www.pudn.com > zhiyonglou311.rar > Icmp.c

//----------------------------------------------------------------------------- 
// Net ICMP.C 
// 
// This module handles ICMP messages 
// Refer to RFC 792, 896, 950, 1122, and 1191 
//----------------------------------------------------------------------------- 
#include  
#include  
#include "C8051f.h" 
#include "net.h" 
#include "cksum.h" 
#include "ip.h" 
#include "serial.h" 
#include "icmp.h" 
 
extern UCHAR idata debug; 
 
 
//------------------------------------------------------------------------ 
// This builds a ping response message.  It allocates memory for the 
// entire outgoing message, including Eth and IP headers.  See "TCP/IP 
// Illustrated, Volume 1" Sect 7.2 for info on Ping messages 
//------------------------------------------------------------------------ 
void ping_send(UCHAR xdata * inbuf, ULONG ipaddr, UINT len) 
{ 
   PING_HEADER xdata * ping_in; 
   PING_HEADER xdata * ping_out; 
   UCHAR xdata * outbuf; 
             
   ping_in = (PING_HEADER xdata *)(inbuf + 34); 
       
   // Allocate memory for entire outgoing message 
   outbuf = (UCHAR xdata *)malloc(len + 34); 
   if (outbuf == NULL) 
   { 
      if (debug) serial_send("PING: Oops, out of memory\r"); 
      return; 
   }       
       
   // Ping response message payload starts at offset 34 
   ping_out = (PING_HEADER xdata *)(outbuf + 34); 
 
   ping_out->msg_type = 0; 
   ping_out->msg_code = 0; 
   ping_out->checksum = 0; 
   ping_out->identifier = ping_in->identifier; 
   ping_out->sequence = ping_in->sequence; 
    
   memcpy(&ping_out->echo_data, &ping_in->echo_data, len - 8); 
             
   // Compute checksum over the ICMP header plus 
	// optional data and insert complement 
   ping_out->checksum = ~cksum(outbuf + 34, len); 
                         
   if (debug) serial_send("ICMP: Sending response to IP layer\r"); 
 
   ip_send(outbuf, ipaddr, ICMP_TYPE, len); 
} 
 
 
 
//------------------------------------------------------------------------ 
// This builds an outgoing ICMP destination port unreachable response 
// message.  See See "TCP/IP Illustrated, Volume 1" Sect 6.5.  This 
// message is typically sent in response to a UDP message directed 
// to a port that has no corresponding application running.  
// Todo: The spec says we should return all options that were in 
// the original incoming IP header.  Right now we cut off everything 
// after the first 20 bytes.  
//------------------------------------------------------------------------ 
void dest_unreach_send(UCHAR xdata * inbuf, ULONG ipaddr) 
{ 
   UCHAR xdata * outbuf; 
   ICMP_ERR_HEADER xdata * icmp; 
             
   // Allocate memory for entire outgoing message 
   // including eth and IP haders.  Always 70 bytes 
   outbuf = (UCHAR xdata *)malloc(70); 
   if (outbuf == NULL) 
   { 
      if (debug) serial_send("ICMP: Oops, out of memory\r"); 
      return; 
   }       
       
   icmp = (ICMP_ERR_HEADER xdata *)(outbuf + 34); 
    
   // Fill in ICMP error message header 
   icmp->msg_type = 3;   // destination unreachable 
   icmp->msg_code = 3;   // port unreachable 
   icmp->checksum = 0; 
       
   // Fill in ICMP error message data 
   icmp->msg_data = 0; 
            
   // Copy in 20 byte original incoming IP header 
   // plus 8 bytes of data 
   memcpy(&icmp->echo_data, inbuf + 14, 28); 
                                
   // Compute checksum over the 36 byte long ICMP 
   // header plus data and insert complement 
   icmp->checksum = ~cksum(outbuf + 34, 36); 
       
   // Forward message to the IP layer 
   if (debug) serial_send("ICMP: Sending dest unreach to IP layer\r"); 
   ip_send(outbuf, ipaddr, ICMP_TYPE, 36); 
} 
 
 
 
 
//------------------------------------------------------------------------ 
// This handles incoming ICMP messages.  See "TCP/IP Illustrated, 
// Volume 1" Sect 6.2 for discussion of the various ICMP messages 
//------------------------------------------------------------------------ 
void icmp_rcve(UCHAR xdata * inbuf, UINT len) 
{ 
   IP_HEADER * ip; 
   UCHAR idata msg_type; 
   UINT idata temp; 
    
   // Allow for 14 bytes eth header 
   ip = (IP_HEADER *)(inbuf + 14); 
         
   // IP header has been adjusted if necessary to always be  
	// 20 bytes so message starts at an offset of 34 
   // Validate checksum of entire ICMP message incl data  
	temp = cksum(inbuf + 34, len); 
	 
	if (temp != 0xFFFF) 
	{ 
	  	if (debug) serial_send("ICMP: Error, cksum bad\r"); 
      return;  
   } 
       
   // Switch on the message type 
   msg_type = *(inbuf + 34); 
   switch(msg_type) 
   { 
      case 3: 
      if (debug) serial_send("ICMP: Dest unreachable rcvd\r"); 
      break; 
 
	   case 8: 
      if (debug) serial_send("ICMP: Ping rcvd\r"); 
      ping_send(inbuf, ip->source_ipaddr, len);  
      break; 
 
      default: 
      if (debug) serial_send("ICMP: Error, unknown msg rcvd\r"); 
      break; 
   } 
}