The hot-plug alarm mechanism of fail-safe PMD is responsible for
handling removed devices during a plug-out event and to restore them
back to activity following a plug-in event.
Fail-safe sets a flag called "pending_alarm" to validate that only one
alarm callback is pending at any time. While this flag is required to
avoid simultaneous initiations of the alarm thread - it should not be
considered during alarm thread cancellation.
So, when failsafe_hotplug_alarm_cancel() was called while the alarm
callback was being executed the alarm mechanism was not stopped.
Skip checking the "pending_alarm" flag to allow alarm thread
cancellation all the times.
Fixes: ebea83f899 ("net/failsafe: add plug-in support")
Cc: stable@dpdk.org
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Failsafe reported Tx offloads capabilities are the AND result of its
default capabilities and those of its sub-devices.
In the corrupted code failsafe default Tx capabilities were set to 0.
As a result when running testpmd with "--tx-offloads=0x8000" parameter
(request for multi segments offload) - an error was returned:
PMD: net_failsafe:
Some Tx offloads are not supported, requested 0x8000 supported 0x0
To fix this, failsafe default Tx offload capabilities are set to
DEV_TX_OFFLOAD_MULTI_SEGS |
DEV_TX_OFFLOAD_IPV4_CKSUM |
DEV_TX_OFFLOAD_UDP_CKSUM |
DEV_TX_OFFLOAD_TCP_CKSUM,
Fixes: a46f8d584e ("net/failsafe: add fail-safe PMD")
Cc: stable@dpdk.org
Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Fail-safe PMD sub devices management is based on ethdev port mechanism.
So, the sub-devices management structures are exposed to other DPDK
entities which may use them in parallel to fail-safe PMD.
Use the new port ownership mechanism to avoid multiple managments of
fail-safe PMD sub-devices.
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Call dedicated ethdev API to free port in remove time as was done in
other fail-safe places.
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
This patch is the last patch in the series of patches aimed
to add support for registering and waiting for Rx interrupts
in failsafe PMD. This allows applications to wait for Rx events
from the PMD using the DPDK rte_epoll subsystem.
The failsafe PMD presents to the application a facade of a single
device to be handled by the application while internally it manages
several devices on behalf of the application including packets
transmission and reception.
The Proposed failsafe Rx interrupt scheme follows this approach.
The failsafe PMD will present the application with a single set of
Rx interrupt vectors representing the failsafe Rx queues, while
internally it will serve as an interrupt proxy for its subdevices.
will allow applications to wait for Rx traffic from the failsafe
PMD by registering and waiting for Rx events from its Rx queues.
In order to support this the following is suggested:
* Every Rx queue in the failsafe (virtual) device will be assigned
* a Linux event file descriptor (efd) and an enable_interrupts flag.
* The failsafe PMD will fill in its rte_intr_handle structure with
the Rx efds assigned previously and register them with the EAL.
* The failsafe driver will create a private epoll fd (epfd) and
* will allocate enough space to handle all the Rx events from all its
subdevices.
* Acting as an application,
for each Rx queue in each active subdevice the failsafe will:
o Register the Rx queue with the EAL.
o Pass the EAL the failsafe private epoll fd as the epfd to
register the Rx queue event on.
o Pass the EAL, as a parameter, the pointer to the failsafe Rx
queue that handles this Rx queue.
o Using the DPDK service callbacks, the failsafe PMD will launch
an Rx proxy service that will Wait on the epoll fd for Rx
events from the sub-devices.
o For each Rx event received the proxy service will
- Retrieve the pointer to failsafe Rx queue that handles
this subdevice Rx queue from the user info returned by the
EAL.
- Trigger a failsafe Rx event on that queue by writing to
the event fd unless interrupts are disabled for that queue.
* The failsafe pmd will also implement the rx_queue_intr_enable
* and rx_queue_intr_disable routines that will enable and disable Rx
interrupts respectively on both on the failsafe and its subdevices.
Signed-off-by: Moti Haimovsky <motih@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
This commit adds the following functionality to failsafe PMD:
* Register and unregister slaves Rx interrupts.
* Enable and Disable slaves Rx interrupts.
The interrupts events generated by the slaves are not handled in this
commit.
