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arp.c

/* linux/net/ipv4/arp.c
 *
 * Version: $Id: arp.c,v 1.99 2001/08/30 22:55:42 davem Exp $
 *
 * 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).
 *
 * 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
 *          Mike McLagan    : Routing by source
 *          Stuart Cheshire   :     Metricom and grat arp fixes
 *                            *** FOR 2.1 clean this up ***
 *          Lawrence V. Stefani: (08/12/96) Added FDDI support.
 *          Alan Cox    :     Took the AP1000 nasty FDDI hack and
 *                            folded into the mainstream FDDI code.
 *                            Ack spit, Linus how did you allow that
 *                            one in...
 *          Jes Sorensen      :     Make FDDI work again in 2.1.x and
 *                            clean up the APFDDI & gen. FDDI bits.
 *          Alexey Kuznetsov: new arp state machine;
 *                            now it is in net/core/neighbour.c.
 *          Krzysztof Halasa: Added Frame Relay ARP support.
 *          Arnaldo C. Melo : convert /proc/net/arp to seq_file
 *          Shmulik Hen:            Split arp_send to arp_create and
 *                            arp_xmit so intermediate drivers like
 *                            bonding can change the skb before
 *                            sending (e.g. insert 8021q tag).
 *          Harald Welte      :     convert to make use of jenkins hash
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/capability.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/inetdevice.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/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/net.h>
#include <linux/rcupdate.h>
#include <linux/jhash.h>
#ifdef CONFIG_SYSCTL
#include <linux/sysctl.h>
#endif

#include <net/net_namespace.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>
#include <net/ax25.h>
#include <net/netrom.h>
#if defined(CONFIG_ATM_CLIP) || defined(CONFIG_ATM_CLIP_MODULE)
#include <net/atmclip.h>
struct neigh_table *clip_tbl_hook;
#endif

#include <asm/system.h>
#include <asm/uaccess.h>

#include <linux/netfilter_arp.h>

/*
 *    Interface to generic neighbour cache.
 */
static u32 arp_hash(const void *pkey, const struct net_device *dev);
static int arp_constructor(struct neighbour *neigh);
static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb);
static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb);
static void parp_redo(struct sk_buff *skb);

static struct neigh_ops arp_generic_ops = {
      .family =         AF_INET,
      .solicit =        arp_solicit,
      .error_report =         arp_error_report,
      .output =         neigh_resolve_output,
      .connected_output =     neigh_connected_output,
      .hh_output =            dev_queue_xmit,
      .queue_xmit =           dev_queue_xmit,
};

static struct neigh_ops arp_hh_ops = {
      .family =         AF_INET,
      .solicit =        arp_solicit,
      .error_report =         arp_error_report,
      .output =         neigh_resolve_output,
      .connected_output =     neigh_resolve_output,
      .hh_output =            dev_queue_xmit,
      .queue_xmit =           dev_queue_xmit,
};

static struct neigh_ops arp_direct_ops = {
      .family =         AF_INET,
      .output =         dev_queue_xmit,
      .connected_output =     dev_queue_xmit,
      .hh_output =            dev_queue_xmit,
      .queue_xmit =           dev_queue_xmit,
};

struct neigh_ops arp_broken_ops = {
      .family =         AF_INET,
      .solicit =        arp_solicit,
      .error_report =         arp_error_report,
      .output =         neigh_compat_output,
      .connected_output =     neigh_compat_output,
      .hh_output =            dev_queue_xmit,
      .queue_xmit =           dev_queue_xmit,
};

struct neigh_table arp_tbl = {
      .family =   AF_INET,
      .entry_size =     sizeof(struct neighbour) + 4,
      .key_len =  4,
      .hash =           arp_hash,
      .constructor =    arp_constructor,
      .proxy_redo =     parp_redo,
      .id =       "arp_cache",
      .parms = {
            .tbl =                  &arp_tbl,
            .base_reachable_time =  30 * HZ,
            .retrans_time =   1 * HZ,
            .gc_staletime =   60 * HZ,
            .reachable_time =       30 * HZ,
            .delay_probe_time =     5 * HZ,
            .queue_len =            3,
            .ucast_probes =   3,
            .mcast_probes =   3,
            .anycast_delay =  1 * HZ,
            .proxy_delay =          (8 * HZ) / 10,
            .proxy_qlen =           64,
            .locktime =       1 * HZ,
      },
      .gc_interval =    30 * HZ,
      .gc_thresh1 =     128,
      .gc_thresh2 =     512,
      .gc_thresh3 =     1024,
};

int arp_mc_map(__be32 addr, u8 *haddr, struct net_device *dev, int dir)
{
      switch (dev->type) {
      case ARPHRD_ETHER:
      case ARPHRD_FDDI:
      case ARPHRD_IEEE802:
            ip_eth_mc_map(addr, haddr);
            return 0;
      case ARPHRD_IEEE802_TR:
            ip_tr_mc_map(addr, haddr);
            return 0;
      case ARPHRD_INFINIBAND:
            ip_ib_mc_map(addr, haddr);
            return 0;
      default:
            if (dir) {
                  memcpy(haddr, dev->broadcast, dev->addr_len);
                  return 0;
            }
      }
      return -EINVAL;
}


