Replacing IPv6 port labeling with CALIPSO in Smack

[Casey Schaufler <casey@schaufler-ca.com>]

I am looking at CALIPSO support for Smack. CALIPSO provides
the same sort of network packet labeling for IPv6 that CIPSO
provides for IPv4. Because most of the details are buried in
the Netlabel code this should be reasonably straight forward.
The complication is that Smack has two mechanisms in place
for labeling IPv6 already, and neither uses anything like
CALIPSO packet labeling. If CONFIG_SECURITY_SMACK_NETFILTER
is defined Smack secids are sent via the netfilter secmark.
Otherwise, the Smack label of the process creating a socket
is maintained in a table indexed by the port number.

My proposed change would make the IPv6 labeling match the IPv4
labeling. The entire port number scheme would be abandoned.
The current secmark scheme would continue to be used if it
is configured. Whereas today IPv6 labeling is only supported
locally, the new code would support labeling remote systems as
well.

Systems that use CONFIG_SECURITY_SMACK_NETFILTER should be
unaffected for local use. The host address labeling scheme
would be retained, so any system configured to use IPv6
externally shouldn't see a difference. Systems that don't
use the option should also work the same as they do today.

Are there any users of Smack that use IPv6 but do not use
CONFIG_SECURITY_SMACK_NETFILTER? Does anyone have, know of
or imagine a use case where CALIPSO labeling would not be
a viable replacement for the hackish "port labeling"?

Thank you.