When same struct dst_entry can be used for many different
neighbours we can not use it for pending confirmations.
Use the new sk_dst_confirm() helper to propagate the
indication from received packets to sock_confirm_neigh().
Reported-by: NYueHaibing <yuehaibing@huawei.com>
Fixes: 5110effe ("net: Do delayed neigh confirmation.")
Fixes: f2bb4bed ("ipv4: Cache output routes in fib_info nexthops.")
Tested-by: NYueHaibing <yuehaibing@huawei.com>
Signed-off-by: NJulian Anastasov <ja@ssi.bg>
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add new transport flag to allow sockets to confirm neighbour.
When same struct dst_entry can be used for many different
neighbours we can not use it for pending confirmations.
The flag is propagated from transport to every packet.
It is reset when cached dst is reset.
Reported-by: NYueHaibing <yuehaibing@huawei.com>
Fixes: 5110effe ("net: Do delayed neigh confirmation.")
Fixes: f2bb4bed ("ipv4: Cache output routes in fib_info nexthops.")
Signed-off-by: NJulian Anastasov <ja@ssi.bg>
Acked-by: NEric Dumazet <edumazet@google.com>
Acked-by: NNeil Horman <nhorman@tuxdriver.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add new skbuff flag to allow protocols to confirm neighbour.
When same struct dst_entry can be used for many different
neighbours we can not use it for pending confirmations.

Add sock_confirm_neigh() helper to confirm the neighbour and
use it for IPv4, IPv6 and VRF before dst_neigh_output.
Signed-off-by: NJulian Anastasov <ja@ssi.bg>
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add new sock flag to allow sockets to confirm neighbour.
When same struct dst_entry can be used for many different
neighbours we can not use it for pending confirmations.
As not all call paths lock the socket use full word for
the flag.

Add sk_dst_confirm as replacement for dst_confirm when
called for received packets.
Signed-off-by: NJulian Anastasov <ja@ssi.bg>
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add the BCM74371 PHY ID to the list of supported chips. This is a 28nm
technology Gigabit PHY SoC.
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

When PSAMPLE is a loadable module, spectrum must not be built-in:

drivers/net/built-in.o: In function `mlxsw_sp_rx_listener_sample_func':
spectrum.c:(.text+0xe357e): undefined reference to `psample_sample_packet'

This adds a Kconfig dependency to enforce usable configurations.

Fixes: 98d0f7b9 ("mlxsw: spectrum: Add packet sample offloading support")
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NYotam Gigi <yotamg@mellanox.com>
Acked-by: NJiri Pirko <jiri@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Fixes the following sparse warnings:

net/ipv6/seg6_iptunnel.c:58:5: warning:
 symbol 'nla_put_srh' was not declared. Should it be static?
net/ipv6/seg6_iptunnel.c:238:5: warning:
 symbol 'seg6_input' was not declared. Should it be static?
net/ipv6/seg6_iptunnel.c:254:5: warning:
 symbol 'seg6_output' was not declared. Should it be static?
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Remove duplicated include.
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Remove .owner field if calls are used which set it automatically.

Generated by: scripts/coccinelle/api/platform_no_drv_owner.cocci
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

module_spi_driver() makes the code simpler by eliminating
boilerplate code.
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Florian Fainelli says:

====================
net: dsa: Support for pdata in dsa2

This is not exactly new, and was sent before, although back then, I did not
have an user of the pre-declared MDIO board information, but now we do. Note
that I have additional changes queued up to have b53 register platform data for
MIPS bcm47xx and bcm63xx.

Yes I know that we should have the Orion platforms eventually be converted to
Device Tree, but until that happens, I don't want any remaining users of the
old "dsa" platform device (hence the previous DTS submissions for ARM/mvebu)
and, there will be platforms out there that most likely won't never see DT
coming their way (BCM47xx is almost 100% sure, BCM63xx maybe not in a distant
future).

We would probably want the whole series to be merged via David Miller's tree
to simplify things.

Thanks!

