Re: [PATCH] monitor: fix printing of range elements in named sets

[Phil Sutter <phil@nwl.cc>]

Hi,

On Wed, Jul 12, 2017 at 01:24:24PM +0200, Arturo Borrero Gonzalez wrote:
> On 11 July 2017 at 20:11, Phil Sutter <phil@nwl.cc> wrote:
> > Hi,
> >
> > On Thu, Jul 06, 2017 at 04:36:45PM +0200, Arturo Borrero Gonzalez wrote:
> >> If you add set elements to interval sets, the output is wrong.
> >> Fix this by caching first element of the range (first event),
> >> then wait for the second element of the range (second event) to
> >> print them both at the same time.
> >
> > As promised, I am preparing my own solution for side-by-side comparison.
> > Though I'm running into problems and want to use the occasion to discuss
> > them first:
> >
> > What I wasn't able to solve yet are half-open ranges, like so:
> >
> > | nft add set ip t portrange { type inet_service; flags interval; }
> > | nft add element ip t portrange { 1024-65535 }
> >
> > In this case there is only a single element with value 1024 which
> > doesn't have EXPR_F_INTERVAL_END set. Looking at
> > interval_map_decompose(), this is identified to be a range till the end
> > of the scope if it's the last element in the set.
> >
> > In monitor code though, I can't predict whether an interval end element
> > will come afterwards or not, so I end up caching the element and
> > everything turns into a mess. I'm pretty sure your solution has the same
> > problem, could you check that?
> >
> > Right now, I only see two ways to get this sorted:
> >
> > 1) Change kernel code to always include both start end end of a range in
> >    a single notification. This would eliminate the need for any caching
> >    in netlink_events_setelem_cb() altogether!
> >
> > 2) Change monitor code to cache all events until the final NFTA_GEN_ID
> >    message, then handle all messages at once.
> >
> > What do you think?
> >
> 
> We should avoid touching the kernel for this.

I found a userspace solution yesterday: I created a new callback for
NFT_MSG_NEWGEN, which will take care of the remaining cached element.
Patch follows later.

Thanks, Phil