br_fdb.c

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/*
 *  Forwarding database
 *  Linux ethernet bridge
 *
 *  Authors:
 *  Lennert Buytenhek       <[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/kernel.h>
#include <linux/init.h>
#include <linux/rculist.h>
#include <linux/spinlock.h>
#include <linux/times.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/jhash.h>
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/atomic.h>
#include <asm/unaligned.h>
#include "br_private.h"

static struct kmem_cache *br_fdb_cache __read_mostly;
static int fdb_insert(struct net_bridge *br, struct net_bridge_port *source,
              const unsigned char *addr);
static void fdb_notify(struct net_bridge *br,
               const struct net_bridge_fdb_entry *, int);

static u32 fdb_salt __read_mostly;

int __init br_fdb_init(void)
{
    br_fdb_cache = kmem_cache_create("bridge_fdb_cache",
                     sizeof(struct net_bridge_fdb_entry),
                     0,
                     SLAB_HWCACHE_ALIGN, NULL);
    if (!br_fdb_cache)
        return -ENOMEM;

    get_random_bytes(&fdb_salt, sizeof(fdb_salt));
    return 0;
}

void br_fdb_fini(void)
{
    kmem_cache_destroy(br_fdb_cache);
}


/* if topology_changing then use forward_delay (default 15 sec)
 * otherwise keep longer (default 5 minutes)
 */
static inline unsigned long hold_time(const struct net_bridge *br)
{
    return br->topology_change ? br->forward_delay : br->ageing_time;
}

static inline int has_expired(const struct net_bridge *br,
                  const struct net_bridge_fdb_entry *fdb)
{
    return !fdb->is_static &&
        time_before_eq(fdb->updated + hold_time(br), jiffies);
}

static inline int br_mac_hash(const unsigned char *mac)
{
    /* use 1 byte of OUI cnd 3 bytes of NIC */
    u32 key = get_unaligned((u32 *)(mac + 2));
    return jhash_1word(key, fdb_salt) & (BR_HASH_SIZE - 1);
}

static void fdb_rcu_free(struct rcu_head *head)
{
    struct net_bridge_fdb_entry *ent
        = container_of(head, struct net_bridge_fdb_entry, rcu);
    kmem_cache_free(br_fdb_cache, ent);
}

static void fdb_delete(struct net_bridge *br, struct net_bridge_fdb_entry *f)
{
    hlist_del_rcu(&f->hlist);
    fdb_notify(br, f, RTM_DELNEIGH);
    call_rcu(&f->rcu, fdb_rcu_free);
}

void br_fdb_changeaddr(struct net_bridge_port *p, const unsigned char *newaddr)
{
    struct net_bridge *br = p->br;
    int i;

    spin_lock_bh(&br->hash_lock);

    /* Search all chains since old address/hash is unknown */
    for (i = 0; i < BR_HASH_SIZE; i++) {
        struct hlist_node *h;
        hlist_for_each(h, &br->hash[i]) {
            struct net_bridge_fdb_entry *f;

            f = hlist_entry(h, struct net_bridge_fdb_entry, hlist);
            if (f->dst == p && f->is_local) {
                /* maybe another port has same hw addr? */
                struct net_bridge_port *op;
                list_for_each_entry(op, &br->port_list, list) {
                    if (op != p &&
                        ether_addr_equal(op->dev->dev_addr,
                                 f->addr.addr)) {
                        f->dst = op;
                        goto insert;
                    }
                }

                /* delete old one */
                fdb_delete(br, f);
                goto insert;
            }
        }
    }
 insert:
    /* insert new address,  may fail if invalid address or dup. */
    fdb_insert(br, p, newaddr);

    spin_unlock_bh(&br->hash_lock);
}

void br_fdb_change_mac_address(struct net_bridge *br, const u8 *newaddr)
{
    struct net_bridge_fdb_entry *f;

