ofproto: Add onf13_flow_monitor_request

This is in preparation for supporting EXT-187: flow entry notification
extension (ONF flow monitor).

Signed-off-by: Simon Horman <horms@verge.net.au>

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v2
* First post
ofp-util: ofputil_flow_monitor_request abstracts onf13_flow_monitor_request

Update documentation of ofputil_flow_monitor_request to note
that it abstracts onf13_flow_monitor_request as well
as {nx,ofp14}_flow_monitor_request.

This is in preparation for supporting EXT-187: flow entry notification
extension (ONF flow monitor).

Signed-off-by: Simon Horman <horms@verge.net.au>

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v2
* First post
ofp-util: Support decoding of EXT-187 requests

Support decoding of EXT-187: flow entry notification extension
(ONF flow monitor) requests.

Signed-off-by: Simon Horman <horms@verge.net.au>

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v2
* First post
ofp-print: Test EXT-187 requests

Test printing of EXT-187: flow entry notification
(ONF flow monitors) requests.

Signed-off-by: Simon Horman <horms@verge.net.au>

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v2
* First post
ofp-util: Support encoding of EXT-187 requests

Support encoding of EXT-187: flow entry notification extension
(ONF flow monitor) requests.

Signed-off-by: Simon Horman <horms@verge.net.au>

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v2
* First post
ofp-util: Support decoding of EXT-187 replies

Support decoding of EXT-187: flow entry notification extension
(ONF flow monitor) replies.

This re-uses existing Nicira extension code as other than the header
the wire format is the same.

Signed-off-by: Simon Horman <horms@verge.net.au>

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v2
* First post
ofp-print: Test of EXT-187 replies

Test printing of EXT-187: flow entry notification extension
(ONF flow monitor) replies.

Signed-off-by: Simon Horman <horms@verge.net.au>

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v2
* First post
ofp-util: Support encoding of EXT-187 replies

Support encoding of EXT-187: flow entry notification extension
(ONF flow monitor) replies.

This re-uses existing Nicira extension code as other than the header
the wire format is the same.

Signed-off-by: Simon Horman <horms@verge.net.au>

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v2
* First post
ofproto: EXT-187 tests

Signed-off-by: Simon Horman <horms@verge.net.au>

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v2
* First post
openflow: EXT-187 is now supported

EXT-187: flow entry notification extension (ONF flow monitor) is
now supported for OpenFlow1.3.

OpenFlow1.4 flow monitor is also now supported.

Signed-off-by: Simon Horman <horms@verge.net.au>

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v2
* First post