Ansible where do PreferredAuthentications SSH settings come from?

Question

I'm running a standard ansible (v2.3.1) playbook using SSH username and password settings. When using the '-vvvv' setting i can see these SSH commands getting generated

EXEC ssh -C -o ControlMaster=auto -o ControlPersist=60s 
-o StrictHostKeyChecking=no -o Port=2222 
-o KbdInteractiveAuthentication=no 
-o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey 
-o PasswordAuthentication=no -o User=dc_user -o ConnectTimeout=10

In the case above, where are the 'PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey' settings getting pulled from. I believe these come from the client SSH config settings but is this correct?

I understand that i can override the ssh arguments by defining this in my 'ansaible.cfg'

[ssh_connection]
scp_if_ssh=True
ssh_args = -o ControlMaster=auto -o ControlPersist=60s -o PreferredAuthentications=publickey

Can someone explain this to me? Thanks

Solution

I'm observe that -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey is hard coded in the source code

If you override ssh_args in ansible.cfg to -o PreferredAuthentications=publickey is added to the ssh command line but this doesn't replace -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey

Example:

$ grep ssh_args /etc/ansible/ansible.cfg 
#ssh_args = -C -o ControlMaster=auto -o ControlPersist=60s
ssh_args = -o ControlMaster=auto -o ControlPersist=60s -o     PreferredAuthentications=publickey
$ ansible rhel7a -m ping -vvvv |grep EXEC
<rhel7a> SSH: EXEC ssh -vvv -o ControlMaster=auto -o ControlPersist=60s -o PreferredAuthentications=publickey -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o User=vagrant -o ConnectTimeout=10 -o ControlPath=/home/user/.ansible/cp/13dd447a86 rhel7a '/bin/sh -c '"'"'echo ~ && sleep 0'"'"''