We introduce a new hashing library that is meant to be used in
the contexts where speed is more important than uniformity of the
hashed values. The hash library leverages architecture specific
implementation to achieve high performance and fall backs to
jhash() for the generic case.

On Intel-based x86 architectures, the library can exploit the crc32l
instruction, part of the Intel SSE4.2 instruction set, if the
instruction is supported by the processor. This implementation
is twice as fast as the jhash() implementation on an i7 processor.

Additional architectures, such as Arm64 provide instructions for
accelerating the computation of CRC, so they could be added as well
in follow-up work.
Signed-off-by: NFrancesco Fusco <ffusco@redhat.com>
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: NThomas Graf <tgraf@redhat.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Use "unsigned int/short" instead of "unsigned", and change the type of
iteration variable "i" to "unsigned int".
Signed-off-by: NTan Xiaojun <tanxiaojun@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Instead of reaquiring the socket lock and taking the normal exit
path when a connection times out, we bail out early with a
return -ETIMEDOUT.
Reviewed-by: NJon Maloy <jon.maloy@ericsson.com>
Reviewed-by: NErik Hugne <erik.hugne@ericsson.com>
Signed-off-by: NWang Weidong <wangweidong1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

As warned by checkpatch.pl, use #include <linux/uaccess.h>
instead of <asm/uaccess.h>
Reviewed-by: NJon Maloy <jon.maloy@ericsson.com>
Reviewed-by: NErik Hugne <erik.hugne@ericsson.com>
Signed-off-by: NWang Weidong <wangweidong1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Remove a number of needless 'goto exit' in send_stream
when the socket is in an unconnected state.
This patch is cosmetic and does not alter the operation of
TIPC in any way.
Reviewed-by: NJon Maloy <jon.maloy@ericsson.com>
Reviewed-by: NErik Hugne <erik.hugne@ericsson.com>
Signed-off-by: NWang Weidong <wangweidong1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

We remove a number of unnecessary variables and branches
in TIPC. This patch is cosmetic and does not change the
operation of TIPC in any way.
Reviewed-by: NJon Maloy <jon.maloy@ericsson.com>
Reviewed-by: NErik Hugne <erik.hugne@ericsson.com>
Signed-off-by: NWang Weidong <wangweidong1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

It was reported that Commit 299603e8
("net-gro: Prepare GRO stack for the upcoming tunneling support")
triggered a compiler warning in ipv6_exthdrs_len():

net/ipv6/ip6_offload.c: In function ‘ipv6_gro_complete’:
net/ipv6/ip6_offload.c:178:24: warning: ‘optlen’ may be used uninitialized in this function [-Wmaybe-u
    opth = (void *)opth + optlen;
    			^
    net/ipv6/ip6_offload.c:164:22: note: ‘optlen’ was declared here
    int len = 0, proto, optlen;
                        ^
Note that there was no real bug here - optlen was never uninitialized
before use. (Was the version of gcc I used smarter to not complain?)
Reported-by: NHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: NH.K. Jerry Chu <hkchu@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Ben Hutchings says:

====================
1. Change PTP clock name to 'sfc'.
2. Complete support for hardware timestamping and PTP clock on the
SFC9100 family.
3. Various cleanups for the PTP code.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Commit 299603e8 ("net-gro: Prepare GRO
stack for the upcoming tunneling support") used an uninitialized variable
which leads to the following compiler warning:

net/ipv6/ip6_offload.c: In function ‘ipv6_gro_complete’:
net/ipv6/ip6_offload.c:178:24: warning: ‘optlen’ may be used uninitialized in this function [-Wmaybe-uninitialized]
    opth = (void *)opth + optlen;
                        ^
net/ipv6/ip6_offload.c:164:22: note: ‘optlen’ was declared here
  int len = 0, proto, optlen;
                      ^
Fix it up.

Cc: Jerry Chu <hkchu@google.com>
Signed-off-by: NHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Ding Tianhong says:

====================
bonding: rebuild the lock use for bond monitor

Now the bond slave list is not protected by bond lock, only by RTNL,
but the monitor still use the bond lock to protect the slave list,
it is useless, according to the Veaceslav's opinion, there were
three way to fix the protect problem:

1. add bond_master_upper_dev_link() and bond_upper_dev_unlink()
   in bond->lock, but it is unsafe to call call_netdevice_notifiers()
   in write lock.
2. remove unused bond->lock for monitor function, only use the exist
   rtnl lock(), it will take performance loss in fast path.
3. use RCU to protect the slave list, of course, performance is better,
   but in slow path, it is ignored.

obviously the solution 1 is not fit here, I will consider the 2 and 3
solution. My principle is simple, if in fast path, RCU is better,
otherwise in slow path, both is well, but according to the Jay Vosburgh's
opinion, the monitor will loss performace if use RTNL to protect the all
slave list, so remove the bond lock and replace with RCU.

