Use in-kernel support for DNS lookup

configname: CONFIG_CEPH_LIB_USE_DNS_RESOLVER

Linux Kernel Configuration
└─>Networking support
└─>Use in-kernel support for DNS lookup
In linux kernel since version 3.1 (release Date: 2011-10-24)  
If you say Y here, hostnames (e.g. monitor addresses) will
be resolved using the CONFIG_DNS_RESOLVER facility.

For information on how to use CONFIG_DNS_RESOLVER consult