Changes in v5:

- dropped changes to drivers/base/ because after more than a month, we cannot
  get any answer from Greg KH

Changes in v4:

- Changed device_find_class() to device_find_in_class_name()
- Added kerneldoc above device_find_in_class_name() to explain what it does
  and the calling convention regarding device reference counts
- Changed dev_to_net_device to device_to_net_device() added comments
  about what it does and the caller conventions regarding reference counts

Changes in v3:

- Tested EPROBE_DEFER from a mockup MDIO/DSA switch driver and everything
  is fine, once the driver finally probes we have access to platform data
  as expected

- added comment above dsa_port_is_valid() that port->name is mandatory
  for platform data cases

- added an extra check in dsa_parse_member() for a NULL pdata pointer

- fixed a bunch of checkpatch errors and warnings

Changes in v2:

- Rebased against latest net-next/master

- Moved dev_find_class() to device_find_class() into drivers/base/core.c

- Moved dev_to_net_device into net/core/dev.c

- Utilize dsa_chip_data directly instead of dsa_platform_data

- Augmented dsa_chip_data to be multi-CPU port ready

Changes from last submission (few months back):

- rebased against latest net-next

- do not introduce dsa2_platform_data which was overkill and was meant to
  allow us to do exaclty the same things with platform data and Device Tree
  we use the existing dsa_platform_data instead

- properly register MDIO devices when the MDIO bus is registered and associate
  platform_data with them

- add a change to the Orion platform code to demonstrate how this can be used

Thank you
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Utilize the ability to pass board specific MDIO bus information towards a
particular MDIO device thus allowing us to provide the per-port switch layout
to the Marvell 88E6XXX switch driver.

Since we would end-up with conflicting registration paths, do not register the
"dsa" platform device anymore.

Note that the MDIO devices registered by code in net/dsa/dsa2.c does not
parse a dsa_platform_data, but directly take a dsa_chip_data (specific
to a single switch chip), so we update the different call sites to pass
this structure down to orion_ge00_switch_init().
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Allow board support code to collect pre-declarations for MDIO devices by
registering them with mdiobus_register_board_info(). SPI and I2C buses
have a similar feature, we were missing this for MDIO devices, but this
is particularly useful for e.g: MDIO-connected switches which need to
provide their port layout (often board-specific) to a MDIO Ethernet
switch driver.
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Allow drivers to use the new DSA API with platform data. Most of the
code in net/dsa/dsa2.c does not rely so much on device_nodes and can get
the same information from platform_data instead.

We purposely do not support distributed configurations with platform
data, so drivers should be providing a pointer to a 'struct
dsa_chip_data' structure if they wish to communicate per-port layout.

Multiple CPUs port could potentially be supported and dsa_chip_data is
extended to receive up to one reference to an upstream network device
per port described by a dsa_chip_data structure.

dsa_dev_to_net_device() increments the network device's reference count,
so we intentionally call dev_put() to be consistent with the DT-enabled
path, until we have a generic notifier based solution.
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In preparation for using this function in net/dsa/dsa2.c, rename the function
to make its scope DSA specific, and export it.
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Move the remaining port configuration code which varies per device
into port.c, using ops were necessary. This makes
mv88e6xxx_6185_family() and mv88e6xxx_6095_family() unused, so remove
them.
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
Reviewed-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The mv88e6390 MDIO bus controllers can support for clause 45 accesses.
The internal SERDES interfaces need this, and it is likely external
10GHz PHYs will be clause 45.
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
Reviewed-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Andrew Lunn says:

====================
Set the CMODE for mv88e6390 ports

The mv88e6390 ports 9 & 10 allow there CMODE to be set. CMODE is part
of what linux defines as phy-mode. Add the needed phy-modes to linux,
and add code which will act upon the phy-mode property to configure
the switch port.

These patches have been posted before as part of a bigger patchset
which has now been broken up. I've added the received reviewed by
tags, and added device tree documentation.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Unlike most ports, ports 9 and 10 of the 6390X family have configurable
PHY modes. Set the mode as part of adjust_link().

