net/ethernet/eth.c

/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Ethernet-type device handling.
 *
 * Version:	@(#)eth.c	1.0.7	05/25/93
 *
 * Authors:	Ross Biro
 *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *		Mark Evans, <evansmp@uhura.aston.ac.uk>
 *		Florian  La Roche, <rzsfl@rz.uni-sb.de>
 *		Alan Cox, <gw4pts@gw4pts.ampr.org>
 * 
 * Fixes:
 *		Mr Linux	: Arp problems
 *		Alan Cox	: Generic queue tidyup (very tiny here)
 *		Alan Cox	: eth_header ntohs should be htons
 *		Alan Cox	: eth_rebuild_header missing an htons and
 *				  minor other things.
 *		Tegge		: Arp bug fixes. 
 *		Florian		: Removed many unnecessary functions, code cleanup
 *				  and changes for new arp and skbuff.
 *		Alan Cox	: Redid header building to reflect new format.
 *		Alan Cox	: ARP only when compiled with CONFIG_INET
 *		Greg Page	: 802.2 and SNAP stuff.
 *		Alan Cox	: MAC layer pointers/new format.
 *		Paul Gortmaker	: eth_copy_and_sum shouldn't csum padding.
 *		Alan Cox	: Protect against forwarding explosions with
 *				  older network drivers and IFF_ALLMULTI.
 *	Christer Weinigel	: Better rebuild header message.
 *             Andrew Morton    : 26Feb01: kill ether_setup() - use netdev_boot_setup().
 *
 *		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 (at your option) any later version.
 */
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/ip.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/errno.h>
#include <linux/config.h>
#include <linux/init.h>
#include <net/dst.h>
#include <net/arp.h>
#include <net/sock.h>
#include <net/ipv6.h>
#include <net/ip.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/checksum.h>

__setup("ether=", netdev_boot_setup);

/*
 *	 Create the Ethernet MAC header for an arbitrary protocol layer 
 *
 *	saddr=NULL	means use device source address
 *	daddr=NULL	means leave destination address (eg unresolved arp)
 */

int eth_header(struct sk_buff *skb, struct net_device *dev, unsigned short type,
	   void *daddr, void *saddr, unsigned len)
{
	struct ethhdr *eth = (struct ethhdr *)skb_push(skb,ETH_HLEN);

	/* 
	 *	Set the protocol type. For a packet of type ETH_P_802_3 we put the length
	 *	in here instead. It is up to the 802.2 layer to carry protocol information.
	 */
	
	if(type!=ETH_P_802_3) 
		eth->h_proto = htons(type);
	else
		eth->h_proto = htons(len);

	/*
	 *	Set the source hardware address. 
	 */
	 
	if(!saddr)
		saddr = dev->dev_addr;
	memcpy(eth->h_source,saddr,dev->addr_len);

	/*
	 *	Anyway, the loopback-device should never use this function... 
	 */

	if (dev->flags & (IFF_LOOPBACK|IFF_NOARP)) 
	{
		memset(eth->h_dest, 0, dev->addr_len);
		return ETH_HLEN;
	}
	
	if(daddr)
	{
		memcpy(eth->h_dest,daddr,dev->addr_len);
		return ETH_HLEN;
	}
	
	return -ETH_HLEN;
}


/*
 *	Rebuild the Ethernet MAC header. This is called after an ARP
 *	(or in future other address resolution) has completed on this
 *	sk_buff. We now let ARP fill in the other fields.
 *
 *	This routine CANNOT use cached dst->neigh!
 *	Really, it is used only when dst->neigh is wrong.
 */

int eth_rebuild_header(struct sk_buff *skb)
{
	struct ethhdr *eth = (struct ethhdr *)skb->data;
	struct net_device *dev = skb->dev;

	switch (eth->h_proto)
	{
#ifdef CONFIG_INET
	case __constant_htons(ETH_P_IP):
 		return arp_find(eth->h_dest, skb);
#endif	
	default:
		printk(KERN_DEBUG
		       "%s: unable to resolve type %X addresses.\n", 
		       dev->name, (int)eth->h_proto);
		
		memcpy(eth->h_source, dev->dev_addr, dev->addr_len);
		break;
	}

	return 0;
}

static inline unsigned int compare_eth_addr(const unsigned char *__a, const unsigned char *__b)
{
	const unsigned short *dest = (unsigned short *) __a;
	const unsigned short *devaddr = (unsigned short *) __b;
	unsigned int res;

	BUILD_BUG_ON(ETH_ALEN != 6);
	res = ((dest[0] ^ devaddr[0]) |
	       (dest[1] ^ devaddr[1]) |
	       (dest[2] ^ devaddr[2])) != 0;

	return res;
}

/*
 *	Determine the packet's protocol ID. The rule here is that we 
 *	assume 802.3 if the type field is short enough to be a length.
 *	This is normal practice and works for any 'now in use' protocol.
 */
 
