Re: [ovs-discuss] Lost in translation! OFP to DPDK datapath OVS actions?

[Ben Pfaff]

Maybe.  Sometimes it's too hard to keep track of changes just by looking
at the flow.

On Wed, Jan 24, 2018 at 08:18:12PM +0100, Alan Kayahan wrote:
> Thanks for bearing with me so far Ben. I will post my experience in
> creating a custom action and match step by step like some others have done
> in the mailing list, both for hearing your input and for others to benefit.
> 
> What if the action is creating a new header, an IPv6 extension header, in
> the packet? My OVS action is pushing the L2+L3 headers in the packet
> buffer, making enough room for say the fragmentation header, then appending
> the header and readjusting the L4 offset. In this case, does it make sense
> to immediately emit ODP action via "nl_msg_put_u16(ctx->odp_actions,
> OVS_ACTION_ATTR_PUSH_EXTH, ofpact_get_PUSH_EXTH(a)->arg);" in
> ofproto-dpif-xlate?
> 
> 
> 2018-01-22 20:33 GMT+01:00 Ben Pfaff :
> 
> > Actions that just set fields don't emit ODP actions to do that
> > immediately because controllers often change fields multiple times
> > between outputs, so that it would be wasteful to emit the changes
> > multiple times.  Instead, at the time of emitting an output (or other
> > visible side effect), OVS emits all changes to fields in one group.
> >
> > On Sat, Jan 13, 2018 at 09:11:50AM +0100, Alan Kayahan wrote:
> > > Indeed. My custom action works when I put nl_msg_put_flag(ctx->odp_
> > actions,
> > > OVS_ACTION_ATTR_MY_ACTION); however none of the other cases follow this
> > > pattern. They all set flow->xxx from the struct casted ofpact instead.
> > > Since both setting ctx->odp_actions and flow->xxx works, I have the
> > > following questions
> > >
> > > 1) Where do the actions defined in ctx->odp_actions get actuated?
> > > 2) Where do the actions for the struct flow get actuated, and how does
> > the
> > > actuator know what OVS actions to actuate?
> > > 3) Can we say that do_xlate_actions() is currently being used outside the
> > > purpose that its name implies, because all it does is to set the fields
> > of
> > > the struct flow to those set in ofpact struct?
> > >
> > > Thanks
> > >
> > > 2018-01-12 18:36 GMT+01:00 Ben Pfaff :
> > >
> > > > On Fri, Jan 12, 2018 at 11:39:44AM +0100, Alan Kayahan wrote:
> > > > > Hello,
> > > > >
> > > > > Per my understanding from /ovs-discuss/2015-May/037313.html,
> > > > > ofproto-dpif-xlate translates OFP actions into Netlink format, which
> > is
> > > > > useful for datapath actions implemented in the kernel module. Does
> > that
> > > > > hold for OFP to DPDK datapath actions too?
> > > >
> > > > Yes.
> > > >
> > > > > I couldn't find a connection from ofproto-dpif-xlate to
> > > > > odp_execute_actions. Where does the translation of ofpact structs
> > into
> > > > > OVS actions implemented in DPDK datapath take place?
> > > >
> > > > ofproto-dpif-xlate does the translation for both datapaths, in the same
> > > > way.
> > > >
> >
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Re: [ovs-discuss] Lost in translation! OFP to DPDK datapath OVS actions?

[Ben Pfaff]

Actions that just set fields don't emit ODP actions to do that
immediately because controllers often change fields multiple times
between outputs, so that it would be wasteful to emit the changes
multiple times.  Instead, at the time of emitting an output (or other
visible side effect), OVS emits all changes to fields in one group.

On Sat, Jan 13, 2018 at 09:11:50AM +0100, Alan Kayahan wrote:
> Indeed. My custom action works when I put nl_msg_put_flag(ctx->odp_actions,
> OVS_ACTION_ATTR_MY_ACTION); however none of the other cases follow this
> pattern. They all set flow->xxx from the struct casted ofpact instead.
> Since both setting ctx->odp_actions and flow->xxx works, I have the
> following questions
> 
> 1) Where do the actions defined in ctx->odp_actions get actuated?
> 2) Where do the actions for the struct flow get actuated, and how does the
> actuator know what OVS actions to actuate?
> 3) Can we say that do_xlate_actions() is currently being used outside the
> purpose that its name implies, because all it does is to set the fields of
> the struct flow to those set in ofpact struct?
> 
> Thanks
> 
> 2018-01-12 18:36 GMT+01:00 Ben Pfaff :
> 
> > On Fri, Jan 12, 2018 at 11:39:44AM +0100, Alan Kayahan wrote:
> > > Hello,
> > >
> > > Per my understanding from /ovs-discuss/2015-May/037313.html,
> > > ofproto-dpif-xlate translates OFP actions into Netlink format, which is
> > > useful for datapath actions implemented in the kernel module. Does that
> > > hold for OFP to DPDK datapath actions too?
> >
> > Yes.
> >
> > > I couldn't find a connection from ofproto-dpif-xlate to
> > > odp_execute_actions. Where does the translation of ofpact structs into
> > > OVS actions implemented in DPDK datapath take place?
> >
> > ofproto-dpif-xlate does the translation for both datapaths, in the same
> > way.
> >
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Re: [ovs-discuss] Lost in translation! OFP to DPDK datapath OVS actions?

[Alan Kayahan]

Indeed. My custom action works when I put nl_msg_put_flag(ctx->odp_actions,
OVS_ACTION_ATTR_MY_ACTION); however none of the other cases follow this
pattern. They all set flow->xxx from the struct casted ofpact instead.
Since both setting ctx->odp_actions and flow->xxx works, I have the
following questions

1) Where do the actions defined in ctx->odp_actions get actuated?
2) Where do the actions for the struct flow get actuated, and how does the
actuator know what OVS actions to actuate?
3) Can we say that do_xlate_actions() is currently being used outside the
purpose that its name implies, because all it does is to set the fields of
the struct flow to those set in ofpact struct?

Thanks

2018-01-12 18:36 GMT+01:00 Ben Pfaff :

> On Fri, Jan 12, 2018 at 11:39:44AM +0100, Alan Kayahan wrote:
> > Hello,
> >
> > Per my understanding from /ovs-discuss/2015-May/037313.html,
> > ofproto-dpif-xlate translates OFP actions into Netlink format, which is
> > useful for datapath actions implemented in the kernel module. Does that
> > hold for OFP to DPDK datapath actions too?
>
> Yes.
>
> > I couldn't find a connection from ofproto-dpif-xlate to
> > odp_execute_actions. Where does the translation of ofpact structs into
> > OVS actions implemented in DPDK datapath take place?
>
> ofproto-dpif-xlate does the translation for both datapaths, in the same
> way.
>
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Re: [ovs-discuss] Lost in translation! OFP to DPDK datapath OVS actions?

[Ben Pfaff]

On Fri, Jan 12, 2018 at 11:39:44AM +0100, Alan Kayahan wrote:
> Hello,
> 
> Per my understanding from /ovs-discuss/2015-May/037313.html,
> ofproto-dpif-xlate translates OFP actions into Netlink format, which is
> useful for datapath actions implemented in the kernel module. Does that
> hold for OFP to DPDK datapath actions too? 

Yes.

> I couldn't find a connection from ofproto-dpif-xlate to
> odp_execute_actions. Where does the translation of ofpact structs into
> OVS actions implemented in DPDK datapath take place?

ofproto-dpif-xlate does the translation for both datapaths, in the same
way.
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