netdev - Re: [PATCH net-next] openvswitch: Derive IP protocol number for IPv6 later frags

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Message-ID: <CALDO+SYG_yFpS6ypj8bHJM9U2NkzxSQLdAQQJgD7ToHvi_1LKQ@mail.gmail.com>
Date:   Mon, 13 Aug 2018 10:48:12 -0700
From:   William Tu <u9012063@...il.com>
To:     pravin shelar <pshelar@....org>
Cc:     Yi-Hung Wei <yihung.wei@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] openvswitch: Derive IP protocol number for IPv6
 later frags

On Sun, Aug 12, 2018 at 6:09 PM Pravin Shelar <pshelar@....org> wrote:
>
> On Fri, Aug 10, 2018 at 10:19 AM, Yi-Hung Wei <yihung.wei@...il.com> wrote:
> > Currently, OVS only parses the IP protocol number for the first
> > IPv6 fragment, but sets the IP protocol number for the later fragments
> > to be NEXTHDF_FRAGMENT.  This patch tries to derive the IP protocol
> > number for the IPV6 later frags so that we can match that.
> >
> > Signed-off-by: Yi-Hung Wei <yihung.wei@...il.com>
> > ---
> >  net/openvswitch/flow.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
> > index 56b8e7167790..3d654c4f71be 100644
> > --- a/net/openvswitch/flow.c
> > +++ b/net/openvswitch/flow.c
> > @@ -297,7 +297,13 @@ static int parse_ipv6hdr(struct sk_buff *skb, struct sw_flow_key *key)
> >
> >         nh_len = payload_ofs - nh_ofs;
> >         skb_set_transport_header(skb, nh_ofs + nh_len);
> > -       key->ip.proto = nexthdr;
> > +       if (key->ip.frag == OVS_FRAG_TYPE_LATER) {
> > +               unsigned int offset = 0;

How about we start the 2nd time parsing from
unsigned int offset = payload_ofs;

> > +
> > +               key->ip.proto = ipv6_find_hdr(skb, &offset, -1, NULL, NULL);

Then we only find the last header from previous parsed offset.

William

> > +       } else {
> > +               key->ip.proto = nexthdr;
> > +       }
> parsing ipv6 ipv6_skip_exthdr() is called to find fragment hdr and
> then this patch calls ipv6_find_hdr() to find next protocol. I think
> we could call ipv6_find_hdr() to get fragment type and next hdr, that
> would save parsing same packet twice in some cases.
>
> Other option would be calling ipv6_find_hdr() after setting OVS_FRAG_TYPE_LATER.