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Diffstat (limited to 'doc/guides/nics/tap.rst')
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1 files changed, 88 insertions, 40 deletions
diff --git a/doc/guides/nics/tap.rst b/doc/guides/nics/tap.rst index 04086b11..ea61be38 100644 --- a/doc/guides/nics/tap.rst +++ b/doc/guides/nics/tap.rst @@ -1,37 +1,10 @@ -.. BSD LICENSE - Copyright(c) 2016 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. - -Tun/Tap Poll Mode Driver -======================== - -The ``rte_eth_tap.c`` PMD creates a device using TUN/TAP interfaces on the +.. SPDX-License-Identifier: BSD-3-Clause + Copyright(c) 2016 Intel Corporation. + +Tap Poll Mode Driver +==================== + +The ``rte_eth_tap.c`` PMD creates a device using TAP interfaces on the local host. The PMD allows for DPDK and the host to communicate using a raw device interface on the host and in the DPDK application. @@ -53,11 +26,6 @@ The interface name can be changed by adding the ``iface=foo0``, for example:: --vdev=net_tap0,iface=foo0 --vdev=net_tap1,iface=foo1, ... -Also the speed of the interface can be changed from 10G to whatever number -needed, but the interface does not enforce that speed, for example:: - - --vdev=net_tap0,iface=foo0,speed=25000 - Normally the PMD will generate a random MAC address, but when testing or with a static configuration the developer may need a fixed MAC address style. Using the option ``mac=fixed`` you can create a fixed known MAC address:: @@ -132,6 +100,7 @@ Supported actions: - DROP - QUEUE - PASSTHRU +- RSS (requires kernel 4.9) It is generally not possible to provide a "last" item. However, if the "last" item, once masked, is identical to the masked spec, then it is supported. @@ -161,10 +130,15 @@ Drop UDP packets in vlan 3:: testpmd> flow create 0 priority 3 ingress pattern eth / vlan vid is 3 / \ ipv4 proto is 17 / end actions drop / end +Distribute IPv4 TCP packets using RSS to a given MAC address over queues 0-3:: + + testpmd> flow create 0 priority 4 ingress pattern eth dst is 0a:0b:0c:0d:0e:0f \ + / ipv4 / tcp / end actions rss queues 0 1 2 3 end / end + Example ------- -The following is a simple example of using the TUN/TAP PMD with the Pktgen +The following is a simple example of using the TAP PMD with the Pktgen packet generator. It requires that the ``socat`` utility is installed on the test system. @@ -213,3 +187,77 @@ traffic is being looped back. You can use ``set all size XXX`` to change the size of the packets after you stop the traffic. Use pktgen ``help`` command to see a list of all commands. You can also use the ``-f`` option to load commands at startup in command line or Lua script in pktgen. + +RSS specifics +------------- +Packet distribution in TAP is done by the kernel which has a default +distribution. This feature is adding RSS distribution based on eBPF code. +The default eBPF code calculates RSS hash based on Toeplitz algorithm for +a fixed RSS key. It is calculated on fixed packet offsets. For IPv4 and IPv6 it +is calculated over src/dst addresses (8 or 32 bytes for IPv4 or IPv6 +respectively) and src/dst TCP/UDP ports (4 bytes). + +The RSS algorithm is written in file ``tap_bpf_program.c`` which +does not take part in TAP PMD compilation. Instead this file is compiled +in advance to eBPF object file. The eBPF object file is then parsed and +translated into eBPF byte code in the format of C arrays of eBPF +instructions. The C array of eBPF instructions is part of TAP PMD tree and +is taking part in TAP PMD compilation. At run time the C arrays are uploaded to +the kernel via BPF system calls and the RSS hash is calculated by the +kernel. + +It is possible to support different RSS hash algorithms by updating file +``tap_bpf_program.c`` In order to add a new RSS hash algorithm follow these +steps: + +1. Write the new RSS implementation in file ``tap_bpf_program.c`` + +BPF programs which are uploaded to the kernel correspond to +C functions under different ELF sections. + +2. Install ``LLVM`` library and ``clang`` compiler versions 3.7 and above + +3. Compile ``tap_bpf_program.c`` via ``LLVM`` into an object file:: + + clang -O2 -emit-llvm -c tap_bpf_program.c -o - | llc -march=bpf \ + -filetype=obj -o <tap_bpf_program.o> + + +4. Use a tool that receives two parameters: an eBPF object file and a section +name, and prints out the section as a C array of eBPF instructions. +Embed the C array in your TAP PMD tree. + +The C arrays are uploaded to the kernel using BPF system calls. + +``tc`` (traffic control) is a well known user space utility program used to +configure the Linux kernel packet scheduler. It is usually packaged as +part of the ``iproute2`` package. +Since commit 11c39b5e9 ("tc: add eBPF support to f_bpf") ``tc`` can be used +to uploads eBPF code to the kernel and can be patched in order to print the +C arrays of eBPF instructions just before calling the BPF system call. +Please refer to ``iproute2`` package file ``lib/bpf.c`` function +``bpf_prog_load()``. + +An example utility for eBPF instruction generation in the format of C arrays will +be added in next releases + +Systems supporting flow API +--------------------------- + +- "tc flower" classifier requires linux kernel above 4.2 +- eBPF/RSS requires linux kernel above 4.9 + ++--------------------+-----------------------+ +| RH7.3 | No flow rule support | ++--------------------+-----------------------+ +| RH7.4 | No RSS action support | ++--------------------+-----------------------+ +| RH7.5 | No RSS action support | ++--------------------+-----------------------+ +| SLES 15, | No limitation | +| kernel 4.12 | | ++--------------------+-----------------------+ +| Azure Ubuntu 16.04,| No limitation | +| kernel 4.13 | | ++--------------------+-----------------------+ + |