Ordering is important, because the SERDES interfaces connected to
ports 9 and 10 can be split and assigned to other ports. The CMODE has
to be correctly set before the SERDES interface on another port can be
configured. Such configuration is likely to be performed in
port_enable() and port_disabled(), called on slave_open() and
slave_close().

The simple case is port 9 and 10 are used for 'CPU' or 'DSA'. In this
case, the CMODE is set via a phy-mode in dsa_cpu_dsa_setup(), which is
called early in the switch setup.

When ports 9 or 10 are used as user ports, and have a fixed-phy, when
the fixed fixed-phy is attached, dsa_slave_adjust_link() is called,
which results in the adjust_link function being called, setting the
cmode. The port_enable() will for other ports will be called much
later.

When ports 9 or 10 are used as user ports and have a real phy attached
which does not use all the available SERDES interface, e.g. a 1Gbps
SGMII, there is currently no mechanism in place to set the CMODE of
the port from software. It must be hoped the stripping resistors are
correct.

At the same time, add a function to get the cmode. This will be needed
when configuring the SERDES interfaces.
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
Reviewed-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The mv88e6390 ports 9 and 10 supports some additional PHY modes. Add
these modes to the PHY core so they can be used in the binding.
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
Reviewed-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

John Fastabend says:

====================
XDP adjust head support for virtio

This series adds adjust head support for virtio. The following is my
test setup. I use qemu + virtio as follows,

./x86_64-softmmu/qemu-system-x86_64 \
  -hda /var/lib/libvirt/images/Fedora-test0.img \
  -m 4096  -enable-kvm -smp 2 -netdev tap,id=hn0,queues=4,vhost=on \
  -device virtio-net-pci,netdev=hn0,mq=on,guest_tso4=off,guest_tso6=off,guest_ecn=off,guest_ufo=off,vectors=9

In order to use XDP with virtio until LRO is supported TSO must be
turned off in the host. The important fields in the above command line
are the following,

  guest_tso4=off,guest_tso6=off,guest_ecn=off,guest_ufo=off

Also note it is possible to conusme more queues than can be supported
because when XDP is enabled for retransmit XDP attempts to use a queue
per cpu. My standard queue count is 'queues=4'.

After loading the VM I run the relevant XDP test programs in,

  ./sammples/bpf

For this series I tested xdp1, xdp2, and xdp_tx_iptunnel. I usually test
with iperf (-d option to get bidirectional traffic), ping, and pktgen.
I also have a modified xdp1 that returns XDP_PASS on any packet to ensure
the normal traffic path to the stack continues to work with XDP loaded.

It would be great to automate this soon. At the moment I do it by hand
which is starting to get tedious.

v2: original series dropped trace points after merge.
====================
Acked-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add support for XDP adjust head by allocating a 256B header region
that XDP programs can grow into. This is only enabled when a XDP
program is loaded.

In order to ensure that we do not have to unwind queue headroom push
queue setup below bpf_prog_add. It reads better to do a prog ref
unwind vs another queue setup call.

At the moment this code must do a full reset to ensure old buffers
without headroom on program add or with headroom on program removal
are not used incorrectly in the datapath. Ideally we would only
have to disable/enable the RX queues being updated but there is no
API to do this at the moment in virtio so use the big hammer. In
practice it is likely not that big of a problem as this will only
happen when XDP is enabled/disabled changing programs does not
require the reset. There is some risk that the driver may either
have an allocation failure or for some reason fail to correctly
negotiate with the underlying backend in this case the driver will
be left uninitialized. I have not seen this ever happen on my test
systems and for what its worth this same failure case can occur
from probe and other contexts in virtio framework.
Signed-off-by: NJohn Fastabend <john.r.fastabend@intel.com>
Acked-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

For XDP we will need to reset the queues to allow for buffer headroom
to be configured. In order to do this we need to essentially run the
freeze()/restore() code path. Unfortunately the locking requirements
between the freeze/restore and reset paths are different however so
we can not simply reuse the code.