    /* If old entry was unassociated with any port, then delete it. */
    f = __br_fdb_get(br, br->dev->dev_addr);
    if (f && f->is_local && !f->dst)
        fdb_delete(br, f);

    fdb_insert(br, NULL, newaddr);
}

void br_fdb_cleanup(unsigned long _data)
{
    struct net_bridge *br = (struct net_bridge *)_data;
    unsigned long delay = hold_time(br);
    unsigned long next_timer = jiffies + br->ageing_time;
    int i;

    spin_lock(&br->hash_lock);
    for (i = 0; i < BR_HASH_SIZE; i++) {
        struct net_bridge_fdb_entry *f;
        struct hlist_node *h, *n;

        hlist_for_each_entry_safe(f, h, n, &br->hash[i], hlist) {
            unsigned long this_timer;
            if (f->is_static)
                continue;
            this_timer = f->updated + delay;
            if (time_before_eq(this_timer, jiffies))
                fdb_delete(br, f);
            else if (time_before(this_timer, next_timer))
                next_timer = this_timer;
        }
    }
    spin_unlock(&br->hash_lock);

    mod_timer(&br->gc_timer, round_jiffies_up(next_timer));
}

/* Completely flush all dynamic entries in forwarding database.*/
void br_fdb_flush(struct net_bridge *br)
{
    int i;

    spin_lock_bh(&br->hash_lock);
    for (i = 0; i < BR_HASH_SIZE; i++) {
        struct net_bridge_fdb_entry *f;
        struct hlist_node *h, *n;
        hlist_for_each_entry_safe(f, h, n, &br->hash[i], hlist) {
            if (!f->is_static)
                fdb_delete(br, f);
        }
    }
    spin_unlock_bh(&br->hash_lock);
}

/* Flush all entries referring to a specific port.
 * if do_all is set also flush static entries
 */
void br_fdb_delete_by_port(struct net_bridge *br,
               const struct net_bridge_port *p,
               int do_all)
{
    int i;

    spin_lock_bh(&br->hash_lock);
    for (i = 0; i < BR_HASH_SIZE; i++) {
        struct hlist_node *h, *g;

        hlist_for_each_safe(h, g, &br->hash[i]) {
            struct net_bridge_fdb_entry *f
                = hlist_entry(h, struct net_bridge_fdb_entry, hlist);
            if (f->dst != p)
                continue;

            if (f->is_static && !do_all)
                continue;
            /*
             * if multiple ports all have the same device address
             * then when one port is deleted, assign
             * the local entry to other port
             */
            if (f->is_local) {
                struct net_bridge_port *op;
                list_for_each_entry(op, &br->port_list, list) {
                    if (op != p &&
                        ether_addr_equal(op->dev->dev_addr,
                                 f->addr.addr)) {
                        f->dst = op;
                        goto skip_delete;
                    }
                }
            }

            fdb_delete(br, f);
        skip_delete: ;
        }
    }
    spin_unlock_bh(&br->hash_lock);
}

/* No locking or refcounting, assumes caller has rcu_read_lock */
struct net_bridge_fdb_entry *__br_fdb_get(struct net_bridge *br,
                      const unsigned char *addr)
{
    struct hlist_node *h;
    struct net_bridge_fdb_entry *fdb;

    hlist_for_each_entry_rcu(fdb, h, &br->hash[br_mac_hash(addr)], hlist) {
        if (ether_addr_equal(fdb->addr.addr, addr)) {
            if (unlikely(has_expired(br, fdb)))
                break;
            return fdb;
        }
    }

    return NULL;
}

#if IS_ENABLED(CONFIG_ATM_LANE)
/* Interface used by ATM LANE hook to test
 * if an addr is on some other bridge port */
int br_fdb_test_addr(struct net_device *dev, unsigned char *addr)
{
    struct net_bridge_fdb_entry *fdb;
    struct net_bridge_port *port;
    int ret;

    rcu_read_lock();
    port = br_port_get_rcu(dev);
    if (!port)
        ret = 0;
    else {
        fdb = __br_fdb_get(port->br, addr);
        ret = fdb && fdb->dst && fdb->dst->dev != dev &&
            fdb->dst->state == BR_STATE_FORWARDING;
    }
    rcu_read_unlock();

    return ret;
}
#endif /* CONFIG_ATM_LANE */

/*
 * Fill buffer with forwarding table records in
 * the API format.
 */
int br_fdb_fillbuf(struct net_bridge *br, void *buf,
           unsigned long maxnum, unsigned long skip)
{
    struct __fdb_entry *fe = buf;
    int i, num = 0;
    struct hlist_node *h;
    struct net_bridge_fdb_entry *f;

    memset(buf, 0, maxnum*sizeof(struct __fdb_entry));

    rcu_read_lock();
    for (i = 0; i < BR_HASH_SIZE; i++) {
        hlist_for_each_entry_rcu(f, h, &br->hash[i], hlist) {
            if (num >= maxnum)
                goto out;

            if (has_expired(br, f))
                continue;

