Subject: Re: [PATCH net-next] openvswitch: add ct_clear action

From: Eric Garver <[email-masked]>
Date: Tue, 10 Oct 2017 08:48:36 -0400

On Mon, Oct 09, 2017 at 09:41:53PM -0700, Pravin Shelar wrote:
> On Fri, Oct 6, 2017 at 9:44 AM, Eric Garver <[email-masked]> wrote:
> > This adds a ct_clear action for clearing conntrack state. ct_clear is
> > currently implemented in OVS userspace, but is not backed by an action
> > in the kernel datapath. This is useful for flows that may modify a
> > packet tuple after a ct lookup has already occurred.
> >
> > Signed-off-by: Eric Garver <[email-masked]>
> Patch mostly looks good. I have following comments.

Thanks for the review Pravin!

> > ---
> >  include/uapi/linux/openvswitch.h |  2 ++
> >  net/openvswitch/actions.c        |  5 +++++
> >  net/openvswitch/conntrack.c      | 12 ++++++++++++
> >  net/openvswitch/conntrack.h      |  7 +++++++
> >  net/openvswitch/flow_netlink.c   |  5 +++++
> >  5 files changed, 31 insertions(+)
> >
> > diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
> > index 156ee4cab82e..1b6e510e2cc6 100644
> > --- a/include/uapi/linux/openvswitch.h
> > +++ b/include/uapi/linux/openvswitch.h
> > @@ -806,6 +806,7 @@ struct ovs_action_push_eth {
> >   * packet.
> >   * @OVS_ACTION_ATTR_POP_ETH: Pop the outermost Ethernet header off the
> >   * packet.
> > + * @OVS_ACTION_ATTR_CT_CLEAR: Clear conntrack state from the packet.
> >   *
> >   * Only a single header can be set with a single %OVS_ACTION_ATTR_SET.  Not all
> >   * fields within a header are modifiable, e.g. the IPv4 protocol and fragment
> > @@ -835,6 +836,7 @@ enum ovs_action_attr {
> >         OVS_ACTION_ATTR_TRUNC,        /* u32 struct ovs_action_trunc. */
> >         OVS_ACTION_ATTR_PUSH_ETH,     /* struct ovs_action_push_eth. */
> >         OVS_ACTION_ATTR_POP_ETH,      /* No argument. */
> > +       OVS_ACTION_ATTR_CT_CLEAR,     /* No argument. */
> >
> >         __OVS_ACTION_ATTR_MAX,        /* Nothing past this will be accepted
> >                                        * from userspace. */
> > diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
> > index a54a556fcdb5..db9c7f2e662b 100644
> > --- a/net/openvswitch/actions.c
> > +++ b/net/openvswitch/actions.c
> > @@ -1203,6 +1203,10 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
> >                                 return err == -EINPROGRESS ? 0 : err;
> >                         break;
> >
> > +               case OVS_ACTION_ATTR_CT_CLEAR:
> > +                       err = ovs_ct_clear(skb, key);
> > +                       break;
> > +
> >                 case OVS_ACTION_ATTR_PUSH_ETH:
> >                         err = push_eth(skb, key, nla_data(a));
> >                         break;
> > @@ -1210,6 +1214,7 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
> >                 case OVS_ACTION_ATTR_POP_ETH:
> >                         err = pop_eth(skb, key);
> >                         break;
> > +
> >                 }
> Unrelated change.
> 

Right. Not sure how that got there. :/

> >
> >                 if (unlikely(err)) {
> > diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
> > index d558e882ca0c..f9b73c726ad7 100644
> > --- a/net/openvswitch/conntrack.c
> > +++ b/net/openvswitch/conntrack.c
> > @@ -1129,6 +1129,18 @@ int ovs_ct_execute(struct net *net, struct sk_buff *skb,
> >         return err;
> >  }
> >
> > +int ovs_ct_clear(struct sk_buff *skb, struct sw_flow_key *key)
> > +{
> > +       if (skb_nfct(skb)) {
> > +               nf_conntrack_put(skb_nfct(skb));
> > +               nf_ct_set(skb, NULL, 0);
> Can the new conntract state be appropriate? may be IP_CT_UNTRACKED?
> 

I think that will be fine. I'll run my tests again to verify.

> > +       }
> > +
> > +       ovs_ct_fill_key(skb, key);
> > +
> I do not see need to refill the key if there is no skb-nf-ct.
> 

Good point.

> > +       return 0;
> > +}
> > +
> >  static int ovs_ct_add_helper(struct ovs_conntrack_info *info, const char *name,
> >                              const struct sw_flow_key *key, bool log)
> >  {