Re: [PATCH bpf-next v5 2/2] bpf, xdp: restructure redirect actions

[Daniel Borkmann <daniel@xxxxxxxxxxxxx>]

On 3/5/21 6:11 PM, Björn Töpel wrote:
> On 2021-03-05 16:44, Daniel Borkmann wrote:
> > On 2/27/21 1:21 PM, Björn Töpel wrote:
> > [...]
> > > diff --git a/include/linux/filter.h b/include/linux/filter.h
> > > index 008691fd3b58..a7752badc2ec 100644
> > > --- a/include/linux/filter.h
> > > +++ b/include/linux/filter.h
> > > @@ -646,11 +646,20 @@ struct bpf_redirect_info {
> > >       u32 flags;
> > >       u32 tgt_index;
> > >       void *tgt_value;
> > > -    struct bpf_map *map;
> > > +    u32 map_id;
> > > +    u32 tgt_type;
> > >       u32 kern_flags;
> > >       struct bpf_nh_params nh;
> > >   };
> > > +enum xdp_redirect_type {
> > > +    XDP_REDIR_UNSET,
> > > +    XDP_REDIR_DEV_IFINDEX,
> >
> > [...]
> >
> > > +    XDP_REDIR_DEV_MAP,
> > > +    XDP_REDIR_CPU_MAP,
> > > +    XDP_REDIR_XSK_MAP,
> >
> > Did you eval whether for these maps we can avoid the redundant def above by just
> > passing in map->map_type as ri->tgt_type and inferring the XDP_REDIR_UNSET from
> > invalid map_id of 0 (given the idr will never allocate such)?
>
> I'll take a stab at it!

Sounds good, thanks! If it doesn't simplify or gets worse, we can always stick to
the one here.

> > [...]
> > > @@ -4068,10 +4039,9 @@ BPF_CALL_2(bpf_xdp_redirect, u32, ifindex, u64, flags)
> > >       if (unlikely(flags))
> > >           return XDP_ABORTED;
> > > -    ri->flags = flags;
> > > -    ri->tgt_index = ifindex;
> > > -    ri->tgt_value = NULL;
> > > -    WRITE_ONCE(ri->map, NULL);
> > > +    ri->tgt_type = XDP_REDIR_DEV_IFINDEX;
> > > +    ri->tgt_index = 0;
> > > +    ri->tgt_value = (void *)(long)ifindex;
> >
> > nit: Bit ugly to pass this in /read out this way, maybe union if we cannot use
> > tgt_index?
>
> Dito!
>
>
> Thanks for the input! I'll get back with a v6!
>
>
> Björn
>
>
> > >       return XDP_REDIRECT;
> > >   }
> > > diff --git a/net/xdp/xskmap.c b/net/xdp/xskmap.c
> > > index 711acb3636b3..2c58d88aa69d 100644
> > > --- a/net/xdp/xskmap.c
> > > +++ b/net/xdp/xskmap.c
> > > @@ -87,7 +87,6 @@ static void xsk_map_free(struct bpf_map *map)
> > >   {
> > >       struct xsk_map *m = container_of(map, struct xsk_map, map);
> > > -    bpf_clear_redirect_map(map);
> > >       synchronize_net();
> > >       bpf_map_area_free(m);
> > >   }
> > > @@ -229,7 +228,8 @@ static int xsk_map_delete_elem(struct bpf_map *map, void *key)
> > >   static int xsk_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
> > >   {
> > > -    return __bpf_xdp_redirect_map(map, ifindex, flags, __xsk_map_lookup_elem);
> > > +    return __bpf_xdp_redirect_map(map, ifindex, flags, __xsk_map_lookup_elem,
> > > +                      XDP_REDIR_XSK_MAP);
> > >   }
> > >   void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,