cachepc-linux

pktgen.rst (12417B)

.. SPDX-License-Identifier: GPL-2.0

====================================
HOWTO for the linux packet generator
====================================

Enable CONFIG_NET_PKTGEN to compile and build pktgen either in-kernel
or as a module.  A module is preferred; modprobe pktgen if needed.  Once
running, pktgen creates a thread for each CPU with affinity to that CPU.
Monitoring and controlling is done via /proc.  It is easiest to select a
suitable sample script and configure that.

On a dual CPU::

    ps aux | grep pkt
    root       129  0.3  0.0     0    0 ?        SW    2003 523:20 [kpktgend_0]
    root       130  0.3  0.0     0    0 ?        SW    2003 509:50 [kpktgend_1]


For monitoring and control pktgen creates::

	/proc/net/pktgen/pgctrl
	/proc/net/pktgen/kpktgend_X
	/proc/net/pktgen/ethX


Tuning NIC for max performance
==============================

The default NIC settings are (likely) not tuned for pktgen's artificial
overload type of benchmarking, as this could hurt the normal use-case.

Specifically increasing the TX ring buffer in the NIC::

 # ethtool -G ethX tx 1024

A larger TX ring can improve pktgen's performance, while it can hurt
in the general case, 1) because the TX ring buffer might get larger
than the CPU's L1/L2 cache, 2) because it allows more queueing in the
NIC HW layer (which is bad for bufferbloat).

One should hesitate to conclude that packets/descriptors in the HW
TX ring cause delay.  Drivers usually delay cleaning up the
ring-buffers for various performance reasons, and packets stalling
the TX ring might just be waiting for cleanup.

This cleanup issue is specifically the case for the driver ixgbe
(Intel 82599 chip).  This driver (ixgbe) combines TX+RX ring cleanups,
and the cleanup interval is affected by the ethtool --coalesce setting
of parameter "rx-usecs".

For ixgbe use e.g. "30" resulting in approx 33K interrupts/sec (1/30*10^6)::

 # ethtool -C ethX rx-usecs 30


Kernel threads
==============
Pktgen creates a thread for each CPU with affinity to that CPU.
Which is controlled through procfile /proc/net/pktgen/kpktgend_X.

Example: /proc/net/pktgen/kpktgend_0::

 Running:
 Stopped: eth4@0
 Result: OK: add_device=eth4@0

Most important are the devices assigned to the thread.

The two basic thread commands are:

 * add_device DEVICE@NAME -- adds a single device
 * rem_device_all         -- remove all associated devices

When adding a device to a thread, a corresponding procfile is created
which is used for configuring this device. Thus, device names need to
be unique.

To support adding the same device to multiple threads, which is useful
with multi queue NICs, the device naming scheme is extended with "@":
device@something

The part after "@" can be anything, but it is custom to use the thread
number.

Viewing devices
===============

The Params section holds configured information.  The Current section
holds running statistics.  The Result is printed after a run or after
interruption.  Example::

    /proc/net/pktgen/eth4@0

    Params: count 100000  min_pkt_size: 60  max_pkt_size: 60
	frags: 0  delay: 0  clone_skb: 64  ifname: eth4@0
	flows: 0 flowlen: 0
	queue_map_min: 0  queue_map_max: 0
	dst_min: 192.168.81.2  dst_max:
	src_min:   src_max:
	src_mac: 90:e2:ba:0a:56:b4 dst_mac: 00:1b:21:3c:9d:f8
	udp_src_min: 9  udp_src_max: 109  udp_dst_min: 9  udp_dst_max: 9
	src_mac_count: 0  dst_mac_count: 0
	Flags: UDPSRC_RND  NO_TIMESTAMP  QUEUE_MAP_CPU
    Current:
	pkts-sofar: 100000  errors: 0
	started: 623913381008us  stopped: 623913396439us idle: 25us
	seq_num: 100001  cur_dst_mac_offset: 0  cur_src_mac_offset: 0
	cur_saddr: 192.168.8.3  cur_daddr: 192.168.81.2
	cur_udp_dst: 9  cur_udp_src: 42
	cur_queue_map: 0
	flows: 0
    Result: OK: 15430(c15405+d25) usec, 100000 (60byte,0frags)
    6480562pps 3110Mb/sec (3110669760bps) errors: 0


Configuring devices
===================
This is done via the /proc interface, and most easily done via pgset
as defined in the sample scripts.
You need to specify PGDEV environment variable to use functions from sample
scripts, i.e.::

    export PGDEV=/proc/net/pktgen/eth4@0
    source samples/pktgen/functions.sh

Examples::

 pg_ctrl start           starts injection.
 pg_ctrl stop            aborts injection. Also, ^C aborts generator.

