f8d0e3f115
When you turn off ARP on a netdevice then the first packet always goes
out with a dstMAC of all zeroes. This is because the first packet is
used to resolve ARP entries. Even though the ARP entry may be resolved
(I tried by setting a static ARP entry for a host i was pinging from),
it gets overwritten by virtue of having the netdevice disabling ARP.
Subsequent packets go out fine with correct dstMAC address (which may
be why people have ignored reporting this issue).
To cut the story short:
the culprit code is in net/ethernet/eth.c::eth_header()
----
/*
* 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;
}
----
Note how the h_dest is being reset when device has IFF_NOARP.
As a note:
All devices including loopback pass a daddr. loopback in fact passes
a 0 all the time ;->
This means i can delete the check totaly or i can remove the IFF_NOARP
Alexey says:
--------------------
I think, it was me who did this crap. It was so long ago I do not remember
why it was made.
I remember some troubles with dummy device. It tried to resolve
addresses, apparently, without success and generated errors instead of
blackholing. I think the problem was eventually solved at neighbour
level.
After some thinking I suspect the deletion of this chunk could change
behaviour of some parts which do not use neighbour cache f.e. packet
socket.
I think safer approach would be to move this chunk after if (daddr).
And the possibility to remove this completely could be analyzed later.
--------------------
Patch updated with Alexey's safer suggestions.
Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
Acked-by: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
303 lines
8 KiB
C
303 lines
8 KiB
C
/*
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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* operating system. INET is implemented using the BSD Socket
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* interface as the means of communication with the user level.
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*
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* Ethernet-type device handling.
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*
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* Version: @(#)eth.c 1.0.7 05/25/93
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*
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* Authors: Ross Biro
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* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
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* Mark Evans, <evansmp@uhura.aston.ac.uk>
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* Florian La Roche, <rzsfl@rz.uni-sb.de>
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* Alan Cox, <gw4pts@gw4pts.ampr.org>
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*
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* Fixes:
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* Mr Linux : Arp problems
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* Alan Cox : Generic queue tidyup (very tiny here)
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* Alan Cox : eth_header ntohs should be htons
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* Alan Cox : eth_rebuild_header missing an htons and
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* minor other things.
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* Tegge : Arp bug fixes.
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* Florian : Removed many unnecessary functions, code cleanup
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* and changes for new arp and skbuff.
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* Alan Cox : Redid header building to reflect new format.
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* Alan Cox : ARP only when compiled with CONFIG_INET
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* Greg Page : 802.2 and SNAP stuff.
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* Alan Cox : MAC layer pointers/new format.
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* Paul Gortmaker : eth_copy_and_sum shouldn't csum padding.
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* Alan Cox : Protect against forwarding explosions with
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* older network drivers and IFF_ALLMULTI.
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* Christer Weinigel : Better rebuild header message.
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* Andrew Morton : 26Feb01: kill ether_setup() - use netdev_boot_setup().
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/string.h>
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#include <linux/mm.h>
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#include <linux/socket.h>
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#include <linux/in.h>
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#include <linux/inet.h>
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#include <linux/ip.h>
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#include <linux/netdevice.h>
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#include <linux/etherdevice.h>
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#include <linux/skbuff.h>
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#include <linux/errno.h>
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#include <linux/config.h>
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#include <linux/init.h>
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#include <linux/if_ether.h>
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#include <net/dst.h>
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#include <net/arp.h>
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#include <net/sock.h>
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#include <net/ipv6.h>
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#include <net/ip.h>
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#include <asm/uaccess.h>
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#include <asm/system.h>
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#include <asm/checksum.h>
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__setup("ether=", netdev_boot_setup);
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/*
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* Create the Ethernet MAC header for an arbitrary protocol layer
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*
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* saddr=NULL means use device source address
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* daddr=NULL means leave destination address (eg unresolved arp)
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*/
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int eth_header(struct sk_buff *skb, struct net_device *dev, unsigned short type,
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void *daddr, void *saddr, unsigned len)
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{
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struct ethhdr *eth = (struct ethhdr *)skb_push(skb,ETH_HLEN);
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/*
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* Set the protocol type. For a packet of type ETH_P_802_3 we put the length
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* in here instead. It is up to the 802.2 layer to carry protocol information.
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*/
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if(type!=ETH_P_802_3)
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eth->h_proto = htons(type);
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else
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eth->h_proto = htons(len);
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/*
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* Set the source hardware address.
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*/
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if(!saddr)
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saddr = dev->dev_addr;
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memcpy(eth->h_source,saddr,dev->addr_len);
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if(daddr)
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{
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memcpy(eth->h_dest,daddr,dev->addr_len);
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return ETH_HLEN;
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}
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/*
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* Anyway, the loopback-device should never use this function...
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*/
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if (dev->flags & (IFF_LOOPBACK|IFF_NOARP))
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{
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memset(eth->h_dest, 0, dev->addr_len);
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return ETH_HLEN;
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}
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return -ETH_HLEN;
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}
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/*
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* Rebuild the Ethernet MAC header. This is called after an ARP
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* (or in future other address resolution) has completed on this
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* sk_buff. We now let ARP fill in the other fields.
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*
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* This routine CANNOT use cached dst->neigh!
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* Really, it is used only when dst->neigh is wrong.
