News items for tag rant - Koos van den Hout

2020-07-15 I tamed systemd
I shared my earlier mishap with systemd on twitter: @khoos: Another run-in with systemd and got a reply to check the prerequisites: @devbeard: Is there something that needs to come after, before the thing is there for gpsctl to configure? and I added a dependency on the serial driver for the right port.

This seems to work now, it all comes up as planned. Updated file /etc/systemd/system/ublox-init.service:
[Unit]
Description=u-blox initialisation
Before=gpsd.service
Before=ntp.service
Requires=sys-devices-platform-soc-3f201000.serial-tty-ttyAMA0.device

[Service]
Type=oneshot
ExecStart=/usr/local/bin/gpsctl -q -a -B 115200 --configure_for_timing

[Install]
WantedBy=multi-user.target
And now I'm greeted by a working ntpd at 115200 bps when I log in to the Pi.

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2020-07-04 Again with systemd in the new GPS Pi
Again and again systemd annoys me. This time in the GPS Pi configured for timing.

Since I want it to work perfectly at start I added the systemd rules as suggested by A Raspberry Pi Stratum 1 NTP Server - Phil's Occasional Blog with /etc/systemd/system/ublox-init.service containing:
[Unit]
Description=u-blox initialisation
Before=gpsd.service
Before=ntp.service

[Service]
Type=oneshot
ExecStart=/usr/local/bin/gpsctl -q -a -B 115200 --configure_for_timing

[Install]
WantedBy=multi-user.target
After reboot ntp was running, but no data at all from the gps unit, and gpsctl was unable to revive it. The solution was to disable the above unit and ntpd, powerdown and restart the whole system and try again. After that doing the changes by hand and starting ntpd worked fine.

It's probably some sort of race condition, but any time I try to make a system with systemd do something reliably I run into things like this.

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2020-07-02 My social media accounts
Social media is a nice and easy way to interact with people. There was and is a lot of choice in social media. Ages ago I started with fidonet echomail groups, later with usenet and recently with web-based social media.

But that's also a development from volunteer-run systems to commercially run systems. Companies like twitter, google and facebook are in the world to make a profit. With echomail and usenet the protocols and software were not linked to the operator of the service, someone else was able to run the same service and allow access to the network again. When google+ stopped the ties to people I knew were broken and I had to find them again on other networks.

I am somewhat active on twitter. My 'main' twitter account is twitter.com/khoos but I was getting a lot of negative messages about world politics which got depressing. Since twitter has made it a lot easier to manage more than one twitter account from the twitter web interface I decided to add a specific account for amateur radio with the predictable name twitter.com/PE4KH. Amateur radio twitter is not completely free of politics, but it's a lot more sane view of twitter.

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2020-04-07 Troy Hunt: No I won't link to your spammy article
A recurring theme in rants here: link request spam written to look like a serious and personal request to improve an article on my site.

Troy Hunt seems to get a lot of those too, so he wrote No, I Won't Link to Your Spammy Article.

So we can now all stop doing stupid 'search engine optimization' and go back to sharing actual good content.

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2020-03-25 It's 2020 and github doesn't support IP version 6
Several of the machines here at home have IPv4 to the outside world disabled, simply to find every ancient service or program that still lives in the old world. Today I found one of those while installing dehydrated to automatically renew Let's Encrypt certificates.

Indeed, github has no IPv6 support. It tries to be a modern service, but lacks an AAAA record.

The solution is simple: use a webproxy to solve this. The only reason I still have a squid webproxy running is to be able to access IPv4-only http/https services from those hosts, so setting the http proxy in the global git config helped. I'm just surprised github doesn't support IPv6.

Update: After some searching I found Github users have been asking about IPv6 connectivity since at least 2018 and the "solution" is that they currently don't support IPv6 and the request is on some list.

