In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Karsten Keil <isdn@linux-pingi.de>
Cc: Geliang Tang <geliangtang@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Anton Vasilyev <vasilyev@ispras.ru>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Zhu Yanjun <yanjun.zhu@oracle.com>
Cc: Philippe Reynes <tremyfr@gmail.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Johannes Berg <johannes.berg@intel.com>
Cc: Jarod Wilson <jarod@redhat.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Philippe Reynes <tremyfr@gmail.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jarod Wilson <jarod@redhat.com>
Cc: Tobias Klauser <tklauser@distanz.ch>
Cc: Philippe Reynes <tremyfr@gmail.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Rasesh Mody <rasesh.mody@cavium.com>
Cc: Sudarsana Kalluru <sudarsana.kalluru@cavium.com>
Cc: Dept-GELinuxNICDev@cavium.com
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jarod Wilson <jarod@redhat.com>
Cc: Philippe Reynes <tremyfr@gmail.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Johannes Berg <johannes.berg@intel.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Steffen Klassert <klassert@mathematik.tu-chemnitz.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jarod Wilson <jarod@redhat.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Oliver Hartkopp <socketcan@hartkopp.net>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: linux-can@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: David Howells <dhowells@redhat.com>
Cc: Jarod Wilson <jarod@redhat.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Johannes Berg <johannes.berg@intel.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Philippe Reynes <tremyfr@gmail.com>
Cc: "yuval.shaia@oracle.com" <yuval.shaia@oracle.com>
Cc: netdev@vger.kernel.org
Cc: linux-parisc@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly. This required adding a pointer back
to vc_map, and adjusting the locking around removal a bit.

Cc: Chas Williams <3chas3@gmail.com>
Cc: linux-atm-general@lists.sourceforge.net
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly. Passes NULL timer when doing non-
timer call.

Cc: Chas Williams <3chas3@gmail.com>
Cc: linux-atm-general@lists.sourceforge.net
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Jon Mason <jdmason@kudzu.us>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Cc: Jarod Wilson <jarod@redhat.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: stephen hemminger <stephen@networkplumber.org>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Solomon Peachy <pizza@shaftnet.org>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linux-pcmcia@lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: "yuval.shaia@oracle.com" <yuval.shaia@oracle.com>
Cc: Tobias Klauser <tklauser@distanz.ch>
Cc: Jarod Wilson <jarod@redhat.com>
Cc: Philippe Reynes <tremyfr@gmail.com>
Cc: netdev@vger.kernel.org
Cc: linux-parisc@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
helper to pass the timer pointer explicitly.

Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: bcm-kernel-feedback-list@broadcom.com
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Jarod Wilson <jarod@redhat.com>
Cc: netdev@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
helper to pass the timer pointer explicitly.

Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Andreas Koensgen <ajk@comnets.uni-bremen.de>
Cc: linux-hams@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Karsten Keil <isdn@linux-pingi.de>
Cc: Geliang Tang <geliangtang@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly. Since the callback is called from
both a timer and a tasklet, adjust the tasklet to pass the timer address
too. When tasklets have their .data field removed, this can be refactored
to call a central function after resolving the correct container_of() for a
separate callback function for timer and tasklet.

Cc: Oliver Neukum <oneukum@suse.com>
Cc: netdev@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Samuel Chessman <chessman@tux.org>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: linux-hams@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Hans Liljestrand <ishkamiel@gmail.com>
Cc: "Reshetova, Elena" <elena.reshetova@intel.com>
Cc: linux-x25@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

In preparation for unconditionally passing the struct timer_list pointer to
all timer callbacks, switch to using the new timer_setup() and from_timer()
to pass the timer pointer explicitly.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Johannes Berg <johannes.berg@intel.com>
Cc: David Ahern <dsa@cumulusnetworks.com>
Cc: linux-decnet-user@lists.sourceforge.net
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Vivien Didelot says:

====================
net: dsa: master and slave helpers

This patch series adds a few helpers to DSA core for clarity and
readability but brings no functional changes.

A dsa_slave_notify helper calls the DSA notifiers when (un)registering a
slave device.

