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[/] [or1k/] [trunk/] [rc203soc/] [sw/] [uClinux/] [net/] [ipv4/] [arp.c] - Blame information for rev 1629

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/* linux/net/inet/arp.c
 *
 * Copyright (C) 1994 by Florian  La Roche
 *
 * This module implements the Address Resolution Protocol ARP (RFC 826),
 * which is used to convert IP addresses (or in the future maybe other
 * high-level addresses) into a low-level hardware address (like an Ethernet
 * address).
 *
 * FIXME:
 *      Experiment with better retransmit timers
 *      Clean up the timer deletions
 *      If you create a proxy entry, set your interface address to the address
 *      and then delete it, proxies may get out of sync with reality -
 *      check this.
 *
 * 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.
 *
 * Fixes:
 *              Alan Cox        :       Removed the ethernet assumptions in
 *                                      Florian's code
 *              Alan Cox        :       Fixed some small errors in the ARP
 *                                      logic
 *              Alan Cox        :       Allow >4K in /proc
 *              Alan Cox        :       Make ARP add its own protocol entry
 *              Ross Martin     :       Rewrote arp_rcv() and arp_get_info()
 *              Stephen Henson  :       Add AX25 support to arp_get_info()
 *              Alan Cox        :       Drop data when a device is downed.
 *              Alan Cox        :       Use init_timer().
 *              Alan Cox        :       Double lock fixes.
 *              Martin Seine    :       Move the arphdr structure
 *                                      to if_arp.h for compatibility.
 *                                      with BSD based programs.
 *              Andrew Tridgell :       Added ARP netmask code and
 *                                      re-arranged proxy handling.
 *              Alan Cox        :       Changed to use notifiers.
 *              Niibe Yutaka    :       Reply for this device or proxies only.
 *              Alan Cox        :       Don't proxy across hardware types!
 *              Jonathan Naylor :       Added support for NET/ROM.
 *              Mike Shaver     :       RFC1122 checks.
 *              Jonathan Naylor :       Only lookup the hardware address for
 *                                      the correct hardware type.
 *              Germano Caronni :       Assorted subtle races.
 *              Craig Schlenter :       Don't modify permanent entry
 *                                      during arp_rcv.
 *              Russ Nelson     :       Tidied up a few bits.
 *              Alexey Kuznetsov:       Major changes to caching and behaviour,
 *                                      eg intelligent arp probing and
 *                                      generation
 *                                      of host down events.
 *              Alan Cox        :       Missing unlock in device events.
 *              Eckes           :       ARP ioctl control errors.
 *              Alexey Kuznetsov:       Arp free fix.
 *              Manuel Rodriguez:       Gratuitous ARP.
 *              Jonathan Layes  :       Added arpd support through kerneld
 *                                      message queue (960314)
 *              Mike Shaver     :       /proc/sys/net/ipv4/arp_* support
 *              Stuart Cheshire :       Metricom and grat arp fixes
 *                                      *** FOR 2.1 clean this up ***
 *              Lawrence V. Stefani: (08/12/96) Added FDDI support.
 *              David S. Miller :       Fix skb leakage in arp_find.
 */
 
/* RFC1122 Status:
   2.3.2.1 (ARP Cache Validation):
     MUST provide mechanism to flush stale cache entries (OK)
     SHOULD be able to configure cache timeout (OK)
     MUST throttle ARP retransmits (OK)
   2.3.2.2 (ARP Packet Queue):
     SHOULD save at least one packet from each "conversation" with an
       unresolved IP address.  (OK)
   950727 -- MS
*/
 
#include <linux/types.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/config.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/errno.h>
#include <linux/in.h>
#include <linux/mm.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/fddidevice.h>
#include <linux/if_arp.h>
#include <linux/trdevice.h>
#include <linux/skbuff.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
 
#include <net/ip.h>
#include <net/icmp.h>
#include <net/route.h>
#include <net/protocol.h>
#include <net/tcp.h>
#include <net/sock.h>
#include <net/arp.h>
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
#include <net/ax25.h>
#if defined(CONFIG_NETROM) || defined(CONFIG_NETROM_MODULE)
#include <net/netrom.h>
#endif
#endif
#ifdef CONFIG_NET_ALIAS
#include <linux/net_alias.h>
#endif
#ifdef CONFIG_ARPD
#include <net/netlink.h>
#endif
 
#include <asm/system.h>
#include <asm/segment.h>
 
#include <stdarg.h>
 
/*
 *      Configurable Parameters
 */
 
/*
 *      After that time, an unused entry is deleted from the arp table.
 *      RFC1122 recommends set it to 60*HZ, if your site uses proxy arp
 *      and dynamic routing.
 */
 
#define ARP_TIMEOUT             (60*HZ)
 
int sysctl_arp_timeout = ARP_TIMEOUT;
 
/*
 *      How often is ARP cache checked for expire.
 *      It is useless to set ARP_CHECK_INTERVAL > ARP_TIMEOUT
 */
 
#define ARP_CHECK_INTERVAL      (60*HZ)
 
int sysctl_arp_check_interval = ARP_CHECK_INTERVAL;
 
/*
 *      Soft limit on ARP cache size.
 *      Note that this number should be greater than
 *      number of simultaneously opened sockets, or else
 *      hardware header cache will not be efficient.
 */
 
#if RT_CACHE_DEBUG >= 2
#define ARP_MAXSIZE     4
#else
#ifdef CONFIG_ARPD
#define ARP_MAXSIZE     64
#else
#define ARP_MAXSIZE     256
#endif /* CONFIG_ARPD */
#endif
 
/*
 *      If an arp request is send, ARP_RES_TIME is the timeout value until the
 *      next request is send.
 *      RFC1122: OK.  Throttles ARPing, as per 2.3.2.1. (MUST)
 *      The recommended minimum timeout is 1 second per destination.
 *
 */
 
#define ARP_RES_TIME            (5*HZ)
 
int sysctl_arp_res_time = ARP_RES_TIME;
 
/*
 *      The number of times an broadcast arp request is send, until
 *      the host is considered temporarily unreachable.
 */
 
#define ARP_MAX_TRIES           3
 
int sysctl_arp_max_tries = ARP_MAX_TRIES;
 
/*
 *      The entry is reconfirmed by sending point-to-point ARP
 *      request after ARP_CONFIRM_INTERVAL.
 *      RFC1122 recommends 60*HZ.
 *
 *      Warning: there exist nodes, that answer only broadcast
 *      ARP requests (Cisco-4000 in hot standby mode?)
 *      Now arp code should work with such nodes, but
 *      it still will generate redundant broadcast requests, so that
 *      this interval should be enough long.
 */
 
#define ARP_CONFIRM_INTERVAL    (300*HZ)
 
int sysctl_arp_confirm_interval = ARP_CONFIRM_INTERVAL;
 
/*
 *      We wait for answer to unicast request for ARP_CONFIRM_TIMEOUT.
 */
 
#define ARP_CONFIRM_TIMEOUT     ARP_RES_TIME
 
int sysctl_arp_confirm_timeout = ARP_CONFIRM_TIMEOUT;
 
/*
 *      The number of times an unicast arp request is retried, until
 *      the cache entry is considered suspicious.
 *      Value 0 means that no unicast pings will be sent.
 *      RFC1122 recommends 2.
 */
 
#define ARP_MAX_PINGS           1
 
int sysctl_arp_max_pings = ARP_MAX_PINGS;
 
/*
 *      When a host is dead, but someone tries to connect it,
 *      we do not remove corresponding cache entry (it would
 *      be useless, it will be created again immediately)
 *      Instead we prolongate interval between broadcasts
 *      to ARP_DEAD_RES_TIME.
 *      This interval should be not very long.
 *      (When the host will be up again, we will notice it only
 *      when ARP_DEAD_RES_TIME expires, or when the host will arp us.
 */
 
#define ARP_DEAD_RES_TIME       (60*HZ)
 
int sysctl_arp_dead_res_time = ARP_DEAD_RES_TIME;
 
/*
 *      This structure defines the ARP mapping cache.
 */
 
struct arp_table
{
        struct arp_table                *next;                  /* Linked entry list            */
        unsigned long                   last_used;              /* For expiry                   */
        unsigned long                   last_updated;           /* For expiry                   */
        unsigned int                    flags;                  /* Control status               */
        u32                             ip;                     /* ip address of entry          */
        u32                             mask;                   /* netmask - used for generalised proxy arps (tridge)           */
        unsigned char                   ha[MAX_ADDR_LEN];       /* Hardware address             */
        struct device                   *dev;                   /* Device the entry is tied to  */
        struct hh_cache                 *hh;                    /* Hardware headers chain       */
 
        /*
         *      The following entries are only used for unresolved hw addresses.
         */
 
        struct timer_list               timer;                  /* expire timer                 */
        int                             retries;                /* remaining retries            */
        struct sk_buff_head             skb;                    /* list of queued packets       */
};
 
 
static atomic_t arp_size = 0;
 
#ifdef CONFIG_ARPD
static int arpd_not_running;
static int arpd_stamp;
#endif
 
static unsigned int arp_bh_mask;
 
#define ARP_BH_BACKLOG  1
 
/*
 *      Backlog for ARP updates.
 */
static struct arp_table *arp_backlog;
 
