-.. BSD LICENSE
- Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
- All rights reserved.
-
- Redistribution and use in source and binary forms, with or without
- modification, are permitted provided that the following conditions
- are met:
-
- * Redistributions of source code must retain the above copyright
- notice, this list of conditions and the following disclaimer.
- * Redistributions in binary form must reproduce the above copyright
- notice, this list of conditions and the following disclaimer in
- the documentation and/or other materials provided with the
- distribution.
- * Neither the name of Intel Corporation nor the names of its
- contributors may be used to endorse or promote products derived
- from this software without specific prior written permission.
-
- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+.. SPDX-License-Identifier: BSD-3-Clause
+ Copyright(c) 2010-2015 Intel Corporation.
+
+.. _kni:
Kernel NIC Interface
====================
* Allows an interface with the kernel network stack.
-The components of an application using the DPDK Kernel NIC Interface are shown in Figure 17.
+The components of an application using the DPDK Kernel NIC Interface are shown in :numref:`figure_kernel_nic_intf`.
-.. _pg_figure_17:
+.. _figure_kernel_nic_intf:
-**Figure 17. Components of a DPDK KNI Application**
+.. figure:: img/kernel_nic_intf.*
-.. image43_png has been renamed
+ Components of a DPDK KNI Application
-|kernel_nic_intf|
The DPDK KNI Kernel Module
--------------------------
-The KNI kernel loadable module provides support for two types of devices:
+The KNI kernel loadable module ``rte_kni`` provides the kernel interface
+for DPDK applications.
-* A Miscellaneous device (/dev/kni) that:
+When the ``rte_kni`` module is loaded, it will create a device ``/dev/kni``
+that is used by the DPDK KNI API functions to control and communicate with
+the kernel module.
- * Creates net devices (via ioctl calls).
+The ``rte_kni`` kernel module contains several optional parameters which
+can be specified when the module is loaded to control its behavior:
- * Maintains a kernel thread context shared by all KNI instances
- (simulating the RX side of the net driver).
+.. code-block:: console
- * For single kernel thread mode, maintains a kernel thread context shared by all KNI instances
- (simulating the RX side of the net driver).
+ # modinfo rte_kni.ko
+ <snip>
+ parm: lo_mode: KNI loopback mode (default=lo_mode_none):
+ lo_mode_none Kernel loopback disabled
+ lo_mode_fifo Enable kernel loopback with fifo
+ lo_mode_fifo_skb Enable kernel loopback with fifo and skb buffer
+ (charp)
+ parm: kthread_mode: Kernel thread mode (default=single):
+ single Single kernel thread mode enabled.
+ multiple Multiple kernel thread mode enabled.
+ (charp)
+ parm: carrier: Default carrier state for KNI interface (default=off):
+ off Interfaces will be created with carrier state set to off.
+ on Interfaces will be created with carrier state set to on.
+ (charp)
- * For multiple kernel thread mode, maintains a kernel thread context for each KNI instance
- (simulating the RX side of the new driver).
+Loading the ``rte_kni`` kernel module without any optional parameters is
+the typical way a DPDK application gets packets into and out of the kernel
+network stack. Without any parameters, only one kernel thread is created
+for all KNI devices for packet receiving in kernel side, loopback mode is
+disabled, and the default carrier state of KNI interfaces is set to *off*.
-* Net device:
+.. code-block:: console
- * Net functionality provided by implementing several operations such as netdev_ops,
- header_ops, ethtool_ops that are defined by struct net_device,
- including support for DPDK mbufs and FIFOs.
+ # insmod kmod/rte_kni.ko
- * The interface name is provided from userspace.
+.. _kni_loopback_mode:
- * The MAC address can be the real NIC MAC address or random.
+Loopback Mode
+~~~~~~~~~~~~~
-KNI Creation and Deletion
--------------------------
+For testing, the ``rte_kni`` kernel module can be loaded in loopback mode
+by specifying the ``lo_mode`` parameter:
+
+.. code-block:: console
+
+ # insmod kmod/rte_kni.ko lo_mode=lo_mode_fifo
+
+The ``lo_mode_fifo`` loopback option will loop back ring enqueue/dequeue
+operations in kernel space.
+
+.. code-block:: console
+
+ # insmod kmod/rte_kni.ko lo_mode=lo_mode_fifo_skb
+
+The ``lo_mode_fifo_skb`` loopback option will loop back ring enqueue/dequeue
+operations and sk buffer copies in kernel space.
+
+If the ``lo_mode`` parameter is not specified, loopback mode is disabled.