The second problem is the curr_slave_lock for bond, it is too old and
unwanted in many place, because the curr_active_slave would only be
changed in 3 place:

1. enslave slave.
2. release slave.
3. change active slave.

all above were already holding bond lock, RTNL and curr_slave_lock
together, it is tedious and no need to add so mach lock, when change
the curr_active_slave, you have to hold the RTNL and curr_slave_lock
together, and when you read the curr_active_slave, RTNL or curr_slave_lock,
any one of them is no problem.

for the stability, I did not change the logic for the monitor,
all change is clear and simple, I have test the patch set for lockdep,
it work well and stability.

v2. accept the Jay Vosburgh's opinion, remove the RTNL and replace with RCU,
    also add some rcu function for bond use, so the patch set reach 10.

v3. accept the Nikolay Aleksandrov's opinion, remove no needed bond_has_slave_rcu(),
    add protection for several 3ad mode handler functions and current_arp_slave.
    rebuild the bond_first_slave_rcu(), make it more clear.

v4. because the struct netdev_adjacent should not be exist in netdevice.h, so I have
    to make a new function to support micro bond_first_slave_rcu().
    also add a new patch to simplify the bond_resend_igmp_join_requests_delayed().

v5. according the Jay Vosburgh's opinion, in patch 2 and 6, the calling of notify
    peer is hardly to happen with the bond_xxx_commit() when the monitoring is running,
    so the performance impact about make two round trips to one trip on RTNL is minimal,
    no need to do that,the reason is very clear, so modify the patch 2 and 6, recover
    the notify peer in RTNL alone.
====================
Signed-off-by: NJay Vosburgh <fubar@us.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The bond_resend_igmp_join_requests_delayed() and
bond_resend_igmp_join_requests() should be integrated,
because the bond_resend_igmp_join_requests_delayed() did
nothing except bond_resend_igmp_join_requests().

The bond igmp_retrans could only be changed in bond_change_active_slave
and here, bond_change_active_slave will be called in RTNL and curr_slave_lock,
the bond_resend_igmp_join_requests already hold RTNL, so no need
to free RTNL and hold curr_slave_lock again, it may be a small optimization,
so move the igmp_retrans in RTNL and remove the curr_slave_lock.
Signed-off-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The bond_select_active_slave() will not release and acquire
bond lock, so it is no need to read the bond lock for them,
and the bond_store_primaryxxx() is already in RTNL, so remove the
unwanted lock.
Suggested-by: NJay Vosburgh <fubar@us.ibm.com>
Suggested-by: NVeaceslav Falico <vfalico@redhat.com>
Signed-off-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The bond_option_active_slave_set() is always called in RTNL,
the RTNL could protect bond slave list, so remove the unwanted
bond lock.
Suggested-by: NJay Vosburgh <fubar@us.ibm.com>
Suggested-by: NVeaceslav Falico <vfalico@redhat.com>
Signed-off-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The bond_3ad_state_machine_handler() use the bond lock to protect
the bond slave list and slave port together, but it is not enough,
the bond slave list was link and unlink in RTNL, not bond lock,
so I add RCU to protect the slave list from leaving.

The bond lock is still used here, because when the slave has been
removed from the list by the time the state machine runs, it appears
to be possible for both function to manupulate the same aggregator->lag_ports
by finding the aggregator via two different ports that are both members of
that aggregator (i.e., port A of the agg is being unbound, and port B
of the agg is runing its state machine).

If I remove the bond lock, there are nothing to mutex changes
to aggregator->lag_ports between bond_3ad_state_machine_handler and
bond_3ad_unbind_slave, So the bond lock is the simplest way to protect
aggregator->lag_ports.

There was a lot of function need RCU protect, I have two choice
to make the function in RCU-safe, (1) create new similar functions
and make the bond slave list in RCU. (2) modify the existed functions
and make them in read-side critical section, because the RCU
read-side critical sections may be nested.

