Hi Ben, Firstly thank you for the swift response, In order to get a better understanding of what I was doing (I’ve starting working with openvswitch a week ago) I tried defining an action called OFPAT_RAW_BUFFER (that did absolutely nothing) just like the FAQ says and my mininet topology did in fact recognize it as a valid action. Now I was starting the actual implementation of the action and that’s where my problems arise, I know how I’m going to program it I just don’t know where I’m meant to implement it and it’s somewhat frustrating.
Based on what you said : “You'll need to make the action send packets that need to be buffered to userspace, with a "userspace" kernel action” How exactly is this done? I believe the kernel receives the packet, and the datapath folder contains the code where the packet is recvd and processed, how exactly is it then sent to userspace, I’m having a tough time understanding how packets work in ovs. Diving in the code I found the ovs_dp_process_packet should be what I’m looking for, but I’m not quite sure. I guess a more accurate question for my case would be, where does someone who is new to ovs start from in order to understand the ovs codebase and learn how to implement a new action such as this one? Thanks again! L From: Ben Pfaff<mailto:[email protected]> Sent: Friday, April 24, 2020 18:50 To: Luca Mancini<mailto:[email protected]> Cc: [email protected]<mailto:[email protected]> Subject: Re: [ovs-discuss] OVS custom action On Fri, Apr 24, 2020 at 02:50:43PM +0000, Luca Mancini wrote: > I am trying to implement a new openflow action on an openvswitch, that upon > request by the controller buffers a given packet. > > So assume a topology like H1—s1--s2—H2 where h1 sends packets to h2, the > controller would specify a BUFFER action to all packets going from h1 to h2 > Making the s1 switch create a buffer where all these packets are stored until > the buffer is full and then send the buffer (as a new packet) down the path > to H2. > I have found very little material regarding the implementation of a new > openflow action to ovs: > > I followed this guide a little bit but I’m finding some things a bit > confusing https://mcfelix.me/blog/modifying-ovs/ > Some questions I have are: > -is this type of action possible? > -where exactly do I need to code the actual action function? > -how and where are packets defined in OVS? I’m having trouble understading if > the packet I need to be storing is the sk_buff that is passed as a parameter > or if it’s something else This should be possible. You'll need to make the action send packets that need to be buffered to userspace, with a "userspace" kernel action. Then you can accumulate the packets in userspace until they should be released. Since you'll only be dealing with userspace packets, struct dp_packet is primarily what you need to care about. The FAQ says this: Q: How do I add support for a new OpenFlow action? A: Add your new action to ``enum ofp_raw_action_type`` in ``lib/ofp-actions.c``, following the existing pattern. Then recompile and fix all of the new warnings, implementing new functionality for the new action as needed. (If you configure with ``--enable-Werror``, as described in the :doc:`/intro/install/general`, then it is impossible to miss any warnings.) If you need to add an OpenFlow vendor extension action for a vendor that doesn't yet have any extension actions, then you will also need to add the vendor to ``vendor_map`` in ``build-aux/extract-ofp-actions``. Also, you will need to add support for the vendor to ``ofpact_decode_raw()`` and ``ofpact_put_raw()`` in ``lib/ofp-actions.c``. (If you have a choice of how to design your vendor extension actions, it will be easier if you make them resemble the ONF and OVS extension actions.)
_______________________________________________ discuss mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
