I see this description in mongoDB officail mannual:
"If you are connecting to a system whose hostname *does not match *the Kerberos name, use --gssapiHostName to specify the Kerberos FQDN that it responds to."

so I run the mongo shell:
administrator@mon:~$ mongo --host 10.154.10.100 --authenticationMechanism=GSSAPI --authenticationDatabase='$external' --username user1@KER.COM --gssapiHostName mon.ker.com

and it works.

but when I try to wrote program with mongo c driver(V 1.7.0), I found there's no parameter corresponding to "gssapiHostName".

so my problem is:
how could I specify the "gssapiHostName" in the following connection string?
auto client = mongocxx::client{ mongocxx::uri

};