Signed-off-by: Moti Haimovsky <motih@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
This patch adds registering the Rx queues of the failsafe PMD with EAL
Rx interrupts subsystem.
Each failsafe RX queue is assigned with a unique eventfd and an enable
interrupts flag.
The PMD creates an interrupt vector containing the above eventfds and
Registers it with EAL. The PMD also implements the Rx interrupts enable
and disable interface routines.
This patch does not implement the generation of Rx interrupts, so an
application can now wait for failsafe Rx interrupts but it will not
receive one.
Signed-off-by: Moti Haimovsky <motih@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
In case of plugged out device, the fail-safe PMD uses failsafe_rx_burst
function for packet receiving.
This function iterates over the present sub-devices until it
receives a traffic from one of them or they are all cannot receive
packets.
The corrupted code didn't advance the sub-device pointer when the
sub-device was not present and caused to infinite loop.
Advance the sub-device pointer also in plugged-out sub-device case.
Fixes: 8052bbd9d5 ("net/failsafe: improve Rx sub-devices iteration")
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Add checks during build to ensure that all symbols in the EXPERIMENTAL
version map section have __experimental tags on their definitions, and
enable the warnings needed to announce their use. Also add an
ALLOW_EXPERIMENTAL_APIS define to allow individual libraries and files
to declare the acceptability of experimental api usage
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>
Create a rte_ethdev_driver.h file and move PMD specific APIs here.
Drivers updated to include this new header file.
There is no update in header content and since ethdev.h included by
ethdev_driver.h, nothing changed from driver point of view, only
logically grouping of APIs. From applications point of view they can't
access to driver specific APIs anymore and they shouldn't.
More PMD specific data structures still remain in ethdev.h because of
inline functions in header use them. Those will be handled separately.
Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Shreyansh Jain <shreyansh.jain@nxp.com>
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>
There is time between the physical removal of the device until
sub-device PMDs get a RMV interrupt. At this time DPDK PMDs and
applications still don't know about the removal and may call sub-device
control operation which should return an error.
In previous code this error is reported to the application contrary to
fail-safe principle that the app should not be aware of device removal.
Add an removal check in each relevant control command error flow and
prevent an error report to application when the sub-device is removed.
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Previous fail-safe code didn't support probed sub-devices capture and
failed when it tried to probe them.
Skip fail-safe sub-device probing when it already was probed.
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
rte_free() is not supposed to work with pointers returned by calloc().
Fixes: a0194d8281 ("net/failsafe: add flexible device definition")
Cc: stable@dpdk.org
Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Ethdev Rx offloads API has changed since:
commit ce17eddefc ("ethdev: introduce Rx queue offloads API")
This commit adds support for the new Rx offloads API.
Signed-off-by: Moti Haimovsky <motih@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Ethdev Tx offloads API has changed since:
commit cba7f53b71 ("ethdev: introduce Tx queue offloads API")
This commit adds support for the new Tx offloads API.
Signed-off-by: Moti Haimovsky <motih@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Connecting the sub-devices each other by cyclic linked list can help to
iterate over them by Rx burst functions because there is no need to
check the sub-devices ring wraparound.
Create the aforementioned linked-list and change the Rx burst functions
iteration accordingly.
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Fail-safe uses atomic operations to protect sub-device close operation
calling by host thread in removal time while the removed sub-device
burst functions are still in process by application threads.
Using "set" atomic operations is a little bit more efficient than "add"
or "sub" atomic operations because "set" shouldn't read the value and
in fact, it does not need a special atomic mechanism in x86 platforms.
Replace "add 1" and "sub 1" atomic operations by "set 1" and "set 0"
atomic operations.
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
failsafe_rx_burst function is used when there are no sub-devices or at
least one of them has been removed, on the other hand, when all the
sub-devices are present, failsafe_rx_burst_fast function is used.
So it's really expected that some of the sub-devices will be unsafe for
Rx burst in failsafe_rx_burst execution.
Remove unlikely compiler hint from fs_rx_unsafe calling.
Fixes: a46f8d584e ("net/failsafe: add fail-safe PMD")
Cc: stable@dpdk.org
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
The pointer to the user parameter of the callback registration is
automatically pass to the callback function.
