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- All rights reserved.
-
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- modification, are permitted provided that the following conditions
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-
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- the documentation and/or other materials provided with the
- distribution.
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- 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
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-
-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.
--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::
- 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.
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.
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 | |
++--------------------+-----------------------+
+
Code Review / deb_dpdk.git / blobdiff