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*/
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int eth_rebuild_header(struct sk_buff *skb)
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{
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struct ethhdr *eth = (struct ethhdr *)skb->data;
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struct net_device *dev = skb->dev;
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switch (eth->h_proto)
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{
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#ifdef CONFIG_INET
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case __constant_htons(ETH_P_IP):
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return arp_find(eth->h_dest, skb);
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#endif
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default:
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printk(KERN_DEBUG
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"%s: unable to resolve type %X addresses.\n",
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dev->name, (int)eth->h_proto);
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memcpy(eth->h_source, dev->dev_addr, dev->addr_len);
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break;
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}
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return 0;
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}
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/*
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* Determine the packet's protocol ID. The rule here is that we
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* assume 802.3 if the type field is short enough to be a length.
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* This is normal practice and works for any 'now in use' protocol.
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*/
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__be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
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{
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struct ethhdr *eth;
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unsigned char *rawp;
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skb->mac.raw = skb->data;
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skb_pull(skb,ETH_HLEN);
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eth = eth_hdr(skb);
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if (is_multicast_ether_addr(eth->h_dest)) {
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if (!compare_ether_addr(eth->h_dest, dev->broadcast))
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skb->pkt_type = PACKET_BROADCAST;
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else
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skb->pkt_type = PACKET_MULTICAST;
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}
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/*
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* This ALLMULTI check should be redundant by 1.4
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* so don't forget to remove it.
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*
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* Seems, you forgot to remove it. All silly devices
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* seems to set IFF_PROMISC.
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*/
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else if(1 /*dev->flags&IFF_PROMISC*/) {
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if (unlikely(compare_ether_addr(eth->h_dest, dev->dev_addr)))
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skb->pkt_type = PACKET_OTHERHOST;
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}
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if (ntohs(eth->h_proto) >= 1536)
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return eth->h_proto;
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rawp = skb->data;
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/*
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* This is a magic hack to spot IPX packets. Older Novell breaks
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* the protocol design and runs IPX over 802.3 without an 802.2 LLC
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* layer. We look for FFFF which isn't a used 802.2 SSAP/DSAP. This
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* won't work for fault tolerant netware but does for the rest.
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*/
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if (*(unsigned short *)rawp == 0xFFFF)
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return htons(ETH_P_802_3);
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/*
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* Real 802.2 LLC
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*/
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return htons(ETH_P_802_2);
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}
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static int eth_header_parse(struct sk_buff *skb, unsigned char *haddr)
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{
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struct ethhdr *eth = eth_hdr(skb);
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memcpy(haddr, eth->h_source, ETH_ALEN);
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return ETH_ALEN;
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}
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int eth_header_cache(struct neighbour *neigh, struct hh_cache *hh)
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{
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unsigned short type = hh->hh_type;
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struct ethhdr *eth;
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struct net_device *dev = neigh->dev;
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eth = (struct ethhdr*)
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(((u8*)hh->hh_data) + (HH_DATA_OFF(sizeof(*eth))));
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if (type == __constant_htons(ETH_P_802_3))
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return -1;
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eth->h_proto = type;
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memcpy(eth->h_source, dev->dev_addr, dev->addr_len);
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memcpy(eth->h_dest, neigh->ha, dev->addr_len);
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hh->hh_len = ETH_HLEN;
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return 0;
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}
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/*
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* Called by Address Resolution module to notify changes in address.
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*/
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void eth_header_cache_update(struct hh_cache *hh, struct net_device *dev, unsigned char * haddr)
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{
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memcpy(((u8*)hh->hh_data) + HH_DATA_OFF(sizeof(struct ethhdr)),
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haddr, dev->addr_len);
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}
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EXPORT_SYMBOL(eth_type_trans);
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static int eth_mac_addr(struct net_device *dev, void *p)
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{
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struct sockaddr *addr=p;
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if (netif_running(dev))
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return -EBUSY;
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memcpy(dev->dev_addr, addr->sa_data,dev->addr_len);
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return 0;
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}
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static int eth_change_mtu(struct net_device *dev, int new_mtu)
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{
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if (new_mtu < 68 || new_mtu > ETH_DATA_LEN)
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return -EINVAL;
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dev->mtu = new_mtu;
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return 0;
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}
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/*
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* Fill in the fields of the device structure with ethernet-generic values.
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*/
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void ether_setup(struct net_device *dev)
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{
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dev->change_mtu = eth_change_mtu;
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dev->hard_header = eth_header;
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dev->rebuild_header = eth_rebuild_header;
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dev->set_mac_address = eth_mac_addr;
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dev->hard_header_cache = eth_header_cache;
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dev->header_cache_update= eth_header_cache_update;
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dev->hard_header_parse = eth_header_parse;
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dev->type = ARPHRD_ETHER;
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dev->hard_header_len = ETH_HLEN;
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dev->mtu = ETH_DATA_LEN;
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dev->addr_len = ETH_ALEN;
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dev->tx_queue_len = 1000; /* Ethernet wants good queues */
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dev->flags = IFF_BROADCAST|IFF_MULTICAST;
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memset(dev->broadcast,0xFF, ETH_ALEN);
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}
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EXPORT_SYMBOL(ether_setup);
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/**
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* alloc_etherdev - Allocates and sets up an ethernet device
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* @sizeof_priv: Size of additional driver-private structure to be allocated
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* for this ethernet device
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*
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* Fill in the fields of the device structure with ethernet-generic
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* values. Basically does everything except registering the device.
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*
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* Constructs a new net device, complete with a private data area of
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* size @sizeof_priv. A 32-byte (not bit) alignment is enforced for
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* this private data area.
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*/
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struct net_device *alloc_etherdev(int sizeof_priv)
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{
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return alloc_netdev(sizeof_priv, "eth%d", ether_setup);
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}
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EXPORT_SYMBOL(alloc_etherdev);
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