src/net/ethernet.c

/*
 * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <byteswap.h>
#include <errno.h>
#include <assert.h>
#include <ipxe/if_arp.h>
#include <ipxe/if_ether.h>
#include <ipxe/in.h>
#include <ipxe/netdevice.h>
#include <ipxe/iobuf.h>
#include <ipxe/ethernet.h>

/** @file
 *
 * Ethernet protocol
 *
 */

/** Ethernet broadcast MAC address */
uint8_t eth_broadcast[ETH_ALEN] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };

/**
 * Check if Ethernet packet has an 802.3 LLC header
 *
 * @v ethhdr		Ethernet header
 * @ret is_llc		Packet has 802.3 LLC header
 */
static inline int eth_is_llc_packet ( struct ethhdr *ethhdr ) {
	uint8_t len_msb;

	/* Check if the protocol field contains a value short enough
	 * to be a frame length.  The slightly convoluted form of the
	 * comparison is designed to reduce to a single x86
	 * instruction.
	 */
	len_msb = *( ( uint8_t * ) &ethhdr->h_protocol );
	return ( len_msb < 0x06 );
}

/**
 * Add Ethernet link-layer header
 *
 * @v netdev		Network device
 * @v iobuf		I/O buffer
 * @v ll_dest		Link-layer destination address
 * @v ll_source		Source link-layer address
 * @v net_proto		Network-layer protocol, in network-byte order
 * @ret rc		Return status code
 */
int eth_push ( struct net_device *netdev __unused, struct io_buffer *iobuf,
	       const void *ll_dest, const void *ll_source,
	       uint16_t net_proto ) {
	struct ethhdr *ethhdr = iob_push ( iobuf, sizeof ( *ethhdr ) );

	/* Build Ethernet header */
	memcpy ( ethhdr->h_dest, ll_dest, ETH_ALEN );
	memcpy ( ethhdr->h_source, ll_source, ETH_ALEN );
	ethhdr->h_protocol = net_proto;

	return 0;
}

/**
 * Remove Ethernet link-layer header
 *
 * @v netdev		Network device
 * @v iobuf		I/O buffer
 * @ret ll_dest		Link-layer destination address
 * @ret ll_source	Source link-layer address
 * @ret net_proto	Network-layer protocol, in network-byte order
 * @ret flags		Packet flags
 * @ret rc		Return status code
 */
int eth_pull ( struct net_device *netdev __unused, struct io_buffer *iobuf,
	       const void **ll_dest, const void **ll_source,
	       uint16_t *net_proto, unsigned int *flags ) {
	struct ethhdr *ethhdr = iobuf->data;
	uint16_t *llc_proto;

	/* Sanity check.  While in theory we could receive a one-byte
	 * packet, this will never happen in practice and performing
	 * the combined length check here avoids the need for an
	 * additional comparison if we detect an LLC frame.
	 */
	if ( iob_len ( iobuf ) < ( sizeof ( *ethhdr ) + sizeof ( *llc_proto ))){
		DBG ( "Ethernet packet too short (%zd bytes)\n",
		      iob_len ( iobuf ) );
		return -EINVAL;
	}

	/* Strip off Ethernet header */
	iob_pull ( iobuf, sizeof ( *ethhdr ) );

	/* Fill in required fields */
	*ll_dest = ethhdr->h_dest;
	*ll_source = ethhdr->h_source;
	*net_proto = ethhdr->h_protocol;
	*flags = ( ( is_multicast_ether_addr ( ethhdr->h_dest ) ?
		     LL_MULTICAST : 0 ) |
		   ( is_broadcast_ether_addr ( ethhdr->h_dest ) ?
		     LL_BROADCAST : 0 ) );

	/* If this is an LLC frame (with a length in place of the
	 * protocol field), then use the next two bytes (which happen
	 * to be the LLC DSAP and SSAP) as the protocol.  This allows
	 * for minimal-overhead support for receiving (rare) LLC
	 * frames, without requiring a full LLC protocol layer.
	 */
	if ( eth_is_llc_packet ( ethhdr ) ) {
		llc_proto = iobuf->data;
		*net_proto = *llc_proto;
	}

	return 0;
}

/**
 * Initialise Ethernet address
 *
 * @v hw_addr		Hardware address
 * @v ll_addr		Link-layer address
 */
void eth_init_addr ( const void *hw_addr, void *ll_addr ) {
	memcpy ( ll_addr, hw_addr, ETH_ALEN );
}

