pgpethernetheader.h

PGP8.0源码 请认真阅读您的文件包然后写出其具体功能

/*____________________________________________________________________________
	Copyright (C) 2002 PGP Corporation
	All rights reserved.
 
	$Id: pgpEthernetheader.h,v 1.2 2002/08/06 20:10:27 dallen Exp $
____________________________________________________________________________*/
#ifndef Included_pgpEthernetheader_h	/* [ */
#define Included_pgpEthernetheader_h

/*
 * The number of bytes in an ethernet (MAC) address.
 */
#define	kPGPnetEthernetAddressLength		6

/*
 * The number of bytes in the type field.
 */
#define	kPGPnetEthernetTypeLength		2

/*
 * The number of bytes in the trailing CRC field.
 */
#define	kPGPnetEthernetCRCLength		4

/*
 * The length of the combined header.
 */
#define	kPGPnetEthernetHeaderLength		((kPGPnetEthernetAddressLength * 2) + kPGPnetEthernetTypeLength)

/*
 * The minimum packet length.
 */
#define	kPGPnetEthernetMinLength		64

/*
 * The maximum packet length.
 */
#define	kPGPnetEthernetMaxLength		1518

/*
 * A macro to validate a length with
 */
#define	PGPnetEthernetIsValidLength(len)	\
			((len) >= kPGPnetEthernetMinLength && (len) <= kPGPnetEthernetMaxlength)

/*
 * Structure of a 10Mb/s Ethernet header.
 */
typedef struct PGPnetEthernetHeader {
	PGPUInt8	dhost[kPGPnetEthernetAddressLength];
	PGPUInt8	shost[kPGPnetEthernetAddressLength];
	PGPUInt16	type;
} PGPnetEthernetHeader;

/*
 * Structure of a 48-bit Ethernet address.
 */
typedef struct PGPnetEthernetAddress {
	PGPUInt8 octet[kPGPnetEthernetAddressLength];
} PGPnetEthernetAddress;

#define	kPGPnetEthernetType_IP			0x0800	/* IP protocol */
#define kPGPnetEthernetType_ARP			0x0806	/* Addr. resolution protocol */
#define kPGPnetEthernetType_RARP		0x8035	/* reverse Addr. resolution protocol */
#define	kPGPnetEthernetType_Loopback	0x9000	/* used to test interfaces */


#define	kPGPnetEthernetMTU	(kPGPnetEthernetMaxLength - kPGPnetEthernetHeaderLength - kPGPnetEthernetCRCLength)

#endif /*	Included_pgpEthernetheader_h	*/