static u32 arp_hash(const void *pkey, const struct net_device *dev)
{
      return jhash_2words(*(u32 *)pkey, dev->ifindex, arp_tbl.hash_rnd);
}

static int arp_constructor(struct neighbour *neigh)
{
      __be32 addr = *(__be32*)neigh->primary_key;
      struct net_device *dev = neigh->dev;
      struct in_device *in_dev;
      struct neigh_parms *parms;

      neigh->type = inet_addr_type(addr);

      rcu_read_lock();
      in_dev = __in_dev_get_rcu(dev);
      if (in_dev == NULL) {
            rcu_read_unlock();
            return -EINVAL;
      }

      parms = in_dev->arp_parms;
      __neigh_parms_put(neigh->parms);
      neigh->parms = neigh_parms_clone(parms);
      rcu_read_unlock();

      if (!dev->header_ops) {
            neigh->nud_state = NUD_NOARP;
            neigh->ops = &arp_direct_ops;
            neigh->output = neigh->ops->queue_xmit;
      } else {
            /* Good devices (checked by reading texts, but only Ethernet is
               tested)

               ARPHRD_ETHER: (ethernet, apfddi)
               ARPHRD_FDDI: (fddi)
               ARPHRD_IEEE802: (tr)
               ARPHRD_METRICOM: (strip)
               ARPHRD_ARCNET:
               etc. etc. etc.

               ARPHRD_IPDDP will also work, if author repairs it.
               I did not it, because this driver does not work even
               in old paradigm.
             */

#if 1
            /* So... these "amateur" devices are hopeless.
               The only thing, that I can say now:
               It is very sad that we need to keep ugly obsolete
               code to make them happy.

               They should be moved to more reasonable state, now
               they use rebuild_header INSTEAD OF hard_start_xmit!!!
               Besides that, they are sort of out of date
               (a lot of redundant clones/copies, useless in 2.1),
               I wonder why people believe that they work.
             */
            switch (dev->type) {
            default:
                  break;
            case ARPHRD_ROSE:
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
            case ARPHRD_AX25:
#if defined(CONFIG_NETROM) || defined(CONFIG_NETROM_MODULE)
            case ARPHRD_NETROM:
#endif
                  neigh->ops = &arp_broken_ops;
                  neigh->output = neigh->ops->output;
                  return 0;
#endif
            ;}
#endif
            if (neigh->type == RTN_MULTICAST) {
                  neigh->nud_state = NUD_NOARP;
                  arp_mc_map(addr, neigh->ha, dev, 1);
            } else if (dev->flags&(IFF_NOARP|IFF_LOOPBACK)) {
                  neigh->nud_state = NUD_NOARP;
                  memcpy(neigh->ha, dev->dev_addr, dev->addr_len);
            } else if (neigh->type == RTN_BROADCAST || dev->flags&IFF_POINTOPOINT) {
                  neigh->nud_state = NUD_NOARP;
                  memcpy(neigh->ha, dev->broadcast, dev->addr_len);
            }

            if (dev->header_ops->cache)
                  neigh->ops = &arp_hh_ops;
            else
                  neigh->ops = &arp_generic_ops;

            if (neigh->nud_state&NUD_VALID)
                  neigh->output = neigh->ops->connected_output;
            else
                  neigh->output = neigh->ops->output;
      }
      return 0;
}

static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb)
{
      dst_link_failure(skb);
      kfree_skb(skb);
}

static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
{
      __be32 saddr = 0;
      u8  *dst_ha = NULL;
      struct net_device *dev = neigh->dev;
      __be32 target = *(__be32*)neigh->primary_key;
      int probes = atomic_read(&neigh->probes);
      struct in_device *in_dev = in_dev_get(dev);

      if (!in_dev)
            return;

      switch (IN_DEV_ARP_ANNOUNCE(in_dev)) {
      default:
      case 0:           /* By default announce any local IP */
            if (skb && inet_addr_type(ip_hdr(skb)->saddr) == RTN_LOCAL)
                  saddr = ip_hdr(skb)->saddr;
            break;
      case 1:           /* Restrict announcements of saddr in same subnet */
            if (!skb)
                  break;
            saddr = ip_hdr(skb)->saddr;
            if (inet_addr_type(saddr) == RTN_LOCAL) {
                  /* saddr should be known to target */
                  if (inet_addr_onlink(in_dev, target, saddr))
                        break;
            }
            saddr = 0;
            break;
      case 2:           /* Avoid secondary IPs, get a primary/preferred one */
            break;
      }

      if (in_dev)
            in_dev_put(in_dev);
      if (!saddr)
            saddr = inet_select_addr(dev, target, RT_SCOPE_LINK);

