->name, bridge_forward.attr.name);
        goto out2;
    }

    br->ifobj = kobject_create_and_add(SYSFS_BRIDGE_PORT_SUBDIR, brobj);
    if (!br->ifobj) {
        pr_info("%s: can't add kobject (directory) %s/%s\n",
            __func__, dev->name, SYSFS_BRIDGE_PORT_SUBDIR);
        goto out3;
    }
    return 0;
 out3:
    sysfs_remove_bin_file(&dev->dev.kobj, &bridge_forward);
 out2:
    sysfs_remove_group(&dev->dev.kobj, &bridge_group);
 out1:
    return err;

}

void br_sysfs_delbr(struct net_device *dev)
{
    struct kobject *kobj = &dev->dev.kobj;
    struct net_bridge *br = netdev_priv(dev);

    kobject_put(br->ifobj);
    sysfs_remove_bin_file(kobj, &bridge_forward);
    sysfs_remove_group(kobj, &bridge_group);
}