I choose (2) because it is no need to create more similar functions.

The nots in the function is still too old, clean up the nots.
Suggested-by: NNikolay Aleksandrov <nikolay@redhat.com>
Suggested-by: NJay Vosburgh <fubar@us.ibm.com>
Suggested-by: NVeaceslav Falico <vfalico@redhat.com>
Signed-off-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The bond_change_active_slave() and bond_select_active_slave()
do't need bond lock anymore, so remove the unwanted bond lock
for these two functions.

The bond_select_active_slave() will release and acquire
curr_slave_lock, so the curr_slave_lock need to protect
the function.

In bond enslave and bond release, the bond slave list is also
protected by RTNL, so bond lock is no need to exist, remove
the lock and clean the functions.
Suggested-by: NJay Vosburgh <fubar@us.ibm.com>
Suggested-by: NVeaceslav Falico <vfalico@redhat.com>
Signed-off-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The bond_activebackup_arp_mon() use the bond lock for read to
protect the slave list, it is no effect, and the RTNL is only
called for bond_ab_arp_commit() and peer notify, for the performance
better, use RCU to replace with the bond lock, to the bond slave
list need to called in RCU, add a new bond_first_slave_rcu()
to get the first slave in RCU protection.

In bond_ab_arp_probe(), the bond->current_arp_slave may changd
if bond release slave, just like:

        bond_ab_arp_probe()                     bond_release()
        cpu 0                                   cpu 1
        ...
        if (bond->current_arp_slave...)         ...
        ...                             bond->current_arp_slave = NULl
        bond->current_arp_slave->dev->name      ...

So the current_arp_slave need to dereference in the section.
Suggested-by: NNikolay Aleksandrov <nikolay@redhat.com>
Suggested-by: NJay Vosburgh <fubar@us.ibm.com>
Suggested-by: NVeaceslav Falico <vfalico@redhat.com>
Signed-off-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The bond_first_slave_rcu() will be used to instead of bond_first_slave()
in rcu_read_lock().

According to the Jay Vosburgh's suggestion, the struct netdev_adjacent
should hide from users who wanted to use it directly. so I package a
new function to get the first slave of the bond.
Suggested-by: NNikolay Aleksandrov <nikolay@redhat.com>
Suggested-by: NJay Vosburgh <fubar@us.ibm.com>
Suggested-by: NVeaceslav Falico <vfalico@redhat.com>
Signed-off-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The bond_loadbalance_arp_mon() use the bond lock to protect the
bond slave list, it is no effect, so I could use RTNL or RCU to
replace it, considering the performance impact, the RCU is more
better here, so the bond lock replace with the RCU.

The bond_select_active_slave() need RTNL and curr_slave_lock
together, but there is no RTNL lock here, so add a rtnl_rtylock.
Suggested-by: NJay Vosburgh <fubar@us.ibm.com>
Suggested-by: NVeaceslav Falico <vfalico@redhat.com>
Signed-off-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The bond_alb_monitor use bond lock to protect the bond slave list,
it is no effect here, we need to use RTNL or RCU to replace bond lock,
the bond_alb_monitor will called 10 times one second, RTNL may loss
performance here, so I replace bond lock with RCU to protect the
bond slave list, also the RTNL is preserved, the logic of the monitor
did not changed.
Suggested-by: NNikolay Aleksandrov <nikolay@redhat.com>
Suggested-by: NJay Vosburgh <fubar@us.ibm.com>
Suggested-by: NVeaceslav Falico <vfalico@redhat.com>
Signed-off-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The bond_mii_monitor() still use bond lock to protect bond slave list,
it is no effect, I have 2 way to fix the problem, move the RTNL to the
top of the function, or add RCU to protect the bond slave list,
according to the Jay Vosburgh's opinion, 10 times one second is a
truely big performance loss if use RTNL to protect the whole monitor,
so I would take the advice and use RCU to protect the bond slave list.

The bond_has_slave() will not protect by anything, there will no things
happen if the slave list is be changed, unless the bond was free, but
it will not happened before the monitor, the bond will closed before
be freed.