+
+.. _kni_kernel_thread_mode:
+
+Kernel Thread Mode
+~~~~~~~~~~~~~~~~~~
+
+To provide flexibility of performance, the ``rte_kni`` KNI kernel module
+can be loaded with the ``kthread_mode`` parameter. The ``rte_kni`` kernel
+module supports two options: "single kernel thread" mode and "multiple
+kernel thread" mode.
+
+Single kernel thread mode is enabled as follows:
+
+.. code-block:: console
+
+ # insmod kmod/rte_kni.ko kthread_mode=single
+
+This mode will create only one kernel thread for all KNI interfaces to
+receive data on the kernel side. By default, this kernel thread is not
+bound to any particular core, but the user can set the core affinity for
+this kernel thread by setting the ``core_id`` and ``force_bind`` parameters
+in ``struct rte_kni_conf`` when the first KNI interface is created:
+
+For optimum performance, the kernel thread should be bound to a core in
+on the same socket as the DPDK lcores used in the application.
+
+The KNI kernel module can also be configured to start a separate kernel
+thread for each KNI interface created by the DPDK application. Multiple
+kernel thread mode is enabled as follows:
-The KNI interfaces are created by a DPDK application dynamically.
-The interface name and FIFO details are provided by the application through an ioctl call
-using the rte_kni_device_info struct which contains:
+.. code-block:: console
-* The interface name.
+ # insmod kmod/rte_kni.ko kthread_mode=multiple
-* Physical addresses of the corresponding memzones for the relevant FIFOs.
+This mode will create a separate kernel thread for each KNI interface to
+receive data on the kernel side. The core affinity of each ``kni_thread``
+kernel thread can be specified by setting the ``core_id`` and ``force_bind``
+parameters in ``struct rte_kni_conf`` when each KNI interface is created.
-* Mbuf mempool details, both physical and virtual (to calculate the offset for mbuf pointers).
+Multiple kernel thread mode can provide scalable higher performance if
+sufficient unused cores are available on the host system.
-* PCI information.
+If the ``kthread_mode`` parameter is not specified, the "single kernel
+thread" mode is used.
-* Core affinity.
+.. _kni_default_carrier_state:
-Refer to rte_kni_common.h in the DPDK source code for more details.
+Default Carrier State
+~~~~~~~~~~~~~~~~~~~~~
-The physical addresses will be re-mapped into the kernel address space and stored in separate KNI contexts.
+The default carrier state of KNI interfaces created by the ``rte_kni``
+kernel module is controlled via the ``carrier`` option when the module
+is loaded.
-Once KNI interfaces are created, the KNI context information can be queried by calling the rte_kni_info_get() function.
+If ``carrier=off`` is specified, the kernel module will leave the carrier
+state of the interface *down* when the interface is management enabled.
+The DPDK application can set the carrier state of the KNI interface using the
+``rte_kni_update_link()`` function. This is useful for DPDK applications
+which require that the carrier state of the KNI interface reflect the
+actual link state of the corresponding physical NIC port.
-The KNI interfaces can be deleted by a DPDK application dynamically after being created.
-Furthermore, all those KNI interfaces not deleted will be deleted on the release operation
-of the miscellaneous device (when the DPDK application is closed).
+If ``carrier=on`` is specified, the kernel module will automatically set
+the carrier state of the interface to *up* when the interface is management
+enabled. This is useful for DPDK applications which use the KNI interface as
+a purely virtual interface that does not correspond to any physical hardware
+and do not wish to explicitly set the carrier state of the interface with
+``rte_kni_update_link()``. It is also useful for testing in loopback mode
+where the NIC port may not be physically connected to anything.
+
+To set the default carrier state to *on*:
+
+.. code-block:: console
+
+ # insmod kmod/rte_kni.ko carrier=on
+
+To set the default carrier state to *off*:
+
+.. code-block:: console
+
+ # insmod kmod/rte_kni.ko carrier=off
+
+If the ``carrier`` parameter is not specified, the default carrier state
+of KNI interfaces will be set to *off*.
+
+KNI Creation and Deletion
+-------------------------
+
+Before any KNI interfaces can be created, the ``rte_kni`` kernel module must
+be loaded into the kernel and configured withe ``rte_kni_init()`` function.
+
+The KNI interfaces are created by a DPDK application dynamically via the
+``rte_kni_alloc()`` function.
+
+The ``struct rte_kni_conf`` structure contains fields which allow the
+user to specify the interface name, set the MTU size, set an explicit or
+random MAC address and control the affinity of the kernel Rx thread(s)
+(both single and multi-threaded modes).
+By default the KNI sample example gets the MTU from the matching device,
+and in case of KNI PMD it is derived from mbuf buffer length.
+
+The ``struct rte_kni_ops`` structure contains pointers to functions to
+handle requests from the ``rte_kni`` kernel module. These functions
+allow DPDK applications to perform actions when the KNI interfaces are
+manipulated by control commands or functions external to the application.
