alb_fasten_mac_swap (actually rlb_teach_disabled_mac_on_primary)
requries RTNL and no other locks. This could cause dev_set_promiscuity
and/or dev_set_mac_address to be called with improper locking.
Changed callers to hold only RTNL during calls to alb_fasten_mac_swap
or functions calling it. Updated header comments in affected functions to
reflect proper reality of locking requirements.
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Move an ASSERT_RTNL down to where we should hold only RTNL;
the existing check produces spurious warnings because we hold additional
locks at _bh, tripping a debug warning in spin_lock_mutex().
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Fix the functions that store the primary and active slave
options via sysfs to hold the correct locks in the correct order.
The bond_change_active_slave and bond_select_active_slave
functions both require rtnl, bond->lock for read and curr_slave_lock for
write_bh, and no other locks. This is so that the lower level
mode-specific functions (notably for balance-alb mode) can release locks
down to just rtnl in order to call, e.g., dev_set_mac_address with the
locks it expects (rtnl only).
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Fixes a race condition in module unload. Without this change,
workqueue events may fire while bonding data structures are partially
freed but before bond_close() is invoked by unregister_netdevice().
Update version to 3.2.3.
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Add new hash for balance-xor and 802.3ad modes. Originally
submitted by "Glenn Griffin" <ggriffin.kernel@gmail.com>; modified by
Jay Vosburgh to move setting of hash policy out of line, tweak the
documentation update and add version update to 3.2.2.
Glenn's original comment follows:
Included is a patch for a new xmit_hash_policy for the bonding driver
that selects slaves based on MAC and IP information. This is a middle
ground between what currently exists in the layer2 only policy and the
layer3+4 policy. This policy strives to be fully 802.3ad compliant by
transmitting every packet of any particular flow over the same link.
As documented the layer3+4 policy is not fully compliant for extreme
cases such as ip fragmentation, so this policy is a nice compromise
for environments that require full compliance but desire more than the
layer2 only policy.
Signed-off-by: "Glenn Griffin" <ggriffin.kernel@gmail.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
From: David Sterba <dsterba@suse.cz>
Use macros for comparing jiffies. Jiffies' wrap caused missed events and hangs.
Module reinsert was needed to make bonding work again.
Signed-off-by: David Sterba <dsterba@suse.cz>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
From: Wagner Ferenc <wferi@niif.hu>
For consistency with the behaviour of the arp_ip_target option,
let /sys/class/net/bond0/bonding/xmit_hash_policy accept and report
current policy even if the bonding mode in effect does not use it.
Signed-off-by: Ferenc Wagner <wferi@niif.hu>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
From: Wagner Ferenc <wferi@niif.hu>
Adhere to coding style: break line after the if condition
Signed-off-by: Ferenc Wagner <wferi@niif.hu>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
From: Wagner Ferenc <wferi@niif.hu>
Code for rendering multivalue sysfs files occurs three times
in this module. Rename 'buffer' to 'buf' in the first, for
the sake of consistency.
Signed-off-by: Ferenc Wagner <wferi@niif.hu>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
From: Wagner Ferenc <wferi@niif.hu>
The previous code returned '\n' (that is, a single empty line)
from most files, with one exception (xmit_hash_policy), where
it returned 'NA\n'. This patch consolidates each file to return
nothing at all if not applicable, not even a '\n'.
I find this behaviour more usual, more useful, more efficient
and shorter to code from both sides.
Signed-off-by: Ferenc Wagner <wferi@niif.hu>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
From: Wagner Ferenc <wferi@niif.hu>
Also remove trailing spaces from multivalued files.
This fixes output like for example:
$ od -c /sys/class/net/bond0/bonding/slaves
0000000 e t h - l e f t e t h - r i g
0000020 h t \n \0
0000025
It mostly entails deleting '+1'-s after sprintf() calls: the return value
of sprintf is the number of characters printed, without the closing NUL,
ie. exactly what the sysfs interface requires. The three multivalue
cases are different, because they also have to swallow back a trailing
space.
Signed-off-by: Ferenc Wagner <wferi@niif.hu>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Fix bond_destroy and bond_free_all to not reference the struct
net_device after calling unregister_netdevice.
Bug and offending change reported by Moni Shoua <monis@voltaire.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The standard validate_addr handler refuses to accept the all zeroes address
as valid. However, it's common historical practice for the bonding
master to be configured up prior to having any slaves, at which time the
master will have a MAC address of all zeroes.
Resolved by setting the dev->validate_addr to NULL. The master still can't
end up with an invalid address, as the set_mac_address function tests
for validity.