 pgset "clone_skb 1"     sets the number of copies of the same packet
 pgset "clone_skb 0"     use single SKB for all transmits
 pgset "burst 8"         uses xmit_more API to queue 8 copies of the same
			 packet and update HW tx queue tail pointer once.
			 "burst 1" is the default
 pgset "pkt_size 9014"   sets packet size to 9014
 pgset "frags 5"         packet will consist of 5 fragments
 pgset "count 200000"    sets number of packets to send, set to zero
			 for continuous sends until explicitly stopped.

 pgset "delay 5000"      adds delay to hard_start_xmit(). nanoseconds

 pgset "dst 10.0.0.1"    sets IP destination address
			 (BEWARE! This generator is very aggressive!)

 pgset "dst_min 10.0.0.1"            Same as dst
 pgset "dst_max 10.0.0.254"          Set the maximum destination IP.
 pgset "src_min 10.0.0.1"            Set the minimum (or only) source IP.
 pgset "src_max 10.0.0.254"          Set the maximum source IP.
 pgset "dst6 fec0::1"     IPV6 destination address
 pgset "src6 fec0::2"     IPV6 source address
 pgset "dstmac 00:00:00:00:00:00"    sets MAC destination address
 pgset "srcmac 00:00:00:00:00:00"    sets MAC source address

 pgset "queue_map_min 0" Sets the min value of tx queue interval
 pgset "queue_map_max 7" Sets the max value of tx queue interval, for multiqueue devices
			 To select queue 1 of a given device,
			 use queue_map_min=1 and queue_map_max=1

 pgset "src_mac_count 1" Sets the number of MACs we'll range through.
			 The 'minimum' MAC is what you set with srcmac.

 pgset "dst_mac_count 1" Sets the number of MACs we'll range through.
			 The 'minimum' MAC is what you set with dstmac.

 pgset "flag [name]"     Set a flag to determine behaviour.  Current flags
			 are: IPSRC_RND # IP source is random (between min/max)
			      IPDST_RND # IP destination is random
			      UDPSRC_RND, UDPDST_RND,
			      MACSRC_RND, MACDST_RND
			      TXSIZE_RND, IPV6,
			      MPLS_RND, VID_RND, SVID_RND
			      FLOW_SEQ,
			      QUEUE_MAP_RND # queue map random
			      QUEUE_MAP_CPU # queue map mirrors smp_processor_id()
			      UDPCSUM,
			      IPSEC # IPsec encapsulation (needs CONFIG_XFRM)
			      NODE_ALLOC # node specific memory allocation
			      NO_TIMESTAMP # disable timestamping
 pgset 'flag ![name]'    Clear a flag to determine behaviour.
			 Note that you might need to use single quote in
			 interactive mode, so that your shell wouldn't expand
			 the specified flag as a history command.

 pgset "spi [SPI_VALUE]" Set specific SA used to transform packet.

 pgset "udp_src_min 9"   set UDP source port min, If < udp_src_max, then
			 cycle through the port range.

 pgset "udp_src_max 9"   set UDP source port max.
 pgset "udp_dst_min 9"   set UDP destination port min, If < udp_dst_max, then
			 cycle through the port range.
 pgset "udp_dst_max 9"   set UDP destination port max.

 pgset "mpls 0001000a,0002000a,0000000a" set MPLS labels (in this example
					 outer label=16,middle label=32,
					 inner label=0 (IPv4 NULL)) Note that
					 there must be no spaces between the
					 arguments. Leading zeros are required.
					 Do not set the bottom of stack bit,
					 that's done automatically. If you do
					 set the bottom of stack bit, that
					 indicates that you want to randomly
					 generate that address and the flag
					 MPLS_RND will be turned on. You
					 can have any mix of random and fixed
					 labels in the label stack.

 pgset "mpls 0"		  turn off mpls (or any invalid argument works too!)

 pgset "vlan_id 77"       set VLAN ID 0-4095
 pgset "vlan_p 3"         set priority bit 0-7 (default 0)
 pgset "vlan_cfi 0"       set canonical format identifier 0-1 (default 0)

 pgset "svlan_id 22"      set SVLAN ID 0-4095
 pgset "svlan_p 3"        set priority bit 0-7 (default 0)
 pgset "svlan_cfi 0"      set canonical format identifier 0-1 (default 0)

 pgset "vlan_id 9999"     > 4095 remove vlan and svlan tags
 pgset "svlan 9999"       > 4095 remove svlan tag


 pgset "tos XX"           set former IPv4 TOS field (e.g. "tos 28" for AF11 no ECN, default 00)
 pgset "traffic_class XX" set former IPv6 TRAFFIC CLASS (e.g. "traffic_class B8" for EF no ECN, default 00)

 pgset "rate 300M"        set rate to 300 Mb/s
 pgset "ratep 1000000"    set rate to 1Mpps

 pgset "xmit_mode netif_receive"  RX inject into stack netif_receive_skb()
				  Works with "burst" but not with "clone_skb".
				  Default xmit_mode is "start_xmit".