/*
 *      Backlog for incomplete entries.
 */
static struct arp_table *arp_req_backlog;
 
 
static void arp_run_bh(void);
static void arp_check_expire (unsigned long);
static int  arp_update (u32 sip, char *sha, struct device * dev,
            unsigned long updated, struct arp_table *ientry, int grat);
 
static struct timer_list arp_timer =
        { NULL, NULL, ARP_CHECK_INTERVAL, 0L, &arp_check_expire };
 
/*
 * The default arp netmask is just 255.255.255.255 which means it's
 * a single machine entry. Only proxy entries can have other netmasks
 */
 
#define DEF_ARP_NETMASK (~0)
 
/*
 *      The size of the hash table. Must be a power of two.
 */
 
#define ARP_TABLE_SIZE          16
#define FULL_ARP_TABLE_SIZE     (ARP_TABLE_SIZE+1)
 
struct arp_table *arp_tables[FULL_ARP_TABLE_SIZE] =
{
        NULL,
};
 
#define arp_proxy_list arp_tables[ARP_TABLE_SIZE]
 
/*
 *      The last bits in the IP address are used for the cache lookup.
 *      A special entry is used for proxy arp entries
 */
 
#define HASH(paddr)             (htonl(paddr) & (ARP_TABLE_SIZE - 1))
 
/*
 *      ARP cache semaphore.
 *
 *      Every time when someone wants to traverse arp table,
 *      he MUST call arp_fast_lock.
 *      It will guarantee that arp cache list will not change
 *      by interrupts and the entry that you found will not
 *      disappear unexpectedly.
 *
 *      If you want to modify arp cache lists, you MUST
 *      call arp_fast_lock, and check that you are the only
 *      owner of semaphore (arp_lock == 1). If it is not the case
 *      you can defer your operation or forgot it,
 *      but DO NOT TOUCH lists.
 *
 *      However, you are allowed to change arp entry contents.
 *
 *      Assumptions:
 *           -- interrupt code MUST have lock/unlock balanced,
 *              you cannot lock cache on interrupt and defer unlocking
 *              to callback.
 *              In particular, it means that lock/unlock are allowed
 *              to be non-atomic. They are made atomic, but it was not
 *              necessary.
 *           -- nobody is allowed to sleep while
 *              it keeps arp locked. (route cache has similar locking
 *              scheme, but allows sleeping)
 *
 */
 
static atomic_t arp_lock;
 
#define ARP_LOCKED() (arp_lock != 1)
 
static __inline__ void arp_fast_lock(void)
{
        atomic_inc(&arp_lock);
}
 
static __inline__ void arp_unlock(void)
{
        if (atomic_dec_and_test(&arp_lock) && arp_bh_mask)
                arp_run_bh();
}
 
/*
 * Enqueue to FIFO list.
 */
 
static void arp_enqueue(struct arp_table **q, struct arp_table *entry)
{
        unsigned long flags;
        struct arp_table * tail;
 
        save_flags(flags);
        cli();
        tail = *q;
        if (!tail)
                entry->next = entry;
        else
        {
                entry->next = tail->next;
                tail->next = entry;
        }
        *q = entry;
        restore_flags(flags);
        return;
}
 
/*
 * Dequeue from FIFO list,
 * caller should mask interrupts.
 */
 
static struct arp_table * arp_dequeue(struct arp_table **q)
{
        struct arp_table * entry;
 
        if (*q)
        {
                entry = (*q)->next;
                (*q)->next = entry->next;
                if (entry->next == entry)
                        *q = NULL;
                entry->next = NULL;
                return entry;
        }
        return NULL;
}
 
/*
 * Purge all linked skb's of the entry.
 */
 
static void arp_purge_send_q(struct arp_table *entry)
{
        struct sk_buff *skb;
        unsigned long flags;
 
        save_flags(flags);
        cli();
        /* Release the list of `skb' pointers. */
        while ((skb = skb_dequeue(&entry->skb)) != NULL)
        {
                skb_device_lock(skb);
                restore_flags(flags);
                dev_kfree_skb(skb, FREE_WRITE);
                cli();
        }
        restore_flags(flags);
        return;
}
 
/*
 *      Release the entry and all resources linked to it: skb's, hh's, timer
 *      and certainly memory.
 *      The entry should be already removed from lists.
 */
 
static void arp_free_entry(struct arp_table *entry)
{
        unsigned long flags;
        struct hh_cache *hh, *next;
 
        del_timer(&entry->timer);
        arp_purge_send_q(entry);
 
        save_flags(flags);
        cli();
        hh = entry->hh;
        entry->hh = NULL;
        restore_flags(flags);
 
        for ( ; hh; hh = next)
        {
                next = hh->hh_next;
                hh->hh_uptodate = 0;
                hh->hh_next = NULL;
                hh->hh_arp = NULL;
                if (atomic_dec_and_test(&hh->hh_refcnt))
                        kfree_s(hh, sizeof(struct(struct hh_cache)));
        }
 
        kfree_s(entry, sizeof(struct arp_table));
        atomic_dec(&arp_size);
        return;
}
 
/*
 *      Hardware header cache.
 *
 *      BEWARE! Hardware header cache has no locking, so that
 *      it requires especially careful handling.
 *      It is the only part of arp+route, where a list
 *      should be traversed with masked interrupts.
 *      Luckily, this list contains one element 8), as rule.
 */
 
/*
 *      How many users has this entry?
 *      The answer is reliable only when interrupts are masked.
 */
 
static __inline__ int arp_count_hhs(struct arp_table * entry)
{
        struct hh_cache *hh;
        int count = 0;
 
        for (hh = entry->hh; hh; hh = hh->hh_next)
                count += hh->hh_refcnt-1;
 
        return count;
}
 
/*
 * Signal to device layer, that hardware address may be changed.
 */
 
static __inline__ void arp_update_hhs(struct arp_table * entry)
{
        struct hh_cache *hh;
 
        for (hh=entry->hh; hh; hh=hh->hh_next)
                entry->dev->header_cache_update(hh, entry->dev, entry->ha);
}
 
/*
 *      Invalidate all hh's, so that higher level will not try to use it.
 */
 
static __inline__ void arp_invalidate_hhs(struct arp_table * entry)
{
        struct hh_cache *hh;
 
        for (hh=entry->hh; hh; hh=hh->hh_next)
                hh->hh_uptodate = 0;
}
 
/*
 *      Atomic attaching new hh entry.
 *      Return 1, if entry has been freed, rather than attached.
 */
 
static int arp_set_hh(struct hh_cache **hhp, struct hh_cache *hh)
{
        unsigned long flags;
        struct hh_cache *hh1;
        struct arp_table *entry;
 
        atomic_inc(&hh->hh_refcnt);
 
        save_flags(flags);
        cli();
        if ((hh1 = *hhp) == NULL)
        {
                *hhp = hh;
                restore_flags(flags);
                return 0;
        }
 
        entry = (struct arp_table*)hh->hh_arp;
 
        /*
         *      An hh1 entry is already attached to this point.
         *      Is it not linked to arp entry? Link it!
         */
        if (!hh1->hh_arp && entry)
        {
                atomic_inc(&hh1->hh_refcnt);
                hh1->hh_next = entry->hh;
                entry->hh = hh1;
                hh1->hh_arp = (void*)entry;
                restore_flags(flags);
 
                if (entry->flags & ATF_COM)
                        entry->dev->header_cache_update(hh1, entry->dev, entry->ha);
#if RT_CACHE_DEBUG >= 1
                printk("arp_set_hh: %08x is reattached. Good!\n", entry->ip);
#endif
        }
#if RT_CACHE_DEBUG >= 1
        else if (entry)
                printk("arp_set_hh: %08x rr1 ok!\n", entry->ip);
#endif
        restore_flags(flags);
        if (atomic_dec_and_test(&hh->hh_refcnt))
                kfree_s(hh, sizeof(struct hh_cache));
        return 1;
}
 
static __inline__ struct hh_cache * arp_alloc_hh(int htype)
{
        struct hh_cache *hh;
        hh = kmalloc(sizeof(struct hh_cache), GFP_ATOMIC);
        if (hh)
        {
                memset(hh, 0, sizeof(struct hh_cache));
                hh->hh_type = htype;
        }
        return hh;
}
 
/*
 * Test if a hardware address is all zero
 */
 
static __inline__ int empty(unsigned char * addr, int len)
{
        while (len > 0)
        {
                if (*addr)
                        return 0;
                len--;
                addr++;
        }
        return 1;
}
 
 
#ifdef CONFIG_ARPD
 
/*
 *      Send ARPD message.
 */
static void arpd_send(int req, u32 addr, struct device * dev, char *ha,
                      unsigned long updated)
{
        int retval;
        struct sk_buff *skb;
        struct arpd_request *arpreq;
 
        if (arpd_not_running)
                return;
 
        skb = alloc_skb(sizeof(struct arpd_request), GFP_ATOMIC);
        if (skb == NULL)
                return;
 
        skb->free=1;
        arpreq=(struct arpd_request *)skb_put(skb, sizeof(struct arpd_request));
        arpreq->req = req;
        arpreq->ip  = addr;
        arpreq->dev = (unsigned long)dev;
        arpreq->stamp = arpd_stamp;
        arpreq->updated = updated;
        if (ha)
                memcpy(arpreq->ha, ha, sizeof(arpreq->ha));
 
        retval = netlink_post(NETLINK_ARPD, skb);
        if (retval)
        {
                kfree_skb(skb, FREE_WRITE);
                if (retval == -EUNATCH)
                        arpd_not_running = 1;
        }
}
 
