arp.c

完整的TCP/IP源代码,绝对好用

*   INPUTS                                                                
*                                                                         
*                     
*       *ip_dest  - Pointer to the IP destination.            
*       *mac_dest - Pointer to the hardware address.  
*                   This will be filled in if found.     
*       *buf_ptr  - Pointer to a buffer containing an IP packet.  
*         buf_len - the ip packet's length                                                                  
*   OUTPUTS                                                               
*                                                                         
*       1          - Indicates successful operation.           
*       0  - Indicates the address is unresolved.  
*                             The IP is queued pending resolution.      
*
*************************************************************************/
UINT8 ARP_Resolve(UINT8*ip_dest, 
                   UINT8 *mac_dest, UINT8 *buf_ptr,UINT16 buf_len)
{
 
    UINT16      timer;
    UINT8       found;
	UINT8       i;
	UINT8  *ip_ptr;

	//如果目的IP地址是一个子网内部的则继续向下，否则，将IP地址修改为GATEWAY的IP，继续向下，
	//这样做的目的是为了转发数据报
	ip_ptr = ip_dest;
	i = *ip_dest;
    i &= 0xe0; 
	if ((i & 0xe0) == 0xe0) //d类 28位多播组号
	{
     

	}
	else if((i & 0xc0) == 0xc0) //c 类21位网络号8位主机号
	{
	  for(i=0;i<4;i++)
	  {
         if((MY_IP[i] & NET_MASK[i]) != (*(ip_dest+i) &NET_MASK[i])) 
		 {
		    ip_ptr = &GATEWAY[0]; //查网关的IP地址
		    break;
		 }
	  }
	}

	else if((i & 0x80) == 0x80) // B类14位网络号16位主机号
	{
	  for(i=0;i<4;i++)
	  {
         if ((MY_IP[i] & NET_MASK[i]) != (*(ip_dest+i) &NET_MASK[i])) 
		 {
		    ip_ptr = GATEWAY; //查网关的IP地址
		    break;
		 }
	  }
	}
	else 					//A类7位网络号24位主机号
	{
	  for(i=0;i<4;i++)
	  {
         if ((MY_IP[i] & NET_MASK[i]) != (*(ip_dest+i) &NET_MASK[i])) 
		 {
		    ip_ptr = GATEWAY; //查网关的IP地址
		    break;
		 }
	  }
	}




    /* If this is a broadcast packet then simply return the ethernet broadcast 
       address. */
/*
   if(memcmp(ip_dest, NET_BCAST,4) == 0)
    	{
    	memcp(mac_dest,NET_Ether_Broadaddr,6);
       return 1;
    	}
*/   
    
    /* Check the ARP cache for the destination.  If found, return. */
	found = ARP_Find_Entry(ip_ptr);
    if ( found != 0xff)
    {   
       memcp(mac_dest, ARP_Cache[found].arp_mac_addr, DADDLEN);
        return (1);
    }
    ARP_Request(ip_ptr,NET_Ether_Broadaddr);  //broadcast the IP addr.
    // if not found, save it to the Wait_IP_buffer
    for(i=0;i<wait_buffer_num;i++)
    	{
    	if(Wait_IP_buffer[i].flag == 0)
    		{
    		memcp(Wait_IP_buffer[i].send_packet,buf_ptr,buf_len);
  		    memcp(Wait_IP_buffer[i].tipnum,ip_ptr,4);

    		Wait_IP_buffer[i].flag = 1;
		    Wait_IP_buffer[i].send_packet_len = buf_len;
    		Wait_IP_buffer[i].time = 0xffff;
    		return (0);
    		}
    	}

