Re: [PATCH net-next V2 3/3] tap: XDP support

[Jason Wang]

On 2017å08æ14æ 16:43, Daniel Borkmann wrote:
> On 08/11/2017 01:41 PM, Jason Wang wrote:
> > This patch tries to implement XDP for tun. The implementation was
> > split into two parts:
> [...]
> > @@ -1402,6 +1521,22 @@ static ssize_t tun_get_user(struct tun_struct 
> > *tun, struct tun_file *tfile,
> >       skb_reset_network_header(skb);
> >       skb_probe_transport_header(skb, 0);
> >
> > +    if (generic_xdp) {
> > +        struct bpf_prog *xdp_prog;
> > +        int ret;
> > +
> > +        rcu_read_lock();
> > +        xdp_prog = rcu_dereference(tun->xdp_prog);
>
> The name generic_xdp is a bit confusing in this context given this
> is 'native' XDP, perhaps above if (generic_xdp) should have a comment
> explaining semantics for tun and how it relates to actual generic xdp
> that sits at dev->xdp_prog, and gets run from netif_rx_ni(). Or just
> name the bool xdp_handle_gso with a comment that we let the generic
> XDP infrastructure deal with non-linear skbs instead of having to
> re-implement the do_xdp_generic() internals, plus a statement that
> the actual generic XDP comes a bit later in the path. That would at
> least make it more obvious to read, imho.

Ok, since non gso packet (e.g jumbo packet) may go this way too, 
something like "xdp_handle_skb" is better. Will send a patch.

Thanks

> > +        if (xdp_prog) {
> > +            ret = do_xdp_generic(xdp_prog, skb);
> > +            if (ret != XDP_PASS) {
> > +                rcu_read_unlock();
> > +                return total_len;
> > +            }
> > +        }
> > +        rcu_read_unlock();
> > +    }
> > +
> >       rxhash = __skb_get_hash_symmetric(skb);
> >   #ifndef CONFIG_4KSTACKS
> >       tun_rx_batched(tun, tfile, skb, more);