      if ((probes -= neigh->parms->ucast_probes) < 0) {
            if (!(neigh->nud_state&NUD_VALID))
                  printk(KERN_DEBUG "trying to ucast probe in NUD_INVALID\n");
            dst_ha = neigh->ha;
            read_lock_bh(&neigh->lock);
      } else if ((probes -= neigh->parms->app_probes) < 0) {
#ifdef CONFIG_ARPD
            neigh_app_ns(neigh);
#endif
            return;
      }

      arp_send(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
             dst_ha, dev->dev_addr, NULL);
      if (dst_ha)
            read_unlock_bh(&neigh->lock);
}

static int arp_ignore(struct in_device *in_dev, struct net_device *dev,
                  __be32 sip, __be32 tip)
{
      int scope;

      switch (IN_DEV_ARP_IGNORE(in_dev)) {
      case 0:     /* Reply, the tip is already validated */
            return 0;
      case 1:     /* Reply only if tip is configured on the incoming interface */
            sip = 0;
            scope = RT_SCOPE_HOST;
            break;
      case 2:     /*
             * Reply only if tip is configured on the incoming interface
             * and is in same subnet as sip
             */
            scope = RT_SCOPE_HOST;
            break;
      case 3:     /* Do not reply for scope host addresses */
            sip = 0;
            scope = RT_SCOPE_LINK;
            dev = NULL;
            break;
      case 4:     /* Reserved */
      case 5:
      case 6:
      case 7:
            return 0;
      case 8:     /* Do not reply */
            return 1;
      default:
            return 0;
      }
      return !inet_confirm_addr(dev, sip, tip, scope);
}

static int arp_filter(__be32 sip, __be32 tip, struct net_device *dev)
{
      struct flowi fl = { .nl_u = { .ip4_u = { .daddr = sip,
                                     .saddr = tip } } };
      struct rtable *rt;
      int flag = 0;
      /*unsigned long now; */

      if (ip_route_output_key(&rt, &fl) < 0)
            return 1;
      if (rt->u.dst.dev != dev) {
            NET_INC_STATS_BH(LINUX_MIB_ARPFILTER);
            flag = 1;
      }
      ip_rt_put(rt);
      return flag;
}

/* OBSOLETE FUNCTIONS */

/*
 *    Find an arp mapping in the cache. If not found, post a request.
 *
 *    It is very UGLY routine: it DOES NOT use skb->dst->neighbour,
 *    even if it exists. It is supposed that skb->dev was mangled
 *    by a virtual device (eql, shaper). Nobody but broken devices
 *    is allowed to use this function, it is scheduled to be removed. --ANK
 */

static int arp_set_predefined(int addr_hint, unsigned char * haddr, __be32 paddr, struct net_device * dev)
{
      switch (addr_hint) {
      case RTN_LOCAL:
            printk(KERN_DEBUG "ARP: arp called for own IP address\n");
            memcpy(haddr, dev->dev_addr, dev->addr_len);
            return 1;
      case RTN_MULTICAST:
            arp_mc_map(paddr, haddr, dev, 1);
            return 1;
      case RTN_BROADCAST:
            memcpy(haddr, dev->broadcast, dev->addr_len);
            return 1;
      }
      return 0;
}


int arp_find(unsigned char *haddr, struct sk_buff *skb)
{
      struct net_device *dev = skb->dev;
      __be32 paddr;
      struct neighbour *n;

      if (!skb->dst) {
            printk(KERN_DEBUG "arp_find is called with dst==NULL\n");
            kfree_skb(skb);
            return 1;
      }

      paddr = ((struct rtable*)skb->dst)->rt_gateway;

      if (arp_set_predefined(inet_addr_type(paddr), haddr, paddr, dev))
            return 0;

      n = __neigh_lookup(&arp_tbl, &paddr, dev, 1);

      if (n) {
            n->used = jiffies;
            if (n->nud_state&NUD_VALID || neigh_event_send(n, skb) == 0) {
                  read_lock_bh(&n->lock);
                  memcpy(haddr, n->ha, dev->addr_len);
                  read_unlock_bh(&n->lock);
                  neigh_release(n);
                  return 0;
            }
            neigh_release(n);
      } else
            kfree_skb(skb);
      return 1;
}

/* END OF OBSOLETE FUNCTIONS */

int arp_bind_neighbour(struct dst_entry *dst)
{
      struct net_device *dev = dst->dev;
      struct neighbour *n = dst->neighbour;

      if (dev == NULL)
            return -EINVAL;
      if (n == NULL) {
            __be32 nexthop = ((struct rtable*)dst)->rt_gateway;
            if (dev->flags&(IFF_LOOPBACK|IFF_POINTOPOINT))
                  nexthop = 0;
            n = __neigh_lookup_errno(
#if defined(CONFIG_ATM_CLIP) || defined(CONFIG_ATM_CLIP_MODULE)
                dev->type == ARPHRD_ATM ? clip_tbl_hook :
#endif
                &arp_tbl, &nexthop, dev);
            if (IS_ERR(n))
                  return PTR_ERR(n);
            dst->neighbour = n;
      }
      return 0;
}