            /* ignore pseudo entry for local MAC address */
            if (!f->dst)
                continue;

            if (skip) {
                --skip;
                continue;
            }

            /* convert from internal format to API */
            memcpy(fe->mac_addr, f->addr.addr, ETH_ALEN);

            /* due to ABI compat need to split into hi/lo */
            fe->port_no = f->dst->port_no;
            fe->port_hi = f->dst->port_no >> 8;

            fe->is_local = f->is_local;
            if (!f->is_static)
                fe->ageing_timer_value = jiffies_delta_to_clock_t(jiffies - f->updated);
            ++fe;
            ++num;
        }
    }

 out:
    rcu_read_unlock();

    return num;
}

static struct net_bridge_fdb_entry *fdb_find(struct hlist_head *head,
                         const unsigned char *addr)
{
    struct hlist_node *h;
    struct net_bridge_fdb_entry *fdb;

    hlist_for_each_entry(fdb, h, head, hlist) {
        if (ether_addr_equal(fdb->addr.addr, addr))
            return fdb;
    }
    return NULL;
}

static struct net_bridge_fdb_entry *fdb_find_rcu(struct hlist_head *head,
                         const unsigned char *addr)
{
    struct hlist_node *h;
    struct net_bridge_fdb_entry *fdb;

    hlist_for_each_entry_rcu(fdb, h, head, hlist) {
        if (ether_addr_equal(fdb->addr.addr, addr))
            return fdb;
    }
    return NULL;
}

static struct net_bridge_fdb_entry *fdb_create(struct hlist_head *head,
                           struct net_bridge_port *source,
                           const unsigned char *addr)
{
    struct net_bridge_fdb_entry *fdb;

    fdb = kmem_cache_alloc(br_fdb_cache, GFP_ATOMIC);
    if (fdb) {
        memcpy(fdb->addr.addr, addr, ETH_ALEN);
        fdb->dst = source;
        fdb->is_local = 0;
        fdb->is_static = 0;
        fdb->updated = fdb->used = jiffies;
        hlist_add_head_rcu(&fdb->hlist, head);
    }
    return fdb;
}

static int fdb_insert(struct net_bridge *br, struct net_bridge_port *source,
          const unsigned char *addr)
{
    struct hlist_head *head = &br->hash[br_mac_hash(addr)];
    struct net_bridge_fdb_entry *fdb;

    if (!is_valid_ether_addr(addr))
        return -EINVAL;

    fdb = fdb_find(head, addr);
    if (fdb) {
        /* it is okay to have multiple ports with same
         * address, just use the first one.
         */
        if (fdb->is_local)
            return 0;
        br_warn(br, "adding interface %s with same address "
               "as a received packet\n",
               source->dev->name);
        fdb_delete(br, fdb);
    }

    fdb = fdb_create(head, source, addr);
    if (!fdb)
        return -ENOMEM;

    fdb->is_local = fdb->is_static = 1;
    fdb_notify(br, fdb, RTM_NEWNEIGH);
    return 0;
}

/* Add entry for local address of interface */
int br_fdb_insert(struct net_bridge *br, struct net_bridge_port *source,
          const unsigned char *addr)
{
    int ret;

    spin_lock_bh(&br->hash_lock);
    ret = fdb_insert(br, source, addr);
    spin_unlock_bh(&br->hash_lock);
    return ret;
}

void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
           const unsigned char *addr)
{
    struct hlist_head *head = &br->hash[br_mac_hash(addr)];
    struct net_bridge_fdb_entry *fdb;

    /* some users want to always flood. */
    if (hold_time(br) == 0)
        return;

