udp.c

开发工具用EMBEST IDE进行开发,该程序是一个S3C44B0直接驱动网卡的程序,包括8019初始化,物理层收包发包,UDP的接收和发送,IP的发送和接收.已及ARM的地址解板,整个程序是自顶而下

//-----------------------------------------------------------------------------
// 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 "44b.h"
#include "44blib.h"
#include "def.h"
#include "option.h"
#include "ethernet.h"
#include "arp.h"
#include "string.h"
//#include "stdlib.h"
#include "stdio.h"
#include "ip.h"
#include "lib.h"
#include "icmp.h"
#include "udp.h"
extern unsigned char  debug;
extern unsigned long  my_ipaddr;
unsigned short  sender_udpport;
static unsigned long  sender_ipaddr;
//extern char  text[];



//------------------------------------------------------------------------
//	This handles outgoing UDP messages
// See "TCP/IP Illustrated, Volume 1" Sect 11.1 - 11.3
//------------------------------------------------------------------------
void udp_send(unsigned char  * inbuf, unsigned short port, unsigned short len)
{
	unsigned long  sum;
  	unsigned short  result;
  	unsigned char  * outbuf;
  	struct UDP_HEADER  * udp;
    struct IP_HEADER  * 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 
 //  	Uart_Printf("udp_send_fuction\n");
   outbuf = (unsigned char  *)malloc(42 + len);
   if (outbuf == NULL)
   {
   //   if (debug) printf("UDP: Oops, out of memory\n");
      return;
   }
   
   udp = (struct UDP_HEADER  *)(outbuf + 34);
   ip = (struct IP_HEADER  *)(outbuf + 14);
   
   // Direct message back to the senders port. 
	udp->dest_port = ntohs(sender_udpport);
	udp->source_port = ntohs(port);
	udp->length = ntohs(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 =ntohl(sender_ipaddr);
	ip->source_ipaddr =ntohl(my_ipaddr);
	 
	
	// Sum source_ipaddr, dest_ipaddr, and entire UDP message 
	sum = (unsigned long)cksum(outbuf + 26, 8 + ntohs(udp->length));
			
	// Add in the rest of pseudoheader which is
	// zero, protocol id, and UDP length
	sum += (unsigned long)0x0011;
	sum += (unsigned long)ntohs(udp->length);

	// In case there was a carry, add it back around
	result = (unsigned short)(sum + (sum >> 16));
	udp->checksum = ntohs(~result);
   //if (debug) printf("UDP: Sending msg to IP layer\n");
	ip_send(outbuf, sender_ipaddr, UDP_TYPE, ntohs(udp->length));
}

//------------------------------------------------------------------------
//	UDP Echo service - see RFC 862
// This simply echos what it received back to the sender
//------------------------------------------------------------------------
void udp_echo_service(unsigned char * inbuf, unsigned short len)
{
//	Uart_Printf("udp_echo_service\n");
udp_send(inbuf, ECHO_PORT, len);
}


//------------------------------------------------------------------------
// This handles incoming UDP messages
// See "TCP/IP Illustrated, Volume 1" Sect 11.1 - 11.3
//------------------------------------------------------------------------
void udp_rcve(unsigned char  * inbuf, unsigned short len)
{
   unsigned short  result;
   struct UDP_HEADER  * udp;
   struct IP_HEADER  * ip;
   unsigned long  sum;
      
	// Total of eth & IP headers = 34 bytes      
   udp = (struct UDP_HEADER  *)(inbuf + 34);
   ip = (struct IP_HEADER  *)(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 < ntohs(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 (ntohs(udp->checksum) == 0)
	{
		Uart_Printf("UDP: Sender did not compute cksum\n");
	}
	else
	{
		// Compute UDP checksum including 12 byte pseudoheader
		// Sum source_ipaddr, dest_ipaddr, and entire UDP message 
		sum = (unsigned long)cksum(inbuf + 26, 8 + ntohs(udp->length));
		
		// Add in the rest of pseudoheader which is
		// zero, protocol id, and UDP length
		sum += (unsigned long)0x0011;     
		sum += (unsigned long)ntohs(udp->length);

		// In case there was a carry, add it back around
		result = (unsigned short)(sum + (sum >> 16));
		
		if (result != 0xFFFF)
		{
	  		Uart_Printf("UDP: Error, bad cksum\n");
			return;
		}
	
//		 	Uart_Printf("UDP: Msg rcvd with good cksum\n");
	}
		
	// Capture sender's port number and ip_addr
	// to send return message to
	sender_udpport =ntohs(udp->source_port);
//	Uart_Printf("sender_udpport= %x\n",sender_udpport);	
   sender_ipaddr = ntohl(ip->source_ipaddr);
//	Uart_Printf(" sender_ipaddr= %x\n",sender_ipaddr);	
	// See if any applications are on any ports
//Uart_Printf("udp->dest_port= %x\n",ntohs(udp->dest_port));	
	switch (ntohs(udp->dest_port))
	{
		case ECHO_PORT:
		// Pass it the payload length
		udp_echo_service(inbuf, ntohs(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;
	}
}