/*
 * Check if we can use proxy ARP for this path
 */

static inline int arp_fwd_proxy(struct in_device *in_dev, struct rtable *rt)
{
      struct in_device *out_dev;
      int imi, omi = -1;

      if (!IN_DEV_PROXY_ARP(in_dev))
            return 0;

      if ((imi = IN_DEV_MEDIUM_ID(in_dev)) == 0)
            return 1;
      if (imi == -1)
            return 0;

      /* place to check for proxy_arp for routes */

      if ((out_dev = in_dev_get(rt->u.dst.dev)) != NULL) {
            omi = IN_DEV_MEDIUM_ID(out_dev);
            in_dev_put(out_dev);
      }
      return (omi != imi && omi != -1);
}

/*
 *    Interface to link layer: send routine and receive handler.
 */

/*
 *    Create an arp packet. If (dest_hw == NULL), we create a broadcast
 *    message.
 */
struct sk_buff *arp_create(int type, int ptype, __be32 dest_ip,
                     struct net_device *dev, __be32 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;

      /*
       *    Allocate a buffer
       */

      skb = alloc_skb(sizeof(struct arphdr)+ 2*(dev->addr_len+4)
                        + LL_RESERVED_SPACE(dev), GFP_ATOMIC);
      if (skb == NULL)
            return NULL;

      skb_reserve(skb, LL_RESERVED_SPACE(dev));
      skb_reset_network_header(skb);
      arp = (struct arphdr *) skb_put(skb,sizeof(struct arphdr) + 2*(dev->addr_len+4));
      skb->dev = dev;
      skb->protocol = htons(ETH_P_ARP);
      if (src_hw == NULL)
            src_hw = dev->dev_addr;
      if (dest_hw == NULL)
            dest_hw = dev->broadcast;

      /*
       *    Fill the device header for the ARP frame
       */
      if (dev_hard_header(skb, dev, ptype, dest_hw, src_hw, skb->len) < 0)
            goto out;

      /*
       * 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).
       */
      /*
       *    Exceptions everywhere. AX.25 uses the AX.25 PID value not the
       *    DIX code for the protocol. Make these device structure fields.
       */
      switch (dev->type) {
      default:
            arp->ar_hrd = htons(dev->type);
            arp->ar_pro = htons(ETH_P_IP);
            break;

#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
      case ARPHRD_AX25:
            arp->ar_hrd = htons(ARPHRD_AX25);
            arp->ar_pro = htons(AX25_P_IP);
            break;

#if defined(CONFIG_NETROM) || defined(CONFIG_NETROM_MODULE)
      case ARPHRD_NETROM:
            arp->ar_hrd = htons(ARPHRD_NETROM);
            arp->ar_pro = htons(AX25_P_IP);
            break;
#endif
#endif

#ifdef CONFIG_FDDI
      case ARPHRD_FDDI:
            arp->ar_hrd = htons(ARPHRD_ETHER);
            arp->ar_pro = htons(ETH_P_IP);
            break;
#endif
#ifdef CONFIG_TR
      case ARPHRD_IEEE802_TR:
            arp->ar_hrd = htons(ARPHRD_IEEE802);
            arp->ar_pro = htons(ETH_P_IP);
            break;
#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);

      return skb;

out:
      kfree_skb(skb);
      return NULL;
}

/*
 *    Send an arp packet.
 */
void arp_xmit(struct sk_buff *skb)
{
      /* Send it off, maybe filter it using firewalling first.  */
      NF_HOOK(NF_ARP, NF_ARP_OUT, skb, NULL, skb->dev, dev_queue_xmit);
}

/*
 *    Create and send an arp packet.
 */
void arp_send(int type, int ptype, __be32 dest_ip,
            struct net_device *dev, __be32 src_ip,
            unsigned char *dest_hw, unsigned char *src_hw,
            unsigned char *target_hw)
{
      struct sk_buff *skb;

      /*
       *    No arp on this interface.
       */

      if (dev->flags&IFF_NOARP)
            return;

      skb = arp_create(type, ptype, dest_ip, dev, src_ip,
                   dest_hw, src_hw, target_hw);
      if (skb == NULL) {
            return;
      }

      arp_xmit(skb);
}

/*
 *    Process an arp request.
 */

static int arp_process(struct sk_buff *skb)
{
      struct net_device *dev = skb->dev;
      struct in_device *in_dev = in_dev_get(dev);
      struct arphdr *arp;
      unsigned char *arp_ptr;
      struct rtable *rt;
      unsigned char *sha;
      __be32 sip, tip;
      u16 dev_type = dev->type;
      int addr_type;
      struct neighbour *n;

