Entries by Raymond P. Burkholder

Quite some ago, there was a discussion around [ovs-dev] Creating a libopenvswitch-dev package, back in 2016. Since then libraries have been updated for C++ inclusion, plus other improvements.

From somewhere, I don't have the reference, maybe my own blog, but since I have this in a note on my desktop, I'll include it here:

• Build a string formatted as the “ovs-ofctl” command would do, for example “table=1,cookie=0xdeadbeef,in_port=1,actions=resubmit(,2)”
• Pass this to parser_ofp_flow_mod_str(). The parser will magically parse the string in to a rich struct.
• Pass the struct to ofputil_encode_flow_mod(). This returns a struct with a serialized OpenFlow message buffer.
• Send this buffer on the wire either via a socket you manage yourself or let OpenVswitch do it for you.

From Phoronix - Linux 5.6 To Bring FQ-PIE Packet Scheduler To Help Fight Bufferbloat, there are some example configurations for using different buffering mechanisms (Implementing the Flow Queue PIE AQM in the Linux Kernel).

For wireless clients:

net.core.default_qdisc=fq
net.ipv4.tcp_congestion_control = bbr

and fq_codel (codel) is better suited for router.

Another possibility:

I had pretty amazing results with cake. I prefer it over fq_codel and it is now part of main line since 4.19.

Cake - Common Applications Kept Enhanced

In the past the internet would just grind to a halt when the Apple devices started cloud syncing. They would totally swamp the outgoing bandwidth. Now nobody notices when an Apple device is syncing.

Open firmware for small routers for congestion management:

The OpenWrt issue with 4MB has to do with using newer kernels. For those devices, DD-WRT is a better bet (still on kernel 3.10).

Overheard on a mail delivery email list:

What we do is FAR from Binary.

Heck, sometimes it feels like the square root of -1 is involved somehow.

An extract from bug #949655 at bugs.debian.org:

I finally found on iPXE website[1] a link to detailed examples, including one[2] to boot pxelinux. It works perfectly with di-netboot-assistant:

#!ipxe
dhcp
set 210:string tftp://my_server/d-i/n-a/
chain ${210:string}pxelinux.0

For those who did not know (like me ), 210 is a standard DHCP option called "path prefix"[3].

• [1]extensive ipxe menu example
• [2]menu.ixpe file
• [3]bootp dhcp parameters

There is a tool called testssl.sh - a free command line tool which checks a server's service on any port for the support of TLS/SSL ciphers, protocols as well as recent cryptographic flaws and more. Very extensive.

$ ./testssl.sh --starttls smtp myrelay.example.org:25
$ ./testssl.sh www.example.org

Or run some simpler tests:

$ openssl s_client -cipher 'DHE' -starttls smtp -crlf -connect myrelay.example.org:25

An older blog entry: SWAKS - Swiss Army Knife SMTP, the all-purpose SMTP transaction tester

2020/01/25 Send an email to

auth-results@verifier.port25.com

2020/01/25 Visit mail-tester.com for another flavour of email tester for spamminess.

• tuned is a profile-based system tuning tool that uses the udev device manager to monitor connected devices, and enables both static and dynamic tuning of system settings. Packages in Debian are 'tuned' and 'tuned-utils'.
• Using netstat and dropwatch to observe packet loss on Linux servers - uses the 'dropwatch' package (needs kernel symbols).
• Track a packet as it goes through the kernel (linux)

Courtesy of 3 quick ways to reduce your attack surface on Linux, a command to identify open ports and identify the associated application:

$ ss -tulnp --no-header | awk '{print($1, $5, $7)}'
udp 0.0.0.0:32770 users:(("vlc",pid=2786557,fd=39))
udp 0.0.0.0:32771 users:(("vlc",pid=2786557,fd=40))
udp 127.0.0.1:123
udp 0.0.0.0:123
udp 0.0.0.0:631
udp 0.0.0.0:37019
udp 0.0.0.0:5353
udp 0.0.0.0:39276 users:(("vlc",pid=2786557,fd=50))
udp 0.0.0.0:39277 users:(("vlc",pid=2786557,fd=51))
tcp 0.0.0.0:61209
tcp 127.0.0.1:25
tcp 127.0.0.1:5433
tcp 0.0.0.0:8794
tcp 127.0.0.1:3493
tcp 127.0.0.1:5101 users:(("ssh",pid=899751,fd=4))
tcp 127.0.0.1:5102 users:(("ssh",pid=2187130,fd=4))
tcp 127.0.0.1:5201 users:(("ssh",pid=2186389,fd=5))
tcp 127.0.0.1:5202 users:(("ssh",pid=2186389,fd=7))
tcp 0.0.0.0:22
tcp 127.0.0.1:631
tcp 127.0.0.1:5432
...