__be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
{
	struct ethhdr *eth;
	unsigned char *rawp;
	
	skb->mac.raw = skb->data;
	skb_pull(skb,ETH_HLEN);
	eth = eth_hdr(skb);
	
	if (*eth->h_dest&1) {
		if (!compare_eth_addr(eth->h_dest, dev->broadcast))
			skb->pkt_type = PACKET_BROADCAST;
		else
			skb->pkt_type = PACKET_MULTICAST;
	}
	
	/*
	 *	This ALLMULTI check should be redundant by 1.4
	 *	so don't forget to remove it.
	 *
	 *	Seems, you forgot to remove it. All silly devices
	 *	seems to set IFF_PROMISC.
	 */
	 
	else if(1 /*dev->flags&IFF_PROMISC*/) {
		if (unlikely(compare_eth_addr(eth->h_dest, dev->dev_addr)))
			skb->pkt_type = PACKET_OTHERHOST;
	}
	
	if (ntohs(eth->h_proto) >= 1536)
		return eth->h_proto;
		
	rawp = skb->data;
	
	/*
	 *	This is a magic hack to spot IPX packets. Older Novell breaks
	 *	the protocol design and runs IPX over 802.3 without an 802.2 LLC
	 *	layer. We look for FFFF which isn't a used 802.2 SSAP/DSAP. This
	 *	won't work for fault tolerant netware but does for the rest.
	 */
	if (*(unsigned short *)rawp == 0xFFFF)
		return htons(ETH_P_802_3);
		
	/*
	 *	Real 802.2 LLC
	 */
	return htons(ETH_P_802_2);
}

static int eth_header_parse(struct sk_buff *skb, unsigned char *haddr)
{
	struct ethhdr *eth = eth_hdr(skb);
	memcpy(haddr, eth->h_source, ETH_ALEN);
	return ETH_ALEN;
}

int eth_header_cache(struct neighbour *neigh, struct hh_cache *hh)
{
	unsigned short type = hh->hh_type;
	struct ethhdr *eth;
	struct net_device *dev = neigh->dev;

	eth = (struct ethhdr*)
		(((u8*)hh->hh_data) + (HH_DATA_OFF(sizeof(*eth))));

	if (type == __constant_htons(ETH_P_802_3))
		return -1;

	eth->h_proto = type;
	memcpy(eth->h_source, dev->dev_addr, dev->addr_len);
	memcpy(eth->h_dest, neigh->ha, dev->addr_len);
	hh->hh_len = ETH_HLEN;
	return 0;
}

/*
 * Called by Address Resolution module to notify changes in address.
 */

void eth_header_cache_update(struct hh_cache *hh, struct net_device *dev, unsigned char * haddr)
{
	memcpy(((u8*)hh->hh_data) + HH_DATA_OFF(sizeof(struct ethhdr)),
	       haddr, dev->addr_len);
}

EXPORT_SYMBOL(eth_type_trans);

static int eth_mac_addr(struct net_device *dev, void *p)
{
	struct sockaddr *addr=p;
	if (netif_running(dev))
		return -EBUSY;
	memcpy(dev->dev_addr, addr->sa_data,dev->addr_len);
	return 0;
}

static int eth_change_mtu(struct net_device *dev, int new_mtu)
{
	if ((new_mtu < 68) || (new_mtu > 1500))
		return -EINVAL;
	dev->mtu = new_mtu;
	return 0;
}

/*
 * Fill in the fields of the device structure with ethernet-generic values.
 */
void ether_setup(struct net_device *dev)
{
	dev->change_mtu		= eth_change_mtu;
	dev->hard_header	= eth_header;
	dev->rebuild_header 	= eth_rebuild_header;
	dev->set_mac_address 	= eth_mac_addr;
	dev->hard_header_cache	= eth_header_cache;
	dev->header_cache_update= eth_header_cache_update;
	dev->hard_header_parse	= eth_header_parse;

	dev->type		= ARPHRD_ETHER;
	dev->hard_header_len 	= ETH_HLEN;
	dev->mtu		= 1500; /* eth_mtu */
	dev->addr_len		= ETH_ALEN;
	dev->tx_queue_len	= 1000;	/* Ethernet wants good queues */	
	dev->flags		= IFF_BROADCAST|IFF_MULTICAST;
	
	memset(dev->broadcast,0xFF, ETH_ALEN);

}
EXPORT_SYMBOL(ether_setup);

/**
 * alloc_etherdev - Allocates and sets up an ethernet device
 * @sizeof_priv: Size of additional driver-private structure to be allocated
 *	for this ethernet device
 *
 * Fill in the fields of the device structure with ethernet-generic
 * values. Basically does everything except registering the device.
 *
 * Constructs a new net device, complete with a private data area of
 * size @sizeof_priv.  A 32-byte (not bit) alignment is enforced for
 * this private data area.
 */

struct net_device *alloc_etherdev(int sizeof_priv)
{
	return alloc_netdev(sizeof_priv, "eth%d", ether_setup);
}
EXPORT_SYMBOL(alloc_etherdev);