[ovs-dev] [PATCH] vswitch: allow to specify ofport when creating port

Ben Pfaff blp at nicira.com
Mon Oct 1 17:08:41 UTC 2012

On Mon, Oct 01, 2012 at 05:35:19PM +0900, Isaku Yamahata wrote:
> For stable bridge configuration, sometimes it is desirable to be able to
> add-port with port number specified.
> This patch implements it and it can be done by setting ofport column of Interface
> table like
>   ovs-vsctl add-port s1 eth2 -- set Interface eth2 ofport=10
> Signed-off-by: Isaku Yamahata <yamahata at valinux.co.jp>

Usually we don't ovs-vswitchd both read and write a single column,
because it can cause confusion.  In this case, for example,
controllers can currently use the ofport column to figure out when a
newly added port has been assigned an OpenFlow port number.  This
commit would make that information harder to interpret (although the
information can still be obtained other ways).

In other cases where there is a need for ovs-vswitchd both to inform
the controller of a value and to take requests for that value, we
generally use two separate columns (or key-value pairs).  For example,
for OpenFlow datapath ID, the datapath_id column in the Bridge table
reports the in-use datapath ID, and the other-config:datapath-id value
requests a particular datapath ID.  I'd suggest using a similar
approach here.

But there's another issue too.  As part of the ongoing effort to
upstream tunneling to the Linux kernel, Justin is currently reworking
how ports are assigned to datapaths.  That work is going to change a
lot of the code in this area, and we've considered adding the ability
to request OpenFlow port numbers as part of it.  So, if requesting
particular port numbers is important to you, I'd suggest coordinating
with Justin.

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