netdev - Re: [PATCHv7 bpf-next 1/3] xdp: add a new helper for dev map multicast support

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Date:   Wed, 15 Jul 2020 20:25:14 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        Jiri Benc <jbenc@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>, ast@...nel.org,
        Daniel Borkmann <daniel@...earbox.net>,
        Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
Subject: Re: [PATCHv7 bpf-next 1/3] xdp: add a new helper for dev map
 multicast support

On Tue, Jul 14, 2020 at 11:52:14PM +0200, Toke Høiland-Jørgensen wrote:
> > +bool dev_in_exclude_map(struct bpf_dtab_netdev *obj, struct bpf_map *map,
> > +			int exclude_ifindex)
> > +{
> > +	struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
> > +	struct bpf_dtab_netdev *dev;
> > +	struct hlist_head *head;
> > +	int i = 0;
> > +
> > +	if (obj->dev->ifindex == exclude_ifindex)
> > +		return true;
> > +
> > +	if (!map || map->map_type != BPF_MAP_TYPE_DEVMAP_HASH)
> > +		return false;
> 
> The map type should probably be checked earlier and the whole operation
> aborted if it is wrong...

Yes, I have already checked it in the helper, there should no need to double
check. I will remove this check.

> 
> > +
> > +	for (; i < dtab->n_buckets; i++) {
> > +		head = dev_map_index_hash(dtab, i);
> > +
> > +		dev = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),
> > +					    struct bpf_dtab_netdev,
> > +					    index_hlist);
> > +
> > +		if (dev && dev->idx == exclude_ifindex)
> > +			return true;
> > +	}
> 
> This looks broken; why are you iterating through the buckets? Shouldn't
> this just be something like:
> 
> return __dev_map_hash_lookup_elem(map, obj->dev->ifindex) != NULL;

Ah, yes, I forgot this. I will update the code.

Thanks
Hangbin