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/** |
* \addtogroup uip |
* @{ |
*/ |
|
/** |
* \defgroup uiparp uIP Address Resolution Protocol |
* @{ |
* |
* The Address Resolution Protocol ARP is used for mapping between IP |
* addresses and link level addresses such as the Ethernet MAC |
* addresses. ARP uses broadcast queries to ask for the link level |
* address of a known IP address and the host which is configured with |
* the IP address for which the query was meant, will respond with its |
* link level address. |
* |
* \note This ARP implementation only supports Ethernet. |
*/ |
|
/** |
* \file |
* Implementation of the ARP Address Resolution Protocol. |
* \author Adam Dunkels <adam@dunkels.com> |
* |
*/ |
|
/* |
* Copyright (c) 2001-2003, Adam Dunkels. |
* All rights reserved. |
* |
* Redistribution and use in source and binary forms, with or without |
* modification, are permitted provided that the following conditions |
* are met: |
* 1. Redistributions of source code must retain the above copyright |
* notice, this list of conditions and the following disclaimer. |
* 2. Redistributions in binary form must reproduce the above copyright |
* notice, this list of conditions and the following disclaimer in the |
* documentation and/or other materials provided with the distribution. |
* 3. The name of the author may not be used to endorse or promote |
* products derived from this software without specific prior |
* written permission. |
* |
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS |
* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY |
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE |
* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
* |
* This file is part of the uIP TCP/IP stack. |
* |
* $Id: uip_arp.c,v 1.7.2.3 2003/10/06 22:42:30 adam Exp $ |
* |
*/ |
|
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#include "uip_arp.h" |
|
#include <string.h> |
|
struct arp_hdr { |
struct uip_eth_hdr ethhdr; |
u16_t hwtype; |
u16_t protocol; |
u8_t hwlen; |
u8_t protolen; |
u16_t opcode; |
struct uip_eth_addr shwaddr; |
u16_t sipaddr[2]; |
struct uip_eth_addr dhwaddr; |
u16_t dipaddr[2]; |
}; |
|
struct ethip_hdr { |
struct uip_eth_hdr ethhdr; |
/* IP header. */ |
u8_t vhl, |
tos, |
len[2], |
ipid[2], |
ipoffset[2], |
ttl, |
proto; |
u16_t ipchksum; |
u16_t srcipaddr[2], |
destipaddr[2]; |
}; |
|
#define ARP_REQUEST 1 |
#define ARP_REPLY 2 |
|
#define ARP_HWTYPE_ETH 1 |
|
struct arp_entry { |
u16_t ipaddr[2]; |
struct uip_eth_addr ethaddr; |
u8_t time; |
}; |
|
struct uip_eth_addr uip_ethaddr = {{UIP_ETHADDR0, |
UIP_ETHADDR1, |
UIP_ETHADDR2, |
UIP_ETHADDR3, |
UIP_ETHADDR4, |
UIP_ETHADDR5}}; |
|
static struct arp_entry arp_table[UIP_ARPTAB_SIZE]; |
static u16_t ipaddr[2]; |
static u8_t i, c; |
|
static u8_t arptime; |
static u8_t tmpage; |
|
#define BUF ((struct arp_hdr *)&uip_buf[0]) |
#define IPBUF ((struct ethip_hdr *)&uip_buf[0]) |
/*-----------------------------------------------------------------------------------*/ |
/** |
* Initialize the ARP module. |
* |
*/ |
/*-----------------------------------------------------------------------------------*/ |
void |
uip_arp_init(void) |
{ |
for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { |
memset(arp_table[i].ipaddr, 0, 4); |
} |
} |
/*-----------------------------------------------------------------------------------*/ |
/** |
* Periodic ARP processing function. |
* |
* This function performs periodic timer processing in the ARP module |
* and should be called at regular intervals. The recommended interval |
* is 10 seconds between the calls. |
* |
*/ |
/*-----------------------------------------------------------------------------------*/ |
void |
uip_arp_timer(void) |
{ |
struct arp_entry *tabptr; |
|
++arptime; |
for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { |
tabptr = &arp_table[i]; |
if((tabptr->ipaddr[0] | tabptr->ipaddr[1]) != 0 && |
arptime - tabptr->time >= UIP_ARP_MAXAGE) { |
memset(tabptr->ipaddr, 0, 4); |
} |
} |
|
} |
/*-----------------------------------------------------------------------------------*/ |
static void |
uip_arp_update(u16_t *ipaddr, struct uip_eth_addr *ethaddr) |
{ |
register struct arp_entry *tabptr; |
/* Walk through the ARP mapping table and try to find an entry to |
update. If none is found, the IP -> MAC address mapping is |
