netdev - Re: [PATCHv6 bpf-next 2/3] sample/bpf: add xdp_redirect_map

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Message-ID: <20200711002127.GD2531@dhcp-12-153.nay.redhat.com>
Date:   Sat, 11 Jul 2020 08:21:27 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Jiri Benc <jbenc@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>, ast@...nel.org,
        Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
Subject: Re: [PATCHv6 bpf-next 2/3] sample/bpf: add
 xdp_redirect_map_multicast test

On Fri, Jul 10, 2020 at 04:32:35PM +0200, Daniel Borkmann wrote:
> On 7/10/20 8:41 AM, Hangbin Liu wrote:
> > On Fri, Jul 10, 2020 at 12:40:11AM +0200, Daniel Borkmann wrote:
> > > > +SEC("xdp_redirect_map_multi")
> > > > +int xdp_redirect_map_multi_prog(struct xdp_md *ctx)
> > > > +{
> > > > +	long *value;
> > > > +	u32 key = 0;
> > > > +
> > > > +	/* count packet in global counter */
> > > > +	value = bpf_map_lookup_elem(&rxcnt, &key);
> > > > +	if (value)
> > > > +		*value += 1;
> > > > +
> > > > +	return bpf_redirect_map_multi(&forward_map, &null_map,
> > > > +				      BPF_F_EXCLUDE_INGRESS);
> > > 
> > > Why not extending to allow use-case like ...
> > > 
> > >    return bpf_redirect_map_multi(&fwd_map, NULL, BPF_F_EXCLUDE_INGRESS);
> > > 
> > > ... instead of requiring a dummy/'null' map?
> > 
> > I planed to let user set NULL, but the arg2_type is ARG_CONST_MAP_PTR, which
> > not allow NULL pointer.
> 
> Right, but then why not adding a new type ARG_CONST_MAP_PTR_OR_NULL ?

Yes, that's what I plan for next step.

Thanks
Hangbin