netdev - Re: [PATCH net-next RFC 7/8] udp: gro behind static key

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Message-ID: <CAF=yD-JKbSPmv1J8KioPTkEb9aEev-exEajv0xKYWkCtTMjVww@mail.gmail.com>
Date:   Mon, 17 Sep 2018 10:12:28 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        steffen.klassert@...unet.com, David Miller <davem@...emloft.net>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net-next RFC 7/8] udp: gro behind static key

On Mon, Sep 17, 2018 at 6:24 AM Paolo Abeni <pabeni@...hat.com> wrote:
>
> On Fri, 2018-09-14 at 13:59 -0400, Willem de Bruijn wrote:
> > diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> > index 4f6aa95a9b12..f44fe328aa0f 100644
> > --- a/net/ipv4/udp_offload.c
> > +++ b/net/ipv4/udp_offload.c
> > @@ -405,7 +405,7 @@ static struct sk_buff *udp4_gro_receive(struct list_head *head,
> >  {
> >       struct udphdr *uh = udp_gro_udphdr(skb);
> >
> > -     if (unlikely(!uh))
> > +     if (unlikely(!uh) || !static_branch_unlikely(&udp_encap_needed_key))
> >               goto flush;
> >
> >       /* Don't bother verifying checksum if we're going to flush anyway. */
>
> If I read this correctly, once udp_encap_needed_key is enabled, it will
> never be turned off, because the tunnel and encap socket shut down does
> not cope with udp_encap_needed_key.
>
> Perhaps we should take care of that, too.

Agreed. For now I reused what's already there, but I can extend
that with refcounting using static_branch_inc/static_branch_dec.