[ovs-dev] Adding NoviFlow experimenters to OVS.

Ben Pfaff blp at ovn.org
Fri Oct 6 05:56:19 UTC 2017


The build-aux changes are just to add support for recognizing the OXM
experimenter extension.  You still need to actually implement the
fields.

On Wed, Oct 04, 2017 at 05:54:52PM -0400, yann bourdeau wrote:
> 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.
> 
> Thanks,
> 
> Yann
> 
> > 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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