compat: backport ndo_get_stats64 addition

The net_device_ops data structure gets a new ndo_get_stats64
callback through two patches. For newer kernels that actually do
have the net_device_ops data structure we have no other option
but to #ifdef that code. For older kernels that do not have the
net_device_ops we stuff the new callback into this compat
module / header files and make netdev_attach_ops() ignore it.
And again -- for newer kernels just #ifdef that stuff out.

This is an example of a complex data structure series of
changes through different sets of collateral evolutions.
If we can figure out a way to not requre #ifdef changes
for *newer* kernels that *do* have the net_device_ops it
would be great. One way to likely accomplish this is to
redefine the net_device_ops data structure through a define
for all kernels and make it out own and in our own
netdev_attach_ops() routine handle the differences.
If this would be possible (needs to be proven but I think
Ozan has already proven this) I'm hopeful we'll eventually
be able to replace net_device_ops() collateral evolutions with
0 lines required to be changed on upstream code!

There are two patches that added ndo_get_stats64, fortunately
both were implemented during the 2.6.36 deveopment cycle.

mcgrof@tux ~/linux-next (git::master)$ git describe --contains be1f3c2c
v2.6.36-rc1~571^2~600
mcgrof@tux ~/linux-next (git::master)$ git describe --contains 28172739
v2.6.36-rc1~571^2~334

commit be1f3c2c027cc5ad735df6a45a542ed1db7ec48b
Author: Ben Hutchings <bhutchings@solarflare.com>
Date:   Tue Jun 8 07:19:54 2010 +0000

    net: Enable 64-bit net device statistics on 32-bit architectures

    Use struct rtnl_link_stats64 as the statistics structure.

    On 32-bit architectures, insert 32 bits of padding after/before each
    field of struct net_device_stats to make its layout compatible with
    struct rtnl_link_stats64.  Add an anonymous union in net_device; move
    stats into the union and add struct rtnl_link_stats64 stats64.

    Add net_device_ops::ndo_get_stats64, implementations of which will
    return a pointer to struct rtnl_link_stats64.  Drivers that implement
    this operation must not update the structure asynchronously.

    Change dev_get_stats() to call ndo_get_stats64 if available, and to
    return a pointer to struct rtnl_link_stats64.  Change callers of
    dev_get_stats() accordingly.

    Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

commit 28172739f0a276eb8d6ca917b3974c2edb036da3
Author: Eric Dumazet <eric.dumazet@gmail.com>
Date:   Wed Jul 7 14:58:56 2010 -0700

    net: fix 64 bit counters on 32 bit arches

    There is a small possibility that a reader gets incorrect values on 32
    bit arches. SNMP applications could catch incorrect counters when a
    32bit high part is changed by another stats consumer/provider.

    One way to solve this is to add a rtnl_link_stats64 param to all
    ndo_get_stats64() methods, and also add such a parameter to
    dev_get_stats().

    Rule is that we are not allowed to use dev->stats64 as a temporary
    storage for 64bit stats, but a caller provided area (usually on stack)

    Old drivers (only providing get_stats() method) need no changes.

    Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Luis R. Rodriguez <mcgrof@frijolero.org>