/*
 *      Send ARPD update message.
 */
 
static __inline__ void arpd_update(struct arp_table * entry)
{
        if (arpd_not_running)
                return;
        arpd_send(ARPD_UPDATE, entry->ip, entry->dev, entry->ha,
                  entry->last_updated);
}
 
/*
 *      Send ARPD lookup request.
 */
 
static __inline__ void arpd_lookup(u32 addr, struct device * dev)
{
        if (arpd_not_running)
                return;
        arpd_send(ARPD_LOOKUP, addr, dev, NULL, 0);
}
 
/*
 *      Send ARPD flush message.
 */
 
static __inline__ void arpd_flush(struct device * dev)
{
        if (arpd_not_running)
                return;
        arpd_send(ARPD_FLUSH, 0, dev, NULL, 0);
}
 
 
static int arpd_callback(struct sk_buff *skb)
{
        struct device * dev;
        struct arpd_request *retreq;
 
        arpd_not_running = 0;
 
        if (skb->len != sizeof(struct arpd_request))
        {
                kfree_skb(skb, FREE_READ);
                return -EINVAL;
        }
 
        retreq = (struct arpd_request *)skb->data;
        dev = (struct device*)retreq->dev;
 
        if (retreq->stamp != arpd_stamp || !dev)
        {
                kfree_skb(skb, FREE_READ);
                return -EINVAL;
        }
 
        if (!retreq->updated || empty(retreq->ha, sizeof(retreq->ha)))
        {
/*
 *      Invalid mapping: drop it and send ARP broadcast.
 */
                arp_send(ARPOP_REQUEST, ETH_P_ARP, retreq->ip, dev, dev->pa_addr, NULL,
                         dev->dev_addr, NULL);
        }
        else
        {
                arp_fast_lock();
                arp_update(retreq->ip, retreq->ha, dev, retreq->updated, NULL, 0);
                arp_unlock();
        }
 
        kfree_skb(skb, FREE_READ);
        return sizeof(struct arpd_request);
}
 
#else
 
static __inline__ void arpd_update(struct arp_table * entry)
{
        return;
}
 
#endif /* CONFIG_ARPD */
 
 
 
 
/*
 *      ARP expiration routines.
 */
 
/*
 *      Force the expiry of an entry in the internal cache so the memory
 *      can be used for a new request.
 */
 
static int arp_force_expire(void)
{
        int i;
        struct arp_table *entry, **pentry;
        struct arp_table **oldest_entry = NULL;
        unsigned long oldest_used = ~0;
        unsigned long flags;
        unsigned long now = jiffies;
        int result = 0;
 
        static int last_index;
 
        if (ARP_LOCKED())
                return 0;
 
        save_flags(flags);
 
        if (last_index >= ARP_TABLE_SIZE)
                last_index = 0;
 
        for (i = 0; i < ARP_TABLE_SIZE; i++, last_index++)
        {
                pentry = &arp_tables[last_index & (ARP_TABLE_SIZE-1)];
 
                while ((entry = *pentry) != NULL)
                {
                        if (!(entry->flags & ATF_PERM))
                        {
                                int users;
                                cli();
                                users = arp_count_hhs(entry);
 
                                if (!users && now - entry->last_used > sysctl_arp_timeout)
                                {
                                        *pentry = entry->next;
                                        restore_flags(flags);
#if RT_CACHE_DEBUG >= 2
                                        printk("arp_force_expire: %08x expired\n", entry->ip);
#endif
                                        arp_free_entry(entry);
                                        result++;
                                        if (arp_size < ARP_MAXSIZE)
                                                goto done;
                                        continue;
                                }
                                restore_flags(flags);
                                if (!users && entry->last_used < oldest_used)
                                {
                                        oldest_entry = pentry;
                                        oldest_used = entry->last_used;
                                }
                        }
                        pentry = &entry->next;
                }
        }
 
done:
        if (result || !oldest_entry)
                return result;
 
        entry = *oldest_entry;
        *oldest_entry = entry->next;
#if RT_CACHE_DEBUG >= 2
        printk("arp_force_expire: expiring %08x\n", entry->ip);
#endif
        arp_free_entry(entry);
        return 1;
}
 
/*
 *      Check if there are entries that are too old and remove them. If the
 *      ATF_PERM flag is set, they are always left in the arp cache (permanent
 *      entries). If an entry was not confirmed for ARP_CONFIRM_INTERVAL,
 *      send point-to-point ARP request.
 *      If it will not be confirmed for ARP_CONFIRM_TIMEOUT,
 *      give it to shred by arp_expire_entry.
 */
 
static void arp_check_expire(unsigned long dummy)
{
        int i;
        unsigned long now = jiffies;
 
        del_timer(&arp_timer);
 
#ifdef CONFIG_ARPD
        arpd_not_running = 0;
#endif
 
        ip_rt_check_expire();
 
        arp_fast_lock();
 
        if (!ARP_LOCKED())
        {
 
                for (i = 0; i < ARP_TABLE_SIZE; i++)
                {
                        struct arp_table *entry, **pentry;
 
                        pentry = &arp_tables[i];
 
                        while ((entry = *pentry) != NULL)
                        {
                                if (entry->flags & ATF_PERM)
                                {
                                        pentry = &entry->next;
                                        continue;
                                }
 
                                cli();
                                if (now - entry->last_used > sysctl_arp_timeout
                                    && !arp_count_hhs(entry))
                                {
                                        *pentry = entry->next;
                                        sti();
#if RT_CACHE_DEBUG >= 2
                                        printk("arp_expire: %08x expired\n", entry->ip);
#endif
                                        arp_free_entry(entry);
                                        continue;
                                }
                                sti();
                                if (entry->last_updated
                                    && now - entry->last_updated > sysctl_arp_confirm_interval
                                    && !(entry->flags & ATF_PERM))
                                {
                                        struct device * dev = entry->dev;
                                        entry->retries = sysctl_arp_max_tries+sysctl_arp_max_pings;
                                        del_timer(&entry->timer);
                                        entry->timer.expires = jiffies + ARP_CONFIRM_TIMEOUT;
                                        add_timer(&entry->timer);
                                        arp_send(ARPOP_REQUEST, ETH_P_ARP, entry->ip,
                                                 dev, dev->pa_addr, entry->ha,
                                                 dev->dev_addr, NULL);
#if RT_CACHE_DEBUG >= 2
                                        printk("arp_expire: %08x requires confirmation\n", entry->ip);
#endif
                                }
                                pentry = &entry->next;  /* go to next entry */
                        }
                }
        }
 
        arp_unlock();
 
        /*
         *      Set the timer again.
         */
 
        arp_timer.expires = jiffies + sysctl_arp_check_interval;
        add_timer(&arp_timer);
}
 
/*
 *      This function is called, if an entry is not resolved in ARP_RES_TIME.
 *      When more than MAX_ARP_TRIES retries was done, release queued skb's,
 *      but not discard entry itself if  it is in use.
 */
 
static void arp_expire_request (unsigned long arg)
{
        struct arp_table *entry = (struct arp_table *) arg;
        struct arp_table **pentry;
        unsigned long hash;
        unsigned long flags;
 
        arp_fast_lock();
 
        save_flags(flags);
        cli();
        del_timer(&entry->timer);
 
        /*
         *      If arp table is locked, defer expire processing.
         */
        if (ARP_LOCKED())
        {
#if RT_CACHE_DEBUG >= 1
                printk(KERN_DEBUG "arp_expire_request: %08x deferred\n", entry->ip);
#endif
                entry->timer.expires = jiffies + HZ/10;
                add_timer(&entry->timer);
                restore_flags(flags);
                arp_unlock();
                return;
        }
 
        /*
         *      Since all timeouts are handled with interrupts enabled, there is a
         *      small chance, that this entry has just been resolved by an incoming
         *      packet. This is the only race condition, but it is handled...
         *
         *      One exception: if entry is COMPLETE but old,
         *      it means that point-to-point ARP ping has been failed
         *      (It really occurs with Cisco 4000 routers)
         *      We should reconfirm it.
         */
 
        if ((entry->flags & ATF_COM) && entry->last_updated
            && jiffies - entry->last_updated <= sysctl_arp_confirm_interval)
        {
                restore_flags(flags);
                arp_unlock();
                return;
        }
 
        restore_flags(flags);
 
        if (entry->last_updated && --entry->retries > 0)
        {
                struct device *dev = entry->dev;
 
#if RT_CACHE_DEBUG >= 2
                printk("arp_expire_request: %08x timed out\n", entry->ip);
#endif
                /* Set new timer. */
                entry->timer.expires = jiffies + sysctl_arp_res_time;
                add_timer(&entry->timer);
                arp_send(ARPOP_REQUEST, ETH_P_ARP, entry->ip, dev, dev->pa_addr,
                         entry->retries > sysctl_arp_max_tries ? entry->ha : NULL,
                         dev->dev_addr, NULL);
                arp_unlock();
                return;
        }
 