    /* ignore packets unless we are using this port */
    if (!(source->state == BR_STATE_LEARNING ||
          source->state == BR_STATE_FORWARDING))
        return;

    fdb = fdb_find_rcu(head, addr);
    if (likely(fdb)) {
        /* attempt to update an entry for a local interface */
        if (unlikely(fdb->is_local)) {
            if (net_ratelimit())
                br_warn(br, "received packet on %s with "
                    "own address as source address\n",
                    source->dev->name);
        } else {
            /* fastpath: update of existing entry */
            fdb->dst = source;
            fdb->updated = jiffies;
        }
    } else {
        spin_lock(&br->hash_lock);
        if (likely(!fdb_find(head, addr))) {
            fdb = fdb_create(head, source, addr);
            if (fdb)
                fdb_notify(br, fdb, RTM_NEWNEIGH);
        }
        /* else  we lose race and someone else inserts
         * it first, don't bother updating
         */
        spin_unlock(&br->hash_lock);
    }
}

static int fdb_to_nud(const struct net_bridge_fdb_entry *fdb)
{
    if (fdb->is_local)
        return NUD_PERMANENT;
    else if (fdb->is_static)
        return NUD_NOARP;
    else if (has_expired(fdb->dst->br, fdb))
        return NUD_STALE;
    else
        return NUD_REACHABLE;
}

static int fdb_fill_info(struct sk_buff *skb, const struct net_bridge *br,
             const struct net_bridge_fdb_entry *fdb,
             u32 portid, u32 seq, int type, unsigned int flags)
{
    unsigned long now = jiffies;
    struct nda_cacheinfo ci;
    struct nlmsghdr *nlh;
    struct ndmsg *ndm;

    nlh = nlmsg_put(skb, portid, seq, type, sizeof(*ndm), flags);
    if (nlh == NULL)
        return -EMSGSIZE;

    ndm = nlmsg_data(nlh);
    ndm->ndm_family  = AF_BRIDGE;
    ndm->ndm_pad1    = 0;
    ndm->ndm_pad2    = 0;
    ndm->ndm_flags   = 0;
    ndm->ndm_type    = 0;
    ndm->ndm_ifindex = fdb->dst ? fdb->dst->dev->ifindex : br->dev->ifindex;
    ndm->ndm_state   = fdb_to_nud(fdb);

    if (nla_put(skb, NDA_LLADDR, ETH_ALEN, &fdb->addr))
        goto nla_put_failure;
    ci.ndm_used  = jiffies_to_clock_t(now - fdb->used);
    ci.ndm_confirmed = 0;
    ci.ndm_updated   = jiffies_to_clock_t(now - fdb->updated);
    ci.ndm_refcnt    = 0;
    if (nla_put(skb, NDA_CACHEINFO, sizeof(ci), &ci))
        goto nla_put_failure;
    return nlmsg_end(skb, nlh);

nla_put_failure:
    nlmsg_cancel(skb, nlh);
    return -EMSGSIZE;
}

static inline size_t fdb_nlmsg_size(void)
{
    return NLMSG_ALIGN(sizeof(struct ndmsg))
        + nla_total_size(ETH_ALEN) /* NDA_LLADDR */
        + nla_total_size(sizeof(struct nda_cacheinfo));
}

static void fdb_notify(struct net_bridge *br,
               const struct net_bridge_fdb_entry *fdb, int type)
{
    struct net *net = dev_net(br->dev);
    struct sk_buff *skb;
    int err = -ENOBUFS;

    skb = nlmsg_new(fdb_nlmsg_size(), GFP_ATOMIC);
    if (skb == NULL)
        goto errout;

    err = fdb_fill_info(skb, br, fdb, 0, 0, type, 0);
    if (err < 0) {
        /* -EMSGSIZE implies BUG in fdb_nlmsg_size() */
        WARN_ON(err == -EMSGSIZE);
        kfree_skb(skb);
        goto errout;
    }
    rtnl_notify(skb, net, 0, RTNLGRP_NEIGH, NULL, GFP_ATOMIC);
    return;
errout:
    if (err < 0)
        rtnl_set_sk_err(net, RTNLGRP_NEIGH, err);
}