/**
 * Generate random Ethernet address
 *
 * @v hw_addr		Generated hardware address
 */
void eth_random_addr ( void *hw_addr ) {
	uint8_t *addr = hw_addr;
	unsigned int i;

	for ( i = 0 ; i < ETH_ALEN ; i++ )
		addr[i] = random();
	addr[0] &= ~0x01; /* Clear multicast bit */
	addr[0] |= 0x02; /* Set locally-assigned bit */
}

/**
 * Transcribe Ethernet address
 *
 * @v ll_addr		Link-layer address
 * @ret string		Link-layer address in human-readable format
 */
const char * eth_ntoa ( const void *ll_addr ) {
	static char buf[18]; /* "00:00:00:00:00:00" */
	const uint8_t *eth_addr = ll_addr;

	sprintf ( buf, "%02x:%02x:%02x:%02x:%02x:%02x",
		  eth_addr[0], eth_addr[1], eth_addr[2],
		  eth_addr[3], eth_addr[4], eth_addr[5] );
	return buf;
}

/**
 * Hash multicast address
 *
 * @v af		Address family
 * @v net_addr		Network-layer address
 * @v ll_addr		Link-layer address to fill in
 * @ret rc		Return status code
 */
int eth_mc_hash ( unsigned int af, const void *net_addr, void *ll_addr ) {
	const uint8_t *net_addr_bytes = net_addr;
	uint8_t *ll_addr_bytes = ll_addr;

	switch ( af ) {
	case AF_INET:
		ll_addr_bytes[0] = 0x01;
		ll_addr_bytes[1] = 0x00;
		ll_addr_bytes[2] = 0x5e;
		ll_addr_bytes[3] = net_addr_bytes[1] & 0x7f;
		ll_addr_bytes[4] = net_addr_bytes[2];
		ll_addr_bytes[5] = net_addr_bytes[3];
		return 0;
	case AF_INET6:
		ll_addr_bytes[0] = 0x33;
		ll_addr_bytes[1] = 0x33;
		memcpy ( &ll_addr_bytes[2], &net_addr_bytes[12], 4 );
		return 0;
	default:
		return -ENOTSUP;
	}
}

/**
 * Generate Ethernet-compatible compressed link-layer address
 *
 * @v ll_addr		Link-layer address
 * @v eth_addr		Ethernet-compatible address to fill in
 */
int eth_eth_addr ( const void *ll_addr, void *eth_addr ) {
	memcpy ( eth_addr, ll_addr, ETH_ALEN );
	return 0;
}

/**
 * Generate EUI-64 address
 *
 * @v ll_addr		Link-layer address
 * @v eui64		EUI-64 address to fill in
 * @ret rc		Return status code
 */
int eth_eui64 ( const void *ll_addr, void *eui64 ) {

	memcpy ( ( eui64 + 0 ), ( ll_addr + 0 ), 3 );
	memcpy ( ( eui64 + 5 ), ( ll_addr + 3 ), 3 );
	*( ( uint16_t * ) ( eui64 + 3 ) ) = htons ( 0xfffe );
	return 0;
}

/** Ethernet protocol */
struct ll_protocol ethernet_protocol __ll_protocol = {
	.name		= "Ethernet",
	.ll_proto	= htons ( ARPHRD_ETHER ),
	.hw_addr_len	= ETH_ALEN,
	.ll_addr_len	= ETH_ALEN,
	.ll_header_len	= ETH_HLEN,
	.push		= eth_push,
	.pull		= eth_pull,
	.init_addr	= eth_init_addr,
	.ntoa		= eth_ntoa,
	.mc_hash	= eth_mc_hash,
	.eth_addr	= eth_eth_addr,
	.eui64		= eth_eui64,
};

/**
 * Allocate Ethernet device
 *
 * @v priv_size		Size of driver private data
 * @ret netdev		Network device, or NULL
 */
struct net_device * alloc_etherdev ( size_t priv_size ) {
	struct net_device *netdev;

	netdev = alloc_netdev ( priv_size );
	if ( netdev ) {
		netdev->ll_protocol = &ethernet_protocol;
		netdev->ll_broadcast = eth_broadcast;
		netdev->max_pkt_len = ETH_FRAME_LEN;
		netdev->mtu = ETH_MAX_MTU;
	}
	return netdev;
}

/* Drag in objects via ethernet_protocol */
REQUIRING_SYMBOL ( ethernet_protocol );

/* Drag in Ethernet configuration */
REQUIRE_OBJECT ( config_ethernet );