        /*
         *      The host is really dead.
         */
 
        arp_purge_send_q(entry);
 
        cli();
        if (arp_count_hhs(entry))
        {
                /*
                 *      The host is dead, but someone refers to it.
                 *      It is useless to drop this entry just now,
                 *      it will be born again, so that
                 *      we keep it, but slow down retransmitting
                 *      to ARP_DEAD_RES_TIME.
                 */
 
                struct device *dev = entry->dev;
#if RT_CACHE_DEBUG >= 2
                printk("arp_expire_request: %08x is dead\n", entry->ip);
#endif
                entry->retries = sysctl_arp_max_tries;
                entry->flags &= ~ATF_COM;
                arp_invalidate_hhs(entry);
                restore_flags(flags);
 
                /*
                 *      Declare the entry dead.
                 */
                entry->last_updated = 0;
                arpd_update(entry);
 
                entry->timer.expires = jiffies + sysctl_arp_dead_res_time;
                add_timer(&entry->timer);
                arp_send(ARPOP_REQUEST, ETH_P_ARP, entry->ip, dev, dev->pa_addr,
                         NULL, dev->dev_addr, NULL);
                arp_unlock();
                return;
        }
        restore_flags(flags);
 
        entry->last_updated = 0;
        arpd_update(entry);
 
        hash = HASH(entry->ip);
 
        pentry = &arp_tables[hash];
 
        while (*pentry != NULL)
        {
                if (*pentry != entry)
                {
                        pentry = &(*pentry)->next;
                        continue;
                }
                *pentry = entry->next;
#if RT_CACHE_DEBUG >= 2
                printk("arp_expire_request: %08x is killed\n", entry->ip);
#endif
                arp_free_entry(entry);
        }
        arp_unlock();
}
 
 
/*
 * Allocate memory for a new entry.  If we are at the maximum limit
 * of the internal ARP cache, arp_force_expire() an entry.  NOTE:
 * arp_force_expire() needs the cache to be locked, so therefore
 * arp_alloc_entry() should only be called with the cache locked too!
 */
 
static struct arp_table * arp_alloc_entry(void)
{
        struct arp_table * entry;
 
 
        if (arp_size >= ARP_MAXSIZE)
                arp_force_expire();
 
        entry = (struct arp_table *)
                kmalloc(sizeof(struct arp_table),GFP_ATOMIC);
 
        if (entry != NULL)
        {
                atomic_inc(&arp_size);
                memset(entry, 0, sizeof(struct arp_table));
 
                entry->mask = DEF_ARP_NETMASK;
                init_timer(&entry->timer);
                entry->timer.function = arp_expire_request;
                entry->timer.data = (unsigned long)entry;
                entry->last_updated = entry->last_used = jiffies;
                skb_queue_head_init(&entry->skb);
        }
        return entry;
}
 
 
 
/*
 *      Purge a device from the ARP queue
 */
 
int arp_device_event(struct notifier_block *this, unsigned long event, void *ptr)
{
        struct device *dev=ptr;
        int i;
 
        if (event != NETDEV_DOWN)
                return NOTIFY_DONE;
 
#ifdef  CONFIG_ARPD
        arpd_flush(dev);
        arpd_stamp++;
#endif
 
        arp_fast_lock();
#if RT_CACHE_DEBUG >= 1  
        if (ARP_LOCKED())
                printk("arp_device_event: impossible\n");
#endif
 
        for (i = 0; i < FULL_ARP_TABLE_SIZE; i++)
        {
                struct arp_table *entry;
                struct arp_table **pentry = &arp_tables[i];
 
                while ((entry = *pentry) != NULL)
                {
                        if (entry->dev == dev)
                        {
                                *pentry = entry->next;  /* remove from list */
                                arp_free_entry(entry);
                        }
                        else
                                pentry = &entry->next;  /* go to next entry */
                }
        }
        arp_unlock();
        return NOTIFY_DONE;
}
 
 
 
/*
 *      This will try to retransmit everything on the queue.
 */
 
static void arp_send_q(struct arp_table *entry)
{
        struct sk_buff *skb;
 
        unsigned long flags;
 
        /*
         *      Empty the entire queue, building its data up ready to send
         */
 
        if(!(entry->flags&ATF_COM))
        {
                printk(KERN_ERR "arp_send_q: incomplete entry for %s\n",
                                in_ntoa(entry->ip));
                /* Can't flush the skb, because RFC1122 says to hang on to */
                /* at least one from any unresolved entry.  --MS */
                /* What's happened is that someone has 'unresolved' the entry
                   as we got to use it - this 'can't happen' -- AC */
                return;
        }
 
        save_flags(flags);
 
        cli();
        while((skb = skb_dequeue(&entry->skb)) != NULL)
        {
                IS_SKB(skb);
                skb_device_lock(skb);
                restore_flags(flags);
                if(!skb->dev->rebuild_header(skb->data,skb->dev,skb->raddr,skb))
                {
                        skb->arp  = 1;
                        if(skb->sk==NULL)
                                dev_queue_xmit(skb, skb->dev, 0);
                        else
                                dev_queue_xmit(skb,skb->dev,skb->sk->priority);
                }
                cli();
        }
        restore_flags(flags);
}
 
 
static int
arp_update (u32 sip, char *sha, struct device * dev,
            unsigned long updated, struct arp_table *ientry, int grat)
{
        struct arp_table * entry;
        unsigned long hash;
        int do_arpd = 0;
 
        if (updated == 0)
        {
                updated = jiffies;
                do_arpd = 1;
        }
 
        hash = HASH(sip);
 
        for (entry=arp_tables[hash]; entry; entry = entry->next)
                if (entry->ip == sip && entry->dev == dev)
                        break;
 
        if (entry)
        {
/*
 *      Entry found; update it only if it is not a permanent entry.
 */
                if (!(entry->flags & ATF_PERM))
                {
                        del_timer(&entry->timer);
                        entry->last_updated = updated;
                        if (memcmp(entry->ha, sha, dev->addr_len)!=0)
                        {
                                memcpy(entry->ha, sha, dev->addr_len);
                                if (entry->flags & ATF_COM)
                                        arp_update_hhs(entry);
                        }
                        if (do_arpd)
                                arpd_update(entry);
                }
 
                if (!(entry->flags & ATF_COM))
                {
/*
 *      This entry was incomplete.  Delete the retransmit timer
 *      and switch to complete status.
 */
                        entry->flags |= ATF_COM;
                        arp_update_hhs(entry);
/*
 *      Send out waiting packets. We might have problems, if someone is
 *      manually removing entries right now -- entry might become invalid
 *      underneath us.
 */
                        arp_send_q(entry);
                }
                return 1;
        }
 
/*
 *      No entry found.  Need to add a new entry to the arp table.
 */
        entry = ientry;
 
        if (grat && !entry)
                return 0;
 
        if (!entry)
        {
                entry = arp_alloc_entry();
                if (!entry)
                        return 0;
 
                entry->ip = sip;
                entry->flags = ATF_COM;
                memcpy(entry->ha, sha, dev->addr_len);
                entry->dev = dev;
        }
 
        entry->last_updated = updated;
        entry->last_used = jiffies;
        if (do_arpd)
                arpd_update(entry);
 
        if (!ARP_LOCKED())
        {
                entry->next = arp_tables[hash];
                arp_tables[hash] = entry;
                return 0;
        }
#if RT_CACHE_DEBUG >= 2
        printk("arp_update: %08x backlogged\n", entry->ip);
#endif
        arp_enqueue(&arp_backlog, entry);
        arp_bh_mask |= ARP_BH_BACKLOG;
        return 0;
}
 
 
 
static __inline__ struct arp_table *arp_lookup(u32 paddr, struct device * dev)
{
        struct arp_table *entry;
 
        for (entry = arp_tables[HASH(paddr)]; entry != NULL; entry = entry->next)
                if (entry->ip == paddr && (!dev || entry->dev == dev))
                        return entry;
        return NULL;
}
 
/*
 *      Find an arp mapping in the cache. If not found, return false.
 */
 
int arp_query(unsigned char *haddr, u32 paddr, struct device * dev)
{
        struct arp_table *entry;
 
        arp_fast_lock();
 
        entry = arp_lookup(paddr, dev);
 
        if (entry != NULL)
        {
                entry->last_used = jiffies;
                if (entry->flags & ATF_COM)
                {
                        memcpy(haddr, entry->ha, dev->addr_len);
                        arp_unlock();
                        return 1;
                }
        }
        arp_unlock();
        return 0;
}
 
 
static int arp_set_predefined(int addr_hint, unsigned char * haddr, u32 paddr, struct device * dev)
{
        switch (addr_hint)
        {
                case IS_MYADDR:
                        printk(KERN_DEBUG "ARP: arp called for own IP address\n");
                        memcpy(haddr, dev->dev_addr, dev->addr_len);
                        return 1;
#ifdef CONFIG_IP_MULTICAST
                case IS_MULTICAST:
                        if(dev->type==ARPHRD_ETHER || dev->type==ARPHRD_IEEE802
                                || dev->type==ARPHRD_FDDI)
                        {
                                u32 taddr;
                                haddr[0]=0x01;
                                haddr[1]=0x00;
                                haddr[2]=0x5e;
                                taddr=ntohl(paddr);
                                haddr[5]=taddr&0xff;
                                taddr=taddr>>8;
                                haddr[4]=taddr&0xff;
                                taddr=taddr>>8;
                                haddr[3]=taddr&0x7f;
                                return 1;
                        }
                /*
                 *      If a device does not support multicast broadcast the stuff (eg AX.25 for now)
                 */
#endif
 
                case IS_BROADCAST:
                        memcpy(haddr, dev->broadcast, dev->addr_len);
                        return 1;
        }
        return 0;
}
 