There is no point to allow changing this user parameter by a caller.
That's why this parameter is always set to NULL by PMDs and set only
in ethdev layer before calling the callback function.
The history is that the user parameter was initially used
by the callback implementation to pass some information
between the application and the driver:
c1ceaf3ad0 ("ethdev: add an argument to internal callback function")
Then a new parameter has been added to leave the user parameter
to its standard usage of context given at registration:
d6af1a13d7 ("ethdev: add return values to callback process API")
The NULL parameter in the internal callback processing function
is now removed. It makes clear that the callback parameter is user
managed and opaque from a DPDK point of view.
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>
There are 3 kind of link data in ethdev:
- capabilities (rte_eth_dev_info)
- configuration (rte_eth_conf)
- status (rte_eth_link)
A bit-field is used for capabilities (rte_eth_dev_info.speed_capa) and
configuration (rte_eth_conf.link_speeds).
Bits are defined in ETH_LINK_SPEED_*.
Some numerical (ETH_SPEED_NUM_*) and boolean (ETH_LINK_*) values
are used for the link status (rte_eth_link.*).
There was a mistake in the comment of rte_eth_link.link_autoneg,
suggesting ETH_LINK_SPEED_[AUTONEG/FIXED] which are 0/1,
instead of ETH_LINK_[AUTONEG/FIXED] which are 1/0.
The drivers are fixed to use ETH_LINK_[AUTONEG/FIXED].
Fixes: 82113036e4 ("ethdev: redesign link speed config")
Suggested-by: Andrew Rybchenko <arybchenko@solarflare.com>
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Move the vdev bus from lib/librte_eal to drivers/bus.
As the crypto vdev helper function refers to data structure
in rte_vdev.h, so we move those helper function into drivers/bus
too.
Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
failsafe device has vlan stripping configured at startup however once
a sub device is found as non-capable of vlan-stripping failsafe
updates it configuration and removes vlan stripping from it.
This update occurs only once at startup. Following a later plugin
attempt and in case of vlan stripping mismatch between failsafe
configuration and device capability - failsafe cannot recover and the
device remains constantly in plug out state.
The sequence of events leading to this situation is described as
follows:
1. Start testpmd with failsafe where mlx4 is a sub device (not capable
of vlan stripping). Expected printout:
PMD: net_failsafe: Disabling VLAN stripping offload
2. Execute:
testpmd> port stop all
testpmd> port config all max-pkt-len 2048
testpmd> port start all
3. Do a plug out (e.g. disable sriov)
4. Do a plug in (e.g. enable sriov)
5. Expected result: failsafe successfully configures and starts its sub
devices
Actual result: failsafe is continuously failing with these messages:
PMD: net_failsafe: VLAN stripping offload requested but not supported by
sub_device 0
PMD: net_failsafe: device already configured, cannot fix live
configuration
PMD: net_failsafe: Unable to synchronize sub device state
Root cause analysis: at startup failsafe removes vlan stripping from its
configuration. After executing "port config all max-pkt-len 2048"
testpmd marks failsafe in need for configuration update.
After executing "port start all" testpmd overrides failsafe
configuration with its own configuration which includes vlan stripping
During the plugin attempt failsafe refuses to update its configuration
by removing vlan stripping since it has already updated its
configuration at startup.
The fix is for failsafe to stop validation and disabling non-supported
offloads in its sub-devices.
Fixes: bbc6a53dda ("net/failsafe: support Rx offload capabilities")
Cc: stable@dpdk.org
Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>
When removing a device, the fail-safe checks that it is not within its
datapath before cleaning it.
When checking whether an Rx burst should be performed on a device, the
remove flag is not checked. Thus the port could still enter its datapath
and miss a removal round. Furthermore, there is a race between the
thread removing the device and the polling thread.
Check the remove flag before entering a sub-device Rx burst when in safe
mode. This check mitigates the aforementioned race condition.
Fixes: 72a57bfd9a ("net/failsafe: add fast burst functions")
Cc: stable@dpdk.org
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Fail-safe attempts to read an ultimate statistics on removal time; if
that fails, it uses the latest recorded snapshot.
This patch adds timestamp for each stats snapshot to allow a time report
since the last snapshot in case of the above failure.