+
+For example, the DPDK application may wish to enabled/disable a physical
+NIC port when a user enabled/disables a KNI interface with ``ip link set
+[up|down] dev <ifaceX>``. The DPDK application can register a callback for
+``config_network_if`` which will be called when the interface management
+state changes.
+
+There are currently four callbacks for which the user can register
+application functions:
+
+``config_network_if``:
+
+ Called when the management state of the KNI interface changes.
+ For example, when the user runs ``ip link set [up|down] dev <ifaceX>``.
+
+``change_mtu``:
+
+ Called when the user changes the MTU size of the KNI
+ interface. For example, when the user runs ``ip link set mtu <size>
+ dev <ifaceX>``.
+
+``config_mac_address``:
+
+ Called when the user changes the MAC address of the KNI interface.
+ For example, when the user runs ``ip link set address <MAC>
+ dev <ifaceX>``. If the user sets this callback function to NULL,
+ but sets the ``port_id`` field to a value other than -1, a default
+ callback handler in the rte_kni library ``kni_config_mac_address()``
+ will be called which calls ``rte_eth_dev_default_mac_addr_set()``
+ on the specified ``port_id``.
+
+``config_promiscusity``:
+
+ Called when the user changes the promiscuity state of the KNI
+ interface. For example, when the user runs ``ip link set promisc
+ [on|off] dev <ifaceX>``. If the user sets this callback function to
+ NULL, but sets the ``port_id`` field to a value other than -1, a default
+ callback handler in the rte_kni library ``kni_config_promiscusity()``
+ will be called which calls ``rte_eth_promiscuous_<enable|disable>()``
+ on the specified ``port_id``.
+
+In order to run these callbacks, the application must periodically call
+the ``rte_kni_handle_request()`` function. Any user callback function
+registered will be called directly from ``rte_kni_handle_request()`` so
+care must be taken to prevent deadlock and to not block any DPDK fastpath
+tasks. Typically DPDK applications which use these callbacks will need
+to create a separate thread or secondary process to periodically call
+``rte_kni_handle_request()``.
+
+The KNI interfaces can be deleted by a DPDK application with
+``rte_kni_release()``. All KNI interfaces not explicitly deleted will be
+deleted when the the ``/dev/kni`` device is closed, either explicitly with
+``rte_kni_close()`` or when the DPDK application is closed.
DPDK mbuf Flow
--------------
The kernel module will be aware of mbufs,
but all mbuf allocation and free operations will be handled by the DPDK application only.
-Figure 18 shows a typical scenario with packets sent in both directions.
+:numref:`figure_pkt_flow_kni` shows a typical scenario with packets sent in both directions.
-.. _pg_figure_18:
+.. _figure_pkt_flow_kni:
-**Figure 18. Packet Flow via mbufs in the DPDK KNI**
+.. figure:: img/pkt_flow_kni.*
-.. image44_png has been renamed
+ Packet Flow via mbufs in the DPDK KNI
-|pkt_flow_kni|
Use Case: Ingress
-----------------
The mbuf is dequeued (without waiting due the cache) and filled with data from sk_buff.
The sk_buff is then freed and the mbuf sent in the tx_q FIFO.
-The DPDK TX thread dequeues the mbuf and sends it to the PMD (via rte_eth_tx_burst()).
+The DPDK TX thread dequeues the mbuf and sends it to the PMD via ``rte_eth_tx_burst()``.
It then puts the mbuf back in the cache.
Ethtool
where each net device must register its own callbacks for the supported operations.
The current implementation uses the igb/ixgbe modified Linux drivers for ethtool support.
Ethtool is not supported in i40e and VMs (VF or EM devices).
-
-Link state and MTU change
--------------------------
-
-Link state and MTU change are network interface specific operations usually done via ifconfig.
-The request is initiated from the kernel side (in the context of the ifconfig process)
-and handled by the user space DPDK application.
-The application polls the request, calls the application handler and returns the response back into the kernel space.
-
-The application handlers can be registered upon interface creation or explicitly registered/unregistered in runtime.
-This provides flexibility in multiprocess scenarios
-(where the KNI is created in the primary process but the callbacks are handled in the secondary one).
-The constraint is that a single process can register and handle the requests.
-
-KNI Working as a Kernel vHost Backend
--------------------------------------
-
-vHost is a kernel module usually working as the backend of virtio (a para- virtualization driver framework)
-to accelerate the traffic from the guest to the host.
-The DPDK Kernel NIC interface provides the ability to hookup vHost traffic into userspace DPDK application.
-Together with the DPDK PMD virtio, it significantly improves the throughput between guest and host.
-In the scenario where DPDK is running as fast path in the host, kni-vhost is an efficient path for the traffic.