      /* arp_rcv below verifies the ARP header and verifies the device
       * is ARP'able.
       */

      if (in_dev == NULL)
            goto out;

      arp = arp_hdr(skb);

      switch (dev_type) {
      default:
            if (arp->ar_pro != htons(ETH_P_IP) ||
                htons(dev_type) != arp->ar_hrd)
                  goto out;
            break;
      case ARPHRD_ETHER:
      case ARPHRD_IEEE802_TR:
      case ARPHRD_FDDI:
      case ARPHRD_IEEE802:
            /*
             * ETHERNET, Token Ring and Fibre Channel (which are IEEE 802
             * devices, according to RFC 2625) devices will accept ARP
             * hardware types of either 1 (Ethernet) or 6 (IEEE 802.2).
             * This is the case also of FDDI, where the RFC 1390 says that
             * FDDI devices should accept ARP hardware of (1) Ethernet,
             * however, to be more robust, we'll accept both 1 (Ethernet)
             * or 6 (IEEE 802.2)
             */
            if ((arp->ar_hrd != htons(ARPHRD_ETHER) &&
                 arp->ar_hrd != htons(ARPHRD_IEEE802)) ||
                arp->ar_pro != htons(ETH_P_IP))
                  goto out;
            break;
      case ARPHRD_AX25:
            if (arp->ar_pro != htons(AX25_P_IP) ||
                arp->ar_hrd != htons(ARPHRD_AX25))
                  goto out;
            break;
      case ARPHRD_NETROM:
            if (arp->ar_pro != htons(AX25_P_IP) ||
                arp->ar_hrd != htons(ARPHRD_NETROM))
                  goto out;
            break;
      }

      /* Understand only these message types */

      if (arp->ar_op != htons(ARPOP_REPLY) &&
          arp->ar_op != htons(ARPOP_REQUEST))
            goto out;

/*
 *    Extract fields
 */
      arp_ptr= (unsigned char *)(arp+1);
      sha   = arp_ptr;
      arp_ptr += dev->addr_len;
      memcpy(&sip, arp_ptr, 4);
      arp_ptr += 4;
      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))
            goto out;

/*
 *     Special case: We must set Frame Relay source Q.922 address
 */
      if (dev_type == ARPHRD_DLCI)
            sha = dev->broadcast;

/*
 *  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.
 */

      /* Special case: IPv4 duplicate address detection packet (RFC2131) */
      if (sip == 0) {
            if (arp->ar_op == htons(ARPOP_REQUEST) &&
                inet_addr_type(tip) == RTN_LOCAL &&
                !arp_ignore(in_dev,dev,sip,tip))
                  arp_send(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip, sha,
                         dev->dev_addr, sha);
            goto out;
      }

      if (arp->ar_op == htons(ARPOP_REQUEST) &&
          ip_route_input(skb, tip, sip, 0, dev) == 0) {

            rt = (struct rtable*)skb->dst;
            addr_type = rt->rt_type;

            if (addr_type == RTN_LOCAL) {
                  n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
                  if (n) {
                        int dont_send = 0;

                        if (!dont_send)
                              dont_send |= arp_ignore(in_dev,dev,sip,tip);
                        if (!dont_send && IN_DEV_ARPFILTER(in_dev))
                              dont_send |= arp_filter(sip,tip,dev);
                        if (!dont_send)
                              arp_send(ARPOP_REPLY,ETH_P_ARP,sip,dev,tip,sha,dev->dev_addr,sha);

                        neigh_release(n);
                  }
                  goto out;
            } else if (IN_DEV_FORWARD(in_dev)) {
                  if ((rt->rt_flags&RTCF_DNAT) ||
                      (addr_type == RTN_UNICAST  && rt->u.dst.dev != dev &&
                       (arp_fwd_proxy(in_dev, rt) || pneigh_lookup(&arp_tbl, &tip, dev, 0)))) {
                        n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
                        if (n)
                              neigh_release(n);

                        if (NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED ||
                            skb->pkt_type == PACKET_HOST ||
                            in_dev->arp_parms->proxy_delay == 0) {
                              arp_send(ARPOP_REPLY,ETH_P_ARP,sip,dev,tip,sha,dev->dev_addr,sha);
                        } else {
                              pneigh_enqueue(&arp_tbl, in_dev->arp_parms, skb);
                              in_dev_put(in_dev);
                              return 0;
                        }
                        goto out;
                  }
            }
      }

      /* Update our ARP tables */

      n = __neigh_lookup(&arp_tbl, &sip, dev, 0);

      if (IPV4_DEVCONF_ALL(ARP_ACCEPT)) {
            /* Unsolicited ARP is not accepted by default.
               It is possible, that this option should be enabled for some
               devices (strip is candidate)
             */
            if (n == NULL &&
                arp->ar_op == htons(ARPOP_REPLY) &&
                inet_addr_type(sip) == RTN_UNICAST)
                  n = __neigh_lookup(&arp_tbl, &sip, dev, 1);
      }

      if (n) {
            int state = NUD_REACHABLE;
            int override;

            /* If several different ARP replies follows back-to-back,
               use the FIRST one. It is possible, if several proxy
               agents are active. Taking the first reply prevents
               arp trashing and chooses the fastest router.
             */
            override = time_after(jiffies, n->updated + n->parms->locktime);

