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

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Date:   Sun, 12 Aug 2018 18:09:45 -0700
From:   Pravin Shelar <pshelar@....org>
To:     Yi-Hung Wei <yihung.wei@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        William Tu <u9012063@...il.com>
Subject: Re: [PATCH net-next] openvswitch: Derive IP protocol number for IPv6
 later frags

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