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Looks like I incorrectly merged one of the rtnl lock changes,
so that one function, bonding_show_active_slave, held rtnl but didn't
release it, and another, bonding_store_active_slave, never held rtnl but
did release it.
Fixed so the first function doesn't mess with rtnl, and the
second correctly acquires and releases rtnl.
Bug reported by Moni Shoua <monis@voltaire.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Update ALB mode monitor to hold correct locks (RTNL and nothing
else) when calling dev_set_promiscuity.
Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Convert more lock acquisitions to _bh flavor to avoid deadlock
with workqueue activity and add acquisition of RTNL in appropriate places.
Affects ALB mode, as well as core bonding functions and sysfs.
Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Convert locking-related activity to new & improved system.
Convert some lock acquisitions to _bh and rework parts of ALB mode, both
to avoid deadlocks with workqueue activity.
Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Convert mii (link state) monitor to acquire correct locks for
failover events. In particular, failovers generally require RTNL at a low
level (when manipulating device MAC addresses, for example) and no other
locks. The high level monitor is responsible for acquiring a known set
of locks, RTNL, the bond->lock for read and the slave_lock for write, and
the low level failover processing can then release appropriate locks as
needed. This patch provides the high level portion.
As it is undesirable to acquire RTNL for every monitor pass (which
may occur as often as every 10 ms), the miimon has been converted to
do conditional locking. A first pass inspects all slaves to determine
if any action is required, and if so, a second pass (after acquring RTNL)
is done to perform any actions (doing a complete rescan, as the situation
may have changed when all locks were released).
Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Change locking in balance-rr transmit processing to use a free
running counter to determine which slave to transmit on. Instead, a
free-running counter is maintained, and modulo arithmetic used to select
a slave for transmit.
This removes lock operations from the TX path, and eliminates
a deadlock introduced by the conversion to work queues.
Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Convert bonding timers to workqueues. This converts the various
monitor functions to run in periodic work queues instead of timers. This
patch introduces the framework and convers the calls, but does not resolve
various locking issues, and does not stand alone.
Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Fix the various misspellings of "system", controller", "interrupt" and
"[un]necessary".
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Prior to use struct marker in the linux kernel markers, we need to clean
two drivers which use this structure name.
Change bonding driver types :
- struct marker to struct bond_marker.
- marker_t to bond_marker_t.
- marker_header to bond_marker_header.
- marker_header_t to bond_marker_header_t.
Change qla4xxx struct marker_entry usage :
- Change struct marker_entry for struct qla4_marker_entry.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Chad Tindel <ctindel@users.sourceforge.net>
Cc: Jay Vosburgh <fubar@us.ibm.com>
Cc: David Somayajulu <david.somayajulu@qlogic.com>
Cc: James Bottomley <James.Bottomley@SteelEye.com>
Cc: Ravi Anand <ravi.anand@qlogic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Two small fixes to IPoIB support for bonding:
1- copy header_ops from slave to bonding for IPoIB slaves
2- move release and destroy logic to UNREGISTER from GOING_DOWN
notifier to avoid double release
Set bonding to version 3.2.1.
Signed-off-by: Moni Shoua <monis at voltaire.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Update the "don't change MAC of slaves" functionality added in
previous changes to be a generic option, rather than something tied to
IB devices, as it's occasionally useful for regular ethernet devices as
well.
Adds "fail_over_mac" option (which is automatically enabled for IB
slaves), applicable only to active-backup mode.
Includes documentation update.
Updates bonding driver version to 3.2.0.
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
When bonding enslaves non Ethernet devices it takes pointers to functions
in the module that owns the slaves. In this case it becomes unsafe
to keep the bonding master registered after last slave was unenslaved
because we don't know if the pointers are still valid. Destroying the bond when slave_cnt is zero
ensures that these functions be used anymore.
Signed-off-by: Moni Shoua <monis at voltaire.com>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Delay sending a gratuitous_arp when LINK_STATE_LINKWATCH_PENDING bit
in dev->state field is on. This improves the chances for the arp packet to
be transmitted.
Signed-off-by: Moni Shoua <monis at voltaire.com>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
bonding sometimes uses Ethernet constants (such as MTU and address length) which
are not good when it enslaves non Ethernet devices (such as InfiniBand).
Signed-off-by: Moni Shoua <monis at voltaire.com>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Allow to enslave devices when the bonding device is not up. Over the discussion
held at the previous post this seemed to be the most clean way to go, where it
is not expected to cause instabilities.
Normally, the bonding driver is UP before any enslavement takes place.