• Zeek s a powerful network analysis framework that is much different from the typical IDS you may know. (Zeek is the new name for the long-established Bro system. While focusing on network security monitoring, Zeek provides a comprehensive platform for more general network traffic analysis as well. Threat Hunting with Bro IDS
• BlackArch Linux is an Arch Linux-based penetration testing distribution for penetration testers and security researchers. The repository contains 2443 tools. You can install tools individually or in groups. BlackArch Linux is compatible with existing Arch installs.
• Stratosphere IPS for Linux is an intrusion prevention system that is based on behavioral detections and machine learning algorithms. Makes use of Zeek.
• Security Onion - Linux distro for intrusion detection, enterprise security monitoring, and log management
• SecTools.Org: Top 125 Network Security Tools - several years old for the newest releases (looks like 2016 is most recent). Doesn't have tools like Suricata.
• Argus s the first network flow system, developed by Carter Bullard in the early 1980's at Georgia Tech, and adopted for cyber security at Carnegie Mellon's Software Engineering Institute in the late 1980's. Network flow technology has become a critical part of modern cyber security and Argus is being used in some of the most important networks in the world. - last code around 2016 though. security links.

Papers:

• Botnet Detection and Prevention inSoftware Defined Networks (SDN) usingDNS Protocol in (IJCSIS) International Journal of Computer Science and Information Security,Vol. 17, No. 5, May 2019

• OpenWebRX -for listening to On-Line SDRs using a web browser. It is a web based server and interface for remotely accessing RTL-SDRs and SDRPlay's. Another link: Open Source SDR Web App for Everyone
• NYC Mesh - community-owned network for fast, affordable and fair access to the Internet - Most of the devices we use, such as a LiteBeam or NanoStation, are self-contained so they have an antenna, radio and ethernet router all in one.

• unDraw - A constantly updated collection of beautiful svg images that you can use completely free and without attribution. From Web Developer Monthly 💻🚀December 2019
• hacker news comments on 33 Amazing Sites with Beautiful Free Icon Sets.

I need to expand on this, but for reference, I found this on reddit - A good C++ (or C, honestly, so long as it works) HTTP server/library, and can be modified to suit:

httperf --hog --num-conns=1024 --num-calls=1 --rate=128 --server localhost --port 8080

Consider Nikto, a web server scanner which performs comprehensive tests against web servers for multiple items, including over 6700 potentially dangerous files/programs, checks for outdated versions of over 1250 servers, and version specific problems on over 270 servers. It also checks for server configuration items such as the presence of multiple index files, HTTP server options, and will attempt to identify installed web servers and software. Scan items and plugins are frequently updated and can be automatically updated.

Another tool for HTTP regression and debugging: siege which is a Debian package supplied by Joe Dog Software.

In my search for an editing environment, I am currently running Visual Studio Code with a number of extensions. It is a GUI based IDE environment and seems to be relatively performant. When jumping to symbol declarations and definitions, it can take a few seconds while performing the lookup.

Since I also use VIM for editing files, I have been keeping my eye on VIM add-ons for creating a console based IDE. Some tools which might be applicable:

• clangd - the language server protocol daemon for clang
• Using LSP & clangd in Vim - notes on integrating clangd, and with a reference at the end about the JSON compilation database, (which in another link, can be supplied via CMake)
• vim cp enhanced highlight - with clangd, I am not sure if this is required, but helps with syntax high-lighting without clangd
• vim-cpp-modern: Enhanced C and C++ syntax highlighting - another syntax highligher, one is forked from the other, with this one being more current, I believe
• VIM CMake - plugin to make working with CMake a little nicer
• CMake Support for Vim - CMake Interoperability in Vim - not sure what the difference is to the previous link
• Vim Cmake integration - some chatter on StackOverflow on integrating CMake with VIM

