Entries by Raymond P. Burkholder

Etherate code on Github is supplemented with some documentation and comments at 53bits Etherate.

Etherate sends traffic directly over Ethernet so it goes without saying that all tests between Tx and Rx hosts are run within the same layer 2 broadcast domain, it can not test over a layer 3 boundary.

TRex Low-Cost, High-Speed Stateful Traffic Generator

MoonGen is a fully scriptable high-speed packet generator built on DPDK and LuaJIT. It can saturate a 10 Gbit/s connection with 64 byte packets on a single CPU core while executing user-provided Lua scripts for each packet. Multi-core support allows for even higher rates. It also features precise and accurate timestamping and rate control.

iperf3

The article DON'T USE ARDUINO (FOR PROFESSIONAL WORK) provides some thoughts on reasons not to use Arduino, including concepts on troubleshooting, licensing, and power utilization. All good reasons.

And the author did provide a couple of alternatives:

• arm mbed
• Lets Get Board talks about differences between three versions of Cortex architectures.

For something completely different, a MIND diet which slows cognitive decline with aging.

We devised a new diet that is tailored to protection of the brain, called MIND (Mediterranean-DASH Diet Intervention for Neurodegenerative Delay). The diet is styled after the Mediterranean and DASH diets but with modifications based on the most compelling findings in the diet-dementia field. For example, a number of prospective studies7–10 observed slower decline in cognitive abilities with high consumption of vegetables, and in the two U.S. studies, the greatest protection was from green leafy vegetables.7;8 Further, all of these studies found no association of overall fruit consumption with cognitive decline. However, animal models11 and one large prospective cohort study12 indicate that at least one particular type of fruit – berries - may protect the brain against cognitive loss.

Encountered at What Happened When I Ate The Best Brain Foods For A Week.

Following on from my previous post on building a FRR package series, this provides the process for installing an FRR (Free Range Routing) package. Some content is taken from Building_FRR_on_Debian8.md.

# update/upgrade existing packages
sudo apt update
sudo apt upgrade

# install a few necessary packages
sudo apt install iproute libc-ares2  libjson-c3

# install frr (users and groups installed via the package)
sudo dpkg -i frr_3.1-dev_amd64.deb

# create empty frr configuration files
sudo install -m 755 -o frr -g frr -d /var/log/frr
sudo install -m 775 -o frr -g frrvty -d /etc/frr
sudo install -m 640 -o frr -g frr /dev/null /etc/frr/zebra.conf
sudo install -m 640 -o frr -g frr /dev/null /etc/frr/bgpd.conf
sudo install -m 640 -o frr -g frr /dev/null /etc/frr/ospfd.conf
sudo install -m 640 -o frr -g frr /dev/null /etc/frr/ospf6d.conf
sudo install -m 640 -o frr -g frr /dev/null /etc/frr/isisd.conf
sudo install -m 640 -o frr -g frr /dev/null /etc/frr/ripd.conf
sudo install -m 640 -o frr -g frr /dev/null /etc/frr/ripngd.conf
sudo install -m 640 -o frr -g frr /dev/null /etc/frr/pimd.conf
sudo install -m 640 -o frr -g frr /dev/null /etc/frr/ldpd.conf
sudo install -m 640 -o frr -g frr /dev/null /etc/frr/nhrpd.conf
sudo install -m 640 -o frr -g frrvty /dev/null /etc/frr/vtysh.conf

Enable routing by setting the following in /etc/sysctl.conf, then running 'sysctl -p'

net.ipv4.ip_forward=1
net.ipv6.conf.all.forwarding=1

Configuration files can then be edited as appropriate, then the services started with:

sudo systemctl start frr

Basic instructions for building Debian packages for FRR (Free Range Routing), a fork of Quagga, can be found in the github repository as Building FRR on Debian 8 from Git Source.

# update/upgrade existing packages
apt update
apt upgrade

# install necessary packages
apt install \
 libsystemd-dev \
 linuxdoc-tools \
 build-essential \
 debhelper \
 git autoconf automake libtool make gawk \
 libreadline-dev texinfo libjson-c-dev pkg-config bison flex \
 python-pip libc-ares-dev python3-dev

# install newer pytest (>3.0) from pip
pip install pytest

# add frr groups and user (not sure if this step is actually needed)
addgroup --system --gid 92 frr
addgroup --system --gid 85 frrvty
adduser --system --ingroup frr --home /var/run/frr/  \
  --gecos "FRR suite" --shell /bin/false frr
usermod -a -G frrvty frr

