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/* linux/net/ipv4/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).
*
* 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
* Jesper D. Brouer: Proxy ARP PVLAN RFC 3069 support.
*/

#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/slab.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;
EXPORT_SYMBOL(clip_tbl_hook);
#endif

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

#include <linux/netfilter_arp.h>

/*
* Interface to generic neighbour cache.
*/
static u32 arp_hash(const void *pkey, const struct net_device *dev, __u32 rnd);
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 const 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,
};

static const 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,
};

static const struct neigh_ops arp_direct_ops = {
.family = AF_INET,
.output = neigh_direct_output,
.connected_output = neigh_direct_output,
};

static const 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,
};

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,
};
EXPORT_SYMBOL(arp_tbl);

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, dev->broadcast, haddr);
return 0;
case ARPHRD_IPGRE:
ip_ipgre_mc_map(addr, dev->broadcast, 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,
__u32 hash_rnd)
{
return arp_hashfn(*(u32 *)pkey, dev, 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;

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

neigh->type = inet_addr_type(dev_net(dev), addr);

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_direct_output;
} 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;
#else
break;
#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;

rcu_read_lock();
in_dev = __in_dev_get_rcu(dev);
if (!in_dev) {
rcu_read_unlock();
return;
}
switch (IN_DEV_ARP_ANNOUNCE(in_dev)) {
default:
case 0: /* By default announce any local IP */
if (skb && inet_addr_type(dev_net(dev),
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(dev_net(dev), 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;
}
rcu_read_unlock();

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

probes -= neigh->parms->ucast_probes;
if (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 {
probes -= neigh->parms->app_probes;
if (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, __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;
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(in_dev, sip, tip, scope);
}

static int arp_filter(__be32 sip, __be32 tip, struct net_device *dev)
{
struct rtable *rt;
int flag = 0;
/*unsigned long now; */
struct net *net = dev_net(dev);

rt = ip_route_output(net, sip, tip, 0, 0);
if (IS_ERR(rt))
return 1;
if (rt->dst.dev != dev) {
NET_INC_STATS_BH(net, 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(skb)) {
printk(KERN_DEBUG "arp_find is called with dst==NULL\n");
kfree_skb(skb);
return 1;
}

paddr = skb_rtable(skb)->rt_gateway;

if (arp_set_predefined(inet_addr_type(dev_net(dev), 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) {
neigh_ha_snapshot(haddr, n, dev);
neigh_release(n);
return 0;
}
neigh_release(n);
} else
kfree_skb(skb);
return 1;
}
EXPORT_SYMBOL(arp_find);

/* END OF OBSOLETE FUNCTIONS */

/*
* Check if we can use proxy ARP for this path
*/
static inline int arp_fwd_proxy(struct in_device *in_dev,
struct net_device *dev, struct rtable *rt)
{
struct in_device *out_dev;
int imi, omi = -1;

if (rt->dst.dev == dev)
return 0;

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

/* place to check for proxy_arp for routes */

out_dev = __in_dev_get_rcu(rt->dst.dev);
if (out_dev)
omi = IN_DEV_MEDIUM_ID(out_dev);

return omi != imi && omi != -1;
}

/*
* Check for RFC3069 proxy arp private VLAN (allow to send back to same dev)
*
* RFC3069 supports proxy arp replies back to the same interface. This
* is done to support (ethernet) switch features, like RFC 3069, where
* the individual ports are not allowed to communicate with each
* other, BUT they are allowed to talk to the upstream router. As
* described in RFC 3069, it is possible to allow these hosts to
* communicate through the upstream router, by proxy_arp'ing.
*
* RFC 3069: "VLAN Aggregation for Efficient IP Address Allocation"
*
* This technology is known by different names:
* In RFC 3069 it is called VLAN Aggregation.
* Cisco and Allied Telesyn call it Private VLAN.
* Hewlett-Packard call it Source-Port filtering or port-isolation.
* Ericsson call it MAC-Forced Forwarding (RFC Draft).
*
*/
static inline int arp_fwd_pvlan(struct in_device *in_dev,
struct net_device *dev, struct rtable *rt,
__be32 sip, __be32 tip)
{
/* Private VLAN is only concerned about the same ethernet segment */
if (rt->dst.dev != dev)
return 0;

/* Don't reply on self probes (often done by windowz boxes)*/
if (sip == tip)
return 0;

if (IN_DEV_PROXY_ARP_PVLAN(in_dev))
return 1;
else
return 0;
}

/*
* 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,
const unsigned char *dest_hw,
const unsigned char *src_hw,
const unsigned char *target_hw)
{
struct sk_buff *skb;
struct arphdr *arp;
unsigned char *arp_ptr;

/*
* Allocate a buffer
*/

skb = alloc_skb(arp_hdr_len(dev) + LL_ALLOCATED_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, arp_hdr_len(dev));
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

#if defined(CONFIG_FDDI) || defined(CONFIG_FDDI_MODULE)
case ARPHRD_FDDI:
arp->ar_hrd = htons(ARPHRD_ETHER);
arp->ar_pro = htons(ETH_P_IP);
break;
#endif
#if defined(CONFIG_TR) || defined(CONFIG_TR_MODULE)
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;
}
EXPORT_SYMBOL(arp_create);

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

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

/*
* 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_rcu(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;
struct net *net = dev_net(dev);