Once a netdevice is UP, the network stack acts to have it join some multicast groups
(eg the all-hosts 224.0.0.1). Now, since ether_setup() have set the bonding device
type to be ARPHRD_ETHER and address len to be ETHER_ALEN, the net core code
computes a wrong multicast link address. This is b/c ip_eth_mc_map() is called
where for multicast joins taking place after the enslavement another ip_xxx_mc_map()
is called (eg ip_ib_mc_map() when the bond type is ARPHRD_INFINIBAND)
Signed-off-by: Moni Shoua <monis at voltaire.com>
Signed-off-by: Or Gerlitz <ogerlitz at voltaire.com>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
This patch allows for enslaving netdevices which do not support
the set_mac_address() function. In that case the bond mac address is the one
of the active slave, where remote peers are notified on the mac address
(neighbour) change by Gratuitous ARP sent by bonding when fail-over occurs
(this is already done by the bonding code).
Signed-off-by: Moni Shoua <monis at voltaire.com>
Signed-off-by: Or Gerlitz <ogerlitz at voltaire.com>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
This patch changes some of the bond netdevice attributes and functions
to be that of the active slave for the case of the enslaved device not being
of ARPHRD_ETHER type. Basically it overrides those setting done by ether_setup(),
which are netdevice **type** dependent and hence might be not appropriate for
devices of other types. It also enforces mutual exclusion on bonding slaves
from dissimilar ether types, as was concluded over the v1 discussion.
IPoIB (see Documentation/infiniband/ipoib.txt) MAC address is made of a 3 bytes
IB QP (Queue Pair) number and 16 bytes IB port GID (Global ID) of the port this
IPoIB device is bounded to. The QP is a resource created by the IB HW and the
GID is an identifier burned into the HCA (i have omitted here some details which
are not important for the bonding RFC).
Signed-off-by: Moni Shoua <monis at voltaire.com>
Signed-off-by: Or Gerlitz <ogerlitz at voltaire.com>
Acked-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
For the operations
get-tx-csum
get-sg
get-tso
get-ufo
the default ethtool_op_xxx behavior is fine for all drivers, so we
permit op==NULL to imply the default behavior.
This provides a more uniform behavior across all drivers, eliminating
ethtool(8) "ioctl not supported" errors on older drivers that had
not been updated for the latest sub-ioctls.
The ethtool_op_xxx() functions are left exported, in case anyone
wishes to call them directly from a driver-private implementation --
a not-uncommon case. Should an ethtool_op_xxx() helper remain unused
for a while, except by net/core/ethtool.c, we can un-export it at a
later date.
[ Resolved conflicts with set/get value ethtool patch... -DaveM ]
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
It's been a useless no-op for long enough in 2.6 so I figured it's time to
remove it. The number of people that could object because they're
maintaining unified 2.4 and 2.6 drivers is probably rather small.
[ Handled drivers added by netdev tree and some missed IRDA cases... -DaveM ]
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch cleans up duplicate includes in
drivers/net/
Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Acked-by: "John W. Linville" <linville@tuxdriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
This patch makes most of the generic device layer network
namespace safe. This patch makes dev_base_head a
network namespace variable, and then it picks up
a few associated variables. The functions:
dev_getbyhwaddr
dev_getfirsthwbytype
dev_get_by_flags
dev_get_by_name
__dev_get_by_name
dev_get_by_index
__dev_get_by_index
dev_ioctl
dev_ethtool
dev_load
wireless_process_ioctl
were modified to take a network namespace argument, and
deal with it.
vlan_ioctl_set and brioctl_set were modified so their
hooks will receive a network namespace argument.
So basically anthing in the core of the network stack that was
affected to by the change of dev_base was modified to handle
multiple network namespaces. The rest of the network stack was
simply modified to explicitly use &init_net the initial network
namespace. This can be fixed when those components of the network
stack are modified to handle multiple network namespaces.
For now the ifindex generator is left global.
Fundametally ifindex numbers are per namespace, or else
we will have corner case problems with migration when
we get that far.
At the same time there are assumptions in the network stack
that the ifindex of a network device won't change. Making
the ifindex number global seems a good compromise until
the network stack can cope with ifindex changes when
you change namespaces, and the like.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Every user of the network device notifiers is either a protocol
stack or a pseudo device. If a protocol stack that does not have
support for multiple network namespaces receives an event for a
device that is not in the initial network namespace it quite possibly
can get confused and do the wrong thing.
To avoid problems until all of the protocol stacks are converted
this patch modifies all netdev event handlers to ignore events on
devices that are not in the initial network namespace.
As the rest of the code is made network namespace aware these
checks can be removed.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch modifies every packet receive function
registered with dev_add_pack() to drop packets if they
are not from the initial network namespace.