By this way, the user can estimate the stats read accuracy.
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
The stats_get API was changed to signal a potential failure to read
stats. Furthermore, some PMDs are able to provide statistics even
after a removal event occurred.
Considering this, the fail-safe can try to access the latest
statistics of a PMD to improve statistics accuracy.
Attempt an ultimate statistics read on removal time; if that
fails, use the latest recorded snapshot.
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
When trying to attach a port as a sub-device, the ethdev port
was compared with devargs.
In the case of a PCI device, the name in devargs is the PCI address.
And since DPDK 17.08, the devargs name of the underlying device was
used to match an ethdev port:
a1e7c17555 ("ethdev: use device name from device structure")
But the recent commit 72e3efb149 has reverted this wrong matching
to use the ethdev port name as identifier of the port.
It impacts functions like rte_eth_dev_allocated() used in failsafe
for matching ports with given devargs.
The fix is to search for matching devargs in underlying device of
all ethdev ports.
If many ports match the same PCI device, only the first one is matched.
This limitation was already present in previous implementation of
rte_eth_dev_allocated(), and must be adressed later with a better
devargs syntax.
Fixes: 72e3efb149 ("ethdev: revert use port name from device structure")
Cc: stable@dpdk.org
Signed-off-by: Raslan Darawsheh <rasland@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
The list of libraries in LDLIBS was generated from the DEPDIRS-xyz
variable. This is valid when the subdirectory name match the library
name, but it's not always the case, especially for PMDs.
The patches removes this feature and explicitly adds the proper
libraries in LDLIBS.
Some DEPDIRS-xyz variables become useless, remove them.
Reported-by: Gage Eads <gage.eads@intel.com>
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Reviewed-by: Gage Eads <gage.eads@intel.com>
The stats_get dev op API doesn't include return value, so PMD cannot
return an error in case of failure at stats getting process time.
Since PCI devices can be removed and there is a time between the
physical removal to the RMV interrupt, the user may get invalid stats
without any indication.
This patch changes the stats_get API return value to be int instead of
void.
All the net PMDs stats_get dev ops are adjusted by this patch.
Signed-off-by: Matan Azrad <matan@mellanox.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>
Extend port_id definition from uint8_t to uint16_t in lib and drivers
data structures, specifically rte_eth_dev_data. Modify the APIs,
drivers and app using port_id at the same time.
Fix some checkpatch issues from the original code and remove some
unnecessary cast operations.
release_17_11 and deprecation docs have been updated in this patch.
Signed-off-by: Zhiyong Yang <zhiyong.yang@intel.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>
The previous stats code returned only the current TX sub
device stats.
This enhancement extends it to return the sum of all sub
devices stats with history of removed sub-devices.
Dedicated stats accumulator saves the stat history of all
sub device remove events.
Each failsafe sub device contains the last stats asked by
the user and updates the accumulator in removal time.
I would like to implement ultimate snapshot on removal time.
The stats_get API needs to be changed to return error in the
case it is too late to retrieve statistics.
By this way, failsafe can get stats snapshot in removal interrupt
callback for each PMD which can give stats after removal event.
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
The corrupted code don't reply error in case of MAC
address adding failure while failsafe PMD was trying
to apply configuration to the sub device.
Hence, the application may get unwanted packets.
The fix adds error report for this case.
Fixes: ebea83f899 ("net/failsafe: add plug-in support")
Cc: stable@dpdk.org
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
fs_bus_uninit is always returning 0 no matter what was the status
of each sub device bus_uninit value.
Fixes: a46f8d584e ("net/failsafe: add fail-safe PMD")
Cc: stable@dpdk.org
Signed-off-by: Raslan Darawsheh <rasland@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
The corrupted code used wrongly snprintf return value as the
number of characters actually copied, in spite of the meaning
is the number of characters which would be generated for the
given input.
It caused to remain zerod bytes between the failsafe command line
non sub device parameters indicates end of string.
Hence, when rte_kvargs_parse tried to parse all parameters, it
got end of string after the first one and the others weren't parsed.
So, if the mac parameters was the first in command line it was
taken while hotplug_poll was left default, and vice versa.
The fix updates the buffer index by dedicated variable contains
the copy size, by the way validates the comma separation.