/* 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 (ipv4_is_loopback(tip) || ipv4_is_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(net, tip) == RTN_LOCAL &&
!arp_ignore(in_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_noref(skb, tip, sip, 0, dev) == 0) {

rt = skb_rtable(skb);
addr_type = rt->rt_type;

if (addr_type == RTN_LOCAL) {
int dont_send;

dont_send = arp_ignore(in_dev, sip, tip);
if (!dont_send && IN_DEV_ARPFILTER(in_dev))
dont_send = arp_filter(sip, tip, dev);
if (!dont_send) {
n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
if (n) {
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 (addr_type == RTN_UNICAST &&
(arp_fwd_proxy(in_dev, dev, rt) ||
arp_fwd_pvlan(in_dev, dev, rt, sip, tip) ||
(rt->dst.dev != dev &&
pneigh_lookup(&arp_tbl, net, &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);
return 0;
}
goto out;
}
}
}

/* Update our ARP tables */

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

if (IPV4_DEVCONF_ALL(dev_net(dev), 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) ||
(arp->ar_op == htons(ARPOP_REQUEST) && tip == sip)) &&
inet_addr_type(net, 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:
consume_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;

/* ARP header, plus 2 device addresses, plus 2 IP addresses. */
if (!pskb_may_pull(skb, arp_hdr_len(dev)))
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;

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

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

return NF_HOOK(NFPROTO_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_proxy(struct net *net, struct net_device *dev, int on)
{
if (dev == NULL) {
IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
return 0;
}
if (__in_dev_get_rtnl(dev)) {
IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, on);
return 0;
}
return -ENXIO;
}

static int arp_req_set_public(struct net *net, struct arpreq *r,
struct net_device *dev)
{
__be32 ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
__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_rcu(net, r->arp_ha.sa_family,
r->arp_ha.sa_data);
if (!dev)
return -ENODEV;
}
if (mask) {
if (pneigh_lookup(&arp_tbl, net, &ip, dev, 1) == NULL)
return -ENOBUFS;
return 0;
}

return arp_req_set_proxy(net, dev, 1);
}

static int arp_req_set(struct net *net, struct arpreq *r,
struct net_device *dev)
{
__be32 ip;
struct neighbour *neigh;
int err;

if (r->arp_flags & ATF_PUBL)
return arp_req_set_public(net, r, dev);

ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
if (r->arp_flags & ATF_PERM)
r->arp_flags |= ATF_COM;
if (dev == NULL) {
struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);

if (IS_ERR(rt))
return PTR_ERR(rt);
dev = rt->dst.dev;
ip_rt_put(rt);
if (!dev)
return -EINVAL;
}
switch (dev->type) {
#if defined(CONFIG_FDDI) || defined(CONFIG_FDDI_MODULE)
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)
{
if (neigh->nud_state&NUD_PERMANENT)
return ATF_PERM | ATF_COM;
else if (neigh->nud_state&NUD_VALID)
return ATF_COM;
else
return 0;
}

/*
* 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;
}

int arp_invalidate(struct net_device *dev, __be32 ip)
{
struct neighbour *neigh = neigh_lookup(&arp_tbl, &ip, dev);
int err = -ENXIO;

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;
}
EXPORT_SYMBOL(arp_invalidate);

static int arp_req_delete_public(struct net *net, struct arpreq *r,
struct net_device *dev)
{
__be32 ip = ((struct sockaddr_in *) &r->arp_pa)->sin_addr.s_addr;
__be32 mask = ((struct sockaddr_in *)&r->arp_netmask)->sin_addr.s_addr;

if (mask == htonl(0xFFFFFFFF))
return pneigh_delete(&arp_tbl, net, &ip, dev);

if (mask)
return -EINVAL;

return arp_req_set_proxy(net, dev, 0);
}

static int arp_req_delete(struct net *net, struct arpreq *r,
struct net_device *dev)
{
__be32 ip;

if (r->arp_flags & ATF_PUBL)
return arp_req_delete_public(net, r, dev);

ip = ((struct sockaddr_in *)&r->arp_pa)->sin_addr.s_addr;
if (dev == NULL) {
struct rtable *rt = ip_route_output(net, ip, 0, RTO_ONLINK, 0);
if (IS_ERR(rt))
return PTR_ERR(rt);
dev = rt->dst.dev;
ip_rt_put(rt);
if (!dev)
return -EINVAL;
}
return arp_invalidate(dev, ip);
}

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

int arp_ioctl(struct net *net, 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;
dev = __dev_get_by_name(net, r.arp_dev);
if (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(net, &r, dev);
break;
case SIOCSARP:
err = arp_req_set(net, &r, dev);
break;
case SIOCGARP:
err = arp_req_get(&r, dev);
break;
}
out:
rtnl_unlock();
if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
err = -EFAULT;
return err;
}

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

switch (event) {
case NETDEV_CHANGEADDR:
neigh_changeaddr(&arp_tbl, dev);
rt_cache_flush(dev_net(dev), 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 __read_mostly = {
.type = cpu_to_be16(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, "ipv4", 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++ = '-';
n = (a->ax25_call[6] >> 1) & 0x0F;
if (n > 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];
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++] = hex_asc_hi(n->ha[j]);
hbuffer[k++] = hex_asc_lo(n->ha[j]);
hbuffer[k++] = ':';
}
if (k != 0)
--k;
hbuffer[k] = 0;
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
}
#endif
sprintf(tbuf, "%pI4", 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, "%pI4", 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_net(inode, 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_net,
};


static int __net_init arp_net_init(struct net *net)
{
if (!proc_net_fops_create(net, "arp", S_IRUGO, &arp_seq_fops))
return -ENOMEM;
return 0;
}

static void __net_exit arp_net_exit(struct net *net)
{
proc_net_remove(net, "arp");
}

static struct pernet_operations arp_net_ops = {
.init = arp_net_init,
.exit = arp_net_exit,
};

static int __init arp_proc_init(void)
{
return register_pernet_subsys(&arp_net_ops);
}

#else /* CONFIG_PROC_FS */

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

#endif /* CONFIG_PROC_FS */
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