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2019-06-18 Scriptkiddies being especially stupid
Cybercriminal Checking how fail2ban was doing on a wordpress site I noticed the following error in the log:
46.105.99.163 - - [18/Jun/2019:09:03:46 +0200] "GET /wp-content/plugins/ungallery/source_vuln.php?pic=../../../../../wp-config.php HTTP/1.1" 404 15933 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:64.0) Gecko/20100101 Firefox/64.0"
which is never going to work as an exploit. A full explanation in Hackers Will Try To Exploit Vulnerabilities in WordPress Plugins in Ways That Will Never Succeed - Plugin Vulnerabilities but this entire attempt is based on just the description of a vulnerability and can never ever have succeeded, not even on a system with the vulnerable version of the ungallery plugin.

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2019-04-12 Corel spam
It seems Corel graphics still exists and part of their continued existance is sending out spam to unverified e-mail addresses. With the included lie:
You are receiving this email because you requested to receive information regarding Corel products and special offers or you subscribe to a Corel e-newsletter.
No I haven't.

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2018-12-30 First annoyance with systemd on thompson
On reinstalling thompson I was not sure whether to pick ubuntu (with lots of package support for amateur radio) or devuan (without systemd). I chose ubuntu to keep access to lots of amateur radio packages but as expected the first systemd problem already got me. Names in the internal network with RFC1918 addresses weren't resolvable.

After some searching I found out systemd-resolved had decided the last nameserver advertised via IPv6 was the one to use. As I could not find a lot of information on how to do the ordering I just decided to kick it all out and switch to normal resolving. Some searching found How to disable systemd-resolved in Ubuntu? - ask ubuntu which has the right steps. Back to somewhat normal, the next step is to convince NetworkManager to use IPv6 resolving before IPv4.

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2018-12-07 Trying to kick spamassassin and perl into the 21st century and prefer IPv6 for DNS traffic
Or in short: Perl considered harmful

I want applications to use and prefer IPv6 whenever possible, so I have a /etc/resolv.conf with IPv6 addresses of the nameserver(s) listed first. But I noticed queries from the spamassassin processes still coming in over the legacy IP protocol. Even when listing them in order in /etc/spamassassin/local.cf spamassassin prefers IPv4. And I want it to prefer IPv6 without leaving out IPv4. I like the redundancy but I want to change the preference. Also: I only want to maintain the list of nameservers in /etc/resolv.conf and not in other locations.

I wrote a simple test program to understand what the perl Net::DNS::Resolver is doing. With a standard test program like:
#!/usr/bin/perl -wT

use strict;
use Net::DNS;
my $resolver = new Net::DNS::Resolver();

print join ' ', $resolver->nameservers();

print "\n";
The IPv4 addresses will be listed first, independent of the order in /etc/resolv.conf. Only after changing to:
#!/usr/bin/perl -wT

use strict;
use Net::DNS;
my $resolver = new Net::DNS::Resolver();
$resolver->prefer_v6(1);

print join ' ', $resolver->nameservers();

