Description of problem:

The write_prometheus plugin of collectd fails to start. Checking audit.log, it looks like SELinux is preventing collectd to listen on port 9103.

Version-Release number of selected component (if applicable):

Kernel: 4.16.9-300.fc28.x86_64
collectd: 5.8.0-8.fc28
collectd-write_prometheus: 5.8.0-8.fc28

How reproducible:

Always

Steps to Reproduce:

1. Install the following packages: collectd collectd-write_prometheus
2. Update /etc/collectd.conf to enable the write_prometheus plugin.
  LoadPlugin syslog
  LoadPlugin cpu
  LoadPlugin interface
  LoadPlugin load
  LoadPlugin memory
  LoadPlugin write_prometheus
  <Plugin write_prometheus>
        Port "9103"
  </Plugin>
  Include "/etc/collectd.d"
3. Start collectd.

Actual results:

collectd doesn't expose any metric on port 9103. The collectd logs show that the service fails to bind on port 9103.

Jun 13 14:27:07 localhost.localdomain collectd[23781]: plugin_load: plugin "memory" successfully loaded.
Jun 13 14:27:07 localhost.localdomain collectd[23781]: plugin_load: plugin "write_prometheus" successfully loaded.
Jun 13 14:27:07 localhost.localdomain collectd[23781]: Systemd detected, trying to signal readyness.
Jun 13 14:27:07 localhost.localdomain collectd[23781]: write_prometheus plugin: Opening a listening socket failed.
Jun 13 14:27:07 localhost.localdomain collectd[23781]: write_prometheus plugin: MHD_start_daemon() failed.
Jun 13 14:27:07 localhost.localdomain collectd[23781]: Initialization of plugin `write_prometheus' failed with status -1. Plugin will be unloaded.
Jun 13 14:27:07 localhost.localdomain collectd[23781]: plugin_unregister_read: No such read function: write_prometheus
Jun 13 14:27:07 localhost.localdomain systemd[1]: Started Collectd statistics daemon.
Jun 13 14:27:07 localhost.localdomain collectd[23781]: Error: one or more plugin init callbacks failed.
Jun 13 14:27:07 localhost.localdomain collectd[23781]: Initialization complete, entering read-loop.

And audit.log reports the AVC denial:

type=AVC msg=audit(1528892827.529:234): avc:  denied  { name_bind } for  pid=23781 comm="collectd" src=9103 scontext=system_u:system_r:collectd_t:s0 tcontext=system_u:object_r:bacula_port_t:s0 tclass=tcp_socket permissive=0
type=AVC msg=audit(1528892827.529:235): avc:  denied  { name_bind } for  pid=23781 comm="collectd" src=9103 scontext=system_u:system_r:collectd_t:s0 tcontext=system_u:object_r:bacula_port_t:s0 tclass=tcp_socket permissive=0


Expected results:

The write_prometheus plugin should start and serve the metrics on port 9103.

Additional info:

I'm not sure whether this bug should be filed against SELinux or collectd. Feel free to redirect.