Fixes: a46f8d584e ("net/failsafe: add fail-safe PMD")
Cc: stable@dpdk.org
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
The sub_device iterator macro should follow the general gist of the
tailq API for an easier understanding and safer use.
Once the loop has finished, the iterator should be set to NULL.
If no sub_device was iterated upon, the iterator should still be NULL.
Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
The corrupted code couldn't recognize that all sub devices
were not ready for Tx traffic when failsafe PMD was trying
to switch device because of an unreachable condition using.
Hence, the current Tx sub device variable was not updated
correctly.
The fix removed the unreachable branch and added new one
in the right place respecting the original intent.
Fixes: ebea83f899 ("net/failsafe: add plug-in support")
Fixes: 598fb8aec6 ("net/failsafe: support device removal")
Cc: stable@dpdk.org
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
When the output of an exec() slave definition is only a single newline
character, the fail-safe currently fails to parse the device with the
value returned by the rte_devargs library.
This behavior is incorrect, because the fail-safe should make a
difference between the absence of a device, and an erroneous device
declaration.
Fix the output sanitization in the case where no newline was at its end
and detect the special case of an absent device. The correct error code
is then returned.
Fixes: a0194d8281 ("net/failsafe: add flexible device definition")
Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
When there is no preferred device, failsafe will always
try to scan for preferred device. And if there is no device
found with the exec option, popen() will get an empty output.
In this case, it was forgotten to close the file descriptor.
It is fixed by closing the file descriptor even if the output is empty.
Coverity issue: 158633
Fixes: a0194d8281 ("net/failsafe: add flexible device definition")
Signed-off-by: Raslan Darawsheh <rasland@mellanox.com>
Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
ctype.h is not compilable in BSD 10 on GCC 4.8 in C11 mode.
CC failsafe.o
In file included from /usr/include/_ctype.h:94:0,
from /usr/include/ctype.h:46,
from /root/dpdk.org/build/include/rte_common.h:50,
from /root/dpdk.org/build/include/rte_memory.h:57,
from /root/dpdk.org/build/include/rte_malloc.h:45,
from /root/dpdk.org/drivers/net/failsafe/failsafe.c:35:
/usr/include/runetype.h:92:22: error: expected '=', ',', ';', 'asm' or
'__attribute__' before 'const'
extern _Thread_local const _RuneLocale *_ThreadRuneLocale;
^
/usr/include/runetype.h: In function '__getCurrentRuneLocale':
/usr/include/runetype.h:96:6: error: '_ThreadRuneLocale' undeclareds
(first use in this function)
if (_ThreadRuneLocale)
^
The fix is to put GCC in gnu99 mode instead.
Fixes: a46f8d584e ("net/failsafe: add fail-safe PMD")
Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Listen to INTR_RMV events issued by slaves.
Add atomic flags on slave queues to detect use of slave bursts function.
If a removal is detected, set the recollection flag on this slave.
During a slave upkeep round, if its recollection flag is set and its
burst functions are not in use by any thread, remove that slave.
Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Acked-by: Olga Shern <olgas@mellanox.com>
Add the "exec" device type.
The parameters given to this type of device will be executed in a shell.
The output of this command is then used as a definition for a device.
That command can be re-interpreted if the related device is not
plugged-in. It allows for a device definition to react to system
changes (e.g. changing PCI bus for a given device).
Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Acked-by: Olga Shern <olgas@mellanox.com>
Periodically check for the existence of a device.
If a device has not been initialized and exists on the system, then it
is probed and configured.
The configuration process strives to synchronize the states between the
plugged-in sub-device and the fail-safe device.
Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Acked-by: Olga Shern <olgas@mellanox.com>
Introduce the fail-safe poll mode driver initialization and enable its
build infrastructure.
This PMD allows for applications to benefit from true hot-plugging
support without having to implement it.
It intercepts and manages Ethernet device removal events issued by
slave PMDs and re-initializes them transparently when brought back.
It also allows defining a contingency to the removal of a device, by
designating a fail-over device that will take on transmitting operations
if the preferred device is removed.
Applications only see a fail-safe instance, without caring for
underlying activity ensuring their continued operations.
Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
Acked-by: Olga Shern <olgas@mellanox.com>