inserted in the ARP table. */ |
for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { |
|
tabptr = &arp_table[i]; |
/* Only check those entries that are actually in use. */ |
if(tabptr->ipaddr[0] != 0 && |
tabptr->ipaddr[1] != 0) { |
|
/* Check if the source IP address of the incoming packet matches |
the IP address in this ARP table entry. */ |
if(ipaddr[0] == tabptr->ipaddr[0] && |
ipaddr[1] == tabptr->ipaddr[1]) { |
|
/* An old entry found, update this and return. */ |
memcpy(tabptr->ethaddr.addr, ethaddr->addr, 6); |
tabptr->time = arptime; |
|
return; |
} |
} |
} |
|
/* If we get here, no existing ARP table entry was found, so we |
create one. */ |
|
/* First, we try to find an unused entry in the ARP table. */ |
for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { |
tabptr = &arp_table[i]; |
if(tabptr->ipaddr[0] == 0 && |
tabptr->ipaddr[1] == 0) { |
break; |
} |
} |
|
/* If no unused entry is found, we try to find the oldest entry and |
throw it away. */ |
if(i == UIP_ARPTAB_SIZE) { |
tmpage = 0; |
c = 0; |
for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { |
tabptr = &arp_table[i]; |
if(arptime - tabptr->time > tmpage) { |
tmpage = arptime - tabptr->time; |
c = i; |
} |
} |
i = c; |
} |
|
/* Now, i is the ARP table entry which we will fill with the new |
information. */ |
memcpy(tabptr->ipaddr, ipaddr, 4); |
memcpy(tabptr->ethaddr.addr, ethaddr->addr, 6); |
tabptr->time = arptime; |
} |
/*-----------------------------------------------------------------------------------*/ |
/** |
* ARP processing for incoming IP packets |
* |
* This function should be called by the device driver when an IP |
* packet has been received. The function will check if the address is |
* in the ARP cache, and if so the ARP cache entry will be |
* refreshed. If no ARP cache entry was found, a new one is created. |
* |
* This function expects an IP packet with a prepended Ethernet header |
* in the uip_buf[] buffer, and the length of the packet in the global |
* variable uip_len. |
*/ |
/*-----------------------------------------------------------------------------------*/ |
void |
uip_arp_ipin(void) |
{ |
uip_len -= sizeof(struct uip_eth_hdr); |
|
/* Only insert/update an entry if the source IP address of the |
incoming IP packet comes from a host on the local network. */ |
if((IPBUF->srcipaddr[0] & uip_arp_netmask[0]) != |
(uip_hostaddr[0] & uip_arp_netmask[0])) { |
return; |
} |
if((IPBUF->srcipaddr[1] & uip_arp_netmask[1]) != |
(uip_hostaddr[1] & uip_arp_netmask[1])) { |
return; |
} |
uip_arp_update(IPBUF->srcipaddr, &(IPBUF->ethhdr.src)); |
|
return; |
} |
/*-----------------------------------------------------------------------------------*/ |
/** |
* ARP processing for incoming ARP packets. |
* |
* This function should be called by the device driver when an ARP |
* packet has been received. The function will act differently |
* depending on the ARP packet type: if it is a reply for a request |
* that we previously sent out, the ARP cache will be filled in with |
* the values from the ARP reply. If the incoming ARP packet is an ARP |
* request for our IP address, an ARP reply packet is created and put |
* into the uip_buf[] buffer. |
* |
* When the function returns, the value of the global variable uip_len |
* indicates whether the device driver should send out a packet or |
* not. If uip_len is zero, no packet should be sent. If uip_len is |
* non-zero, it contains the length of the outbound packet that is |
* present in the uip_buf[] buffer. |
* |
* This function expects an ARP packet with a prepended Ethernet |
* header in the uip_buf[] buffer, and the length of the packet in the |
* global variable uip_len. |
*/ |
/*-----------------------------------------------------------------------------------*/ |
typedef struct arp_hdr aht; |
|
void |
uip_arp_arpin(void) |
{ |
int ul; |
|
if(uip_len < sizeof(struct arp_hdr)) { |
uip_len = 0; |
return; |
} |
|
uip_len = 0; |
|
switch(BUF->opcode) { |
case HTONS(ARP_REQUEST): |
/* ARP request. If it asked for our address, we send out a |
reply. */ |
if(BUF->dipaddr[0] == uip_hostaddr[0] && |
BUF->dipaddr[1] == uip_hostaddr[1]) { |
/* The reply opcode is 2. */ |
BUF->opcode = HTONS(2); |
|
memcpy(BUF->dhwaddr.addr, BUF->shwaddr.addr, 6); |
memcpy(BUF->shwaddr.addr, uip_ethaddr.addr, 6); |
memcpy(BUF->ethhdr.src.addr, uip_ethaddr.addr, 6); |