/*
 *      Create a new unresolved entry.
 */
 
struct arp_table * arp_new_entry(u32 paddr, struct device *dev, struct hh_cache *hh, struct sk_buff *skb)
{
        struct arp_table *entry;
 
        entry = arp_alloc_entry();
 
        if (entry != NULL)
        {
                entry->ip = paddr;
                entry->dev = dev;
                if (hh)
                {
                        entry->hh = hh;
                        atomic_inc(&hh->hh_refcnt);
                        hh->hh_arp = (void*)entry;
                }
                entry->timer.expires = jiffies + sysctl_arp_res_time;
 
                if (skb != NULL)
                {
                        skb_queue_tail(&entry->skb, skb);
                        skb_device_unlock(skb);
                }
 
                if (!ARP_LOCKED())
                {
                        unsigned long hash = HASH(paddr);
                        entry->next = arp_tables[hash];
                        arp_tables[hash] = entry;
                        add_timer(&entry->timer);
                        entry->retries = sysctl_arp_max_tries;
#ifdef CONFIG_ARPD
                        if (!arpd_not_running)
                                arpd_lookup(paddr, dev);
                        else
#endif
                                arp_send(ARPOP_REQUEST, ETH_P_ARP, paddr, dev, dev->pa_addr, NULL,
                                         dev->dev_addr, NULL);
                }
                else
                {
#if RT_CACHE_DEBUG >= 2
                        printk("arp_new_entry: %08x backlogged\n", entry->ip);
#endif
                        arp_enqueue(&arp_req_backlog, entry);
                        arp_bh_mask |= ARP_BH_BACKLOG;
                }
        }
        return entry;
}
 
 
/*
 *      Find an arp mapping in the cache. If not found, post a request.
 */
 
int arp_find(unsigned char *haddr, u32 paddr, struct device *dev,
             u32 saddr, struct sk_buff *skb)
{
        struct arp_table *entry;
        unsigned long hash;
 
        if (arp_set_predefined(ip_chk_addr(paddr), haddr, paddr, dev))
        {
                if (skb)
                        skb->arp = 1;
                return 0;
        }
 
        hash = HASH(paddr);
        arp_fast_lock();
 
        /*
         *      Find an entry
         */
        entry = arp_lookup(paddr, dev);
 
        if (entry != NULL)      /* It exists */
        {
                if (entry->flags & ATF_COM)
                {
                        entry->last_used = jiffies;
                        memcpy(haddr, entry->ha, dev->addr_len);
                        if (skb)
                                skb->arp = 1;
                        arp_unlock();
                        return 0;
                }
 
                /*
                 *      A request was already sent, but no reply yet. Thus
                 *      queue the packet with the previous attempt
                 */
 
                if (skb != NULL)
                {
                        if (entry->last_updated)
                        {
                                skb_queue_tail(&entry->skb, skb);
                                skb_device_unlock(skb);
                        }
                        /*
                         * If last_updated==0 host is dead, so
                         * drop skb's and set socket error.
                         */
                        else
                        {
                                icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, 0, dev);
                                skb_device_unlock(skb); /* else it is lost forever */
                                dev_kfree_skb(skb, FREE_WRITE);
                        }
                }
                arp_unlock();
                return 1;
        }
 
        entry = arp_new_entry(paddr, dev, NULL, skb);
 
        if (skb != NULL && !entry) {
                skb_device_unlock(skb); /* else it is lost forever */
                dev_kfree_skb(skb, FREE_WRITE);
        }
 
        arp_unlock();
        return 1;
}
 
/*
 *      Binding hardware header cache entry.
 *      It is the only really complicated part of arp code.
 *      We have no locking for hh records, so that
 *      all possible race conditions should be resolved by
 *      cli()/sti() pairs.
 *
 *      Important note: hhs never disappear from lists, if ARP_LOCKED,
 *      this fact allows to scan hh lists with enabled interrupts,
 *      but results in generating duplicate hh entries.
 *      It is harmless. (and I've never seen such event)
 *
 *      Returns 0, if hh has been just created, so that
 *      caller should fill it.
 */
 
int arp_bind_cache(struct hh_cache ** hhp, struct device *dev, unsigned short htype, u32 paddr)
{
        struct arp_table *entry;
        struct hh_cache *hh;
        int addr_hint;
        unsigned long flags;
 
        save_flags(flags);
 
        if ((addr_hint = ip_chk_addr(paddr)) != 0)
        {
                unsigned char haddr[MAX_ADDR_LEN];
                if (*hhp)
                        return 1;
                hh = arp_alloc_hh(htype);
                if (!hh)
                        return 1;
                arp_set_predefined(addr_hint, haddr, paddr, dev);
                dev->header_cache_update(hh, dev, haddr);
                return arp_set_hh(hhp, hh);
        }
 
        arp_fast_lock();
 
        entry = arp_lookup(paddr, dev);
 
        if (entry)
        {
                for (hh = entry->hh; hh; hh=hh->hh_next)
                        if (hh->hh_type == htype)
                                break;
 
                if (hh)
                {
                        arp_set_hh(hhp, hh);
                        arp_unlock();
                        return 1;
                }
        }
 
        hh = arp_alloc_hh(htype);
        if (!hh)
        {
                arp_unlock();
                return 1;
        }
 
        if (entry)
        {
 
                cli();
                hh->hh_arp = (void*)entry;
                hh->hh_next = entry->hh;
                entry->hh = hh;
                atomic_inc(&hh->hh_refcnt);
                restore_flags(flags);
 
                if (entry->flags & ATF_COM)
                        dev->header_cache_update(hh, dev, entry->ha);
 
                if (arp_set_hh(hhp, hh))
                {
                        arp_unlock();
                        return 0;
                }
 
                entry->last_used = jiffies;
                arp_unlock();
                return 0;
        }
 
        entry = arp_new_entry(paddr, dev, hh, NULL);
        if (entry == NULL)
        {
                kfree_s(hh, sizeof(struct hh_cache));
                arp_unlock();
                return 1;
        }
 
        if (!arp_set_hh(hhp, hh))
        {
                arp_unlock();
                return 0;
        }
        arp_unlock();
        return 1;
}
 
static void arp_run_bh()
{
        unsigned long flags;
        struct arp_table *entry, *entry1;
        struct device  * dev;
        unsigned long hash;
        struct hh_cache *hh;
        u32 sip;
 
        save_flags(flags);
        cli();
        arp_fast_lock();
 
        while (arp_bh_mask)
        {
                arp_bh_mask  &= ~ARP_BH_BACKLOG;
 
                while ((entry = arp_dequeue(&arp_backlog)) != NULL)
                {
                        restore_flags(flags);
                        if (arp_update(entry->ip, entry->ha, entry->dev, 0, entry, 0))
                                arp_free_entry(entry);
                        cli();
                }
 
                cli();
                while ((entry = arp_dequeue(&arp_req_backlog)) != NULL)
                {
                        restore_flags(flags);
 
                        dev = entry->dev;
                        sip = entry->ip;
                        hash = HASH(sip);
 
                        for (entry1 = arp_tables[hash]; entry1; entry1 = entry1->next)
                                if (entry1->ip == sip && entry1->dev == dev)
                                        break;
 
                        if (!entry1)
                        {
                                cli();
                                entry->next = arp_tables[hash];
                                arp_tables[hash] = entry;
                                restore_flags(flags);
                                entry->timer.expires = jiffies + sysctl_arp_res_time;
                                entry->retries = sysctl_arp_max_tries;
                                entry->last_used = jiffies;
                                if (!(entry->flags & ATF_COM))
                                {
                                        add_timer(&entry->timer);
#ifdef CONFIG_ARPD
                                        if (!arpd_not_running)
                                                arpd_lookup(sip, dev);
                                        else
#endif
                                                arp_send(ARPOP_REQUEST, ETH_P_ARP, sip, dev, dev->pa_addr, NULL, dev->dev_addr, NULL);
                                }
#if RT_CACHE_DEBUG >= 1
                                printk(KERN_DEBUG "arp_run_bh: %08x reinstalled\n", sip);
#endif
                        }
                        else
                        {
                                struct sk_buff * skb;
                                struct hh_cache * next;
 
                                /* Discard entry, but preserve its hh's and
                                 * skb's.
                                 */
                                cli();
                                for (hh=entry->hh; hh; hh=next)
                                {
                                        next = hh->hh_next;
                                        hh->hh_next = entry1->hh;
                                        entry1->hh = hh;
                                        hh->hh_arp = (void*)entry1;
                                }
                                entry->hh = NULL;
 
                                /* Prune skb list from entry
                                 * and graft it to entry1.
                                 */
                                while ((skb = skb_dequeue(&entry->skb)) != NULL)
                                {
                                        skb_device_lock(skb);
                                        restore_flags(flags);
                                        skb_queue_tail(&entry1->skb, skb);
                                        skb_device_unlock(skb);
                                        cli();
                                }
                                restore_flags(flags);
 
                                arp_free_entry(entry);
 
                                if (entry1->flags & ATF_COM)
                                {
                                        arp_update_hhs(entry1);
                                        arp_send_q(entry1);
                                }
                        }
                        cli();
                }
                cli();
        }
        arp_unlock();
        restore_flags(flags);
}
 