Sample scripts
==============

A collection of tutorial scripts and helpers for pktgen is in the
samples/pktgen directory. The helper parameters.sh file support easy
and consistent parameter parsing across the sample scripts.

Usage example and help::

 ./pktgen_sample01_simple.sh -i eth4 -m 00:1B:21:3C:9D:F8 -d 192.168.8.2

Usage:::

  ./pktgen_sample01_simple.sh [-vx] -i ethX

  -i : ($DEV)       output interface/device (required)
  -s : ($PKT_SIZE)  packet size
  -d : ($DEST_IP)   destination IP. CIDR (e.g. 198.18.0.0/15) is also allowed
  -m : ($DST_MAC)   destination MAC-addr
  -p : ($DST_PORT)  destination PORT range (e.g. 433-444) is also allowed
  -t : ($THREADS)   threads to start
  -f : ($F_THREAD)  index of first thread (zero indexed CPU number)
  -c : ($SKB_CLONE) SKB clones send before alloc new SKB
  -n : ($COUNT)     num messages to send per thread, 0 means indefinitely
  -b : ($BURST)     HW level bursting of SKBs
  -v : ($VERBOSE)   verbose
  -x : ($DEBUG)     debug
  -6 : ($IP6)       IPv6
  -w : ($DELAY)     Tx Delay value (ns)
  -a : ($APPEND)    Script will not reset generator's state, but will append its config

The global variables being set are also listed.  E.g. the required
interface/device parameter "-i" sets variable $DEV.  Copy the
pktgen_sampleXX scripts and modify them to fit your own needs.


Interrupt affinity
===================
Note that when adding devices to a specific CPU it is a good idea to
also assign /proc/irq/XX/smp_affinity so that the TX interrupts are bound
to the same CPU.  This reduces cache bouncing when freeing skbs.

Plus using the device flag QUEUE_MAP_CPU, which maps the SKBs TX queue
to the running threads CPU (directly from smp_processor_id()).

Enable IPsec
============
Default IPsec transformation with ESP encapsulation plus transport mode
can be enabled by simply setting::

    pgset "flag IPSEC"
    pgset "flows 1"

To avoid breaking existing testbed scripts for using AH type and tunnel mode,
you can use "pgset spi SPI_VALUE" to specify which transformation mode
to employ.


Current commands and configuration options
==========================================

**Pgcontrol commands**::

    start
    stop
    reset

**Thread commands**::

    add_device
    rem_device_all


**Device commands**::

    count
    clone_skb
    burst
    debug

    frags
    delay

    src_mac_count
    dst_mac_count

    pkt_size
    min_pkt_size
    max_pkt_size

    queue_map_min
    queue_map_max
    skb_priority

    tos           (ipv4)
    traffic_class (ipv6)

    mpls

    udp_src_min
    udp_src_max

    udp_dst_min
    udp_dst_max

    node

    flag
    IPSRC_RND
    IPDST_RND
    UDPSRC_RND
    UDPDST_RND
    MACSRC_RND
    MACDST_RND
    TXSIZE_RND
    IPV6
    MPLS_RND
    VID_RND
    SVID_RND
    FLOW_SEQ
    QUEUE_MAP_RND
    QUEUE_MAP_CPU
    UDPCSUM
    IPSEC
    NODE_ALLOC
    NO_TIMESTAMP

    spi (ipsec)

    dst_min
    dst_max

    src_min
    src_max

    dst_mac
    src_mac

    clear_counters

    src6
    dst6
    dst6_max
    dst6_min

    flows
    flowlen

    rate
    ratep

    xmit_mode <start_xmit|netif_receive>

    vlan_cfi
    vlan_id
    vlan_p

    svlan_cfi
    svlan_id
    svlan_p


References:

- ftp://robur.slu.se/pub/Linux/net-development/pktgen-testing/
- ftp://robur.slu.se/pub/Linux/net-development/pktgen-testing/examples/

Paper from Linux-Kongress in Erlangen 2004.
- ftp://robur.slu.se/pub/Linux/net-development/pktgen-testing/pktgen_paper.pdf

Thanks to:

Grant Grundler for testing on IA-64 and parisc, Harald Welte,  Lennert Buytenhek
Stephen Hemminger, Andi Kleen, Dave Miller and many others.


Good luck with the linux net-development.