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

//----------------------------------------------------------------------------- 
// Net UDP.C 
// 
// This module handles UDP messages 
// Refer to RFC 768, 1122 
// Also RFC 862 echo, RFC 867 daytime, and RFC 868 time 
//----------------------------------------------------------------------------- 
#include  
#include  
#include "C8051f.h" 
#include "net.h" 
#include "ip.h" 
#include "cksum.h" 
#include "serial.h" 
#include "icmp.h" 
#include "udp.h" 
 
extern UCHAR idata debug; 
extern ULONG code my_ipaddr; 
UINT xdata sender_udpport; 
static ULONG xdata sender_ipaddr; 
extern char xdata text[]; 
 
 
//------------------------------------------------------------------------ 
//	UDP Echo service - see RFC 862 
// This simply echos what it received back to the sender 
//------------------------------------------------------------------------ 
void udp_echo_service(UCHAR xdata * inbuf, UINT len) 
{ 
   if (debug) 
   { 
      serial_send("ECHO: Nr chars = "); 
      memset(text, 0, 10); 
      itoa(len, text, 10); 
      serial_send(text); 
	   serial_send("\r"); 
   } 
	udp_send(inbuf, ECHO_PORT, len);       
} 
 
 
 
//------------------------------------------------------------------------ 
//	This handles outgoing UDP messages 
// See "TCP/IP Illustrated, Volume 1" Sect 11.1 - 11.3 
//------------------------------------------------------------------------ 
void udp_send(UCHAR xdata * inbuf, UINT port, UINT len) 
{ 
	ULONG idata sum; 
  	UINT idata result; 
  	UCHAR xdata * outbuf; 
  	UDP_HEADER xdata * udp; 
   IP_HEADER xdata * ip; 
   	 
   // Allocate memory for entire outgoing message including 
   // eth & IP headers. Total ethernet message length is: 
   // 14 byte eth header + 20 byte IP header + 8 byte UDP header 
   // + length of this data  
   outbuf = (UCHAR xdata *)malloc(42 + len); 
   if (outbuf == NULL) 
   { 
      if (debug) serial_send("UDP: Oops, out of memory\r"); 
      return; 
   } 
    
   udp = (UDP_HEADER xdata *)(outbuf + 34); 
   ip = (IP_HEADER xdata *)(outbuf + 14); 
    
   // Direct message back to the senders port.  
	udp->dest_port = sender_udpport; 
	udp->source_port = port; 
	udp->length = 8 + len; 
	udp->checksum = 0; 
		 
	// Fill in data 
   // Important do not free receive buffer prior to this 
   memcpy(&udp->msg_data, (inbuf + 42), len);  
	 
	 
	// Compute checksum including 12 bytes of pseudoheader 
	// Must pre-fill 2 items in outbuf to do this 
	// Direct message back to senders ip address 
	ip->dest_ipaddr = sender_ipaddr; 
	ip->source_ipaddr = my_ipaddr; 
	  
	 
	// Sum source_ipaddr, dest_ipaddr, and entire UDP message  
	sum = (ULONG)cksum(outbuf + 26, 8 + udp->length); 
			 
	// Add in the rest of pseudoheader which is 
	// zero, protocol id, and UDP length 
	sum += (ULONG)0x0011; 
	sum += (ULONG)udp->length; 
 
	// In case there was a carry, add it back around 
	result = (UINT)(sum + (sum >> 16)); 
	udp->checksum = ~result; 
   if (debug) serial_send("UDP: Sending msg to IP layer\r"); 
	ip_send(outbuf, sender_ipaddr, UDP_TYPE, udp->length); 
} 
 
 
 
//------------------------------------------------------------------------ 
// This handles incoming UDP messages 
// See "TCP/IP Illustrated, Volume 1" Sect 11.1 - 11.3 
//------------------------------------------------------------------------ 
void udp_rcve(UCHAR xdata * inbuf, UINT len) 
{ 
   UINT idata result; 
   UDP_HEADER xdata * udp; 
   IP_HEADER xdata * ip; 
   ULONG idata sum; 
       
	// Total of eth & IP headers = 34 bytes       
   udp = (UDP_HEADER xdata *)(inbuf + 34); 
   ip = (IP_HEADER xdata *)(inbuf + 14); 
			 
	// The IP length "len" should be the same as the redundant length 
	// udp->length.  TCP/IP Illustrated, Vol 2, Sect 23.7 says to use the 
	// UDP length, unless IP length < UDP length, in which case the frame 
	// should be discarded. 
   if (len < udp->length) return; 
		    
	// If the checksum is zero it means that the sender did not compute 
	// it and we should not try to check it. 
	if (udp->checksum == 0) 
	{ 
		if (debug) serial_send("UDP: Sender did not compute cksum\r"); 
	} 
	else 
	{ 
		// Compute UDP checksum including 12 byte pseudoheader 
		// Sum source_ipaddr, dest_ipaddr, and entire UDP message  
		sum = (ULONG)cksum(inbuf + 26, 8 + udp->length); 
		 
		// Add in the rest of pseudoheader which is 
		// zero, protocol id, and UDP length 
		sum += (ULONG)0x0011;      
		sum += (ULONG)udp->length; 
 
		// In case there was a carry, add it back around 
		result = (UINT)(sum + (sum >> 16)); 
		 
		if (result != 0xFFFF) 
		{ 
	  		if (debug) serial_send("UDP: Error, bad cksum\r"); 
			return; 
		} 
	 
		if (debug) serial_send("UDP: Msg rcvd with good cksum\r"); 
	} 
		 
	// Capture sender's port number and ip_addr 
	// to send return message to 
	sender_udpport = udp->source_port; 
   sender_ipaddr = ip->source_ipaddr; 
				       
	// See if any applications are on any ports 
	switch (udp->dest_port) 
	{ 
		case ECHO_PORT: 
		// Pass it the payload length 
		udp_echo_service(inbuf, udp->length - 8); 
		break; 
 
		default: 
		// If no application is registered to handle incoming 
		// UDP message then send ICMP destination unreachable 
		dest_unreach_send(inbuf, ip->source_ipaddr); 
		break; 
	} 
}