# download source for master
git clone https://github.com/FRRouting/frr.git frr

# prepare build files
cd frr
./bootstrap.sh

# invoke debian package builder
dh binary-arch

As of this writing, the following packages are built, with the first being the one of interest:

frr_3.1-dev_amd64.deb
frr-dbg_3.1-dev_amd64.deb
frr-dbgsym_3.1-dev_amd64.deb

gcc -v for debian/stretch yields:

gcc version 6.3.0 20170516 (Debian 6.3.0-18)

I have been looking at alternatives for entry-access mechanisms. Some things to be looked into include:

NFC (Near Field Communications)
• Arduino NFC Shield features a transceiver module, PN532, which handles wireless communication at 13.56MHz, this means that you can read and write a 13.56MHz tag with this shield or implement point to point (P2P) data exchange between the shield and a smart phone. There is an NFC Library using PN532 to read/write card and communicate with android.
• Tutorial for NFC Shield and NFC Module from ElecFreaks.

Also similar to the topic is the controls behind the scenes. It is possibly to turn an Arduino into a PLC, complete with PLC style enclosures and PLC style software:

• CONTROLLINO was the first ARDUINO compatible software open-soure PLC (programmable logic controller) and is the market leader in its field. Programming software for the solution.
• Industrial Shields
• industruino prototyping kit
• Hartmut Wendt DIN rail enclosure: ArduiBox Open for Arduino Uno, 101, Zero
• plcLib: PLC Software for the Arduino

Other interesting bits:

• LoRa mini long distance wireless rx/tx. Along with this low power scenario, there are solar cells and Lithium Ion Polymer batteries, and charger.
• DMX Shields. Some additional info on DMX512 as an Arduino shield.
• DMX 512 Opto Isolated Arduino shield. Lots of other interesting projects at this site.
• MegaMoto Motor Control Shield for Arduino -- 30A of current at up to 28V in two half bridge or one full bridge.
• Grid-Eye 8x8 IR Array

From demystifying openvswitch (with the slide deck showing some interesting edit shortcuts with virsh, and slide 13 may be incorrect as trunk is default):

• ovs-vsctl: Set up, maintain, and inspect various openvswitch configurations. It provides a high level interface to the database to query and apply changes at run time. Operations are persistent across reboot. Example: ovs-vsctl --format=table --column=name,vlan_mode
• ovs-ofctl, ovs-dpctl: Administer and monitor flow entries. Two kinds of flows: openflows (flows managed at control plane) and datapath (kernel flow, cached version of openflow). ovs-ofctl speaks to openflow module. ovs-dpctl talks to kernel module.
• ovs-appctl: Sends commands to a running openvswitch to gather information which is not directly exposed to ovs-ofctl -- the Swiss Army knife of openflow troubleshooting. Example: ovs-appctl vlog/list, ovs-appctl vlog/set module(:facility(:level)) where level is emer, err, warn, info, dbg
• ovsdb-client: query the ovs database. Example: ovsdb-lient list-tables, ovsdb-client list-columns , ovsdb-client monitor --detach
• ovsdb-tool showlog

openvswitch deep dive on slide 14 and 15, shows relationship between commands and the daemons.

• SIGCOMM '17: 2017/08/21 -- SIGCOMM is the flagship annual conference of the ACM Special Interest Group on Data Communication (SIGCOMM) on the applications, technologies, architectures, and protocols for computer communication.
• CppCon 2017: 2017/09/23 -- is the annual, week-long face-to-face gathering for the entire C++ community.
• SaltConf17: 2017/10/31 -- fourth annual SaltStack global user conference will be held in Salt Lake City,
• LISA17: Where systems engineering and operations professionals share real-world knowledge about designing, building, and maintaining the critical systems of our interconnected world.

From a recent netfilter mailing list message:

Logging from network namespaces other than init has been disabled since kernel 3.10 in order to prevent host kernel log flooding from inside a container.

If you have kernel >= 4.11 or one with commit 2851940ffee3 ("netfilter: allow logging from non-init namespaces") backported, you can enable netfilter logging from other network namespaces by

 echo 1 >/proc/sys/net/netfilter/nf_log_all_netns

(the command must be issued from init_net).

Logging via NFLOG target and ulogd2 should work even without the sysctl mentioned above, IIRC.

From the netfilter mailing list:

... connection tracking helpers assignation can only be used with nft 0.8 and Linux 4.12.

You can set automatic assignment with:

echo 1 > /proc/sys/net/netfilter/nf_conntrack_helper 

With all the BTRFS bashing going on, even though it is recommended one cares about checksummed data and metadata, there wasn't an easy alternative. That has now been solved.

ZFS is now (ie, for some time now) available as a set of native (contrib) packages in Debian. I will need to give that a test now. [zfs-zed, zfsutils-linux, zfs-dkms, zfs-initramfs, zfsutils, zfs-dracut]. With the right set of packages and boot configuration, it is also possible to use zfs as a boot partition.

