- New requirements in Libreswan 3.18 (not released yet)
- libsystemd-dev (Ubuntu/Debian) or systemd-devel (CentOS)
- Applies only to systemd-based Linux distributions
- Libevent2 is newly available in CentOS 6 as of May 12
- No longer need to install from download.libreswan.org
- Remove libevent-devel before install to avoid conflicts
- Thanks to Thomas C for reporting this issue