NeoVim

• neovim
• clangd with neovim

• Proxmox Ceph Server
• Manage Ceph Services on Proxmox VE Nodes
• Manage Ceph Services on Proxmox VE Nodes - reformatted copy of above link
• Proxmox VE Ceph Benchmark 2018/02 with a referral to Benchmark Proxmox VE Ceph Cluster Performance
• Install Ceph Server on Proxmox VE - video tutorial
• Ceph PGs per Pool Calculator

• As Ceph handles data object redundancy and multiple parallel writes to disks (OSDs) on its own, using a RAID controller normally doesn’t improve performance or availability. On the contrary, Ceph is designed to handle whole disks on it’s own, without any abstraction in between. RAID controller are not designed for the Ceph use case and may complicate things and sometimes even reduce performance, as their write and caching algorithms may interfere with the ones from Ceph.
• Ceph Object Storage Daemons are storing objects for Ceph over the network. It is recommended to use one OSD per physical disk.
• We recommend a Ceph cluster size, starting with 12 OSDs, distributed evenly among your, at least three nodes (4 OSDs on each node).

On my Debian desktop, I have both of my primary monitors in portrait mode, with a third monitor in landscape mode. The login screen is therefore rotated 90 degrees from how it needs to be. After login, I need to manually go into System Settings, and manually rotate the monitors.

That is, up until now. A little poking around says I need to:

apt install arandr

This is a GUI application which will create a script in .screenlayout which can be auto-started upon login:

$ cat .screenlayout/bythree.sh
#!/bin/sh
xrandr \
  --output DisplayPort-0 --primary --mode 3840x2160 --pos 0x8 --rotate right \
  --output DisplayPort-1 --mode 3840x2160 --pos 2160x0 --rotate right \
  --output DisplayPort-2 --off \
  --output DisplayPort-3 --mode 2560x1600 --pos 4320x0 --rotate normal \
  --output HDMI-A-0 --off \
  --output HDMI-A-1 --off

This can be autostarted in LXDE with:

$ cat ~/.config/lxsession/LXDE/autostart
@lxpanel --profile LXDE
@pcmanfm --desktop --profile LXDE
@xscreensaver -no-splash
#@~/.screenlayout/bythree.sh    <= does not work
#@${HOME}/.screenlayout/bythree.sh   <= does not work
# make sure there is a line return at end of command:
@/home/me/.screenlayout/bythree.sh

Instructions for the autostart file can be found at LXSession.

Continuing on in the search for a responsive IDE for building large C++ codesets with CMake, the next stop is Visual Studio Code.

The initial install supplies a basic IDE editing environment.

Usability occurs when extensions are loaded. I have the following installed (versions are as of this writing):

• C/C++ for Visual Studio Code, v0.26, by Microsoft <== some sites say to disable this, but it is required by the debug function
• CMake, v0.0.17, by twxs, which provides CMake language support
• CMake Tools, v1.2.3, by Microsoft, which provides the build capability
• vscode-clangd, v0.0.19, is the clang language server, which provides code completion and symbol tables

Prior to installation of the extensions, on Debian, I installed the following packages first (in addition to the standard compilers):

• cmake
• clangd
• clangd-9

reddit - PROTIP: Use clangd instead of the official C/C++ extension suggests adding the following to .vscode/settings.json:

"C_Cpp.autocomplete": "Disabled",
"C_Cpp.formatting": "Disabled",
"C_Cpp.errorSquiggles": "Disabled",
"C_Cpp.intelliSenseEngine": "Disabled",

In addition, I have a more recent version of clangd, so in .vscode/settings.json, I also have:

"clangd.path": "/usr/lib/llvm-9/bin/clangd",

My over all file looks like:

{
  "clangd.path": "/usr/lib/llvm-9/bin/clangd",
  "C_Cpp.autocomplete": "Disabled",
  "C_Cpp.formatting": "Disabled",
  "C_Cpp.errorSquiggles": "Disabled",
  "C_Cpp.intelliSenseEngine": "Disabled",
  "C_Cpp.default.intelliSenseMode": "clang-x64",
  "editor.tabSize": 2
}

In the root directory of the project, a link is required (the setting "compileCommands" in .vscode/c_cpp_properties.json does not appear to be used by the clangd module) :

ln -s build/compile_commands.json .

As a note, if compile_commands.json is not provided, then the following flag needs to be passed to CMake (seems to be defaulted "on" in current Visual Studio Code):

-DCMAKE_EXPORT_COMPILE_COMMANDS=1

Documentation for clangd is found at Getting started with clangd.