Description of problem:

I'm trying to run knot-resolver out of EPEL on CentOS 7.4.1708. Systemd opens a socket for it, but the daemon never starts, leaving these error messages in syslog:

   kresd: [system] bind to '127.0.0.1@53' Permission denied
   kresd: [system] bind to '::1@53' Permission denied

Which is weird, because the systemd unit files shipped in the package set up socket activation, which (according to the documentation at https://knot-resolver.readthedocs.io/en/stable/daemon.html#running-supervised ) should work automatically.

Looking at the source code, the socket activation code is within "#ifdef HAS_SYSTEMD" guards. Looking at the Makefile, this #define is set if libsystemd of version 227 or above is detected. This test was added in commit 50eebc07, in august of 2016 (first released in knot-resolver-1.1.0), with the comment that the sd_listen_fds_with_names() function call requires this version. CentOS 7 has version 219:

   $ rpm -qf /usr/lib64/libsystemd.so
   systemd-devel-219-42.el7_4.4.x86_64

Sure enough, when I fetch the SRPM and rebuild it, the Makefile does not detect systemd:

   [no] systemd (daemon)

Version-Release number of selected component (if applicable): knot-resolver-1.5.0-1.el7.x86_64

How reproducible: Always

Steps to Reproduce:
1. yum -y install bind-utils knot-resolver-1.5.0-1.el7.x86_64
2. systemctl start kresd.socket
3. dig @localhost a a.root-servers.net

Actual results:

kresd doesn't start.

dig fails:
   ;; connection timed out; no servers could be reached

/var/log/messages contains:
   kresd: [system] bind to '127.0.0.1@53' Permission denied
   kresd: [system] bind to '::1@53' Permission denied
   [...]
   systemd: start request repeated too quickly for kresd.service
   systemd: Failed to start Knot DNS Resolver daemon.
   systemd: Unit kresd.socket entered failed state.
   systemd: kresd.service failed.


Expected results:

kresd should start and answer the query.


Additional info:

I assume an updated systemd isn't possible for CentOS, so can we get a unit file that starts kresd as a normal daemon instead of using socket activation?