X-Git-Url: http://git.droids-corp.org/?a=blobdiff_plain;f=doc%2Fguides%2Fnics%2Ftap.rst;h=4b6d77d377038f2e844cd14168ba3ab676fce4fb;hb=fb0198b7dc075eaabf52d1de3e73e6ee90679646;hp=5c5ba5357bbaa94bc5f7872410916b728eee9a49;hpb=2bc06869cd94195e986cfb7939a549d7050097e8;p=dpdk.git diff --git a/doc/guides/nics/tap.rst b/doc/guides/nics/tap.rst index 5c5ba5357b..4b6d77d377 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 +.. SPDX-License-Identifier: BSD-3-Clause + Copyright(c) 2016 Intel Corporation. + +Tun|Tap Poll Mode Driver ======================== -The ``rte_eth_tap.c`` PMD creates a device using TUN/TAP interfaces on the +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. @@ -46,17 +19,29 @@ These TAP interfaces can be used with Wireshark or tcpdump or Pktgen-DPDK along with being able to be used as a network connection to the DPDK application. The method enable one or more interfaces is to use the ``--vdev=net_tap0`` option on the DPDK application command line. Each -``--vdev=net_tap1`` option give will create an interface named dtap0, dtap1, +``--vdev=net_tap1`` option given will create an interface named dtap0, dtap1, and so on. 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:: +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:: + + --vdev=net_tap0,mac=fixed + +The MAC address will have a fixed value with the last octet incrementing by one +for each interface string containing ``mac=fixed``. The MAC address is formatted +as 00:'d':'t':'a':'p':[00-FF]. Convert the characters to hex and you get the +actual MAC address: ``00:64:74:61:70:[00-FF]``. - --vdev=net_tap0,iface=foo0,speed=25000 + --vdev=net_tap0,mac="00:64:74:61:70:11" + +The MAC address will have a user value passed as string. The MAC address is in +format with delimiter ``:``. The string is byte converted to hex and you get +the actual MAC address: ``00:64:74:61:70:11``. It is possible to specify a remote netdevice to capture packets from by adding ``remote=foo1``, for example:: @@ -98,14 +83,32 @@ can utilize that stack to handle the network protocols. Plus you would be able to address the interface using an IP address assigned to the internal interface. +The TUN PMD allows user to create a TUN device on host. The PMD allows user +to transmit and receive packets via DPDK API calls with L3 header and payload. +The devices in host can be accessed via ``ifconfig`` or ``ip`` command. TUN +interfaces are passed to DPDK ``rte_eal_init`` arguments as ``--vdev=net_tunX``, +where X stands for unique id, example:: + + --vdev=net_tun0 --vdev=net_tun1,iface=foo1, ... + +Unlike TAP PMD, TUN PMD does not support user arguments as ``MAC`` or ``remote`` user +options. Default interface name is ``dtunX``, where X stands for unique id. + Flow API support ---------------- The tap PMD supports major flow API pattern items and actions, when running on -linux kernels above 4.2 ("Flower" classifier required). Supported items: +linux kernels above 4.2 ("Flower" classifier required). +The kernel support can be checked with this command:: + + zcat /proc/config.gz | ( grep 'CLS_FLOWER=' || echo 'not supported' ) | + tee -a /dev/stderr | grep -q '=m' && + lsmod | ( grep cls_flower || echo 'try modprobe cls_flower' ) + +Supported items: - eth: src and dst (with variable masks), and eth_type (0xffff mask). -- vlan: vid, pcp, tpid, but not eid. (requires kernel 4.9) +- vlan: vid, pcp, but not eid. (requires kernel 4.9) - ipv4/6: src and dst (with variable masks), and ip_proto (0xffff mask). - udp/tcp: src and dst port (0xffff) mask. @@ -114,6 +117,7 @@ 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. @@ -143,10 +147,31 @@ 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 + +Multi-process sharing +--------------------- + +It is possible to attach an existing TAP device in a secondary process, +by declaring it as a vdev with the same name as in the primary process, +and without any parameter. + +The port attached in a secondary process will give access to the +statistics and the queues. +Therefore it can be used for monitoring or Rx/Tx processing. + +The IPC synchronization of Rx/Tx queues is currently limited: + + - Maximum 8 queues shared + - Synchronized on probing, but not on later port update + 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. @@ -156,8 +181,8 @@ used to build the dpdk you pulled down. Run pktgen from the pktgen directory in a terminal with a commandline like the following:: - sudo ./app/app/x86_64-native-linuxapp-gcc/app/pktgen -l 1-5 -n 4 \ - --proc-type auto --log-level 8 --socket-mem 512,512 --file-prefix pg \ + sudo ./app/app/x86_64-native-linux-gcc/app/pktgen -l 1-5 -n 4 \ + --proc-type auto --log-level debug --socket-mem 512,512 --file-prefix pg \ --vdev=net_tap0 --vdev=net_tap1 -b 05:00.0 -b 05:00.1 \ -b 04:00.0 -b 04:00.1 -b 04:00.2 -b 04:00.3 \ -b 81:00.0 -b 81:00.1 -b 81:00.2 -b 81:00.3 \ @@ -195,3 +220,82 @@ 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 + + +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 + +TAP reports on supported RSS functions as part of dev_infos_get callback: +``ETH_RSS_IP``, ``ETH_RSS_UDP`` and ``ETH_RSS_TCP``. +**Known limitation:** TAP supports all of the above hash functions together +and not in partial combinations. + +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 | | ++--------------------+-----------------------+ +