netdev - Re: [PATCH v2 net-next 8/9] bpf: nfp: Report bpf_prog ID during XDP_QUERY

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Date:   Tue, 13 Jun 2017 20:43:00 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     <netdev@...r.kernel.org>, Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>
Subject: Re: [PATCH v2 net-next 8/9] bpf: nfp: Report bpf_prog ID during
 XDP_QUERY_PROG

On Tue, 13 Jun 2017 20:19:53 -0700, Martin KaFai Lau wrote:
> On Tue, Jun 13, 2017 at 07:19:50PM -0700, Jakub Kicinski wrote:
> > On Tue, 13 Jun 2017 17:37:50 -0700, Martin KaFai Lau wrote:  
> > > On Tue, Jun 13, 2017 at 04:52:32PM -0700, Jakub Kicinski wrote:  
> > > > On Tue, 13 Jun 2017 14:08:40 -0700, Martin KaFai Lau wrote:  
> > > > > -	case XDP_QUERY_PROG:
> > > > > -		xdp->prog_attached = !!nn->dp.xdp_prog;
> > > > > +	case XDP_QUERY_PROG: {
> > > > > +		const struct bpf_prog *xdp_prog;
> > > > > +
> > > > > +		xdp_prog = nn->dp.xdp_prog;
> > > > > +		if (xdp_prog) {
> > > > > +			xdp->prog_id = xdp_prog->aux->id;
> > > > > +			xdp->prog_attached = true;
> > > > > +		} else {
> > > > > +			xdp->prog_id = 0;
> > > > > +			xdp->prog_attached = false;
> > > > > +		}
> > > > >  		return 0;
> > > > > +	}  
> > > >
> > > > I'm sorry to nit pick but it could be done on a single line:
> > > >
> > > > 	case XDP_QUERY_PROG:
> > > > 		xdp->prog_attached = !!nn->dp.xdp_prog;
> > > > +		xdp->prog_id = nn->dp.xdp_prog ? nn->dp.xdp_prog->aux->id : 0;
> > > >  		return 0;
> > > >  	default:
> > > >  		return -EINVAL;  
> > > OK...
> > >  
> > > >
> > > >
> > > > What would be even cooler is a helper like this:
> > > >
> > > > static inline u32 bpf_prog_id(struct bpf_prog *prog)
> > > > {
> > > > 	if (!prog)
> > > > 		return 0;
> > > > 	return prog->aux->id;
> > > > }
> > > >
> > > > in linux/bpf.h.  
> > > Good idea.  
> >
> > You may actually have to add that into a source file, because bpf.h
> > does not know the definition of struct bpf_prog :(  
> Yeah. filter.h seems not working well either.
> It looks good to me at the first thought.  After a second thought,
> in the future, I am not so sure having a getter for every fields
> in bpf_prog.

Yes, if it's not a static inline it's far less appealing...
 
> I can put bpf_prog_id() in nfp_net_common.c only.
> or do 'xdp->prog_id = nn->dp.xdp_prog ? nn->dp.xdp_prog->aux->id : 0;'
> as you suggested earlier also.
> I am fine either way.  Your call ;)

OK, let's do the ternary operator version then :)  Sorry for leading you
into this dead end.