[ovs-dev] Adding NoviFlow experimenters to OVS.

yann bourdeau yann.bourdeau at noviflow.com
Wed Oct 4 21:54:52 UTC 2017

Hi Ben,

	I have looked at the python code to do it in build-aux. However what I want to add is an OXM that match on UDP payload not on an existing field. From what I understand I can’t do it from all the source in build-aux or am I mistaken?

	Here is the documentation:

Finally flow entries using the match field defined above can be loaded in the switch using the
OFPT_FLOW_MOD message including the following ofp_match as one of the fields to match
struct ofp_match {
uint16_t type; /* ofp_match_type OFPMT_OXM 0x0001 */
uint16_t length; /* Length of ofp_match (excluding padding) */
uint8_t oxm_fields[0]; /* 0 or more OXM match fields */
uint8_t pad[]; /* Exactly ((length + 7)/8*8 – length)
(between 0 and 7) bytes of all-zero bytes */
where one of the oxm_fields is
struct oxm_fields {
uint16_t oxm_class; /* Match class OFPXMC_EXPERIMENTER 0xffff */
uint oxm_field:7; /* Match field within the class NOVI_OXM_UDP_PAYLOAD 0b0000001 */
uint oxm_hasmask:1; /* Set if OXM includes a bitmask in payload (wildcard match tables only) */
uint8_t oxm_length; /* Length of OXM payload */
uint32_t experimenter; /* NoviFlow experimenter ID 0xff000002 */
uint8_t payload[1-32] /* 1-32 payload bytes to be matched on*/
uint8_t mask [0-32] /* Optional mask present if oxm_hasmask bit is set in the header */

The offset is set by the following experimenter message:

struct ofp_experimenter_msg {
uint32_t experimenter; /* NoviFlow experimenter ID 0xff000002 */
uint8_t customer; /* Customer ID 0xff */
uint8_t reserved; /* Reserved for future use 0x00 */
uint16_t novi_msg_type; /* NoviFlow message type NOVI_MSG_UDP_PAYLOAD 0x0000 */
uint8_t table_id; /* Table number */
uint8_t payload_size; /* Number of bytes N to be match on (1-32) */
uint16_t payload_offset; /* Starting position X in the UDP payload (0-maxudpmatch)
where maxudpmatch=14 for the NoviSwitch 1000 Series,
44 for the NoviSwitch 21100 and
48 for the other NoviSwitch 2000 Series */

I suppose I will need to modify some C code to do it. I have spent some time at looking at the C code this afternoon. I’m starting to get how it works but I’m not there yet.



> Le 4 oct. 2017 à 14:07, Ben Pfaff <blp at ovn.org> a écrit :
> For fields, you should just have to add an entry to OXM_CLASSES in
> build-aux/extract-ofp-fields.  For actions, vendor_map in
> build-aux/extract-ofp-actions.
> On Wed, Oct 04, 2017 at 12:45:46PM -0400, yann bourdeau wrote:
>> Hi Ben,
>> 	Thanks for the commit revision. It will help. However, do you have the same for match field and action? Otherwise I will just dig in and try to understand.
>> Thanks,
>> Yann
>>> Le 4 oct. 2017 à 12:32, Ben Pfaff <blp at ovn.org> a écrit :
>>> On Wed, Oct 04, 2017 at 12:13:03PM -0400, yann bourdeau wrote:
>>>> Hi all,
>>>> 	I was wondering if there was a good tutorial on how to add experimenters message, match fields and actions to OVS. I have found a little bit of info at the end of the page there: https://github.com/openvswitch/ovs/blob/7169d4fdc8e564331c7a5ad910bc1d99cb413712/FAQ.rst#development <https://github.com/openvswitch/ovs/blob/7169d4fdc8e564331c7a5ad910bc1d99cb413712/FAQ.rst#development>. It is quite brief.
>>>> 	I have used OVS in the past but never developed for it.
>>> Adding a new kind of experimenter message shouldn't be much work.  You
>>> can look at commit 9021969654dda "extract-ofp-msg: Add ONF extension
>>> support" for an example.

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