All of a sudden, the PdeS IRC channel wasn't working anymore. As inexplicable as this sudden disruption first appeared to be, as obvious are the reasons in hindsight. What has happened?
At August 18, apt offered an InspIRCd update, dutifully asking whether I wanted to keep the configuration files. I didn't realize at this moment that the update was in fact the upgrade from version 2 to 3 I had been waiting for since May. As a matter of fact, this update is disruptive and requires one to carefully review and modify the configuration of InspIRCd. Well, I failed to do that, and I also failed to notice that the InspIRCd service didn't restart after the update.
Sometimes people jokingly remark that I should work as a system or network admin rather than as a scientist. This incident shows that I'm not qualified for such a job. I'm way too careless.
In any case, I now had to find the reason for the InspIRCd service to quit. It wasn't too difficult, but a multi-step procedure. The first obstacle was an outdated apparmor profile, which allowed InspIRCd to write in /run, but not in /run/inspircd. That was easily fixed.
The second was the TLS configuration of our channel. I took the opportunity to renew our certificate and to altogether strengthen the security of the channel, but it took me a while to realize that the identifier in the bind_ssl and sslprofile_name tags has to be one and the same (it isn't in the documentation!).
<bind address="" port="6697" type="clients" ssl="pdes"> <module name="ssl_gnutls"> <sslprofile name="pdes" provider="gnutls" certfile="cert/cert.pem" keyfile="cert/key.pem" dhfile="cert/dhparams.pem" mindhbits="4096" outrecsize="4096" hash="sha512" requestclientcert="no" priority="PFS:+SECURE256:+SECURE128:-VERS-ALL:+VERS-TLS1.3">
Well, the channel is up again, more secure than ever. Fire away. 😅