 
/*
 *      Interface to link layer: send routine and receive handler.
 */
 
/*
 *      Create and send an arp packet. If (dest_hw == NULL), we create a broadcast
 *      message.
 */
 
void arp_send(int type, int ptype, u32 dest_ip,
              struct device *dev, u32 src_ip,
              unsigned char *dest_hw, unsigned char *src_hw,
              unsigned char *target_hw)
{
        struct sk_buff *skb;
        struct arphdr *arp;
        unsigned char *arp_ptr;
 
        /*
         *      No arp on this interface.
         */
 
        if (dev->flags&IFF_NOARP)
                return;
 
        /*
         *      Allocate a buffer
         */
 
        skb = alloc_skb(sizeof(struct arphdr)+ 2*(dev->addr_len+4)
                                + dev->hard_header_len, GFP_ATOMIC);
        if (skb == NULL)
        {
                printk(KERN_DEBUG "ARP: no memory to send an arp packet\n");
                return;
        }
        skb_reserve(skb, dev->hard_header_len);
        arp = (struct arphdr *) skb_put(skb,sizeof(struct arphdr) + 2*(dev->addr_len+4));
        skb->arp = 1;
        skb->dev = dev;
        skb->free = 1;
        skb->protocol = htons (ETH_P_ARP);
 
        /*
         *      Fill the device header for the ARP frame
         */
        dev->hard_header(skb,dev,ptype,dest_hw?dest_hw:dev->broadcast,src_hw?src_hw:NULL,skb->len);
 
        /*
         * Fill out the arp protocol part.
         *
         * The arp hardware type should match the device type, except for FDDI,
         * which (according to RFC 1390) should always equal 1 (Ethernet).
         */
#ifdef CONFIG_FDDI
        arp->ar_hrd = (dev->type == ARPHRD_FDDI) ? htons(ARPHRD_ETHER) : htons(dev->type);
#else
        arp->ar_hrd = htons(dev->type);
#endif
        /*
         *      Exceptions everywhere. AX.25 uses the AX.25 PID value not the
         *      DIX code for the protocol. Make these device structure fields.
         */
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
#if defined(CONFIG_NETROM) || defined(CONFIG_NETROM_MODULE)
        arp->ar_pro = (dev->type == ARPHRD_AX25 || dev->type == ARPHRD_NETROM) ? htons(AX25_P_IP) : htons(ETH_P_IP);
#else
        arp->ar_pro = (dev->type != ARPHRD_AX25) ? htons(ETH_P_IP) : htons(AX25_P_IP);
#endif
#else
        arp->ar_pro = htons(ETH_P_IP);
#endif
        arp->ar_hln = dev->addr_len;
        arp->ar_pln = 4;
        arp->ar_op = htons(type);
 
        arp_ptr=(unsigned char *)(arp+1);
 
        memcpy(arp_ptr, src_hw, dev->addr_len);
        arp_ptr+=dev->addr_len;
        memcpy(arp_ptr, &src_ip,4);
        arp_ptr+=4;
        if (target_hw != NULL)
                memcpy(arp_ptr, target_hw, dev->addr_len);
        else
                memset(arp_ptr, 0, dev->addr_len);
        arp_ptr+=dev->addr_len;
        memcpy(arp_ptr, &dest_ip, 4);
 
        dev_queue_xmit(skb, dev, 0);
}
 
 
/*
 *      Receive an arp request by the device layer.
 */
 
int arp_rcv(struct sk_buff *skb, struct device *dev, struct packet_type *pt)
{
/*
 *      We shouldn't use this type conversion. Check later.
 */
 
        struct arphdr *arp = (struct arphdr *)skb->h.raw;
        unsigned char *arp_ptr= (unsigned char *)(arp+1);
        unsigned char *sha,*tha;
        u32 sip,tip;
 
        if(skb->pkt_type == PACKET_OTHERHOST)
        {
                kfree_skb(skb, FREE_READ);
                return 0;
        }
 
/*
 *      The hardware length of the packet should match the hardware length
 *      of the device.  Similarly, the hardware types should match.  The
 *      device should be ARP-able.  Also, if pln is not 4, then the lookup
 *      is not from an IP number.  We can't currently handle this, so toss
 *      it.
 */
#if defined(CONFIG_NET_ETHERNET) || defined(CONFIG_FDDI)
        if (dev->type == ARPHRD_ETHER || dev->type == ARPHRD_FDDI)
        {
                /*
                 * According to RFC 1390, FDDI devices should accept ARP hardware types
                 * of 1 (Ethernet).  However, to be more robust, we'll accept hardware
                 * types of either 1 (Ethernet) or 6 (IEEE 802.2).
                 *
                 * ETHERNET devices will accept both hardware types, too. (RFC 1042)
                 */
                if (arp->ar_hln != dev->addr_len    ||
                        ((ntohs(arp->ar_hrd) != ARPHRD_ETHER) && (ntohs(arp->ar_hrd) != ARPHRD_IEEE802)) ||
                        dev->flags & IFF_NOARP          ||
                        arp->ar_pln != 4)
                {
                        kfree_skb(skb, FREE_READ);
                        return 0;
                }
        }
        else
        {
                if (arp->ar_hln != dev->addr_len    ||
                        dev->type != ntohs(arp->ar_hrd) ||
                        dev->flags & IFF_NOARP          ||
                        arp->ar_pln != 4)
                {
                        kfree_skb(skb, FREE_READ);
                        return 0;
                }
        }
#else
        if (arp->ar_hln != dev->addr_len    ||
#if CONFIG_AP1000
            /*
             * ARP from cafe-f was found to use ARPHDR_IEEE802 instead of
             * the expected ARPHDR_ETHER.
             */
            (strcmp(dev->name,"fddi") == 0 &&
             arp->ar_hrd != ARPHRD_ETHER && arp->ar_hrd != ARPHRD_IEEE802) ||
            (strcmp(dev->name,"fddi") != 0 &&
             dev->type != ntohs(arp->ar_hrd)) ||
#else
                dev->type != ntohs(arp->ar_hrd) ||
#endif
                dev->flags & IFF_NOARP          ||
                arp->ar_pln != 4)
        {
                kfree_skb(skb, FREE_READ);
                return 0;
        }
#endif
 
/*
 *      Another test.
 *      The logic here is that the protocol being looked up by arp should
 *      match the protocol the device speaks.  If it doesn't, there is a
 *      problem, so toss the packet.
 */
 
        switch (dev->type)
        {
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
                case ARPHRD_AX25:
                        if(arp->ar_pro != htons(AX25_P_IP))
                        {
                                kfree_skb(skb, FREE_READ);
                                return 0;
                        }
                        break;
#endif
#if defined(CONFIG_NETROM) || defined(CONFIG_NETROM_MODULE)
                case ARPHRD_NETROM:
                        if(arp->ar_pro != htons(AX25_P_IP))
                        {
                                kfree_skb(skb, FREE_READ);
                                return 0;
                        }
                        break;
#endif
                case ARPHRD_ETHER:
                case ARPHRD_ARCNET:
                case ARPHRD_METRICOM:
                case ARPHRD_IEEE802:
                case ARPHRD_FDDI:
                        if(arp->ar_pro != htons(ETH_P_IP))
                        {
                                kfree_skb(skb, FREE_READ);
                                return 0;
                        }
                        break;
 
                default:
                        printk(KERN_ERR "ARP: dev->type mangled!\n");
                        kfree_skb(skb, FREE_READ);
                        return 0;
        }
 
/*
 *      Extract fields
 */
 
        sha=arp_ptr;
        arp_ptr += dev->addr_len;
        memcpy(&sip, arp_ptr, 4);
        arp_ptr += 4;
        tha=arp_ptr;
        arp_ptr += dev->addr_len;
        memcpy(&tip, arp_ptr, 4);
 
/*
 *      Check for bad requests for 127.x.x.x and requests for multicast
 *      addresses.  If this is one such, delete it.
 */
        if (LOOPBACK(tip) || MULTICAST(tip))
        {
                kfree_skb(skb, FREE_READ);
                return 0;
        }
 
/*
 *  Process entry.  The idea here is we want to send a reply if it is a
 *  request for us or if it is a request for someone else that we hold
 *  a proxy for.  We want to add an entry to our cache if it is a reply
 *  to us or if it is a request for our address.
 *  (The assumption for this last is that if someone is requesting our
 *  address, they are probably intending to talk to us, so it saves time
 *  if we cache their address.  Their address is also probably not in
 *  our cache, since ours is not in their cache.)
 *
 *  Putting this another way, we only care about replies if they are to
 *  us, in which case we add them to the cache.  For requests, we care
 *  about those for us and those for our proxies.  We reply to both,
 *  and in the case of requests for us we add the requester to the arp
 *  cache.
 */
 
/*
 *      try to switch to alias device whose addr is tip or closest to sip.
 */
 
#ifdef CONFIG_NET_ALIAS
        if (tip != dev->pa_addr && net_alias_has(skb->dev))
        {
                /*
                 *      net_alias_dev_rx32 returns main dev if it fails to found other.
                 *      if successful, also incr. alias rx count.
                 */
                dev = net_alias_dev_rx32(dev, AF_INET, sip, tip);
 
                if (dev->type != ntohs(arp->ar_hrd) || dev->flags & IFF_NOARP)
                {
                        kfree_skb(skb, FREE_READ);
                        return 0;
                }
        }
#endif
 
        if (arp->ar_op == htons(ARPOP_REQUEST))
        {
 
/*
 * Only reply for the real device address or when it's in our proxy tables
 */
                if (tip != dev->pa_addr)
                {
                        struct arp_table *proxy_entry;
 
