TLS handshake fails with GNUTLS_E_RANDOM_FAILED

Logs show this error: ocserv[3886]: GnuTLS error (at worker-vpn.c:817): Failed to acquire random data.

Root cause appears to be

uname -a
Linux OLVCT2007200721 3.10.0-514.28.1.el7.x86_64 #1 SMP Fri Jul 7 12:58:19 EDT 2017 x86_64 x86_64 x86_64 GNU/Linux
cat /etc/os-release
NAME="Red Hat Enterprise Linux Server"
VERSION="7.3 (Maipo)"
ID="rhel"
ID_LIKE="fedora"
VERSION_ID="7.3"
PRETTY_NAME="Red Hat Enterprise Linux"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:redhat:enterprise_linux:7.3:GA:server"
HOME_URL="https://www.redhat.com/"
BUG_REPORT_URL="https://bugzilla.redhat.com/"

REDHAT_BUGZILLA_PRODUCT="Red Hat Enterprise Linux 7"
REDHAT_BUGZILLA_PRODUCT_VERSION=7.3
REDHAT_SUPPORT_PRODUCT="Red Hat Enterprise Linux"
REDHAT_SUPPORT_PRODUCT_VERSION="7.3"

Root cause appears to be that getrandom syscall is not present on RHEL 7.3 and GnuTLS fallback to /dev/urandom fails in the worker process, exact root cause unknown).