            /* Broadcast replies and request packets
               do not assert neighbour reachability.
             */
            if (arp->ar_op != htons(ARPOP_REPLY) ||
                skb->pkt_type != PACKET_HOST)
                  state = NUD_STALE;
            neigh_update(n, sha, state, override ? NEIGH_UPDATE_F_OVERRIDE : 0);
            neigh_release(n);
      }

out:
      if (in_dev)
            in_dev_put(in_dev);
      kfree_skb(skb);
      return 0;
}

static void parp_redo(struct sk_buff *skb)
{
      arp_process(skb);
}


/*
 *    Receive an arp request from the device layer.
 */

static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
               struct packet_type *pt, struct net_device *orig_dev)
{
      struct arphdr *arp;

      if (dev->nd_net != &init_net)
            goto freeskb;

      /* ARP header, plus 2 device addresses, plus 2 IP addresses.  */
      if (!pskb_may_pull(skb, (sizeof(struct arphdr) +
                         (2 * dev->addr_len) +
                         (2 * sizeof(u32)))))
            goto freeskb;

      arp = arp_hdr(skb);
      if (arp->ar_hln != dev->addr_len ||
          dev->flags & IFF_NOARP ||
          skb->pkt_type == PACKET_OTHERHOST ||
          skb->pkt_type == PACKET_LOOPBACK ||
          arp->ar_pln != 4)
            goto freeskb;

      if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
            goto out_of_mem;

      memset(NEIGH_CB(skb), 0, sizeof(struct neighbour_cb));

      return NF_HOOK(NF_ARP, NF_ARP_IN, skb, dev, NULL, arp_process);

freeskb:
      kfree_skb(skb);
out_of_mem:
      return 0;
}

/*
 *    User level interface (ioctl)
 */

/*
 *    Set (create) an ARP cache entry.
 */

static int arp_req_set(struct arpreq *r, struct net_device * dev)
{
      __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
      struct neighbour *neigh;
      int err;

      if (r->arp_flags&ATF_PUBL) {
            __be32 mask = ((struct sockaddr_in *) &r->arp_netmask)->sin_addr.s_addr;
            if (mask && mask != htonl(0xFFFFFFFF))
                  return -EINVAL;
            if (!dev && (r->arp_flags & ATF_COM)) {
                  dev = dev_getbyhwaddr(&init_net, r->arp_ha.sa_family, r->arp_ha.sa_data);
                  if (!dev)
                        return -ENODEV;
            }
            if (mask) {
                  if (pneigh_lookup(&arp_tbl, &ip, dev, 1) == NULL)
                        return -ENOBUFS;
                  return 0;
            }
            if (dev == NULL) {
                  IPV4_DEVCONF_ALL(PROXY_ARP) = 1;
                  return 0;
            }
            if (__in_dev_get_rtnl(dev)) {
                  IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, 1);
                  return 0;
            }
            return -ENXIO;
      }

      if (r->arp_flags & ATF_PERM)
            r->arp_flags |= ATF_COM;
      if (dev == NULL) {
            struct flowi fl = { .nl_u = { .ip4_u = { .daddr = ip,
                                           .tos = RTO_ONLINK } } };
            struct rtable * rt;
            if ((err = ip_route_output_key(&rt, &fl)) != 0)
                  return err;
            dev = rt->u.dst.dev;
            ip_rt_put(rt);
            if (!dev)
                  return -EINVAL;
      }
      switch (dev->type) {
#ifdef CONFIG_FDDI
      case 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).
             */
            if (r->arp_ha.sa_family != ARPHRD_FDDI &&
                r->arp_ha.sa_family != ARPHRD_ETHER &&
                r->arp_ha.sa_family != ARPHRD_IEEE802)
                  return -EINVAL;
            break;
#endif
      default:
            if (r->arp_ha.sa_family != dev->type)
                  return -EINVAL;
            break;
      }

      neigh = __neigh_lookup_errno(&arp_tbl, &ip, dev);
      err = PTR_ERR(neigh);
      if (!IS_ERR(neigh)) {
            unsigned state = NUD_STALE;
            if (r->arp_flags & ATF_PERM)
                  state = NUD_PERMANENT;
            err = neigh_update(neigh, (r->arp_flags&ATF_COM) ?
                           r->arp_ha.sa_data : NULL, state,
                           NEIGH_UPDATE_F_OVERRIDE|
                           NEIGH_UPDATE_F_ADMIN);
            neigh_release(neigh);
      }
      return err;
}

static unsigned arp_state_to_flags(struct neighbour *neigh)
{
      unsigned flags = 0;
      if (neigh->nud_state&NUD_PERMANENT)
            flags = ATF_PERM|ATF_COM;
      else if (neigh->nud_state&NUD_VALID)
            flags = ATF_COM;
      return flags;
}

