ethernet.c

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/*
 * 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 );