[...]

quoted

here I added nested bridge attributes to IFLA_AF_SPEC and pass them down
to the drivers as needed. Should we merge these two sets so that we have
only a single nested set of bridge attributes? Either in IFLA_AF_SPEC or
IFLA_PROTINFO.

[...]

This is an area where there is no clear choice.
I would like to keep AF_UNSPEC for non-protocol stuff,
that is why I targeted PF_BRIDGE:IFLA_PROTINFO.

Works for me.

Other alternative would be to add sysctl which is less message
based, but is more general. (ie. /default and /all are available).

I would just assume use netlink seeing this is common for all the other
networking bits and any networking app is already likely to be handling
these events.

.John