At some point libvirtd on igloo, the machine which hosts mail and a number of shell servers, failed.  Libvirtd is the server side virtualization management daemon, it is responsible for starting, stopping, arranging networking, storage, and system resources for kvm/qemu guests (also for xen but we aren’t using xen here).

     This affected a number of machines including mail and because every server NFS mounts the mail spool from mail, it affected them indirectly.

     The message that Igloo gave in syslog relating to libvirt was:

        libvirtd[2271]: internal error: wrong nlmsg len

     The “nlmsg” refers to Netlink, so it would appear something went wrong in networking and libvirtd didn’t know how to handle it and crashed.

     I don’t know exactly how long and how deep the outage was since it was kind of a gradual deterioration situation after libvirtd crashed.  I was going to add an automatic restart to libvirtd in systemd to prevent this specific failure in the future but found it was already in place but incompletely specified so perhaps systemd choked.  I have corrected that.

     I received about eight tickets on this issue, and I really appreciate it that the ticket system is being used, but also with outages of this magnitude a phone call would be good because if I’m not actively at the terminal I may not be aware of issues.

     Rust is a new compiled programming language that users a new memory
management scheme.

     I first learned several assembly languages and then learned C, and because I learned assembly first and thus really think in terms of what the hardware does, I have not had issues with array bounds or de-referenced pointers but a lot of people have. In fact this tends to be what causes the majority of privilege escalation exploits.

     Many languages, Java, Python, Perl, BASIC, etc solved this by using a memory management technique known as garbage collection but this method has severe performance issues. First, it can be difficult for the language to determine if a particular variable will ever be accessed again, thus memory release may be very delayed resulting in wasted memory. But more significant is that garbage collection causes periodic halts in execution that can be very annoying.

     Enter rust, they invented a new method of memory management in which you declare to the compiler how memory is used, in what contexts and time frames, and this enables the compiler to manage memory much as you would do by hand without the human error component.

     This makes Rust an ideal replacement for C, for those who are less disciplined, and for critical tasks, because, like C, it can approach assembler in efficiency, doesn’t introduce the periodic lags of garbage collection, and yet protects you against buffer overruns and pointer de-reference errors.  Now if they will only invent a text editor that corrects run-on sentences.

     I’ve installed the rust compiler rustc on all of the shell servers and working on installing it on the other machines as it will be necessary in the future for kernel compilation.

     The newest version is on Fedora and Rocky8, 1.80, slightly older versions on Ubuntu, and Zorin, 1.75, and even older versions on Debian and MxLinux 1.65.