memcpy(BUF->ethhdr.dest.addr, BUF->dhwaddr.addr, 6); |
|
BUF->dipaddr[0] = BUF->sipaddr[0]; |
BUF->dipaddr[1] = BUF->sipaddr[1]; |
BUF->sipaddr[0] = uip_hostaddr[0]; |
BUF->sipaddr[1] = uip_hostaddr[1]; |
|
ul = BUF->hwlen; |
BUF->ethhdr.type = HTONS(UIP_ETHTYPE_ARP); |
uip_len = sizeof(struct arp_hdr); |
} |
break; |
case HTONS(ARP_REPLY): |
/* ARP reply. We insert or update the ARP table if it was meant |
for us. */ |
if(BUF->dipaddr[0] == uip_hostaddr[0] && |
BUF->dipaddr[1] == uip_hostaddr[1]) { |
|
uip_arp_update(BUF->sipaddr, &BUF->shwaddr); |
} |
break; |
} |
|
( void ) ul; |
|
return; |
} |
/*-----------------------------------------------------------------------------------*/ |
/** |
* Prepend Ethernet header to an outbound IP packet and see if we need |
* to send out an ARP request. |
* |
* This function should be called before sending out an IP packet. The |
* function checks the destination IP address of the IP packet to see |
* what Ethernet MAC address that should be used as a destination MAC |
* address on the Ethernet. |
* |
* If the destination IP address is in the local network (determined |
* by logical ANDing of netmask and our IP address), the function |
* checks the ARP cache to see if an entry for the destination IP |
* address is found. If so, an Ethernet header is prepended and the |
* function returns. If no ARP cache entry is found for the |
* destination IP address, the packet in the uip_buf[] is replaced by |
* an ARP request packet for the IP address. The IP packet is dropped |
* and it is assumed that they higher level protocols (e.g., TCP) |
* eventually will retransmit the dropped packet. |
* |
* If the destination IP address is not on the local network, the IP |
* address of the default router is used instead. |
* |
* When the function returns, a packet is present in the uip_buf[] |
* buffer, and the length of the packet is in the global variable |
* uip_len. |
*/ |
/*-----------------------------------------------------------------------------------*/ |
void |
uip_arp_out(void) |
{ |
struct arp_entry *tabptr; |
/* Find the destination IP address in the ARP table and construct |
the Ethernet header. If the destination IP addres isn't on the |
local network, we use the default router's IP address instead. |
|
If not ARP table entry is found, we overwrite the original IP |
packet with an ARP request for the IP address. */ |
|
/* Check if the destination address is on the local network. */ |
if((IPBUF->destipaddr[0] & uip_arp_netmask[0]) != |
(uip_hostaddr[0] & uip_arp_netmask[0]) || |
(IPBUF->destipaddr[1] & uip_arp_netmask[1]) != |
(uip_hostaddr[1] & uip_arp_netmask[1])) { |
/* Destination address was not on the local network, so we need to |
use the default router's IP address instead of the destination |
address when determining the MAC address. */ |
ipaddr[0] = uip_arp_draddr[0]; |
ipaddr[1] = uip_arp_draddr[1]; |
} else { |
/* Else, we use the destination IP address. */ |
ipaddr[0] = IPBUF->destipaddr[0]; |
ipaddr[1] = IPBUF->destipaddr[1]; |
} |
|
for(i = 0; i < UIP_ARPTAB_SIZE; ++i) { |
tabptr = &arp_table[i]; |
if(ipaddr[0] == tabptr->ipaddr[0] && |
ipaddr[1] == tabptr->ipaddr[1]) |
break; |
} |
|
if(i == UIP_ARPTAB_SIZE) { |
/* The destination address was not in our ARP table, so we |
overwrite the IP packet with an ARP request. */ |
|
memset(BUF->ethhdr.dest.addr, 0xff, 6); |
memset(BUF->dhwaddr.addr, 0x00, 6); |
memcpy(BUF->ethhdr.src.addr, uip_ethaddr.addr, 6); |
memcpy(BUF->shwaddr.addr, uip_ethaddr.addr, 6); |
|
BUF->dipaddr[0] = ipaddr[0]; |
BUF->dipaddr[1] = ipaddr[1]; |
BUF->sipaddr[0] = uip_hostaddr[0]; |
BUF->sipaddr[1] = uip_hostaddr[1]; |
BUF->opcode = HTONS(ARP_REQUEST); /* ARP request. */ |
BUF->hwtype = HTONS(ARP_HWTYPE_ETH); |
BUF->protocol = HTONS(UIP_ETHTYPE_IP); |
BUF->hwlen = 6; |
BUF->protolen = 4; |
BUF->ethhdr.type = HTONS(UIP_ETHTYPE_ARP); |
|
uip_appdata = &uip_buf[40 + UIP_LLH_LEN]; |
|
uip_len = sizeof(struct arp_hdr); |
return; |
} |
|
/* Build an ethernet header. */ |
memcpy(IPBUF->ethhdr.dest.addr, tabptr->ethaddr.addr, 6); |
memcpy(IPBUF->ethhdr.src.addr, uip_ethaddr.addr, 6); |
|
IPBUF->ethhdr.type = HTONS(UIP_ETHTYPE_IP); |
|
uip_len += sizeof(struct uip_eth_hdr); |
} |
/*-----------------------------------------------------------------------------------*/ |
|
/** @} */ |
/** @} */ |