Ever since I started working with multicast back in the early 2000's, I've had to make my own tools. There weren't that many useful ones available, at least not in the Open Source space where I worked.
The first tool made, mcjoin,
was based on an example an IBM'er had made public. I used that, the
standard ping(1) tool, and tcpdump(1), to check my multicast flows.
When I started out learning about libnl, around 10 years ago, I did not fully understand it. Mostly because I didn't (want to) understand Netlink. A great way to learn something is to try to fix a bug, or develop a new feature, because then you will want to write both tests and demo applications, which you may end up having to debug! Debuggers give you backtraces, which will help you understand how your program works.
> Note: for debugging embedded systems using gdb-server, see the following blog post I wrote
| #BR2_ROOTFS_OVERLAY := $(BR2_ROOTFS_OVERLAY) $(BR2_EXTERNAL_NETBOX_PATH)/jocke | |
| LINUX_OVERRIDE_SRCDIR = /home/jocke/src/linux | |
| #IPROUTE2_OVERRIDE_SRCDIR = /home/jocke/src/iproute2 | |
| #MDIO_TOOLS_OVERRIDE_SRCDIR = /home/jocke/src/github.com/jocke/mdio-tools | |
| #MDIO_TOOLS_AUTORECONF = YES | |
| #PLY_OVERRIDE_SRCDIR = /home/jocke/src/github.com/jocke/ply | |
| #PLY_AUTORECONF = YES | |
| #TCPDUMP_OVERRIDE_SRCDIR = /home/jocke/src/github.com/the-tcpdump-group/tcpdump | |
| #LIBPCAP_OVERRIDE_SRCDIR = /home/jocke/src/github.com/the-tcpdump-group/libpcap |
Standard escape codes are prefixed with Escape:
^[\033\u001b\x1B27
| Marvell>> printenv | |
| baudrate=115200 | |
| bootargs=console=ttyS0,115200 root=/dev/nfs rw ip=0.0.0.0:0.0.0.0:10.4.50.254:255.255.255.0:marvell:eth0:none nfsroot=0.0.0.0:/srv/nfs/ | |
| bootcmd=run get_env; run get_images; run set_bootargs; booti $kernel_addr $ramfs_addr $fdt_addr | |
| bootdelay=2 | |
| console=console=ttyS0,115200 | |
| eth1addr=00:51:82:11:22:01 | |
| eth2addr=00:51:82:11:22:02 | |
| eth3addr=00:51:82:11:22:03 | |
| ethact=mvpp2-0 |
| #!/bin/sh -x | |
| # Sets up a complete network world inside a network namespace | |
| ns=world | |
| ip netns add $ns | |
| for i in 1 2 3 4; do | |
| ip netns exec $ns ip link add eth$i type veth peer p$i | |
| done |
TCL-Expect scripts are an amazingly easy way to script out laborious tasks in the shell when you need to be interactive with the console. Think of them as a "macro" or way to programmaticly step through a process you would run by hand. They are similar to shell scripts but utilize the .tcl extension and a different #! call.
The first step, similar to writing a bash script, is to tell the script what it's executing under. For expect we use the following:
#!/usr/bin/expect
| /* Read kernel IPv4 routes from main routing table | |
| * | |
| * Copyright (c) 2021 Joachim Wiberg <troglobit@gmail.com> | |
| * | |
| * Permission to use, copy, modify, and/or distribute this software for any | |
| * purpose with or without fee is hereby granted, provided that the above | |
| * copyright notice and this permission notice appear in all copies. | |
| * | |
| * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES | |
| * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
| # ~/.config/gtk-3.0/settings.ini | |
| [Settings] | |
| gtk-icon-theme-name = Adwaita-dark | |
| gtk-theme-name = Adwaita-dark | |
| gtk-font-name = DejaVu Sans 11 |
| -- Copy from /etc/xdg/awesome/rc.lua to .config/awesome/rc.lua | |
| -- | |
| -- My additions | |
| local r = require("runonce") | |
| ... | |
| -beautiful.init(gears.filesystem.get_themes_dir() .. "default/theme.lua") | |
| +beautiful.init(gears.filesystem.get_themes_dir() .. "zenburn/theme.lua") | |
| ... | |
| - }, properties = { titlebars_enabled = true } |