print "\n";
I will see the IPv6 resolver listed first. But now to convince spamassassin to do the same. Browsing the Net::DNS::Resolver shows the RES_OPTIONS="inet6" option but does not document it. This option confuses spamassassin when starting:
export RES_OPTIONS="inet6"
root@gosper:/etc/default# service spamassassin restart
Restarting SpamAssassin Mail Filter Daemon: Bad arg length for NetAddr::IP::Util::mask4to6, length is 128, should be 32 at /usr/lib/x86_64-linux-gnu/perl5/5.24/NetAddr/IP/Lite.pm line 647.
Compilation failed in require at /usr/lib/x86_64-linux-gnu/perl5/5.24/NetAddr/IP.pm line 8.
BEGIN failed--compilation aborted at /usr/lib/x86_64-linux-gnu/perl5/5.24/NetAddr/IP.pm line 8.
Compilation failed in require at /usr/share/perl5/Mail/SpamAssassin/Util.pm line 70.
BEGIN failed--compilation aborted at /usr/share/perl5/Mail/SpamAssassin/Util.pm line 70.
Compilation failed in require at /usr/share/perl5/Mail/SpamAssassin/Conf.pm line 85.
BEGIN failed--compilation aborted at /usr/share/perl5/Mail/SpamAssassin/Conf.pm line 85.
Compilation failed in require at /usr/share/perl5/Mail/SpamAssassin.pm line 71.
BEGIN failed--compilation aborted at /usr/share/perl5/Mail/SpamAssassin.pm line 71.
Compilation failed in require at /usr/sbin/spamd line 240.
BEGIN failed--compilation aborted at /usr/sbin/spamd line 240.
So that was a bad idea and is not the answer. Looking at the resolv.conf manpage shows that the option indeed does different things which explains why that was wrong.
  inet6  Sets RES_USE_INET6 in _res.options.  This has the
		 effect of trying an AAAA query before an A query inside
		 the gethostbyname(3) function, and of mapping IPv4
		 responses in IPv6 "tunneled form" if no AAAA records
		 are found but an A record set exists.  Since glibc
		 2.25, this option is deprecated; applications should
		 use getaddrinfo(3), rather than gethostbyname(3).
So if I want perl programs to do what I want, I have to change every one of them to set $resolver->prefer_v6(1);. There is no sane default or a global "get into the 21st century" flag.

Changing /usr/share/perl5/Mail/SpamAssassin/DnsResolver.pm to include $res->prefer_v6(1); does help, but will need to be redone when updating spamassassin.

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2018-11-28 Using mice adopted to my hands
The old rsi problem was acting up again, just like I had RSI in 1999.

One of the things I now did was add a left-side mouse on the linux desktop at home. I have used a left-side mouse for a number of years on a linux desktop and used the instructions from the xmodmap manpage:
       Many  pointers are designed such that the first button is pressed using
       the index finger of the right hand.  People who  are  left-handed  fre‐
       quently  find  that  it is more comfortable to reverse the button codes
       that get generated so that the primary  button  is  pressed  using  the
       index  finger  of  the  left  hand.   This  could be done on a 3 button
       pointer as follows:
       %  xmodmap -e "pointer = 3 2 1"
But I now have two USB mice, one with a forward/backward button and a clearly right-handed design and one simple one on the left. And it is possible to selectively swap mouse buttons on only one input device with xinput.

The list of all inputs:
koos@thompson:~$ xinput list
⎡ Virtual core pointer                          id=2    [master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]
⎜   ↳ Logitech USB-PS/2 Optical Mouse           id=9    [slave  pointer  (2)]
⎜   ↳ Logitech Optical USB Mouse                id=10   [slave  pointer  (2)]
⎣ Virtual core keyboard                         id=3    [master keyboard (2)]
    ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]
    ↳ Power Button                              id=6    [slave  keyboard (3)]
    ↳ Power Button                              id=7    [slave  keyboard (3)]
    ↳ Burr-Brown from TI               USB Audio CODEC  id=8    [slave  keyboard (3)]
    ↳ VIA Technologies Inc. USB Audio Device    id=11   [slave  keyboard (3)]
    ↳ daskeyboard                               id=12   [slave  keyboard (3)]
    ↳ daskeyboard                               id=13   [slave  keyboard (3)]
    ↳ Dell WMI hotkeys                          id=14   [slave  keyboard (3)]
Setting the button order happens with xinput set-button-map which needs an ID. Solution in .xsession:
xinput set-button-map $(xinput list --id-only "Logitech Optical USB Mouse") 3 2 1

Oh, and in that other operating system I use (Windows) one of the problems is the user can't set mouse button order per device. And technical specifications of left-handed mice do not list whether the buttons are swapped in hardware.

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IPv6 check

Running test...
, reachable as koos+website@idefix.net. PGP encrypted e-mail preferred. PGP key 5BA9 368B E6F3 34E4 local copy PGP key 5BA9 368B E6F3 34E4 via keyservers

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