My system was upgraded to lighttpd 1.4.68-1 in the last few days.
I quickly noticed issues. Many connections dropped with no log entry in either access.log or error.log
Watching via tcpdump showed the connections trying and failing.
Also there was an issue with random 100% CPU usage that required restarting lighttpd to fix.
Dropping back to the previous build fixed all the issues.
Checked the change log for 1.4.68 on the lighttpd website.
Noticed that one of the changes was turning on KTLS
This led me to believe that the error was with KTLS. This made sense as clearly the missed connections were failing someplace outside of lighttpd and thus not being logged.
I add "Options" => "-KTLS" to ssl.openssl.ssl-conf-cmd in lighttpd's conf. That fixed the problem.
I do not know how many other systems this affects.
my system is a PCduino3 nano with an AllWinner A20 SoC, 1GHz ARM Cortex A7 Dual Core processor.
If it is a common problem building with KTLS disabled might be an option.