This patch refactors the code path and adds a reset helper routine.
Signed-off-by: NJohn Fastabend <john.r.fastabend@intel.com>
Acked-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Factor out qp assignment.
Signed-off-by: NJohn Fastabend <john.r.fastabend@intel.com>
Acked-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

At this point the do_xdp_prog is mostly if/else branches handling
the different modes of virtio_net. So remove it and handle running
the program in the per mode handlers.
Signed-off-by: NJohn Fastabend <john.r.fastabend@intel.com>
Acked-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

For XDP use case and to allow ethtool reset tests it is useful to be
able to use reset paths from contexts where rtnl lock is already
held.

This requries updating virtnet_set_queues and free_receive_bufs the
two places where rtnl_lock is taken in virtio_net. To do this we
use the following pattern,

	_foo(...) { do stuff }
	foo(...) { rtnl_lock(); _foo(...); rtnl_unlock()};

this allows us to use freeze()/restore() flow from both contexts.
Signed-off-by: NJohn Fastabend <john.r.fastabend@intel.com>
Acked-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Nikolay Aleksandrov says:

====================
bridge: improve cache utilization

This is the first set which begins to deal with the bad bridge cache
access patterns. The first patch rearranges the bridge and port structs
a little so the frequently (and closely) accessed members are in the same
cache line. The second patch then moves the garbage collection to a
workqueue trying to improve system responsiveness under load (many fdbs)
and more importantly removes the need to check if the matched entry is
expired in __br_fdb_get which was a major source of false-sharing.
The third patch is a preparation for the final one which
If properly configured, i.e. ports bound to CPUs (thus updating "updated"
locally) then the bridge's HitM goes from 100% to 0%, but even without
binding we get a win because previously every lookup that iterated over
the hash chain caused false-sharing due to the first cache line being
used for both mac/vid and used/updated fields.

Some results from tests I've run:
(note that these were run in good conditions for the baseline, everything
 ran on a single NUMA node and there were only 3 fdbs)

1. baseline
100% Load HitM on the fdbs (between everyone who has done lookups and hit
                            one of the 3 hash chains of the communicating
                            src/dst fdbs)
Overall 5.06% Load HitM for the bridge, first place in the list

2. patched & ports bound to CPUs
0% Local load HitM, bridge is not even in the c2c report list
Also there's 3% consistent improvement in netperf tests.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Writing once per jiffy is enough to limit the bridge's false sharing.
After this change the bridge doesn't show up in the local load HitM stats.
Suggested-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Fdb's used and updated fields are written to on every packet forward and
packet receive respectively. Thus if we are receiving packets from a
particular fdb, they'll cause false-sharing with everyone who has looked
it up (even if it didn't match, since mac/vid share cache line!). The
"used" field is even worse since it is updated on every packet forward
to that fdb, thus the standard config where X ports use a single gateway
results in 100% fdb false-sharing. Note that this patch does not prevent
the last scenario, but it makes it better for other bridge participants
which are not using that fdb (and are only doing lookups over it).
The point is with this move we make sure that only communicating parties
get the false-sharing, in a later patch we'll show how to avoid that too.
Signed-off-by: NNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Move the fdb garbage collector to a workqueue which fires at least 10
milliseconds apart and cleans chain by chain allowing for other tasks
to run in the meantime. When having thousands of fdbs the system is much
more responsive. Most importantly remove the need to check if the
matched entry has expired in __br_fdb_get that causes false-sharing and
is completely unnecessary if we cleanup entries, at worst we'll get 10ms
of traffic for that entry before it gets deleted.
Signed-off-by: NNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Move around net_bridge so the vlan fields are in the beginning since
they're checked on every packet even if vlan filtering is disabled.
For the port move flags & vlan group to the beginning, so they're in the
same cache line with the port's state (both flags and state are checked
on each packet).
Signed-off-by: NNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The patch fixes the case when adding a zero value to the packet
pointer.  The zero value could come from src_reg equals type
BPF_K or CONST_IMM.  The patch fixes both, otherwise the verifer
reports the following error:
  [...]
    R0=imm0,min_value=0,max_value=0
    R1=pkt(id=0,off=0,r=4)
    R2=pkt_end R3=fp-12
    R4=imm4,min_value=4,max_value=4
    R5=pkt(id=0,off=4,r=4)
  269: (bf) r2 = r0     // r2 becomes imm0
  270: (77) r2 >>= 3
  271: (bf) r4 = r1     // r4 becomes pkt ptr
  272: (0f) r4 += r2    // r4 += 0
  addition of negative constant to packet pointer is not allowed
Signed-off-by: NWilliam Tu <u9012063@gmail.com>
Signed-off-by: NMihai Budiu <mbudiu@vmware.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Acked-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

