On Thu, 2020-10-01 at 08:41 -0700, Jakub Kicinski wrote:
> > Even if I don't have a good idea now on how to avoid the duplication, it
> > might be nicer to have a (flag) attribute here for "CTRL_ATTR_ALL_OPS"?
>
> Hm. How would you see the dump structured?
Yeah, that's the tricky part ... Hence why I said "I don't have a good
idea now" :)
> We need to annotate the root
> policies with the command. Right now I have:
>
> [ATTR_FAMILY_ID]
> [ATTR_OP]
> [ATTR_POLICY]
> [policy idx]
> [attr idx]
> [bla]
> [bla]
> [bla]
>
> But if we're dumping _all_ the policy to op mapping is actually 1:n,
> so we'd need to restructure the dump a lil' bit and have OP only
> reported on root of the policy and make it a nested array.
So today you see something like
[ATTR_FAMILY_ID]
[ATTR_POLICY]
[policy idx, 0 = main policy]
[bla]
...
...
I guess the most compact representation, that also preserves the most
data about sharing, would be to do something like
[ATTR_FAMILY_ID]
[ATTR_POLICY]
[policy idx, 0 = main policy]
[bla]
...
...
[ATTR_OP_POLICY]
[op] = [policy idx]
...
This preserves all the information because it tells you which policies
actually are identical (shared), each per-op policy can have nested
policies referring to common ones, like in the ethtool case, etc.
OTOH, it's a lot trickier to implement - I haven't really come up with a
good way of doing it "generically" with the net/netlink/policy.c code.
I'm sure it can be solved, but I haven't really given it enough thought.
Perhaps by passing a "policy iterator" to netlink_policy_dump_start(),
instead of just a single policy (i.e. a function & a data ptr or so),
and then it can walk all the policies using that, assign the idxes etc.,
and dump them out in netlink_policy_dump_write()?
But then we'd still have to get the policy idx for a given policy, and
not clean up all the state when netlink_policy_dump_loop() returns
false, because you still need it for ATTR_OP_POLICY to find the idx from
the pointer?
I guess it's doable. Just seems a bit more complex. OTOH, it may be that
such complexity also completely makes sense for non-generic netlink
families anyway, I haven't looked at them much at all.
johannes
