ip.c

基于51的单片机的PPP协议实现

/*/////////////////////////////////////////////////////////////////////////////

File Name : IP.C

Author : Rene Trenado

Location : Motorola Applications Lab, Baja California

Date Created : September 2000

Current Revision : 0.0

Notes : This file contains the Internet Protocol variables & support routines

/////////////////////////////////////////////////////////////////////////////*/
#include "IP.h"
#include "PPP.h"
#include "SLIP.h"

extern BYTE	InBuffer [PPP_BUFFER_SIZE + 1];	/// Input Buffer for PPP data
extern BYTE	OutBuffer[PPP_BUFFER_SIZE + 1];	

BYTE IPAddress[4] = {220, 1, 141, 149};					/* Default IP Address */
static volatile char IPAdapter = PPP;					/* Default interface for IP output */
IPDatagram *ip_in;
IPDatagram *ip_out;								/* Global buffer for IP packet output */




/***********************************************************************
Function : 	IPInit

Parameters : 	None

Date : 		September 2000

Desc : 		Initializes the IP module pointers

***********************************************************************/
void IPInit (void) {
	ip_in = (IPDatagram *)&InBuffer [4];
	ip_out = (IPDatagram *)&OutBuffer [4];
}



/***********************************************************************
Function : 	Bind adapter

Parameters : 	Interface: A Byte ID

Date : 		September 2000

Desc : 		Selects the output format of an IP packet

***********************************************************************/
void IPBindAdapter (INTERFACE Interface) {
	IPAdapter = Interface;							/* switch to different output interface */
}


/***********************************************************************
Function : 	IPNetSend

Parameters : 	ip: A pointer to a IP datagram to transmit

Date : 		November 2000

Desc : 		Sends a IP datagram over the interface specified

***********************************************************************/
void IPNetSend (IPDatagram* ip) {
static WORD Id = 0xF0;								/* ID to be used in IP datagrams */

	ip_out->Version_HLen	= 0x45;					/* Header Forma=IPv4, Length = 5 DWORDs */
	ip_out->Service 	= 0;							/* Always zero */
	ip_out->LengthUpper 	= 0;						/* High byte of datagram Length */
	ip_out->ID 		= htons(Id++);					/* Merge IP ID */
	ip_out->Frag 		= 0;						/* No flags nor enable fragmentation */
	ip_out->TTL 		= 0x80;					/* Time to live set to default */
	ip_out->Checksum 	= 0;							/* Clear checksum to avoid miscalculations */
	ip_out->Checksum 	= htons(IPCheckSum ((BYTE *)ip_out, 10));	/* Get checksum of entire datagram */

	switch (IPAdapter) {							/* Select the adapter to output the IP datagram */
		case PPP:								/* Output through PPP adapter */
			OutBuffer [0] = 0xff;					/* Frame PPP packet */
			OutBuffer [1] = 0x03;
			OutBuffer [2] = 0x00;					/* This is a IP datagram, set protocol type */
			OutBuffer [3] = 0x21;
      			ProcPPPSend (OutBuffer, OutBuffer [7] + 6);
		break;

		case SLIP:
			ProcSLIPSend ((BYTE *)ip_out, ip_out->Length);	/* Output through SLIP interface */
		break;


		case ETHERNET:							/* Send datagram over ethernet */
		break;

		default:
		break;
	}
}


/***********************************************************************
Function : 	IPCompare

Parameters : 	Ip: A pointer to a IP address to compare

Date : 		November 2000

Desc : 		Compares an IP address to the default IP address defined
		in this module

***********************************************************************/
BYTE IPCompare (BYTE *IPOne) {
	if (IPOne [0] != IPAddress[0]) return (BYTE)0x00;
	if (IPOne [1] != IPAddress[1]) return (BYTE)0x00;
	if (IPOne [2] != IPAddress[2]) return (BYTE)0x00;
	if (IPOne [3] != IPAddress[3]) return (BYTE)0x00;

	return (BYTE) 0x01;
}



/***********************************************************************
Function : 	IPChecksum

Parameters : 	Data: A pointer to an array of Words
		Size: Size of the array

Date : 		August 2000

Desc : 		Obtains the IP checksum of an array of 16-bit words of size "Size"

***********************************************************************/
DWORD IPCheckSum (BYTE* Data, WORD Size) {
unsigned long	Sum = 0;

	while (Size-->0) {
		Sum += ((unsigned long)((*Data << 8) + *(Data+1)) & 0xFFFF);
		Data+=2;
	}

	Sum = (Sum >> 16) + (Sum & 0xFFFF);
	Sum += (Sum >> 16);

	return (WORD) ~Sum;
}