The peers notify for the bond will calling curr_active_slave, so
derefence the slave to make sure we will accessing the same slave
if the curr_active_slave changed, as the rcu dereference need in
read-side critical sector and bond_change_active_slave() will call
it with no RCU hold,  so add peer notify in rcu_read_lock which
will be nested in monitor.
Suggested-by: NJay Vosburgh <fubar@us.ibm.com>
Suggested-by: NVeaceslav Falico <vfalico@redhat.com>
Signed-off-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The bond slave list was no longer protected by bond lock and only
protected by RTNL or RCU, so anywhere that use bond lock to protect
slave list is meaningless.

remove the release and acquire bond lock for bond_select_active_slave().

The curr_active_slave could only be changed in 3 place:

1. enslave slave.
2. release slave.
3. change_active_slave.

all above place were holding bond lock, RTNL and curr_slave_lock
together, it is tedious and meaningless, obviously bond lock is no
need here, but RTNL or curr_slave_lock is needed, so if you want
to access active slave, you have to choose one lock, RTNL or
curr_slave_lock, if RTNL is exist, no need to add curr_slave_lock,
otherwise curr_slave_lock is better, because of the performance.

there are several place calling bond_select_active_slave() and
bond_change_active_slave(), the next step I will clean these place
and remove the no effect lock.

there are some document changed together when update the function.
Suggested-by: NJay Vosburgh <fubar@us.ibm.com>
Suggested-by: NVeaceslav Falico <vfalico@redhat.com>
Signed-off-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

After commit 95dc1929 ("pkt_sched: give visibility to mq slave
qdiscs") we call disc_list_add() while the device qdisc might be
the noop_qdisc one.

This shows up as duplicates in "tc qdisc show", as all inactive devices
point to noop_qdisc.

Fix this by setting dev->qdisc to the new qdisc before calling
ops->change() in attach_default_qdiscs()

Add a WARN_ON_ONCE() to catch any future similar problem.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Ben Hutchings says:

====================
An assortment of changes for Linux 3.14:

1. Merge the sfc fixes that you have already merged into net.git.
   (The branch point for those was such that this does not bring in any
   other changes.)
2. Reduce log level for a generally useless warning message, from
   Robert Stonehouse.
3. Include BISTs in ethtool offline self-test for EF10 and recover from
   BISTs initiated through other functions, from Jon Cooper.
4. Improve a sanity check on RX completions.
5. Avoid incrementing RX dropped count while the interface is down, from
   Jon Cooper.
6. Improve hardware sensor naming and log messages, from Edward Cree.
7. Log all unexpected errors returned by firmware, from Edward Cree.
8. Expose another NVRAM partition to userland.
9. Some refactoring of the PTP code in preparation for EF10 support.
10. Various minor cleanups.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Scott Feldman says:

====================
bonding: add more netlink attributes

v2:

Addressed v1 review comments.  In particular, Jay's concern about
current sysfs ordering limitations carrying over to iproute.  Netlink
attributes are processed in a priority order in
bond_netlink.c:bond_changelink().  Lower priority attributes can't undo
higher priority attributes when attempting to set both with iproute
command.  For example, this command will fail:

  ip link add bond1 type bond mode active-backup miimon 10 arp_interval 10

Because we're trying to create a new bond to use incompatible miimon
and ARP interval attributes.  However, if attributes are applied
one-at-a-time, previously applied attributes can be overridden:

  ip link add bond1 type bond mode active-backup miimon 10
  ip link set dev bond1 type bond arp_interval 10

These two commands succeed.  The bond is first created to use miimon.
Next, the bond is converted to use ARP interval, which undoes miimon.

v1:

Following Jiri Pirko's lead, add more bonding netlink attributes.  Sending
matching iproute2 patch separately.  sysfs access to attributes is
retained.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add IFLA_BOND_ARP_ALL_TARGETS to allow get/set of bonding parameter
arp_all_targets via netlink.
Signed-off-by: NScott Feldman <sfeldma@cumulusnetworks.com>
Signed-off-by: NJiri Pirko <jiri@resnulli.us>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add IFLA_BOND_ARP_VALIDATE to allow get/set of bonding parameter
arp_validate via netlink.
Signed-off-by: NScott Feldman <sfeldma@cumulusnetworks.com>
Signed-off-by: NJiri Pirko <jiri@resnulli.us>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add IFLA_BOND_ARP_IP_TARGET to allow get/set of bonding parameter
arp_ip_target via netlink.
Signed-off-by: NScott Feldman <sfeldma@cumulusnetworks.com>
Signed-off-by: NJiri Pirko <jiri@resnulli.us>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add IFLA_BOND_ARP_INTERVAL to allow get/set of bonding parameter
arp_interval via netlink.
Signed-off-by: NScott Feldman <sfeldma@cumulusnetworks.com>
Signed-off-by: NJiri Pirko <jiri@resnulli.us>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add IFLA_BOND_USE_CARRIER to allow get/set of bonding parameter
use_carrier via netlink.
Signed-off-by: NScott Feldman <sfeldma@cumulusnetworks.com>
Signed-off-by: NJiri Pirko <jiri@resnulli.us>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add IFLA_BOND_DOWNDELAY to allow get/set of bonding parameter
downdelay via netlink.
Signed-off-by: NScott Feldman <sfeldma@cumulusnetworks.com>
Signed-off-by: NJiri Pirko <jiri@resnulli.us>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add IFLA_BOND_UPDELAY to allow get/set of bonding parameter
updelay via netlink.
Signed-off-by: NScott Feldman <sfeldma@cumulusnetworks.com>
Signed-off-by: NJiri Pirko <jiri@resnulli.us>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add IFLA_BOND_MIIMON to allow get/set of bonding parameter
miimon via netlink.
Signed-off-by: NScott Feldman <sfeldma@cumulusnetworks.com>
Signed-off-by: NJiri Pirko <jiri@resnulli.us>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patches fixes the following warning by replacing smp_processor_id()
with raw_smp_processor_id():

[   11.120893] BUG: using smp_processor_id() in preemptible [00000000] code: arping/3510
[   11.120913] caller is .packet_sendmsg+0xc14/0xe68
[   11.120920] CPU: 13 PID: 3510 Comm: arping Not tainted 3.13.0-rc3-next-20131211-dirty #1
[   11.120926] Call Trace:
[   11.120932] [c0000001f803f6f0] [c0000000000138dc] .show_stack+0x110/0x25c (unreliable)
[   11.120942] [c0000001f803f7e0] [c00000000083dd24] .dump_stack+0xa0/0x37c
[   11.120951] [c0000001f803f870] [c000000000493fd4] .debug_smp_processor_id+0xfc/0x12c
[   11.120959] [c0000001f803f900] [c0000000007eba78] .packet_sendmsg+0xc14/0xe68
[   11.120968] [c0000001f803fa80] [c000000000700968] .sock_sendmsg+0xa0/0xe0
[   11.120975] [c0000001f803fbf0] [c0000000007014d8] .SyS_sendto+0x100/0x148
[   11.120983] [c0000001f803fd60] [c0000000006fff10] .SyS_socketcall+0x1c4/0x2e8
[   11.120990] [c0000001f803fe30] [c00000000000a1e4] syscall_exit+0x0/0x9c
Signed-off-by: NLi Zhong <zhong@linux.vnet.ibm.com>
Acked-by: NJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add support to netconf to show changes to proxy-arp status on a per
interface basis via netlink in a manner similar to forwarding
and reverse path state.
Signed-off-by: NStephen Hemminger <stephen@networkplumber.org>
Acked-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>

A freshly allocated skb starts with timestamps clear.
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>

The SFC9100 family has only one clock per controller, shared by all
functions.  Therefore only create a clock device under the primary
function, and make all other functions refer to the primary's clock
device.

Since PTP functionality is limited to port 0 and PF 0 on the earlier
SFN[56]322F boards, and we also set the primary flag for that
function, we can make the creation of a clock device conditional only
on this flag.
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>

The primary function of an EF10 controller will share its clock
device with other functions in the same domain (which we call
secondary functions).  To this end, we need to associate functions
on the same controller.

We do not control probe order, so allow primary and secondary
functions to appear in any order.  Maintain global lists of all
primary functions and of unassociated secondary functions,
and a list of secondary functions on each primary function.

Use the VPD serial number to tell whether functions are part of the
same controller.  VPD will not be readable by virtual functions, so
this may need to be revisited later.
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>

Original version by Stuart Hodgson.
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>

The EF10 firmware can optionally insert RX timestamps in the packet
prefix.  These only include the clock minor value.  We must also
enable periodic time sync events on each event queue which provide
the high bits of the clock value.

[bwh: Combined and rebased several changes.
 Added the above description and some sanity checks for inline vs
 separate timestamps.
 Changed efx_rx_skb_attach_timestamp() to read the packet prefix
 from the skb head area.]
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>