/* Dump information about entries, in response to GETNEIGH */
int br_fdb_dump(struct sk_buff *skb,
        struct netlink_callback *cb,
        struct net_device *dev,
        int idx)
{
    struct net_bridge *br = netdev_priv(dev);
    int i;

    if (!(dev->priv_flags & IFF_EBRIDGE))
        goto out;

    for (i = 0; i < BR_HASH_SIZE; i++) {
        struct hlist_node *h;
        struct net_bridge_fdb_entry *f;

        hlist_for_each_entry_rcu(f, h, &br->hash[i], hlist) {
            if (idx < cb->args[0])
                goto skip;

            if (fdb_fill_info(skb, br, f,
                      NETLINK_CB(cb->skb).portid,
                      cb->nlh->nlmsg_seq,
                      RTM_NEWNEIGH,
                      NLM_F_MULTI) < 0)
                break;
skip:
            ++idx;
        }
    }

out:
    return idx;
}

/* Update (create or replace) forwarding database entry */
static int fdb_add_entry(struct net_bridge_port *source, const __u8 *addr,
             __u16 state, __u16 flags)
{
    struct net_bridge *br = source->br;
    struct hlist_head *head = &br->hash[br_mac_hash(addr)];
    struct net_bridge_fdb_entry *fdb;

    fdb = fdb_find(head, addr);
    if (fdb == NULL) {
        if (!(flags & NLM_F_CREATE))
            return -ENOENT;

        fdb = fdb_create(head, source, addr);
        if (!fdb)
            return -ENOMEM;
        fdb_notify(br, fdb, RTM_NEWNEIGH);
    } else {
        if (flags & NLM_F_EXCL)
            return -EEXIST;
    }

    if (fdb_to_nud(fdb) != state) {
        if (state & NUD_PERMANENT)
            fdb->is_local = fdb->is_static = 1;
        else if (state & NUD_NOARP) {
            fdb->is_local = 0;
            fdb->is_static = 1;
        } else
            fdb->is_local = fdb->is_static = 0;

        fdb->updated = fdb->used = jiffies;
        fdb_notify(br, fdb, RTM_NEWNEIGH);
    }

    return 0;
}

/* Add new permanent fdb entry with RTM_NEWNEIGH */
int br_fdb_add(struct ndmsg *ndm, struct nlattr *tb[],
           struct net_device *dev,
           const unsigned char *addr, u16 nlh_flags)
{
    struct net_bridge_port *p;
    int err = 0;

    if (!(ndm->ndm_state & (NUD_PERMANENT|NUD_NOARP|NUD_REACHABLE))) {
        pr_info("bridge: RTM_NEWNEIGH with invalid state %#x\n", ndm->ndm_state);
        return -EINVAL;
    }

    p = br_port_get_rtnl(dev);
    if (p == NULL) {
        pr_info("bridge: RTM_NEWNEIGH %s not a bridge port\n",
            dev->name);
        return -EINVAL;
    }

    if (ndm->ndm_flags & NTF_USE) {
        rcu_read_lock();
        br_fdb_update(p->br, p, addr);
        rcu_read_unlock();
    } else {
        spin_lock_bh(&p->br->hash_lock);
        err = fdb_add_entry(p, addr, ndm->ndm_state, nlh_flags);
        spin_unlock_bh(&p->br->hash_lock);
    }

    return err;
}

static int fdb_delete_by_addr(struct net_bridge_port *p, const u8 *addr)
{
    struct net_bridge *br = p->br;
    struct hlist_head *head = &br->hash[br_mac_hash(addr)];
    struct net_bridge_fdb_entry *fdb;

    fdb = fdb_find(head, addr);
    if (!fdb)
        return -ENOENT;

    fdb_delete(p->br, fdb);
    return 0;
}

/* Remove neighbor entry with RTM_DELNEIGH */
int br_fdb_delete(struct ndmsg *ndm, struct net_device *dev,
          const unsigned char *addr)
{
    struct net_bridge_port *p;
    int err;

    p = br_port_get_rtnl(dev);
    if (p == NULL) {
        pr_info("bridge: RTM_DELNEIGH %s not a bridge port\n",
            dev->name);
        return -EINVAL;
    }

    spin_lock_bh(&p->br->hash_lock);
    err = fdb_delete_by_addr(p, addr);
    spin_unlock_bh(&p->br->hash_lock);

    return err;
}