Package is tracker is zfs-linux.

Primary web site is zfsonlinux.org. Documentation, FAQ, and a wiki can be found there.

A quicky setup and go can be found at HowtoForge.

Getting side tracked seems to be a fact of life. This morning it is C++ Unikernels. A variety of unikernels.

This all happened while looking at this years CPPCon 2017 show schedule There is a session on includeOS, which is a performant, minimal unikernel operating system for the cloud. We provide a bootloader, standard libraries and the build- and deployment system. Written and used for C++ apps. And has some references to code for small, light weight http servers, ostensibly probably for REST interfaces. Even LWN has a recent discussion about it.

Also in the program, immer: a library of persistent and immutable data structures written in C++. These enable whole new kinds of architectures for interactive and concurrent programs of striking simplicity, correctness, and performance.

Somewhere along the line, Nix: the purely functional package manager, a part of the purely functional Linux distribution was mentioned.

... the Nix package manager from a description in a purely functional build language. The fact that it’s purely functional essentially means that building a new configuration cannot overwrite previous configurations.

I had thought that the Reactor engine could use pillar states when running states for minions. It may or may not have worked in the future. For the present, it is confirmed as not working: Pillars not available to reactor states #42762. This refers to another issue which supposedly resolves everything in v2017.7.1: Only force saltenv/pillarenv to be a string when not None #42433.

While discovering this issue, I have been thinking about ways to maintain temporary variables somewhere. I first looked at Thorium, but it doesn't seem to have a very flexible two-step look up system, as I need to access variables based upon minion_id, and service type.

The consul pillar state seems to be used only on the master, but I am thinking something should be available on the minion, or accessible from the minion. I thought of the sqlite state for this, but might be a bit heavy duty.

While researching this issue, I came across other interesting Salt articles, which I book mark here, for possible future reference:

• stretch repository is missing packages #42715: this is interesting because in order to load 2017.7.1, I would have to obtain it from the SaltStack repository (as debian doesn't have this yet), and since I run Stretch and Buster, this might cause some issues.
• SaltStack-able Microservices Architecture: Beating the challenge with SaltStack, upstart, consul, consul-template, logstash, etc. An interesting article as it introduces the concept of a jinja macro.
• Combine multiple pillar files under a single key: uses the 'multiple app needs logrotate entries' problem to introduce the concept of merge, os_family_map (which has another issue in github), and jinja 'do' statements.
• Salt consul pillar list of dicts #34458: not necessarily directly relevant, but does have a link to the YAML v1.2 Specifications.
• Using Consul as an External Pillar Source: a simple, detailed way of using Consul for pillar based data for common data as well as minion specific private data.
• Two entries here from the same blogger: Create self-managing servers with Masterless Minions and Using salt-ssh to install Salt, with a bonus reference: Getting redundancy and scalability with multiple master servers"
• Managing your computers with a Salt Master and Git.
• Some notes on using SaltStack: centers the discussion around roles.
• Using Consul as an External Pillar Source
• SaltStack orchestration with Beacons and Reactors

swaks primary design goal is to be a flexible, scriptable, transaction-oriented SMTP test tool. It handles SMTP features and extensions such as TLS, authentication, and pipelining; multiple version of the SMTP protocol including SMTP, ESMTP, and LMTP; and multiple transport methods including unix-domain sockets, internet-domain sockets, and pipes to spawned processes. Options can be specified in environment variables, configuration files, and the command line allowing maximum configurability and ease of use for operators and scripters.

Built in to iproute2:

~$  ip tcp_metrics
192.168.4.2 age 336273.112sec source 192.168.4.1
10.151.0.10 age 17668.708sec cwnd 10 rtt 969us rttvar 788us source 10.9.2.21
10.152.0.10 age 8.368sec source 10.9.2.21

sysstat package (edit /etc/default/sysstat and change ENABLED from false to true, and change /etc/cron.d/sysstat to a different interval)

to look into:
• sysstat package: sar

netstat

netstat -s|grep -i retran
    19448 segments retransmitted
    161 times recovered from packet loss due to fast retransmit
    Detected reordering 3 times using reno fast retransmit
    1 timeouts after reno fast retransmit
    303 fast retransmits
    1 retransmits in slow start
    TCPRetransFail: 167
    TCPSynRetrans: 13966

More stats than you can shake a stick at: ss -ti

Papers on TCP:

• TCP Congestion Control on RTP Media Streams: using ffmpeg, tcptrace, mininet, wanem
• TCP Tuning Techniques for High-Speed Wide-Area Networks: presentation
• Identification of Hostile TCP Traffic Using Support Vector Machines
• SLAC Network Monitoring Tools: large list of curated tools