/*
 * Fundamental constants relating to ethernet.
 *
 * $FreeBSD: src/sys/net/ethernet.h,v 1.24 2004/10/05 19:28:52 sam Exp $
 *
 */

#ifndef _FREEBSD_NET_ETHERNET_H_
#define _FREEBSD_NET_ETHERNET_H_

/*
 * Somce basic Ethernet constants.
 */
#define	ETHER_ADDR_LEN		6	/* length of an Ethernet address */
#define	ETHER_TYPE_LEN		2	/* length of the Ethernet type field */
#define	ETHER_CRC_LEN		4	/* length of the Ethernet CRC */
#define	ETHER_HDR_LEN		(ETHER_ADDR_LEN*2+ETHER_TYPE_LEN)
#define	ETHER_MIN_LEN		64	/* minimum frame len, including CRC */
#define	ETHER_MAX_LEN		1518	/* maximum frame len, including CRC */
#define	ETHER_MAX_LEN_JUMBO	9018	/* max jumbo frame len, including CRC */

#define	ETHER_VLAN_ENCAP_LEN	4	/* len of 802.1Q VLAN encapsulation */
/*
 * Mbuf adjust factor to force 32-bit alignment of IP header.
 * Drivers should do m_adj(m, ETHER_ALIGN) when setting up a
 * receive so the upper layers get the IP header properly aligned
 * past the 14-byte Ethernet header.
 */
#define	ETHER_ALIGN		2	/* driver adjust for IP hdr alignment */

/*
 * Compute the maximum frame size based on ethertype (i.e. possible
 * encapsulation) and whether or not an FCS is present.
 */
#define	ETHER_MAX_FRAME(ifp, etype, hasfcs)				\
	((ifp)->if_mtu + ETHER_HDR_LEN +				\
	 ((hasfcs) ? ETHER_CRC_LEN : 0) +				\
	 (((etype) == ETHERTYPE_VLAN) ? ETHER_VLAN_ENCAP_LEN : 0))

#endif