Most of the DSA slave code only needs to access the dsa_port structure,
not the dsa_slave_priv (which only contains a few PHY-specific members).
Thus a dsa_slave_to_port helper returns a dsa_port structure of a slave
device.

A dsa_slave_to_master returns the master device of a slave device.

After that the netdev member of the dsa_port structure is split into two
explicit master and slave members to avoid confusion, and a dsa_to_port
helper is added for switch drivers to get a const reference to a port.

Changes in v2:
  - prefer dsa_slave_to_master instead of dsa_slave_get_master
  - rename dsa_master_get_slave to dsa_master_find_slave
  - pack master and slave net devices into an anonymous union
  - add dsa_to_port public helper for switch drivers
  - add Reviewed-by tags from Florian
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

The dsa_port structure is part of DSA core data and must only be updated
by the later. It is OK and sometimes necessary for the DSA drivers to
access this data, but this has to be read only.

For that purpose, add a dsa_to_port() helper which returns a const
pointer to a dsa_port structure which must be used by DSA drivers from
now on instead of digging into ds->ports[] themselves.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The dsa_port structure has a "netdev" member, which can be used for
either the master device, or the slave device, depending on its type.

It is true that today, CPU port are not exposed to userspace, thus the
port's netdev member can be used to point to its master interface.

But it is still slightly confusing, so split it into more explicit
"master" and "slave" members inside an anonymous union.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The dsa_master_get_slave is slightly confusing since the idiomatic "get"
term often suggests reference counting, in symmetry to "put".

Rename it to dsa_master_find_slave to make the look up operation clear.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Many part of the DSA slave code require to get the master device
assigned to a slave device. Remove dsa_master_netdev() in favor of a
dsa_slave_to_master() helper which does that.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Many portions of DSA core code require to get the dsa_port structure
corresponding to a slave net_device. For this purpose, introduce a
dsa_slave_to_port() helper.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Both DSA slave create and destroy functions call call_dsa_notifiers with
respectively DSA_PORT_REGISTER and DSA_PORT_UNREGISTER and the same
dsa_notifier_register_info structure.

Wrap this in a dsa_slave_notify helper so prevent cluttering these
functions.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

When dsa_slave_create is called, the related port already has a CPU port
assigned to it, available in its cpu_dp member. Use it instead of the
unique tree cpu_dp.
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

When netlink_ack() reports an allocation error to the sending
socket, there's no need to look up the sending socket since
it's available in the SKB's CB. Use that instead of going to
the trouble of looking it up.

Note that the pointer is only available since Eric Biederman's
commit 3fbc2905 ("netlink: Make the sending netlink socket availabe in NETLINK_CB")
which is far newer than the original lookup code (Oct 2003)
(though the field was called 'ssk' in that commit and only got
renamed to 'sk' later, I'd actually argue 'ssk' was better - or
perhaps it should've been 'source_sk' - since there are so many
different 'sk's involved.)
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Jesper Dangaard Brouer says:

====================
net: New bpf cpumap type for XDP_REDIRECT

Introducing a new way to redirect XDP frames.  Notice how no driver
changes are necessary given the design of XDP_REDIRECT.

This redirect map type is called 'cpumap', as it allows redirection
XDP frames to remote CPUs.  The remote CPU will do the SKB allocation
and start the network stack invocation on that CPU.

This is a scalability and isolation mechanism, that allow separating
the early driver network XDP layer, from the rest of the netstack, and
assigning dedicated CPUs for this stage.  The sysadm control/configure
the RX-CPU to NIC-RX queue (as usual) via procfs smp_affinity and how
many queues are configured via ethtool --set-channels.  Benchmarks
show that a single CPU can handle approx 11Mpps.  Thus, only assigning
two NIC RX-queues (and two CPUs) is sufficient for handling 10Gbit/s
wirespeed smallest packet 14.88Mpps.  Reducing the number of queues
have the advantage that more packets being "bulk" available per hard
interrupt[1].

[1] https://www.netdevconf.org/2.1/papers/BusyPollingNextGen.pdf

Use-cases:

1. End-host based pre-filtering for DDoS mitigation.  This is fast
   enough to allow software to see and filter all packets wirespeed.
   Thus, no packets getting silently dropped by hardware.

