[ipsec] esp6: support ipv6 nexthdrs process for beet gso segment

For beet mode, when it's ipv6 inner address with nexthdrs set,
the packet format might be:

    ----------------------------------------------------
    | outer  |     | dest |     |      |  ESP    | ESP |
    | IP6 hdr| ESP | opts.| TCP | Data | Trailer | ICV |
    ----------------------------------------------------

Before doing gso segment in xfrm6_beet_gso_segment(), it should
skip all nexthdrs and get the real transport proto, and set
transport_header properly.

This patch is to fix it by simply calling ipv6_skip_exthdr()
in xfrm6_beet_gso_segment().

Fixes: 7f9e40eb18a9 ("esp6: add gso_segment for esp6 beet mode")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 net/ipv6/esp6_offload.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

2020-04-10, 17:07:31 +0800, Xin Long wrote:
> For beet mode, when it's ipv6 inner address with nexthdrs set,
> the packet format might be:
> 
>     ----------------------------------------------------
>     | outer  |     | dest |     |      |  ESP    | ESP |
>     | IP6 hdr| ESP | opts.| TCP | Data | Trailer | ICV |
>     ----------------------------------------------------
> 
> Before doing gso segment in xfrm6_beet_gso_segment(), it should
> skip all nexthdrs and get the real transport proto, and set
> transport_header properly.
> 
> This patch is to fix it by simply calling ipv6_skip_exthdr()
> in xfrm6_beet_gso_segment().
> 
> Fixes: 7f9e40eb18a9 ("esp6: add gso_segment for esp6 beet mode")
> Signed-off-by: Xin Long <lucien.xin@gmail.com>
> ---
>  net/ipv6/esp6_offload.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv6/esp6_offload.c b/net/ipv6/esp6_offload.c
> index b828508..021f58c 100644
> --- a/net/ipv6/esp6_offload.c
> +++ b/net/ipv6/esp6_offload.c
> @@ -173,7 +173,7 @@ static struct sk_buff *xfrm6_beet_gso_segment(struct xfrm_state *x,
>  	struct xfrm_offload *xo = xfrm_offload(skb);
>  	struct sk_buff *segs = ERR_PTR(-EINVAL);
>  	const struct net_offload *ops;
> -	int proto = xo->proto;
> +	u8 proto = xo->proto;
>  
>  	skb->transport_header += x->props.header_len;
>  
> @@ -184,7 +184,13 @@ static struct sk_buff *xfrm6_beet_gso_segment(struct xfrm_state *x,
>  		proto = ph->nexthdr;
>  	}
>  
> -	if (x->sel.family != AF_INET6) {
> +	if (x->sel.family == AF_INET6) {
> +		int offset = skb_transport_offset(skb);
> +		__be16 frag;
> +
> +		offset = ipv6_skip_exthdr(skb, offset, &proto, &frag);
> +		skb->transport_header += offset;

This seems a bit wrong: we start with offset = transport_offset, then
ipv6_skip_exthdr adds the size of the extension headers to it.

In a simple case where there's no extension header, ipv6_skip_exthdr
returns offset. Now we add offset to skb->transport_header, so
transport_header is increased, but it shouldn't have changed.

What am I missing?

Thanks.

On Wed, Apr 15, 2020 at 5:56 PM Sabrina Dubroca <sd@queasysnail.net> wrote:
>
> 2020-04-10, 17:07:31 +0800, Xin Long wrote:
> > For beet mode, when it's ipv6 inner address with nexthdrs set,
> > the packet format might be:
> >
> >     ----------------------------------------------------
> >     | outer  |     | dest |     |      |  ESP    | ESP |
> >     | IP6 hdr| ESP | opts.| TCP | Data | Trailer | ICV |
> >     ----------------------------------------------------
> >
> > Before doing gso segment in xfrm6_beet_gso_segment(), it should
> > skip all nexthdrs and get the real transport proto, and set
> > transport_header properly.
> >
> > This patch is to fix it by simply calling ipv6_skip_exthdr()
> > in xfrm6_beet_gso_segment().
> >
> > Fixes: 7f9e40eb18a9 ("esp6: add gso_segment for esp6 beet mode")
> > Signed-off-by: Xin Long <lucien.xin@gmail.com>
> > ---
> >  net/ipv6/esp6_offload.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/ipv6/esp6_offload.c b/net/ipv6/esp6_offload.c
> > index b828508..021f58c 100644
> > --- a/net/ipv6/esp6_offload.c
> > +++ b/net/ipv6/esp6_offload.c
> > @@ -173,7 +173,7 @@ static struct sk_buff *xfrm6_beet_gso_segment(struct xfrm_state *x,
> >       struct xfrm_offload *xo = xfrm_offload(skb);
> >       struct sk_buff *segs = ERR_PTR(-EINVAL);
> >       const struct net_offload *ops;
> > -     int proto = xo->proto;
> > +     u8 proto = xo->proto;
> >
> >       skb->transport_header += x->props.header_len;
> >
> > @@ -184,7 +184,13 @@ static struct sk_buff *xfrm6_beet_gso_segment(struct xfrm_state *x,
> >               proto = ph->nexthdr;
> >       }
> >
> > -     if (x->sel.family != AF_INET6) {
> > +     if (x->sel.family == AF_INET6) {
> > +             int offset = skb_transport_offset(skb);
> > +             __be16 frag;
> > +
> > +             offset = ipv6_skip_exthdr(skb, offset, &proto, &frag);
> > +             skb->transport_header += offset;
>
> This seems a bit wrong: we start with offset = transport_offset, then
> ipv6_skip_exthdr adds the size of the extension headers to it.
>
> In a simple case where there's no extension header, ipv6_skip_exthdr
> returns offset. Now we add offset to skb->transport_header, so
> transport_header is increased, but it shouldn't have changed.
>
> What am I missing?
You're right, actually skb_transport_offset(skb) is always 0 in there.

I will post v2 with:
skb->transport_header += ipv6_skip_exthdr(skb, 0, &proto, &frag);

Thanks for reviewing.

>
> Thanks.
>
> --
> Sabrina
>