[ovs-discuss] Fwd: How to modify the in_port field inside a flow in OF13 ?
nilesh.gavaskar at gmail.com
Wed Mar 11 19:07:36 UTC 2015
That fixed my problem. Thanks !
Sorry for the repost. I should have read the FAQs first.
By a flow parameter, I meant something like mod_dl_src or mod_dl_dst. I
couldn't find a similar action parameter that I could use.
I tried using the resubmit() action but I was going around in circles.
I had also looked at the OFPACT_SET_FIELD inside ofp-actions.c but I
couldn't figure out how to use it.
Here is what I used to change the input port num: ( '0' is the new port
ovs-ofctl add-flow br0 in_port=2,actions=load:0->NXM_OF_IN_PORT,controller
On Wed, Mar 11, 2015 at 2:33 PM, Ben Pfaff <blp at nicira.com> wrote:
> On Wed, Mar 11, 2015 at 02:23:59PM -0400, Nilesh G wrote:
> > Does anyone know of a way to modify the input port field (in_port) for a
> > packet via a flow parameter in OF 1.3 ?
> What's a flow parameter?
> The FAQ has a possibly relevant Q&A:
> ### Q: I added a flow to send packets out the ingress port, like this:
> ovs-ofctl add-flow br0 in_port=2,actions=2
> but OVS drops the packets instead.
> A: Yes, OpenFlow requires a switch to ignore attempts to send a packet
> out its ingress port. The rationale is that dropping these packets
> makes it harder to loop the network. Sometimes this behavior can
> even be convenient, e.g. it is often the desired behavior in a flow
> that forwards a packet to several ports ("floods" the packet).
> Sometimes one really needs to send a packet out its ingress port
> ("hairpin"). In this case, output to OFPP_IN_PORT, which in
> ovs-ofctl syntax is expressed as just "in_port", e.g.:
> ovs-ofctl add-flow br0 in_port=2,actions=in_port
> This also works in some circumstances where the flow doesn't match
> on the input port. For example, if you know that your switch has
> five ports numbered 2 through 6, then the following will send every
> received packet out every port, even its ingress port:
> ovs-ofctl add-flow br0 actions=2,3,4,5,6,in_port
> or, equivalently:
> ovs-ofctl add-flow br0 actions=all,in_port
> Sometimes, in complicated flow tables with multiple levels of
> "resubmit" actions, a flow needs to output to a particular port
> that may or may not be the ingress port. It's difficult to take
> advantage of OFPP_IN_PORT in this situation. To help, Open vSwitch
> provides, as an OpenFlow extension, the ability to modify the
> in_port field. Whatever value is currently in the in_port field is
> the port to which outputs will be dropped, as well as the
> destination for OFPP_IN_PORT. This means that the following will
> reliably output to port 2 or to ports 2 through 6, respectively:
> ovs-ofctl add-flow br0 in_port=2,actions=load:0->NXM_OF_IN_PORT,2
> ovs-ofctl add-flow br0 actions=load:0->NXM_OF_IN_PORT,2,3,4,5,6
> If the input port is important, then one may save and restore it on
> the stack:
> ovs-ofctl add-flow br0 actions=push:NXM_OF_IN_PORT,\
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