/*
 *    Get an ARP cache entry.
 */

static int arp_req_get(struct arpreq *r, struct net_device *dev)
{
      __be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
      struct neighbour *neigh;
      int err = -ENXIO;

      neigh = neigh_lookup(&arp_tbl, &ip, dev);
      if (neigh) {
            read_lock_bh(&neigh->lock);
            memcpy(r->arp_ha.sa_data, neigh->ha, dev->addr_len);
            r->arp_flags = arp_state_to_flags(neigh);
            read_unlock_bh(&neigh->lock);
            r->arp_ha.sa_family = dev->type;
            strlcpy(r->arp_dev, dev->name, sizeof(r->arp_dev));
            neigh_release(neigh);
            err = 0;
      }
      return err;
}

static int arp_req_delete(struct arpreq *r, struct net_device * dev)
{
      int err;
      __be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
      struct neighbour *neigh;

      if (r->arp_flags & ATF_PUBL) {
            __be32 mask =
                   ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;
            if (mask == htonl(0xFFFFFFFF))
                  return pneigh_delete(&arp_tbl, &ip, dev);
            if (mask == 0) {
                  if (dev == NULL) {
                        IPV4_DEVCONF_ALL(PROXY_ARP) = 0;
                        return 0;
                  }
                  if (__in_dev_get_rtnl(dev)) {
                        IN_DEV_CONF_SET(__in_dev_get_rtnl(dev),
                                    PROXY_ARP, 0);
                        return 0;
                  }
                  return -ENXIO;
            }
            return -EINVAL;
      }

      if (dev == NULL) {
            struct flowi fl = { .nl_u = { .ip4_u = { .daddr = ip,
                                           .tos = RTO_ONLINK } } };
            struct rtable * rt;
            if ((err = ip_route_output_key(&rt, &fl)) != 0)
                  return err;
            dev = rt->u.dst.dev;
            ip_rt_put(rt);
            if (!dev)
                  return -EINVAL;
      }
      err = -ENXIO;
      neigh = neigh_lookup(&arp_tbl, &ip, dev);
      if (neigh) {
            if (neigh->nud_state&~NUD_NOARP)
                  err = neigh_update(neigh, NULL, NUD_FAILED,
                                 NEIGH_UPDATE_F_OVERRIDE|
                                 NEIGH_UPDATE_F_ADMIN);
            neigh_release(neigh);
      }
      return err;
}

/*
 *    Handle an ARP layer I/O control request.
 */

int arp_ioctl(unsigned int cmd, void __user *arg)
{
      int err;
      struct arpreq r;
      struct net_device *dev = NULL;

      switch (cmd) {
            case SIOCDARP:
            case SIOCSARP:
                  if (!capable(CAP_NET_ADMIN))
                        return -EPERM;
            case SIOCGARP:
                  err = copy_from_user(&r, arg, sizeof(struct arpreq));
                  if (err)
                        return -EFAULT;
                  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|ATF_DONTPUB)))
            return -EINVAL;
      if (!(r.arp_flags & ATF_NETMASK))
            ((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr =
                                             htonl(0xFFFFFFFFUL);
      rtnl_lock();
      if (r.arp_dev[0]) {
            err = -ENODEV;
            if ((dev = __dev_get_by_name(&init_net, r.arp_dev)) == NULL)
                  goto out;

            /* Mmmm... It is wrong... ARPHRD_NETROM==0 */
            if (!r.arp_ha.sa_family)
                  r.arp_ha.sa_family = dev->type;
            err = -EINVAL;
            if ((r.arp_flags & ATF_COM) && r.arp_ha.sa_family != dev->type)
                  goto out;
      } else if (cmd == SIOCGARP) {
            err = -ENODEV;
            goto out;
      }

      switch (cmd) {
      case SIOCDARP:
            err = arp_req_delete(&r, dev);
            break;
      case SIOCSARP:
            err = arp_req_set(&r, dev);
            break;
      case SIOCGARP:
            err = arp_req_get(&r, dev);
            if (!err && copy_to_user(arg, &r, sizeof(r)))
                  err = -EFAULT;
            break;
      }
out:
      rtnl_unlock();
      return err;
}

static int arp_netdev_event(struct notifier_block *this, unsigned long event, void *ptr)
{
      struct net_device *dev = ptr;

      if (dev->nd_net != &init_net)
            return NOTIFY_DONE;

      switch (event) {
      case NETDEV_CHANGEADDR:
            neigh_changeaddr(&arp_tbl, dev);
            rt_cache_flush(0);
            break;
      default:
            break;
      }

      return NOTIFY_DONE;
}

static struct notifier_block arp_netdev_notifier = {
      .notifier_call = arp_netdev_event,
};

/* Note, that it is not on notifier chain.
   It is necessary, that this routine was called after route cache will be
   flushed.
 */
void arp_ifdown(struct net_device *dev)
{
      neigh_ifdown(&arp_tbl, dev);
}