    // the oldest is discarded.
    timer = Wait_IP_buffer[0].time;
    for (i=1;i<wait_buffer_num;i++)
    	{
    	if (Wait_IP_buffer[i].time < timer)
    		{
    		timer = Wait_IP_buffer[i].time;
    		found = i;
    		}
    	}

    memcp (Wait_IP_buffer[found].send_packet,buf_ptr,buf_len);
    	
    return(0);
}  /* end ARP_Resolve */

/*************************************************************************
*
*   FUNCTION                                                              
*                                                                         
*       ARP_Find_Entry                                                    
*                                                                         
*   DESCRIPTION                                                           
*                                                                         
*       This function searches the ARP cache for a matching entry.        
*                                                                         
*   INPUTS                                                                
*                                                                         
*       *dest - IP address for which an ethernet address is desired.                               
*                                                                         
*   OUTPUTS                                                               
*                                                                         
*       *ARP_ENTRY - A pointer to an entry in the ARP cache. 
*        NU_NULL   - If failure.                                  
*
*************************************************************************/
UINT8 ARP_Find_Entry( UINT8* destip)
{
    UINT8   i;
    char j;
    /* Search the cache for the target IP number. */

    for (i = 0; i < ARP_CACHE_LENGTH; i++)
    {
		j = memcmp(destip,ARP_Cache[i].arp_ip_addr,4);
        if ( j == 0)
        {
            // We found the entry. 
            //a_entry = &ARP_Cache[i];
            if(ARP_Cache[i] .arp_time !=0)
            	{
            	return(i);
            	}
        }
    }
        return (0xff);

} /* ARP_Find_Entry */

/*************************************************************************
*
*   FUNCTION                                                              
*                                                                         
*       ARP_Request                                                       
*                                                                         
*   DESCRIPTION                                                           
*                                                                         
*       Send an ARP request.                                              
*                                                                         
*   INPUTS                                                                
*                                                                         
*       *tip          - The target IP number                          
*       *thardware    - The target hardware address.                  
*                                                                         
*   OUTPUTS                                                               
*                                                                         
*       NU_SUCCESS  - If success.                                   
*       -1          - If error.                                     
*                                                                         
*************************************************************************/
void  ARP_Request(UINT8 *tip, UINT8 *thardware)
{
    ARP_LAYER    arp_packet;

    ARP_Build_Pkt(tip, &arp_packet,thardware, MY_IP, ARPREQ);//RARPQ);modified bu yugz
    Ether_output(thardware,sizeof(arp_packet),(UINT8 *)&arp_packet,EARP);
    return ;

} /* ARP_Request */

/*************************************************************************
*                                                                       
*   FUNCTION                                                              
*                                                                       
*       ARP_Cache_Update                                                 
*                                                                       
*   DESCRIPTION                                                           
*                                                                       
*       Add an entry to the ARP cache.                                   
*                                                                       
*   INPUTS                                                                
*                                                                       
*       *ipn    - The IP address                                                   
*       *hrdn  - The pointer to the hardware address                                                  
*       flags  - The arp flags 
*                                                                       
*   OUTPUTS                                                               
*                                                                       
*       INT    - Index of entry made in ARP cache.        
*       -1     - Entry was not found.                     
*                                                                       
*************************************************************************/
INT16 ARP_Cache_Update(UINT8 *ipn, UINT8 *hrdn, UINT8 flags)
{
    INT16   i, found = -1 ;
    UINT32  timer;
    UINT8 j;
    for (i=0; i < ARP_CACHE_LENGTH; i++)
	{
	 j = memcmp(ipn, ARP_Cache[i].arp_ip_addr,4) ;
        if (j == 0)
        {
            found = i;
            break;
        }
	}
    /*
     *  if that IP number is not already here, take the oldest
     *  entry.
     *  If it is already here, update the info and reset the timer.
     *  These were pre-initialized to 0, so if any are blank, they
     *  will be
     *  taken first because they are faked to be oldest.
     */
    if (found<0)
    {
        found = 0;
        timer = ARP_Cache[found].arp_time;

        for (i=1; i < ARP_CACHE_LENGTH; i++)
        {
            if ( (ARP_Cache[i].arp_time <  timer) &&
                ( (ARP_Cache[i].arp_flags & ARP_PERMANENT) == 0) )
            {  
                found = i;
                timer = ARP_Cache[i].arp_time;
            }  
        } 
    }  

    /*
     *   do the update to the cache
     */
    memcp (ARP_Cache[found].arp_mac_addr, hrdn, DADDLEN);
    memcp (ARP_Cache[found].arp_ip_addr,ipn,4);

    
    ARP_Cache[found].arp_time = 2000; //time_20min; // here is the 20 * tick/min 
    ARP_Cache[found].arp_flags = (ARP_UP | flags);
    return (found);
}