netdev - Re: [PATCH net-next 05/15] ipv6/gso: remove temporary HBH/jumbo header

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Date:   Thu, 3 Feb 2022 18:15:34 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>, Coco Li <lixiaoyan@...gle.com>
Subject: Re: [PATCH net-next 05/15] ipv6/gso: remove temporary HBH/jumbo header

On Thu, Feb 3, 2022 at 5:48 PM Eric Dumazet <edumazet@...gle.com> wrote:

>
> Well, this does not work at all.
>
>
>
>
> >  static inline bool ipv6_accept_ra(struct inet6_dev *idev)
> >  {
> >         /* If forwarding is enabled, RA are not accepted unless the special
> > diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
> > index d37a79a8554e92a1dcaa6fd023cafe2114841ece..7f65097c8f30fa19a8c9c265eb4f027e91848021
> > 100644
> > --- a/net/ipv6/ip6_offload.c
> > +++ b/net/ipv6/ip6_offload.c
> > @@ -87,6 +87,27 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
> >         bool gso_partial;
> >
> >         skb_reset_network_header(skb);
> > +       if (ipv6_has_hopopt_jumbo(skb)) {
> > +               const int hophdr_len = sizeof(struct hop_jumbo_hdr);
> > +               int err;
> > +
> > +               err = skb_cow_head(skb, 0);
> > +               if (err < 0)
> > +                       return ERR_PTR(err);
> > +
> > +               /* remove the HBH header.
> > +                * Layout: [Ethernet header][IPv6 header][HBH][TCP header]
> > +                */
> > +               memmove(skb->data + hophdr_len,
> > +                       skb->data,

Oh, I must use skb_mac_header() instead of skb->data, sorry for the noise.

> > +                       ETH_HLEN + sizeof(struct ipv6hdr));
> > +               skb->data += hophdr_len;
> > +               skb->len -= hophdr_len;
> > +               skb->network_header += hophdr_len;
> > +               skb->mac_header += hophdr_len;
> > +               ipv6h = (struct ipv6hdr *)skb->data;
> > +               ipv6h->nexthdr = IPPROTO_TCP;
> > +       }
> >         nhoff = skb_network_header(skb) - skb_mac_header(skb);
> >         if (unlikely(!pskb_may_pull(skb, sizeof(*ipv6h))))
> >                 goto out;