samba4 provision dns.keytab generation howto?

[Gémes Géza]

Hi,

I would like to add (to samba-tool) the ability to export keytabs for
individual user/spn-s.
For that I've started studying the code to figure out how the dns.keytab
is generated.
Unfortunately I couldn't go past
source4/scripting/python/samba/provision/__init__.py :-(
What I've found: source4/libnet/libnet_export_keytab.c doesn't accept as
a parameter anything user/spn related and thus exports the whole secrets
database.

Thank you for any pointers to the C/Python code which does
creates/exports the dns.keytab.

Cheers

Geza