Petr Machata [off-list ref] writes:

Jakub Kicinski [off-list ref] writes:

quoted

On Mon, 3 Oct 2022 09:52:59 +0200 Petr Machata wrote:

quoted

I assumed the policy is much more strict with changes like this. If you
think it's OK, I'm fine with it as well.

The userspace (lldpad in particular) is doing the opposite thing BTW:
assuming everything in the nest is a DCB_ATTR_IEEE_APP. When we start
emitting the new attribute, it will get confused.

Can you add an attribute or a flag to the request which would turn
emitting the new attrs on?

The question is whether it's better to do it anyway. My opinion is that
if a userspace decides to make assumptions about the contents of a TLV,
and neglects to validate the actual TLV type, it's on them, and I'm not
obligated to keep them working. We know about this case, but really any
attribute addition at all could potentially trip some userspace if they
expected something else at this offset.

And re the flag: I think struct dcbmsg.dcb_pad was meant to be the place
to keep flags when the need arises, but it is not validated anywhere, so
we cannot use it. It could be a new command, but I'm not a fan. So if we
need to discriminate userspaces, I think it should be a new attribute.