/*
 *    Called once on startup.
 */

static struct packet_type arp_packet_type = {
      .type =     __constant_htons(ETH_P_ARP),
      .func =     arp_rcv,
};

static int arp_proc_init(void);

void __init arp_init(void)
{
      neigh_table_init(&arp_tbl);

      dev_add_pack(&arp_packet_type);
      arp_proc_init();
#ifdef CONFIG_SYSCTL
      neigh_sysctl_register(NULL, &arp_tbl.parms, NET_IPV4,
                        NET_IPV4_NEIGH, "ipv4", NULL, NULL);
#endif
      register_netdevice_notifier(&arp_netdev_notifier);
}

#ifdef CONFIG_PROC_FS
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)

/* ------------------------------------------------------------------------ */
/*
 *    ax25 -> ASCII conversion
 */
static char *ax2asc2(ax25_address *a, char *buf)
{
      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 /* CONFIG_AX25 */

#define HBUFFERLEN 30

static void arp_format_neigh_entry(struct seq_file *seq,
                           struct neighbour *n)
{
      char hbuffer[HBUFFERLEN];
      const char hexbuf[] = "0123456789ABCDEF";
      int k, j;
      char tbuf[16];
      struct net_device *dev = n->dev;
      int hatype = dev->type;

      read_lock(&n->lock);
      /* Convert hardware address to XX:XX:XX:XX ... form. */
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
      if (hatype == ARPHRD_AX25 || hatype == ARPHRD_NETROM)
            ax2asc2((ax25_address *)n->ha, hbuffer);
      else {
#endif
      for (k = 0, j = 0; k < HBUFFERLEN - 3 && j < dev->addr_len; j++) {
            hbuffer[k++] = hexbuf[(n->ha[j] >> 4) & 15];
            hbuffer[k++] = hexbuf[n->ha[j] & 15];
            hbuffer[k++] = ':';
      }
      hbuffer[--k] = 0;
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
      }
#endif
      sprintf(tbuf, "%u.%u.%u.%u", NIPQUAD(*(u32*)n->primary_key));
      seq_printf(seq, "%-16s 0x%-10x0x%-10x%s     *        %s\n",
               tbuf, hatype, arp_state_to_flags(n), hbuffer, dev->name);
      read_unlock(&n->lock);
}

static void arp_format_pneigh_entry(struct seq_file *seq,
                            struct pneigh_entry *n)
{
      struct net_device *dev = n->dev;
      int hatype = dev ? dev->type : 0;
      char tbuf[16];

      sprintf(tbuf, "%u.%u.%u.%u", NIPQUAD(*(u32*)n->key));
      seq_printf(seq, "%-16s 0x%-10x0x%-10x%s     *        %s\n",
               tbuf, hatype, ATF_PUBL | ATF_PERM, "00:00:00:00:00:00",
               dev ? dev->name : "*");
}

static int arp_seq_show(struct seq_file *seq, void *v)
{
      if (v == SEQ_START_TOKEN) {
            seq_puts(seq, "IP address       HW type     Flags       "
                        "HW address            Mask     Device\n");
      } else {
            struct neigh_seq_state *state = seq->private;

            if (state->flags & NEIGH_SEQ_IS_PNEIGH)
                  arp_format_pneigh_entry(seq, v);
            else
                  arp_format_neigh_entry(seq, v);
      }

      return 0;
}

static void *arp_seq_start(struct seq_file *seq, loff_t *pos)
{
      /* Don't want to confuse "arp -a" w/ magic entries,
       * so we tell the generic iterator to skip NUD_NOARP.
       */
      return neigh_seq_start(seq, pos, &arp_tbl, NEIGH_SEQ_SKIP_NOARP);
}

/* ------------------------------------------------------------------------ */

static const struct seq_operations arp_seq_ops = {
      .start  = arp_seq_start,
      .next   = neigh_seq_next,
      .stop   = neigh_seq_stop,
      .show   = arp_seq_show,
};

static int arp_seq_open(struct inode *inode, struct file *file)
{
      return seq_open_private(file, &arp_seq_ops,
                  sizeof(struct neigh_seq_state));
}

static const struct file_operations arp_seq_fops = {
      .owner            = THIS_MODULE,
      .open           = arp_seq_open,
      .read           = seq_read,
      .llseek         = seq_lseek,
      .release    = seq_release_private,
};

static int __init arp_proc_init(void)
{
      if (!proc_net_fops_create(&init_net, "arp", S_IRUGO, &arp_seq_fops))
            return -ENOMEM;
      return 0;
}

#else /* CONFIG_PROC_FS */

static int __init arp_proc_init(void)
{
      return 0;
}

#endif /* CONFIG_PROC_FS */

EXPORT_SYMBOL(arp_broken_ops);
EXPORT_SYMBOL(arp_find);
EXPORT_SYMBOL(arp_create);
EXPORT_SYMBOL(arp_xmit);
EXPORT_SYMBOL(arp_send);
EXPORT_SYMBOL(arp_tbl);

#if defined(CONFIG_ATM_CLIP) || defined(CONFIG_ATM_CLIP_MODULE)
EXPORT_SYMBOL(clip_tbl_hook);
#endif

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