-
-Overview
-~~~~~~~~
-
-vHost-net has three kinds of real backend implementations. They are: 1) tap, 2) macvtap and 3) RAW socket.
-The main idea behind kni-vhost is making the KNI work as a RAW socket, attaching it as the backend instance of vHost-net.
-It is using the existing interface with vHost-net, so it does not require any kernel hacking,
-and is fully-compatible with the kernel vhost module.
-As vHost is still taking responsibility for communicating with the front-end virtio,
-it naturally supports both legacy virtio -net and the DPDK PMD virtio.
-There is a little penalty that comes from the non-polling mode of vhost.
-However, it scales throughput well when using KNI in multi-thread mode.
-
-.. _pg_figure_19:
-
-**Figure 19. vHost-net Architecture Overview**
-
-.. image45_png has been renamed
-
-|vhost_net_arch|
-
-Packet Flow
-~~~~~~~~~~~
-
-There is only a minor difference from the original KNI traffic flows.
-On transmit side, vhost kthread calls the RAW socket's ops sendmsg and it puts the packets into the KNI transmit FIFO.
-On the receive side, the kni kthread gets packets from the KNI receive FIFO, puts them into the queue of the raw socket,
-and wakes up the task in vhost kthread to begin receiving.
-All the packet copying, irrespective of whether it is on the transmit or receive side,
-happens in the context of vhost kthread.
-Every vhost-net device is exposed to a front end virtio device in the guest.
-
-.. _pg_figure_20:
-
-**Figure 20. KNI Traffic Flow**
-
-.. image46_png has been renamed
-
-|kni_traffic_flow|
-
-Sample Usage
-~~~~~~~~~~~~
-
-Before starting to use KNI as the backend of vhost, the CONFIG_RTE_KNI_VHOST configuration option must be turned on.
-Otherwise, by default, KNI will not enable its backend support capability.
-
-Of course, as a prerequisite, the vhost/vhost-net kernel CONFIG should be chosen before compiling the kernel.
-
-#. Compile the DPDK and insert uio_pci_generic/igb_uio kernel modules as normal.
-
-#. Insert the KNI kernel module:
-
- .. code-block:: console
-
- insmod ./rte_kni.ko
-
- If using KNI in multi-thread mode, use the following command line:
-
- .. code-block:: console
-
- insmod ./rte_kni.ko kthread_mode=multiple
-
-#. Running the KNI sample application:
-
- .. code-block:: console
-
- ./kni -c -0xf0 -n 4 -- -p 0x3 -P -config="(0,4,6),(1,5,7)"
-
- This command runs the kni sample application with two physical ports.
- Each port pins two forwarding cores (ingress/egress) in user space.
-
-#. Assign a raw socket to vhost-net during qemu-kvm startup.
- The DPDK does not provide a script to do this since it is easy for the user to customize.
- The following shows the key steps to launch qemu-kvm with kni-vhost:
-
- .. code-block:: bash
-
- #!/bin/bash
- echo 1 > /sys/class/net/vEth0/sock_en
- fd=`cat /sys/class/net/vEth0/sock_fd`
- qemu-kvm \
- -name vm1 -cpu host -m 2048 -smp 1 -hda /opt/vm-fc16.img \
- -netdev tap,fd=$fd,id=hostnet1,vhost=on \
- -device virti-net-pci,netdev=hostnet1,id=net1,bus=pci.0,addr=0x4
-
-It is simple to enable raw socket using sysfs sock_en and get raw socket fd using sock_fd under the KNI device node.
-
-Then, using the qemu-kvm command with the -netdev option to assign such raw socket fd as vhost's backend.
-
-.. note::
-
- The key word tap must exist as qemu-kvm now only supports vhost with a tap beckend, so here we cheat qemu-kvm by an existing fd.
-
-Compatibility Configure Option
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-There is a CONFIG_RTE_KNI_VHOST_VNET_HDR_EN configuration option in DPDK configuration file.
-By default, it set to n, which means do not turn on the virtio net header,
-which is used to support additional features (such as, csum offload, vlan offload, generic-segmentation and so on),
-since the kni-vhost does not yet support those features.
-
-Even if the option is turned on, kni-vhost will ignore the information that the header contains.
-When working with legacy virtio on the guest, it is better to turn off unsupported offload features using ethtool -K.
-Otherwise, there may be problems such as an incorrect L4 checksum error.
-
-.. |kni_traffic_flow| image:: img/kni_traffic_flow.*
-
-.. |vhost_net_arch| image:: img/vhost_net_arch.*
-
-.. |pkt_flow_kni| image:: img/pkt_flow_kni.*
-
-.. |kernel_nic_intf| image:: img/kernel_nic_intf.*
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