/*
 *      To get in here, it is a request for someone else.  We need to
 *      check if that someone else is one of our proxies.  If it isn't,
 *      we can toss it.
 *
 *      Make "longest match" lookup, a la routing.
 */
 
                        arp_fast_lock();
 
                        for (proxy_entry = arp_proxy_list; proxy_entry;
                             proxy_entry = proxy_entry->next)
                        {
                                if (proxy_entry->dev == dev &&
                                    !((proxy_entry->ip^tip)&proxy_entry->mask))
                                        break;
                        }
 
                        if (proxy_entry && (proxy_entry->mask || ((dev->pa_addr^tip)&dev->pa_mask)))
                        {
                                char ha[MAX_ADDR_LEN];
                                struct rtable * rt;
 
                                /* Unlock arp tables to make life for
                                 * ip_rt_route easy. Note, that we are obliged
                                 * to make local copy of hardware address.
                                 */
 
                                memcpy(ha, proxy_entry->ha, dev->addr_len);
                                arp_unlock();
 
                                rt = ip_rt_route(tip, 0, NULL);
                                if (rt  && rt->rt_dev != dev)
                                        arp_send(ARPOP_REPLY,ETH_P_ARP,sip,dev,tip,sha,ha,sha);
                                ip_rt_put(rt);
 
                        }
                        else
                                arp_unlock();
                }
                else
                        arp_send(ARPOP_REPLY,ETH_P_ARP,sip,dev,tip,sha,dev->dev_addr,sha);
 
        }
 
        arp_fast_lock();
        arp_update(sip, sha, dev, 0, NULL, ip_chk_addr(tip) != IS_MYADDR && dev->type != ARPHRD_METRICOM);
        arp_unlock();
        kfree_skb(skb, FREE_READ);
        return 0;
}
 
 
 
/*
 *      User level interface (ioctl, /proc)
 */
 
/*
 *      Set (create) an ARP cache entry.
 */
 
static int arp_req_set(struct arpreq *r, struct device * dev)
{
        struct arp_table *entry, **entryp;
        struct sockaddr_in *si;
        unsigned char *ha;
        u32 ip;
        u32 mask = DEF_ARP_NETMASK;
        unsigned long flags;
 
        /*
         *      Extract netmask (if supplied).
         */
 
        if (r->arp_flags&ATF_NETMASK)
        {
                si = (struct sockaddr_in *) &r->arp_netmask;
                mask = si->sin_addr.s_addr;
        }
 
        /*
         *      Extract destination.
         */
 
        si = (struct sockaddr_in *) &r->arp_pa;
        ip = si->sin_addr.s_addr;
 
 
        if (r->arp_flags&ATF_PUBL)
        {
                if (!mask && ip)
                        return -EINVAL;
                if (!dev) {
                        dev = dev_getbytype(r->arp_ha.sa_family);
                        if (!dev)
                                return -ENODEV;
                }
        }
        else
        {
                if (!dev)
                {
                        struct rtable * rt;
                        rt = ip_rt_route(ip, 0, NULL);
                        if (!rt)
                                return -ENETUNREACH;
                        dev = rt->rt_dev;
                        ip_rt_put(rt);
                        if (!dev)
                                return -ENODEV;
                }
                if (dev->type != ARPHRD_METRICOM && ip_chk_addr(ip))
                        return -EINVAL;
        }
        if (dev->flags & (IFF_LOOPBACK | IFF_NOARP))
                return -ENODEV;
 
        if (r->arp_ha.sa_family != dev->type)
                return -EINVAL;
 
        arp_fast_lock();
#if RT_CACHE_DEBUG >= 1
        if (ARP_LOCKED())
                printk("arp_req_set: bug\n");
#endif
 
        if (!(r->arp_flags & ATF_PUBL))
                entryp = &arp_tables[HASH(ip)];
        else
                entryp = &arp_proxy_list;
 
        while ((entry = *entryp) != NULL)
        {
                /* User supplied arp entries are definitive - RHP 960603 */
 
                if (entry->ip == ip && entry->mask == mask && entry->dev == dev) {
                        *entryp=entry->next;
                        arp_free_entry(entry);
                        continue;
                }
                if ((entry->mask & mask) != mask)
                        break;
                entryp = &entry->next;
        }
 
        entry = arp_alloc_entry();
        if (entry == NULL)
        {
                arp_unlock();
                return -ENOMEM;
        }
        entry->ip = ip;
        entry->dev = dev;
        entry->mask = mask;
        entry->flags = r->arp_flags;
 
        entry->next = *entryp;
        *entryp = entry;
 
        ha = r->arp_ha.sa_data;
        if (empty(ha, dev->addr_len))
                ha = dev->dev_addr;
 
        save_flags(flags);
        cli();
        memcpy(entry->ha, ha, dev->addr_len);
        entry->last_updated = entry->last_used = jiffies;
        entry->flags |= ATF_COM;
        restore_flags(flags);
        arpd_update(entry);
        arp_update_hhs(entry);
        arp_unlock();
        return 0;
}
 
 
 
/*
 *      Get an ARP cache entry.
 */
 
static int arp_req_get(struct arpreq *r, struct device *dev)
{
        struct arp_table *entry;
        struct sockaddr_in *si;
        u32 mask = DEF_ARP_NETMASK;
 
        if (r->arp_flags&ATF_NETMASK)
        {
                si = (struct sockaddr_in *) &r->arp_netmask;
                mask = si->sin_addr.s_addr;
        }
 
        si = (struct sockaddr_in *) &r->arp_pa;
 
        arp_fast_lock();
#if RT_CACHE_DEBUG >= 1
        if (ARP_LOCKED())
                printk("arp_req_set: impossible\n");
#endif
 
        if (!(r->arp_flags & ATF_PUBL))
                entry = arp_tables[HASH(si->sin_addr.s_addr)];
        else
                entry = arp_proxy_list;
 
        for ( ; entry ;entry = entry->next)
        {
                if (entry->ip == si->sin_addr.s_addr
                    && (!dev || entry->dev == dev)
                    && (!(r->arp_flags&ATF_NETMASK) || entry->mask == mask))
                {
                        memcpy(r->arp_ha.sa_data, entry->ha, entry->dev->addr_len);
                        r->arp_ha.sa_family = entry->dev->type;
                        r->arp_flags = entry->flags;
                        strncpy(r->arp_dev, entry->dev->name, sizeof(r->arp_dev));
                        arp_unlock();
                        return 0;
                }
        }
 
        arp_unlock();
        return -ENXIO;
}
 
static int arp_req_delete(struct arpreq *r, struct device * dev)
{
        struct sockaddr_in      *si;
        struct arp_table        *entry, **entryp;
        int     retval = -ENXIO;
        u32     mask = DEF_ARP_NETMASK;
 
        if (r->arp_flags&ATF_NETMASK)
        {
                si = (struct sockaddr_in *) &r->arp_netmask;
                mask = si->sin_addr.s_addr;
        }
 
        si = (struct sockaddr_in *) &r->arp_pa;
 
        arp_fast_lock();
#if RT_CACHE_DEBUG >= 1
        if (ARP_LOCKED())
                printk("arp_req_delete: impossible\n");
#endif
 
        if (!(r->arp_flags & ATF_PUBL))
                entryp = &arp_tables[HASH(si->sin_addr.s_addr)];
        else
                entryp = &arp_proxy_list;
 
        while ((entry = *entryp) != NULL)
        {
                if (entry->ip == si->sin_addr.s_addr
                    && (!dev || entry->dev == dev)
                    && (!(r->arp_flags&ATF_NETMASK) || entry->mask == mask))
                {
                        *entryp = entry->next;
                        arp_free_entry(entry);
                        retval = 0;
                        continue;
                }
                entryp = &entry->next;
        }
 
        arp_unlock();
        return retval;
}
 
/*
 *      Handle an ARP layer I/O control request.
 */
 
int arp_ioctl(unsigned int cmd, void *arg)
{
        int err;
        struct arpreq r;
 
        struct device * dev = NULL;
 
        switch(cmd)
        {
                case SIOCDARP:
                case SIOCSARP:
                        if (!suser())
                                return -EPERM;
                case SIOCGARP:
                        err = verify_area(VERIFY_READ, arg, sizeof(struct arpreq));
                        if (err)
                                return err;
                        memcpy_fromfs(&r, arg, sizeof(struct arpreq));
                        break;
                case OLD_SIOCDARP:
                case OLD_SIOCSARP:
                        if (!suser())
                                return -EPERM;
                case OLD_SIOCGARP:
                        err = verify_area(VERIFY_READ, arg, sizeof(struct arpreq_old));
                        if (err)
                                return err;
                        memcpy_fromfs(&r, arg, sizeof(struct arpreq_old));
                        memset(&r.arp_dev, 0, sizeof(r.arp_dev));
                        break;
                default:
                        return -EINVAL;
        }
 
        if (r.arp_pa.sa_family != AF_INET)
                return -EPFNOSUPPORT;
 
        if (!(r.arp_flags & ATF_PUBL))
                r.arp_flags &= ~ATF_NETMASK;
        if (!(r.arp_flags & ATF_NETMASK))
                ((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr=DEF_ARP_NETMASK;
 