These two tests are based on the work done for f23cc643.  The first test is
just a basic one to make sure we don't allow AND'ing negative values, even if it
would result in a valid index for the array.  The second is a cleaned up version
of the original testcase provided by Jann Horn that resulted in the commit.
Acked-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: NJosef Bacik <jbacik@fb.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Vivien Didelot says:

====================
net: dsa: add fabric notifier

When a switch fabric is composed of multiple switch chips, these chips
must be programmed accordingly when an event occurred on one of them.

Examples of such event include hardware bridging: when a Linux bridge
spans interconnected chips, they must be programmed to allow external
ports to ingress frames on their internal ports.

Another example is cross-chip hardware VLANs. Switch chips in-between
interconnected bridge ports must also configure a given VLAN to allow
packets to pass through them.

In order to support that, this patchset introduces a non-intrusive
notifier mechanism. It adds a notifier head in every DSA switch tree
(the said fabric), and a notifier block in every DSA switch chip.

When an even occurs, it is chained to all notifiers of the fabric.
Switch chips can react accordingly if they are cross-chip capable.

On a dynamic debug enabled system, bridging a port in a multi-chip
fabric will print something like this (ZII Rev B board):

    # brctl addif br0 lan3
    mv88e6085 0.1:00: crosschip DSA port 1.0 bridged to br0
    mv88e6085 0.4:00: crosschip DSA port 1.0 bridged to br0
    # brctl delif br0 lan3
    mv88e6085 0.1:00: crosschip DSA port 1.0 unbridged from br0
    mv88e6085 0.4:00: crosschip DSA port 1.0 unbridged from br0

Currently only bridging events are added. A patchset introducing support
for cross-chip hardware bridging configuration in mv88e6xxx will follow
right after. Then events for switchdev operations are next on the line.

We should note that non-switchdev events do not support rolling-back
switch-wide operations. We'll have to work on closer integration with
switchdev for that, like introducing new attributes or objects, to
benefit from the prepare and commit phases.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

A slave device will now notify the switch fabric once its port is
bridged or unbridged, instead of calling directly its switch operations.

This code allows propagating cross-chip bridging events in the fabric.
Signed-off-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add a notifier block per DSA switch, registered against a notifier head
in the switch fabric they belong to.

This infrastructure will allow to propagate fabric-wide events such as
port bridging, VLAN configuration, etc. If a DSA switch driver cares
about cross-chip configuration, such events can be caught.
Signed-off-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The scope of the functions inside net/dsa/slave.c must be the slave
net_device pointer. Change to state setter helper accordingly to
simplify callers.
Signed-off-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

When an error is returned during the bridging of a port in a
NETDEV_CHANGEUPPER event, net/core/dev.c rolls back the operation.

Be consistent and unassign dp->bridge_dev when this happens.

In the meantime, add comments to document this behavior.
Signed-off-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Simplify the code handling the slave netdevice notifier call by
providing a dsa_slave_changeupper helper for NETDEV_CHANGEUPPER, and so
on (only this event is supported at the moment.)

Return NOTIFY_DONE when we did not care about an event, and NOTIFY_OK
when we were concerned but no error occurred, as the API suggests.
Signed-off-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Move the netdevice notifier block register code in slave.c and provide
helpers for dsa.c to register and unregister it.

At the same time, check for errors since (un)register_netdevice_notifier
may fail.
Signed-off-by: NVivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>