netdev - Re: [PATCH net 1/2] openvswitch: Properly set L4 keys on "later" IP fragments.

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Message-ID: <CAOrHB_BKd=QKR_ScO+r7qAyZaniEbFur+iup1iXbtiycaFawjw@mail.gmail.com>
Date:   Sun, 25 Aug 2019 13:40:58 -0700
From:   Pravin Shelar <pshelar@....org>
To:     Justin Pettit <jpettit@....org>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Joe Stringer <joe@...d.net.nz>
Subject: Re: [PATCH net 1/2] openvswitch: Properly set L4 keys on "later" IP fragments.

On Sun, Aug 25, 2019 at 9:54 AM Pravin Shelar <pshelar@....org> wrote:
>
> On Sat, Aug 24, 2019 at 9:58 AM Justin Pettit <jpettit@....org> wrote:
> >
> > When IP fragments are reassembled before being sent to conntrack, the
> > key from the last fragment is used.  Unless there are reordering
> > issues, the last fragment received will not contain the L4 ports, so the
> > key for the reassembled datagram won't contain them.  This patch updates
> > the key once we have a reassembled datagram.
> >
> > Signed-off-by: Justin Pettit <jpettit@....org>
> > ---
> >  net/openvswitch/conntrack.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
> > index 848c6eb55064..f40ad2a42086 100644
> > --- a/net/openvswitch/conntrack.c
> > +++ b/net/openvswitch/conntrack.c
> > @@ -524,6 +524,10 @@ static int handle_fragments(struct net *net, struct sw_flow_key *key,
> >                 return -EPFNOSUPPORT;
> >         }
> >
> > +       /* The key extracted from the fragment that completed this datagram
> > +        * likely didn't have an L4 header, so regenerate it. */
> > +       ovs_flow_key_update(skb, key);
> > +
> >         key->ip.frag = OVS_FRAG_TYPE_NONE;
> >         skb_clear_hash(skb);
> >         skb->ignore_df = 1;
> > --
>
> Looks good to me.
>
> Acked-by: Pravin B Shelar <pshelar@....org>
>
Actually I am not sure about this change. caller of this function
(ovs_ct_execute()) does skb-pull and push of L2 header, calling
ovs_flow_key_update() is not safe here, it expect skb data to point to
L2 header.