This should ensure that the various network stacks do
not receive packets in a anything but the initial network
namespace until the code has been converted and is ready
for them.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch makes /proc/net per network namespace. It modifies the global
variables proc_net and proc_net_stat to be per network namespace.
The proc_net file helpers are modified to take a network namespace argument,
and all of their callers are fixed to pass &init_net for that argument.
This ensures that all of the /proc/net files are only visible and
usable in the initial network namespace until the code behind them
has been updated to be handle multiple network namespaces.
Making /proc/net per namespace is necessary as at least some files
in /proc/net depend upon the set of network devices which is per
network namespace, and even more files in /proc/net have contents
that are relevant to a single network namespace.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
http://bugzilla.kernel.org/show_bug.cgi?id=8797 shows that the
bonding driver may produce bogus combinations of the checksum
flags and SG/TSO.
For example, if you bond devices with NETIF_F_HW_CSUM and
NETIF_F_IP_CSUM you'll end up with a bonding device that
has neither flag set. If both have TSO then this produces
an illegal combination.
The bridge device on the other hand has the correct code to
deal with this.
In fact, the same code can be used for both. So this patch
moves that logic into net/core/dev.c and uses it for both
bonding and bridging.
In the process I've made small adjustments such as only
setting GSO_ROBUST if at least one constituent device
supports it.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
During the transition to the ethtool_ops way of doing things, we supported
calling the device's ->do_ioctl method to allow unconverted drivers to
continue working. Those days are long behind us, all in-tree drivers
use the ethtool_ops way, and so we no longer need to support this.
The bonding driver is the biggest beneficiary of this; it no longer
needs to call ioctl() as a fallback if ethtool_ops aren't supported.
Also put a proper copyright statement on ethtool.c.
Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Cc: Chad Tindel <ctindel@users.sourceforge.net>
Cc: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
At present, when a device is enslaved to bonding, if ipv6 is
active then addrconf will be initated on the slave (because it is closed
then opened during the enslavement processing). This causes DAD and RS
packets to be sent from the slave. These packets in turn can confuse
switches that perform ipv6 snooping, causing them to incorrectly update
their forwarding tables (if, e.g., the slave being added is an inactve
backup that won't be used right away) and direct traffic away from the
active slave to a backup slave (where the incoming packets will be
dropped).
This patch alters the behavior so that addrconf will only run on
the master device itself. I believe this is logically correct, as it
prevents slaves from having an IPv6 identity independent from the
master. This is consistent with the IPv4 behavior for bonding.
This is accomplished by (a) having bonding set IFF_SLAVE sooner
in the enslavement processing than currently occurs (before open, not
after), and (b) having ipv6 addrconf ignore UP and CHANGE events on
slave devices.
The eql driver also uses the IFF_SLAVE flag. I inspected eql,
and I believe this change is reasonable for its usage of IFF_SLAVE, but
I did not test it.
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Modify carrier state determination for 802.3ad mode to comply
with section 43.3.9 of IEEE 802.3, which requires that "Links that are
not successful candidates for aggregation (e.g., links that are attached
to other devices that cannot perform aggregation or links that have been
manually configured to be non-aggregatable) are enabled to operate as
individual IEEE 802.3 links."
Bug reported by Laurent Chavey <chavey@google.com>. This patch
is an updated version of his patch that changes the wording of
commentary and adds an update to the driver version.
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Laurent Chavey <chavey@google.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
The following patch (based on a patch from Stephen Hemminger
<shemminger@linux-foundation.org>) removes use after free conditions in
the unregister path for the bonding master. Without this patch, an
operation of the form "echo -bond0 > /sys/class/net/bonding_masters"
would trigger a NULL pointer dereference in sysfs. I was not able to
induce the failure with the non-sysfs code path, but for consistency I
updated that code as well.
I also did some testing of the bonding /proc file being open
while the bond is being deleted, and didn't see any problems there.
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Herbert Xu conviced me that a new flag was overkill; every driver
currently overrides get_stats, so we might as well make the internal
one the default. If someone did fail to set get_stats, they would now
get all 0 stats instead of "No statistics available".
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Network drivers which keep stats allocate their own stats structure
then write a get_stats() function to return them. It would be nice if
this were done by default.
1) Add a new "stats" field to "struct net_device".
2) Add a new feature field to say "this driver uses the internal one"
3) Have a default "get_stats" which returns NULL if that feature not set.
4) Change callers to check result of get_stats call for NULL, not if
->get_stats is set.
This should not break backwards compatibility with older drivers, yet
allow modern drivers to shed some boilerplate code.
Lightly tested: works for a modified lguest network driver.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