2. Given NIC HW unevenly distributes packets across RX queue, this
   mechanism can be used for redistribution load across CPUs.  This
   usually happens when HW is unaware of a new protocol.  This
   resembles RPS (Receive Packet Steering), just faster, but with more
   responsibility placed on the BPF program for correct steering.

3. Auto-scaling or power saving via only activating the appropriate
   number of remote CPUs for handling the current load.  The cpumap
   tracepoints can function as a feedback loop for this purpose.

In V7, a --stress-mode was implemented for the samples program, which
between each stats update, adds + removes CPUs from the map
concurrently with traffic.  I did find and fix some concurrency issues
in the tear-down path, details in patch desc.  The stress test have
now been running for 15 hours without any issues, while being
bombarded with 11.6 Mpps via pktgen_sample04_many_flows.sh.

See individual patches for patchset-version changes.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

This sample program show how to use cpumap and the associated
tracepoints.

It provides command line stats, which shows how the XDP-RX process,
cpumap-enqueue and cpumap kthread dequeue is cooperating on a per CPU
basis.  It also utilize the xdp_exception and xdp_redirect_err
transpoints to allow users quickly to identify setup issues.

One issue with ixgbe driver is that the driver reset the link when
loading XDP.  This reset the procfs smp_affinity settings.  Thus,
after loading the program, these must be reconfigured.  The easiest
workaround it to reduce the RX-queue to e.g. two via:

 # ethtool --set-channels ixgbe1 combined 2

And then add CPUs above 0 and 1, like:

 # xdp_redirect_cpu --dev ixgbe1 --prog 2 --cpu 2 --cpu 3 --cpu 4

Another issue with ixgbe is that the page recycle mechanism is tied to
the RX-ring size.  And the default setting of 512 elements is too
small.  This is the same issue with regular devmap XDP_REDIRECT.
To overcome this I've been using 1024 rx-ring size:

 # ethtool -G ixgbe1 rx 1024 tx 1024

V3:
 - whitespace cleanups
 - bpf tracepoint cannot access top part of struct

V4:
 - report on kthread sched events, according to tracepoint change
 - report average bulk enqueue size

V5:
 - bpf_map_lookup_elem on cpumap not allowed from bpf_prog
   use separate map to mark CPUs not available

V6:
 - correct kthread sched summary output

V7:
 - Added a --stress-mode for concurrently changing underlying cpumap
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This adds two tracepoint to the cpumap.  One for the enqueue side
trace_xdp_cpumap_enqueue() and one for the kthread dequeue side
trace_xdp_cpumap_kthread().

To mitigate the tracepoint overhead, these are invoked during the
enqueue/dequeue bulking phases, thus amortizing the cost.

The obvious use-cases are for debugging and monitoring.  The
non-intuitive use-case is using these as a feedback loop to know the
system load.  One can imagine auto-scaling by reducing, adding or
activating more worker CPUs on demand.

V4: tracepoint remove time_limit info, instead add sched info

V8: intro struct bpf_cpu_map_entry members cpu+map_id in this patch
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch makes cpumap functional, by adding SKB allocation and
invoking the network stack on the dequeuing CPU.

For constructing the SKB on the remote CPU, the xdp_buff in converted
into a struct xdp_pkt, and it mapped into the top headroom of the
packet, to avoid allocating separate mem.  For now, struct xdp_pkt is
just a cpumap internal data structure, with info carried between
enqueue to dequeue.

If a driver doesn't have enough headroom it is simply dropped, with
return code -EOVERFLOW.  This will be picked up the xdp tracepoint
infrastructure, to allow users to catch this.

V2: take into account xdp->data_meta

V4:
 - Drop busypoll tricks, keeping it more simple.
 - Skip RPS and Generic-XDP-recursive-reinjection, suggested by Alexei

V5: correct RCU read protection around __netif_receive_skb_core.

V6: Setting TASK_RUNNING vs TASK_INTERRUPTIBLE based on talk with Rik van Riel
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>