[ovs-dev] [PATCH 1/1] Add Static route to logical router

Guru Shetty guru at ovn.org
Thu Apr 7 18:04:52 UTC 2016


On 7 April 2016 at 01:43, Mickey Spiegel <emspiege at us.ibm.com> wrote:

> See comments inline
>
> Mickey
>
>
> -----Guru Shetty <guru at ovn.org> wrote: -----
> >To: Mickey Spiegel/San Jose/IBM at IBMUS
> >From: Guru Shetty <guru at ovn.org>
> >Date: 04/06/2016 05:58PM
> >Cc: ovs dev <dev at openvswitch.org>, Shi Xin Ruan <Steve.ruan at cn.ibm.com>
> >Subject: Re: [ovs-dev] [PATCH 1/1] Add Static route to logical router
> >
> >
> >
> >On 6 April 2016 at 16:55, Mickey Spiegel <emspiege at us.ibm.com> wrote:
> >>Steve and Guru,
> >>
> >> I am not all that concerned about the "valid" column, but I do think
> that we will need a different additional column in the near future for
> output port.
> >>
> >> There are three different motivations for allowing output port to be
> specified in the static route:
> >> 1) In order to support static routes with a link local next hop. If a
> link local next hop is used, it is possible that the same link local
> address appears on different router ports with different meanings. By
> specifying the port, this disambiguates the specific link local next hop
> that was desired.
> >> Note: Neutron does not yet support static routes with link local next
> hop. We need to drive the feature in Neutron as well, optionally allowing a
> router interface to be specified in addition to the next hop.
> >> 2) This feature should not really be specific to static routes, it
> should also apply to dynamic routes when we add that in the future.
> Basically anything that looks up an IP address prefix and returns a next
> hop and optionally an output port. There are cases where explicitly
> specifying the output port makes sense.
> > For point 1 and 2, I am not sure whether we should do anything till
> there is code in ovn-northd that actually uses it.
>
> [Mickey] Point of clarification, the proposal is to add an output port
> column to the static route table in northd. The question is not whether
> there is code in ovn-northd that uses it, it is whether there is code at
> the CMS layer that fills this column. Both the features in points 1 and 2
> would make use of this column.
>
I see what you mean now.


> Even if we don't add this column now, if you don't have a separate static
> route table, it will make such an addition difficult in the future.
>
> >> 3) In order to optimize processing of the routing recursion (Steve's
> code loops over the router's ports in ovn-northd.c to carry out this
> routing recursion), we might want to do it above OVN in an event triggered
> manner, rather than every time ovn-northd.c recalculates the flows that it
> places into the southbound database.
> > I don't think I understand the above point. The static_route I have in
> mind need not recursively look through routers. All they need is to see
> whether the router peer has the next hop IP address and the packet is just
> sent to that router. From there on it is a fresh start.
>
> [Mickey] By routing recursion I just meant a small walk through all of the
> router ports to find which router port has the next hop address.
>
We are on the same page then (for the above point.)

So to summarize, a new table will help if we add the outport as a column
and keep it optional. If it is filled, use it. Else, figure out the next
hop.



More information about the dev mailing list