Re: [PATCH RFC 5/5] udp: Support UDP fraglist GRO/GSO.

[Steffen Klassert <steffen.klassert@secunet.com>]

On Mon, Sep 23, 2019 at 09:01:13AM -0400, Willem de Bruijn wrote:
> On Fri, Sep 20, 2019 at 12:49 AM Steffen Klassert
> <steffen.klassert@secunet.com> wrote:
> >
> > This patch extends UDP GRO to support fraglist GRO/GSO
> > by using the previously introduced infrastructure.
> > All UDP packets that are not targeted to a GRO capable
> > UDP sockets are going to fraglist GRO now (local input
> > and forward).
> >
> > Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
> 
> > @@ -538,6 +579,15 @@ INDIRECT_CALLABLE_SCOPE int udp4_gro_complete(struct sk_buff *skb, int nhoff)
> >         const struct iphdr *iph = ip_hdr(skb);
> >         struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
> >
> > +       if (NAPI_GRO_CB(skb)->is_flist) {
> > +               uh->len = htons(skb->len - nhoff);
> > +
> > +               skb_shinfo(skb)->gso_type |= (SKB_GSO_FRAGLIST|SKB_GSO_UDP_L4);
> > +               skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
> > +
> > +               return 0;
> > +       }
> > +
> >         if (uh->check)
> >                 uh->check = ~udp_v4_check(skb->len - nhoff, iph->saddr,
> >                                           iph->daddr, 0);
> > diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
> > index 435cfbadb6bd..8836f2b69ef3 100644
> > --- a/net/ipv6/udp_offload.c
> > +++ b/net/ipv6/udp_offload.c
> > @@ -150,6 +150,15 @@ INDIRECT_CALLABLE_SCOPE int udp6_gro_complete(struct sk_buff *skb, int nhoff)
> >         const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
> >         struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
> >
> > +       if (NAPI_GRO_CB(skb)->is_flist) {
> > +               uh->len = htons(skb->len - nhoff);
> > +
> > +               skb_shinfo(skb)->gso_type |= (SKB_GSO_FRAGLIST|SKB_GSO_UDP_L4);
> > +               skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
> > +
> > +               return 0;
> > +       }
> > +
> 
> This is the same logic as in udp4_gro_complete. Can it be deduplicated
> in udp_gro_complete?

The code below would mess up the checksum then. We did not change
the packets, so the checksum is still correct.

> 
> >         if (uh->check)
> >                 uh->check = ~udp_v6_check(skb->len - nhoff, &ipv6h->saddr,
> >                                           &ipv6h->daddr, 0);