        if (r.arp_dev[0])
        {
                if ((dev = dev_get(r.arp_dev)) == NULL)
                        return -ENODEV;
 
                if (!r.arp_ha.sa_family)
                        r.arp_ha.sa_family = dev->type;
                else if (r.arp_ha.sa_family != dev->type)
                        return -EINVAL;
        }
 
        switch(cmd)
        {
                case SIOCDARP:
                        return arp_req_delete(&r, dev);
                case SIOCSARP:
                        return arp_req_set(&r, dev);
                case OLD_SIOCDARP:
                        /* old  SIOCDARP destroys both
                         * normal and proxy mappings
                         */
                        r.arp_flags &= ~ATF_PUBL;
                        err = arp_req_delete(&r, dev);
                        r.arp_flags |= ATF_PUBL;
                        if (!err)
                                arp_req_delete(&r, dev);
                        else
                                err = arp_req_delete(&r, dev);
                        return err;
                case OLD_SIOCSARP:
                        err = arp_req_set(&r, dev);
                        /* old SIOCSARP works so funny,
                         * that its behaviour can be emulated
                         * only approximately 8).
                         * It should work. --ANK
                         */
                        if (r.arp_flags & ATF_PUBL)
                        {
                                r.arp_flags &= ~ATF_PUBL;
                                arp_req_delete(&r, dev);
                        }
                        return err;
                case SIOCGARP:
                        err = verify_area(VERIFY_WRITE, arg, sizeof(struct arpreq));
                        if (err)
                                return err;
                        err = arp_req_get(&r, dev);
                        if (!err)
                                memcpy_tofs(arg, &r, sizeof(r));
                        return err;
                case OLD_SIOCGARP:
                        err = verify_area(VERIFY_WRITE, arg, sizeof(struct arpreq_old));
                        if (err)
                                return err;
                        r.arp_flags &= ~ATF_PUBL;
                        err = arp_req_get(&r, dev);
                        if (err < 0)
                        {
                                r.arp_flags |= ATF_PUBL;
                                err = arp_req_get(&r, dev);
                        }
                        if (!err)
                                memcpy_tofs(arg, &r, sizeof(struct arpreq_old));
                        return err;
        }
        /*NOTREACHED*/
        return 0;
}
 
/*
 *      Write the contents of the ARP cache to a PROCfs file.
 */
 
#define HBUFFERLEN 30
 
int arp_get_info(char *buffer, char **start, off_t offset, int length, int dummy)
{
        int len=0;
        off_t pos=0;
        int size;
        struct arp_table *entry;
        char hbuffer[HBUFFERLEN];
        int i,j,k;
        const char hexbuf[] =  "0123456789ABCDEF";
 
        size = sprintf(buffer,"IP address       HW type     Flags       HW address            Mask     Device\n");
 
        pos+=size;
        len+=size;
 
        arp_fast_lock();
 
        for(i=0; i<FULL_ARP_TABLE_SIZE; i++)
        {
                for(entry=arp_tables[i]; entry!=NULL; entry=entry->next)
                {
/*
 *      Convert hardware address to XX:XX:XX:XX ... form.
 */
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
#if defined(CONFIG_NETROM) || defined(CONFIG_NETROM_MODULE)
                        if (entry->dev->type == ARPHRD_AX25 || entry->dev->type == ARPHRD_NETROM)
                             strcpy(hbuffer,ax2asc((ax25_address *)entry->ha));
                        else {
#else
                        if(entry->dev->type==ARPHRD_AX25)
                             strcpy(hbuffer,ax2asc((ax25_address *)entry->ha));
                        else {
#endif
#endif
 
                        for(k=0,j=0;k<HBUFFERLEN-3 && j<entry->dev->addr_len;j++)
                        {
                                hbuffer[k++]=hexbuf[ (entry->ha[j]>>4)&15 ];
                                hbuffer[k++]=hexbuf[  entry->ha[j]&15     ];
                                hbuffer[k++]=':';
                        }
                        hbuffer[--k]=0;
 
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
                        }
#endif
                        size = sprintf(buffer+len,
                                "%-17s0x%-10x0x%-10x%s",
                                in_ntoa(entry->ip),
                                (unsigned int)entry->dev->type,
                                entry->flags,
                                hbuffer);
#if RT_CACHE_DEBUG < 2
                        size += sprintf(buffer+len+size,
                                 "     %-17s %s\n",
                                 entry->mask==DEF_ARP_NETMASK ?
                                 "*" : in_ntoa(entry->mask), entry->dev->name);
#else
                        size += sprintf(buffer+len+size,
                                 "     %-17s %s\t%d\t%1d\n",
                                 entry->mask==DEF_ARP_NETMASK ?
                                 "*" : in_ntoa(entry->mask), entry->dev->name,
                                 entry->hh ? entry->hh->hh_refcnt : -1,
                                 entry->hh ? entry->hh->hh_uptodate : 0);
#endif
 
                        len += size;
                        pos += size;
 
                        if (pos <= offset)
                                len=0;
                        if (pos >= offset+length)
                                goto done;
                }
        }
done:
        arp_unlock();
 
        *start = buffer+len-(pos-offset);       /* Start of wanted data */
        len = pos-offset;                       /* Start slop */
        if (len>length)
                len = length;                   /* Ending slop */
        return len;
}
 
 
 
/*
 *      Called once on startup.
 */
 
static struct packet_type arp_packet_type =
{
        0,       /* Should be: __constant_htons(ETH_P_ARP) - but this _doesn't_ come out constant! */
        NULL,           /* All devices */
        arp_rcv,
        NULL,
        NULL
};
 
static struct notifier_block arp_dev_notifier={
        arp_device_event,
        NULL,
 
};
 
#ifdef CONFIG_PROC_FS
static struct proc_dir_entry arp_proc_dir_entry = {
                PROC_NET_ARP, 3, "arp",
                S_IFREG | S_IRUGO, 1, 0, 0,
                0, &proc_net_inode_operations,
                arp_get_info
        };
#endif
 
 
void arp_init (void)
{
        /* Register the packet type */
        arp_packet_type.type=htons(ETH_P_ARP);
        dev_add_pack(&arp_packet_type);
        /* Start with the regular checks for expired arp entries. */
        add_timer(&arp_timer);
        /* Register for device down reports */
        register_netdevice_notifier(&arp_dev_notifier);
 
#ifdef CONFIG_PROC_FS
        proc_net_register(&arp_proc_dir_entry);
#endif
 
#ifdef CONFIG_ARPD
        netlink_attach(NETLINK_ARPD, arpd_callback);
#endif
}
 
#ifdef CONFIG_AX25_MODULE
 
/*
 *      ax25 -> ascii conversion
 */
char *ax2asc(ax25_address *a)
{
        static char buf[11];
        char c, *s;
        int n;
 
        for (n = 0, s = buf; n < 6; n++) {
                c = (a->ax25_call[n] >> 1) & 0x7F;
 
                if (c != ' ') *s++ = c;
        }
 
        *s++ = '-';
 
        if ((n = ((a->ax25_call[6] >> 1) & 0x0F)) > 9) {
                *s++ = '1';
                n -= 10;
        }
 
        *s++ = n + '0';
        *s++ = '\0';
 
        if (*buf == '\0' || *buf == '-')
           return "*";
 
        return buf;
 
}
 
#endif
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[/] [or1k/] [trunk/] [rc203soc/] [sw/] [uClinux/] [net/] [ipv4/] [arp.c] - Blame information for rev 1629

Line No.	Rev	Author	Line
1	1629	jcastillo	`/* linux/net/inet/arp.c`
2			`*`
3			`* Copyright (C) 1994 by Florian La Roche`
4			`*`
5			`* This module implements the Address Resolution Protocol ARP (RFC 826),`
6			`* which is used to convert IP addresses (or in the future maybe other`
7			`* high-level addresses) into a low-level hardware address (like an Ethernet`
8			`* address).`
9			`*`
10			`* FIXME:`
11			`* Experiment with better retransmit timers`
12			`* Clean up the timer deletions`
13			`* If you create a proxy entry, set your interface address to the address`
14			`* and then delete it, proxies may get out of sync with reality -`
15			`* check this.`
16			`*`
17			`* This program is free software; you can redistribute it and/or`
18			`* modify it under the terms of the GNU General Public License`
19			`* as published by the Free Software Foundation; either version`
20			`* 2 of the License, or (at your option) any later version.`
21			`*`
22			`* Fixes:`
23			`* Alan Cox : Removed the ethernet assumptions in`
24			`* Florian's code`
25			`* Alan Cox : Fixed some small errors in the ARP`
26			`* logic`
27			`* Alan Cox : Allow >4K in /proc`
28			`* Alan Cox : Make ARP add its own protocol entry`
29			`* Ross Martin : Rewrote arp_rcv() and arp_get_info()`
30			`* Stephen Henson : Add AX25 support to arp_get_info()`
31			`* Alan Cox : Drop data when a device is downed.`
32			`* Alan Cox : Use init_timer().`
33			`* Alan Cox : Double lock fixes.`
34			`* Martin Seine : Move the arphdr structure`
35			`* to if_arp.h for compatibility.`
36			`* with BSD based programs.`
37			`* Andrew Tridgell : Added ARP netmask code and`
38			`* re-arranged proxy handling.`
39			`* Alan Cox : Changed to use notifiers.`
40			`* Niibe Yutaka : Reply for this device or proxies only.`