uip_arp.c

基于STC单片机与MICROCHIP ENC28J60的TCPIP以太网控制器

/**
 * \addtogroup uip
 * @{
 */

/**
 * \defgroup uiparp uIP 
 * @{
 * 
 * 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.
 仅支持以太网*/
 
/**
 * \file
 * Implementation of the ARP Address Resolution Protocol.
 * \author Adam Dunkels <[e-mail]>
 *
 */

/*
 * 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 $
 *
 */

#include "uip_arp.h"
#include "reg51.h"
#include <string.h>

sbit P10 = P1^0;
sbit P11 = P1^1;		   			//add1
sbit P12 = P1^2;					 //add1

struct arp_hdr {
  struct uip_eth_hdr ethhdr;		//头	14字节		
  u16_t hwtype;
  u16_t protocol;
  u8_t hwlen;
  u8_t protolen;
  u16_t opcode;
  struct uip_eth_addr shwaddr;		//地址
  u16_t sipaddr[2];
  struct uip_eth_addr dhwaddr;
  u16_t dipaddr[2];			//42字节 
};
		
struct ethip_hdr {
  struct uip_eth_hdr ethhdr;		//14字节
  /* IP header. */
  u8_t vhl,
    tos,          
    len[2],       
    ipid[2],        
    ipoffset[2],  
    ttl,          
    proto;     
  u16_t ipchksum;
  u16_t srcipaddr[2], 
    destipaddr[2];		//20字节
};					

#define ARP_REQUEST 1
#define ARP_REPLY   2

#define ARP_HWTYPE_ETH 1			//硬件类型1代表MAC地址

struct arp_entry {
  u16_t ipaddr[2];
  struct uip_eth_addr ethaddr;
  u8_t time;
};

struct uip_eth_addr xdata uip_ethaddr = {{UIP_ETHADDR0,
				    UIP_ETHADDR1,
				    UIP_ETHADDR2,
				    UIP_ETHADDR3,
				    UIP_ETHADDR4,
				    UIP_ETHADDR5}};

static struct arp_entry xdata arp_table[UIP_ARPTAB_SIZE];			//UIP_ARPTAB_SIZE=2
static u16_t xdata ipaddr[2];
static u8_t xdata i, c;

static u8_t xdata arptime;
static u8_t xdata 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) {			//UIP_ARPTAB_SIZE=5
    memset(arp_table[i].ipaddr, 0, 4);			//清0
  }
}
/*-----------------------------------------------------------------------------------*/
/**
 * Periodic ARP processing function.
 *周期性ARP处理函数
 * 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.
 *建议10s钟进行一次查询		arptime+1时间为10s
 */
/*-----------------------------------------------------------------------------------*/
void
uip_arp_timer(void)
{
  struct arp_entry *tabptr;
  
  ++arptime;								//静态变量
  for(i = 0; i < UIP_ARPTAB_SIZE; ++i) {					//清0	
    tabptr = &arp_table[i];
    if((tabptr->ipaddr[0] | tabptr->ipaddr[1]) != 0 &&
       arptime - tabptr->time >= UIP_ARP_MAXAGE) {				//UIP_ARP_MAXAGE=120,代表20分钟
      memset(tabptr->ipaddr, 0, 4);			//该字符串函数的意义, 可能是清零
    }
  }

}
/*-----------------------------------------------------------------------------------*/
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 入口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);		//赋值
	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.现在i是ARP表格的入口 */
  memcpy(tabptr->ipaddr, ipaddr, 4);
  memcpy(tabptr->ethaddr.addr, ethaddr->addr, 6);
  tabptr->time = arptime;
}
/*-----------------------------------------------------------------------------------*/
/**
 * ARP processing for incoming IP packets
 *	ARP处理进入的IP包
 * 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.
 *当接收到一个IP包的时候，这个函数奖被设备驱动调用，这个函数将核实该地址是不是ARP缓寸中的IP地址
如果是的话，ARP 缓存将被更新，如果不是的话，将创立一个新的。
 * 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.
 */														//  驱动函数应该解决的问题
/*-----------------------------------------------------------------------------------*/
void
uip_arp_ipin(void)
{
  uip_len -= sizeof(struct uip_eth_hdr);			//14个字节
						
  /* 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]) !=			//需要接收的ARP/IP包
     (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));
  
  P12=~P12;							//add1

  return;
}
/*-----------------------------------------------------------------------------------*/
/**
 * ARP processing for incoming ARP packets.
 *收到的ARP包
 * 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.
 *接收到ARP包的时候调用这个函数，对几种不的ARP包进行不同的处理，
如果是我发的请求的一个回复，我们将更新我们的ARP表格，如果是要求我们自己的IP地址
一个ARP回复包将创立，然后发送出去。
 * 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.
 *当这个函数返回时候，全局变量uiplen隐含了是否要发送一个包。
 * 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.
 */												//  驱动函数应该解决的问题
/*-----------------------------------------------------------------------------------*/
void
uip_arp_arpin(void)
{

  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] &&			//IP确定是要求主机发送请求的
       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);		//主要在于发送这个地址给对方
      memcpy(BUF->ethhdr.src.addr, uip_ethaddr.addr, 6);	//主要在于发送这个地址给对方
      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];

      BUF->ethhdr.type = HTONS(UIP_ETHTYPE_ARP);      
      uip_len = sizeof(struct arp_hdr);				//设置发送包的长度为结构体的长度
    }      
    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] &&			//确定是我要接收的数据包
       BUF->dipaddr[1] == uip_hostaddr[1]) {

      uip_arp_update(BUF->sipaddr, &BUF->shwaddr);			//更新到ARP列表中

    }
    break;
  }

  return;
}
/*-----------------------------------------------------------------------------------*/
/**
 * Prepend Ethernet header to an outbound IP packet and see if we need
 * to send out an ARP request.
 *我准备发送一个数据包出去，但确定我要发送一个ARP请求包
 * 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.
 *要发送的目的地址的MAC地址不知道，而发送一个ARP请求的包
 * 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.
 *如果ARP缓存中有目的的IP和子网地址，则不要在发送请求ARP包，如果没有，则暂时要
发送的IP包将被ARP包所覆盖，要TCP重新传送这个包。
 * If the destination IP address is not on the local network, the IP
 * address of the default router is used instead.
 *如果目的的IP地址没有在本地网络中，则默认路由器的地址将取代它。
 * 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.这个是判断即将要发送的数据包 */
  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];				//UIP.C的开始设置
  } 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++) {  		//改++i ->\i++
   		 tabptr = &arp_table[i];
    if(ipaddr[0] == tabptr->ipaddr[0] &&
       ipaddr[1] == tabptr->ipaddr[1])
      break;
  }

  if(i == UIP_ARPTAB_SIZE-1) {						//运行完没发现所要IP地址  改
    /* The destination address was not in our ARP table, so we
       overwrite the IP packet with an ARP request. */
	//发送ARP包
    memset(BUF->ethhdr.dest.addr, 0xff, 6);			// 广播包发送
    memset(BUF->dhwaddr.addr, 0x00, 6);				//随意
    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);				//HW 硬件
    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];			//要改
    
    uip_len = sizeof(struct arp_hdr);
    return;
  }
  /* Build an ethernet header. 在缓存中IP找到了，作为IP包发送出去*/
  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);			//意思是我开始写的以太网头后面的数据
}
/*-----------------------------------------------------------------------------------*/

/** @} */
/** @} */